Scientists saw repeating pulses from a quasar — a bright galactic core powered by at least one huge black hole — and say the light is likely being generated during the latter stages of a monster black hole collision.
If this interpretation is correct, researchers could learn a great deal more about the final phases of such mergers, where simulations tend to break down — a situation dubbed “the final parsec problem.”
The light signal from 3.5 billion light-years away was spotted by the Catalina Real-Time Transient Survey (CRTS), a set of three telescopes in Australia and the United States that look at 500 million light sources across 80 percent of the sky observable from Earth.
“There has never been a data set on quasar variability that approaches this scope before,” lead study author George Djorgovski, director of the Center for Data-Driven Discovery at the California Institute of Technology, said in a statement.
“In the past, scientists who study the variability of quasars might only be able to follow some tens — or, at most, hundreds — of objects with a limited number of measurements,” Djorgovski said in the statement. “In this case, we looked at a quarter-million quasars, and were able to gather a few hundred data points for each one.”
The discovery came as a surprise, as the researchers were originally trying to learn more about how quasar brightness varies. While scrutinizing the data, however, they found 20 quasars that varied predictably — unlike the chaotic signals that researchers are used to.
Further analysis showed that one quasar, called PG 1302-102, likely has two black holes separated by just a few hundredths of a light-year. Other mergers observed previously placed such colliding black holes much further apart — anywhere between tens and thousands of light-years.
To verify the signal, which appears to repeat every five years, researchers brought in historical information covering most of the last two decades. Also, the light spectrum revealed something interesting happening in the gases surrounding the disc, which are spinning so quickly that they get superheated.
“When you look at the emission lines in a spectrum from an object, what you’re really seeing is information about speed — whether something is moving toward you or away from you and how fast. It’s the Doppler effect,” said co-author Eilat Glikman, an assistant professor of physics at Middlebury College in Vermont.
With quasars, you typically have one emission line, and that line is a symmetric curve,” Glikman added. “But with this quasar, it was necessary to add a second emission line with a slightly different speed than the first one in order to fit the data. That suggests something else, such as a second black hole, is perturbing this system.”
Researchers aren’t sure what is causing the repeating light signal, but possibilities could include jets of material rotating around the center, similar to a lighthouse, or a distorted disc of material around the black holes that is either throwing material on the black holes or “blocking light from the quasar at regular intervals,” Glikman said.
Asteroids have long been regarded as planetary building blocks. But they may actually be byproducts of planet formation, born when violent collisions smashed an earlier generation of objects apart, a new study suggests.
Asteroid fragments that fall to Earth as meteorites often contain tiny, round pellets called chondrules that formed when molten droplets quickly cooled in space in the solar system’s early years. Chondrules are found in 92 percent of all meteorites, and are often thought to be the building blocks of planets.
Chondrules were part of the protoplanetary disc of gas and dust surrounding the newborn sun that gave birth to Earth and the other planets. A recent study found that chondrules formed about 1 million years after planetesimals — the building blocks of protoplanets — came together.
Prior research had suggested that chondrules in some meteorites were probably born when rocks in space collided at speeds of more than 22,370 mph (36,000 km/h). However, it was uncertain how the majority of chondrules formed.
Now, scientists have found that cosmic impacts could have generated enough chondrules during the first 5 million years or so of planet formation to explain the large quantity of these pellets.
“The most surprising implication of our work is that the meteorites we find on Earth are not actually the building blocks of planets, as has been thought for a long time,” lead study author Brandon Johnson, a planetary scientist at MIT, told Space.com. “Instead, they may be a byproduct of planetary formation.”
Chondrule-bearing meteorites — known as chondrites — may thus not be representative of the objects that built the solar system’s planets, study team members said.
The researchers simulated impacts of varying speeds between protoplanetary objects about 60 to 650 miles (100 to 1,000 kilometers) wide. They found that when collision speeds exceeded 5,590 mph (9,000 km/h), plumes of molten rock that blasted out from these impacts could form millimeter-size droplets that could have cooled into chondrules.
The scientists calculated that cosmic impacts within a typical protoplanetary disc could have generated more than 44 billion trillion lbs. (20 billion trillion kilograms) of chondrules. For comparison, the present asteroid belt currently has a mass of about 6.6 billion trillion lbs. (3 billion trillion kg).
This finding suggests that cosmic impacts could have generated many of the chondrules in the asteroid belt from which nearly all meteorites originate.
“We’ve put together a coherent model for chondrule formation,” Johnson said. “Once we have a proper context for how chondrules formed, we can really understand what was happening in the nascent solar system.”
Johnson noted that the team’s work only investigated vertical impacts. “More realistic impacts may be at an angle,” Johnson said. Still, such oblique impacts “produce more jetted materials, more chondrules,” he added.
A NASA space telescope has spotted a colossal black hole chowing down on gas from a distant collision between two doomed galaxies. Views of the cosmic smashup, which the swirl of gas and dust previously hid, will likely shed light on the evolution of galaxies, scientists say.
The new view of the colliding galaxies — known collectively as Arp 299 — was captured by NASA’s Nuclear Spectroscopic Telescope Array (NuSTAR), an X-ray space telescope built to hunt black holes. The galaxies in Arp 299 are about 130 million light-years from Earth and made a close pass by each other about 700 million years ago, sparking a fierce burst of star formation. Now, some stars from the galaxies are turning to dust via huge supernova explosions.
