This brilliant star explosion, called Supernova 1987A, occurred only 160,000 light-years from Earth in a satellite galaxy of the Milky Way known as the Large Magellanic Cloud. When it was first discovered on Feb. 23, 1987, the supernova was one of the brightest observed and closest to Earth, providing astronomers with a unique opportunity to study the phases before, during and after the death of a star, officials said in a statement from the European Space Agency (ESA).
To celebrate the 30th anniversary of SN 1987A, researchers have released new images, time-lapse videos and animation of the supernova’s evolution.
“Because of its early detection and relative proximity to Earth, SN 1987A has become the best studied supernova ever,” ESA officials said in the statement. “Prior to SN 1987A, our knowledge of supernovae was simplistic and idealized. But by studying the evolution of SN 1987A from supernova to supernova remnant in superb detail, using telescopes in space and on the ground, astronomers have gained revolutionary insights into the deaths of massive stars.”
The Hubble Space Telescope has also studied the supernova in great detail since it launched into space in 1990. At the time, “Hubble was the first to see the event in high resolution” and clearly image the structure of the supernova, which consists of a main ring surrounding the exploded star and two fainter outer rings, ESA officials said.
The Chandra X-ray telescope, which launched in 1999, has also been keeping a close eye on the expanding cloud of gas and remnant star material over the years.
Based on the latest observations of SN 1987A, astronomers have found that the gas and star material was ejected 20,000 years before the supernova explosion actually occurred. Slow-moving stellar winds initially carried some of this material away from the dying star.
However, as the doomed star neared the end of its life, it evolved into a hot body and generated faster stellar winds that caused the slower material to pile up and form the concentric ring-like structures observed around the exploded star, ESA officials said.
“The initial burst of light from the supernova illuminated the rings. They slowly faded over the first decade after the explosion, until the shock wave of the supernova slammed into the inner ring in 2001, heating the gas to searing temperatures and generating strong X-ray emission,” ESA officials said in the statement. “Hubble’s observations of this process shed light on how supernovae can affect the dynamics and chemistry of their surrounding environment, and thus shape galactic evolution.”
Pluto has long been viewed as a distant, cold and mostly dead world, but the first spacecraft to pass by it last year revealed many surprises about this distant dwarf planet.
Data from the New Horizons flyby finished downloading to Earth in October, and while it will take many years for scientists to complete their inventory and model the results, early studies offer intriguing hints of its complex chemistry, perhaps even some form of pre-biological processes below Pluto’s surface. Complex layers of organic haze; water ice mountains from some unknown geologic process; possible organics on the surface; and a liquid water ocean underneath — all of these features point to a world with much more vibrancy than scientists have long presumed.
“The connection with astrobiology is immediate — it’s right there in front of your face. You see organic materials, water and energy,” said Michael Summers, a planetary scientist on the New Horizons team who specializes in the structure and evolution of planetary atmospheres.
Summers has co-authored two research papers on the topic, with the first, “The Photochemistry of Pluto’s Atmosphere as Illuminated by New Horizons,” published in the journal Icarus in September. The second paper, “Constraints on the Microphysics of Pluto’s Photochemical Haze from New Horizons Observations” is in press at the same journal.
In first looking at the images of Pluto, Summers was reminded of a world he has studied for decades while working at George Mason University. Titan, an icy orange colored moon of Saturn, is the only moon in the Solar System with a substantial atmosphere and a liquid (methane) hydrological cycle. It has hydrocarbon chemistry, including ethane and methane lakes that have compounds that may be precursors to the chemistry required for life.
Unlike Titan, Pluto’s atmosphere is thin and sparse, with haze reaching out at least 200 kilometers (125 miles) above the surface, at least ten times higher than scientists expected. But above 30 km (19 miles) Pluto displays a similar paradox to Titan with condensation happening in a region that’s too warm in temperature for haze particles to occur.
NASA’s Cassini spacecraft saw the same oddity in the highest reaches of Titan’s atmosphere (the ionosphere) at about 500 to 600 kilometers above the surface (roughly 310 or 370 miles). Through modeling, scientists determined that the condensation is partially the result of Titan’s photochemistry, whereby ultraviolet sunlight breaks down methane, triggering the formation of hydrocarbons.
“This haze formation is initiated in the ionosphere, where there are electrically charged particles (electrons and ions),” Summers said. “The electrons attach to the hydrocarbons and make them stick together. They become very stable, and as they fall through the atmosphere they grow by other particles sticking to them. The bigger they are, the faster they fall. On Titan, as you go down in the atmosphere the haze particles get more numerous and much larger than on Pluto.”
In retrospect, Summers said it shouldn’t have been too much of a surprise that Pluto likely has the same process. Like Titan, it has a nitrogen atmosphere with methane as a minor component. The main difference, however, is Pluto’s atmosphere is just 10 millibars at the surface, compared to Titan’s 1.5 bar. (A bar is a metric unit of pressure, with 1 bar equal to 10,000 pascal units, or slightly less than the average atmospheric pressure on Earth at sea level.) The atmospheric pressure difference of the two bodies also affects the shape of the haze particles as Titan’s particles taking much longer to fall to the surface and ultimately become spherical, while Pluto’s haze particles fall more rapidly and grow into fractals.
With the possible production of hydrocarbons and nitriles (another organic molecule) on Pluto, even more interesting pre- chemistry for life could take place, Summers said. “You can start building complex pre-biotic molecules,” he said. An example is hydrogen cyanide, possibly a key molecule leading to prebiotic chemistry.
What’s also abundant on Titan are tholins, complex organic compounds created when the Sun’s ultraviolet light strikes the haze particles. It’s rare on Earth, but common on Titan and may have contributed to its orange color. There is also a reddish hue on parts of Pluto’s surface, which could be from a layer of tholins, Summers said.
His quick calculation estimates these tholins could be 10 to 30 meters thick, providing more organic material per square meter than a forest on Earth. This material may also change its chemical composition as cosmic rays (high-energy radiation particles) strike the surface.
