On March 26, researchers announced the discovery of 2012 VP133, an estimated 280-mile wide (450-kilometer) object that lies just beyond the Kuiper Belt of icy objects that swarm outside of Neptune’s orbit.
The new object is nicknamed “Biden” after the vice-president of the United States, because both Joe Biden and 2012 VP133 are “VPs.” It is one of only two dwarf planets discovered beyond the Kuiper Belt, with Sedna (a decade ago) being the other one. The paper, “A Sedna-like body with a perihelion of 80 astronomical units,” was published in the journal Nature.
Mapping tiny worlds at the Solar System’s edge could one day show scientists how life arose on Earth. That’s because many of these objects could contain organics, carbon-based material that are ingredients for life. [Strangest Places Where Life Is Found On Earth]
As the scientists continue their search, they expect that 2012 VP133 will be the first of a series of discoveries of such objects. Finding such a world has a value of its own, but the team is also thinking of a greater astrobiological question as they study 2012 VP133. Are the possible organics —which show up as ultra-red material in telescopes — a possible source for life on Earth? And could be this be true of other planetary systems as well?
“One of the questions I’ve had is trying to map out what is this ultra-red material in the Kuiper Belt,” said Scott Sheppard, a faculty member at the Carnegie Institution for Science, Department of Terrestrial Magnetism (DTM) in Washington, D.C.
Sheppard co-discovered the object along with the Gemini Observatory’s Chadwick Trujillo.
Curiously enough, 2012 VP133 has none of this material on it, but Sedna does. It will take more discoveries of such objects to figure out if ultra-red material is common outside of the Kuiper Belt, and how organics could have been transported to Earth early in our Solar System’s history.
A treasure trove of possible organics
Most dwarf planets found to date — including Pluto, which was once considered a planet — reside in the Kuiper Belt, a vast collection of frozen objects that orbit our Sun about 30 to 50 astronomical units (AUs) away. One astronomical unit is the distance between the Earth and the Sun, about 150 million kilometers.
There are millions of objects in the Kuiper Belt, but the ones that interest Sheppard and his colleagues are those that have “resonances” with Neptune. An orbital resonance occurs when two bodies — like a planet and a moon, or a planet and an asteroid — exert gravitational influences on each other that put them into closely related orbits.
In a 2012 paper in the Astronomical Journal, “The Color Differences of Kuiper Belt Objects in Resonance with Neptune,”Sheppard examined 58 Kuiper Belt objects that have a resonance with the gas giant.
He found that those resonant objects that are embedded in the Kuiper Belt are full of this ultra-red material, indicating likely organics. On the edge of the belt, some of those objects also still have the material, showing that it is somehow leaking into the inner Solar System. Those that are quite far away, however, show none of the material.
Sedna and 2012 VP133 are well beyond the boundaries of the Kuiper Belt. Sheppard’s new paper argues that they are part of the edges of the Oort Cloud, a theorized icy collection of objects extending thousands of AUs away from Earth. (The Oort Cloud is perhaps best known for being the supposed source of many comets that fly into the inner solar system.)
It’s difficult to envision how dwarf planets such as Sedna and 2012 VP133 could receive ultra-red material from the Kuiper Belt because they are so far away from it. Further, it’s unclear why only Sedna (of the two dwarf planets known in that region) has the material. They’re too far away for Neptune to have any influence on them. So what happened? [New Dwarf Planet Photos: Images of 2012 VP113]
Determining what resonants have and do not have ultra-red material helps us understand how the ultra-red material has moved around the outer Solar System,” said Sheppard.
A big jolt
Looking at other objects, it becomes clear that something big likely disturbed some of them. For example, Sedna’s weird orbit got the attention of researchers because it is so eccentric. The dwarf planet ranges between 80 AU and 940 AU — meaning that one orbit takes about 11,400 years to complete. It’s by far the most eccentric orbit in the Solar System.
“It probably formed much further in and somehow got scattered out there and captured into the no-man land area,” Sheppard said.
Sheppard and Trujillo then compared Sedna’s and 2012 VP133′s orbits with 10 representative Kuiper Belt objects that have eccentric orbits. To their surprise, they found that all 12 of them had almost identical “arguments of perihelion.” That’s an orbital parameter that measures the angle between two points in each object’s orbit: the closest approach to the Sun, and the location where the objects cross the plane of the Solar System.
“They should just have random arguments of perihelion,” Sheppard said.
The similarities point to a giant disturbance causing chaos. There are three theories for this. Perhaps a rogue planet (Earth’s size or smaller) was ejected out of the Solar System, throwing smaller objects aside as it passed into the outer Solar System.
“That rogue planet could have been ejected or it could be out there today,” Sheppard said.
He said it would be too dim to show up in surveys, such as NASA’s Wide-field Infrared Survey Explorer (WISE), a spacecraft more suited to finding gas giant planets, which emit their own heat.
Another theory — the leading one — says a passing star about 200 AU from our own caused huge gravitational disturbances. It seems easy to explain a star tugging on the wandering Sedna, but VP113 has a more circular orbit that only goes as far as 266 AU.
“That makes VP113 more tightly bound to the Sun, and it’s harder to form that from a stellar encounter,” Sheppard said. “It would have to be stronger or a bigger object, so it’s less likely to have happened.”
The third — Sheppard termed it the “dark horse” theory — suggests the Sun captured extrasolar planets from another star early in the Sun’s history, while it was forming in a cloud of gas and young stars.
Hundreds of objects waiting for discovery
As Sheppard wrestles with the question of how the ultra-red material moved around, he’s also interested in learning more about the nature of the material itself. Researchers suspect it’s organics, but what sort of organics is of great interest. Luckily, there’s a chance to take a closer look.
NASA’s New Horizons probe is currently sailing to the outer Solar System. It’s expected to make a pass by Pluto and its moons in 2015 before zooming toward the Kuiper Belt. After the Pluto encounter is finished, perhaps the spacecraft could turn its observations to an ultra-red object. No candidates have been identified yet, but this is a possibility, Sheppard said.
Sheppard’s search of the outer Solar System will continue. He and his collaborators have some suspected new objects that need confirmation, and better yet, his research estimates that there could be at least 900 objects in the Oort Cloud’s fringes that are at least 621 miles (1,000 km) in diameter — a little less than half of Pluto’s size.
“There are for sure some bigger than Pluto, and there might be some bigger than Earth or Mars,” Sheppard said. “We think there’s a lot of these objects out there.“
A team of scientists detected a pair of faraway objects that could be a giant Jupiter-like alien planet and a rocky exomoon flying freely through space, or a small dim star hosting a planet about 18 times more massive than Earth.
The astronomers used a technique called gravitational microlensing, watching what happens a big foreground object passes in front of a star from our perspective on Earth. The nearby body’s gravitational field bends and magnifies the light from the distant star, acting like a lens. [The Strangest Alien Planets Ever (Gallery)]
Analyzing lensing events can reveal a great deal about the foreground object — for example, in the case of a star, whether it hosts a planet and, if so, how massive that world is compared to the star.