But star formation isn’t the only result of such supermassive collisions. As two galaxies merge, the chaos should send gas flowing to the central black holes. This collision-induced feeding frenzy by black holes helps explain how the objects grow to be millions to billions of times the mass of the sun.
“We want to understand the mechanisms that trigger the black holes to turn on and start consuming the gas,” the study’s lead researcher, Andrew Ptak, of NASA’s Goddard Space Flight Center in Greenbelt, Maryland, said in a statement.
Although previous space telescopes, including NASA’s Chandra X-ray Observatory and the European Space Agency’s XMM-Newton, have observed Arp 299, they were only able to probe the low-energy X-rays emitted by the collision and unable to see if one or both of the black holes were actively chomping down gas.
“Odds are low that both black holes are on at the same time in a merging pair of galaxies,” said co-author Ann Hornschemeier, also of NASA’s Goddard Space Flight Center, referring to the black holes’ ability to munch down gas and shine brightly. “When the cores of the galaxies get closer, however, tidal forces slosh the gas and stars around vigorously, and, at that point, both black holes may turn on.”
NASA’s NuSTAR space telescope, launched in 2012, is the first observatory capable of spotting high-energy X-rays and therefore making sense of the tangled galaxies in Arp 299. The new image shows that the black hole in the galaxy on the right is indeed the hungry one. Meanwhile, the black hole on the left is likely dormant or hidden by thicker layers of gas and dust.
“Before now, we couldn’t pinpoint the real monster in the merger,” said Ptak.
As it approaches the supermassive black hole, the gas grows increasingly hot — so hot that electrons get stripped off of atoms — and a plasma is created. This plasma then boosts the visible light up to high-energy X-rays, detectable by NuSTAR.
As an added bonus, the galaxies’ two black holes themselves will eventually merge, shaking the fabric of space-time and producing gravitational waves that propagate outward like ripples on a pond.
The study, which has been accepted for publication in the Astrophysical Journal, was presented Thursday (Jan. in Seattle at the 225th American Astronomical Society meeting.
Astronomers have spotted a new object emerging from the ashes of a recently deceased star. The stellar post-mortem, which is recounted in two new videos, may also solve a mystery surrounding the unexpected shape of the star’s explosive remains, scientists say.
In February 1987, astronomers saw a new point of light appear in the sky: a supernova explosion, roughly 150,000 light-years from Earth. A massive star had reached the end of its fuel supply and gone down in a blaze of glory. Since then, scientists have studied the corpse of Supernova 1987A extensively, including visualizing the supernova’s dissection in a new video.
“It’s like doing a forensic investigation into the death of a star,” said Giovanna Zanardo, a Ph.D. candidate at the University of Western Australia, in a statement.
Zanardo and a group of collaborators from the International Centre for Radio Astronomy Research (ICRAR) in Perth, Western Australia, have highlighted some of their most recent findings about 1987A in two videos. In them, the researchers “dissect” the supernova remains with observations, and attempt to recreate the event using computer models.
The ICRAR scientists believe they have identified a pulsar or neutron star in the supernova debris. When massive stars die, the leftover material may collapse down into an incredibly dense object called a neutron star. Pulsars are rapidly spinning neutron stars that radiate bright beams of light that appear to pulse on and off, like a lighthouse.
Images featured in one supernova video show what the ICRAR scientists say is light from the new object.
The challenge in identifying this object, said the researchers, is detecting its faint light in the bright chaos of the debris field. In order to disentangle the different light sources, the researchers combined observations from two telescopes: the Atacama Large Millimetre/submillimeter Array (ALMA) in Chile’s Atacama Desert and the Australia Telescope Compact Array (ATCA) in New South Wales.
The combined observations allowed the ICRAR researchers to see different wavelengths of light emitted by the stellar remains: waves, microwaves and infrared light. Analyzing each of these wavelengths alone enabled the researchers to look for different objects that radiate different kinds of light.
In the second supernova video, the ICRAR scientists show how they may have also solved a long-standing mystery about the shock wave that is still expanding away from the supernova remnant.
Scientists have observed that one side of the supernova explosion appears brighter than the other. To figure out why, researchers at ICRAR developed a 3D simulation of the stellar death. They found that tweaking things in the simulation, like the asymmetry of the explosion and the composition of the gas surrounding the supernova, changed the outcome and eventually created models that agree with the new observations.
“The fact that the model matches the observations so well means that we now have a good handle on the physics of the expanding remnant, and are beginning to understand the composition of the environment surrounding the supernova,” said Toby Potter, a UWA researcher at ICRAR, said in the statement. This understanding, he said, “is a big piece of the puzzle solved in terms of how the remnant of SN1987A formed.”
Stanford university is inviting artificial intelligence researchers, roboticists and other scientists to participate in what it is calling the One Hundred Year Study on Artificial Intelligence (AI100). Scientists will consider how machines that perceive, learn and reason will affect the way people live, work and communicate.