Intriguingly, reddish material was also spotted near Pluto’s ice volcanoes, or calderas. It’s possible that the dwarf planet could have a subsurface ocean similar to that suspected on Titan, Saturn’s Enceladus and Jupiter’s Europa. These moons, however, have a tidal source of energy within, created by orbiting their huge central planets and interacting gravitationally with other moons. Pluto is bereft of such heating, but it’s possible that radioactivity in its interior could be keeping the inside liquid, Summers said.
“These are the things you need for life: organics, raw material and energy,” Summers said.
While it’s a stretch right now to say Pluto is hospitable for life, Summers said he is looking forward to doing more modeling. “I’ve been studying Pluto all my life, and never expected to talk about these things being there.”
The dwarf planet Ceres keeps looking better and better as a possible home for alien life.
NASA’s Dawn spacecraft has spotted organic molecules — the carbon-containing building blocks of life as we know it — on Ceres for the first time, a study published today (Feb. 16) in the journal Science reports.
And these organics appear to be native, likely forming on Ceres rather than arriving via asteroid or comet strikes, study team members said.
“Because Ceres is a dwarf planet that may still preserve internal heat from its formation period and may even contain a subsurface ocean, this opens the possibility that primitive life could have developed on Ceres itself,” Michael Küppers, a planetary scientist based at the European Space Astronomy Centre just outside Madrid, said in an accompanying “News and Views” article in the same issue of Science.
“It joins Mars and several satellites of the giant planets in the list of locations in the solar system that may harbor life,” added Küppers, who was not involved in the organics discovery.
The $467 million Dawn mission launched in September 2007 to study Vesta and Ceres, the two largest objects in the main asteroid belt between Mars and Jupiter.
Dawn circled the 330-mile-wide (530 kilometers) Vesta from July 2011 through September 2012, when it departed for Ceres, which is 590 miles (950 km) across. Dawn arrived at the dwarf planet in March 2015, becoming the first spacecraft ever to orbit two different bodies beyond the Earth-moon system.
During its time at Ceres, Dawn has found bizarre bright spots on crater floors, discovered a likely ice volcano 2.5 miles (4 km) tall and helped scientists determine that water ice is common just beneath the surface, especially near the dwarf planet’s poles.
The newly announced organics discovery adds to this list of achievements. The carbon-containing molecules — which Dawn spotted using its visible and infrared mapping spectrometer instrument — are concentrated in a 385-square-mile (1,000 square km) area near Ceres’ 33-mile-wide (53 km) Ernutet crater, though there’s also a much smaller patch about 250 miles (400 km) away, in a crater called Inamahari.
And there could be more such areas; the team surveyed only Ceres’ middle latitudes, between 60 degrees north and 60 degrees south.
“We cannot exclude that there are other locations rich in organics not sampled by the survey, or below the detection limit,” study lead author Maria Cristina De Sanctis, of the Institute for Space Astrophysics and Space Planetology in Rome, told Space.com via email.
Dawn’s measurements aren’t precise enough to nail down exactly what the newfound organics are, but their signatures are consistent with tar-like substances such as kerite and asphaltite, study team members said.
“The organic-rich areas include carbonate and ammoniated species, which are clearly Ceres’ endogenous material, making it unlikely that the organics arrived via an external impactor,” co-author Simone Marchi, a senior research scientist at the Southwest Research Institute in Boulder, Colorado, said in a statement.
In addition, the intense heat generated by an asteroid or comet strike likely would have destroyed the organics, further suggesting that the molecules are native to Ceres, study team members said.
The organics might have formed via reactions involving hot water, De Sanctis and her colleagues said. Indeed, “Ceres shows clear signatures of pervasive hydrothermal activity and aqueous alteration,” they wrote in the new study.
Such activity likely would have taken place underground. Dawn mission scientists aren’t sure yet how organics generated in the interior could make it up to the surface and leave the signatures observed by the spacecraft.
“The geological and morphological settings of Ernutet are still under investigation with the high-resolution data acquired in the last months, and we do not have a definitive answer for why Ernutet is so special,” De Sanctis said.
It’s already clear, however, that Ceres is a complex and intriguing world — one that astrobiologists are getting more and more excited about.
“In some ways, it is very similar to Europa and Enceladus,” De Sanctis said, referring to ocean-harboring moons of Jupiter and Saturn, respectively.
“We see compounds on the surface of Ceres like the ones detected in the plume of Enceladus,” she added. “Ceres’ surface can be considered warmer with respect to the Saturnian and Jovian satellites, due to [its] distance from the sun. However, we do not have evidence of a subsurface ocean now on Ceres, but there are hints of subsurface recent fluids.”
Baby pictures of a newborn supernova have captured this stellar explosion after the first half-dozen hours of its life, shedding light on how these giant explosions happen, a new study finds.
This newly discovered cosmic baby is the type of supernova that occurs when a giant star runs out of fuel and explodes. Supernovas are so bright that they can briefly outshine all of the other stars in their home galaxy.
Astronomers have previously seen glimpses of supernovas within the first minutes after they explode. However, until now, researchers had not captured light from a newborn supernova across the so many wavelengths — including radio waves, visible light and X-rays. The new images add to evidence that suggests that these dying stars may signal their upcoming demise by spewing a disk of material in the months before their deaths, according to a paper describing the finding.
Much remains unknown about how and why dying stars can detonate with such violence. Studying the final years of a star that is destined to die as a supernova could reveal key details about the way in which these explosions happen, but stars in these brief, final stages are rare — statistically, it is very likely that none of the 100 billion to 400 billion stars in the Milky Way galaxy are within one year of dying as a supernova, according to the new paper.
Now scientists report the discovery of a supernova just 3 hours after it exploded, helping them capture “the earliest spectra ever taken of a supernova explosion,” said study lead author Ofer Yaron, an astrophysicist at the Weizmann Institute of Science in Rehovot, Israel. A light spectrum is essentially detailed look at the wavelengths of light emitted by an object. Because chemical elements can absorb certain wavelengths, stellar spectra can be used to reveal the composition of a star.
“Until several years ago, catching a supernova a week after explosion was regarded as early,” Yaron told Space.com. “This is not the case anymore.”
The astronomers detected the supernova known as SN 2013fs on Oct. 6, 2013, using the data from the Intermediate Palomar Transient Factory (iPTF) based at the Palomar Observatory in California. Its star was likely a red supergiant about 10 to 17 times heavier than the sun and several hundred times wider than the sun, Yaron said.
