A heavyweight black hole in the heart of a distant galaxy has the mass of 140 million suns, according to new measurements. A vivid video by the National Radio Astronomy Observatory describes how researchers “weighed” the black hole at the center of the barred spiral galaxy NGC 1097.
Many galaxies have huge black holes in their centers, and these objects affect the galaxies’ growth and evolution. The galaxy NGC 1097 is 47 million light-years away from Earth, too far to determine the mass of its central black hole by the movement of the stars around it. But by tracking the movements of two types of molecular gases around the galaxy’s center, researchers using the Atacama Large Millimeter/submillimeter Array in Chile (ALMA) were able to work backward and figure out the black hole’s gravitational pull.
The ALMA telescopes tracked the radiation emitted from the two gases, hydrogen cyanide and formyl cation, as they swirled around the galaxy. The gases don’t interact strongly with environmental conditions within the galaxy, such as ionized gas flowing inward or outward. This means the gases paint an accurate picture of the effects of gravity’s pull alone. With just two hours of observational data, the researchers learned enough about the distribution and velocities of those gases to fit them to a model and calculate the pull of the galaxy’s core black hole.
The mass of a central black hole affects the physical properties of its host galaxy, and recent work has shown that those effects are different for different types of galaxies, study lead author, Kyoko Onishi, a doctoral student at the SOKENDAI (The Graduate University for Advanced Studies) in Japan, said in a statement. To understand those effects, Onishi said it’s important to measure the mass of these central black holes in various galaxy types.
Because of the quick precision measurements, “ALMA will enable us to observe a large number of galaxies in a practical length of time,” added Onishi, who is doing her research at the National Astronomical Observatory of Japan (NAOJ).
A Mars-size planet about 200 light-years from our solar system has turned out to be the lightest known alien world orbiting a normal star, researchers say.
Astronomers made the discovery after measuring the size and mass of the baking-hot planet, named Kepler-138 b, which orbits a red dwarf star called Kepler-138. Mars is only 53 percent the size of the Earth (or just about half the size), so Kepler-138 b is smaller than the Earth.
In the past couple of decades, astronomers have confirmed the existence ofmore than 1,800 exoplanets, or planets orbiting a star other than our sun. However, it’s more difficult for scientists to calculate the masses of small, rocky planets like Mars or Mercury than for large, gaseous worlds such as Jupiter or Saturn. Scientists measure the masses of exoplanets by looking at how strongly their gravitational fields tug on their stars; small planets have small masses, and their weak tugs on their stars are more difficult for astronomers to detect. As such, few Earth-size exoplanets have had their masses measured. [The Smallest Known Alien Planets in Pictures]
In this new study, astronomers investigated Kepler-138, a cold, dim red dwarf star with a mass about half that of the sun. Kepler-138 is located about 200 light-years from Earth, in the constellation Lyra.
Kepler-138 “is more than 10 million times further away from us than our sun,” study lead author Daniel Jontof-Hutter, an astronomer at Pennsylvania State University in University Park, told Space.com.
The star Kepler-138 is home to three exoplanets, prior research has confirmed by detecting the slight dimming of the star’s light that occurs whenever one of these worlds crosses in front of it. Each of these two planets — Kepler-138 c and Kepler-138 d — is about 1.2 times as wide as Earth. The third, Kepler-138 b, is a little more than half as wide as Earth, making it about the size of Mars.
“Kepler-138 b has the same apparent size to us as a golf ball 10 million kilometers [6.2 million miles] away,” Jontof-Hutter said.
These three exoplanets orbit very close to their star. Kepler-138 b takes a little more than 10 days to complete its orbit, Kepler-138 c requires nearly 14 days and Kepler-138 d needs about 23 days.
Using NASA’s Kepler spacecraft, the researchers looked at how the gravitational tug-of-war among these exoplanets influenced the lengths of their orbits. Because the strength of a planet’s gravitational pull is directly related to its mass, the scientists were able to weigh all three of these planets.
The astronomers found that the mass of the Mars-size inner planet, Kepler-138 b, is about one-fifteenth, or 6.7 percent, of Earth’s, making it about two-thirds the mass of Mars.
“Kepler-138 b is the first exoplanet smaller than Earth to have both its size and its mass measured,” Jontof-Hutter said.
The least massive known alien world may be the exoplanet PSR B1257+12 b, which has an estimated mass only about one-fiftieth, or 2 percent, that of Earth. However, that world does not orbit a normal star, but instead circles a pulsar — a dense, rapidly spinning remnant of a supernova explosion.
Knowing the mass and width of Kepler-138 b helped the researchers calculate its density, which they found is about two-thirds that of Mars, suggesting it has a purely rocky composition.
Although Kepler-138 b may be similar in mass and width to Mars, it is so much closer to its star, and thus hotter, meaning it is likely very different from Mars, Jontof-Hutter said. “In fact, all three planets orbiting Kepler-138 are likely too hot to retain liquid water,” Jontof-Hutter said. On the outermost planet, surface temperatures are about 250 degrees Fahrenheit (120 degrees Celsius), while those on the innermost planet are about 610 degrees F (320 degrees C).
Kepler-138 c and Kepler-138 d have masses 197 percent and 64 percent of Earth’s, respectively.
This finding opens up the study of rocky alien planets smaller than Earth, Jontof-Hutter said.
“The enormous variety of exoplanets that have been discovered by Kepler show us that systems like our own solar system are probably not the norm, and we don’t know why,” Jontof-Hutter said. Analyzing more exoplanets “will give us clues about how planets form and enable us to learn how common systems like are own really are.”
The scientists detailed their findings in the June 18 issue of the journal Nature.
Methane, a potential sign of primitive life, has been found in meteorites from Mars, adding weight to the idea that life could live off methane on the Red Planet, researchers say.
This discovery is not evidence that life exists, or has ever existed, on Mars, the researchers cautioned. Still, methane “is an ingredient that could potentially support microbial activity in the Red Planet,” study lead author Nigel Blamey, a geochemist at Brock University in St. Catharines, Ontario, Canada, told Space.com.
Methane is the simplest organic molecule. This colorless, odorless, flammable gas was first discovered in the Martian atmosphere by the European Space Agency’s Mars Express spacecraft in 2003, and NASA’s Curiosity rover discovered a fleeting spike of methane at its landing site last year.
Much of the methane in Earth’s atmosphere is produced by life, such as cattle digesting food. However, there are ways to produce methane without life, such as volcanic activity.
To shed light on the nature of the methane on Mars, Blamey and his colleagues analyzed rocks blasted off Mars by cosmic impacts that subsequently crash-landed on Earth as meteorites. About 220 pounds (100 kilograms) of Martian meteorites have been found on Earth.
The scientists focused on six meteorites from Mars that serve as examples of volcanic rocks there, collecting samples about one-quarter of a gram from each — a little bigger than a 1-carat diamond. All the samples were taken from the interiors of the meteorites, to avoid terrestrial contamination.
The researchers found that all six released methane and other gases when crushed, probably from small pockets inside.
“The biggest surprise was how large the methane signals were,” Blamey said.
Chemical reactions between volcanic rocks on Mars and the Martian environment could release methane. Although the dry thin air of Mars makes its surface hostile to life, the researchers suggest the Red Planet is probably more habitable under its surface. They noted that if methane is available underground on Mars, microbes could live off it, just as some bacteria do in extreme environments on Earth.
“We have not found life, but we have found methane that could potentially support microbes in the subsurface,” Blamey said.
Blamey now hopes to analyze more Martian meteorites. He and his colleagues detailed their findings online today (June 16) in the journal Nature Communications.