“If your goal is to create a process that looks ahead 30 to 50 to 70 years, it’s not altogether clear what artificial intelligence will mean, or how you would study it,” said Russ Altman, a professor of bioengineering and computer science at Stanford. “But it’s a pretty good bet that Stanford will be around, and that whatever is important at the time, the university will be involved in it.”
The future, and potential, of artificial intelligence has come under fire and increasing scrutiny in the past several months after both renowned physicist, cosmologist and author Stephen Hawking and high-tech entrepreneur Elon Musk warned of what they perceive as a mounting danger from developing AI technology.
Musk, speaking at an MIT symposium in October, said scientists should be careful about developing AI technology. “If I were to guess at what our biggest existential threat is, it’s probably that,” said Musk, CEO of electric car maker Tesla Motors, and CEO and co-founder of the commercial space flight company SpaceX. “With artificial intelligence, we are summoning the demon. In all those stories with the guy with the pentagram and the holy water, and he’s sure he can control the demon. It doesn’t work out.”
Hawking added to the conversation in an interview with the BBC,, saying scientists should be cautious about creating machines that could one day be smarter and stronger than humans.
“It would take off on its own and re-design itself at an ever-increasing rate,” Hawking said in the interview. “Humans, who are limited by slow biological evolution, couldn’t compete, and would be superseded.”
Stanford’s AI project appears to be more focused on what AI can add to society, though the project is looking to keep an eye on development and any direction that might take.
A NASA probe is about to get the first up-close look at a potentially habitable alien world.
In March 2015, NASA’s Dawn spacecraft will arrive in orbit around the dwarf planet Ceres, the largest object in the main asteroid belt between Mars and Jupiter. Ceres is a relatively warm and wet body that deserves to be mentioned in the same breath as the Jovian moon Europa and the Saturn satellite Enceladus, both of which may be capable of supporting life as we know it, some researchers say.
“I don’t think Ceres is less interesting in terms of astrobiology than other potentially habitable worlds,” Jian-Yang Li, of the Planetary Science Institute in Tucson, Arizona, said Thursday (Dec. 18) during a talk here at the annual fall meeting of the American Geophysical Union.
Life as we know it requires three main ingredients, Li said: liquid water, an energy source and certain chemical building blocks (namely, carbon, hydrogen, nitrogen, oxygen, phosphorus and sulfur).
The dwarf planet Ceres — which is about 590 miles (950 kilometers) wide — is thought to have a lot of water, based on its low overall density (2.09 grams per cubic centimeter; compared to 5.5 g/cubic cm for Earth). Ceres is likely a differentiated body with a rocky core and a mantle comprised of water ice, researchers say, and water-bearing minerals have been detected on its surface.
Indeed, water appears to make up about 40 percent of Ceres’ volume, Li said.
“Ceres is actually the largest water reservoir in the inner solar system other than the Earth,” he said. However, it’s unclear at the moment how much, if any, of this water is liquid, he added.
As far as energy goes, Ceres has access to a decent amount via solar heating, since the dwarf planet lies just 2.8 astronomical units (AU) from the sun, Li said. (One AU is the distance between Earth and the sun — about 93 million miles, or 150 million km). Europa and Enceladus are much farther away from our star — 5.2 and 9 AU, respectively.
Both Europa and Enceladus possess stores of internal heat, which is generated by tidal forces. This heat keeps the ice-covered moons’ subsurface oceans of liquid water from freezing up, and also drives the eruption of water-vapor plumes on Enceladus (and probably Europa as well; researchers announced last year that NASA’s Hubble Space Telescope spotted water vapor erupting from the Jupiter moon in December 2012).
Intriguingly, scientists announced the discovery of water-vapor emission from Ceres — which may also possess a subsurface ocean — earlier this year.
Ceres’ plumes may or may not be evidence of internal heat, Li said. For example, they may result when water ice near Ceres’ surface is heated by sunlight and warms enough to sublimate into space.
“Right now, we just don’t know much about the outgassing on Ceres,” Li said.
Dawn should help bring Ceres into much clearer focus when it reaches the dwarf planet this spring. The spacecraft, which orbited the huge asteroid Vesta from July 2011 through September 2012, will map Ceres’ surface in detail and beam home a great deal of information about the body’s geology and thermal conditions before the scheduled end of its prime mission in July 2015.
Ground-based instruments should also play a role in unveiling Ceres. For example, the Atacama Large Millimeter/submillimeter Array, or ALMA — a huge system of radio dishes in Chile — has the ability to probe deeper than Dawn, going into Ceres’ subsurface and shedding more light on the dwarf planet’s composition and thermal properties, Li said.
“This is highly complementary to the Dawn mission,” he said.
Ceres’ relative proximity to Earth also makes it an attractive target for future space missions, Li added.
These deadly outbursts could help explain the so-called Fermi paradox, the seeming contradiction between the high chance of alien life and the lack of evidence for it, scientists added.
Gamma-ray bursts are brief, intense explosions of high-frequency electromagnetic radiation. These outbursts give off as much energy as the sun during its entire 10-billion-year lifetime in anywhere from milliseconds to minutes. Scientists think gamma-ray bursts may be caused by giant exploding stars known as hypernovas, or by collisions between pairs of dead stars known as neutron stars.