In the new study, the team observed one intriguing lensing event using telescopes in New Zealand and the Australian state of Tasmania. They determined that the foreground object has an orbiting companion about 0.05 percent as massive as itself.
“One possibility is for the lensing system to be a planet and its moon, which if true, would be a spectacular discovery of a totally new type of system,” Wes Traub, chief scientist for NASA’s Exoplanet Exploration Program office at NASA’s Jet Propulsion Laboratory in Pasadena, Calif., said in a statement.
“The researchers’ models point to the moon solution, but if you simply look at what scenario is more likely in nature, the star solution wins,” added Traub, who was not involved in the study.
The team could solve the mystery if they knew how far away from Earth the lensing system, called MOA-2011-BLG-262, lies. If it’s relatively nearby, MOA-2011-BLG-262 is probably a starless “rogue planet” and moon; a distant system would have to be as massive as a star to produce the same lensing effects, researchers said.
Unfortunately, the true identity of MOA-2011-BLG-262 will probably remain a mystery forever. Microlensing events are random encounters, so there will be no follow-up observations.
“We won’t have a chance to observe the exomoon candidate again,” study lead author David Bennett, of the University of Notre Dame, said in a statement. “But we can expect more unexpected finds like this.”
And astronomers may be able to measure distances during future microlensing events using the principle of parallax, which describes how the position of an object appears to change when viewed from two different locations.
This strategy could work if observers manage to observe a lensing event with two widely spaced telescopes on Earth, or a ground-based scope and an instrument in orbit, such as NASA’s Spitzer or Kepler space telescopes, researchers said.
Astronomers have discovered more than 1,700 alien planets to date, but they’re still looking for their first confirmed exomoon.
The new study was led by the joint Japan-New Zealand-American Microlensing Observations in Astrophysics (MOA) and the Probing Lensing Anomalies NETwork (PLANET) programs. It appears in the Astrophysical Journal.
The explosion, known as a supernova, would have been visible from Earth several thousand years ago. While the supernova remnant (called DEM L241) has been known since the 1970s, the companion star remained invisible until NASA’s Chandra X-Ray Observatory recently examined the region. Scientists explained the hard-to-kill star’s supernova survival in a video.
The surviving star’s days are numbered, however. Its massive size suggests it too is destined for a catastrophic explosion a few million years from now, researchders said.
Scientists located the star while examining DEM L241, which lies about 160,000 light-years away in the Large Magellanic Cloud, a small galaxy neighboring our own Milky Way. The supernova remnant itself is very bright in X-rays, indicating it’s still hot.
While it’s unclear what remains of the star that exploded, scientists suspect it is either a black hole or a neutron star (a tiny and extremely dense stellar core). This remnant is locked in an orbital dance with the young massive star that is slowly tearing the star apart, researchers added.
“As they orbit one another, the dense neutron star or black hole pulls material away from its companion star through the wind of particles that flows away from its surface,” NASA officials stated on the Chandra website. “If this result is confirmed, DEM L241 would be only the third binary containing both a massive star and a neutron star or black hole ever found in the aftermath of a supernova.”
Besides revealing the hidden companion, Chandra’s observations found that the supernova remnant includes oxygen, neon and magnesium. This information, along with the existence of the nearby massive star, suggests that the exploding star had a mass between 25 and 40 times that of the sun, researchers said.
The scientists are now examining the velocity of the companion star to see if the binary system has a black hole in it.
“Indirect evidence already exists that other supernova remnants were formed by the collapse of a star to form a black hole,” NASA officials added. “However, if the collapsed star in DEM L241 turns out to be a black hole, it would provide the strongest evidence yet for such a catastrophic event.”
This means that in the distant future, the binary system may become either two neutron stars, two black holes, or a black hole and a neutron star orbiting each other.
A paper based on the research, led by Fred Seward of the Harvard-Smithsonian Center for Astrophysics, was published in the Astrophysical Journal in November 2012.
Researchers announced their discovery of the deep watery ocean on Enceladus on Thursday (April 3) in the journal Science, confirming suspicions held by many scientists since 2005, when NASA’s Cassini spacecraft spied geysers of ice and water vapor erupting from Enceladus’ south pole.
The discovery vaults Enceladus into the top tier of life-hosting candidates along with Europa, an ice-sheathed moon of Jupiter that also hosts a subterranean ocean. Both frigid satellites bear much closer investigation, researchers say.
“I don’t know which of the two is going to be more likely to have life. It might be both; it could be neither,” study co-author Jonathan Lunine of Cornell University told reporters yesterday (April 2). “I think what this discovery tells us is that we just need to be more aggressive in getting the next generation of spacecraft both to Europa and to the Saturn system once the Cassini mission is over.”
Cassini arrived in orbit around Saturn in 2004 and is currently scheduled to go out in a blaze of glory in September 2017, when it will dive headlong into the giant planet’s thick atmosphere.
Enceladus’ geysers blast material hundreds of miles into space, offering a way to sample the moon’s subsurface ocean from afar. (Researchers think the ocean is feeding the geysers, though they can’t be sure of this at the moment.)
Cassini has already done some of this work with its mass spectrometer, detecting salts and organic compounds — the carbon-based building blocks of life as we know it — in Enceladus’ plumes during flybys of the moon.
But Cassini’s mass spectrometer can detect only relatively light organics. A follow-up mission to Enceladus should sport a more advanced and more sensitive version of this instrument that could spot a wider range of organics, Lunine said.
“You could actually do this by making flybys of Enceladus, the way that Cassini does now,” he said. “I think you could learn quite a bit about the organic inventory in the plume by flying this device.”
Interestingly, astronomers announced in December that they had discovered plumes of water vapor erupting from Europa’s south polar region as well. So that moon’s ocean could be sampled during flybys, too — perhaps by a mission called the Europa Clipper.
NASA is developing the Europa Clipper as a concept mission at the moment. Recent estimates have pegged the mission’s cost at around $2 billion. That’s pretty steep in these tough economic times, so a scaled-down version might have the best chance of getting it off the ground, NASA officials have said.
Enceladus and Europa aren’t the only icy moons that harbor subsurface oceans; Jupiter’s enormous moon Ganymede also has one, for example. But Ganymede’s appears to be sandwiched between layers of ice, while the seas of Enceladus and Europa are in contact with rocky seafloors, making possible all sorts of interesting chemical reactions, researchers say.
A single gas giant planet in the not-too-warm, not-too-cold habitable zone around its star — where Earth and Mars correspondingly reside — could host several livable moons. At this early point in our hunt for exoplanets, most of the worlds we have found in the habitable zone are giants, not Earths. It’s possible that the first inhabited place we discover outside our Solar System will be a moon.