As NASA’s New Horizons spacecraft glides its way to the cold outer reaches of our solar system to take the first-ever up-close look at Pluto, the time is right to revise the International Astronomical Union (IAU)’s 2006 definition of a planet, which resulted in Pluto’s “demotion” from planet to ambiguous dwarf-planet status.
For those unfamiliar with the issues that led to that highly controversial decision, here’s a quick recap: It started with Pluto itself, discovered on Feb. 18, 1930, by Clyde Tombaugh, a young American astronomer working at Lowell Observatory in Flagstaff, Arizona. Pluto turned out to be rather unlike the other eight large objects orbiting the sun. Pluto is much smaller than Mercury, and only two-thirds the size of Earth’s moon. Its orbit is tilted and eccentric, crossing Neptune’s. No other planet acted like this. In 2000, astronomers found other objects orbiting the sun in the deep outer solar system, with qualities very much like Pluto’s. They were given names like Sedna , Quaoar, Ixion, Varuna, Makemake and Haumea . Many were close (but not quite equal) to Pluto in size. All of them had tilted, eccentric orbits; quite a few of those orbits crossed Neptune’s.
The tipping point came in 2005. California Institute of Technology astronomer Mike Brown, along with Chad Trujillo of Gemini Observatory and David Rabinowitz of Yale University, discovered a new massive body in the solar system. This new body, which astronomers latter dubbed Eris, was particularly noteworthy: Not only did it possess a moon, but at the time, it was estimated to be larger than Pluto. Subsequent observations revealed that Eris and Pluto are nearly identical in size, though Pluto is likely a few kilometers larger. Initially, Brown had named the newly discovered body Xena (after the protagonist of the eponymous TV show, with a sneaky Planet X reference). Although the name Xena didn’t stick, the IAU later officially — and aptly — christened it Eris after the Greek goddess of chaos and discord.
So, it seemed quite clear that if Pluto was our solar system’s ninth planet, then Eris should be its 10th. And if Eris and Pluto were planets, why shouldn’t Makemake and Haumea be considered planets as well? And what if there were even bigger objects out there to be discovered? Why shouldn’t the solar system have 15 planets, or 40? (Can you imagine the mnemonic device that would be required to remember 40 planets in the solar system?!)
For all who were in support of granting planet status to these objects, an equally adamant camp insisted that none of these objects, including Pluto, deserved to be called planets, and that our solar system contained only eight objects worthy of planet status. Neptune would be the last and final.
A worsening problem
With the intention of solving the debate once and for all, members of the IAU met in 2006. They spent days debating how to establish unambiguous definitions for the objects in our solar system. In the end, Resolution 5A was born:
The IAU therefore resolves that planets and other bodies in our solar system, except satellites, be defined into three distinct categories in the following way:
(1) A planet is a celestial body that (a) is in orbit around the sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighborhood around its orbit.
(2) A dwarf planet is a celestial body that (a) is in orbit around the sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape , (c) has not cleared the neighborhood around its orbit, and (d) is not a satellite.
(3) All other objects, except satellites, orbiting the sun shall be referred to collectively as small solar-system bodies.
These are, to put it bluntly, terrible definitions. Despite its goal of providing unambiguous definitions, Resolution 5A actually contains the kind of ambiguity that most scientific organizations would protest. It adds confusion, resolves little and makes nobody happy.
So how did that become the official definition of a planet? A very strange vote. If you think low voter turnout is limited to politics, consider this: Only about 4 percent of IAU members were present for the vote on Resolution 5A. But it was travel schedules, not apathy, that caused this abysmal turnout. You see, the vote took place on the last day of the IAU meeting, when many people had to leave to catch flights back home — 424 astronomers were present, even though IAU membership in 2006 was just more than 10,000. As a result, Pluto lost the status it had enjoyed for more than 80 years and became a dwarf planet overnight. [Pluto Demoted: No Longer a Planet in Highly Controversial Definition]
The term “dwarf planet” itself causes confusion. You often hear people say Pluto is still a planet but that it just happens to be a dwarf planet now. But despite the name, the IAU does not consider a dwarf planet a planet — unlike a dwarf star, which is still a star, or a dwarf galaxy, which is still a galaxy. So much for eliminating ambiguity! But just the conflicting use of the word planet isn’t the most unclear part of the resolution.
Credit: Made with the Pluto Safari app for iOS and Android.
Picking apart Resolution 5A
Let’s dissect resolution 5A “Definition of ‘planet’”, one of six IAU Resolutions that were passed at the Closing Ceremony of the General Assembly in 2006.
*Nearly round shape. There is an element of something good here. We all intuitively feel that a planet should be round, or nearly so. But what is “nearly”? How lumpy and bumpy must an object be to no longer qualify as a planet or a dwarf planet? How smooth must the “ball” be? The Earth, which we all agree is a planet, is nearly round on some scales, but on others, it’s not. If you’re standing in the bottom of the Grand Canyon, the Earth isn’t even close to nearly round.
*Cleared the neighborhood. I’ve tried to wrap my head around this phrase for years, tried to convince myself that it makes sense — but I just can’t swallow it. The IAU is trying to express that, in addition to being round, a planet should be the dominant gravitational force in its local region of the solar system. That’s not an unreasonable position. Certainly the Earth and Jupiter are the dominant objects in their local regions. Neptune surely is, too. Even though Pluto’s orbit crosses Neptune’s, Neptune forces Pluto into something called a 3:2 resonance (for every three times Neptune goes around the sun, Pluto goes around twice), preventing collision. But have any of these planets actually “cleared the neighborhood” around their orbits? No. Pluto is still clearly in Neptune’s “neighborhood.” For that matter, Jupiter has two well-known groups of asteroids, the Trojans, which lead and follow Jupiter along in its orbit. For that matter, the Earth hasn’t quite “cleared the neighborhood” around its orbit, either, to which anyone who saw the near-Earth asteroids that entered Earth’s atmosphere near Chelyabinsk, Russia, on Feb. 15, 2013, or Tunguska, Siberia, on June 30, 1908, can attest. So are Earth, Jupiter and Neptune the dominant gravitational objects in their local neighborhoods? Yes, clearly. Have they cleared their neighborhoods? No. Not by a long shot.
Other scientists have weighed in on the matter. Alan Stern, principal investigator for the New Horizons mission to Pluto, made it clear he disagrees with the IAU resolution. “Any definition that allows a planet in one location but not another is unworkable. Take Earth. Move it to Pluto’s orbit, and it will be instantly disqualified as a planet,” Stern said.
The biggest problem with the IAU’s planet definition is that it replaces an already-ambiguous concept (“What is a planet?”) with three more ambiguous concepts, (“nearly round,” “cleared” and “neighborhood”). Indeed, the only definitive part of the IAU resolution on which everyone can agree is the first part: (1) A planet is in orbit around the sun. It’s why the moon is not a planet. My 6-year-old niece intuitively understands this. It’s the only part of the IAU definition I would keep.
The way out
Let’s look at some other kinds of definitions that are clear and unambiguous.
*International boundaries. It’s well understood that the portion of North America north of 49 degrees, between the Canadian provinces of British Columbia, Alberta, Saskatchewan and Manitoba, and the U.S. states of Washington, Idaho, Montana, North Dakota and Minnesota, is called Canada, and the portion below that latitude is called the United States. There’s no physical demarcation — no river, no mountain range — along the 49th parallel. There’s no subtle change in vegetation or geological structure. But there is a hard, sharp, clearly defined, well-understood boundary that unambiguously answers the question, “What is Canada?” It’s the country north of the 49th parallel. It passes the 6-year-old-niece test.