The supernova detonated about 160 million light-years away in a spiral galaxy called NGC 7610. This galaxy is relatively close to the Milky Way, making it easier for scientists to aim more telescopes at it and detect signals from it that span almost the entire the spectrum of light, from radio waves to X-rays. Observations of the supernova were made with telescopes at the Keck Observatory in Hawaii and NASA’s Swift satellite starting about 6 hours after the explosion, Yaron explained.
SN 2013fs was the most common variety of supernova: a Type II. This kind of supernova happens when the core of a massive star runs out of fuel, collapses to an extraordinarily dense nugget in a fraction of a second and then bounces and blasts its material outward.
The astronomers captured pictures of the newborn supernova early enough to spot a disk of matter the star expelled just before its demise. Normally supernovas are seen after the shockwave from the explosions have swept away such material and any secrets that the disk might have contained.
The researchers found that a year or so before this star died, it rapidly spewed out vast amounts of material, equal to about one-thousandth of the sun’s mass, at speeds of nearly 224,000 mph (360,000 km/h). Previous research had seen cases where such early eruptions occurred among unusual subgroups of Type II supernovas, but these new findings suggest that such outpourings also precede more common kinds of Type II supernovas.
“It’s as if the star ‘knows’ its life is ending soon, and puffing material at an enhanced rate during its final breaths,” Yaron told Space.com. “Think of a volcano or geyser bubbling before an eruption.”
These findings suggest that a star may be unstable months before its turns into a Type II supernova. As such, “the structure of the star when it explodes may be different than that assumed so far,” Yaron said. For instance, the core of a star may experience upheavals during its final days, causing strong winds to travel from the depths of the star all the way to its surface and beyond.
New, automated surveys of the sky such as the iPTF have begun capturing supernovas a day or less after they explode.
“With the help of new sky surveys coming up in the very near future, we expect to significantly increase the number of supernova events for which we are able to obtain early observations within hours and maybe minutes from explosion,” Yaron said.
The scientists detailed their findings online Feb. 13 in the journal Nature Physics.
When some stars reach the end of their lives, they explode in a bright stellar event called a supernova, releasing material created in the heart of the star out into the universe. There are different types of supernova explosions, and astronomers generally classify these powerful outbursts based on the presence of hydrogen.
“While stars begin their lives with hydrogen fusing into helium, large stars nearing a supernova death have run out of hydrogen as fuel,” NASA officials said in a statement. “Supernovae in which very little hydrogen is present are called ‘Type I.’ Those that do have an abundance of hydrogen, which are rarer, are called ‘Type II.'”
But in a recent study published in The Astrophysical Journal, astronomers examine a supernova called SN 2014C that released a lot of material (including mostly hydrogen and heavier elements) unusually late in its life but before it exploded. The so-called chameleon supernova — perhaps named because its appearance makes it look like something other than itself — resides in a spiral galaxy about 36 million to 46 million light-years from Earth.
“This ‘chameleon supernova’ may represent a new mechanism of how massive stars deliver elements created in their cores to the rest of the universe,” Raffaella Margutti, lead author of the study and an assistant professor of physics and astronomy at Northwestern University, said in the statement. “Expelling this material late in life is likely a way that stars give elements, which they produce during their lifetimes, back to their environment.”
The material released into the universe following massive star explosions serves as the building blocks of Earth and other planets in our solar system. However, astronomers question why SN 2014C would throw off so much hydrogen before exploding.
Using NASA’s NuSTAR (Nuclear Spectroscopic Telescope Array) satellite, astronomers found that “SN 2014C had transformed itself from a Type I to a Type II supernova after its core collapsed,” NASA officials said in the statement. Although hydrogen was not detected in initial observations, shock waves coming from the star explosion hit an outer shell of mostly hydrogen material, suggesting the star released the material decades to centuries before it exploded.
What’s more, astronomers also found that the “supernova brightened in X-rays after the initial explosion, demonstrating that there must be a shell of material, previously ejected by the star, that the shock waves had hit,” according to observations from NASA’s Chandra and Swift observatories
One hypothesis for SN 2014C’s unusual behavior is that the star was part of a binary system and did not die alone — its possible the gravitational pull of a nearby star influenced SN 2014C’s evolution, according to the statement. Roughly seventy percent of massive stars have companions, NASA officials said.
“The notion that a star could expel such a huge amount of matter in a short interval is completely new,” Fiona Harrison, NuSTAR principal investigator and professor of physics and astronomy at Caltech, said in the NASA statement. “It is challenging our fundamental ideas about how massive stars evolve, and eventually explode, distributing the chemical elements necessary for life.”
An international team of scientists tasked with fleshing out the main goals of the mission, which is known as Venera-D, is wrapping up its work and will deliver its final report to NASA and the Russian Academy of Sciences’ Space Research Institute by the end of the month, said David Senske, of NASA’s Jet Propulsion Laboratory in Pasadena, California.
“Is this the mission that’s going to fly? No, but we’re getting there,” Senske, the U.S. co-chair of this “joint science-definition team,” told Space.com last month at the annual fall meeting of the American Geophysical Union, in San Francisco.
Venera-D is led by Russia, which has been developing the project for more than a decade. The mission would mark a return to once-familiar territory for the nation; Russia’s forerunner state, the Soviet Union, launched a number of probes to Venus from the early 1960s through the mid-1980s, as part of its Venera and Vega programs. (“Venera” is the Russian name for Venus.)
“Russia has always been interested in going back to Venus,” Senske said.
NASA got involved about three years ago, when Russia asked if the U.S. space agency would be interested in collaborating on the mission, Senske added.
The joint science-definition team arose out of those initial discussions. The team stood down shortly thereafter; Russia’s March 2014 annexation of Crimea prompted NASA to suspend most cooperation with Roscosmos, Russia’s federal space agency (with activities involving the International Space Station being the most prominent exception).
But the collaboration was up and running again by August 2015, Senske said, and the team met in Moscow that October. More meetings are planned, including a workshop this May that will inform decisions about the mission’s scientific instruments, he added.
