Astronomers may have discovered an exoplanet that has found the elixir to planetary youth, knocking billions of years off its age.
Until now, stellar rejuvenation has been pure conjecture, but after studying a white dwarf star called PG 0010+280, it turns out that one very interesting explanation for an excess in detected infrared radiation may be down to the presence of an exoplanet that was given a facelift.
White dwarf stars are the remnant husks of stars that have died. Eventually, when a star like our sun runs out of fuel, puffing up into a red giant star, its layers of plasma will be blasted into space by powerful, suicidal stellar winds. This will create a beautiful planetary nebula with a small, dense white dwarf in the core. [The Strangest Alien Planets (Gallery)]
But what happens to all this material that has been jetted into space? Well, as the theory goes, some of it may fall onto massive gaseous exoplanets orbiting far away from the star. Before their star ran out of hydrogen and puffed up into a red giant, that exoplanet was aging gracefully, cooling down billions of years after formation.
The situation changed, however, when its atmosphere became bulked up with stellar plasma, re-heating the massive world and making it appear much younger than it really is.
“When planets are young, they still glow with infrared light from their formation,” Michael Jura of the University of California, Los Angeles, co-author of the study published in The Astrophysical Journal, said in a statement. “But as they get older and cooler, you can’t see them anymore. Rejuvenated planets would be visible again
White dwarf studies have gone into overdrive in recent years after astronomers realized they could study white dwarf atmospheres to find the pulverized remains of asteroids and planetary bodies. When passing into the white dwarf phase, the planets and asteroids that are in orbit may drift too close to the powerful tidal forces near that star, and become shredded.
During a survey of white dwarfs for the chemical signatures of these pulverized planetary remains, undergraduate student Blake Pantoja, who was studying at UCLA at the time, came across something weird in data from NASA’s Wide-field Infrared Survey Explorer, and follow-up study by NASA’s Spitzer Space Telescope confirmed the strange excess in infrared light coming from PG 0010+280. At first the team assumed the excess was radiating from a disk of the pulverized remains of asteroids that may have been present — but the data didn’t fit with this explanation.
So two possible explanations remain: perhaps the excess is being generated by a companion brown dwarf (a failed star) or, potentially, a rejuvenated planet, heated up by an influx of stellar matter.
“I find the most exciting part of this research is that this infrared excess could potentially come from a giant planet, though we need more work to prove it,” said Siyi Xu of UCLA and the European Southern Observatory in Germany. “If confirmed, it would directly tell us that some planets can survive the red giant stage of stars and be present around white dwarfs.”
To confirm if this infrared excess is indeed a rejuvenated planet, astronomers are looking to NASA’s James Webb Space Telescope (that is planned for a 2018 launch) for help. Although tantalizing, we’ll have to wait for confirmation as to what this signal is.
The bizarre find is the first of its kind ever discovered by astronomers. The strange, cometlike planet, known as GJ 436b, is orbiting a red dwarf star and is about 22 times as massive as Earth. Astronomers detected the giant gas cloud around the planet using NASA’s Hubble Space Telescope and Chandra X-ray Observatory.
“I was astonished by the mere size of the cloud of gas escaping from the planet,” said study lead author David Ehrenreich, an astronomer at the observatory of the University of Geneva in Switzerland.
GJ 436b, located about 33 light-years from Earth in the constellation Leo, is a kind of world known as a warm Neptune. Such planets, at about 10 to 20 times the mass of Earth, are about the mass of “cold Neptunes” such as Uranus — and, naturally, Neptune — but they are as close, or closer, to their stars than Mercury is to our sun. With an orbit of only about 3 million miles (4.8 million kilometers), “GJ 436b is 33 times closer to its star than Earth is to the sun, and 13 times closer than Mercury,” Ehrenreich told Space.com.
The cloud of gas around GJ 436b, made up mostly of hydrogen, has a circular head that surrounds GJ 436b, and a tail trailing behind the planet. The diameter of the head is about 1.8 million miles (3 million km), or five times the width of the host star, which is about half that of the sun, Ehrenreich said. The length of the tail is uncertain, because the research team’s observations do not cover it entirely, but their computer models suggest it could be about 9.3 million miles (15 million km) long.
Although prior research has predicted that other gas giants should be blowing off cometlike tails, based on how hot they must be due to their proximity to their stars, “GJ 436b is the first planet for which a cometlike tail is confidently detected,” Ehrenreich said. (A previous study revealed indirect evidence of a rocky world that appears to be disintegrating around its host star, creating a cometlike tail of material behind the planet. That study used data from NASA’s Kepler space telescope, which observed scattering of the light from the planet’s host star.)
The scientists estimated that GJ 436b is currently blowing off up to 1,000 tons of gas per second. This means that GJ 436b is currently losing about 0.1 percent of its atmosphere every billion years, which is far too slow a rate to deplete its atmosphere in the lifetime of its parent red dwarf star. However, when the star was more active in its infancy, the researchers estimated that GJ 436b could have lost 10 percent or more of its atmosphere during its first billion years.
Recently, another team of researchers suggested that GJ 436b might possess a helium-rich sky depleted of hydrogen. “However, in order to be really hydrogen-poor and helium-rich, the atmosphere of GJ 436b should have represented a very small fraction of the planet['s] initial mass, around one-thousandth,” Ehrenreich said. “In such a case, the whole atmosphere would have been gone today, which as we measure is not the case.”
Ehrenreich noted that the Kepler spacecraft, as well as NASA’s upcoming TESS space mission and the European Space Agency’s future CHEOPS and PLATO spacecraft “are poised to find thousands of system like GJ 436 in the coming years.” This suggests that many other planets with cometlike tails could soon be discovered.
The scientists now plan to investigate less massive planets, such as “super-Earths” and “mini-Neptunes” to see if they might also have puffy atmospheres and cometlike tails.