It is this sort of consideration that inspires René Heller, a postdoctoral fellow in astronomy at McMaster University, in Ontario, Canada. He studies how “exomoons” could form, what they might be like and how we might detect them with current or future astronomical instruments. A major part of his work deals with gauging the habitability of exomoons, which is a bit trickier than planets because moons orbit another body besides their star. [The Strangest Alien Planets Ever (Gallery)]
A new paper by Heller and his colleague Rory Barnes of the University of Washington and the NASA Virtual Planetary Laboratory examines how heat emanating from a freshly formed exoplanet, coupled with irradiation from the solar system’s star, can roast the planet’s moons. Before the planet cools off sufficiently, its close-orbiting moons could lose all their water, leaving them bone-dry and barren.
“An exomoon’s habitability is of course constrained by its location in the stellar habitable zone, but it also has a second heat source — its host planet — that has to be accounted for,” said Heller, whose paper has been accepted for publication in The International Journal of Astrobiology. “With regard to this second source, our study shows that at close range, the illumination from young and hot giant planets can render their moons uninhabitable.”
Researchers believe moons could serve as suitable abodes for life just as well as planets. Even moons far beyond the habitable zone, such as Jupiter’s Europa and Saturn’s Titan, offer tantalizing hints of potential habitability thanks to the subsurface ocean in the former and the intriguing organic chemistry of the latter. Still, a moon around an exoplanet in the habitable zone stands as a far better bet for life than these frigid candidates.
Heller’s findings suggest that we ought to exercise caution, however, before declaring that an Earth-sized, habitable-zone exomoon is a real-life Pandora — the lush moon of science fiction fame in “Avatar.” Before assuming an exomoon is habitable based on its host planet’s locale, the moon’s current and conjectured past orbital distances will need to be assessed.
“Earth-size exomoons that could soon be detected by our telescopes might have been desiccated shortly after formation and still be dry today,” said Heller. “In evaluating a moon’s habitability, it is crucial to consider its history together with that of its host planet.”
Moons are generally thought to arise much like planets do; piecemeal, that is. In the disk of leftover material encircling a star after its birth, planets aggregate as chunks collide and merge together into larger and larger bodies. As their mass and gravity grow in tandem, developing planets similarly attract their own mini-disks of gas and dust. Debris within this secondary disk then coalesces into moons. (Notably, our Moon stands as an exception, likely created by a giant impact to an ur-Earth by another sizable proto-planetary chunk.)
All this crashing about generates a lot of heat. Newly born planetary and lunar bodies should therefore be quite toasty. Yet rocky worlds might be able to retain a water reservoir, or have it be replenished early (or later) on by impacts from icy comets. [9 Exoplanets That Could Host Alien Life]
Where a moon sets up shop around its planet influences the chances of hanging onto any initial water and allowing life a chance without relying upon the fortune of future cometary water. According to formation models, significantly sized satellites should form between about five and 30 planetary radii, or half-planet widths, from their host planet. Jupiter’s four biggest moons, dubbed the Galilean moons, fit this profile: Io orbits at 6.1 Jupiter radii; Europa, 9.7; Ganymede, 15.5; and Callisto squeaks in at 27 Jupiter radii. The biggest moon of Saturn, Titan, makes its home at a distance at of 21.3 Saturn radii.
Finding the ‘habitable edge’
In their new paper, as well as several prior works, Heller and Barnes have sought to figure out just how close is too close for an exomoon to maintain liquid water on its surface. This inner orbital boundary they call the “habitable edge.” Moons within it receive an excess of heat energy from two key sources: firstly, the flexing of the moon, called tidal heating, caused by gravitational interactions with its planetary host, and secondly, from extra illumination from the planet.
Raising the temperature on a watery world can trigger what is known as a runaway greenhouse effect. Water evaporates because of heat. Resulting water vapor is particularly good at trapping heat. In a positive feedback loop, this trapped heat can lead to evaporation of water at a faster rate than cooling, and condensation can restore it back to liquid form. Over time, a world’s entire water supply can end up as a hot gas. This gas is broken down by sunlight into constituent oxygen and hydrogen. The latter, the lightest element, can escape off into space, and the world becomes desiccated.
Orbits, however, are not fixed things. Where a moon orbits today might not be where it initially formed and existed for many millions of years. The tidal forces just mentioned usually work to slowly push a moon out to a wider orbit over time. Thus, the observed location of moons today must be taken with a grain of salt—though appearing “safe” now, their pasts could have left them parched.
“Moons that are outside the habitable edge today, and thereby seemingly habitable, may have once been inside the habitable edge and become dry and uninhabitable,” said Heller.
Building the model
With these considerations in mind, Heller and Barnes set about creating a model of a potentially habitable moon and gas giant duet. The model moons in their study are purposefully not like anything we have in the Solar System. In order to be broadly habitable, regardless of habitable edge considerations, a moon must possess a certain minimum mass, the same as a potentially habitable planet. A livable world must be massive enough to gravitationally retain an atmosphere and generate a protective magnetic field from a molten, rotating iron core. [The Moon: 10 Surprising Facts]
This mass habitability cutoff point is thought to be at least that of Mars, or 10 percent of Earth’s mass. For comparison, the biggest moon in our solar system, Ganymede, is a measly one-fortieth of Earth’s mass. That said, various studies have indicated that gas giant planets much bigger than Jupiter should spawn comparatively super-sized satellites.
The researchers accordingly went with a “monster” Jupiter, a Jovian planet 13 times Jupiter’s mass, as their model host planet. A 13-mass Jupiter is about as massive as a planet can get, scientists think, before entering into brown dwarf or “failed star” territory; in such a case, the planet would emit way too much heat for most exomoons to ever have a prayer of being habitable.
As for hypothetical test moons in the study, Heller and Barnes went with two: an Earth twin, with the same rockiness and mass, and a “super-Ganymede,” an icy body with a quarter of Earth’s mass.
Heller and Barnes then placed these planet-and-moon duos in their model at two different orbital distances from a sunlike star. The first location approximated Earth’s, about 93 million miles away, considered toward the hotter end of a sunlike star’s habitable zone. The second spot was 1.7 times farther away, somewhat past the orbit of Mars, taken here as the outer limit of the habitable zone.
The model also addressed the issue of tidal heating. Moons (and planets) can have oval-shaped orbits that periodically swing them closer to their host. The more “eccentric,” or oval-shaped, such an orbit is in swinging an orbit in close to its planet contributes to greater degrees of tidal heating. For this portion of the model, the researchers opted for four different orbital eccentricities to give a good range of results.
A final numerical consideration was the age of the planet-moon system. Younger giant planets emit more heat than older, cooled-off versions of themselves. So, three ages were picked: 100 million, 500 million and 1 billion years, with the last representing a fairly evolved system.
Now, with all these parameters in place, Heller and Barnes plugged in the critical variable of the hypothetical moons’ orbital distance from host planets.
Life or death?
