Now, scientists think they may have an answer to this long-standing puzzle: The constant pummeling that formed Earth may have altered its composition.
Earth formed by accretion — the gradual accumulation of bits of matter due to their mutual gravitational pull. Heat from the radioactivity of accreting meteorites and from the impacts of rocks constantly bombarding the newborn Earth caused the planet to melt enough for heavy materials to sink downward. This resulted in an iron-rich core, above which lay a rocky mantle and crust
The most primitive meteorites, known as chondrites, are the primordial material from which the planets were formed. Among these, previous research found that enstatite chondrites have a mix of isotopes that is remarkably similar to that of Earth, which suggests they might be the raw material from which Earth originated. (Isotopes are versions of an element that have different numbers of neutrons.)
Strangely, Earth appears to be low in silicon, potassium and sodium, and enriched in magnesium, calcium and aluminum, compared with enstatite chondrites. Now, for the first time, scientists think they may have an explanation for this mystery.
“The most exciting aspect of these results is that it is the first time that anyone comes close to answering the question, ‘Why does Earth have the same isotopic composition as enstatite chondrites but a different chemical composition?’”study lead author Asmaa Boujibar, a planetary scientist at NASA’s Johnson Space Center in Houston, told Space.com.
In experiments, the researchers melted enstatite chondrites at various pressures. This procedure mimicked how accreting rock might have behaved during Earth’s formation.
The experiments suggested that the heat of the newborn Earth left the rocks constituting its crust enriched in silicon and relatively low in magnesium. The research team’s computer models then suggested that the many cosmic impacts that pulverized the young Earth stripped a great deal of this crust off the planet, leaving Earth relatively depleted of silicon and rich in magnesium.
The heat from these impacts also would have made potassium, sodium; calcium and aluminum escape as gases from Earth. However, much of the calcium and aluminum would have condensed and returned back to Earth. That could help explain why the proportions of these elements on Earth are different from their proportions in enstatite chondrites, the researchers said.
The nature of the impacts that might have caused this heat-based loss of matter from Earth remain uncertain, Boujibar said, adding that the impacts might have involved giant rocks, very fast rocks or very hot rocks.
Uncovering the nature of these impacts would shed light on how Earth formed, she added. For instance, very fast rocks might be the result of Jupiter moving closer and then farther away from, the sun and gravitationally slinging around rocks at high speeds, while very hot rocks were seen in the solar system soon after it formed.
Boujibar and her colleaguesdetailed their findings online Sept. 23 in the journal Nature Communications.
Scientists are referring to the resurrected cloud as a “radio phoenix,” named after the mythical bird that is reborn from its ashes, because the high-energy electrons within it are once again radiating mostly at radio frequencies, according to a statement from NASA. The cloud is found in Abell 1033, a galaxy cluster of more than 350 galaxies about 1.6 million light-years from Earth.
The above video shows new images of Abell 1033 created using light collected by NASA’s Chandra X-ray Observatory, radio emissions collected by the Very Large Array, and optical light from the Sloan Digital Sky Survey. Combining data from these telescopes, as well as the Westerbork Synthesis Radio Telescope in the Netherlands, astronomers were able to figure out what brought the radio phoenix back to life.
Astronomers working on the project believe the supermassive black hole that sits near Abell 1033′s center erupted long ago, releasing a stream of high-energy electrons (subatomic particles that make up atoms) that formed a cloud hundreds of thousands of light-years wide and radiating radio emissions. As the electrons gradually lost energy over millions of years, the cloud’s emissions began to fade, the NASA statement said.
Galaxy clusters can consist of hundreds or even thousands of individual galaxies, as well as dark matter, and huge reservoirs of hot gas, the NASA statement said. As the electron cloud in Abell 1033 grew dimmer, another cluster of galaxies slammed into the original cluster, sending shock waves through the system.
These shock waves, similar to sonic booms produced by supersonic jets, passed through the dormant cloud of particles, compressed the cloud and re-energized the electrons, essentially waking them up. The now wide-awake electrons once again radiated radio frequencies — the phoenix had risen from the ashes.
The image of Abel 1033 shows X-rays from Chandra in pink and radio data from the VLA in green. Background imagery comes from observations from the SDSS and a map of the density of galaxies, made from the analysis of optical data, is seen in blue.
Astronomers believe this image shows the radio phoenix soon after it was resurrected, because these types of radio sources fade “very quickly” (on a cosmic scale) when located close to the center of a galaxy cluster, the NASA statement said. Because of the intense density, pressure and magnetic fields near the center of Abell 1033, scientists expect the radio phoenix to radiate for tens of millions of years.
Researchers have a new way to rank the life-hosting potential of alien worlds.
The “habitability index” metric could help guide the operations of future observatories, such as NASA’s James Webb Space Telescope (JWST), that will scan exoplanet atmospheres for signs of life, scientists said.
“Basically, we’ve devised a way to take all the observational data that are available and develop a prioritization scheme so that as we move into a time when there are hundreds of targets available, we might be able to say, ‘OK, that’s the one we want to start with,” study lead author Rory Barnes, of the University of Washington, said in a statement.
Traditionally, assessing habitability has been a yes-or-no affair, with researchers attempting to determine whether or not an alien world resides in the “habitable zone” of its host star. This region of space, also known as the “Goldilocks zone,” is that just-right range of distances that can allow the existence of liquid water on a planet’s surface.
But the new index is more involved, integrating information about an exoplanet’s composition (e.g., rocky or not rocky), reflectivity and orbital path to come up with the probability that it can indeed support liquid surface water.