*Constellation boundaries. Back in 1888, the IAU defined an intricate set of boundary lines in the sky, precisely outlining the groups of stars that were commonly referred to as constellations. It also declared that there would be 88 of these constellations. Lines were chosen carefully, to respect traditional choices about which star might lie in which constellation, and in the end, the definitions were clear. There is no ambiguity about which particular point in the sky falls within which constellation. And, you can tell precisely when a moving celestial object (like Pluto) might cross from one constellation to another. It’s an arbitrarily agreed upon but well-defined system of definitions that has served the astronomical community well for more than 100 years.
*The Karman line that defines the edge of space. Where does the Earth’s atmosphere end and outer space begin? Clearly, there is no physical boundary. There is no bubble holding the atmosphere that one must pierce on one’s way to the International Space Station. The air just gets thinner and thinner until you can ignore it. But in reality, air molecules continue to exist, albeit in smaller numbers, out to an altitude of many thousands of kilometers and beyond — indeed, some of these air molecules may have made it as far as Pluto by now! However, since the early days of manned spaceflight, a near-universally accepted definition is that space begins at an altitude of 100 kilometers (62 miles). In fact, this definition is accepted by the Fédération Aéronautique Internationale (FAI), an international standard-setting body for aeronautics and astronautics. Pilots who’ve flown higher than 100 km have officially earned the title of astronaut. It’s another arbitrary, but widely accepted convention that is clear, unambiguous and easily passes the 6-year-old comprehension test.
What the IAU should have done in 2006, and could easily do moving forward, is to crystallize the definition of the word “planet” as unambiguously as it defined the boundaries of the constellations in 1888. Yes, that definition would have been arbitrary, and yes, the actual physical objects themselves would gradually transition from larger to smaller, and don’t care in the least what we choose to call them. But the IAU could have chosen a definition that resolves the debate in a far more satisfying manner than it actually did.
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The 1,000-km rule
So, what would be a better definition for the objects in the solar system?
(1) A “planet”  is a celestial body that (a) is in orbit around the sun, and (b) has a maximum surface radius greater than 1,000 km (620 miles).
(2) All other objects, except satellites, orbiting the sun shall be referred to collectively as small solar-system bodies.
“But that’s completely unscientific,” you may say. “Why 1,000 km? Why not 1,200, or 750?”
I submit that the precise definition of a planet as an object with a radius of at least 1,000 km is no less scientific than the definition of a kilometer as being a unit of distance equal to 1,000 m, or a degree being 1/360 of a circle.
And there are other reasons why the 1,000-km definition is more scientific than it might seem at first. But let’s put that aside momentarily. Instead, let’s see what would have happened if the IAU had adopted this definition.
Here is a list of the largest known objects orbiting the sun, and their radii in kilometers:
Object Radii (km)
Jupiter: 69,911 km (43,441 miles)
Saturn: 58,232 km (36,184 miles)
Uranus: 25,362 (15,759 miles)
Neptune: 24,622 (15,299 miles)
Earth: 6,378 (3,963 miles)
Venus: 6,052 (3,761 miles)
Mars: 3,390 (2,106 miles)
Mercury: 2,440 (1,516 miles)
Pluto: 1,184 (736 miles)
Eris: 1,163 (723 miles)
Makemake: 715 (444 miles)
Haumea: 620 (385 miles)
Quaoar: 555 (345 miles)
Sedna: 498 (309 miles)
Ceres: 475 (295 miles)
Orcus: 458 (285 miles)
By the 1,000-km definition, all eight classical planets would remain planets. So would Pluto. And we’d add Eris. The solar system would have exactly 10 planets, a number that is deeply satisfying to two-handed, five-fingered humans who’ve been practicing base-10 mathematics for thousands of years. The “Plutophile” camp, fond of keeping Pluto’s planetary status for historical reasons, would retain its dignity. And elevating Eris to a first-class planet would be an honorable nod to the cutting-edge astronomers whose work led to a need for this new definition in the first place.
And finally, the 1,000-km rule, like any good arbitrary rule, actually does a pretty good job of respecting the underlying physical phenomena that it purports to define. Planets are made of physical materials like rock, metal, gas and ice. They may come in different proportions, but those materials all respect the same physical laws. When you put together a lump of rock, metal or ice, in any proportion, certain things start to happen as that lump approaches 1,000 km in radius. The materials will pull together under the force of their own gravity. Solid rock will start to deform. Ice, even frozen hard as granite at the edge of the solar system, will slowly flow. There is no known substance that can resist the force of its own gravity when made into a lump with a 1,000-km radius. Any object, made of any substance, of approximately that size, will eventually flow under action of its own gravity into a shape that is “nearly round” when viewed from far away. The 1,000-km radius just happens to describe something that naturally takes place for objects of a certain size and results in what we all intuitively want a planet to look like.
And for space enthusiasts, there’s one more benefit to my proposed definition. While we’re all looking forward to the New Horizons Pluto flyby, there’s also a certain sadness to knowing that, after Pluto, there will be no more planets in our solar system to explore. If our solar system has 10 planets, that’s no longer true. As far away and difficult as it was to reach Pluto, it will be even more difficult to reach Eris. It’s another frontier, another first and another project to fund. That prospect alone should give the scientific community a reason to rethink and resolve Resolution 5A.
Mars is a large enough planet that astrobiologists looking for life need to narrow the parameters of the search to those environments most conducive to habitability.
NASA’s Mars Curiosity mission is exploring such a spot right now at its landing site around Gale Crater, where the rover has found extensive evidence of past water and is gathering information on methane in the atmosphere, a possible signature of microbial activity.
But where would life most likely gain energy from its surroundings? One possibility is in an environment that includes “green rust,” a partially oxidized iron mineral. A fully oxidized iron “rust” — one exposed to oxidation for long enough — turns orangey-red, similar to the color of Mars’ regolith. When oxidization is incomplete, however, the iron rust is greenish.
This means that there are two different “redox states,” or types of iron with different numbers of electrons in the same mineral. This difference between the two iron redox states could allow the mineral to take in or give up electrons and thus act as a catalyst, said Laurie Barge, a planetary scientist at NASA’s Jet Propulsion Laboratory. She studies hydrothermal vents, an area where chemical contrasts also fuel life.
“From an environmental science perspective, green rust can absorb and concentrate nutrients, and can also accept and donate electrons for life,” said Barge.
She is the lead author of related work that was presented at the American Geophysical Union’s Joint Assembly meeting in May 2015. Funding for this work comes from the Jet Propulsion Laboratory’s Icy Worlds team as part of the NASA Astrobiology Institute (NAI) element of the Astrobiology Program at NASA.
One major challenge in the search for life on Mars is that its surface is highly oxidized. On Earth, green rust generated in Barge’s lab oxidizes quickly when exposed to air, and its composition is changed in only an hour. However, the lack of oxygen on Mars makes this a slower process. It is likely that green rust occurs beneath the oxidized surface, perhaps only a centimeter or half-inch deep as revealed by Curiosity.
There are more probes on the way to Mars that will include drills. One of those will be NASA’s InSight lander, which is set to go to the Red Planet in 2016. Another is the European Space Agency’s ExoMars rover, expected to launch in 2018.
A major focus of current NASA missions on Mars is finding out where water has flowed in the past. NASA’s Curiosity, Opportunity and Spirit rovers have all found rocks that form in the presence of water, such as the red iron oxide mineral hematite, as well as select sulfates and clays. Further, several orbiting spacecraft have seen signs, such as the presence of gullies, in which water is thought to have once flowed on the surface.
Barge knows from her experiments that green rust forms when two contrasting solutions – one containing iron and one containing hydroxide – are mixed. On Earth, green rust has been found in such environments as non-oxygenated wet sediments and steel pipes that corrode in sea water.