For both styles of moon, Earth-like and super-Ganymede-esque, an orbital distance of 10 Jupiter radii or less would be bad news for life. A runaway greenhouse effect would commence based on the host planet’s illumination alone for around 200 million years—a fairly decent span of geological time, and certainly long enough to thoroughly dry out the moon. Add in the sun’s rays, and the water-vaporizing interval on the Earth-like moon lasts for 500 million years. For the super-Ganymede, it’s 600 million.
Bump the hypothetical moon distance from its host to a roomier 15 Jupiter radii and the picture still doesn’t improve much; 200 million-plus years or so of moon-cooking still ensues. Out at 20 Jupiter radii, the Earthlike moon is spared a runaway greenhouse effect, but the super-Ganymede still suffers out-of-control heating for a similar couple hundred million year span.
“The thermal irradiation from a super-Jupiter host planet can clearly have a major influence on the habitability of its moons,” said Heller. “Depending on the planet’s mass and the history of its luminosity, any exomoon discovered today would need to have had a sufficiently wide orbit to have avoided desiccation in the far past.”
The findings are somewhat conservative because other sources of heat might factor in enough to tip the scales. Examples include the latent heat within a new moon emanating from forces of friction and pressure during its formation. Plus, life may find it very hard to get going even before the temperature rises enough to kick off a runaway greenhouse effect—the ground could simply be too hot.
For an arid moon, however, its chances of bringing forth life might not be lost forever. Due to gravitational perturbations, it could migrate beyond the habitable edge. Once there, out of the death zone, icy comets pummeling it could deliver vast stores of water after the runaway greenhouse effect has slackened. A cometary bombardment is similarly thought to have deluged Earth several million years after its molten exterior cooled to a hard crust, giving rise to our planet’s life-permitting oceans.
So, the overall message of Heller’s newest study is that Earth-like exomoons’ pasts cannot be ignored. When these worlds are identified, it will be necessary to perform orbital simulations on them to try to glean their histories. The orbital evolution models will be complex, accounting for tidal effects between the planet and the moon, as well as the gravitational perturbations between the moon, other moons, the planet, and the star. Coupled with models of planetary formation and cooling, astrobiologists can hopefully better estimate an exomoon’s current habitability.
Said Heller: “It’s important that we do our best to look deep into an exomoon’s past in order to better understand whether it can possibly support extraterrestrial life.”
When a distant planet appears as a point of light in a telescope, it’s hard to imagine what things are like at the surface. Does rain fall? Is the atmosphere thick, or dissipating into space? How constant is the sunlight on its surface?
Telescopes today are only just beginning to answer that question and get us closer to understanding where extraterrestrial life might exist. As planets transit across the face of their stars, it’s possible for astronomers to figure out what chemicals are contained in the planet atmospheres, and to make predictions. However, until now only hot giant planets are observable.
A senior research scientist with the Meteorological Dynamics Laboratory of the Pierre Simon Laplace Institute in Paris, is part of a group trying to create a model for how planetary atmospheres behave on smaller, rocky planets like Earth, based upon observations in our own solar system. He acknowledges it is limited – we know little about such planets farther in the universe – but the model is a start to learning more about other planets. [The Strangest Alien Planets (Photos)]
“It’s very ambitious,” Forget said. “It’s designed in a way so we can simulate, as much as we can, a planet with any kind of atmosphere around any kind of star, and with this tool explore the range of planets we can have.”
His latest work concerning climates on terrestrial exoplanets, carried out with his colleague Jeremy Leconte, is a synthesis of this experience, along with a survey of the research literature. The paper, called “Possible climates on terrestrial exoplanets”, is available right now on the pre-publishing site Arxiv, and in press with the Proceedings of the Royal Society.
The “punchline” of the research, as Forget put it, is what factors control the composition of a planet’s atmosphere. Studying all sorts of planets will help scientists learn more about life and habitability in distant worlds.
Life in strange places
What is the climate on a planet – and in particular how life-friendly it is- depends on three factors: the atmospheric composition (including the presence or absence of an ocean), its parent star’s variability, type and distance away from the planet, and the type of planetary rotation.
This can lead to life in unexpected places. Perhaps a star is smaller and weaker than our own sun, but the planet is at a shorter distance than the Earth is to its sun. Since that star’s rays have a shorter distance to travel to the planet’s surface, they could warm it to a similar extent as the sun does on the Earth.
Or maybe a planet is roasting right next to a star, tidally locked so that the perpetual day-facing side is too hot to support life. On the night side, however, the atmosphere surrounding the planet could permit pockets of liquid water.
These are all scenarios that Forget and Leconte are considering. A key figure in their paper looks at the different types of atmospheres that are possible depending on the mass of the planet, and its temperature. [9 Exoplanets That Could Host Alien Life]
“This is very highly speculative brainstorming on what kind of cocktail of atmosphere we can have on a terrestrial planet,” Forget said. “We don’t know quantitatively where we should put the boundaries between the various types of atmospheres. Also, keep in mind the physical processes that actually control the composition of the atmosphere are extremely difficult to model and simulate and calculate.”
The research, however, shows that different kinds of planets tend to have specific sorts of atmospheres.
A gas giant, for example, is so huge that its gravity can hold on to the light elements of hydrogen and helium, which were likely the original elements in the solar system when the sun and planets were just coming together from a gas cloud. Earth likely had these elements in abundance in its atmosphere at the beginning, but lost them over time as the planet’s mass is much smaller. A recent Nature Geoscience paper also showed that Mars likely had hydrogen in its atmosphere when it was young.
By contrast, Earth- and Mars-like planets likely would have more carbon dioxide and nitrogen in their atmosphere, the graph shows. Oceans of liquid water are possible. If the planet receives a little too much starlight, however, there can be a runaway greenhouse effect.
“The star light heats up the water, putting more water vapor in the atmosphere, which enhances the greenhouse effect and amplifies the heating,” Forget said.
Eventually, all the oceans can be vaporized. Because the Sun’s luminosity increases with time, this will eventually happen to the Earth. Fortunately, not for another billion years, according to another recent study by Leconte and Forget. Venus being closer to the Sun, received even more sunlight, causing the hydrogen and oxygen atoms contained in the water to escape and leaving carbon dioxide molecules behind; this created Venus’ notoriously thick and stifling atmosphere. [See photos of Venus]
Planets farther away from a star similar to our sun (say, at Jupiter’s distance) would see the carbon dioxide freeze out and collapse on to the surface, although nitrogen can still remain until planets are beyond the equivalent distance of Neptune in our own solar system.
Glancing at Gliese 581
As Forget’s team refines the model it is also applying the research to current exoplanet discoveries. One notable set was several planet candidates found in recent years around Gliese 581, which is about 20 light-years away.
Astronomers initially felt that Gliese 581c was potentially habitable, but changed their minds after follow-up research, Forget explained. “Initially, the astronomers were very excited about 581c, but very quickly they interacted with climatologists like me who said it cannot be habitable. It is way too close to the star and there will be a runaway greenhouse effect,” he said.