Venera-D is a large-scale mission, comparable in scope to NASA “flagship” efforts such as the $2.5 billion Curiosity Mars rover, Senske said. The baseline concept calls for an orbiter that will study Venus from above for at least three years, plus a lander that will operate for a few hours on the planet’s surface.
Mission planners said they had originally hoped the lander could survive for 30 days; the “D” in Venera-D stands for “dolgozhivushaya,” which means “long lasting” in Russian. But this goal was ultimately deemed too difficult and costly, given the blistering temperatures on Venus’ surface, according to RussianSpaceWeb.com (which outlines the mission’s tortuous history in rich detail).
Data gathered by the orbiter should help scientists better understand the composition, structure and dynamics of Venus’ atmosphere, including why the planet’s air rotates so much faster than the surface does, a mysterious phenomenon known as super-rotation, Senske said.
The lander will collect further atmospheric information while descending, then study the composition and morphology of the Venusian surface after touching down.
Venera-D could incorporate additional components as well. Some ideas on the drawing board include a handful of small, relatively simple ground stations that would gather surface data for a month or so (putting the “D” back in Venera-D) and a solar-powered, uncrewed aerial vehicle that would ply the Venusian skies.
The surface of Venus is far too hot to support life as we know it, but temperatures are much more hospitable at an altitude of 31 miles (50 kilometers) or so. Furthermore, the planet’s atmosphere sports mysterious dark streaks that some astronomers have speculated might be signs of microbial life. The UAV could hypothetically investigate this possibility, sampling the air while cruising along.
Engineers have already been thinking about how to build such an aircraft. For example, the U.S. aerospace company Northrop Grumman and partner L’Garde Inc. have been researching a concept vehicle called the Venus Atmospheric Maneuverable Platform (VAMP) for several years now.
It’s still too early to know exactly what Venera-D will look like, what it will do or when the mission will launch. A liftoff in 2025 or 2026 is possible under an “aggressive” time line, Senske said. “It depends when the Russians can get this into their federal space budget,” he said.
Some things are known, however. For instance, Russia will build the orbiter and the lander, and Venera-D will launch atop Russia’s in-development Angara A5 rocket, Senske said. If NASA remains involved in the mission — which is far from a given at this point — the U.S. space agency will likely contribute smaller items, such as individual scientific instruments.
“Russia is definitely in the driver’s seat,” Senske said. “NASA is the junior partner.”
Space weather can be a nightmare for planetary atmospheres, particularly for ones that don’t have a magnetic field to protect them — unlike Earth’s, which has a powerful magnetosphere acting as a shield. It might therefore be strange to hear that dwarf planet Pluto, which isn’t known for its powerful global magnetic field, is able to possess an atmosphere at all. But like other planets in the solar system, the sun erodes Pluto’s atmosphere — albeit at a slower rate than expected.
Although astronomical measurements detected the presence of an atmosphere at Pluto long before the NASA New Horizons flyby in July 2015, very little was known about how much was being eroded into space by the continuous stream of solar wind particles. New Horizons measurements, however, proved that the rate of atmospheric loss was 100 times less than expected and, in new research published this week in the journal Icarus, researchers think they know what might be protecting Pluto’s tenuous atmospheric gases.
Researchers from Georgia Institute of Technology have shown that when Charon orbits between Pluto and the sun, its presence can modify the dwarf planet’s bow shock — a standing shock wave that appears “upstream” of Pluto as the solar wind particles encounter Pluto’s thin atmosphere, like the wave that roils in front of a boat’s bow when it powers through water — thereby shielding Pluto’s atmosphere for a short time. Charon maximizes this protection should it also have an atmosphere, but its protective impact is minimal when it either doesn’t have an atmosphere or when it is positioned “downstream” of Pluto.
As Pluto and Charon orbit so close to one another, the pair are believed to share atmospheric gases and when Charon passes behind Pluto particles originating from Pluto are deposited at the moon’s poles, appearing as a dark brown deposit in New Horizons observations.
As Pluto is located so far away from the sun in the Kuiper Belt, the impact of the solar wind is much lower than its impact on planets closer to the sun. The space weather impact has been reduced even further with the help of Charon.
As a result inner Planets by solar wind,” said Georgia Tech student John Hale. “Even at its great distance from the sun, Pluto is slowly losing its atmosphere. Knowing the rate at which Pluto’s atmosphere is being lost can tell us how much atmosphere it had to begin with, and therefore what it looked like originally. From there, we can get an idea of what the solar system was made of during its formation.”
As Pluto and Charon orbit so close and Charon is roughly half the size of its dwarf planet buddy, the pair orbits a common point in space known as the “barycenter.” This orbital oddity added fuel to the debate as to whether Pluto should be called a dwarf planet, or whether Pluto and Charon should be designated a “binary planet.” Now, with more findings about the pair’s atmospheric interactions, it could be argued that the case for calling Pluto a binary planet is as valid as ever.
Betelgeuse is a “red supergiant” that will soon die in a supernova explosion. As the name of its stellar class indicates, Betelgeuse has bloated immensely as the end of its life has neared. Although Betelgeuse’s mass is just 15 to 25 times that of the sun, the star is currently about 860 million miles (1.4 billion kilometers) across, or 1,000 times wider than Earth’s star. (If you put Betelgeuse in the sun’s location, the red star’s surface would extend past the orbit of Mars and into the asteroid belt.)
Such an enormous star should be spinning slowly, since rotation rate decreases as size increases. (Think about how ice-skaters control their spin speed by bringing their arms in close to their body or extending them.) But that’s not the case with Betelgeuse, which is rotating at a blazing 33,500 mph (53,900 km/h), astronomers said.
“We cannot account for the rotation of Betelgeuse,” study lead author J. Craig Wheeler, an astronomer at the University of Texas at Austin, said in a statement. “It’s spinning 150 times faster than any plausible single star just rotating and doing its thing.”
But Wheeler and his colleagues may have an answer. Their computer models suggest that Betelgeuse’s puzzling spin could be explained if the giant gobbled up a companion roughly the same mass as the sun 100,000 years or so ago. (The angular momentum of the companion’s orbit would be transferred to Betelgeuse, speeding up the giant’s rotation to its current rate
This act of cannibalism likely would have spurred a cosmic belch of sorts, causing Betelgeuse to blast a cloud of material out into space at about 22,400 mph (36,000 km/h), Wheeler said. Indeed, astronomers have spotted a shell of matter at roughly the distance from Betelgeuse that this scenario predicts, he added.
