There are some things in the universe that you simply can’t escape. Death. Taxes. Black holes. If you time it right, you can even experience all three at once.
Black holes are made out to be uncompromising monsters, roaming the galaxies, voraciously consuming anything in their path. And their name is rightly deserved: once you fall in, once you cross the terminator line of the event horizon, you don’t come out. Not even light can escape their clutches.
But in movies, the scary monster has a weakness, and if black holes are the galactic monsters, then surely they have a vulnerability. Right?
Black holes are strange regions where gravity is strong enough to bend light, warp space and distort time.
In the 1970s, theoretical physicist Stephen Hawking made a remarkable discovery buried under the complex mathematical intersection of gravity and quantum mechanics: Black holes glow, ever so slightly, and, given enough time, they eventually dissolve.
Wow! Fantastic news! The monster can be slain! But how? How does this so-called Hawking Radiation work?
Well, general relativity is a super-complicated mathematical theory. Quantum mechanics is just as complicated. It’s a little unsatisfying to respond to “How?” with “A bunch of math,” so here’s the standard explanation: the vacuum of space is filled with virtual particles, little effervescent pairs of particles that pop into and out of existence, stealing some energy from the vacuum to exist for the briefest of moments, only to collide with each other and return to nothingness.
Every once in a while, a pair of these particles pops into existence near an event horizon, with one partner falling in and the other free to escape. Unable to collide and evaporate, the escapee goes on its merry way as a normal non-virtual particle.
Voila: The black hole appears to glow, and in doing so — in doing the work to separate a virtual particle pair and promote one of them into normal status — the black hole gives up some of its own mass. Subtly, slowly, over the eons, black holes dissolve. Not so black anymore, huh?
Here’s the thing: I don’t find that answer especially satisfying, either. For one, it has absolutely nothing to do with Hawking’s original 1974 paper, and for another, it’s just a bunch of jargon words that fill up a couple of paragraphs but don’t really go a long way to explaining this behavior. It’s not necessarily wrong, just…incomplete.
First things first: “Virtual particles” are neither virtual nor particles. In quantum field theory — our modern conception of the way particles and forces work — every kind of particle is associated with a field that permeates all of space-time. These fields aren’t just simple bookkeeping devices. They are active and alive. In fact, they’re more important than particles themselves. You can think of particles as simply excitations — or “vibrations” or “pinched-off bits,” depending on your mood — of the underlying field.
Sometimes the fields start wiggling, and those wiggles travel from one place to another. That’s what we call a “particle.” When the electron field wiggles, we get an electron. When the electromagnetic field wiggles, we get a photon. You get the idea.
Sometimes, however, those wiggles don’t really go anywhere. They fizzle out before they get to do something interesting. Space-time is full of the constantly fizzling fields.
What does this have to do with black holes? Well, when one forms, some of the fizzling quantum fields can get trapped — some permanently, appearing unfortunately within the newfound event horizon. Fields that fizzled near the event horizon end up surviving and escaping. But due to the intense gravitational time dilation near the black hole, thy appear to come out much, much later in the future.
In their complex interaction and partial entrapment with the newly forming black hole, the temporary fizzling fields get “promoted” to become normal everyday ripples — in other words, particles.
So, Hawking Radiation isn’t so much about particles opposing into existence near a present-day black hole, but the result of a complex interaction at the birth of a black hole that persists until today.
One way or the other, as far as we can tell, black holes do dissolve. I emphasize the “as far as we can tell” bit because, like I said at the beginning, generality is all sorts of hard, and quantum field theory is a beast. Put the two together and there’s bound to be some mathematical misunderstanding.
But with that caveat, we can still look at the numbers, and those numbers tell us we don’t have to worry about black holes dying anytime soon. A black hole with the mass of the sun will last a wizened 10^67 years. Considering that the current age of our universe is a paltry 13.8 times 10^9 years, that’s a good amount of time. But if you happened to turn the Eiffel Tower into a black hole, it would evaporate in only about a day. I don’t know why you would, but there you go.
A giant blob of gas and dust far off in the universe mysteriously glows bright green, and astronomers have finally figured out why. Two huge galaxies were observed in the blob’s core, and they’re surrounded by a swarm of smaller galaxies in what appears to be the birth of a massive cluster of galaxies.
Astronomers spotted the blob’s central galaxies using the Atacama Large Millimeter/submillimeter Array (ALMA) and the Very Large Telescope at the European Southern Observatory in Chile. The glowing space blob was first discovered in 2000, and the source of its light has been a mystery ever since.
One study published in 2011 suggested that polarized light emitted by the blob could have come from hidden galaxies. The new observations with ALMA and VLT allowed researchers to pinpoint two big galaxies as the sources of this light.
Further observations by the Hubble Space Telescope and the Keck Observatory in Hawaii revealed the swarm of small, faint galaxies surrounding the bigger two in the heart of the blob. Here, galaxies are forming stars at 100 times the rate of the Milky Way.
A giant green “space blob” – called the Lyman-alpha blob LAB-1 – is seen in this composite of two different images taken by the Very Large Telescope in Chile. The LAB-1 space blob is 300,000 light-years across, making it one of the largest known single objects in the universe.
Credit: ESO/M. Hayes
“For a long time, the origin of the extended Lyman-alpha light has been controversial,” Jim Geach, the study’s lead author, said in a statement. “But with the combination of new observations and cutting-edge simulations, we think we have solved a 15-year-old mystery.”
So-called “Lyman-alpha blobs” are some of the biggest things in space. This particular space blob, named SSA22-Lyman-alpha Blob 1 (LAB-1), is the largest of its kind. It measures about 300,000 light-years across, or three times the size of the Milky Way galaxy.