Probing by laser
To detect green rust, Barge suggests using laser Raman spectroscopy, a technique which will be included on ESA’s ExoMars and NASA’s Mars 2020 missions. The technique involves directing a laser beam at a sample and then collecting and analyzing the light that is scattered from the spot to identify its molecular composition and structure. The scattered light contains fingerprint spectral features that allow us to determine the molecular makeup and mineralogy of the sample. Barge has teamed up with Pablo Sobron, a research scientist at the SETI Institute, an expert in laser-based spectroscopy applied to Mars exploration, to adapt the Raman technique for the detection and analysis of green rust.
But first, there needs to be a better understanding of where green rust will occur and how it can support habitability. The JPL Icy Worlds team (led by the Jet Propulsion Laboratory’s Isik Kanik) recently received a second five-year NASA Astrobiology Institute grant to study the habitability of icy worlds, including an investigation into how green rust might drive prebiotic chemistry, or chemistry that is a precursor to life.
“There’s a theory proposed by Michael Russell at JPL that green rust could have acted as a proto-enzyme to convert energy currencies on early Earth,” Barge said, referring to how lifeforms convert proton and electron gradients into chemical energy to drive metabolism and, thereby, life.
Green rust is especially interesting in this regard because it is a double layered hydroxide that can sandwich all sorts of interesting components relevant to life in between these layers, Barge added. These include phosphates, DNA, amino acids and proteins.
Dark matter is five times more plentiful in the universe than regular matter, but it does not emit, reflect or absorb light, making it not just dark but entirely transparent. But if dark-matter particles around black holes can produce gamma-rays (high-energy light), such emissions would give scientists a new way to study this mysterious material.
The process responsible for creating the gamma-rays is somewhat counterintuitive, because it seems to defy two common assumptions: that nothing can escape from a black hole and that there’s no such thing as a free lunch.
Jeremy Schnittman is a theoretical astrophysicist at the NASA Goddard Space Flight Center, and he’s beginning a project to look through data from the Fermi Gamma-ray Space telescope for signs of high-energy light around the edge of a black hole that might have been created by dark matter.
“We’re really just getting started on this part of the problem,” Schnittman said. “As a theoretical astrophysicist, I haven’t done a lot of data analysis in my career, so it’s a little bit of a learning curve for me. But fortunately I’m surrounded by people here at Goddard who are real experts at the Fermi data.”
Schnittman’s search for this dark-matter signal began with a computer program that he has been developing for about 10 years. It models in 3D the paths of particles as they zip through space near a black hole, while some of them get close enough to orbit around the black hole or fall in.
Just over a year ago, he decided to adjust the program to model dark-matter particles. The resulting video shows how the subatomic bits get caught up in the gravitational pull of the black hole and swirl around it in a region called the ergosphere (where all particles must orbit in the direction of the black hole’s spin). Some of the particles collide and destroy each other (also known as annihilation), and this produces a pair of gamma-rays.
These particles of light might normally fall into the black hole, helpless against its gravitational pull, were it not for something called the Penrose process.
In 1971, astrophysicist Roger Penrose showed that if two photons are created very close to a black hole, it’s possible for one of them to escape, while the other falls in. This flies counter to the commonly held idea that nothing can escape from a black hole, or at least nothing that goes past the “event horizon” — the point at which the gravitational pull is so strong that nothing, not even light, can ever exert enough force to get away.
According to the Penrose principle, the particles are not created beyond this point of no return, but under normal circumstances, it’s unlikely that either particle would have any means of getting away from the black hole. So the Penrose process still changes the fate of at least one particle, giving it an escape route.
In 2009, a group of researchers showed that the Penrose process could be applied to dark-matter particles that annihilate and form two gamma-rays. If dark-matter particles are annihilating near the surface of a black hole, telescopes on Earth could detect the escaping gamma-rays.
Schnittman’s work using the 3D computer model has shown many more paths that the particles can take, including some that are more likely to produce gamma-rays that can escape the black hole, and with even higher energies than had been previously predicted. A brief description of those results was published in the journal Physical Review Letters last December, and a longer description of the work has been accepted to the Astrophysical Journal.
With those results, Schnittman and his colleagues are now looking for this signal, although they said they expect it to be very dim compared to many other gamma-ray sources. The researchers are creating a list of target galaxies that have few gamma-ray sources and very massive black holes.
“The bigger the black hole, the bigger the signal,” Schnittman said. “It scales in a way that as your black hole [mass] goes up by a factor of 10, the expected signal goes way up, by something like a factor of 1,000.
“The first pass at observing this effect is almost certainly not going to yield an actual detection. But it will provide probably the strongest upper limit on this type of process that has ever been seen before — the idea of high-energy dark-matter particle reactions. Even that is progress.”
The particles that escape the black hole via the Penrose process not only go free, but they also leave with more energy than they started with. In fact, they have more energy than the pair of particles had combined. This, it would seem, is a free lunch.
Since Penrose’s original work, scientists have shown that not only does the escaping particle steal energy from its partner (essentially pushing off the other particle), but it also steals energy from the spinning black hole. Every Penrose particle that escapes slows the spin of the black hole by a very, very tiny amount.
(When he originally proposed the idea, Penrose wrote that this phenomenon could be used by an advanced society as an energy-producing garbage disposal, in which the garbage serves as the particle that falls into the black hole, producing a flux of high energy particles that escapes.)
Schnittman said he is reserved in his hopes for finding a dark-matter signal in the Fermi data. Not only will it be difficult to see such a small signal amid the noise of gamma-rays in the universe, but the existence of the signal also relies on a major unknown: whether or not dark-matter particles create gamma-rays when they annihilate.
The fact is, scientists don’t know what dark matter is made of, and they don’t know if dark-matter particles will annihilate in the way that Schnittman’s model predicts, if they do so at all. So if Schnittman did find a signal, it would mean a major breakthrough in the study of the nature of dark matter.
“That’s Nobel Prize kind of stuff,” Schnittman said. “It’s a long shot, but it would be a tremendous payoff if we found actual confirmation of dark-matter annihilation.”
Saturn’s icy moon Enceladus is looking better and better as a potential abode for alien life.
Chemical reactions that free up energy that could potentially support a biosphere have occurred — and perhaps still are occurring — deep within Enceladus’ salty subsurface ocean, a new study suggests.
This determination comes less than two months after a different research team announced that active hydrothermal vents likely exist on Enceladus’ seafloor, suggesting that conditions there could be similar to those that gave rise to some of the first lifeforms on Earth.
Astrobiologists regard the 314-mile-wide (505 kilometers) Enceladus as one of the solar system’s best bets to host life beyond Earth.
The satellite is covered by an icy shell, but it’s geologically quite active, as evidenced by the powerful geysers that blast continuously from its south polar region. These plumes contain significant amounts of water, which scientists think originates from a subsurface ocean.
Previous studies have suggested that this ocean is in contact with Enceladus’ rocky mantle, making possible all sorts of interesting chemical reactions. The new paper, published Wednesday (May 6) in the journal Geochimica et Cosmochimica Acta, further supports that notion.
The researchers studied mass-spectrometry measurements of the gases and ice grains in Enceladus’ plumes made by NASA’s Cassini spacecraft, which has been orbiting Saturn since 2004. The team used this information to develop a model that estimates the saltiness and pH of Enceladus’ plumes, and, by extension, the moon’s underground ocean.
The scientists determined that the ocean is likely salty and quite basic, with a pH of 11 or 12 — roughly equivalent to that of ammonia-based glass-cleaning solutions, but still within the tolerance range of some organisms on Earth. (The pH scale runs from 0 to 14. Seven is neutral; anything higher is basic, and anything lower is acidic.)
Enceladus’ subsurface sea contains dissolved sodium chloride (NaCl) — run-of-the-mill table salt — just as Earth’s oceans do, researchers said. But it’s full of sodium carbonate (Na2CO3), which is also known as washing soda or soda ash, as well.