Although there are other possible explanations for this space cloud, “the fact is, there is evidence that Betelgeuse had some kind of commotion on roughly this timescale,” Wheeler said.
Betelgeuse lies about 640 light-years from the sun. Like other supergiants, it will die young; the star is only about 10 million years old. The sun, by contrast, is nearly 4.6 billion years old and is only about halfway through its life.
The new study was published today (Dec. 19) in the journal Monthly Notices of the Royal Astronomical Society.
The left lobe of Pluto’s “heart” is a 600-mile-wide (1,000 kilometers) plain called Sputnik Planitia (formerly known as Sputnik Planum), which astronomers think is an enormous impact crater. This basin has been filling with nitrogen ice over the years and now contains huge amounts of the stuff. Indeed, observations by NASA’s New Horizons spacecraft, which flew by Pluto last year, suggest that Sputnik Planitia’s ice may be up to 6 miles (10 km) thick.
Sputnik Planitia is aligned nicely with Pluto’s “tidal axis” — the line along which the gravitational pull from the dwarf planet’s largest moon, Charon, is the strongest. And that’s probably no coincidence, according to two new studies, both of which were published online today (Nov. 16) in the journal Nature.
In the first study, James Keane, a doctoral student at the University of Arizona’s Lunar and Planetary Laboratory, and his colleagues modeled what happened as nitrogen ice accumulated in Sputnik Planitia. The results were dramatic.
“Once enough ice has piled up, maybe a hundred meters thick, it starts to overwhelm the planet’s shape, which dictates the planet’s orientation,” Keane said in a statement. “And if you have an excess of mass in one spot on the planet, it wants to go to the equator. Eventually, over millions of years, it will drag the whole planet over.”
This tumble brought Sputnik Planitia to the southeast, until the plain faced directly away from Charon as it does today. The team’s models predicted this very orientation: In this spot, near the tidal axis, the additional mass causes the least wobble in Pluto’s spin, the researchers said. (Pluto and Charon are tidally locked, meaning the two bodies always show the same face to each other, just as Earth’s moon always shows just one side to Earth.)
Pluto’s reorientation would have stressed the dwarf planet’s crust, leading to a network of faults and fractures on the surface, Keane and his colleagues report. And New Horizons spotted just such a network, whose characteristics match those predicted by the team’s models, they said.
Those models assume that Pluto harbors a subsurface ocean of liquid water — a notion bolstered by the second study, which was led by Francis Nimmo, a professor of Earth and planetary sciences at the University of California, Santa Cruz.
Nimmo and his team determined that the odds of Sputnik Planitia occurring in its present location, so close to the tidal axis, purely by chance were just 5 percent. So they, too, believe that a substantial reorientation has taken place.
The researchers suggested that the impact that created the basin weakened the crust overlying a buried ocean, causing some of the water to rise close to the surface. This action, along with the deposition of nitrogen ice in Sputnik Planitia, would have created enough of a “positive mass anomaly” to roll the dwarf planet, Nimmo and his colleagues wrote.
It’s hard to imagine Pluto reorienting in this way if it didn’t have an ocean, Nimmo said. For example, the team’s calculations suggest that Sputnik Planitia’s ice layer would have to be 25 miles (40 km) thick if no ocean existed.
“Our view is that 40 kilometers’ thickness of nitrogen ice is not that likely,” Nimmo told Space.com. “So if you want to have another source of dense material down there, then water seemed like a very natural explanation, because water is a lot denser than ice.”
The team also considered the possibility that rock migrated in to make up the extra mass, but that explanation doesn’t seem likely, either, Nimmo said.
“The rock is so far down there, and it’s also pretty strong,” he said. “So it’s hard to figure out how that rock would get moved around in the way that you would need.”
Other research groups also have suggested that Pluto may harbor a subsurface ocean, using other lines of evidence. One such argument points to the dwarf planet’s surface fractures, which may be the result of this ocean gradually freezing over time — a prospect also raised by Keane and his colleagues in their paper. (Water expands as it freezes, which would lead to stresses in overlying rock or ice.) In addition, Nimmo said, Pluto doesn’t have an equatorial bulge — and bodies with oceans can’t maintain such a bulge.
“All these lines of argument are pointing in the same direction,” Nimmo said.
If Pluto does have an ocean, how has it managed to avoid freezing up entirely over the past 4.5 billion years? Pluto is big enough that it may have retained a substantial amount of internal heat, Nimmo said. And the dwarf planet’s water may contain significant amounts of ammonia or other substances that act as an antifreeze, he added.
Astronomers think subsurface oceans exist on the Saturn moons Enceladus and Titan; the Jovian satellites Europa, Ganymede and Callisto; and a number of other solar system bodies. Indeed, such buried water may be abundant in the Kuiper Belt, the ring of frigid objects beyond Neptune’s orbit, Nimmo said.
“My guess is that, on big Kuiper Belt objects, these kinds of oceans are pretty common,” Nimmo said. “One of the lessons of the last 20 years is that oceans pop up in all kinds of unexpected places.”
The asteroid, called 16 Psyche, is one of the most massive in the asteroid belt. Researchers think the 186-mile-wide (300 kilometers) body, made of almost pure nickel-iron, might be the core of a world whose outer layers were blasted off by impacts billions of years ago.
Previous observations of Psyche showed no water on the surface. But according to Vishnu Reddy, an assistant professor at the University of Arizona’s Lunar and Planetary Laboratory, new data from the NASA Infrared Telescope Facility show evidence for water or hydroxyl, a molecule with one hydrogen atom bound to one oxygen atom, on Psyche’s surface. Hydroxyl exists on Earth, but it is very reactive and tends to combine with other compounds — and in fact can remove those compounds from the air.
“We did not expect a metallic asteroid like Psyche to be covered by water and/or hydroxyl,” Reddy said in a statement. “Metal-rich asteroids like Psyche are thought to have formed under dry conditions without the presence of water or hydroxyl, so we were puzzled by our observations at first.”