LAB-1 is located 11.5 billion light-years from Earth, so the light we observe from it is almost as old as the universe (13.8 billion years). This means that looking at LAB-1 provides a window into the early history of the universe.
Lyman-alpha blobs consist mainly of hydrogen gas and emit a particular wavelength of ultraviolet light called Lyman-alpha radiation. The light looks green to viewers on Earth, because its wavelength is stretched by the expanding universe during its long trip here.
This is a snapshot from a computer simulation of the evolution of a Lyman-alpha Blob similar to LAB-1. Gas within the dark matter halo is color- coded so that cold gas (mainly hydrogen) appears red and hot gas appears white. At the center of this system are two star-forming galaxies surrounded by hot gas and many smaller satellite galaxies that appear as small red clumps.
Once they had observed the sources of light from within the blob, the researchers created simulations of galaxy formation using NASA’s Pleiades supercomputer. They wanted to show that ultraviolet light — a byproduct of star formation — scatters off hydrogen gas to create a bright, glowing mega-blob like LAB-1.
“Think of a streetlight on a foggy night — you see the diffuse glow because light is scattering off the tiny water droplets,” Geach said in the same statement. “A similar thing is happening here, except the streetlight is an intensely star-forming galaxy and the fog is a huge cloud of intergalactic gas. The galaxies are illuminating their surroundings.”
The simulations also track gas and dark matter in the blob as it evolves into a galaxy. “Lyman-alpha Blob-1 is the site of formation of a massive elliptical galaxy that will one day be the heart of a giant cluster,” Geach added
Monster black holes can be millions of times more massive than the sun. If a star happens to wander too close, the black hole’s extreme gravitational forces can tear the star into shreds, in an event called “stellar tidal disruption.”
This kind of stellar destruction may also spit out a bright flare of energy in the form of ultraviolet and X-ray light. The two new studies examine how surrounding dust absorbs and re-emits the light from those flares, like a cosmic echo, according to a statement from NASA’s Jet Propulsion Laboratory (JPL).
“This is the first time we have clearly seen the infrared-light echoes from multiple tidal disruption events,” Sjoert van Velzen, a postdoctoral fellow at Johns Hopkins University and lead author of one study, said in the statement.
The new studies use data from NASA’s Wide-field Infrared Survey Explorer (WISE). The NASA study led by van Velzen used these “echoes” to identify three black holes in the act of devouring stars. The second study, led by Ning Jiang, a postdoctoral researcher at the University of Science and Technology of China, identified a potential fourth light echo.
Flares emitted from stellar tidal disruptions are extremely energetic and “destroy any dust” that is within the immediate neighborhood, according to NASA. However, a patchy, spherical web of dust that resides a few trillion miles (half a light-year) from the black hole can survive the flare and absorb light released from the star being gobbled up
“The black hole has destroyed everything between itself and this dust shell,” van Velzen said in the statement. “It’s as though the black hole has cleaned its room by throwing flames.”
The absorbed light heats the more distant dust, which in turn gives off infrared radiation that the WISE instrument can measure. These emissions can be detected for up to a year after the flare is at its brightest, the statement said. Scientists are able to characterize and locate the dust by measuring the delay between the original light flare and the subsequent echoes, according to the NASA study, which will be published in the Astrophysical Journal.
“Our study confirms that the dust is there, and that we can use it to determine how much energy was generated in the destruction of the star,” Varoujan Gorjian, an astronomer at JPL and co-author of the paper led by van Velzen, said in the statement.
Many supermassive black holes in the centers of galaxies possess a thick ring of material known as a torus. Appearing like a supersized doughnut, astronomers have long thought that these features were created by churned-up material from the galactic core itself, falling into the black hole’s gravitational well.
However, according to powerful new observations by the the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, this conventional model is, apparently, far too simple.
While studying the environment surrounding the supermassive black hole in the core of the barred spiral galaxy NGC 1068 47 million light-years away, ALMA was able to track clouds of material being flung outwards by the black hole, creating its own torus rather than material falling in.
WATCH VIDEO: The Race To See The Black Hole At Our Galaxy’s Core
“Think of a black hole as an engine,” said astronomer Jack Gallimore, of Bucknell University in Lewisburg, Pennsylvania, in a statement. “It’s fueled by material falling in on it from a flattened disk of dust and gas. But like any engine, a black hole can also emit exhaust.”
Black holes consuming matter possess accretion disks, which are basically flat and hot features that swirl around the black hole’s event horizon. The innermost section of the accretion disk is so hot that it generates X-ray and ultraviolet radiation, but further out, the disk is cooler and emits infrared and millimeter wavelength radiation. ALMA is very sensitive to the latter, allowing the observatory to track the motion of the gases in the outermost portion of NGC 1068’s accretion disk.
The torus of material harboring the supermassive black hole is highlighted in the pullout box. This region, which is approximately 40 light-years across, is the result of material flung out of the black hole’s accretion disk.
While following cool clouds of carbon monoxide gas inside this cooler accretion disk region, Gallimore’s team saw the clouds lift off the disk. As they become ionized by the superheated portion of the accretion disk, the clouds started to interact with the black hole’s powerful magnetic field. The gas was then flung away from the accretion disk at high speed, far faster than the rotational speed of the disk itself.
“These clouds are traveling so fast that they reach ‘escape velocity’ and are jettisoned in a cone-like spray from both sides of the disk,” said Gallimore. “With ALMA, we can for the first time see that it is the gas that is thrown out that hides the black hole, not the gas falling in.”