So this alien water body is probably more similar to terrestrial “soda lakes,” such as Mono Lake in California, than it is to the Atlantic and Pacific oceans, study team members said.
Such inferences shouldn’t dishearten astrobiologists; a variety of lifeforms thrive in Mono Lake, including brine shrimp and many different types of microbe. And the new study provides other reasons to be optimistic about Enceladus’ life-hosting potential, researchers said.
For example, the team’s model suggests that the subsurface ocean’s high pH is generated by a process called serpentization, in which certain kinds of metallic rocks from Enceladus’ upper mantle are transformed into new minerals (including serpentine, hence the name) via interactions with water.
In addition to raising pH, serpentization results in the production of molecular hydrogen (H2) — a potential source of chemical energy for any lifeforms that may exist in the underground sea, researchers said.
”Molecular hydrogen can both drive the formation of organic compounds like amino acids that may lead to the origin of life, and serve as food for microbial life such as methane-producing organisms,” study lead author Christopher Glein, of the Carnegie Institution for Science in Washington, said in a statement.
“As such, serpentinization provides a link between geological processes and biological processes,” he added. “The discovery of serpentinization makes Enceladus an even more promising candidate for a separate genesis of life.”
Sunlight probably doesn’t flow through Enceladus’ underground sea, but any microbes that exist there may thus have access to two different sources metabolism-supporting energy sources — molecular hydrogen and the heat provided by hydrothermal vents.
More than 40,000 citizen stargazers have helped to classify over 2 million celestial objects and identify five never-before-seen supernovas, in a massive example of citizen science at work.
An amateur astronomy project of cosmic proportions, established by scientists at the Australian National University, asked volunteers to look through images taken by the SkyMapper telescope and search for new objects, with a particular focus on finding new supernovas.
The project was set up using the Zooniverse platform (run by the University of Oxford), which hosts many other citizen science projects, and which was promoted on the BBC2 TV series “Stargazing Live,” from March 18 to March 20. [Supernova Photos: Great Images of Star Explosions]
To participate in the project, volunteers signed up online and accessed the Zooniverse platform, which walked them through their tasks.
Zooniverse has hosted many space-related citizen science projects in the past, including hunts for alien planets, “space warp” galaxies and holes in cosmic clouds.
The participants were asked to look at star-filled patches of the night sky, taken by the SkyMapper telescope. The volunteers would look at images of the same region taken at different times, and search for changes that could indicate the presence of different celestial objects.
A supernova, for example, is a large star that has burned up most of its fuel and dies in a great explosion. A supernova eruption can briefly outshine all the light created by all the stars in an entire galaxy — so even a star that is normally too distant to see with a telescope may suddenly become visible if it explodes into a supernova. This means a SkyMapper volunteer might see a point of light appear where there previously was none.
“One volunteer was so determined to find a supernova that he stayed online for 25 hours. Unfortunately, he didn’t find one, but he did find an unusual variable star, which we think might explode in the next 700 million years or so,” Richard Scalzo, a researcher working with the SkyMapper telescope at the Australian National University (ANU) Research School of Astronomy and Astrophysics, said in a statement from ANU (a variable star is one that changes in brightness when observed from either, either due to changes in the star itself or something between the star and the observer). “It was a huge success. Everyone was really excited to take part.”
That excitement paid off, as the project required multiple volunteers. If one of the citizen scientists spotted a possible supernova or some other change in the sky images, then additional volunteers would examine that same region.
If the citizen observers confirmed a new object, then the professional scientists would do a more extensive background check in that region of the sky, Scalzo said in an email. After that, the scientists looked at the object’s spectra, a breakdown of the light the object emits. This can tell scientists all kinds of information about the object’s makeup and its history.
“Once we have at least one spectrum, we consider what other science we could do,” Scalzo said. “Type Ia supernovae can be used to study the expansion history of the universe and dark energy. Other kinds of supernovae can be used, singly or in large groups, to learn more about how different kinds of stars end their lives.”
Scalzo said the project required the assistance of so many human helpers because the computer programs need assistance. “Computers are very good at identifying supernova,” he said, “but you need a lot of data to train them.”
In other words, the scientists have to provide the computer program with lots of examples of what the supernova look like; it isn’t as simple as telling the computer to look for changes in the sky images.
“A few years ago, before SkyMapper was ready to take data, another group called the Palomar Transient Factory (PTF) partnered with the Zooniverse to allow volunteers to hunt for supernovae,” Scalzo said. “Over a few years, PTF found more than 500 real supernovae with the help of Zooniverse volunteers, and used the data to train a machine-learning algorithm to recognize supernovae more accurately than the volunteers could.”
The SkyMapper telescope has only identified 15 supernova, so Scalzo said there is still work to do to improve the programs.
The five newly discovered supernovas have already made their way into a cosmological study of dark energy by the SkyMapper scientists, but Scalzo said there is more work to be done before the results of that study are published. He added that there may be more work for citizen scientists to do with SkyMapper data in the future.
In the search for life beyond Earth, the mantra has usually been, “Follow the water.” But now, scientists say it may be possible for a waterless environment to give rise to alien life.
In a recent study, researchers at Cornell University proposed a formula for life that could thrive on Saturn’s largest moon, Titan. With its freezing temperatures, seas of liquid methane and toxic atmosphere devoid of any liquid water, it may seem unlikely that Titan could give rise to life. But in such environments, it may be possible for there to be methane-based, oxygen-free extraterrestrial life, the researchers said.
On Titan, temperatures of minus 292 degrees Fahrenheit (minus 180 degrees Celsius) would make it difficult for processes like metabolism and reproduction to occur. But the theorized cell membrane, which houses the cell’s organic matter, is composed of nitrogen instead of water, allowing it to do just that. [5 Bold Claims of Alien Life]
On Earth, living cells have a strong, permeable, water-based barrier called a lipid bilayer membrane. But that concept works only in environments with liquid water, so when astronomers are searching for life outside our solar system, they zoom in on small rocky exoplanets orbiting inside a star’s habitable zone — the band where liquid water can exist. But plenty of exoplanets (and even solar system moons) exist well outside this range, where liquid water can’t exist.
So astronomers have long been fascinated by nonaqueous life, and even the possibility that Titan may host methane-based life. Other than Earth, it is the only place in our solar system with liquid seas on its surface. It also hosts a mysterious process that consumes hydrogen, acetylene and ethane, the researchers said. All of these elements flow down from the atmosphere but never quite make it to the surface. So, could life be gobbling them up?
To investigate this possibility, Jonathan Lunine, an astronomer at Cornell University, collaborated with James Stevenson, a graduate student, and his adviser, Paulette Clancy, both of whom work at Cornell’s Chemical and Biomolecular Engineering Department.
“We’re not biologists, and we’re not astronomers — but we had the right tools,” Clancy said in a statement. “Perhaps it helped, because we didn’t come in with any preconceptions about what should be in a membrane and what shouldn’t. We just worked with the compounds that we knew were there and asked, ‘If this was your palette, what can you make out of that?’”
The researchers were able to model a cell that supports metabolism and reproduction but that’s constructed from nitrogen, carbon and hydrogen-based molecules — all of which are known to exist within Titan’s frigid seas. Like a lipid bilayer membrane here on Earth, it’s both rigid and flexible, controlling the transportation of materials in and out of the cell.
They named their theorized cell membrane an “azotosome.” (Azote is French for nitrogen, and lipsome is Greek for “lipid body,” so “azotosome” means “nitrogen body.”)
So far, the researchers have only shown that azotosomes could exist based on molecular simulations.
“Ours is the first concrete blueprint of life not as we know it,” Stevenson said. The next step will be to demonstrate in the laboratory how such membranes function in a methane environment. In the long run, scientists might also be able to model possible observable indicators of alien life.