If a gamma-ray burst exploded within the Milky Way, it could wreak extraordinary havoc if it were pointed directly at Earth, even from thousands of light-years away. Although gamma rays would not penetrate Earth’s atmosphere well enough to burn the ground, they would chemically damage the atmosphere, depleting the ozone layer that protects the planet from damaging ultraviolet rays that could trigger mass extinctions. It’s also possible that gamma-ray bursts may spew out cosmic rays, which are high-energy particles that may create an experience similar to a nuclear explosion for those on the side of the Earth facing the explosion, causing radiation sickness.
To see how great a threat gamma-ray bursts might pose to Earth, researchers investigated how likely it was that such an explosion could have inflicted damage on the planet in the past.
Gamma-ray bursts are traditionally divided into two groups — long and short — depending on whether they last more or less than 2 seconds. Long gamma-ray bursts are associated with the deaths of massive stars, while short gamma-ray bursts are most likely caused by the mergers of neutron stars.
For the most part, long gamma-ray bursts happen in galaxies very different from the Milky Way — dwarf galaxies low in any element heavier than hydrogen and helium. Any long gamma-ray bursts in the Milky Way will likely be confined in regions of the galaxy that are similarly low in any element heavier than hydrogen and helium, the researchers said.
The scientists discovered the chance that a long gamma-ray burst could trigger mass extinctions on Earth was 50 percent in the past 500 million years, 60 percent in the past 1 billion years, and more than 90 percent in the past 5 billion years. For comparison, the solar system is about 4.6 billion years old.
Short gamma-ray bursts happen about five times more often than long ones. However, since these shorter bursts are weaker, the researchers found they had negligible life-threatening effects on Earth. They also calculated that gamma-ray bursts from galaxies outside the Milky Way probably pose no threat to Earth.
These findings suggest that a nearby gamma-ray burst may have caused one of the five greatest mass extinctions on Earth, such as the Ordovician extinction that occurred 440 million years ago. The Ordovician extinction was the earliest of the so-called Big Five extinction events, and is thought by many to be the second largest. [Wipe Out: History's Most Mysterious Extinctions]
The scientists also investigated the danger that gamma-ray bursts may pose for life elsewhere in the Milky Way. Stars are packed more densely together toward the center of the galaxy, meaning worlds there face a greater danger of gamma-ray bursts. Worlds in the region about 6,500 light-years around the Milky Way’s core, where 25 percent of the galaxy’s stars reside, faced more than a 95 percent chance of a lethal gamma-ray burst within the past billion years. The researchers suggest that life as it is known on Earth could survive with certainty only in the outskirts of the Milky Way, more than 32,600 light-years from the galactic core.
The researchers also explored the danger gamma-ray bursts could pose for the universe as a whole. They suggest that because of gamma-ray bursts, life as it is known on Earth might safely develop in only 10 percent of galaxies. They also suggest that such life could only have developed in the past 5 billion years. Before then, galaxies were smaller in size, and gamma-ray bursts were therefore always close enough to cause mass extinctions to any potentially life-harboring planets.
“This may be an explanation, or at least a partial one, to what is called the Fermi paradox or the ‘Big Silence,’” said lead study author Tsvi Piran, a physicist at the Hebrew University in Jerusalem. “Why we haven’t encountered advanced civilizations so far? The Milky Way galaxy is much older than the solar system and there was ample time and ample space — the number of planetary systems with conditions similar to Earth is huge — for life to develop elsewhere in the galaxy. So why we haven’t encountered advanced civilizations so far?”
The answer to Fermi’s paradox may be that gamma-ray bursts have struck many life-harboring planets. The most severe criticism of these estimates “is that we address life as we know it on Earth,” Piran told Live Science. “One can imagine very different forms of life that are resilient to the relevant radiation.”
The enormous black holes that lurk at the hearts of all galaxies are significantly bigger than astronomers had imagined, a new study suggests.
Researchers have used a new method to measure the distance to the active spiral galaxy NGC 4151 — whose core is dubbed the “Eye of Sauron” because of its resemblance to the structure in the “Lord of the Rings” films — with unprecedented precision. This calculation enabled them to determine the mass of NGC 4151′s central black hole more accurately — and the results were surprising.
”Our calculations show that the supermassive black holes are 40 percent heavier than previously thought,” study co-author Darach Watson, of the University of Copenhagen’s Niels Bohr Institute (NBI), said in a statement. “This fundamentally changes determinations of the masses of black holes.”
Supermassive black holes can contain as much mass as hundreds of millions, or even several billion, suns.
Previous estimates of the distance to NGC 4151′s central black hole relied on measurements of redshift — how wavelengths of light are lengthened by an object’s motion away from Earth-based observers. This technique yielded imprecise results, with estimates ranging from 13 million to 95 million light-years, Watson said.
So the study team, led by Sebastian Hönig of the University of Southampton in England (who was working at NBI while performing the research), tried out a different method: geometry.
As NGC 4151′s black hole draws in nearby gas, the material gets heated up and releases ultraviolet (UV) radiation. This radiation, in turn, heats up a ring of dust that orbits the black hole, causing the dust to give off infrared radiation.
Observations by Earth-based telescopes have revealed that the time delay between the UV and infrared emission is 30 days. Because the speed of light is known, calculating the distance between the black hole and the dust ring is a relatively straightforward matter.