Reddy presented his results Wednesday (Oct. 20) at the 48th meeting of the American Astronomical Society’s Division for Planetary Sciences and 11th European Planetary Science Congress in Pasadena, California.
The water could have reached Psyche via past impacts from smaller asteroids that contain volatiles such as carbon, hydrogen and water, Reddy said.
NASA is currently reviewing a proposed mission to Psyche, which could tell astronomers whether the signal from the surface comes from water or hydroxyl.
The new research, co-authored by Reddy and led by Driss Takir at the U.S. Geological Survey, has been accepted to the Astronomical Journal, and can be read online here.
A strange and colossal ring system around an alien planet is apparently stuck in reverse, circling opposite to the planet’s own orbit around its parent star. While the arrangement appears unstable, new calculations show the rings could remain for at least 100,000 years.
These rings could account for bizarre eclipse behavior seen in 2007 for this star, called J1407, researchers on the new study suggested. Back then, astronomers observed an eclipse of the star last for several weeks, varying rapidly in brightness over the course of minutes. In 2015, the team suggested that there could be a planet orbiting this star with rings over a hundred times larger than the rings of Saturn.
In the new simulations conducted this year, the team calculated whether the planet could hang on to its ring system even as the gravitational effect of the star pulls on the rings. Because of the planet’s highly elliptical orbit, the star’s tug could potentially destabilize the rings when the planet approached closer, the researchers said.
According to the simulations, the system can stay stable for more than 10,000 orbits lasting 11 years each, with one stipulation, said lead author Steven Rieder, a postdoctoral fellow at the RIKEN Advanced Institute for Computational Science in Japan.
“The system is only stable when the rings rotate opposite to how the planet orbits the star,” Rieder said in a statement. “It might be far-fetched, massive rings that rotate in opposite direction,” he added, “but we now have calculated that a ‘normal’ ring system cannot survive.” More usually, a planet’s rings circle in the same direction as the planet is traveling, and the planet orbits in the same direction as the star turns.
It’s also possible that the stellar eclipses were created by a free-floating object passing between Earth and the star, but this would be true only if that object’s velocity as measured in the observations was not correct, Rieder said. He added that this would be a strange explanation, as the measurements the team obtained are “very accurate.”
The researchers said they next plan to examine how the ring structure was created, and how it evolves. A paper based on the research will appear shortly in the journal Astronomy and Astrophysics.
The dwarf planet, called 2014 UZ224, measures about 330 miles (530 kilometers) across and is located about 8.5 billion miles (13.7 billion km) from the sun, NPR reported today (Oct. 11). For comparison, Pluto’s largest moon, Charon, is about 750 miles (1,200 km) in diameter, and reaches a maximum distance of about 4.5 billion miles (7.3 billion km) from the sun.
A year on 2014 UZ224 (the time it takes the dwarf planet to orbit the sun) is about 1,100 Earth years. One Pluto year, for c is about 248 Earth years. The new object was also confirmed by NASA.
David Gerdes, a professor of astronomy at the University of Michigan, told NPR that the new dwarf planet was discovered using an instrument called the Dark Energy Camera (DECam). The universe is not only expanding but accelerating in that expansion, and “dark energy” is the name scientists have given the mechanism powering that expansion. The DECam was built to observe the movement of galaxies and supernovas (exploding stars) as they move away from the Earth. The goal is to provide more clues that will help reveal what dark energy actually is or where it comes from.
A project called the Dark Energy Survey is using observations from the DECam to create a map of the universe that provides information relevant to the study of dark energy. The DES maps have already been used to study dark matter (which makes up about eighty percent of all the mass in the universe but whose exact nature is still a mystery) and to find previously unidentified objects.
Part of the DES includes taking images of a few small patches of the sky “roughly” once per week, according to the mission website, and that’s what made this new discovery possible. While stars and galaxies appear in the same place in the sky, an object that is relatively close to Earth and orbiting the sun might appear to move over the course of a week or a few weeks.
A few years ago, Gerdes asked some visiting undergraduates to look for unidentified solar system objects in the galaxy map, according to NPR. The challenge was slightly difficult because the repeated observations would take place at irregular intervals, Gerdes said, but the students developed computer software to work with the irregularities and spot moving objects.
It took two years to confirm the detection of 2014 UZ224, NPR reports, and while its exact orbital path is still unclear, the scientists behind the discovery say they think that 2014 UZ224 is the third most-distant object in the solar system.
The smallest object in the solar system that has earned the title of “dwarf planet” (prior to this new discovery) is Ceres, which lies in the asteroid belt between Jupiter and Mars. Ceres is 590 miles (950 km) across. The object 2014 UZ224 might be too small to be considered a dwarf planet, Gerdes told NPR, but that will have to be decided by the International Astronomical Union (which made the controversial decision to demote Pluto to a dwarf planet). There are four other recognized dwarf planets in the solar system, but scientists think there could be dozens — or even more than 100 — objects that size that have yet to be discovered, according to NASA.
The region beyond Neptune’s orbit is known as the Kuiper Belt, a disk that is believed to contain thousands of icy, rocky bodies. Beyond that is a region known as the Oort Cloud — a sphere of icy, rocky bodies that surrounds the rest of the solar system. Most comets originate in the Kuiper Belt or the Oort Cloud, but their wide orbits bring them close to the sun.
While the outer regions of the solar system are thought to be made up mostly of objects smaller than Pluto, there may be another planet nearly the size of Neptune lurking in this outer territory. Recent research has shown that the movement of known bodies in the outer solar system may point to the existence of this ninth planet (which scientists have dubbed Planet Nine); that research has prompted efforts to spot the new planet with telescopes.
This huge ocean is probably buried about 60 miles (100 kilometers) beneath Dione’s icy shell, according to the study. Intriguingly, Dione’s putative ocean is likely in contact with the moon’s rocky core, team members said.
“The contact between the ocean and the rocky core is crucial,” study co-author Attilio Rivoldini, of the Royal Observatory of Belgium in Brussels, said in a statement. “Rock-water interactions provide key nutrients and a source of energy, both being essential ingredients for life.”