The original concept “was a great first step, but it doesn’t make any distinctions within the habitable zone,” Barnes said. “Now it’s as if Goldilocks has hundreds of bowls of porridge to choose from.”
Calculations performed in the new study, which has been accepted for publication in the Astrophysical Journal, suggest that the best candidates for alien life are exoplanets that receive about 60 to 90 percent as much energy from their host stars as Earth gets from the sun, researchers said.
Astronomers have discovered nearly 2,000 exoplanets to date, and many more await confirmation by follow-up observations and analysis. More than half of these finds have come courtesy of NASA’s Kepler space telescope, which notices the tiny brightness dips caused when planets cross the face of, or transit, their host stars from the instrument’s perspective.
JWST, which is scheduled to launch in late 2018, will also make use of such transits. Among many other tasks, the $8.8 billion observatory will study starlight that passes through exoplanet atmospheres for signs of oxygen, methane and other gases that could have been produced by living organisms.
The new habitability index should help scientists optimize JWST’s life-hunting work, study team members said.
“This innovative step allows us to move beyond the two-dimensional habitable zone concept to generate a flexible framework for prioritization that can include multiple observable characteristics and factors that affect planetary habitability,” co-author Victoria Meadows, also of the University of Washington, said in the same statement. “The power of the habitability index will grow as we learn more about exoplanets from both observations and theory.”
If you could hear the stuff that swirls around black holes, superdense white dwarfs and young stars, what would it sound like? Probably like the empty spaces on the radio dial, researchers say.
Simone Scaringi, a postdoctoral researcher at the Max Planck Institute in Germany, studies “accretion disks” around massive objects. An accretion disk is acollection of matter that gathers in a disc shape around a rotating object. Scaringi and his team looked at flickering in the light emissions of galactic nuclei, black holes, young stellar objects and white dwarfs, which are the collapsed remnants of massive stars. You can hear what accretion disks around black holes sound like here.
Using observations from NASA’s Kepler space telescope, ground-based instruments and the European Space Agency’s XMM-Newton satellite, the scientists found it’s possible to turn the flickering into sound.
“It’s something I always wanted to try and do,” Scaringi told Space.com. “This project gave me a good excuse to give it a try. For me, it’s the obvious way to explain this research. … I can show it’s a different type of noise.”
The flickering comes from the energy released by material in accretion disks that falls in toward the central object. Scaringi treated the flashes’ frequency as that of a sound wave; for example, a frequency of 10 flashes a second was converted to a wave consisting of 10 cycles per second, or 10 Hertz. There was one “cheat”: Scaringi had to scale the frequencies to the range of human hearing, as most of them would be far too low for humans to hear.
The result is a white-noise-like sound, which helps illustrate the team’s main finding: The physics of accretion disks scale up and down and remain mostly the same, no matter how massive the object at the center of the disk is.
To many people, this finding might be intuitive; after all, stirring creamer into a cup of coffee produces a shape not unlike that of a spiral galaxy. And scientists and philosophers have remarked on the similarity between the shapes of spiral galaxies and accretion discs around stars.
Intuitions, however, are often wrong. Many scientists were unsure whether the same physical laws applied at widely differing scales. One issue, Scaringi said, is relativity. Black holes, for example, have the mass of multiple suns — millions or billions of suns in the case of the supermassive black holes at the centers of galaxies. The difference in gravitational forces between the area near the black hole’s “point of no return,” called the event horizon, and the regions farther away is large, whereas for young stars it is comparatively small.
Scaringi’s team has shown that the behavior of accretion disks will scale up; one can apply the same basic laws to a large black hole, or a galaxy, or a young solar system. But the mechanism is still unknown.
“As far as the detailed modeling is concerned, we’re still not there,” Scaringi said. “We seem to observe that it turns out that they all seem to scale, but the detailed physics as to why the scaling relation holds is not clear yet.”
The study appears in the Oct. 9 issue of the journal Science Advances.
A huge telescope array will allow scientists to conduct the most sensitive and exhaustive search for signs of alien civilizations to date when it comes online, the project’s backers say.
The Square Kilometer Array (SKA), currently planned to begin construction in 2018, could enable the search for intelligent alien life to piggy-back on other scientific observations, scouring the galaxy with unprecedented precision.
“A unique aspect for the search of life in the universe is the question of whether advanced lifeevolves intelligence,” Andrew Siemion said at the Astrobiology Science Conference in Chicago in June. [13 Ways to Hunt Intelligent Alien Life]
Siemion, who holds joint appointments with the University of California, Berkeley, the Netherlands Institute for Radio Astronomy and Radbound University in the Netherlands, hunts for signs of alien technology in the universe.
“The only way to answer that in the foreseeable future is to look directly for evidence” of intelligence, Siemion said. “For that, you need a large telescope.”
The Square Kilometer Array is an enormous radio telescope that will be built in South Africa and Australia. Funded by a consortium of different countries, the SKA will combine thousands of small antennaeacross the globe instead of a single large dish, allowing unprecedented sensitivity in radio astronomy.
Using such a costly instrument for a single scientific study, especially one as speculative as the search for extraterrestrial intelligence (SETI), is unheard of in astronomy. But SETI scientists figured out a way to obtain significant telescope time nearly 30 years ago, when they began to piggy-back on other users’ observations at the enormous Arecibo Observatory in Puerto Rico, duplicating their observations with very little loss of sensitivity. Today, SETI researchers are able to obtain thousands of hours of observations annually, which they diligently scrutinize for radio signals from beyond Earth.