The vast majority of galaxies are known to contain supermassive black holes in their cores. They have a symbiotic relationship and the activity of black holes are known to have a powerful influence over the galaxies as a whole, even impacting the rate of star formation. Now, with observatories like ALMA, we’re beginning to see the intricacies of this relationship and their impact on the hearts of galaxies.
A star’s mysterious evolution recently came to light using the Hubble Space Telescope, which spotted the star cooling after a rapid temperature increase in the past. Th find is all the more extraordinary given that this sort of process usually exceeds a human lifetime, according to astronomers.
The researchers explained the process behind the rebirth of the star (called SAO 244567) in this new animation.
“SAO 244567 is one of the rare examples of a star that allows us to witness stellar evolution in real time,” Nicole Reindl, a postdoctoral researcher from the University of Leicester in the U.K. who led the study, said in a statement. “Over only 20 years the star has doubled its temperature, and it was possible to watch the star ionizing its previously ejected envelope [of dust and gas], which is now known as the Stingray Nebula.”
Astronomers have seen many changes in the star, which is 7,000 light-years from Earth, in the past 45 years. Between 1971 and 2002, they saw the surface temperature of the star increase by almost 72,000 degrees Fahrenheit (40,000 degrees Celsius). But the new observations with Hubble’s cosmic origins spectrograph reveal that the star is cooling and expanding.
In 2014, Reindl’s team proposed that SAO 244567 — whose low mass makes it hard to explain the rapid temperature fluctuations — may have just undergone a “helium-shell flash event,” which happens when helium briefly ignites outside the heart, or core, of the star. Once the heating flash completes, SAO 244567 should regress in its evolution and cool. The new observations suggest this 2014 theory was correct, Reindl said in the same statement.
“The release of nuclear energy by the flash forces the already very compact star to expand back to giant dimensions — the born-again scenario,” Reindl said.
She added that the team will need to refine their calculations to better explain SAO 244567’s behavior, which can’t be accounted for in current models of star evolution.
Hundreds of black holes could be lurking inside a cluster of stars that orbits the Milky Way galaxy, a new study shows.
NGC 6101 is a globular cluster (a dense, spherical collection of ancient stars) orbiting the center of the Milky Way. Using computer models, scientists recently showed that some strange characteristics of NGC 6101 could be explained by the presence of hundreds of black holes — something scientists have never observed in a globular cluster.
Black holes can form when massive stars die in a fiery explosion called a supernova. This type of blast is thought to kick the black hole away from its birth site, according to Mark Gieles, a professor of astrophysics at the University of Surrey in England and one of the authors of the new study. But the existence of so many black holes within the globular cluster would suggest that these “kicks” are not as powerful as scientists previously thought, Gieles said in a video detailing the new work.
Finding black holes is difficult, because astronomers can’t see them the same way they can see stars and other objects in the universe. That’s because black holes are so dense that not even light can escape the pull of their gravity.
While black holes may be difficult to spot, computer simulations can help predict where they might be hiding. Gieles and colleagues at the University of Surrey were inspired to create simulations of NGC 6101 after another group published their observations of the cluster last year.
The cluster’s structure didn’t make sense at first. Usually, in globular clusters, heavy stars move to the center, while lightweight stars tend to migrate to the periphery — a process known as “mass segregation.” But NGC 6101 has very few stars near its center. “We found that this is not at all what you would expect for a normal stellar system,” Gieles said in the video about the study.
“It reminded us of previous work where we looked at the influence black holes can have on globular clusters, and we had the idea, ‘Maybe we could explain it by simply putting some black holes into the cluster,'” Miklos Peuten, a Ph.D student in astrophysics at the University of Surrey and lead author of the research paper, said in the same video.
To make sense of the missing mass segregation, the team recreated the entire 13-billion-year evolution of the cluster. Without black holes, the simulation didn’t match their real observations of the system. But once they threw black holes into the mix, their simulations matched their observations perfectly. Black holes could be the missing piece of the NGC 6101 puzzle.
“The next step would be to look at other globular clusters which also have strange profiles” and see if black holes can explain those as well, Peuten said in the video, adding that this “would help us to understand how black holes are created and how black holes evolve.”
The star, located almost 11,000 light-years from Earth, has a mass 30 times that of the sun, and it’s still growing. Astronomers found that this star is still in the process of collecting material from its parent cloud of gas and dust, which means it is only a baby in cosmic terms and is expected to be even more massive by the time it grows up, according to a statement from the University of Cambridge, where the research was conducted. A young star such as this is also known as a protostar.
Due to their incredibly large size, protostars such as this are difficult to locate in Earth’s galaxy (the Milky Way) and are hard to study because they live fast and die young and are generally very far away.
“An average star like our sun is formed over a few million years, whereas massive stars are formed orders of magnitude faster — around 100,000 years,” John Ilee, lead author of the study from Cambridge’s Institute of Astronomy, said in the statement. “These massive stars also burn through their fuel much more quickly, so they have shorter overall life spans, making them harder to catch when they are infants.”
But the astronomers behind the new work were able to do just that: catch the star during a key stage of its birth. Their findings revealed that massive stellar bodies like this form from rotating discs of gas and dust, also known as the stars’ parent clouds. This process is very similar to the way that much smaller stars like Earth’s sun form, astronomers said in the statement.
Using the Submillimeter Array (SMA) in Hawaii and the Karl G. Jansky Very Large Array (VLA) in New Mexico, the astronomers found that the new protostar lives in an infrared dark cloud, which is an ideal region for star formation because it is very cold and dense.
With thick surrounding clouds of gas and dust, these areas are generally difficult to observe using telescopes. However, the astronomers were able to peer through the clouds and measure the radiation emitted from the dust around the star and its chemical signatures. Their findings revealed the presence of a “Keplerian” disc that’s rotating more quickly at its center.