“We’re going to study one such object in the course of next year with Hubble, and have proposed to observe several more,” Ehrenreich said.
The scientists detailed their findings online today (June 24) in the journal Nature.
Globular clusters are densely packed collections of ancient stars. Roughly spherical in shape, they contain hundreds of thousands, and sometimes millions, of stars. Studying them helps astronomers estimate the age of a region of space or figure out where the center of a galaxy lies.
There are about 150 known globular clusters in the Milky Way galaxy, according to Georgia State University’s HyperPhysics website. All are estimated to be at least 10 billion years old, and contain some of the oldest stars in the galaxy. The clusters likely formed very early, before the galaxy flattened into a spiral disc.
Some globular clusters, such as Messier 13 (M13) in the constellation Hercules, can be seen with the naked eye. They are pretty to look at, but it was only after telescopes were invented that they began to shine in astronomy circles. With telescopes, it was possible to peer closer at the stars within these clusters. They are mostly low-mass red stars and intermediate-mass yellow stars — none of them greater than 0.8 solar masses, according to HyperPhysics. [Related: How to See the Great Hercules Cluster of Stars]
Some other general observations of globular clusters, according to Pennsylvania State University: they are found in every direction in the sky, the density of stars in a globular cluster is much greater than the density of stars around the sun, and the clusters are not found to contain any gas. The abundance of any elements heavier than helium is only 1 percent to 10 percent of the abundance of the same elements in the sun.
The first two officially discovered and named clusters in the telescopic age were M22 (in Sagittarius, in 1665) and Omega Centauri in Centaurus, according to Encyclopedia Britannica. Like M13, Omega Centauri is also visible to the naked eye, but was not classified as a globular cluster until examined by a telescope.
M22 was a notable find not only for its early discovery, but also for the ages of the stars within it. The stars range between 12 billion and 13 billion years old, which date it close to the formation of the universe 13.8 billion years ago, according to the European Space Agency.
“[Its discovery] is not so surprising as it is one of the brightest globular clusters visible from the Northern Hemisphere, located in the constellation of Sagittarius, close to the Galactic Bulge — the dense mass of stars at the center of the Milky Way,” according to the ESA.
It’s tricky to find M13 with the naked eye, but if the skies are especially dark and clear it is possible, ESA wrote. Omega Centauri and M13 both were discovered by Edmund Halley in the 18th century; Halley is best known as the astronomer who figured out that Halley’s Comet returns to Earth periodically.
“As Halley wrote: ‘This is but a little Patch, but it shews it self to the naked Eye, when the Sky is serene and the Moon absent,’” ESA wrote. Centuries later, M13 was also the target of the Arecibo radio telescope message to extraterrestrials in 1974.
In 1917 astronomer Harlow Shapley, studying Cepheids, a certain kind of variable star within each cluster, noted that these stars shine at a predictable brightness depending on distance from the receiver. He was able to calculate the distances to these stars, which revealed the galactic center is in the constellation Sagitarrius.
Shapley also noted that globular clusters are arranged symmetrically around the galaxy, but that they were arranged equally above and below the galactic plane, seeming to avoid the plane itself.
Shapley’s model greatly increased the size of the galaxy and pushed the solar system — and humanity — farther from the center. However, Shapley believed that the universe was “a single, enormous, all-encompassing unit,” according to the American Institute of Physics. Building on Shapley’s research, Edwin Hubble found globular clusters that were even more distant — as much as 10 times farther — and that lay beyond the Milky Way, in other galaxies. Presented with Hubble’s evidence, Shapley reportedly was glad to see his theories refuted.
The namesake Hubble Space Telescope has been particularly productive when it comes to looking at globular clusters, because they are not obscured by Earth’s atmosphere. With an absence of star twinkling, the stars come into sharper view. This makes it easier to calculate their distance and properties. In one area of the Virgo constellation alone, NASA wrote in a release in 2008, the telescope revealed more than 11,000 globular clusters.
At the same time, the telescope gave hints as to why M87 (which is embedded in the same region) has more star clusters than what would be expected. This is because M87 and clusters like it were created in very dense areas of the universe that provided more favorable conditions for star birth, which takes place in clouds of gas called nebulae.
Hubble also destroyed a long-standing perception among astronomers that globular clusters always contain stars of about the same age. The most massive globular clusters likely grab on to any material that is nearby and birth new generations of stars, NASA wrote in a past release.
What does this mean? Well, it could be that each of the dozens of clusters studied are packed with dark matter or may even by hiding a massive black hole, but neither of the explanations make any sense.
Globular star clusters are ancient ensembles of thousands of stars that can be found orbiting galaxies like our Milky Way. Their study is critical to help us understand how galaxies on the whole evolve as the stars they are known to contain are often as old as the galaxies they orbit.
“Globular clusters and their constituent stars are keys to understanding the formation and evolution of galaxies. For decades, astronomers thought that the stars that made up a given globular cluster all shared the same ages and chemical compositions — but we now know that they are stranger and more complicated creatures,” said Matt Taylor, a PhD student at the Pontificia Universidad Catolica de Chile, Santiago, Chile, and lead author of the study.
Using the FLAMES instrument on the ESO’s Very Large Telescope at the Paranal Observatory in Chile, Taylor and his team surveyed 125 of the around 2,000 globular clusters in orbit around Centaurus A and gauged their masses. Usually, the mass of a globular cluster can be derived by measuring their brightness. The brighter the cluster, the more stars it has and the more massive it is.
Naturally, the researchers’ suspicions are focusing on these clusters amassing a reservoir of dark matter. But globular star clusters are not thought to contain significant quantities of invisible stuff. Perhaps, therefore, these islands of stars have massive black holes in their cores, or maybe a massive graveyard of other stellar corpses, like the burnt-out husks of stars like neutron stars? For now, where this extra baggage comes from remains mystery.