The researchers used the twin Keck telescopes in Hawaii to measure the angle the dust ring makes in the sky — just 12 millionths of a degree. They combined the light collected by both telescopes, using a technique called interferometry. The method resulted in a resolution about 100 times greater than that achieved by NASA’s Hubble Space Telescope, researchers said.
The team could then calculate the distance to the Eye of Sauron using geometry. The distance from the black hole to the dust ring forms the base of an isosceles triangle, whose twin long legs are the distance from Earth to either side of the ring; with the angle of the sharp point of the triangle known, the legs’ distance can be computed.
The team calculated the distance to NGC 4151 to be 62 million light-years, with an uncertainty of just 13.5 percent or so. This improved precision will help researchers estimate the true heft of supermassive black holes, Watson said.
”The calculations of the mass (weight) of the supermassive black holes at the heart of galaxies depends on two main factors: the rotational speed of the stars in the galaxy and how far it is from the black hole to the stars,” he said. “The rotational speed can be observed, and the distance from the black hole out to the rotating disc of stars can now be calculated precisely using the new method.”
Initial indications suggest that supermassive black hole masses have been underestimated by perhaps 40 percent. Researchers hope to extend their measurements to other active galaxies; the technique could eventually help astronomers better understand the rate at which the universe is expanding, study team members said.
The new study was published online today (Nov. 26) in the journal Nature.
The low birth rate for stars in distant galaxy clusters is one of astronomy’s long-standing mysteries. But scientists now have a new culprit in the case: cosmic turbulence from black holes.
The discovery, made by astronomers using NASA’s Chandra X-Ray Observatory, suggests that black holes make it hard for new stars to form in gas-rich galaxy clusters. It may also explain why more infant stars aren’t present in these otherwise fertile areas, researchers said.
“We knew that somehow the gas in clusters is being heated to prevent it cooling and forming stars. The question was exactly how,” said the study’s lead author Irina Zhuravleva, of Stanford University in Palo Alto, California, in a NASA statement. Zhuravleva and her colleagues suspect they “may have found evidence that the heat is channeled from turbulent motions.”
Zhuravleva’s team used the Chandra X-ray Observatory to study the Virgo and Perseus galaxy clusters, which are brimming with thousands of galaxies and even more stars. The Virgo galaxy cluster alone contains about 2,000 galaxies — the largest of which contain roughly 1 trillion stars.
But despite their sheer size, the most massive element of the galactic clusters are the gas that lives in the spaces between galaxies. Over time, these gas clouds should naturally cool down and become prime areas of star formation. But in most galaxies, the gas is hotter than predicted. Since this hot gas can’t coalesce into stars, star births remain low, researchers said.
Turbulence usually refers to chaotic changes in the pressure and speed of a material. A fast moving ship, for example, can create turbulence on an otherwise calm body of water. In the interstellar gas clouds, the turbulence is believed to originate with supermassive black holes, which spit out violent jets of matter. The jets carve out deep cavities in the gas and generate strong turbulence, which gets passed into the gas cloud surrounding the cavity.
For the new study, which is detailed in the journal Nature, the researchers used the Chandra X-ray Observatory to study gas clouds in the Virgo and Perseus galaxy clusters. The X-ray images showed changes in the density of gas in those clusters, or areas where the gas was either bunched up or spread out. The researchers say these changes indicate the amount of turbulence in that area, from which they can estimate how much heat will be distributed to the gas.
“Our work gives us an estimate of how much turbulence is generated in these clusters,” said one of the study’s authors, Alexander Schekochihin of the University of Oxford in the United Kingdom, in the press release. “From what we’ve determined so far, there’s enough turbulence to balance the cooling of the gas.”
Turbulence in galaxy cluster gas clouds could come from other major events, like two galaxies merging together. But the researchers believe black hole ejections are the most common source of the turbulence that ultimately hinders star birth.
That’s apparently what happens when a dying star swallows a smaller, dead star. And for decades, this exotic cosmic rarity was only theory, a wild idea hatched by an astronomer and a now-famous physicist and an astronomer.
It’s called a Thorne-Zytkow object (TZO), and its existence was first proposed in 1975 by physicist Kip Thorne and astronomer Anna Zytkow. TZOs The strange hybrid stars are theorized to form from binary systems containing two massive stars — a neutron star and a red supergiant star.
Neutron stars are extraordinarily dense corpses of normal stars. Red supergiants are dying stars with the greatest diameters of any star in the universe, ranging from 200 to 2,000 times wider than the sun — “so big that if you placed them where our sun is, they would extend out to, or even beyond, the orbit of Saturn,” said study lead author Emily Levesque, an astrophysicist at the University of Colorado at Boulder.
The news study, which details the likely discovery of the Thorne-Zytkow object, was published in the Sept. 1 issue of the journal MNRAS Letters. News of the find first came out, and was previewed in June, shortly after the study was submitted to the online preprint site arxiv.org.
The hunt for a hybrid star
A TZO is typically thought to form when a red supergiant engulfs an orbiting neutron star. The merger would result in “a shell of burning material around the neutron core — a shell that would generate new elements as it burned,” Thorne said in a statement. “Convection, the circulation of hot gas inside the star, would reach right into the burning shell and carry the products of burning all the way to the surface of the star long before the burning was complete.”