According to Siemion, data from the SKA could be similarly piggy-backed. But while Arecibo utilizes a single large dish, the SKA will be much larger than the biggest radio telescope operating today, allowing scientists to search for fainter signals.
Construction on the SKA should begin in 2018. The first phase, planned for completion by 2020, would allow for about 10 percent of the collecting area of the full instrument at low and mid-range frequencies.
According to a paper Siemion authored last fall, a five-year campaign by the first phase of the SKA could allow scientists to survey more than 10,000 stars. When completed, the SKA could detect signals as faint as those emitted by aircraft radars on Earth from every star within almost 200 light-years.
Earth began leaving its mark in the galaxy when humanity started transmitting signals by radio. These signals radiate outward from the planet, and could theoretically be detected by other civilizations. Given the enormous size of the spectrum that radio waves cover, scientists have suggested a number of preferred frequencies to hunt for extraterrestrial communication. [The Serious Search for Intelligent Life: 4 Key Questions (Video)]
As technology has improved on Earth, however, humanity has begun to reduce the radio-wave leakage into space. This could suggest that the window for observing accidentally broadcast signals is brief — perhaps only a century or so. While scientists still hope to detect such signals, they also aim to find deliberately transmitted radio waves, which have been designed to travel through space.
The SKA concentrates on a frequency region known as the “terrestrial microwave window,” the spectral region of low natural noise between the galactic background and the emission and absorption of water and oxygen in Earth’s atmosphere. These frequencies can travel through the space between stars and through the water-laden atmosphere of Earth or any other planet with ease, leading scientists to suspect that distant civilizations might use them to communicate
SETI scientists aren’t just searching for signals broadcast at random. They also hope to eavesdrop on interplanetary communications.
If alien technology spreads to multiple planets within a single system, it is feasible to expect these various outposts to communicate with one another. If those planets lie along Earth’s line of sight, and observations are made when the planets are communicating with each other, it is possible that the SKA could pick up those broadcasts, researchers said.
In addition to the recent spate of planets unearthed by NASA’s Keplermission, the European Space Agency’s Gaia spacecrat and future missions such as NASA’s Transiting Exoplanet Survey Satellite(TESS) could produce a catalog of properly aligned planetary systems to watch. Life-hunting researchers have already begun eavesdropping on some of Kepler’s discoveries, for example.
“We’re going to have all kinds of data to figure out how to build these databases in coming years,” Siemion said.
Although the terrestrial microwave window will be the primary focus of the SETI search with the SKA, Siemion cautions that it is not the only potential signal for communication.
“We don’t know exactly what E.T. is going to do,” he said.
Stephen Hawking may have just solved one of the most vexing mysteries in physics — the “information paradox.”
Einstein’s theory of general relativity predicts that the physical information about material gobbled up by a black hole is destroyed, but the laws of quantum mechanics stipulate that information is eternal. Therein lies the paradox.
Hawking — working with Malcolm Perry, of the University of Cambridge in England, and Harvard University’s Andrew Stromberg — has come up with a possible solution: The quantum-mechanical information about infalling particles doesn’t actually make it inside the black hole.
“I propose that the information is stored not in the interior of the black hole, as one might expect, but on its boundary, the event horizon,” Stephen Hawking said during a talk today (Aug. 25) at the Hawking Radiation conference, which is being held at the KTH Royal Institute of Technology in Stockholm, Sweden.
The information is stored at the boundary as two-dimensional holograms known as “super translations,” he explained. But you wouldn’t want super translations, which were first introduced as a concept in 1962, to back up your hard drive.
“The information about ingoing particles is returned, but in a chaotic and useless form,” Hawking said. “For all practical purposes, the information is lost.”
Hawking also discussed black holes — whose gravitational pull is so intense that nothing, not even light, can escape once it passes the event horizon — during a lecture last night (Aug. 24) in Stockholm.
It’s possible that black holes could actually be portals to other universes, he said.
“The hole would need to be large, and if it was rotating, it might have a passage to another universe. But you couldn’t come back to our universe,” Hawking said at the lecture, according to a KTH Royal Institute of Technology statement. “So, although I’m keen on spaceflight, I’m not going to try that.”
Located at the heart of a dwarf galaxy known as RGG 118, the black hole contains about 50,000 times more mass than the sun. It’s therefore less than half as heavy as the second-smallest known supermassive black hole, researchers said.
“It might sound contradictory, but finding such a small, large black hole is very important,” lead author Vivienne Baldassare, a doctoral student at the University of Michigan (UM) in Ann Arbor, said in a statement. “We can use observations of the lightest supermassive black holes to better understand how black holes of different sizes grow.” [Images: Black Holes of the Universe]
There are two types of black hole — stellar mass and supermassive. Stellar-mass black holes weigh a few times as much as the sun and form after the collapse of huge stars. Supermassive black holes reside at the center of most, if not all, galaxies and are thought to evolve and grow along with the collection of stars they inhabit.
RGG 118 is located about 340 million light-years from Earth; the dwarf galaxy was originally identified by the Sloan Digital Sky Survey. Baldassare and her colleagues were able to determine the mass of RGG 118′s central black hole by studying the motion of gas near the galaxy’s center with the 21-foot (6.5 meters) Clay Telescope in Chile.
At 50,000 solar masses, the black hole is quite a lightweight. For example, the Milky Way galaxy’s central supermassive black hole is about 100 times more massive. The heaviest known black holes weigh about 200,000 times as much as the one in RGG 118.