A United States-led team discovered Gliese 581g in the center of the star’s habitable region, but that planet has been called into dispute by others who said the discovery was a fluke in the data and not an actual planet. Another planet, Gliese 581d was thought to be too cold as it receives less than a third of the stellar energy Earth does while being so close to its dwarf star that it is likely tidally locked, with one side perpetually facing the star. (That’s similar to how the moon’s rotation behaves around Earth, Forget pointed out.)
“With another member of the team, Robin Wordsworth, we applied our model to the planet and found it was quite easy to show that, with a reasonably thick atmosphere, it still has warm enough temperatures for liquid water, so it’s not impossible that it was habitable,” he said.
As for Gliese 581c – the planet that initially excited astronomers – Forget and Leconte are not altogether ruling out habitability. There could be different climate regions on the planet, with a spot at the edge of the night side still cool enough for liquid water.
Two motivations drive Forget’s team to learn more. The first one is to prepare for observations for a time when telescopes can pick out more about small exoplanet atmospheres, whatever they are: hot, temperate, or very cold. Also, they hope to “make progress on these never-ending questions on habitability, are we alone in the universe, and so on,” he said.
“We have no observations at all about atmospheres on terrestrial planets, yet we know there are a lot of terrestrial planets everywhere; a very high fraction of stars have these planets,” he added. And when those results come in, Forget’s team hopes to be ready to learn more about if life could exist in those places, and how.
The star, called HR 5171 A, shines 12,000 light-years from Earth in the center of a new image released on March 12. Known as a “yellow hypergiant,” The star is more than 1,300 times the diameter of the sun, much larger than scientists expected after earlier observations, European Southern Observatory officials said in a statement. You can see the yellow hypergiant in a new video from ESO as well.
The new measurements place the star as one of the top 10 largest stars ever discovered. Scientists using ESO’s Very Large Telescope Interferometer to observe the star got another surprise as well. HR 5171 A is actually part of a double star system, with its companion orbiting extremely close to the hypergiant.
HR 5171 A is 50 percent larger than the red supergiant Betelgeuse, the star that makes up one of the constellation Orion’s shoulders. Only 12 yellow hypergiants have been found in the Milky Way, and they are in an unstable stage of life, according to ESO. Yellow hypergiants are rapidly changing, and shoot out material that forms a large atmosphere around the star.
“The new observations also showed that this star has a very close binary partner, which was a real surprise,” Olivier Chesneau, a scientist of the Observatoire de la Côte d’Azur in France working with the VLT said in a statement. “The two stars are so close that they touch and the whole system resembles a gigantic peanut … The companion we have found is very significant as it can have an influence on the fate of HR 5171 A, for example, stripping off its outer layers and modifying its evolution.”
Although the huge star is very far from Earth, keen observers can come close to spotting it with the naked eye, ESO officials said. The star shines about 1 million times brighter than the sun.
HR 5171 A has been found to be getting bigger over the last 40 years, cooling as it grows, and its evolution has now been caught in action,” ESO officials said. Only a few stars are caught in this very brief phase, where they undergo a dramatic change in temperature as they rapidly evolve.”
Chesneau and his international team of scientists used a special technique called interferometry to combine the light from multiple individual telescopes, creating a giant telescope they used to observe HR 5171 A, ESO officials said.
The new study will be published in the journal Astronomy & Astrophysics.
The oceans soured into a deadly sulfuric-acid stew after the huge asteroid impact that wiped out the dinosaurs, a new study suggests.
Eighty percent of the planet’s species died off at the end of the Cretaceous Period 65.5 million years ago, including most marine life in the upper ocean, as well as swimmers and drifters in lakes and rivers. Scientists blame this mass extinction on the asteroid or comet impact that created the Chicxulub crater in the Gulf of Mexico.
A new model of the disaster finds that the impact would have inundated Earth’s atmosphere with sulfur trioxide, from sulfate-rich marine rocks called anhydrite vaporized by the blast. Once in the air, the sulfur would have rapidly transformed into sulfuric acid, generating massive amounts of acid rain within a few days of the impact, according to the study, published today (March 9) in the journal Nature Geoscience.
The model helps explain why most deep-sea marine life survived the mass extinction while surface dwellers disappeared from the fossil record, the researchers said. The intense acid rainfall only spiked the upper surface of the ocean with sulfuric acid, leaving the deeper waters as a refuge. The model could also account for another extinction mystery: the so-called fern spike, revealed by a massive increase in fossil fern pollen just after the impact. Ferns are one of the few plants that tolerate ground saturated in acidic water, the researchers said.
The Chicxulub impact devastated the Earth with more than just acid rain. Other killer effects included tsunamis, a global firestorm and soot from burning plants. [The 10 Best Ways to Destroy Earth]
The ocean-acidification theory has been put forth before, but some scientists questioned whether the impact would have produced enough global acid rain to account for the worldwide extinction of marine life. For example, the ejected sulfur could have been sulfur dioxide, which tends to hang out in the atmosphere instead of forming aerosols that become acid rain.
Lead author Sohsuke Ohno, of the Chiba Institute of Technology in Japan, and his co-authors simulated the Chicxulub impact conditions in a lab, zapping sulfur-rich anhydrite rocks with a laser to mimic the forces of an asteroid colliding with Earth. The resulting vapor was mostly sulfur trioxide, rather than sulfur dioxide, the researchers found. In Earth’s atmosphere, the sulfur trioxide would have quickly combined with water to form sulfuric acid aerosols. These aerosols played a key role in quickly getting sulfur out of the sky and into the ocean, the researchers said. The tiny droplets likely stuck to pulverized silicate rock debris raining down on the planet, thus removing sulfuric acid from the atmosphere in just a matter of days.
“Our experimental results indicate that sulfur trioxide is expected to be the major sulfide component in the sulfur oxide gas released during the impact,” Ohno told Live Science in an email interview. “In addition to that, by the scavenging or sweeping out of acid aerosols by coexisting silicate particles, sulfuric acid would have settled to the ground surface within a very short time,” Ohno said.
A NASA spacecraft has pounded another nail into the coffin of the hypothetical solar system body known as “Planet X” or “Nemesis.”
After scanning the entire sky, the space agency’s Wide-Field Infrared Survey Explorer (WISE) found no signs of an undiscovered planet or other large body in the outer reaches of the solar system. The probe did, however, find several thousand new objects much farther out.
“The outer solar system probably does not contain a large gas planet, or a small, companion star,” Kevin Luhman of Penn State University said in a statement. Luhman is the author of one of two new papers appearing in the Astrophysical Journal that describe the results of WISE’s search. [Images from NASA's WISE Space Telescope]
‘Hiding in plain sight’
WISE scanned the sky throughout 2010 and in early 2011, with a six-month gap between the two observations. By comparing the two sets of infrared images, astronomers could identify objects that had moved slightly across the sky. WISE imaged nearly 750 million stars, asteroids, and galaxies, some of which had never been spotted before.