“Our discovery of star clusters with unexpectedly high masses for the amount of stars they contain hints that there might be multiple families of globular clusters, with differing formation histories. Apparently some star clusters look like, walk like, and smell like run-of-the-mill globulars, but there may quite literally be more to them than meets the eye,” added co-author Thomas Puzia, also at the Pontificia Universidad Catolica de Chile.
To widen the search, the researchers are now carrying out a survey of other globular clusters around other galaxies in the hope of finding more of these mysterious “dark clusters.”
“We have stumbled on a new and mysterious class of star cluster! This shows that we still have much to learn about all aspects of globular cluster formation. It’s an important result and we now need to find further examples of dark clusters around other galaxies,” concluded Taylor.
Scientists have spotted a kind of young birthplace for stars in telescope observations for the first time. The newborn star-forming clump in deep space is a giant cloud of gas that may have given birth to dozens of stars a year, researchers say.
The discovery could shed light on galaxy formation in the early universe, when star formation was at its peak, scientists added.
Stars formed at the greatest speed when the universe was between 3 billion and 4 billion years old, a time when galaxies possessed massive star-forming clumps. It was a mystery as to how these clumps arose, since astronomers have not yet seen them form. Now scientists have uncovered a young star-forming clump, one less than 10 million years old, which could help solve that mystery.
“Clumps have been extensively studied so far, but for the first time, we have observed a newly born one,” study lead author Anita Zanella, an astronomer at the French Alternative Energies and Atomic Energy Commission, told Space.com.
Until now, studied clumps usually contained stars more than 100 million years in age, meaning the clumps were correspondingly old, Zanella said. She and her colleagues instead looked for relatively young stars, which in turn could reveal the presence of relatively young clumps.
The astronomers used NASA’s Hubble Space Telescope to discover the clump, which is located in a galaxy nearly 10.4 billion light-years away, dating back to when the universe was only about 3.3 billion years old. The scientists calculated that the clump was about 3,000 light-years wide and more than 1 billion times the mass of the sun.
Based on the light detected from the clump, the researchers estimated that the gas cloud produced “the equivalent of 32 stars with the mass of the sun every year,” Zanella said. This accounted for nearly 40 percent of the stars produced in the galaxy hosting the clump. All in all, “the clump formed stars 10 times more efficiently than normal galaxies,” Zanella said.
By analyzing the initial phase of clump formation, this research favors a theory that suggests star-forming clumps begin as giant, dense pockets in highly turbulent, gas-rich matter in young galaxies. The researchers’ preliminary estimates suggest that giant clumps such as the one they discovered live about 500 million years.
This research suggests that giant clumps are not rapidly destroyed by the energetic winds from the stars they created as some had previously argued. Instead, the clumps could live long enough to migrate toward the centers of galaxies. “Clump migration could thus explain why and how galaxy bulges form,” Zanella said.
Future research with other telescopes could help discover additional young star-forming clumps, yielding insights on galaxy formation, Zanella said. That research could possibly involve the Atacama Large Millimeter Array in northern Chile and the James Webb Space Telescope, whose launch is planned for the end of 2018.
The results, outlined in a new study, show that the disk is about 60 percent larger than previously thought. Not only do the results extend the size of the Milky Way, they also reveal a rippling pattern, which raises intriguing questions about what sent wavelike fluctuations rippling through the disk.
The researchers said the likely culprit was a dwarf galaxy. It might have plunged through the Milky Way’s center long ago, sparking the rippling patterns astronomers have now detected for the first time.
Roughly 15 years ago, Heidi Newberg, an astronomer at the Rensselaer Polytechnic Institute in New York, and her colleagues found a group of stars beyond the disk’s outermost edge. The so-called Monoceros Ring is about 60,000 light-years from the galactic center (just beyond where the disk was thought to end at 50,000 light-years).
Over the years, astronomers were divided into two camps regarding the origins of the ring. Some argued that it was simply a tidal stream: The debris of a dwarf galaxy that fell into the Milky Way and was stretched in the process. Others argued that the ring is a part of the disk. The issue, however, is that the ring is slightly above the plane of the disk. So astronomers in the latter camp attributed that to the fact that the disk flares up toward the edge.
Enter Yan Xu, an astronomer at the National Astronomical Observatories of China. Xu, Newberg and colleagues took a second look at the problem using data from the Sloan Digital Sky Survey. With improved data compared to previous studies, they found four total structures in and just outside what is currently considered the Milky Way’s outer disk. The third structure was the highly debated Monoceros ring, and the fourth structure was the Triangulum Andromeda Stream, located 70,000 light-years from the galactic center.
All four structures alternated with respect to the disk. They went from above it, to below it, to above it, to below it. Newberg, who was in the tidal stream camp, was surprised that the ring and three other structures were actually a part of an oscillating disk.
“We didn’t know how a disk could go up and down,” said Newberg. Luckily, computer simulations by various teams showed that a dwarf galaxy falling into the Milky Way might create a similar pattern. “When it goes through, it can disturb the disk just like a pebble disturbs water in a puddle,” said Newberg. “And that wave can propagate through the disk from that event.”
This new picture makes sense, said Newberg. It even matches observations of the gases in the disk, which have long been observed as rippled. But the implications extend far beyond a corrugated disk.
“If it’s true that the Monoceros Ring and the Triangulum Andromeda structure are part of this oscillatory pattern, then the stellar disk goes out way further than the textbook tells us it ought to be,” said Newberg. Instead of extending nearly 100,000 light-years from one side to the other, it would be more like 160,000 light-years wide.
This brings the Milky Way’s size up to that of Andromeda. The Milky Way’s small radius in comparison to Andromeda’s larger radius has always puzzled astronomers, because the two galaxies have roughly the same mass.
The team plans to further map the rippled disk of Earth’s galaxy and better match their results to models.
The study was detailed in the March 10 edition of the Astrophysical Journal.