“In a sense, it’s a teeny supermassive black hole,” said co-author Elena Gallo of UM in another statement.
The team also used NASA’s Chandra X-ray Observatory to measure the X-ray brightness of RGG 118′s hot gas, which allowed them to calculate how quickly the black hole is gobbling up material. The scientists found that RGG 118 is consuming material at about 1 percent the maximum rate — similar to that of other, larger supermassive black holes.
“This little supermassive black hole behaves very much like its bigger, and in some cases much bigger, cousins,” said study co-author Amy Reines, also of UM. “This tells us black holes grow in a similar way, no matter what their size.”
Scientists still aren’t sure exactly how supermassive black holesare born and grow. One idea posits that huge clouds of gas collapse into “seed” black holes, which merge over time to form the larger, supermassive black holes. Other researchers think they form when a giant star, approximately 100 times the mass of the sun, runs out of fuel and collapses into a black hole.
“This black hole in RGG 118 is serving as a proxy for those in the very early universe, and ultimately may help us decide which of the two [ideas] is right,” Gallo said.
Active black holeshelp shape how their galaxies grow and evolve, regulating temperature and the movement of the gas and dust that grow into stars. The small size of RGG 118′s black hole indicates that the dwarf galaxy has likely never endured a mergerwith a neighbor — the process by which larger galaxies are thought to grow, researchers said.
“These little galaxies can serve as analogs to galaxies in the earlier universe,” Baldassare said. “By studying how galaxies like this one are growing and feeding their black holes and how the two are influencing each other, we could gain a better understanding of how galaxies were forming in the early universe.”
The research, which included a fourth author, Jenny Greene of Princeton University, is available online in the Astrophysical Journal Letters.
Planetary Resources deployed its first spacecraft from the International Space Station last month, and the Washington-based asteroid-mining company aims to launch a series of increasingly ambitious and capable probes over the next few years.
The goal is to begin transforming asteroid water into rocket fuel within a decade, and eventually to harvest valuable and useful platinum-group metals from space rocks.
“We have every expectation that delivering water from asteroids and creating an in-space refueling economy is something that we’ll see in the next 10 years — even in the first half of the 2020s,” said Chris Lewicki, Planetary Resources president and chief engineer Chris Lewicki.
“After that, I think it’s going to be how the market develops,” Lewicki told Space.com, referring to the timeline for going after asteroid metals.
“If there’s one thing that we’ve seen repeat throughout history, it’s, you tend to overpredict what’ll happen in the next year, but you tend to vastly underpredict what will happen in the next 10 years,” he added. “We’re moving very fast, and the world is changing very quickly around us, so I think those things will come to us sooner than we might think.”
Planetary Resources and another company, Deep Space Industries, aim to help humanity extend its footprint out into the solar system by tapping asteroid resources. (Both outfits also hope to make a tidy profit along the way, of course.)
This ambitious plan begins with water, which is plentiful in a type of space rock known as carbonaceous chondrites. Asteroid-derived water could do far more than simply slake astronauts’ thirst, mining advocates say; it could also help shield them from dangerous radiation and, when split into its constituent hydrogen and oxygen, allow voyaging spaceships to fill up their fuel tanks on the go.
The technology to detect and extract asteroid water is not particularly challenging or expensive to implement, Lewicki said. Scientific spacecraft routinely identify the substance on celestial bodies, and getting water out of an asteroid could simply involve bagging up the space rock and letting the sun heat it up.
Carbonaceous chondrites also commonly contain metals such as iron, nickel and cobalt, so targeting these asteroids could allow miners to start building things off Earth as well. That’s the logical next step beyond exploiting water, Lewicki said.
The “gold at the end of the rainbow,” he added, is the extraction and exploitation of platinum-group metals, which are rare here on Earth but are extremely important in the manufacture of electronics and other high-tech goods.
“Ultimately, what we want to do is create a space-based business that is an economic engine that really opens up space to the rest of the economy,” Lewicki said.
Developing off-Earth resources should have the effect of opening up the final frontier, he added.
“Every frontier that we’ve opened up on planet Earth has either been in the pursuit of resources, or we’ve been able to stay in that frontier because of the local resources that were available to us,” Lewicki said. “There’s no reason to think that space will be any different.”
Planetary Resources isn’t mining asteroids yet, but it does have some hardware in space. The company’s Arkyd-3R cubesat deployed into Earth orbit from the International Space Station last month, embarking on a 90-day mission to test avionics, software and other key technology.
Incidentally, the “R” in “Arkyd-3R” stands for “reflight.” The first version of the probe was destroyed when Orbital ATK’s Antares rocket exploded in October 2014; the 3R made it to the space station aboard SpaceX’s robotic Dragon cargo capsule in April. [Antares Rocket Explosion in Pictures]
Planetary Resources is now working on its next spacecraft, which is a 6U cubesat called Arkyd-6. (One “U,” or “unit,” is the basic cubesat building block — a cube measuring 4 inches, or 10 centimeters, on a side. The Arkyd-3R is a 3U cubesat.)
The Arkyd-6, which is scheduled to launch to orbit in December aboard SpaceX’s Falcon 9 rocket, features advanced avionics and electronics, as well as a “selfie cam” that was funded by a wildly successful Kickstarter project several years ago. The cubesat will also carry an instrument designed to detect water and water-bearing minerals, Lewicki said.