A TZO should appear virtually identical to a very bright red supergiant. However, a TZO’s unique innards should produce unusually large amounts of rubidium, strontium, yttrium, zirconium, molybdenum and lithium, setting it apart from a normal red supergiant.
Now, scientists have detected a red supergiant with the distinct chemical signature of a TZO, suggesting they may have detected these space oddities for the first time.
“I am extremely happy that observational confirmation of our theoretical prediction has started to emerge,” Zytkow said in a June statement.
In a galaxy not so far away
The candidate TZO is named HV 2112. The star is a member of the Small Magellanic Cloud, a dwarf galaxy about 199,000 light-years away that is a close neighbor of the Milky Way and easily visible to the naked eye from the Southern Hemisphere.
The researchers identified HV 2112 after a survey of 62 red supergiants conducted with the 6.5-meter (21.3 feet) Magellan Clay telescope in Chile and the Apache Point Observatory 3.5-meter (11.5 feet) telescope in New Mexico.
“On our first night at the Magellan telescope, we had a fantastic ‘Hmmm, that’s odd’ moment,” Levesque told Space.com. “We were displaying the raw data as we took it, and when one star’s data popped up, we could tell, even in that messy format, that the spectrum was unusual. Our co-author Nidia Morrell [of the Carnegie Observatories in La Serena, Chile] looked at the data for this star and immediately said, ‘I don’t know what it is, but I know that I like it!’”
“It was our first inkling that there was something different about this star,” Levesque said. “And that star turned out to be HV 2112.”
The scientists confirmed excess levels of rubidium, molybdenum and lithium in HV 2112′s gaseous shroud.
“If HV 2112 is found to be a bona fide TZO, this would have huge implications,” Levesque said. “It could offer the first solid evidence for a completely different model of how stars’ interiors can work. Inside these stars, we also have a new way of producing elements, and knowing where the various elements come from is a critical ingredient in trying to understand how the universe works. We hear that everything is made of ‘star stuff’ — inside TZOs, we might have found a totally new way to make some of it.”
Is it really there?
The evidence that HV 2112 is a TZO is strong “but not ironclad,” Thorne said in a statement. “Certainly it’s by far the best candidate for a TZO that anyone has seen, but additional confirmation is needed.”
Although HV 2112 looks exactly how the researchers expected a TZO to look, “some of those expectations are based on models and predictions from a couple of decades ago,” Levesque said. “It’s possible that when modern-day models are run, they will give us new things to look for or new ideas of what a TZO might look like.”
Levesque noted that she had already “gotten dozens of emails from people who are interested in running their own new computer models to test how TZO interiors work, how they might form or evolve, or even whether or not they can stably exist. “A few months ago, TZOs were an interesting but somewhat obscure topic, but our discovery has spurred a renewed interest in these stars,” Levesque said. “Whether people are criticizing our findings or setting out to prove us wrong honestly matters less to me than the fact that new research on TZOs is underway — the more people study them, the more we’ll know!”
Levesque said that after she and her colleagues get more information on what modern-day models predict TZOs should look like, they would like to get more observations of HV 2112 and its surroundings “to see if there are any other strange quirks or tell-tale signs of it being a TZO.”
“Searching for more TZOs would obviously be exciting, too,” Levesque added. “Finding one is interesting, but if we find several, we’ll be able to learn so much more.”
On April 23, NASA’s Swift satellite spotted the enormous star flare coming from DG Canum Venaticorum (DG CVn), a system of two red dwarfs located about 60 light-years from Earth. The eruption put to shame anything ever seen on the sun, whose strong flares are classified into three categories, with C flares being the weakest, M of medium strength and X the most powerful.
“The biggest flare we’ve ever seen from the sun occurred in November 2003 and is rated as X45,” Stephen Drake, an astrophysicist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, said in a statement. “The flare on DG CVn, if viewed from a planet the same distance as Earth is from the sun, would have been roughly 10,000 times greater than this, with a rating of about X100,000.”
For a few minutes, the superflare’s X-ray brightness outshone both stars’ total luminosity in all wavelengths, researchers said. The eruption’s temperature reached 360 million degrees Fahrenheit (200 million degrees Celsius) — about 13 times hotter than the sun’s core.
But DG CVn wasn’t done yet, firing off a number of other flares over the next 11 days, with each one being a bit weaker than the last. X-ray emission from the system finally returned to baseline levels 20 days after the April 23 event.
DG CVn’s sustained activity surprised scientists.
“We used to think major flaring episodes from red dwarfs lasted no more than a day, but Swift detected at least seven powerful eruptions over a period of about two weeks,” said Drake, who gave a presentation about the DG CVn superflare in August at a meeting of the American Astronomical Society’s High Energy Astrophysics Division. “This was a very complex event.”
Both of the stars in the DG CVn system are about one-third as massive as the sun. They orbit about 3 astronomical units from each other — too close for Swift to tell which one of them was responsible for the big flares this year. (One astronomical unit, or AU, is the average distance from Earth to the sun — about 93 million miles, or 150 million kilometers).