“This type of rotation is also seen in the solar system — the inner planets rotate around the sun more quickly than the outer planets,” Ilee explained. “It’s exciting to find such a disc around a massive young star, because it suggests that massive stars form in a similar way to lower-mass stars, like our sun.”
The new findings were published Aug. 9 in the Monthly Notices of the Royal Astronomical Society.
Are black holes truly black? A new laboratory experiment points toward “no.”
Using a simulated black hole made from soundwaves, scientists have observed a phenomenon known as Hawking radiation: a faint energy emission that, in theory, is created right at the edge of a black hole’s event horizon, or the point beyond which even light cannot escape.
If Hawking radiation comes from astrophysical black holes (not just those created in a lab), it would mean these objects are not entirely dark. It could also help scientists solve a paradox posed by black holes, and perhaps shed light on one of the most significant problems facing modern physics.
Black holes are strange regions where gravity is strong enough to bend light, warp space and distort time
Jeff Steinhauer, an experimental physicist at the Technion — Israel Institute of Technology in Israel, and lead author on the new study, told Space.com.
According to Steinhauer, earlier calculations by cosmologist Stephen Hawking (who came up with the theory that bears his name) combined the theories of quantum physics and gravity. The current experiment tests those calculations, providing the first strong evidence that they are correct, Steinhauer said.
“A black hole is a testing ground for the laws of physics,” Steinhauer said.
Swimming against the current
There’s a tricky concept in physics that says that pairs of particles constantly blink into existence throughout space. One is a particle of normal matter and the other is its exact opposite, or antiparticle, so the two annihilate one another, and there’s no change to the universe’s energy balance sheet. These are called virtual particles. When this happens near the edge, or event horizon, of a black hole, the particles can avoid complete destruction; one can fall inside while the other escapes.
But observing such interactions in nature has remained difficult, the Hawking radiation around a black hole (if it exists) is so faint that it can’t be seen from Earth around known black holes (most of which are very far away). In addition to the distance, the Hawking radiation is likely overwhelmed by radiation from other sources, Steinhauer said.
“It makes it seemingly almost impossible to see this very slight radiation coming from the black hole,” he said.
The same problem applies in a laboratory, where any heat can create background radiation that overwhelms the lab-produced Hawking radiation. To eliminate that problem, Steinhauer’s experiment ran at less than a billionth of a degree above absolute zero.
In the analogue black hole, a line of cold rubidium atoms stream from a laser to create a form of matter known as a Bose-Einstein condensate. The cold gas flows faster than the speed of sound in one direction, so that a sound wave trying to go against the flow can’t manage to move forward. In this respect, the slower moving sound wave is like a particle trying to escape from a black hole.
“It’s like trying to swim against the river,” Steinhauer said. “If the river is going faster than you can swim, you go backwards, even though you feel like you’re going forward.”
The upstream attempt is analogous to light in a black hole trying to escape, he said. Sound waves trying to move forward instead fall backward. If two virtual particles were created near the edge of the event horizon, one particle could be consumed by the black hole (the fast-moving stream), while the other escapes, avoiding destruction. The escaping particles are called Hawking radiation.
A method of creating a black hole using sound waves was proposed in 1981, and since then scientists have struggled to simulate Hawking radiation in the lab. Two years ago, Steinhauer performed an experiment that measured Hawking radiation after something was deliberately crashed into the event horizon of the analogue black hole. This new experiment took more of a wait-and-see stance, waiting for the particle-antiparticle pair to appear without external stimulation, more like what happens in the depths of space.
Just as Hawking theorized, the simulated black hole spit out the predicted particles, a sign of Hawking radiation.
“What I saw suggests that a real black hole might emit something,” Steinhauer said.
The new finding also has larger implications for the field of physics, he said. One of the biggest mysteries in physics is why Einstein’s theory of gravity (which describes large-scale interactions in the universe) doesn’t seem to be compatible with quantum mechanics (which describes very small-scale interactions).
“Combining gravity with quantum physics is one of the main goals of physics today,” Steinhauer said. “Hawking made the first steps toward that.”
The simulated black hole tested Hawking’s equations.
“His calculations predicted there should be light from a black hole,” Steinhauer said. “It turns out his calculations were correct.”
One intriguing result of the artificial black hole involved insight into the information paradox. According to Einstein’s theory of general relativity, everything that crosses the event horizon of a black hole is consumed, including information. As the escaping particle steals energy from a black hole, the massive object can shrink over time, eventually evaporating into nothing. Of course, this assumes it has stopped consuming nearby material and thus isn’t putting on new weight. Theoretically, a black hole can shrink into nothing, taking with it the information carried by or about the particles it consumed.
“Information has vanished,” he said. “It’s like it goes into the black hole and disappears.”
Since quantum mechanics suggests that information can’t be lost, that raises a paradox.
According to Hawking’s calculations, the surviving particles contain no useful information about how the black hole formed and what it consumed, suggesting that information vanished with the black hole itself.
Steinhauer’s black hole revealed that the higher energy particle pairs remained entangled, even after one was swallowed by the event horizon. Entangled particles are able to share information instantaneously, even when they are separated by great distances, a phenomenon sometimes described as “spooky action at a distance.”
“Some of the solutions to this [paradox] probably rely on entanglement,” Steinhauer said.
Scientists not associated with the research who were interviewed by Nature News and Physics World both said that while the experiment appears to have measured Hawking radiation, it does not necessarily prove that Hawking radiation exists around black holes in space.
This research suggests that Ceres might still be warmed by radioactive material in its interior, scientists say.