The next step is the Arkyd 100, which is twice as big as the Arkyd-6 and will hunt for potential mining targets from low-Earth orbit. Planetary Resources aims to launch the Arkyd-100 in late 2016, Lewicki said.
After the Arkyd 100 will come the Arkyd 200 and Arkyd 300 probes. These latter two spacecraft, also known as “interceptors” and “rendezvous prospectors,” respectively, will be capable of performing up-close inspections of promising near-Earth asteroids in deep space.
If all goes according to plan, the first Arkyd 200 will launch to Earth orbit for testing in 2017 or 2018, and an Arkyd 300 will launch toward a target asteroid — which has yet to be selected — by late 2018 or early 2019, Lewicki said.
“It is an ambitious schedule,” he said. But such rapid progress is feasible, he added, because each new entrant in the Arkyd series builds off technology that has already been demonstrated — and because Planetary Resources is building almost everything in-house.
“When something doesn’t work so well, we don’t have a vendor to blame — we have ourselves,” Lewicki said. “But we also don’t have to work across a contractural interface and NDAs [non-disclosure agreements] and those sorts of things, so that we can really find a problem with a design within a week or two and fix it and move forward.”
For its part, Deep Space Industries is also designing and building spacecraft and aims to launch its first resource-harvesting mission before 2020, company representatives have said.
Extracting and selling asteroid resources is in full compliance with the Outer Space Treaty of 1967, Lewicki said.
But there’s still some confusion in the wider world about the nascent industry and the rights of its players, so he’s happy that the U.S. Congress is taking up the asteroid-mining issue. (The House of Representatives recently passed a bill recognizing asteroid miners’ property rights, and the Senate is currently considering the legislation as well.)
“I think it’s more of a protection issue than it is an actual legal issue,” Lewicki said. “From a lawyer’s interpretation, I think the landscape is clear enough. But from an international aspect, and some investors — I think they would like to see more certainty.”
The most comprehensive assessment of the energy output in the nearby universe reveals that today’s produced energy is only about half of what it was 2 billion years ago. A team of international scientists used several of the world’s most powerful telescopes to study the energy of the universe and concluded that the universe is slowly dying.
“We used as many space- and ground-based telescopes as we could get our hands on to measure the energy output of over 200,000 galaxies across as broad a wavelength range as possible,” Galaxy And Mass Assembly (GAMA) team leader Simon Driver, of the University of Western Australia, said in a statement. The astronomers created a video explaining the slow death of the universe to illustrate the discovery.
When the Big Bang created the energy of the universe about 13.8 billion years ago, some portion of that energy found itself locked up as mass. When stars shine, they are converting that mass back into energy, as described by Albert Einstein’s famous equation E=mc2 (energy = mass x speed of light squared). [From the Big Bang to Now in 10 Easy Steps]
“While most of the energy sloshing around in the universe arose in the aftermath of the Big Bang, additional energy is constantly being generated by stars as they fuse elements like hydrogen and helium together,” Driver said.
“This new energy is either absorbed by dust as it travels through the host galaxy, or escapes into intergalactic space and travels until it hits something, such as another star, a planet, or, very occasionally, a telescope mirror.”
Astronomers have known that the universe is slowly fading out since the late 1990s. Using several telescopes on the ground, as well as NASA’s orbiting GALEX and WISE and the European Space Agency’s Herschel, the team found that the energy output is dropping over 21 different wavelengths, making their results the most comprehensive assessment to date of the energy output of the nearby universe.
“The universe will decline from here on in, sliding gently into old age,” Driver said.
“The universe has basically sat down on the sofa, pulled up a blanket, and is about to nod off for an eternal doze,” he said.
Astronomers are constantly uncovering the “most distant,” “most massive” or “most energetic” objects in our universe, but today, researchers have announced the discovery of a truly monstrous structure consisting of a ring of galaxies around 5 billion light-years across.
The galactic ring, which was revealed by 9 gamma-ray bursts (GRBs), is located 7 billion light-years away and spans an area of the sky more than 70 times the diameter of a full moon.
GRBs are thought to be detonated when a massive star reaches the end of its life. As the star implodes after running out of fuel, a black hole is formed and vast quantities of energy are blasted in collimated beams. Should Earth be aligned with these beams, an incredibly luminous signal can be observed and these beacons can be used to precisely gauge the distance to the GRB and the location of the galaxy that hosts it.
The GRBs are all cataloged in the Gamma Ray Burst Online Index, which precisely records each GRB distance and location, like pins on a cosmic map.
Astronomers believe these GRBs (and therefore the galaxies they inhabit) are somehow associated as all 9 are located at a similar distance from Earth. According to its discoverers, there’s a 1-in-20,000 probability of the GRBs being in this distribution by chance — in other words, they are very likely associated with the same structure, a structure that, according to cosmological models, should not exist.
“If the ring represents a real spatial structure, then it has to be seen nearly face-on because of the small variations of GRB distances around the object’s center,” said Lajos Balazs, of Konkoly Observatory in Budapest, Hungary, and lead author of a paper published in the journal Monthly Notices of the Royal Astronomical Society. “The ring could though instead be a projection of a sphere, where the GRBs all occurred within a 250 million year period, a short timescale compared with the age of the universe.”
But what could possibly be creating a sphere an unprescedented 5 billion light-years across?