If life does exist on Titan, it would demonstrate that methane, in addition to water, could be an indicator of life, and that life could more easily populate the cosmos.
Earlier this month, researchers made two big announcements: Saturn’s moon Enceladus likely harbors hot springs, and Jupiter’s huge satellite Ganymede apparently possesses a subsurface ocean that may contain more water than all of Earth does.
However, while the discovery makes Enceladus, which also has a subsurface ocean, even more intriguing to astrobiologists, Ganymede is still not a great bet for alien life, researchers say. [6 Most Likely Places for Alien Life in the Solar System]
Enceladus is the sixth-largest of Saturn’s moons, with a diameter of only about 314 miles (505 kilometers). Despite its tiny size, Enceladus has drawn a great deal of attention due to its erupting water geysers, first seen by NASA’s Cassini spacecraft in 2005. Now, scientists have found that Enceladus may have hot springs under its frozen crust. The discovery that the floor of its hidden ocean may be home to near-boiling temperatures is the first evidence of active hydrothermal vents beyond the oceans of Earth.
“This surely has implications regarding astrobiology, life-searching and all those kinds of topics,” said study author Hsiang-Wen Sean Hsu, a planetary scientist at the University of Colorado, Boulder.
Specifically, these new findings suggest that the conditions on Enceladus’ seafloor are similar to those found on Earth in a deep-sea field of hydrothermal vents known as Lost City in the Atlantic Ocean, which is home to a wide variety of animals, such as eels, snails, mussels, worms, shrimplike amphipods and flealike ostracods, said Gabriel Tobie, a planetologist at the University of Nantes in France.
Lost City consists of 196-foot-tall (60 meters) limestone chimneys that release alkaline fluid that is low in metals and lower than boiling temperature. In contrast, most other known hydrothermal vents on Earth give off metal-rich acidic fluid that is hotter than boiling temperature.
Alkaline hydrothermal vents might have been the birthplace of the first living organisms on the early Earth, supplying key nutrients and energy, Tobie said.
“For Enceladus, the new discovery of hot vents enhances its chance for life,” Tobie told Space.com.
NASA also announced that a salty ocean hides beneath the icy crust of Ganymede, the largest moon in the solar system. Scientists using NASA’s Hubble Space Telescope found that Ganymede’s ocean could harbor more water than is found on Earth. Ganymede’s sea may be about 60 miles (100 km) deep — 10 times the depth of Earth’s oceans.
However, this finding does not necessarily raise Ganymede’s chances for life, Tobie said.
“A major difference between Enceladus and Ganymede is the difference of pressure at the base of the ocean,” Tobie said. The pressure at the base of Enceladus’ ocean is rather low, at 50 to 100 bar — or about 50 to 100 times the atmospheric pressure of Earth at sea level. This low pressure permits water from circulating in underlying porous rocks, thus helping to drive chemical reactions that could lead life to emerge.
In contrast, the pressure at the base of Ganymede’s ocean is much higher — about 15,000 to 20,000 bar, Tobie said. Under such high pressure, not only is rock less porous, but water can form a kind of ice.
“A very thick layer of high-pressure ice more than 400 kilometers [250 miles] thick will form at the base of the ocean,” Tobie said. “Even if deep hot vents exist on Ganymede, the chance for life seems rather low due to the formation of this high-pressure ice layer.”
However, Ganymede is not the only watery moon of Jupiter. Prior research suggests that Europa, the fourth-largest moon of Jupiter, may possess both an ocean beneath its icy surface and hot springs.
“Like in Enceladus, the ocean in Europa would be directly in contact with the rock core, which will favor water-rock interactions and exchange of nutrients with the ocean,” Tobie said.
“Both Europa and Enceladus have a high astrobiological potential,” he added. “But for the moment, it is only a potential. Only future missions with in situ investigations will really answer if it is more than only a potential.”
Cosmic detectives are investigating a case of mistaken stellar identity: An exploding star that was once thought to be the oldest recorded nova — a nuclear explosion on the surface of a dead star — was more likely caused by the merger of two stars.
In 1670, a bright new star appeared in the constellation Cygnus, the Swan, and stayed there for two years — you can see the location of the new stars in this video. The short-lived star was grouped into the “nova” category, but over the last 30 years, astronomers have been questioning its identity.
A new research paper that examines the chemical makeup of the crime scene may be the final nail in the coffin. The researchers suggest that the so-called nova is instead the oldest example of another type of stellar explosion sometimes called a “red nova” — a somewhat newly-discovered phenomenon that scientists are still working to understand.
In 1670, a new star appeared just above the head of the swan that makes up the constellation Cygnus. Many astronomers took note of this newcomer, so its appearance and life span are well documented. It was dubbed Nova Vul 1670 —at the time, “nova” referred simply to any new star.
In the last 300 years, however, the word “nova” has taken on a much more specific and scientific meaning.
By today’s definition, a classic nova is an explosion that takes place on the surface of a white dwarf — the small, dense, nugget of leftover material from a star that has stopped burning. The white dwarf syphons material away from another nearby star, the pressure builds up on its surface and a nuclear reaction releases an incredible burst of energy. (Unlike Type Ia supernovas, which start in a similar fashion, the white dwarf in a nova is expected to survive through the explosion.)
Many things about CK Vulpeculae’s identity as a nova just don’t line up, said Tomasz Kaminski, a postdoctoral fellow at the European Southern Observatory.
For example, novas tend to burn in the sky for days — not years, as CK Vulpeculae did. Plus, the new star of 1670 didn’t disappear right away. After two years, it faded, then reappeared, then faded for good — which is very unusual for a nova, Kaminski said. And observations have shown that CK Vulpeculae’s temperature is much lower than that of a nova, where the radiation from the nuclear reaction continues to generate heat after the explosion is done, Kaminski said.
The new study, which is detailed in the March 23 edition of the journal Nature, may finally strip CK Vulpeculae of its “nova” title. Kaminski and his co-authors looked at the different molecules present in the wreckage of CK Vulpeculae, and found a profile that they say cannot be created by a classical nova.
But if isn’t a nova, then what is it?
In the new paper, Kaminski and his colleagues argue that CK Vulpeculae is a phenomenon with multiple names in scientific literature. They’ve been called red novas, red transients, luminous red transients and intermediate luminous optical transients (ILOTs), among others.
“People who study these red nova realized all the observations we have of these objects can be explained only if they explode as [an] effect of a collision and a merger of two stars,” Kaminski said.
The notion that a red nova could be a unique category of stellar explosion took hold in 2008, when astronomers watched two stars in a system orbit in toward each other and produce an explosion with the characteristics of a red nova, Kaminski said.
“Many of the novae we know from historical records could be this type; it’s just that people observe them during the outburst, and then no one really cared what happened with them,” Kaminski said. “And that’s why they didn’t realize maybe we’re dealing with some new phenomenon.”
Previous groups have suggested that CK Vulpeculae is a red nova. What Kaminski and his group have provided is the first look at the molecular profile of one of these objects, which he said is distinct from other stellar explosions. [Star Quiz: Test Your Stellar Smarts]
“This is a major step,” he said. The chemical profile shows the presence of molecules and isotopes that are strange compared to other types of stellar explosions, including classical novas, Kaminski said. In fact, the profile is actually somewhat unique among red nova, which may be a product of CK Vulpeculae’s age — perhaps something happens in these red novas over time that produces a unique bouquet of chemicals, he said.
The researchers made their observations with the submillimeter-wavelength Atacama Pathfinder Experiment (APEX) telescope and Effelsberg radio telescope.
Kaminski cautioned that scientists are still working to demonstrate that red novas are, in fact, the products of stellar mergers.