With a diameter of about 585 miles (940 kilometers), Ceres is by far the biggest member of the asteroid belt located between Mars and Jupiter. Previous remote analysis of Ceres using ground- and space-based telescopes suggested that it was not as dense as other large asteroids such as Vesta. This suggested that Ceres was not made up solely of rock, but composed partly of both icy and rocky material.
However, scientists weren’t sure how the innards of Ceres were structured. Whereas Earth developed an onion-like structure fully differentiated into distinct layers — an outer crust, a central core and a mantle layer between the two — prior research suggested that Ceres might only be partially differentiated into more vague zones, or perhaps not differentiated at all. Shedding light on the structure of Ceres might, in turn, yield insight into how it and other asteroids and dwarf planets evolved over time.
One property of Ceres that might reveal more about its structure is how easy or difficult it is for the dwarf planet to spin. This property, technically known as the moment of inertia, is related to how mass is distributed within a celestial body: The lower the moment of inertia, the more dense material is concentrated in a body’s center.
To determine the moment of inertia of Ceres, scientists needed to analyze the dwarf planet’s gravity field. Anything that has mass has a gravity field that attracts objects toward it, and the strength of this field depends on a body’s mass. Because the mass of bodies such as Earth and Ceres is not spread out evenly, this means their gravity fields are stronger in some places on their surfaces and weaker in others.
The researchers examined gravity-field data that NASA’s Dawn spacecraft gathered from its close encounter with Ceres. Their work suggests that Ceres is only partially differentiated, with a core made of rock overlaid by a shell composed of a mix of icy, salty and rocky material that is about 43.5 to 120 miles (70 to 190 km) thick.
“The partial differentiation suggests that Ceres was hot at one point, but it did not fully separate the water and other volatiles from its rocky components,” study lead author Ryan Park, a planetary scientist at NASA’s Jet Propulsion Laboratory in Pasadena, California, told Space.com.
The scientists also detected signs that Ceres’ interior might still be warm. This was a bit of a surprise, because previous research suggested that a body as small as Ceres should have cooled off a long time ago. This new finding indicates that Ceres might have a warm interior because of heat from radioactive material, Park said.
Two separate studies suggest that galactic radiation would quickly degrade biological material on the surface of Mars and Jupiter’s ocean-harboring moon Europa, two of the prime targets in the search for past or present extraterrestrial life.
Objects in the solar system are bathed in radiation from the sun and large planets such as Jupiter. But the largest doses come from galactic cosmic rays (GCRs), which stream in from faraway sources such as exploding stars.
Earth’s thick atmosphere protects life here from the damaging effects of GCRs. But life on other worlds would not be so lucky; modern Mars has a thin atmosphere, for example, and Europa has virtually no atmosphere at all. Both worlds therefore are bombarded by high levels of radiation, which could spell doom for any fossils that may have once existed on the worlds’ surfaces.
Mars is the most Earth-like world in the solar system. Scientists think Mars once harbored a large ocean of liquid water that the planet lost, along with its atmosphere, billions of years ago.
While scientists consider it unlikely that life exists at the Martian surface today, many researchers hope to find evidence that Martian life existed in the past. That evidence would come in the form of fossilized microorganisms or biological molecules such as amino acids, the building blocks of proteins.
But finding that evidence would require such molecules to persist on Mars or Europa. To check if this is likely, Alexander Pavlov, a planetary scientist at NASA’s Goddard Space Flight Center in Maryland, and his colleagues set out to test how amino acids withstand doses of radiation similar to those experienced at the Martian surface.
Previous studies that dosed only amino acids found they could survive for up to 1 billion years under Martian conditions. However, Pavlov’s team mixed the amino acids with rocky material similar to that found on Mars, generating conditions a rover is more likely to sample. The researchers found that the amino acids were degraded by radiation in as few as 50 million years.
“More than 80 percent of the amino acids are destroyed for dosages of 1 megagray, which is equivalent to 20 million years,” Pavlov said in March, during a presentation at the 47th Lunar and Planetary Science Conference in The Woodlands, Texas. “If we’re going for ancient biomarkers, that’s a very big problem.”
The scientists then combined the surface sample with water to simulate historically wet regions on Mars; these are the places considered most favorable to life. Water accelerated the degradation of the biomarkers, destroying some in as few as 500,000 years and all within 10 million years.
The odds of finding signs of life in hydrated minerals near the Martian surface therefore aren’t great, the researchers said.
Cold temperatures slow the degradation process down, but not enough for long-term preservation, the scientists said. Material lasted no more than 100 million years when exposed to Mars-like GRC levels.
These findings could be bad news for missions that plan to search for signs of ancient life on the Martian surface, the researchers said.
“We are extremely unlikely to find primitive amino acid molecules in the top 1 meter [3.3 feet] [of the crust], due to cosmic rays,” Pavlov said. “It would be critical to provide missions with 2-meter [6.6 m] drilling capabilities, or chose landing sights with freshly exposed rocks.”
Such rocks would have been kicked up from beneath the surface by asteroid or comet impacts within the last 10 million years, he said.
In 2020, the European Space Agency and Russia plan to launch a life-hunting Mars rover that can drill up to 2 meters down. The mission will be the second phase of the ExoMars mission; the first phase, which consists of an orbiter and a landing demonstrator, launched in March.
Jupiter’s moon Europa is considered one of the best places to search for life beyond Earth. A global ocean sloshes beneath the moon’s icy shell, fed by thermal vents that could possibly generate the energy needed for life to evolve.
NASA aims to launch a flyby mission to Europa in the 2020s, and the agency is considering adding a lander to the mission profile as well
Europa’s ice shell is thought to be miles thick on average, so a lander wouldn’t be able to drill through the ice (except perhaps in a few select spots). But signs of Europan life, if it exists, may rise up from the ocean onto the surface.