According to most cosmological models, the universe should have a roughly uniform distribution of matter over the largest scales. This is known as the “Cosmological Principal” and observations by NASA’s Wilkinson Microwave Anisotropy Probe (WMAP) and Europe’s Planck space telescope, which both studied the distribution of the universe’s ancient cosmic microwave background (CMB) radiation, seem to agree. However, other results have recently challenged this idea hinting that structures as large as 1.2 billion light-years may exist. But a growing list of discoveries in the cosmic abyss seem to contradict even the 1.2 billion light-year “limit.”
The GRB ring is 5 times larger than the 1.2 billion light-year limit; a pretty huge anomaly by anyone’s standard. And this latest discovery isn’t even the biggest. In 2013, another distribution of GRBs revealed a 10 billion light-year structure. Other large structures also defy this theoretical limit.
So what could be causing this particular ring of GRBs? One idea focuses around the large-scale structure of the universe where clusters of galaxies amass together in a web-like structure, thought to be clumped around concentrations of dark matter. The “holes” in this web are referred to as voids — regions of the cosmos that are conspicuously near-empty of any matter. The largest voids are called, unsurprisingly, “super-voids.”
But this new structure dwarfs all known super-voids.
“If we are right, this structure contradicts the current models of the universe. It was a huge surprise to find something this big — and we still don’t quite understand how it came to exist at all,” added Balazs.
So is the Cosmological Principal flawed? It’s certainly looking that way.
Galaxies are strung together in filaments separated by immense voids. These filaments are connected in a gargantuan tangle known as the cosmic web.
Much remains a mystery about how galaxies form. Researchers suggest that a key player is a kind of current known as a cold accretion flow. These rivers of gas can get as hot as 18,000 degrees Fahrenheit (10,000 degrees Celsius) — they are only “cold” relative to the kinds of extraordinarily hot winds astronomers regularly see in the universe, such as those around black holes.
One model suggests that, at the points where these filaments intersect, cold accretion flows streaming along the cosmic web’s filaments create disklike or ringlike structures, and that these “protogalactic disks” eventually coalesce into galaxies.
To learn more about how galaxies are born, scientists analyzed the first filament that astronomers ever imaged, a giant structure 1.5 million light-years long and 10 billion light-years away from Earth that was discovered in 2010.
This filament is about one-third as bright as the Milky Way, making it 3 billion times more luminous than the sun and more than 10 times brighter than what is expected for a filament. The filament is probably unusually radiant because it is illuminated by a quasar, the brightest type of object in the universe, researchers have said.
Using the Cosmic Web Imager at Palomar Observatory in California, the scientists discovered that the brightest spot in the filament is a spinning protogalactic disk of hydrogen.
“It is rare and surprising to discover a completely new kind of object,” said study lead author Christopher Martin, an astrophysicist at the California Institute of Technology in Pasadena.
The researchers found that this protogalactic disk is more than 407,000 light-years wide, weighs as much as about 100 billion suns, and is surrounded by a “halo” of invisible dark matter weighing as much as 10 trillion suns. For comparison, the Milky Way may be 160,000 light-years in diameter, and it weighs perhaps 1 trillion suns.
These findings reveal how cold accretion flows might help build protogalaxies — clouds of gas that give birth to galaxies, Martin said.
“It is extremely rare in astrophysics to be able to uncover the physical processes behind an observed phenomenon,” he told Space.com. “In this case, we will be able to study the processes that form the basic constituent of the universe, galaxies.”
In the future, Martin and his colleagues plan to find more protogalactic disks and study them with a larger telescope and better instruments.
“We are about to commission the perfect instrument for this — the Keck Cosmic Web Imager, which will be mounted at the Nasmyth focus of the W. M. Keck Observatory Keck II telescope [in Hawaii],” Martin said. “We plan to start observing at the beginning of 2016 with the Keck Cosmic Web Imager.”
The scientists detailed their findings online today (Aug. 5) in the journal Nature.
Talk about a starry night: A pair of university students in San Jose has found what appear to be the densest galaxies ever seen — cosmic realms where the night sky would appear ablaze with stars from the surface of a planet.
The students, Richard Vo and Michael Sandoval, discovered the so-called ultra-compact dwarf galaxies while sifting through open-source archives of astronomy observations by several different observatories as undergraduates at San Jose State University in California. They also created a video simulation depicting how such dense galaxies can form with a supermassive black hole at their core.
Looking up from a planet embedded inside one of the newfound galaxies, an observer would see more than a million stars at once, compared to the few thousand stars visible in Earth’s night sky, researchers explained. But the way these ultradense star clusters form, and whether they are actually galaxies at all, is still unknown.
“People have written sci-fi stories about things like this; it’s nice to see one that actually exists,” said Aaron Romanowsky, an astronomer at San Jose State University who served as the students’ adviser and co-author of the new study.
The first known ultracompact dwarf galaxy was found in 2013, surprising astronomers by having a supermassive black hole at its heart despite its small size. But the two newly discovered objects are even more tightly packed with stars. The first new object is about twice as dense as the original find, and the second object is a whopping 200 times denser than the original.
“This class of object was overlooked for a hundred years,” Romanowsky told Space.com. “It’s such a bright object, easy to see, but people didn’t know to look at it.” Romanowsky was also part of the team that found the first ultracompact dwarf galaxy two years ago. [A Tiny Dwarf Galaxy and Its Giant Black Hole (Video)]
In the past, such star clusters would have been mistaken for foreground stars because of their brightness. But when these clusters are examined more closely, the single point of light resolves into a fuzzy cluster, and spectrum data reveal it’s much farther away.