If the researchers are correct, 700-mile-wide (1,120 kilometers) Dione would be the third Saturn moon known to harbor a subsurface ocean, after giant Titan and geyser-spouting Enceladus. Astronomers think the Jupiter moons Europa, Callisto and Ganymede also have buried oceans, and recent research indicates Pluto might as well.
The study team, led by Mikael Beuthe of the Royal Observatory of Belgium, modeled the icy shells of Dione and Enceladus using gravity data gathered by NASA’s Saturn-orbiting Cassini spacecraft during its various flybys of the satellites.
Similar simulations performed by other researchers in the past have suggested that Dione is sea-free and that Enceladus’ ocean is buried deep. But Beuthe and his colleagues added a new wrinkle into their models.
“As an additional principle, we assumed that the icy crust can stand only the minimum amount of tension or compression necessary to maintain surface landforms,” Beuthe said in the same statement. “More stress would break the crust down to pieces.”
The team’s results indicate that Enceladus’ ocean is close to the surface, especially near the moon’s south pole — which makes sense, because geysers blast water ice and other material deep into space from this region.
The simulations also suggest Dione has a vast ocean tens of kilometers deep, buried under many miles of ice. This ocean has also probably existed for the moon’s entire history, meaning there has potentially been plenty of time for life to take root and evolve beneath Dione’s battered, icy shell, researchers said.
The new study was published online this week in the journal Geophysical Research Letters.
The skeleton of the Milky Way galaxy is coming into focus: A group of researchers recently dug up a cache galactic “bones” using a method that could answer key questions about these objects.
Galactic “bones” are long, cold, dense filaments of gas that have been discovered running through the center of the Milky Way’s spiral arms. But many other filaments have also been found in the fringes of the galactic arms, or in between them, prompting questions about where these features form.
The new paper reports the identification of 54 galactic filaments, nine of which have been previously identified. This is the first census of a large portion of the galaxy, according to the authors of the new work. The team used a computer algorithm to identify the filaments (previous investigations have searched for these filaments “by eye.”). The authors say the method can help them begin to answer questions about how the filaments formed, how they affect the growth and development of the galaxy, and what happens to them over time.
In 2012, a group of scientists at the Harvard Smithsonian center for Astrophysics (CfA) announced that a cold, dense thread of gas called “Nessie” was actually running straight through the center of one of the Milky Way galaxy’s four main spiral arms. The arms are made up of a sparser collection of gas, dust, stars and other cosmic objects (that could perhaps be considered more “flesh” than the bones). Nessie, which is at least 260 light-years long, was already known to scientists, but no one realized its apparent connection to the spiral arm.
The discovery raised questions about Nessie’s formation: Could the gravitational weight of the arm have formed this “bone”? Did the entire galaxy have a skeleton running through it? Since that discovery, a few other studies have identified a handful of other filaments; while some seem to have definite associations with the structure of the galaxy, some lie in between the arms.
The problem with trying to answer questions about the galactic bone formation is that there haven’t been enough filaments to conduct a comprehensive study, according to Ke Wang, an astronomer with the European Southern Observatory and lead author on the new paper.
With only a small sample of bones to study, it’s difficult to figure out if a particular property is unique to one filament or characteristic of filaments in general. The new study further emphasizes that there is actually tremendous variety among these filaments, and not just their location in the galaxy, Wang told Space.com. The new paper also identifies filaments that are shaped like the letter C, some like the letter S, some like the letter L, and still others like the letter X. What’s more, some of these filaments were “wiggling” and “twisting,” Wang said.
In order to do a characteristic study of the galactic filaments, Wang and his colleagues set out to complete the first large-scale census of the galaxy, and identify as many of these features as possible.
The team built a computer program inspired by something called a “minimum tree spanning” algorithm, which was invented back in the 1920s, and used today to optimize networks, including roads and water pipe systems, Wang told Space.com. The new program looks through a data set that has identified single points in the galaxy that feature the kind of cold, dense gas that defines the filaments. The program then tries to show that groups of those points are connected and make up a single structure.
This first survey used data collected by the Caltech Submillimeter Observatory 10 meter (32.8) telescope, which covered nearly half the galactic plane, as well as data from the Spitzer Space Telescope, Wide-field Infrared Survey Explorer (WISE), and the Arizona Radio Observatory.
The filaments identified in the new paper are between 10 and 276 of parsecs long, where one parsec is about 3.2 light-years, or about 18 trillion miles — in other words, these features are massive. (At 260 light-years long, Nessie is about 79 parsecs). The team identified 54, in a region that covers almost half the galactic plane. In the paper, the authors speculate that there are about 200 filaments of about this size in the entire galaxy.
“By revealing a relatively complete (in the searched region which is about half the Galactic plane) and a statistically significant sample, we are now confident with the statistics,” Wang said in an email. “We find that most large filaments concentrate along major spiral arms, but only about 30% of them run along the center of spiral arms.” Wang defines “bones” as those that lie in the center of a galactic arm.
“[The astrophysical community is] really at the start of revealing the whole population of these kinds of filaments in the entire galaxy,” Wang told Space.com
The new cache of galactic filaments identified by Wang and his team seems to have only opened up more questions about these cosmic objects. While some previous studies have shown that the bones can be found preferentially inside the galactic arms, others have shown that they form preferentially outside the arms, Wang said. But, previous studies only had a few filaments to study, he said. (He noted that various studies have also provided slightly different definitions of what constitutes a galactic filament).
So right now, scientists don’t know how the filaments form of why about 30% of them are showing up in the middle of galactic arms. Wang said scientists have hypothesized that the filaments could be formed by the “differential rotation of of materials in the galactic disk,” by turbulence in the interstellar medium, by magnetic fields, or some combination of factors.
“With the observations so far, including ours and other teams’ work, we are now at the starting of answering this question,” Wang said. “The community is excited about these large filaments, and there are more ongoing observational and theoretical works. I think in a few years’ time we may have an answer.”
Meteorites that crashed onto Earth billions of years ago may have provided the phosphorous essential to the biological systems of terrestrial life.
The meteorites are believed to have contained a phosphorus-bearing mineral called schreibersite, and scientists have recently developed a synthetic version that reacts chemically with organic molecules, showing its potential as a nutrient for life.