Luhman’s study found 762 new objects among the data, but no signs of a Saturn-sized object out to 10,000 times the Earth-sun distance (an astronomical unit, or AU; 1 AU is about 93 million miles, or 150 million kilometers). Nor did Luhman spot any Jupiter-size or larger objects out to 26,000 AUs.
A second study, led by Davy Kirkpatrick of NASA’s Infrared and Processing Analysis Center at the California Institute of Technology, discovered 3,525 new stars and brown dwarfs, some of which overlapped Luhman’s finds. Brown dwarfs are objects that are larger than planets but too small to sustain fusion in their core as true stars do. As a result, they are far dimmer and more challenging to observe.
“We’re finding objects that were totally overlooked before,” Kirkpatrick said in a statement.
Some of these include extremely close stars, such as one located only 20 light-years away in the constellation Norma. A study that looked at WISE data last year found a pair of brown dwarfs just 6.5 light-years from Earth, making it the closest star system discovered in almost 100 years.
“Neighboring star systems that have been hiding in plain sight just jump out in the WISE data,” mission principal investigator Ned Wright of UCLA said in a statement.
The sun’s unseen companion?
Planets in the inner solar system were easily spotted by early astronomers as they moved across the sky, as were the gas giants Jupiter and Saturn. More distant planets had to wait until the 18th century and the improvement of telescopes for their discovery; Uranus was discovered in 1781 and it took almost another 60 years to locate Neptune.
At the turn of the 20th century, astronomers such as Percival Lowell continued to search for an even more-distant gas planet that could be responsible for disrupting the orbits of Uranus and Neptune.
Lowell dubbed the putative body Planet X; his persistence led to the 1930 discovery of Pluto. By 1978, scientists had concluded that Pluto was too small to affect the larger bodies, and began searching for a large missing planet.
In 1984, paleontologists claimed that a dim companion star to the sun would explain the periodic occurrence of mass extinctions on Earth. A massive body could theoretically disturb objects in the Oort Cloud surrounding the solar system, sending comets hurtling toward Earth with a deadly frequency. Known as Nemesis, scientists suggested the star could be a red dwarf, or a brown dwarf too dim to observe.
But the massive body did not turn up in the data from WISE, which scans the heavens in infrared rather than visual light. Since both new studies turned up relatively distant brown dwarfs, they should have had an easier time spotting a companion close enough to the sun to disturb the Oort Cloud, but neither did.
The recent data isn’t the first evidence against the theoretical bodies. The link between Planet X and mass extinctions was ruled out some time ago. Several infrared sky surveys in addition to WISE have also examined the space around the solar system and found no signs of a companion star to the sun.
After completing its primary mission, WISE began a hibernation stage. Reactivated in 2013 and named NEOWISE, the satellite began its current search for potentially hazardous comets and near-Earth asteroids, also helping scientists learn more about some that were already identified.
Each of the two new studies found objects the other one missed, suggesting that even more distant neighbors exist outside the solar system.
“We think there are even more stars to find out there with WISE,” Wright said. “We don’t know our sun’s backyard as well as you might think.”
Astronomers have detected eight new exoplanet candidates circling nearby red dwarf stars, which make up at least 75 percent of the galaxy’s 100 billion or so stars. Three of these worlds are just slightly bigger than Earth and orbit in the “habitable zone,” the range of distances from a parent star where liquid water could exist on a planet’s surface.
The new finds imply that virtually all red dwarfs throughout the Milky Way have planets, and at least 25 percent of these stars in the sun’s own neighborhood host habitable-zone “super-Earths,” researchers said.
“We are clearly probing a highly abundant population of low-mass planets, and can readily expect to find many more in the near future — even around the very closest stars to the sun,” study lead author Mikko Tuomi, of the University of Hertfordshire in the United Kingdom, said in a statement.
Tuomi and his colleagues spotted the exoplanet candidates after combining data gathered by two instruments — the High Accuracy Radial velocity Planet Searcher (HARPS) and the Ultraviolet and Visual Echelle Spectrograph (UVES), both of which are operated by the European Southern Observatory in Chile.
Both HARPS and UVES employ the radial-velocity technique, which detects exoplanets by noticing the tiny wobbles they induce in their parent stars’ motion toward or away from Earth.
“We were looking at the data from UVES alone, and noticed some variability that could not be explained by random noise,” Tuomi said. “By combining those with data from HARPS, we managed to spot this spectacular haul of planet candidates.”
The eight newfound candidates circle stars located between 15 and 80 light-years away from Earth. The worlds orbit their parent stars at distances ranging from 0.05 to four times the Earth-sun distance (which is about 93 million miles, or 150 million kilometers), researchers said.
The new detection bolster observations made by NASA’s prolific Kepler space telescope, which launched in 2009 to hunt for alien worlds around stars that lie considerably farther away from Earth.
“This result is somewhat expected in the sense that studies of distant red dwarfs with the Kepler mission indicate a significant population of small-radius planets,” said study co-author Hugh Jones, also from the University of Hertfordshire. “So it is pleasing to be able to confirm this result with a sample of stars that are among the brightest in their class.”
Every black hole conceals a secret — the quantum remains of the star from which it formed, say a group of scientists, who also predict that these stars can later emerge once the black hole evaporates.
The researchers call these objects “Planck stars” and believe that they could solve a very important question in modern physics: the information paradox, or the question of what happens to information contained in matter that falls into a black hole.
The idea could also finally reconcile quantum mechanics and Albert Einstein’s general theory of relativity that describes gravity, thus showing how a theory of quantum gravity might solve longstanding puzzles in the world of physics. [The Strangest Black Holes in the Universe]
Warping space and time
Black holes are regions of space so incredibly dense that nothing, not even light, can escape from them. Most are thought to form at the end of a big star’s life, when its internal pressure is insufficient to resist its own gravity and the star collapses under its own weight.
Most scientists believe that, since there is nothing to stop this collapse, eventually a singularity will form — a region where infinite densities are reached and Einstein’s general relativity ceases to be predictive.
But this “singularity theory” has flaws. Since the laws of physics no longer apply in a region of infinite density, no one knows what could possibly happen inside a black hole.
Stephen Hawking suggested in the early 1970s that black holes can slowly evaporate and disappear. But in this case, what happens to the information that describes an object that falls into a black hole? According to general relativity, information cannot simply disappear; inside a black hole, however, information apparently does. This “information paradox” has puzzled researchers for decades.
Carlo Rovelli at the University of Marseille in France and Francesca Vidotto at Radboud University in the Netherlands have attempted to answer this question by exploring the idea that the universe, which is assumed to have started with the Big Bang, actually emerged — because of quantum gravitational effects — from a “big bounce,” following an earlier contracting phase.
“The quantum gravitational effects produce an effective repulsive force, so that matter wouldn’t have collapsed into a singularity, but it would have just reached a maximal compact state,” Vidotto said.