The width of one of the ultracompact dwarf galaxies, called M59-UCD3, is 200 times smaller than that of the Milky Way galaxy, but its star density is about 10,000 times higher. The other newfound galaxy, called M85-HCC1, has even more stars — its stellar density is 1 million times that of the Milky Way, and even led researchers to coin a new phrase for it: hypercompact cluster.
The students investigated data from the Sloan Digital Sky Survey, the Subaru Telescope in Hawaii, the Hubble Space Telescope, and the Southern Astrophysical Research Telescope in Chile. Although they intended to survey about one-third of the sky, each of them happened to discover an ultradense object not long after they began searching.
“It was a training procedure, actually,” said Vo, who is now a graduate student at San Francisco University in California. “He [Romanowsky] said, ‘There’s an ultracompact dwarf here; I want you to find it for yourself,’” Vo told Space.com.
But, in addition to the dwarf, he noticed another mysterious cluster. “And it ends up being one of the densest objects in the sky we have discovered so far,” Vo said.
The research is detailed in the July 20 edition of The Astrophysical Journal Letters.
Ultracompact dwarf galaxies have perplexed astronomers because they seem to defy classification. They’re too tiny to clearly be galaxies, but far too dense to be ordinary clusters of stars. [A Zoo of Galaxies in Infrared (Images)]
“For decades, a hundred years, there was a pretty clear distinction — how do you know the difference between a human and an elephant?” Romanowsky said. “Now, we’re finding things that are halfway in between, and we don’t know what to call them … The word we use is ‘ultracompact dwarf,’ but it’s an intentionally ambiguous word.”
The first ultracompact dwarf — which previously held the title of densest galaxy — puzzled astronomers until they spotted a supermassive black hole at its core. That detail suggested that it might have been a large galaxy at some point, before losing most of its stars. Researchers suspect that close interaction with another galaxy, whose gravity stripped off stars as they passed one another, might have transformed a normal dwarf galaxy into a dense ultracompact dwarf.
Sandoval, now a graduate student at the University of Tennessee in Knoxville, put together the above video simulation to demonstrate that process.
“We all know, from a mechanics/theory perspective, how things interact in space, [but] it is still hard to visualize how it actually looks in physical space,” Sandoval told Space.com in an email. “My goal was to see how the theory of tidal stripping would look in physical space, to accurately represent it, and to hopefully start up a method of analyzing phenomena that we can’t actually ‘see’ happening with our own eyes.”
The simulation was about as accurate as Sandoval could get without a supercomputer, and it incorporated imagery others had created showing what it would be like to look around inside the system, he said.
Going forward, the researchers will be searching for telltale signs of this process happening in the newly discovered objects; they’ll look for a supermassive black hole in the center and further analyze disturbances in the “host” galaxies near the objects. Those disturbances suggest that the large galaxies recently consumed stars from the ultracompact dwarfs; heavy metals in the dwarfs also suggest their previous size, as heavy metals are often synthesized by larger galaxies.
Romanowsky said that understanding how these objects form will teach astronomers about the formation of modern galaxies and what happens when they go head-to-head.
“In astronomy, there’s so many discoveries still to be made,” he added. “We’re still in the exploration phase, and even undergraduates can still make discoveries.”
Planets can exist in multiple-star systems. Astronomers have even observed them. Take Kepler-47c, a planet five times the mass of the Earth, in a very Earth-like orbit. The only difference is instead of one star in the center of the system, it has two. So contact your local travel agent and you can recreate that iconic film moment — just don’t forget a space suit: Kepler-47c isn’t exactly capable of supporting life, since it’s most likely a gas giant.
Astronomers don’t know for sure just how common planets are around multiple-star systems. To be fair, we don’t know for sure just how common planets are anywhere, but they appear to be just this side of quite numerous: a hundred billion planets, with a few billion of them life-friendly, in the Milky Way alone.
But you just can’t plop planets down wherever you feel like it, especially when it comes to multiple-star systems. The problem, as usual, is gravity.
Drawn into gravity
We usually think of gravity as easy. Two things attract each other. Done. Drop something, it falls. Launch a rocket, it doesn’t. Sure there are tides, and don’t get near black holes, but this is the kind of stuff that dead folks with interesting wigs figured out a long time ago.
Gravity is indeed pretty easy, when it’s just two things interacting. One planet plus one star? You’re golden. It’s so easy you can even write down the mathematical solutions of the possible orbits. All sorts of stable configurations. But put in another star? Or a third? The situation gets…tricky. Orbital stability isn’t a given. And the math? Just look up a picture of Henri Poincare, one of the first people to try to tackle the problem of multiple objects orbiting together. Look into his eyes, and tell me that isn’t the face of a man who has stared into the depths of mathematical hell and barely survived with his sanity intact.
I’m not saying that it’s impossible: You may have noticed, if you are observant enough, that our own solar system contains more than two objects. Our system didn’t fall apart billions of years ago because there’s a hierarchy. In other words, each planet or moon or asteroid or whatever is dominated by one and only one other player.
For example, the Earth cares a lot about the gravitational pull of the sun, but not of Jupiter, and Jupiter feels likewise. The moon cares a lot about the Earth, but not the sun or Ceres. And so on. Every interaction is essentially one-to-one. Thus, all the planets get nice stable little orbits that can last for billions of years. If you broke this hierarchy, say, by shoving Jupiter into the inner system, or inflating it to be 10 times more massive, its gravity would start to compete with the sun’s, the hierarchy would be broken, and so would the solar system.