Phosphorus is one of life’s most vital components, but it often goes unheralded. It helps form the backbone of the long chains of nucleotides that create RNA and DNA; it is part of the phospholipids in cell membranes; and is a building block of the coenzyme used as an energy carrier in cells, adenosine triphosphate (ATP).
Yet the majority of phosphorus on Earth is found in the form of inert phosphates that are insoluble in water and are generally unable to react with organic molecules. This appears at odds with phosphorus’ ubiquity in biochemistry, so how did phosphorus end up being critical to life?
In 2004, Matthew Pasek, an astrobiologist and geochemist from the University of South Florida, developed the idea that schreibersite [(Fe, Ni)3P], which is found in a range of meteorites from chondrites to stony-iron pallasites, could be the original source of life’s phosphorus. Because the phosphorus within schreibersite is a phosphide, which is a compound containing a phosphorus ion bonded to a metal, it behaves in a more reactive fashion than the phosphate typically found on Earth.
Finding naturally formed schreibersite to use in laboratory experiments can be time-consuming when harvesting from newly fallen meteorites and expensive when buying from private collectors. Instead, it has become easier to produce schreibersite synthetically for use in the laboratory.
Natural schreibersite is an alloy of iron, phosphorous and nickel, but the common form of synthetic schreibersite that has typically been used in experiments is made of just iron and phosphorus, and is easily obtainable as a natural byproduct of iron manufacturing. Previous experiments have indicated it reacts with organics to form chemical bonds with oxygen, the first step toward integrating phosphorous into biological systems.
However, since natural schreibersite also incorporates nickel, some scientific criticism has pointed out that the nickel could potentially alter the chemistry of the mineral, rendering it non-reactive despite the presence of phosphides. If this were the case, it would mean that the experiments with the iron-phosphorous synthetic schreibersite would not represent the behavior of the mineral in nature.
“There was always this criticism that if we did include nickel it might not react as much,” said Pasek.
Pasek and his colleagues have addressed this criticism by developing a synthetic form of schreibersite that includes nickel.
In a recent paper published in the journal Physical Chemistry Chemical Physics, Pasek and lead author and geochemist Nikita La Cruz of the University of Michigan show how a form of synthetic schreibersite that includes nickel reacts when exposed to water. As the water evaporates, it creates phosphorus-oxygen (P-O) bonds on the surface of the schreibersite, making the phosphorus available to life. The findings seem to remove any doubts as to whether meteoritic schreibersite could stimulate organic reactions.
“Biological systems have a phosphorus atom surrounded by four oxygen atoms, so the first step is to put one oxygen atom and one phosphorous atom together in a single P-O bond,” Pasek explained.
Terry Kee, a geochemist at the University of Leeds and president of the Astrobiology Society of Britain, has conducted his own extensive work with schreibersite and, along with Pasek, is one of the original champions of the idea that it could be the source of life’s phosphorus.
“The bottom line of what [La Cruz and Pasek] have done is that it appears that this form of nickel-flavored synthetic schreibersite reacts pretty much the same as the previous synthetic form of schreibersite,” Kee said.
Pasek described how meteors would have fallen into shallow pools of water on ancient Earth. The pools would then have undergone cycles of evaporation and rehydration, a crucial process for chemical reactions to take place. As the surface of the schreibersite dries, it allows molecules to join into longer chains. Then, when the water returns, these chains become mobile, bumping into other chains. When the pool dries out again, the chains bond and build ever larger structures.
“The reactions need to lose water in some way in order to build the molecules that make up life,” said Pasek. “If you have a long enough system with enough complex organics, then, hypothetically, you could build longer and longer polymers to make bigger pieces of RNA. The idea is that at some point you might have enough RNA to begin to catalyze other reactions, starting a chain reaction that builds up to some sort of primitive biochemistry, but there’s still a lot of steps we don’t understand.”
Demonstrating that nickel-flavored schreibersite, of the sort contained in meteorites, can produce phosphorus-based chemistry is exciting. However, Kee said further evidence is needed to show that the raw materials of life on Earth came from space.
“I wouldn’t necessarily say that the meteoric origin of phosphorus is the strongest idea,” he said. “Although it’s certainly one of the more pre-biotically plausible routes.” [Fallen Stars: A Gallery of Famous Meteorites]
Despite having co-developed much of the theory behind schreibersite with Pasek, Kee pointed out that hydrothermal vents could rival the meteoritic model. Deep-sea volcanic vents are already known to produce iron-nickel alloys such as awaruite, and Kee says that the search is now on for the existence of awaruite’s phosphide equivalent in the vents: schreibersite.
“If it could be shown that schreibersite can be produced in the conditions found in vents — and I think those conditions are highly conducive to forming schreibersite — then you’ve got the potential for a lot of interesting phosphorylation chemistry to take place,” said Kee
Pasek agreed that hydrothermal vents could prove a good environment to promote phosphorus chemistry, with the heat driving off the water to allow the P-O bonds to form. “Essentially it’s this driving off of water that you’ve got to look for,” he added.
Pasek and Kee both agreed that it is possible that both mechanisms — the meteorites in the shallow pools and the deep-sea hydrothermal vents — could have been at work during the same time period and provided phosphorus for life on the young Earth. Meanwhile David Deamer, a biologist from the University of California, Santa Cruz, has gone one step further by merging the two models, describing schreibersite reacting in hydrothermal fields of bubbling shallow pools in volcanic locations similar to those found today in locations such as Iceland or Yellowstone National Park.
Certainly, La Cruz and Pasek’s results indicate that schreibersite becomes more reactive as the environment in which it exists gets warmer.
“Although we see the reaction occurring at room temperature, if you increase the temperature to 60 or 80 degrees Celsius [140 or 176 degrees Fahrenheit], you get increased reactivity,” said Pasek. “So, hypothetically, if you have a warmer Earth, you should get more reactivity.”
One twist to the tale is the possibility that phosphorus could have bonded with oxygen in space, beginning the construction of life’s molecules before ever reaching Earth. Schreibersite-rich grains coated in ice and then heated by shocks in planet-forming disks of gas and dust could potentially have provided conditions suitable for simple biochemistry. While Pasek agreed with that idea in principle, he said he has “a hard time seeing bigger things like RNA or DNA forming in space without fluid to promote them.”