Indeed, Europa has reddish surface features that have been identified as salts, which likely came from beneath. Scientists have also tentatively identified, but not confirmed, plumes like those found on Saturn’s moon Enceladus, which could shoot water-rich material — and, possibly, signs of life — from the ocean to the surface.
Like Pavlov, Luis Teodoro, a planetary scientist at NASA’s Ames Research Center in California, was concerned with GCR radiation, and how dosages could affect the hunt for life. But Teodoro focused on Europa, not Mars.
Simulating the conditions at Europa, Teodoro found that the moon’s GCR dosages were comparable to those on the Red Planet.
“Radiation is going to play a major role at Europa in the top few meters — actually, dare I say, dozen meters — of Europa’s surface,” Teodoro said at the same conference.
He said his simulations suggest that hardy “extremophile” microbes found in some of Earth’s harshest environments would survive no more than 150,000 years in the top 3.3 feet (1 m) of Europa’s icy crust. Organic biomarkers buried within 3.3 feet of the surface would last only 1 to 2 million years, he said.
“If we want to put a landeron the surface of Europa to check if life is there, we most likely are going to see something destroyed — mangled materials, mainly organics — from this huge dosage of radiation,” he said.
There is hope, however, that fresh surface ice deposits could still contain biomarkers that scientists could successfully identify as life. So it’s important to determine if Europa does indeed spout plumes that bring fresh material to the surface, Teodoro said.
Europa also is exposed to another source of radiation that Earth and Mars avoid: the radiation from Jupiter. Teodoro said he plans to include the effects of Jupiter’s doses in future models.
For now, however, his research seems to suggest that hunting for existing life or fossils on the icy moon may remain a challenge. But Teodoro said he hasn’t given up completely on the cool world.
“Maybe this is all telling us life is not at the surface,” he said, expressing his hope that evidence of alien organisms instead lies beneath the ice.
The gas cloud, a nebula called LHA 120-N55, is about 163,000 light-years away from Earth and is situated in the Large Magellanic Cloud, a nearby dwarf galaxy that’s one of the Milky Way’s satellites. The image was taken by the VLT’s FOcal Reducer and low dispersion Spectrograph (FORS2), and its location in space is pinpointed in a new video.
The gaseous N55 is inside of a superbubble, a vast structure which occurs when winds from new stars and shockwaves from supernova explosions, caused by dying stars, blow away the gas and dust those stars used to possess. The process carves bubble-shaped holes in the gas.
Emission nebula LHA 120-N55 shines in this image from the European Southern Observatory’s Very Large Telescope.
ESO “The material that became N55, however, managed to survive as a small remnant pocket of gas and dust,” ESO officials said in a statement. “It is now a standalone nebula inside the superbubble and a grouping of brilliant blue and white stars — known as LH 72 — also managed to form hundreds of millions of years after the events that originally blew up the superbubble.”
Those brilliant stars are quite young — too young to have created the superbubble — but they are responsible for the bright colors in the image. Their radiation is stripping away electrons inside the hydrogen atoms of N55, which makes the gas glow; that vibrant glow is seen as an indication of new stars.
This region will see a lot of upheaval in a few million years, ESO officials added, when some of these young stars begin to go supernova. “In effect, a bubble will be blown within a superbubble, and the cycle of starry ends and beginnings will carry on in this close neighbour of our home galaxy,” they said.
Astronomers using NASA’s Hubble Space Telescope have discovered a moon orbiting Makemake, which is the second-brightest object in the distant Kuiper Belt beyond Neptune. (Pluto is the brightest of these bodies.)
The newfound satellite — the first ever spotted around Makemake — is 1,300 times fainter than the dwarf planet and is thought to be about 100 miles (160 kilometers) in diameter, researchers said. The moon was spotted 13,000 miles (20,900 km) from the surface of Makemake, which itself is 870 miles (1,400 km) wide. [See images of the dwarf planet Makemake]
“Makemake is in the class of rare Pluto-like objects, so finding a companion is important,” Alex Parker of the Southwest Research Institute (SwRI) in Boulder, Colorado, who led the image analysis for the Hubble observations, said in a statement today (April 26).
“The discovery of this moon has given us an opportunity to study Makemake in far greater detail than we ever would have been able to without the companion,” Parker added.
For example, further observations of the moon — which has been provisionally named S/2015 (136472) 1, and nicknamed MK 2 — should allow astronomers to calculate the density of Makemake, which should tell them if the dwarf planet and Pluto are made of similar stuff.
Additional Hubble observations should also reveal the shape of MK 2’s orbit around Makemake. If the orbit is tightly circular, the moon was probably created by a long-ago giant impact, just like the five satellites in the Pluto system were, researchers said. A looping, elliptical orbit, on the other hand, would suggest that MK 2 was once a free-flying Kuiper Belt object that Makemake captured.
The Hubble discovery images suggest that MK 2 is as dark as charcoal, which seems surprising given that Makemake is so bright. One possible explanation is that the moon’s gravity is too weak to hold onto reflective ices, which sublimate off MK 2’s surface into space, researchers said.
Makemake orbits the sun at an average distance of 45.7 astronomical units (AU) and completes one lap around the star every 309 Earth years. (One AU is the Earth-sun distance — about 93 million miles, or 150 million km.) The dwarf planet is even farther away than Pluto, which lies 39.5 AU from the sun on average and orbits once every 248 Earth years.
Makemake is one of five objects officially recognized as a dwarf planet by the International Astronomical Union (IAU). The others are the Kuiper Belt denizens Pluto, Eris and Haumea, and Ceres, which lies in the main asteroid belt between Mars and Jupiter.