All this gravity business means that planets around multiple star systems have only a few orbital options if they intend to stick around. Most potential orbits are unstable: even the faintest stellar breeze could potentially knock them either out of the system altogether or crashing into another body. To make a system a long-term home, a planet has two choices: either ensure that the gravitational pull of one star completely dominates the other, or that their gravitational effects are equal.
And that’s just for a binary star. Don’t get me started on multiples.
When two stars dance
Take Kepler-47c: the two stars orbit each other very closely and tightly , and the planet itself is rather far out. Far enough, in fact, that gravitywise the planet doesn’t even care that there’s two stars — to the planet, the center of the system just looks like a single star with the combined mass of the two suns. Stability achieved.
Another possible configuration is for a planet to only orbit a single star, with the other star far enough away and/or small enough to not matter. Figure-eight patterns around both stars are technically possible, but come on, don’t hold your breath looking for one. Truly chaotic orbits — stable, but never repeating the same pattern twice — would be extremely rare, too, as fun as they might be.
So we can get planets in a binary system, although they might be more rare than planets around solitary stars. But there are heaps of binary stars out there, so even if a tiny percentage of them host planets, that still leaves heaps of planets.
Life on around a binary-star system
What does this mean for such a planet’s weather and the prospects for life? That’s a little more difficult to say, since it’s hard to make general, broad-brush statements about the possibility of life anywhere, let alone in these kinds of binary systems. Instead, it’s best to examine each system (real or imagined) in detail.
While binary systems certainly have a habitable zone, where liquid water could potentially exist on the surface of a planet, life might find it difficult to gain a foothold. Orbiting two stars at once, as our friend Kepler-47c does, makes life very elliptical, occasionally bringing the planet out of the zone. Life doesn’t take too kindly to frequently freezing over.
Orbiting just one star in a binary system? Well, sometimes you’ll have two stars in your sky at once, which can be a tad toasty. And sometimes you’ll have a star on each face of the planet, ruining the night. And don’t forget the double-doses of UV radiation and solar flares.
With that kind of instability, erraticism and irradiation, it’s hard to imagine complex life evolving with the kind of regularity it needs. But thankfully, Mother Nature isn’t limited by our lack of imagination, so who knows what’s out there!
Learn more by listening to the episode “Is Life Possible Around a Binary Star?” on the Ask A Spaceman podcast, available on iTunes and on the Web at http://www.askaspaceman.com. Thanks to Adam Diener for the great question! Ask yours on Twitter using #AskASpaceman or by following @PaulMattSutter.
In the new image, researchers were able to make out the glow of ionized carbon (shown in red) in the process of assembling into a galaxy — called BDF 3299 — around 800 million years after the Big Bang. The carbon cloud is overlaid on another picture of the galaxy’s neighborhood, where you can tell the galaxy itself is off to the right. Researchers think that carbon’s glow is obscured by the supernova blasts and chaos of galactic formation there, but the cold store of carbon nearby still shines as the galaxy draws from it.
The image was captured by the Atacama Large Millimeter/submillimeter Array (ALMA), a giant radio telescope in Chile consisting of 66 radio antennas, most 40 feet (12 meters) in diameter.
“This is the most distant detection ever of this kind of emission from a ‘normal’ galaxy, seen less than one billion years after the Big Bang,” Andrea Ferrara, a cosmologist and co-author of the study from Scuola Normale Superiore, a part of the Pisa University System in Italy, said in a statement. “It gives us the opportunity to watch the build-up of the first galaxies. For the first time we are seeing early galaxies not merely as tiny blobs, but as objects with internal structure!”
BDF 3299 was among the first galaxies to condense out of cold matter during the galaxy’s reionization phase. Seeing the crooked galaxy’s formation offers a chance to refine models of the very early universe.
“We have been trying to understand the interstellar medium and the formation of the reionisation sources for many years,” Ferrara said. “Finally, to be able to test predictions and hypotheses on real data from ALMA is an exciting moment and opens up a new set of questions. This type of observation will clarify many of the thorny problems we have with the formation of the first stars and galaxies in the Universe.”
The black hole orbits in tandem with a sunlike star at the heart of the system V404 Cygni, which lies about 8,000 light-years from Earth. Swift spotted an outburst of activity from the black hole on June 15, and the spacecraft’s X-ray Telescope detected the expanding rings during observations made in late June and early July, NASA officials said.
The black hole is easy to see in the new images without the rings pointing the way; it appears as a bluish-white dot. But the bull’s-eye really marks the spot of the invisible interstellar dust between Earth and the system.
The various layers of dust, which are found between 4,000 and 7,000 light-years from Earth, reflect some of the X-rays over toward us as they fan out in all directions from the black hole.
“The flexible planning of Swift observations has given us the best dust-scattered X-ray ring images ever seen,” Andrew Beardmore, an astronomer at the University of Leicester in England and leader of the investigating team, said in a statement. “With these observations, we can make a detailed study of the normally invisible interstellar dust in the direction of the black hole.”
V404 Cygni’s arousal on June 15 was likely caused by material falling into the black hole, part of a cycle that repeats every few decades, researchers said. The companion star is about 10 percent as massive as the black hole, and the behemoth pulls a stream of gas away from it over time. The cool gas can resist the black hole’s pull, but when enough gas builds up and heats up, it’s suddenly pulled into the center of the black hole, triggering a sudden outburst of X-rays. Astronomers caught its most recent eruption before this one in 1989.
The outburst offers a rare opportunity to gather data about the nearby binary system, the black hole within it and the normally undetectable interstellar dust clouds that stand in its way, NASA officials said.