The remains of thousands of stars might exist in a vast graveyard near the giant black hole at the heart of our Milky Way galaxy, a region where dead stars feed on companions like zombies and unleash X-ray “howls,” researchers say.
Scientists have long thought that a monster black hole with the mass of 4.3 million suns, named Sagittarius A* (pronounced Sagittarius A star), lurks at the heart of the Milky Way. Recently, astronomers discovered that a surprising number of young, massive stars exist within a few dozen light-years of this black hole.
“These young, massive stars are puzzling because when we think about how stars form from clouds of gas that gravitationally collapse in on themselves, it’s hard to figure how these clouds could have survived long enough to form stars, given the intense gravitational pull of the supermassive black hole that’s so close to them,” lead study author Kerstin Perez, an astrophysicist now at Columbia University in New York, told Space.com.
To learn more about the mysterious center of the galaxy, scientists have focused on X-rays, whose the wavelengths and energies of can shed light on the kinds of activities take place at the galactic center. Previous research has suggested that relatively weak, “soft” X-rays from the galactic core mostly came from white dwarfs — the dim, fading remnants of stars much like the sun — that are accumulating or accreting matter onto themselves.
Now, using NASA’s NuSTAR X-ray space telescope, astronomers have the best pictures yet of the sources of stronger, “hard” X-rays from the area 100 or so light-years away from the Milky Way’s central black hole. However, the nature of these X-ray sources remains a mystery. In a statement, NASA described the signals as possible “screams” from zombie stars.
“As of right now, we haven’t solved any mysteries about the galactic center — we just launched a new, big mystery,” Perez said, who conducted this research while at Columbia University in New York.
Mystery in the Milky Way
The researchers currently have four possible explanations for these hard X-rays; three of those theories involve different kinds of stellar remnants. However, each of these options presents difficulties, Perez said.
One possible explanation points to what is known as an intermediate polar, which is a binary system made up of a white dwarf with a powerful magnetic field that is accreting matter onto itself from a companion star. Intermediate polars are cataclysmic variables, meaning they can brighten in sharp outbursts. [Latest Black Hole Images from NuSTAR Telescope]
If these powerful X-ray sources are intermediate polars, their presence would be puzzling. For example, if intermediate polars are the source of all this radiation, the researchers estimate that 1,000 to 10,000 intermediate polars might exist in the galactic center — about 1,000 times more than observers might have expected.
In addition, the energy of these X-rays suggests that each of the white dwarfs in these intermediate polars has a mass almost as heavy as the sun’s. That is substantially heavier than any intermediate polars that have previously been seen in the galactic center, which have masses that are about half that of the sun’s. “If these are intermediate polars, why are they so heavy?” Perez said. “Did they form from denser clouds of gas, or did they accrete more matter?
Alternatively, these hard X-ray sources might be millisecond pulsars, which are highly magnetic neutron stars that spin about 1,000 times per second. A neutron star is a dense, city-sized stellar remnant born from the explosive death of a larger star. However, when astronomers look at the galactic center in other wavelengths of light besides X-rays, “we don’t see as many millisecond pulsars as we would need to explain these hard X-rays,” Perez said. “Still, prior research has suggested there may be millisecond pulsars hiding in the galactic center.”
In a third theory, these hard X-rays might come from low-mass X-ray binaries. In this scenario, one of the pair of binary stars is either a black hole or a neutron star, while its companion is either a regular star like the sun, an old star such as a red giant or a stellar remnant such as a white dwarf.
However, “low-mass X-ray binaries are inherently unstable, mostly lasting on time scales of 10 years or so,” Perez said. “Maybe there’s something wacky about the environment of the galactic center that makes them more stable.”
One more scenario
The last possibility is that these powerful X-rays do not come from stellar remnants at all, but rather are the results of outbursts of high-energy particles known as cosmic rays, which are coming from the Milky Way’s supermassive black hole and slamming into dense clouds of gas and dust.
“Prior research has postulated that large flares happening on the order of 100 years could travel from the Milky Way’s supermassive black hole and travel through clouds, lighting them up in X-rays,” Perez said. “The difficulty with that idea is that the X-rays don’t match where material is known to be around the galactic center and models that exist right now of how cosmic rays propagate.”
To help solve the mystery behind these powerful X-rays, Perez and her colleagues hope to use NuSTAR to look at the galactic center within the coming year. “Maybe we’ll be able to narrow down these four possibilities,” Perez said.
The eruption was first recognized in 2014, when astronomer Emily Safron, who had just graduated from the University of Toledo in Ohio with her bachelor’s degree, noticed an object in her data that was brightening dramatically over time.
The finding not only marks the earliest eruption ever recorded but also sheds light on how stars grow to be so massive so quickly, researchers reported in a new study.
Stars are born within the clouds of dust and gas scattered throughout most galaxies. Turbulence within the clouds gives rise to knots that begin to collapse under their own weight. The knot quickly becomes a protostar, and continues to grow denser and hotter. Eventually, the central protostar becomes surrounded by a dusty disk roughly equal to it in mass. Astronomers call this a “Class 0″ protostar.
Although a Class 0 protostar has yet to generate energy by fusing hydrogen into helium deep in its core, it still shines, albeit faintly. As the protostar collapses further and accumulates more material from the disk of gas and dust surrounding it, it releases energy in the form of visible light. But this light is often blocked by the surrounding gas and dust.
Studies have shown, however, that the light heats up the dust around the protostar, causing it to give off a faint glow that can then be detected by infrared observatories, like the Spitzer Space Telescope. In this way, astronomers can detect a protostar’s presence via the faint glow of its surrounding dust clouds.
But in 2006, a Class 0 protostar in the constellation Orion, dubbed HOPS 383, acted out of the norm and brightened dramatically. Over two years, it became 35 times brighter. In addition, the most recent data available, from 2012, show that the eruption isn’t fading.