The DG CVn stars complete one rotation in less than a day, compared to about 25 days for the sun. The dwarfs’ rotational speed helps explain how they are capable of such powerful flaring, researchers said: Flares erupt when a star’s twisted magnetic fields reconnect, and rapid spin amps these fields up.
The sun may once have blasted out megaflares, too. A star’s rotational speed decreases as it ages, and our sun is middle-aged at about 5 billion years old. The DG CVn stars are just 30 million years old or so, researchers said.
In the past 20 years or so, astronomers have confirmed the existence of nearly 2,000 worlds outside Earth’s solar system. Many of these exoplanets lie in the habitable zones of stars, areas potentially warm enough for the worlds to harbor liquid water on their surfaces. Astrobiologists hope that life may someday be spotted on such alien planets, since there is life pretty much everywhere water exists on Earth.
One strategy to discover signs of such alien life involves looking for ways that organisms might change a world’s appearance. For example, chemicals typically shape what are known as the spectra seen from planets by adding or removing wavelengths of light. Alien-hunting telescopes could look for spectra that reveal chemicals associated with life. In other words, these searches would focus on biosignatures — chemicals or combinations of chemicals that life could produce, but that processes other than life could not or would be unlikely to create.
Astrophysicists Timothy Brandt and David Spiegel at the Institute for Advanced Study in Princeton, New Jersey, sought to see how challenging it might be to conclusively identify signatures of water, oxygen and chlorophyll — the green pigment that plants use to convert sunlight to energy — on a distant twin of Earth using a future off-Earth instrument such as NASA’s proposed Advanced Technology Large-Aperture Space Telescope (ATLAST).
The scientists found that water would be the easiest to detect.
“Water is a very common molecule, and I think a mission to take spectra of exoplanets should certainly look for water,” said Brandt, the lead study author. “Indeed, we have found water in a few gas giants more massive than Jupiter orbiting other stars.”
In comparison, oxygen is more difficult to detect than previously thought, requiring scientific instruments approximately twice as sensitive as those needed to detect water and significantly better at discriminating between similar colors of light.
“Oxygen, however, has only been a large part of Earth’s atmosphere for a few hundred million years,” Brandt said. “If we see it in an exoplanet, it probably points to life, but not finding oxygen certainly does not mean that the planet is sterile.”
Although a well-designed space telescope could detect water and oxygen on a nearby Earth twin, the astrophysicists found the instrument would need to be significantly more sensitive or very lucky, to see chlorophyll. Identifying this chemical typically requires scientific instruments about six times more sensitive than those needed for oxygen. Chlorophyll becomes as detectable as oxygen only when an exoplanet has a lot of vegetation and/or little in the way of cloud cover, researchers said.
Chlorophyll slightly reddens the light from Earth. If extraterrestrial life does convert sunlight to energy as plants do, scientists expect that the alien process might use a different pigment than chlorophyll. But alien photosynthesis could also slightly redden planets, just as chlorophyll does.
“Light comes in packets called photons, and only photons with at least a certain amount of energy are useful for photosynthesis,” Brandt said. Chlorophyll reflects photons that are too red and low in energy to be used for photosynthesis, and it may be reasonable to assume that extraterrestrial pigments would do the same thing, Brandt noted.
The researchers suggest a strategy for discovering Earthlike alien life that first looks for water, then oxygen on the more favorable planets and finally chlorophyll on only the most exceptionally promising worlds.
“The goal of a future space telescope will be primarily to detect water and oxygen on a planet around a nearby star,” Brandt said. “The construction and launch of such a telescope will probably cost at least $10 billion and won’t happen for at least 20 years — a lot of technology development needs to happen first — but it could be the most exciting mission of my lifetime.”
Brandt and Spiegel detailed their findings online Sept. 1 in the journal Proceedings of the National Academy of Sciences.
The molecule in question — iso-propyl cyanide (i-C3H7CN) — was spotted in Sagittarius B2, a huge star-making cloud of gas and dust near the center of the Milky Way, about 27,000 light-years from the sun. The discovery suggests that some of the key ingredients for life on Earth could have originated in interstellar space.
A specific molecule emits light at a particular wavelength and in a telltale pattern, or spectrum, which scientists can detect using radio telescopes. For this study, astronomers used the enormous Atacama Large Millimeter/submillimeter Array (ALMA) telescope in the Chilean desert, which went online last year and combines the power of 66 radio antennas. [5 Bold Claims of Alien Life]
Iso-propyl cyanide joins a long list of molecules detected in interstellar space. But what makes this discovery significant is the structure of iso-propyl cyanide. All other organic molecules that have been detected in space so far (including normal-propyl cyanide, the sister of i-C3H7CN) are made of a straight chain with a carbon backbone. Iso-propyl cyanide, however, has a “branched” structure. This same type of branched structure is a key characteristic of amino acids.
“Amino acids are the building blocks of proteins, which are important ingredients of life on Earth,” the study’s lead author, Arnaud Belloche, of the Max Planck Institute for Radio Astronomy, told Space.com in an email. “We are interested in the origin of amino acids in general and their distribution in our galaxy.”
