The Atacama Large Millimeter/submillimeter Array (ALMA) is a telescope array in Chile that includes 66 receivers scattered across the Atacama Desert. The array is located at the European Southern Observatory and bills itself as “the largest astronomical project in existence.”
ALMA is able to peer through the dust that obscures planetary systems under construction, or to look back at stars and galaxies that formed in the early days of the universe and emit their radiation in millimeter light — waves that are about 1,000 times longer than visible-light wavelengths.
Although there are other observatories that can do the same thing, what distinguishes ALMA is its sheer size and number of receivers. Working together, they provide more sensitivity in astronomical observations and allow astronomers to look at the universe in high definition.
ALMA can be viewed as an amalgamation of three separate projects under conception: the Millimeter Array (MMA) of the United States, the Large Southern Array (LSA) of Europe and the Large Millimeter Array (LMA) of Japan. Through conversations between researchers, scientists concluded it would be easier to collaborate on one large project rather than creating several smaller ones.
The first large milestone occurred in 1997, when the European Southern Observatory (ESO) and the National Radio Astronomy Observatory (NRAO) agreed to merge MMA and LSA, a move they formalized in 1999. The ALMA agreement between the entities was subsequently signed in February 2003, with Japan joining in 2004.
ESO — which already has facilities in Chile — negotiated an agreement with the country to build ALMA at Llano de Chajnantor, a high-altitude site that would make it easier to observe the cosmos because the atmosphere is thinner there. In exchange, Chile received 10 percent observing time and additional “cultural, educational and production activities,” according to ALMA. The $1.3 billion cost was borne principally by North America and Europe, with Japan close behind.
Contracts for the antennas were awarded in 2005, with the first antenna coming to Chile in 2007. As antennas arrived and were checked for health and interferometry capabilities, ESO put out a call for the first science observations. Antennas began moving to Chajnantor in 2009, and observations began with a partially completed ALMA in 2011. The 66th and final receiver was installed in 2013.
ALMA’s extreme altitude is an aid in performing observations. Its highest receivers are about 16,500 feet (5,000 meters) above sea level, far above much of the atmosphere and water vapor that can make it hard to see what’s in the sky. Astronomers work in a facility at 9,500 feet (2,900 m), where they receive supplemental oxygen if they’re going to stay awhile.
The 66 receivers can be arranged in many different configurations, ranging from very close together to quite spread apart. At its greatest, the receivers can be moved as far as 9.9 miles (16 kilometers) apart. Each telescope receives information individually, then transmits the data to a supercomputer that combines the information to trace the signal direction — a high-tech version of how human ears combine to locate a sound.
This technology allows astronomers to look at three principal questions, according to ALMA’s website: the nature of the universe’s first stars and galaxies, how planets and stars come together, and what the chemistry is of the gas and dust clouds that may eventually collapse to form planets and stars.
“Many other astronomical specialties also will benefit from the new capabilities of ALMA,” the website added, such as the ability to “map gas and dust in the Milky Way and other galaxies, investigate ordinary stars, analyze gas from an erupting volcano on Jupiter’s moon, Io [and] study the origin of the solar wind.”
The first image from ALMA was a combined view of the Antennae Galaxies, which are about 75 million light-years from Earth. Another early image pierced dust surrounding the Centaurus A galaxy to show its bright center. The telescope is also capable of producing three-dimensional visualizations of gas, such as the image above of NGC 253 (the Sculptor Galaxy) released in 2013.
One of ALMA’s most prominent finds was announced in 2014 from examining a famed supernova remnant — the leftovers of supernova 1987A — and uncovering dust spewing in the area.
“We have found a remarkably large dust mass concentrated in the central part of the ejecta from a relatively young and nearby supernova,” astronomer Remy Indebetouw, of NRAO and the University of Virginia, said in a statement. “This is the first time we’ve been able to really image where the dust has formed, which is important in understanding the evolution of galaxies.”
A baby star was captured on camera in 2013 showing the youngster blasting out starstuff at 84,477 mph (144,000 kph). Once the material crashed into the surrounding gas, it produced a glow. This could provide some clues as to how the sun came together, astronomers said at the time. “The sun is a star, so if we want to understand how our solar system was created, we need to understand how stars are formed,” Héctor Arce, the lead author of the Astrophysical Journal study, said in a statement.