“HOPS 383 is the first outburst we’ve ever seen from a Class 0 object, and it appears to be the youngest protostellar eruption ever recorded,” William Fischer, a postdoctoral researcher at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, said in a statement from NASA.
The new study of HOPS 383 was completed using data from the Spitzer telescope in conjunction with the European Space Agency’s Herschel Space Observatory, as part of a project called the Herschel Orion Protostar Survey (HOPS).
Scientists were also surprised by the length of the eruption, thus making HOPS 383 even more intriguing.
“An outburst lasting this long rules out many possibilities, and we think HOPS 383 is best explained by a sudden increase in the amount of gas the protostar is accreting from the disk around it,” Fischer said.
It’s likely that instabilities in the disk lead to episodes in which large quantities of material flow onto the protostar, Fischer said. This causes the star to develop a hotspot on its surface, which, in turn, heats up the disk and brightens it dramatically.
Such episodes have been observed in older protostars and have been theorized to occur in younger protostars. These episodes could help explain why protostars are dimmer than scientists think they should be, according to the study.
To build up the bulk of a typical star over a short time period, protostars should be brighter, as they should accumulate more material from the surrounding disk faster. Because these protostars are so faint, some astronomers suspect that they could also build up the bulk of a typical star by randomly munching on a lot of material from the surrounding disk, as noted in the study. If that were the case, then astronomers should regularly observe these flashes.
The team will continue to monitor HOPS 383 and has submitted a proposal to use NASA’s Stratospheric Observatory for Infrared Astronomy (SOFIA), the world’s largest flying telescope.
The study was published in the Feb. 10 edition of the Astrophysical Journal.
Supermassive black holes loom in the centers of the majority of massive galaxies. Some of these black holes, like the one in the Milky Way’s center, lie dormant. Others (so-called quasars) actively chow down on gas, causing them to radiate like brilliant beacons of light. They can therefore be seen from across the universe.
Although these monsters clearly accrete huge amounts of matter, some material escapes. It’s flung out into space at close to the speed of light in a jet of plasma. Astronomers don’t understand the physical mechanism at play here, but think it has to do with a strong magnetic field close to the black hole itself.
Luckily, magnetic field lines leave an imprint on any light that passes through them. The magnetic field will twist light so that it is circularly polarized, meaning the electric and magnetic fields rotate continuously as the wave moves, in a corkscrew motion. The stronger the magnetic field, the stronger this imprint.
Until now, only weak magnetic fields located several light-years from the black hole have been caught on camera via this twisting of light. But by looking at higher energies, like the ones visible with ALMA, astronomers can probe more powerful magnetic fields, which lie closer to their black hole counterparts.
“These results, and future studies, will help us understand what is really going on in the immediate vicinity of supermassive black holes,” Muller said in the statement.
Despite the harsh environment created by the monster black hole lurking in the center of the Milky Way galaxy, new observations show that stars — and, potentially, planets — are forming just two light-years away from the colossal giant.
Bright and massive stars were spotted circling the 4-million-solar-mass behemoth more than a decade ago, sparking a debate within the astronomy community. Did they migrate inward after they formed? Or did they somehow manage to form in their original positions?
Most astronomers had said the latter idea seemed far-fetched, given that the black hole wreaks havoc on its surroundings, often stretching any nearby gas into taffylike streamers before it has a chance to collapse into stars. But the new study details observations of low-mass stars forming within reach of the galactic center. The findings lend support to the argument that “adult” stars observed in this region formed near the black hole.
The new evidence for ongoing star formation near the black hole is “a nail in the coffin” for the theory that the stars form in situ, said lead author Farhad Yusef-Zadeh, of Northwestern University. The observations, if accurate, make it unlikely that the stars migrated from elsewhere, the researchers said.
Birth near a black hole
Stars are born within clouds of dust and gas. Turbulence within these clouds give rise to knots that begin to collapse under their own weight. The knots grows hotter and denser, rapidly becoming protostars, which are so-named because they have yet to start fusing hydrogen into helium.
But a protostar can rarely be seen. It has yet to generate energy via nuclear fusion, and any faint light it does produce is often blocked by the disk of gas and dust still surrounding it.
So, when Yusef-Zadeh and his colleagues used the Very Large Array in New Mexico to scan the skies near the central supermassive black hole, they didn’t spot the protostars but rather the disks of gas and dust surrounding them.
“You could see these beautiful cometary-shaped structures,” Yusef-Zadeh told Space.com. Intense starlight and stellar winds from previously discovered high-mass stars had shaped these disks into cometlike structures with bright heads and tails. Similar structures (called bow shocks) can be seen anywhere young stars are being born, including the famous Orion Nebula.
There is, of course, one big catch here — and that is that the tidal force on the black hole is so strong that it’s hard to see how these stars would form,” Yusef-Zadeh said. “Many people think that star formation is forbidden near a supermassive black hole. But nature finds a way.”
Astronomers have managed to find a way as well. Over the last decade, they’ve come up with two scenarios, both of which use the nearby black hole to simulate star formation.
In the first scenario, a cloud might break apart in the strong gravitational field and reassemble into a disk that surrounds the black hole. This disk would then form stars in the same way that the disks surrounding young stars form planets. Although this scenario was first proposed in 2005 by Sergei Nayakshin, an astronomer at the University of Leicester in the United Kingdom, it predicts the formation of low-mass stars. Until now, such stars hadn’t been discovered in the galactic center.
In the second scenario, a cloud gets stretched into a taffylike streamer. But as this happens, the gravitational tide from the nearby black hole does two different things. “It disrupts in one direction, but it squeezes in another direction,” Yusef-Zadeh said. It’s this squeezing, or compressing, that would trigger star formation within the long streamer, Yusef-Zadeh added.
Both scenarios explain why stars encircling the monster black hole, called Sagittarius A*, are found in two rings, or disks, as opposed to random placements.
But some astronomers remain cautious.