Scientists have previously found amino acids in meteorites that fell to Earth, and the composition of these chemicals suggested they had an interstellar origin. The researchers in this new study did not find amino acids, but their discovery adds an “additional piece of evidence that the amino acids found in meteorites could have been formed in the interstellar medium,” Belloche wrote.
“The detection of a molecule with a branched carbon backbone in interstellar space, in a region where stars are being formed, is interesting because it shows that interstellar chemistry is indeed capable of producing molecules with such a complex, branched structure,” Belloche added.
It was first suggested in the 1980s that branched molecules could form on the surface of dust grains in interstellar space. But this is the first time such compounds have been detected. What’s more, iso-propyl cyanide seemed to be plentiful — it was almost half as abundant of its more common sister variant in Sagittarius B2, the study found. This means that branched molecules could actually be quite ordinary in interstellar space, the researchers said.
Researchers using data gathered by NASA’s Hubble Space Telescope have determined that the supernova SN 1993J — which was first observed in 1993, as its name suggests — occurred because one star nabbed hydrogen from another.
“This is like a crime scene, and we finally identified the robber,” study co-author Alex Filippenko, a professor of astronomy at the University of California, Berkeley, said in a statement. “The companion star stole a bunch of hydrogen before the primary star exploded.” [Supernova Photos: Great Images of Star Explosions]
One telltale sign that something was unusual came through looking at the composition of SN 1993J, which is a Type IIb supernova — a rare kind of star explosion that has much less hydrogen than typical supernovas do.
Astronomers began searching for the companion star shortly after the discovery of SN 1993J, which is found in the Messier 81 galaxy, about 11 million light-years from Earth. They were unable to find the companion, however, because the supernova zone was so crowded that it was tough to know if they were observing the correct star.
“A binary system is likely required to lose the majority of the primary star’s hydrogen envelope prior to the explosion,” said lead author Ori Fox, also of UC Berkeley. “The problem is that, to date, direct observations of the predicted binary companion star have been difficult to obtain since it is so faint relative to the supernova itself.”
What eventually turned the tide was combining optical images with Hubble ultraviolet (UV) data to find the spectrum of elements expected to emanate from the companion star. The team plans to examine the system further to find more properties of the companion and to better figure out how stars explode, researchers said.
“We were able to get that UV spectrum with Hubble. This conclusively shows that you have an excess of continuum emission in the UV, even after the light from other stars has been subtracted,” said co-author Azalee Bostroem of the Space Telescope Science Institute in Baltimore, Maryland.
While supernovas occur about once every second throughout the cosmos, catching one is a challenge to astronomers. Many of them appear faint because they are far from our planet, or they can be obscured from our view by cosmic dust. This makes predicting star explosions even more of a puzzle for scientists.
A team of researchers has delineated the “Venus Zone,” the range of distances from a host star where planets are likely to resemble Earth’s similarly sized sister world, which has been rendered unlivably hot due to a runaway greenhouse effect.
The new study should help scientists get a better handle on how many of the rocky planets spotted by NASA’s prolific Kepler space telescope are truly Earth-like, team members said.
“The Earth is Dr. Jekyll, and Venus is Mr. Hyde, and you can’t distinguish between the two based only on size,” lead author Stephen Kane, of San Francisco State University, said in a statement. “So the question then is, how do you define those differences, and how many ‘Venuses’ is Kepler actually finding?”
The results could also lead to a better understanding of Earth’s history, Kane added.
“We believe the Earth and Venus had similar starts in terms of their atmospheric evolution,” he said. “Something changed at one point, and the obvious difference between the two is proximity to the sun.”
Kane and his team defined the Venus Zone based on solar flux — the amount of stellar energy that orbiting planets receive. The outer edge of the zone is the point at which a runaway greenhouse effect would take hold, with a planet’s temperature soaring thanks to heat-trapping gases in its atmosphere. The inner boundary, meanwhile, is the distance at which stellar radiation would completely strip away a planet’s air.
The thinking is similar to that behind the “habitable zone” — the just-right range of distances from a star at which liquid water, and perhaps life as we know it, may be able to exist.
The dimensions of these astronomical zones vary from star to star, since some stars are hotter than others. In our own solar system, the Venus Zone’s outer boundary lies just inside the orbit of Earth, researchers said.
Future space-based instruments — such as NASA’s $8.8 billion James Webb Space Telescope, scheduled to launch in 2018 — will be able to analyze some exoplanets’ atmospheres, helping scientists refine the Venus Zone concept, researchers said.
“If we find all of these planets in the Venus Zone have a runaway greenhouse-gas effect, then we know that the distance a planet is from its star is a major determining factor. That’s helpful to understanding the history between Venus and Earth,” Kane said.
“This is ultimately about putting our solar system in context,” he added. “We want to know if various aspects of our solar system are rare or common.”
The Kepler spacecraft launched in March 2009 on a mission to determine how commonly Earth-like planets occur around the Milky Way galaxy. To date, Kepler has detected more than 4,200 exoplanet candidates, 978 of which have been confirmed by follow-up observations or analysis. Mission team members think about 90 percent of the candidates will eventually turn out to be the real deal.
The telescope suffered a glitch in May 2013 that ended its original exoplanet hunt, but Kepler has embarked upon a new mission called K2, which calls for it to observe a range of cosmic objects and phenomena.