The formation of stars determines where new planetary systems can arise as well as the structure and evolution of galaxies. Learning more about star formation could help scientists understand the remaining mysteries about the birth of galaxies, including how the supermassive black holes at their hearts apparently originated so early in the universe’s history.
A dearth of data on the way matter is distributed within star-forming clouds has limited the accuracy of star formation models. Now scientists have developed a way to determine these details by using so-called dust-extinction maps, or observations of how dust scatters and absorbs light.
The birth of stars
Stars are born when pockets of gas and dust within interstellar molecular clouds exceed critical density and collapse under their own gravity. Once the pressure and the temperature inside get high enough for nuclear fusion to ignite, it creates a star. The rate at which stars form depends mainly on the number and density of these clumps within stellar nurseries.
Scientists have now used one feature of these clouds to better understand star formation. As the light of distant stars penetrates through a stellar nursery, the molecular cloud’s dust dims the light. By measuring how this process dims thousands of different stars, scientists can reconstruct the cloud’s 3D structure, helping pinpoint how matter is distributed within the cloud.
Using data from 16 nearby molecular clouds, each within about 850 light-years of Earth, “we could devise a very concrete recipe for how new stars are born in the interstellar gas clouds,” study lead author Jouni Kainulainen, an astrophysicist at the Max Planck Institute for Astronomy in Heidelberg, Germany, told Space.com. “And the ingredients of this recipe are simple to understand — only those regions in the clouds in which density is higher than about 5,000 molecules per cubic centimeter produce stars, and about a tenth of the gas in these regions collapses into the new stars.”
A clue for cosmic clouds
One key consequence of these findings “is that we have given astronomers a new tool to estimate the rates at which molecular clouds form stars, without even seeing the new stars in the clouds,” Kainulainen said. “I quote my collaborator Thomas Henning — ‘Show us your image of a cloud, and we can tell you how much it forms stars right now.’”
Such a capability “gives us a great possibility to use new, powerful telescopes such as the Atacama Large Millimeter/submillimeter Array (ALMA) to observe gas clouds in the galaxy and better map its star-formation capacity,” Kainulainen said. ALMA consists of 66 high-precision microwave antennas spread over distances of up to 10 miles (16 kilometers) in the Chilean desert, which can act like a single, high-resolution telescope. The array has just commenced operations.
Intriguingly, the researchers found it was simpler for stars to form in these clouds than once predicted by theory. But the findings have yet to address the question of how galaxies and supermassive black holes formed in the early universe, Kainulainen said. “I think it is currently too early to speculate about the possible effects of our findings to the early universe,” he said.
“We have to remember that physical conditions during the early galaxy formation were quite different from those of the galaxies today,” Kainulainen said. “It would be an unreasonable leap in conclusions to assume that the process of star formation would proceed exactly in the same way as in the current, local universe. Our results are best applicable to spiral galaxies such as the Milky Way in the local universe.”
Future studies should address the assumptions made in creating the team’s 3D models for the molecular clouds, Kainulainen said. “It is a good topic for future discussions — how this 3D modeling could potentially be improved,” he said. “I hope we will have comments and ideas from other scientists regarding this.”
Future research could determine what processes are most responsible for shaping molecular clouds.
“We know today very well that processes such as gravitational forces and magneto-hydrodynamic turbulence have a key role in shaping the clouds,” Kainulainen said. “With the parameters we have derived, we can answer questions such as, ‘In which regions is the cloud structure most crucially affected by turbulence, and in which by gravity?’ Such questions are of great importance in understanding the origin of interstellar gas clouds in galaxies and their evolution.”
Galaxies — those vast collections of stars that populate our universe — are all over the place. Perhaps the most resonant example of this fact is the Hubble eXtreme Deep Field, a collection of photographs from the Hubble Space Telescope revealing thousands of galaxies in a single composite picture.
Estimating how many galaxies are throughout the universe is a tougher job, however. Sheer numbers is one problem — once the count gets into the billions, it takes a while to do the addition. Another problem is the limitation of our instruments. To get the best view, a telescope needs to have a large aperture (the diameter of the main mirror or lens) and be located above the atmosphere to avoid distortion from Earth’s air.
While estimates among different experts vary, an acceptable range is between 100 billion and 200 billion galaxies, Mario Livio, an astrophysicist at the Space Telescope Science Institute in Baltimore, told Space.com.