“The center of our galaxy is a unique and extreme environment very different from our local solar neighborhood and the rest of the Milky Way,” said Jessica Lu, an astronomer at the University of Hawaii’s Institute for Astronomy. It’s therefore crucial that astronomers don’t jump to any conclusions.
“While these bow shocks have similar shapes to protostars seen in the nearby Orion cluster, there are other ways to produce these bow shocks around small clumps of gas,” Lu told Space.com in an email. [The Strangest Black Holes in the Universe]
Some scientists who do think that stars — even low-mass stars — are forming within a few light-years of supermassive black holes are now starting to wonder if planets are forming there, too.
Typically, a disk circling a protostar will break up into clumps of gas and dust that later become full-fledged planets. But in such an extreme environment, the wind from nearby stars (the same winds that are responsible for the cometlike shapes of the disks seen by Yusef-Zadeh and his colleagues), may also steal mass from these disks. Yusef-Zadeh and his colleagues estimate that there could be enough material left in those disks to form planets.
The team plans to use the Atacama Large Millimeter/submillimeter Array (ALMA) in northern Chile to better probe the disks where the planets may form. ALMA’s high sensitivity will reveal the disks’ masses and maybe even any gaps in the disks, which likely result from forming planets.
“We’re just beginning to really learn about this environment,” Yusef-Zadeh said, adding that he’s excited to start picking away at all of the questions the new study has opened.
Small, cold stars known as red dwarfs are the most common type of star in the Universe, and the sheer number of planets that may exist around them potentially make them valuable places to hunt for signs of extraterrestrial life.
However, previous research into planets around red dwarfs suggested that while they may be warm enough to host life, they might also completely dry out, with any water they possess locked away permanently as ice. New research published on the topic finds that these planets may stay wet enough for life after all. The scientists detailed their findings online on November 12 in The Astrophysical Journal Letters.
Red dwarfs, also known as M stars, are roughly one-fifth as massive as the Sun and up to 50 times fainter. These stars comprise up to 70 percent of the stars in the cosmos, and NASA’s Kepler space observatory has discovered that at least half of these stars host rocky planets that are one-half to four times the mass of Earth.
Red dwarf planets are potentially key places to search for life as we know it, not just because there are so many of them, but also because of their incredible longevity. Unlike our Sun, which will die in a few billion years, red dwarfs will take trillions of years to burn through their fuel, significantly longer than the age of the Universe, which is less than 14 billion years old. This longevity potentially gives red dwarfs a great deal more time for life to evolve around them.
Research into whether a distant world might host life as we know it usually focuses on whether or not it has liquid water, since there is life virtually everywhere there is liquid water on Earth, even miles underground. Scientists typically concentrate on habitable zones, the area around a star where it is neither too hot for all its surface water to boil away, nor too cold enough for all its surface water to freeze.
Recent findings suggest that planets in the habitable zones of red dwarf stars could accumulate significant amounts of water. In fact, each planet could possess about 25 times more water than Earth.
The habitable zones of red dwarfs are close to these stars because of how dim they are, often closer than the distance Mercury orbits the Sun. This closeness makes them appealing to astrobiologists, since planets near their stars cross in front of them more often, making them easier to detect than planets that orbit farther away.
However, when a planet orbits very near a star, the star’s gravitational pull can force the world to become “tidally locked” to it. When a planet is tidally locked to its star, it will always show the same side to its star, just as the Moon always shows the same side to Earth. This causes the planet to have one permanent day side and one permanent night side.
The extremes of heat and cold that tidally locked planets experience could make them profoundly different from Earth. For example, prior research speculated the dark sides of tidally locked planets would become so cold that any water there would freeze. Sunlight would make water on the sunlit side evaporate, and this water vapor could get carried by air currents to the night sides, eventually leading to sheets of ice miles thick on the night sides and removing all water from the sunlit sides. Life as we know it probably could not develop on the day sides of such planets. Although they would have sunlight for photosynthesis, they would have no water to serve as the primordial soup for life to swim in.
To see how habitable tidally-locked planets really are, scientists devised a 3D global climate model of planets that simulated interactions between the atmosphere, ocean, sea ice, and land, as well as a 3-D model of ice sheets large enough to cover entire continents. They also simulated a red dwarf with a temperature of about 5,660 degrees Fahrenheit (3,125 degrees Celsius), and investigated whether all the water on these planets would indeed get trapped on their night sides. [The Strangest Alien Planets (Gallery)]
“I’ve been interested in trying to make calculations relevant for M-star planet habitability since being convinced by astronomers that these types of planets will likely be closest (in proximity) to Earth,” said study co-author Dorian Abbot, a geoscientistat the University of Chicago.
For instance, the nearest known star to the Sun, Proxima Centauri, is a red dwarf, and it remains uncertain whether or not it has a planet. The possibility that red dwarf planets might be relatively near to Earth “means that anything geoscientists can tell astronomers about habitability of these planets will be essential for planning future missions.”
The researchers simulated planets of Earth’s size and gravity that experienced between 63 percent and 77 percent as much sunlight as Earth. They also modeled a super-Earth planet 50 percent wider than Earth with 38 percent stronger gravity, because astronomers have discovered super-Earth worlds around red dwarfs. For instance, Gliese 667Cb, a super-Earth at least 4.5 times the mass of Earth, orbits Gliese 667C, a red dwarf about 22 light years from Earth. They set this super-Earth on an orbit where it received about two-thirds as much as sunlight as Earth.
The researchers modeled three different arrangements of continents for all these planets. One was a water world with no continents and global oceans of varying depths. Another involved a supercontinent covering the night side and an ocean covering the day side. The last mimicked Earth’s configuration of continents. The planets also had atmospheres similar to Earth’s, but the researchers also tested lower levels of the greenhouse gas, carbon dioxide, which traps heat and helps keep planets warm.