Noam Soker, an astrophysicist at the Technion Israel Institute of Technology, was one of the scientists who previously suggested that CK Vulpeculae was a red nova. He and some of his colleagues have theorized that red novas are not the result of suddenly stellar mergers but rather are produced by the gradual accretion of matter from one star to another. He and Kaminski said one thing that would help clarify the cause of a red nova would be observations inside the clouds of debris, to see the stars that remain there.
Kaminski said that, right now, the available evidence suggests that CK Vulpeculae is a red nova. But it’s possible that in 10 years, someone will come up with a different explanation for how this stellar explosion came to be.
“This is science and astronomy: You propose something new, and everyone is welcome to find supporting evidence, or disprove it with some new theory or new observations,” he said.
This finding, which was made by the SOFIA flying observatory, may shed light on how the dust that helped form countless stars and galaxies was created, the scientists added.
The elements that make up everything from people to planets are essentially stardust. These elements are forged in stars by nuclear fusion, which fuse small atoms such as hydrogen and helium into larger ones such as carbon and iron. [Supernova Photos: Amazing Star Explosions]
For years, scientists have tried to explain the vast amounts of dust seen in the early universe. The leading explanation was that this dust was created by exploding stars known as supernovas.
However, researchers also thought supernovas should excel at shattering and destroying dust as well. Prior research suggested that up to 80 percent or more of the dust that supernovas might generate could get destroyed by the so-called “reverse shocks” of these explosions. Reverse shocks are shockwaves rebounding off the cold, dense matter surrounding supernovas.
“It’s been known that ‘we are all made of star stuff,’ but the details of how newly formed ‘star stuff’ survives to later become the seeds for stars and planets is a bit murky,” said lead study author Ryan Lau, an astronomer at Cornell University.
One potential alternative source of the ancient dust seen in the early universe was that “some less powerful stars that don’t go supernova go through a phase where they gently blow off their innards and form dust,” Lau said. “However, this way of forming dust isn’t very efficient, because it takes a while for these less powerful stars to evolve to that point.”
Now Lau and his colleagues have unexpectedly confirmed that supernovas can be dust factories.
“Finding this surviving dust is surprising to me because when I think of a supernova, I imagine a very harsh, violent environment that is very inhospitable to dust and other things that happen to be caught in the explosion,” Lau told Space.com.
The astronomers employed the Stratospheric Observatory for Infrared Astronomy (SOFIA), a joint project of NASA and the German Aerospace Center housed aboard a modified Boeing 747SP jumbo jet. They analyzed dust in the middle of Sgr A East, the remnant of a supernova located near the center of the Milky Way. This remnant, known as Sgr A East, is about 10,000 years old.
“We were on a flying observatory traveling at 600 mph (965 km/h) at an altitude of 45,000 feet (13,715 meters) to take images of a 10,000-year-old supernova remnant located 27,000 light-years away from us at the center of our galaxy,” Lau said. “No other currently operating observatory other than the Stratospheric Observatory for Infrared Astronomy could detect this dust.”
The scientists found that about 7 to 20 percent of the initial dust of the supernova survived its reverse shock.
“One of the most surprising things is that we were not expecting to see this at all,” Lau said. “We were looking at the two brighter features to the right and to the left of the supernova dust we found.”
The researchers suggest the dust survived the supernova’s reverse shock because of dense gas surrounding the explosion, which slowed the debris from the supernova, helping the dust cool greatly and preventing its destruction. This finding implies that ancient supernovas could have generated the vast amounts of dust seen in the early universe.
The scientists detailed their findings online today (March 19) in the journal Science.
A decade ago, a tiny but mighty probe descended into the soupy atmosphere of Titan. This moon of Saturn is of great interest to astrobiologists because its chemistry and liquid cycle remind us of what the early Earth could have looked like before life arose.
The probe, called Huygens, made it to the surface and transmitted imagery all the way. It remained alive on the surface for more than an hour, transmitting data to NASA’s orbiting Cassini spacecraft for later analysis by scientists.
During long-term missions, sometimes it takes years to examine all the data gathered by probes because there is so much for investigators to parse through. A decade later, we are only now starting to understand how the atmosphere of Titan formed, mostly based on what Huygens observed in January 2005.
The data could help settle a debate about how Titan got its atmosphere, said Christopher Glein, a postdoctoral researcher at the University of Toronto in Canada.
One scenario, more popular before Huygens reached the surface, suggested that the moon nabbed nitrogen, methane and noble gases that were floating in the solar system during formation. Another theory, and one that Glein supports, holds that the atmosphere was generated within Titan as a consequence of hydrothermal activity.
“That’s the idea I am exploring — producing gases inside of Titan,” Glein said.
His new paper, titled “Noble gases, nitrogen, and methane from the deep interior to the atmosphere of Titan,” was published in the journal Icarus.
Seeking noble gases
The Huygens probe found an isotope of argon — a noble gas also found in Earth’s atmosphere — that appeared to be made within Titan’s presumed rocky core. Argon-40 is a radioactive product that is formed from the radioactive decay of potassium-40. It originated inside of Titan, Glein said, and then got into the atmosphere by some means, perhaps by venting, or through cryovolcanism (cold volcanoes that may erupt mixtures of liquid water).
How the gas was released is a reflection of geophysical processes that depend on Titan’s internal structure. Perhaps Titan is even warmer than thought. Some models predict that Titan’s interior should be warm, but for that to happen its structure would need to be differentiated.
This could mean that Titan has (or once had) a hot rocky core surrounded by an ocean with an icy shell overlaid on top. This would be similar in structure to what is hypothesized on Jupiter’s satellite Ganymede, the largest moon in the solar system, and unlike that of Callisto, another large moon of Jupiter that is mostly undifferentiated, Glein said. [Amazing Photos: Titan, Saturn's Largest Moon]
“There’s not unanimous agreement,” he added. “The key observation is the gravity field — which tells us how much mass separation occurred during the formation and evolution of Titan. If there is a rocky core and ocean-ice shell, there should be a great deal of separation. But Titan is a no-man’s land of ambiguity between Ganymede and Callisto. We can’t be definitive yet.”
Glein’s contribution to the body of knowledge on the origin of Titan’s atmosphere was to create a mathematical representation of Titan’s volatile element geochemistry, assuming that the moon is differentiated and the noble gases originated from the rocky core.
“I did some calculations and connected the dots together. This could all make sense in terms of a larger story,” he said
Glein assumed the building blocks of Titan would have a chemistry similar to a certain kind of ice that is reflective of primitive solar system material, such as comets. The carbon dioxide and ammonia found in these small bodies can produce methane and nitrogen if they are cooked in a hydrothermal system. Inside of Titan, it’s possible this combination would account for the nitrogen and methane that now reside in its atmosphere.
According to Glein, some noble gases behave very similarly (in terms of how easily they form gases) to methane and nitrogen, which are the gases that give Titan an atmosphere. For example, nitrogen is similar to argon, and methane behaves similarly to krypton. These noble gas analogies allowed Glein to calculate how much methane and nitrogen can go from the rocky core to the atmosphere, a distance of at least 300 miles (500 kilometers).
For example, standard models show that the whiff of argon-36 detected by Huygens can be explained if only 2 percent of the total amount in the core make it out to the top. Similarly, nitrogen should also bleed outwards at about 2 percent, and Glein found that this is enough to explain the amount of nitrogen we find in Titan’s atmosphere. He came to a similar conclusion using krypton to estimate the outgassing percentage for methane.
The challenge is that much of the work is based on a single mission and only a few hours of data. While Cassini still makes regular flybys past Titan, its instruments (coupled with the greater distance) are not sensitive enough to gather precise abundances of trace noble gases that would improve on the Huygens results. Similarly, telescopic observations are hard because Titan is too far away for this exacting work.