Ceres is the only one of these five that doesn’t have at least one moon.
The IAU defines a dwarf planet as an object that orbits the sun and is massive enough to have been forced into a spherical shape by its own gravity but has not “cleared its neighborhood” of other orbiting material. (Pluto falls short on this last count, according to IAU officials, which is why the former ninth planet was reclassified as a dwarf planet in 2006.)
MK 2 was spotted in observations made by Hubble’s Wide Field Camera 3 in April 2015, after several previous Makemake observation campaigns had failed to turn up any satellites.
“Our preliminary estimates show that the moon’s orbit seems to be edge-on, and that means that often when you look at the system you are going to miss the moon because it gets lost in the bright glare of Makemake,” Parker said.
Supermassive black holes are the most extreme objects in the known universe, with masses millions or even billions of times the mass of our sun. Now astronomers have been able to study one of these behemoths inside a strange, distant quasar and they’ve made an astonishing discovery — it’s spinning one-third the speed of light.
Studying a supermassive black hole some 3.5 billion light-years away is no easy feat, but this isn’t a regular object: it’s a quasar that shows quasi-periodic brightening events every 12 years or so — a fact that has helped astronomers reveal its extreme nature.
Quasars are extremely bright accretion disks in galactic cores driven by copious quantities of matter falling into the central supermassive black hole. The vast majority of galaxies are thought to contain supermassive black holes, though modern galaxies have calmed down and quasars no longer shine. But it’s a different story for galaxies that are billions of light-years away.
The object at the center of the strange quasar called OJ287 “weighs in” at 18 billion solar masses and is one of the biggest supermassive (or ultramassive?) black holes in the known universe. Interestingly, it is also one of the most well-studied quasars as it is located very close to the apparent path of the sun’s motion across the sky as seen from Earth — a region where historic searches for asteroids and comets are regularly carried out. Therefore, astronomers have over 100 years of serendipitous brightness data for OJ287, allowing them to predict when the next flaring event would be.
On closer inspection of the flaring events that occurred in recent decades, astronomers realized that rather than a single brightening event occurring every 12 years, the brightening is actually a double peak, providing a clue as to what might be causing it. ANALYSIS: Black Holes Slug it Out in Quasar Deathmatch Mauri Valtonen of University of Turku, Finland, and his international team used several optical telescopes around the world in conjunction with NASA’s SWIFT X-ray space telescope to realize that these 12-year double-brightening events are triggered by a smaller black hole in orbit around OJ287.
Valtonen is the lead author of the study published in the Astrophysical Journal. The massive black hole possesses a very hot accretion disk, a key component of a quasar.
The material accumulates in the disk and gets pulled into the black hole, feeding it. Along the way, the disk material is heated and emits powerful electromagnetic radiation. OJ287’s smaller black hole partner, which itself is still 100 solar masses (still a huge black hole!) has a highly elongated orbit, swinging close to the more massive black hole every 12 years.
During closest approach, the smaller black hole “splashes” into OJ287’s accretion disk once during the incoming swing and once more as it swings around the black hole’s far side, creating 2 distinct flaring events, as this diagram demonstrates: An illustration of the binary black hole system in OJ287. The predictions of the model are verified by observations.
This periodic close encounter stirs up the supermassive black hole’s accretion disk material, rapidly heating it twice in rapid succession. This is what causes OJ287’s strange brightenings every 12 years. With this binary black hole model in mind, the researchers were able to predict when the latest event was due to occur.
The last brightening happened on Nov. 18, 2015, only a few days before Valtonen’s prediction, confirming his team’s binary black hole model. But through these observations, the supermassive black hole’s spin could also be calculated and it’s fast. The team’s observations show that it is spinning at a third of the speed of light. Interestingly, from the historical data of OJ287, the team was also able to calculate how much energy is being lost from the system via gravitational waves. Of course, gravitational waves are currently a very hot topic, having been directly detected for the first time by the US-based Laser Interferometer Gravitational-wave Observatory (LIGO) and announced last month.
That LIGO detection was the signature produced by 2 orbiting and merging black holes, a discovery that not only confirmed one of Einstein’s final predictions of general relativity, but also directly confirmed the existence of 2 black holes merging as one. ANALYSIS: We Just Heard the Spacetime ‘Chirp’ of Black Hole Rebirth Though the gravitational waves of the OJ287 black hole binary are too weak to be detected by the current generation of gravitational wave detectors (as the source is far too distant), the Nov. 18 brightening
This periodic close encounter stirs up the supermassive black hole’s accretion disk material, rapidly heating it twice in rapid succession. This is what causes OJ287’s strange brightenings every 12 years. With this binary black hole model in mind, the researchers were able to predict when the latest event was due to occur.
The last brightening happened on Nov. 18, 2015, only a few days before Valtonen’s prediction, confirming his team’s binary black hole model. But through these observations, the supermassive black hole’s spin could also be calculated and it’s fast. The team’s observations show that it is spinning at a third of the speed of light. Interestingly, from the historical data of OJ287, the team was also able to calculate how much energy is being lost from the system via gravitational waves. Of course, gravitational waves are currently a very hot topic, having been directly detected for the first time by the US-based Laser Interferometer Gravitational-wave Observatory (LIGO) and announced last month. That LIGO detection was the signature produced by 2 orbiting and merging black holes, a discovery that not only confirmed one of Einstein’s final predictions of general relativity, but also directly confirmed the existence of 2 black holes merging as one.
We Just Heard the Spacetime ‘Chirp’ of Black Hole Rebirth Though the gravitational waves of the OJ287 black hole binary are too weak to be detected by the current generation of gravitational wave detectors (as the source is far too distant), the Nov. 18 brightening of the quasar serves as a fitting celebration for Einstein’s theory that he presented almost exactly 100 years before on Nov. 25, 1915.