When it came to super-Earths covered entirely in water, and super-Earths with continental arrangements like Earth’s, the researchers found it was unlikely that all their water would get trapped on their night sides.
“This is because surface winds transport sea ice to the day side where it is melted easily,” said lead study author Jun Yang at the University of Chicago.
Moreover, ocean currents transport heat from the day side to the night side on these planets.
“Ocean heat transport strongly influences the climate and sea ice thickness on our Earth,” Yang said. “We found this may also work on exoplanets.”
If a super-Earth has very large continents covering most of its night side, the scientists discovered ice sheets of at least 3,300 feet (1,000 meters) thick could grow on its night side. However, the day sides of these super-Earths would dry out completely only if they received less geothermal heat from volcanic activity than Earth, and had 10 percent of the amount of water on Earth’s surface or less. Similar results were seen with Earth-sized planets.
“The important implication is that it may be easier than previously thought to keep liquid water on the dayside of a tidally locked planet, where photosynthesis is possible,” Abbot said. “There are many issues that will affect the habitability of M-star planets, but our results suggest at least that water-trapping on the night side will only be a problem for relatively dry planets with large continents on their nightside and relatively low geothermal heat flux.”
Based on present and near-future technology, Yang said it would be very difficult for astronomers to gauge how thick the sea ice or the ice sheets are on the night sides of red dwarf planets and test whether their models are correct. Still, using current and upcoming technology “it may be possible to know whether the day sides are dry or not,” Yang said.
The new Milky Way galaxy maps are based on observations by the European Space Agency’s prolific Planck space observatory. They show the Milky Way in four distinct color signals that, when combined into a single mosaic, create a hypnotic view of our home galaxy.The Planck satellite observed the oldest light in the universe during its mission. In the new Milky Way maps, red colors indicate dust, yellow is gas, green is high energy particles, and blue is the magnetic field.
“Planck can see the old light from our universe’s birth, gas and dust in our own galaxy, and pretty much everything in between, either directly or by its effect on the old light,” Charles Lawrence, the U.S. project scientist for the mission at NASA’s Jet Propulsion Laboratory in Pasadena, California, said in a statement.
The Planck satellite was built to detect microwave light, which made it sensitive to something called the cosmic microwave background, or light left over from the big bang. Planck’s study of the cosmic microwave background is helping scientists answer questions about the very early days of the universe, such as when the first stars were born.
With its microwave vision, Planck can detect more than just the cosmic microwave background.
One of the new Milky Way images released by the Planck collaboration is an overview that shows four separate galaxy views, as well as the final view of them combined. The red version (upper left) show the heat coming from dust throughout the Milky Way galaxy. Planck can capture this thermal light even though the dust is extremely cold — about minus 420 Fahrenheit (minus 251 Celsius).
The yellow version (upper right) shows carbon monoxide gas, which is concentrated in areas where new stars are being born. Meanwhile, the blue image (lower right) shows light created when charged particles get caught up in the Milky Way’s magnetic field, and are pulled along like a swimmer in a current. The particles accelerate to nearly the speed of light and begin to radiate. The green image (lower left) shows light that is created by free particles that zip past one another without quite colliding. This kind of light is often associated with hot, ionized gas near massive stars.
The $795 million Planck satellite launched in 2009 and collected data for just over four years before being decommissioned in 2013. Last week, the collaboration released the results of a much-anticipated joint study with the BICEP2 collaboration. In March 2014, BICEP2 announced what some scientists took as evidence of inflation in the early universe and evidence of gravitational waves. But the results of the join analysis showed that BICEP2′s measurements were contaminated by space dust.
The white spot on Ceres in a series of new photos taken on Jan. 13 by NASA’s Dawn spacecraft, which is rapidly approaching the round dwarf planet in the asteroid belt between the orbits of Mars and Jupiter. But when the initial photo release on Monday (Jan. 19), the Dawn scientists gave no indication of what the white dot might be.
“Yes, we can confirm that it is something on Ceres that reflects more sunlight, but what that is remains a mystery,” Marc Rayman, mission director and chief engineer for the Dawn mission, told Space.com in an email.
The new images show areas of light and dark on the face of Ceres, which indicate surface features like craters. But at the moment, none of the specific features can be resolved, including the white spot.
“We do not know what the white spot is, but it’s certainly intriguing,” Rayman said. “In fact, it makes you want to send a spacecraft there to find out, and of course that is exactly what we are doing! So as Dawn brings Ceres into sharper focus, we will be able to see with exquisite detail what [the white spot] is.”
Ceres is a unique object in our solar system. It is the largest object in the asteroid belt and is classified as an asteroid. It is simultaneously classified as a dwarf planet, and at 590 miles across (950 kilometers, or about the size of Texas), Ceres is the smallest known dwarf planet in the solar system.
The $466 million Dawn spacecraft is set to enter into orbit around Ceres on March 6. Dawn left Earth in 2007 and in the summer of 2011, it made a year-long pit stop at the asteroid Vesta, the second largest object in the asteroid belt.
While Vesta shared many properties with our solar system’s inner planets, scientists with the Dawn mission suspect that Ceres has more in common with the outer most planets. 25 percent of Ceres’ mass is thought to be composed of water, which would mean the space rock contains even more fresh water than Earth. Scientists have observed water vapor plumes erupting off the surface of Ceres, which may erupt from volcano-like ice geysers.
The mysterious white spot captured by the Dawn probe is one more curious feature of this already intriguing object.
Scientists are finding more evidence of a galactic “skeleton” lurking inside the appendages of the Milky Way, and studying these massive “bones” could help researchers get a better idea of what our galaxy looks like from the outside.
In 2013, researchers first suggested that long, thin, dense clouds of gas may form inside the spiral arms of the Milky Way, creating a sort of galactic skeleton that traces the shape of these massive structures. At the time, only one such “bone” — known as Nessie — had been identified.