This way, the universe would “bounce” when the energy density of matter reached the Planck scale, the smallest possible size in physics, causing the universe to expand again, and then possibly collapse again, and so on, back and forth. [Alternatives to the Big Bang Theory (Infographic)]
A similar idea has now been proposed for the fate of the collapsing matter of a dying star.Researchers say that quantum effects — similar to those that prevent an electron falling into the nucleus of an atom — would stop the collapse of a star before it could shrink to a single point, or singularity. The star would then become a super-compact object, bounce back during the evaporation process of the black hole and finally explode. Eventually, everything that would have fallen into the black hole would be released.
The researchers say that, as the black hole evaporates and shrinks, its boundary will at some point meet that of the Planck star as it expands after the bounce. When that happens, there is no black hole horizon any more, and all information trapped inside the black hole can escape.
In this case, the information paradox would be solved; the information would simply be re-emitted into the universe.
“The black hole has a huge remnant — a Planck star — and this allows us to understand the evaporation of black holes, their final stage of life, without paradoxes. Paradoxes are not part of nature; they are the sign of some incomplete knowledge,” Vidotto said.
Rovelli agrees: “Information is never too concentrated, and it can escape with the explosion of the star.” This release of information, he estimates, would generate radiation with a wavelength of about 10^-14 cm — the wavelength of gamma rays.
“Now we glimpse a tantalizing possibility: If, in the black holes, matter collapses and then bounces, the expansion can be a very dramatic event, a big explosion,” Vidotto said.
And possibly, the scientists add, astronomers have already observed Planck stars releasing the information into space, in the form of extremely bright events called gamma-ray bursts.
No ‘end of physics’
Finally, if the theory is confirmed, it could be a solid proof that quantum gravity exists, said Aurelien Barrau of the Joseph Fourier University in Grenoble, France, who was not involved in the study.
“The paper shows that there might be experimental consequences of quantum gravity,” he said. “This would be fascinating.”
The next step would be to get a more accurate description of the quantum gravitational process that should lead to the “big bounce,” possibly with the help of an accurate computer simulation of a realistic collapse, said Stefano Liberati, a physicist at SISSA (International School for Advanced Studies, Trieste, Italy), who did not take part in the research either.
“If the idea [is confirmed] with more detailed calculations, it will be further evidence that what we call singularities in general relativity are just situations where our current theory lack predictability, but are resolved successfully by quantum gravity,” he said. “At that point, the Big Bang or the center of black holes would not be ‘the end of physics’ but just another door to be disclosed, leading us to a quantum leap in understanding the nature of our universe.”
The discovery will help better model the evolution of black holes over time, and help uncover the huge influence they can have on their host galaxies.
Black holes are objects with gravitational pulls so powerful, not even light can escape. Black holes grow when gas and dust in space flows or accretes onto them — this matter gets so hot it glows hot with radiation such as X-rays. [Strangest Black Holes in the Universe]
The amount of radiation flowing out from a black hole cannot exceed a certain level known as the Eddington limit or this radiation will blow gas flowing inward away. This limit is based on the black hole’s mass.
However, whether the amount of kinetic energy from a black hole, in the form of jets and winds, was constrained by the same limit was unclear. Insights on these jets and winds is crucial for understanding the critical role black holes can play in their host galaxies — for instance, they could blow on gas hard enough to keep stars from forming.
To help solve this mystery, scientists investigated the black hole called MQ1 at the center of its host galaxy, M83, for more than a year. The galaxy lies about 15 million light-years away from Earth in the constellation Hydra, and is one of the closest and brightest spiral galaxies in the sky, visible with only binoculars.
“This powerful black hole is in a famous nearby galaxy that has been looked at gazillions of times, but was never spotted or never noticed,”study lead author Roberto Soria, an astrophysicist at the International Center for Radio Astronomy Research located in Perth, Australia, told Space.com.
It took a combination of optical, X-ray and radio observations from the Hubble Space Telescope, the Chandra X-ray Observatory and the Australia Telescope Compact Array to find MQ1. “Only when you put all three images together does this black hole really stand out,” Soria said.
By analyzing the gas flowing into the black hole, they inferred its weight as less than 100 times that of the sun. The researchers compared the mass of the black hole with its outgoing kinetic power, which they estimated by looking at how bright its surroundings are with infrared and radio waves — the brighter the surroundings, the more kinetic energy jets and winds from the black holes must be slamming them with.
The scientists discovered the amount of kinetic energy flowing out from this black hole was perhaps two to five times higher than the Eddington limit for a black hole of this mass. “The little mass that is squirting out travels at a speed approaching the speed of light,” Soria said.
Scientists had suspected that even small black holes such as MQ1 could produce huge amounts of kinetic energy. Now they have proof.
“We have finally shown that even a small one can be so powerful,” Soria said. “In our models, we will have to pay more attention to the huge influence black hole jets have in the evolution of young galaxies, even small black holes that maybe would have been ignored in the past.”
Black holes with such a huge jet power are very rare in the nearby universe “so finding one is exciting and helps us understand them better,” Soria said. “We will look at more galaxies a bit further away, up to 50 million light years, to try and discover more of those.”
The scientists detailed their findings online Feb. 27 in the journal Science.
NASA’s planet-hunting Kepler space telescope may be down, but it’s far from out.
Though a glitch ended Kepler’s original operations last May, the mission continues to discover distant worlds, adding a whopping 715 new exoplanets to the tally on Wednesday (Feb. 26). Several thousand more will likely follow in the years to come, and a new mission could get Kepler scanning the heavens again in the near future.
“Kepler is the gift that keeps on giving,” Sara Seager, a professor of physics and planetary science at the Massachusetts Institute of Technology, told reporters Wednesday during a NASA press conference that announced the 715 newfound worlds.
Revolutionizing exoplanet science
Astronomers have discovered about 1,700 exoplanets to date (the exact number depends on which of the five main alien-world catalogs is consulted). Kepler has found more than half of them; Wednesday’s announcement brought its current tally to 961.
And the finds should keep rolling in from the $600 million Kepler mission, which launched in March 2009. The observatory has detected about 3,600 planet candidates, and mission scientists expect that about 90 percent of them will eventually be confirmed as bona fide alien worlds.
But Kepler is about much more than just sheer numbers. The main goal of the spacecraft’s original mission was to determine how commonly Earth-like planets occur throughout the Milky Way galaxy. Team members are confident they will be able to answer this question using the data Kepler has already gathered, which takes some time to get through.
“We have confidence that there will be planets like Earth in other places,” Seager said.
Indeed, one research team recently used Kepler observations to estimate that about 20 percent of sun-like stars have at least one Earth-size planet orbiting in the habitable zone— that just-right range of distances where liquid water, and perhaps life as we know it, could exist.
Kepler has revolutionized the field of exoplanet science in other ways as well, teaching astronomers that multiplanet systems are common in the Milky Way and that small, rocky planets like Earth are much more abundant than gas giants such as Jupiter and Saturn.