Infant stars may release bursts of light when they collide with and devour dense clumps of matter that otherwise might have gone on to form planets, new research suggests. The new finding has larger implications for understanding how stars grow and evolve early in their lives — specifically, that stars may grow through chaotic series of violent events, instead of steadily getting larger, as previously thought, the authors of the new work noted.
Stars coalesce from vast clouds of gas and dust, and planets emerge from whirling disks of leftover matter that surround newborn stars. Young stars that are still feeding on their parent clouds are known as protostars, while the disks of material that give rise to planets are known as protoplanetary disks.
Previous research often envisioned protostars growing in a simple manner, steadily accumulating or accreting fuel from surrounding clouds. However, protostars are often far dimmer than expected, given their estimated average rates of accretion. With the new finding, scientists now have evidence that protostars may evolve in an extremely chaotic way, sporadically accreting dense clumps of gas from their surrounding protoplanetary disks.
For the new work, astronomers focused on protostars known as FU Orionis objects. These young stars, also known as FUors, are known to experience dramatic spikes in brightness, the researchers said. Previous work suggested that FUors brightened because their accretion rates suddenly increased by a factor of 1,000 or more, and staying that way for decades or longer. To learn more about these outbursts, scientists used the Subaru Telescope, located at the Mauna Kea Observatories in Hawaii, to analyze four of the 11 confirmed FUors, located between 1,500 and 3,500 light-years from the Milky Way.
The new images of the flaring newborn stars “were surprising and fascinating, and nothing like anything previously observed around young stars,” representativesofthe National Institutes of Natural Sciences (NINS) in Japan said in a statement. (NINS is one of the managing institutions of the National Astronomical Observatory of Japan, where some of the paper’s authors are based.) The researchers discovered “tails” projecting from the protoplanetary material around the young stars, as well as spikes of gas and dust.
The researchers created computer simulations that suggested that the proto-planetary disks of newly formed stars could be gravitationally unstable and can fragment, creating dense clumps of gas that can collide with the stars, helping them grow and creating those bright bursts of light. “We suggest a previously unrecognized evolutionary stage in the formation of stars and protoplanetary disks,” study lead author Hauyu Baobab Liu, an astronomer at the Academia Sinica Institute of Astronomy and Astrophysics in Taipei, Taiwan, told Space.com.
These observations may reveal that clumps of gas and dust fall into the stars (helping them grow) in a more chaotic fashion than once thought. Credit: Science Advances, H. B. Liu This unstable phase of a protostar’s life might last several hundred thousand years, the scientists added. “Although more simulations are required to match the simulations to the observed images, these images show that this is a promising explanation for the nature of FU Ori[onis]outbursts,” NINS representatives said in the statement. The scientists detailed their findings online Feb. 5 in the journal Science Advances.
A powerful greenhouse effect can destroy a planet’s chances of hosting life, a new study suggests.
Until proven otherwise, scientists on Earth assume water is necessary for life to arise on other planets. In the search for life outside the solar system, scientists focus on a “habitable zone” around other stars. Inside such a habitable zone, Earth-like planets are neither too hot nor too cold for liquid water to exist on the surface.
A planet that orbits too close to its sun may become parched because of the solar heat. But now, scientists think an extreme greenhouse effect can also push a planet into dry conditions — similar to what happened on Venus.
The new research shows that warming due to carbon dioxide is as powerful as solar heat due to orbit when it comes to drying out a planet. The modeling study was published today (Feb. 9) in the journal Nature Communications.
“This is interesting because it tells you that you need to know more than just the position of a planet to know whether it might be habitable or not,” said Max Popp, lead author of the study and a postdoctoral researcher at the Max Planck Institute for Meteorology in Hamburg, Germany.
In the case of hot, hellish Venus, water that evaporated from the planet’s surface built up high in the planet’s atmosphere and eventually escaped into space. This is called a “moist greenhouse.” Today, the atmosphere of Venus is almost entirely carbon dioxide. (Earth is able to keep its water because this planet’s upper atmosphere is quite dry.)
To better understand the conditions that trigger such extreme greenhouse effects, Popp and his colleagues created a 3D model of an Earth-like planet that was entirely covered by water. This simulated water-world meant the scientists could ignore the complicated effects of continents and seasons.
The researchers discovered that once carbon dioxide levels in the model reached 1,520 parts per million, the planet’s climate was unstable. The surface temperatures rapidly jumped to about 135 degrees Fahrenheit (57 degrees Celsius), creating a warm, moist greenhouse regime, the study reported. (The measurement means there are 1,520 molecules of carbon dioxide for every 1 million air molecules.)
“A planet like Earth will eventually change to a very warm climate, and it will occur relatively abruptly,” Popp told Live Science.
The researchers think changes in large-scale cloud patterns drive the warm, moist greenhouse effect, Popp said. The location and thickness of cloud cover can change how much solar heat is trapped on a planet.
Although the findings suggest that greenhouse gases can be as lethal for a planet as orbiting too close to a sun, this process would occur at carbon dioxide levels significantly higher than those experienced on Earth today, the researchers said.
Popp said it’s likely impossible for human activity to induce a similar moist greenhouse effect on Earth. To do so, human activity would have to raise the concentration of CO2 in the atmosphere considerably, even more than if all the available fossil fuel reserves were burned, the researchers said.
“This is an idealized study designed to give a comparison between solar [heating] and carbon dioxide,” Popp said. As such, Popp said a similar scenario wouldn’t happen on Earth anytime soon.