“I think ultimately we are going to need another mission to Titan, such as a rover, and I think probably the Jupiter system more in the immediate future. There is useful information out there,” Glein said.
“One of the next questions is trying to address why Ganymede and Callisto don’t have atmospheres, like Titan,” he added. “If we can get new data from Ganymede especially, we can test this model and get a general understanding of what’s going on. This is also a key next step in testing the hypothesis of a hydrothermal solar system, where heat sources inside icy worlds allow liquid water to persist, and drive geochemical transformations of carbon and nitrogen. This could set the stage for subsurface life.”
NASA’s forthcoming Juno mission arrives at Jupiter in 2016, and could help in terms of measuring Jupiter’s global water abundance and explaining how its moons were formed from the gas cloud that birthed Jupiter, Glein said. Further ahead is Europe’s JUICE mission, which will look at several of Jupiter’s icy moons in the 2030s and could gather more information on Ganymede’s chemistry and interior.
Astronomers have discovered the largest and most luminous black hole ever seen — an ancient monster with a mass about 12 billion times that of the sun — that dates back to when the universe was less than 1 billion years old.
It remains a mystery how black holes could have grown so huge in such a relatively brief time after the dawn of the universe, researchers say.
Supermassive black holes are thought to lurk in the hearts of most, if not all, large galaxies. The largest black holes found so far in the nearby universe have masses more than 10 billion times that of the sun. In comparison, the black hole at the center of the Milky Way is thought to have a mass only 4 million to 5 million times that of the sun.
Although not even light can escape the powerful gravitational pulls of black holes — hence, their name — black holes are often bright. That’s because they’re surrounded by features known as accretion disks, which are made up of gas and dust that heat up and give off light as it swirl into the black holes. Astronomers suspect that quasars, the brightest objects in the universe, contain supermassive black holes that release extraordinarily large amounts of light as they rip apart stars.
So far, astronomers have discovered 40 quasars — each with a black hole about 1 billion times the mass of the sun — dating back to when the universe was less than 1 billion years old. Now, scientists report the discovery of a supermassive black hole 12 billion times the mass of the sun about 12.8 billion light-years from Earth that dates back to when the universe was only about 875 million years old.
This black hole — technically known as SDSS J010013.02+280225.8, or J0100+2802 for short — is not only the most massive quasar ever seen in the early universe but also the most luminous. It is about 429 trillion times brighter than the sun and seven times brighter than the most distant quasar known.
The light from very distant quasars can take billions of years to reach Earth. As such, astronomers can see quasars as they were when the universe was young.
This black hole dates back to a little more than 6 percent of the universe’s current age of 13.8 billion years.
“This is quite surprising because it presents serious challenges to theories of black hole growth in the early universe,” said lead study author Xue-Bing Wu, an astrophysicist at Peking University in Beijing.
Accretion discs limit the speed of modern black holes’ growth. First, as gas and dust in the disks get close to black holes, traffic jams slow down any other material that’s falling into them. Second, as matter collides in these traffic jams, it heats up, emitting radiation that drives gas and dust away from the black holes.
Scientists still do not have a satisfactory theory to explain how these supermassive objects formed in the early universe, Wu said.
“It requires either very special ways to quickly grow the black hole or a huge seed black hole,” Wu told Space.com. For instance, a recent study suggested that because the early universe was much smaller than it is today, gas was often denser, obscuring a substantial amount of the radiation given off by accretion disks and thus helping matter fall into black holes.
The researchers noted that the light from this black hole could help provide clues about the dark corners of the distant cosmos. As the quasar’s light shines toward Earth, it passes through intergalactic gas that colors the light. By deducing how this intergalactic gas influenced the spectrum of light from the quasar, scientists can deduce which elements make up this gas. This knowledge, in turn, can provide insight into the star-formation processes that were at work shortly after the Big Bang that produced these elements.
“This quasar is the most luminous one in the early universe, which, like a lighthouse, will provide us chances to use it as a unique tool to study the cosmic structure of the dark, distant universe,” Wu said.
An explosion on the surface of a dying star has is helping to clear up a mystery behind copious amounts of lithium seen in the universe.
By studying Nova Delphini 2013 (V339 Del), astronomers were able to detect a precursor to lithium, making the first direct detection of the third lightest element whose abundance had long remained in the theoretical realm.
“There have been no direct observational evidence for lithium production in novae before our result,” lead author Akito Tajitsu, of the National Observatory of Japan, told Space.com via email. “But many scientists made predictions about it.”
When V339 Del was spotted by an amateur astronomer on Aug. 14, 2013, it was just beyond the limit of being visible to the naked eye, though it was visible in binoculars and telescopes. Within two days, it had brightened enough to be seen without instruments in regions without too much light pollution, the first naked-eye nova since 2007.
Novae form when material from one star in a close binary surface is dumped onto the surface of its white dwarf companion. The runaway thermonuclear reaction causes the surge in brightness, which in turn creates more complex elements than the hydrogen and helium that dominate the inside of most stars.
One element predicted to form in the outburst is the most abundant isotope of lithium, lithium-7 (Li-7). While most heavy elements form inside of stars and through supernovae, lithium-7 is too fragile to withstand the high temperatures found within most stellar cores.
“Lithium is one of the so-called ‘light elements,’ together with beryllium and boron. These elements are much less abundant in the Milky Way and in the Solar System than their neighbors on the periodic table,” Margarita Hernanz, of the Institute of Space Sciences in Spain, told Space.com by email. Hernanz, who studies the late stages of stellar evolution, including explosions, was not part of the research project.
“They are not formed only inside of stars like the others. Their synthesis relies on processes less efficient than nuclear reactions inside the stars.”
Some of the lithium in the universe formed when the universe first got started, during the Big Bang. Cosmic rays interacting with stars and interstellar matter may have formed more. But these events do not provide enough lithium to equal the amount of the element present today.
In the 1950s, scientists suggested that an isotope of beryllium (Be-7) could form near the surface of the star. If the fresh Be-7 was transported to the cooler outer regions before it decayed into Li-7, the temperatures would not destroy the new element. But the difficulty in observing lithium from the ground made it a challenge to verify observationally — until now.
Tajitsu and his team used Japan’s Subaru Telescope on the summit of Mauna Kea, Hawaii. Its lofty altitude, large aperture and high sensitivity allowed the team to examine the composition of the material expelled from V339 Del at four points after the explosion. During the first three epochs, they were able to identify a significant quantity of Be-7 ejected from the nova at a high velocity.
By the end of their observations, however, no beryllium was visible; the team is still investigating the reason behind the complete disappearance. Continuing studies of V339 Del may help answer lingering questions such as this.
Beryllium-7 has a half-life of 53 days. Every eight weeks or so, the amount of beryllium is reduced by half as it decays into lithium-7, which is even more difficult to detect. In order to observe the rapidly shifting beryllium before it transitions into lithium, scientists must observe the new nova quickly, which can create scheduling challenges with large telescopes.
By studying lithium in the galaxy, scientists can understand how it evolves chemically over time.
“In general, all the chemical elements play an important role in galactic evolution, because they determine the chemical composition of the galactic gas from which stars form,” Hernanz said.
“The study of the so-called chemical evolution of the galaxy determines how this chemical composition evolves along the history of the galaxy.”
Tajitsu and his team hope to repeat their observations for many other classical novae, confirming how they might contribute to the evolution of lithium in the current universe.
Other than the first detection of beryllium-7, V339 Del has nothing to make it stand out from other novae. It appears to be a typical explosion on a carbon and oxygen dwarf. This means that classical novae could easily contribute a substantial amount of lithium to the galaxy.
The research, along with Hernanz’s accompanying News & Views article, was published online today (Feb. 18) in the journal Nature.