A new mission?
Kepler’s original planet hunt ended in May 2013 when the second of its four orientation-maintaining reaction wheels failed, robbing the observatory of its ultraprecise pointing ability.
But team members say that Kepler remains extremely capable with two good wheels, and they’ve proposed a new mission called K2, which would allow the spacecraft to keep hunting for exoplanets, as well as other phenomena and objects such as supernova explosions, asteroids and comets.
The K2 proposal is currently under review at NASA headquarters, and a final decision is expected by May or so, officials have said.
Kepler team members announced Wednesday (Feb. 25) that the telescope had lost a second detector, leaving it with 19 operational “science modules” with which to gather data. But the failure shouldn’t affect the spacecraft’s performance much if at all, mission officials said.
“We were surprised by the loss of module 7, but it appears to have failed randomly, much like module 3 did,” said Kepler deputy project manager Charlie Sobeck, of NASA’s Ames Research Center in Moffett Field, Calif. “It will have very little impact on [Kepler's] ability to continue doing science.”
The new findings, based on data collected by NASA’s X-ray mapping NuSTAR space telescope, may be a clue into what exactly happens in the hearts of stars as they explode as supernovas, the researchers added.
Elements from carbon on upward that make up stars, planets and people are synthesized within massive stars. These elements are spread throughout the universe by the explosions that end the lives of these stars, supernovas that are bright enough to momentarily outshine their entire galaxies.
Stars that are born with more than about eight times the sun’s mass end their lives as so-called core-collapse supernovas. When the core of such a massive star runs out of fuel, it collapses to an extraordinarily dense nugget in a fraction of a second. Further material falling onto this collapsed core can bounce off it, causing a violent shock wave that blasts matter outward.
For decades “our best model of supernova explosions forced the stars to collapse symmetrically,” said study lead author Brian Grefenstette, an astrophysicist at the California Institute of Technology in Pasadena. “Stars are big spherical balls of gas, so it made sense that they should collapse in some kind of spherical way.”
“The problem is that when you try to make a star explode by forcing it to collapse symmetrically, the star doesn’t explode,” Grefenstette told Space.com. “You get a dud.”
This failure apparently happens in symmetrical models because that shock wave that starts at the center of the star and is supposed to destroy it gets trapped by all of the material above it. This mean the shock wave “can’t find a way out,” Grefenstette said.
As such, astrophysicists have explored ways to put ripples in the material of a dying star they call asymmetries “that can let the shock wave out and rip apart the star,” Grefenstette said. However, it was uncertain how exactly core-collapse supernovas should look — the predicted shape could differ significantly depending on which models one used of the explosions.
Now scientists have confirmed that supernovas can be asymmetric by looking at the nearby remnants of such an explosion.
“Our results are really the first step in being able to see what was going on in the center of the star,” Grefenstette said.
Researchers investigated Cassiopeia A, a remnant about 11,000 light-years away of a supernova that happened about 350 years ago. They focused on the distribution of the radioactive titanium isotope Ti-44, which is produced deep in the cores of stars.
The supernova tossed out titanium-44 just like a bomb would scatter debris.
“We’re like forensic scientists studying the radioactive ash that the explosion left behind to try to understand what happened during the explosion,” Grefenstette said.
Since titanium-44 is radioactive, “it glows in a very specific color of light,” Grefenstette said — high-energy X-rays. The researchers looked at this glowing matter using the NuSTAR space telescope (short for Nuclear Spectroscopic Telescope Array), which is “the first telescope that makes detailed images in this color of light, which lets us unlock a lot of the information that was hidden to us before,” Grefenstette said.
These images revealed the radioactive isotope was spread around in an uneven manner. This revealed the explosion was more asymmetrical than could be produced by a spherical explosion, although it was not completely lopsided in nature.
“What our results are pointing toward is the idea that the explosion happens because the core of the star sloshes around a bit during the collapse,” Grefenstette said. “In this case, we think that what happens is like when you boil water on a stove top, where bubbles are made near the bottom of the pot and rise up, making the surface of the water slosh around and letting some steam escape.”
“In the supernova, the heat, instead of coming from the burner on your stove, is coming from small particles called neutrinos, which are produced in the intense pressure at the center of the explosion,” Grefenstette said. “These neutrinos heat the material in the center of the collapse and make large bubbles of hot gas that rise up through the material and cause the core of the star to slosh around a bit.
This sloshing “lets the shock wave escape the material that’s holding it back, and once this happens, it’s kind of like if you punched a hole in the top of a pressure cooker and the whole thing explodes,” Grefenstette said.
A study of teeny-tiny meteorite fragments revealed that two essential components of life on Earth as we know it, could have migrated to our planet on space dust.
Researchers discovered DNA and amino acids components in a smidgen of a space rock that fell over Murchison, Victoria, in Australia in September 1969. Previous studies of the meteorite revealed organic material, but the samples examined then were much larger. This study would lend more credence to the idea that life arose from outside of our planet, researchers said in a statement.
“Despite their small size, these interplanetary dust particles may have provided higher quantities and a steadier supply of extraterrestrial organic material to early Earth,” said Michael Callahan, a research physical scientist at NASA’s Goddard Space Flight Center in Greenbelt, Md. [5 Bold Claims of Alien Life]
Amino acids are the basis of proteins, which are structures that make up hair, skin and other bits of living creatures. DNA is a molecule that contains information on building and running an organism.
Meteorites such as Murchison are rare types of space rocks: the carbonaceous chondrites make up less than 5 percent of meteorites found on Earth, NASA said. Further, the molecules discovered in these space rocks are usually in miniscule concentrations of parts-per-million or parts-per-billion.
These factors have researchers questioning how significant the carbon-rich rocks themselves were in bringing life to Earth. Space dust, however, is more plentiful as it is constantly available from comets and asteroids shedding debris in their travels through the solar system.
The Murchison study (a proof of concept for further work, the researchers say) found life’s building blocks in a sample that weighed about the same as a few eyebrow hairs. The 360-microgram sample was about 1,000 times smaller than a typical sample analyzed by researchers.
Samples from space
This micro-sample required a more sensitive technique than usual to extract the information scientists needed. A nanoflow liquid chromatography instrument organized the molecules, which were then ionized with a nanoelectrospray for analysis in a mass spectrometer.
NASA and other agencies have dealt with small sample sizes before, such as on the Stardust mission that collected particles from Comet Wild-2 and returned them to Earth in 2006. Researchers anticipate the techniques they are using today could be used for other missions in the solar system, especially for sample-return missions.
“This technology will also be extremely useful to search for amino acids and other potential chemical biosignatures in samples returned from Mars and eventually plume materials from the outer planet icy moons Enceladus and Europa,” said Goddard astrobiologist Daniel Glavin, who was co-author on the research.
The study, led by Callahan, was recently published in the Journal of Chromatography A.