Now, new research presented at the 225th meeting of the American Astronomical Society shows that Nessie is not alone. Catherine Zucker, an undergraduate physics student at the University of Virginia, has dug up six strong candidates for additional galactic bones.
Living inside the Milky Way comes with a disadvantage: Astronomers cannot see what this galactic house looks like from the outside. The Milky Way is a spiral galaxy, meaning multiple “arms” sprout from a central region and then swirl around it, like streams of water spiraling down a drain. These arms coil around each other in a flat plane, so the galaxy is like a pancake: When it’s viewed face-on, it is circular, but when it’s viewed edge-on, it’s a straight line. The Earth is nestled inside this pancake, toward the outside of the disc. As a result, the Milky Way appears as a ribbon running down the middle of the night sky.
The sun and the Earth are elevated just slightly above the galactic plane, giving scientists a small boost when they’re trying to look at the larger galactic structure (like a kid on an adult’s shoulders, trying to see over a crowd). Scientists have identified the large spiral arms that make up the galaxy, but there is still debate about the exact location of those arms, as well as the location of smaller spirals that branch off of the larger ones.
But the “bones” that scientists have now identified — long, thin, highly dense clouds of gas that can also be identified by the light they absorb — would be significantly easier to spot, and could help scientists create a more precise sketch of what the Milky Way looks like from the outside.
“It’s a really new field of study,” Zucker told Space.com at the AAS meeting in Seattle, where she presented a poster featuring her work on the galactic skeleton. When Zucker started her work, the gas cloud known as “Nessie” was the only object of its kind that had been identified, and the only candidate for a bone. “What I was trying to do was basically prove that the Nessie filament wasn’t some curiosity, wasn’t a fluke — that there are other filaments out there similar to Nessie that can trace galactic structure.”
Zucker started looking through images of the galaxy taken by various telescopes, including the Spitzer Space Telescope. She found 15 long, thin gas clouds that looked like they could be galactic bones.
There were six initial criteria for a galactic bone. For example, it must lie mostly parallel to the plane of the galaxy and be associated with a known spiral arm — Nessie appears to trace the spine of the Scutum-Centaurus Arm, one of the largest arms in the Milky Way. A bone must also be more than 50 times longer than it is wide — Nessie is more than 300 times longer. Zucker also had to make sure she was seeing a single cloud and not multiple clouds in the same line of sight.
With her list of criteria, Zucker identified 10 candidate bones, six of which met the entire list of requirements. She spelled out her conclusion on her poster: “Nessie is not a ‘curiosity’ – other bones exist.”
Zucker is focusing on something called “Filament 5,” which could be a bone that lies in the Scutum-Centaurus Arm, just like Nessie, but on the opposite side of the galaxy. There is still some debate about the exact location of the Scutum-Centaurus arm. Different measurements put it within a few degrees of the center of the galactic plane. Zucker said bones like Nessie could “potentially resolve a lot of those issues.”
Ultimately, these bones could serve as a guide for creating a sketch of the Milky Way’ major structural elements, and give scientists an outside view of our galaxy, without requiring them to leave home.
The giant black hole at the center of the Milky Way galaxy recently spit out the largest X-ray flare ever seen in that region, astronomers say.
The enormous eruption from the Milky Way’s core was detected on Sept. 14, 2013, very close to the supermassive black hole known as Sagittarius A*. Pronounced “Sagittarius A star” and abbreviated as Sgr A*, the Milky Way’s monster black hole has a mass that is about 4.5 million times that of the sun. Scientists unveiled the discovery of the record-breaking flare this month at the 225th meeting of the American Astronomical Society.
The so-called “megaflare” flare was spotted by NASA’s Chandra X-ray Observatory, which can peer through dust and starlight to the center of the Milky Way. The event was 400 times brighter than the normal level of radiation from this region and nearly three times brighter than the previous record-holding flare, recorded in 2012. A second X-ray flare, with a flash 200 times brighter than normal levels, was then seen on Oct. 22, 2014.
Daryl Haggard, of Amherst College in Massachusetts, presented the findings at a news conference here at the AAS meeting on Jan. 5. Haggard and her colleagues have two possible explanations for what might have caused the flare. First, the black hole may be behaving like our own sun, which also emits bright X-ray flares. In the sun, these flares occur when magnetic-field lines become very tightly packed together or twisted, and the researchers said it’s possible something similar took place near the black hole.
It’s also plausible that the flare was the product of Sgr A* having a snack. An asteroid or other object may have come too close to the black hole, ripping it apart. The debris would have accelerated rapidly and potentially radiated a bright burst of X-rays.
“If an asteroid was torn apart, it would go around the black hole for a couple of hours — like water circling an open drain — before falling in,” Fred Baganoff, of the Massachusetts Institute of Technology and a member of the research team, said in a statement. “That’s just how long we saw the brightest X-ray flare last, so that is an intriguing clue for us to consider.”
Researchers saw the flare by chance while watching Sgr A* in anticipation of a different event: A gas cloud called G2 was set to make a close pass by Sgr A*, and some scientists hypothesized that material from G2 would fall into the black hole, generating a bright display of X-rays, NASA officials said in a statement. But no X-ray signal was detected as G2 made its closest approach to Sgr A*. The new flares do not appear to be part of the missing light show, according to Haggard.
We do not think flares are connected to the G2 object,” Haggard said. “And the reason for that is that the time scales don’t quite match. The time scale for these flares is fairly rapid — thousands of seconds,” or an hour or two, she said.
This time scale is characteristic of an object roughly one astronomical unit (the distance from the Earth to the sun) from Sgr A*, Haggard added. G2′s closest approach to Sgr A* was 150 astronomical units, “so the time scale doesn’t quite match up,” she added.
Haggard and her colleagues are hoping for flares from Sgr A*. With more detailed observations, she said, it might be possible to discern whether Sgr A* is rotating or stationary — a feature that can change aspects of a black hole’s physiology.