To the best of Livio’s knowledge, Hubble is the best instrument available for galaxy counting and estimation. The telescope, launched in 1990, initially had a distortion on its main mirror that was corrected during a shuttle visit in 1993. Hubble also went underwent several upgrades and service visits until the final shuttle mission there in May 2009.
In 1995, astronomers pointed the telescope at what appeared to be an empty region of Ursa Major, and collected 10 days’ worth of observations. The result was an estimated 3,000 faint galaxies in a single frame, going as dim as 30th magnitude. (For comparison, the North Star or Polaris is at about 2nd magnitude.) This image composite was called the Hubble Deep Field and was the furthest anyone had seen into the universe at the time. [Related: Brightest Stars: Luminosity & Magnitude]
As the Hubble telescope received upgrades to its instruments, astronomers repeated the experiment twice. In 2003 and 2004, scientists created the Hubble Ultra Deep Field, which in a million-second exposure revealed about 10,000 galaxies in a small spot in the constellation Fornax.
In 2012, again using upgraded instruments, scientists used the telescope to look at a portion of the Ultra Deep Field. Even in this narrower field of view, astronomers were able to detect about 5,500 galaxies. Researchers dubbed this the eXtreme Deep Field.
All in all, Hubble reveals an estimated 100 billion galaxies in the universe or so, but this number is likely to increase to about 200 billion as telescope technology in space improves, Livio said.
Whatever instrument is used, the method of estimating the number of galaxies is the same. You take the portion of sky imaged by the telescope (in this case, Hubble). Then — using the ratio of the sliver of sky to the entire universe — you can determine the number of galaxies in the universe.
“This is assuming that there is no large cosmic variance, that the universe is homogenous,” Livio said. “We have good reasons to suspect that is the case. That is the cosmological principle.”
The principle dates back to Albert Einstein’s theory of general relativity at the turn of the last century. One of general relativity’s findings is that gravity is a distortion of space and time. With that understanding in hand, several scientists (including Einstein) tried to understand how gravity affected the entire universe.
“The simplest assumption to make is that if you viewed the contents of the universe with sufficiently poor vision, it would appear roughly the same everywhere and in every direction,” NASA stated. “That is, the matter in the universe is homogeneous and isotropic when averaged over very large scales. This is called the cosmological principle.”
One example of the cosmological principle at work is the cosmic microwave background, radiation that is a remnant of the early stages of the universe after the Big Bang. Using instruments such as NASA’s Wilkinson Microwave Anisotropy Probe, astronomers have found the CMB is virtually identical wherever one looks.
Would the number of galaxies change with time?
Measurements of the universe’s expansion — through watching galaxies race away from us — show that it is about 13.82 billion years old. As the universe gets older and bigger, however, galaxies will recede farther and farther from Earth. This will make them more difficult to see in telescopes.
The universe is expanding faster than the speed of light (which does not violate Einstein’s speed limit because the expansion is of the universe itself, rather than of objects traveling through the universe). Also, the universe is accelerating in its expansion.
This is where the concept of the “observable universe” — the universe that we can see — comes into play. In 1 trillion to 2 trillion years, Livio said, this means that there will be galaxies that are beyond what we can see from Earth.
“We can only see light from galaxies whose light had enough time to reach us,” Livio said. “It doesn’t mean that that’s all there is in the universe. Hence, the definition of the observable universe.”
Galaxies also change over time. The Milky Way is on a collision course with the nearby Andromeda Galaxy, and both will merge in about 4 billion years. Later on, other galaxies in our Local Group — the galaxies closest to us — will eventually combine. Residents of that future galaxy would have a much darker universe to observe, Livio said.
“Civilizations started then, they would have no evidence that there was a universe with 100 billion galaxies,” he said. “They would not see the expansion. They would probably not be able to tell there was a Big Bang.”
What about other universes?
As the early universe inflated, there are some theories that say that different “pockets” broke away and formed different universes. These different places could be expanding at different rates, include other types of matter, and have different physical laws than our own universe.
Livio pointed out there could be galaxies in these other universes — if they exist — but we have no way right now of knowing for sure. So the number of galaxies could even be greater than 200 billion, when considering other universes.
In our own cosmos, Livio said, astronomers will be better able to refine the number upon the launch of the James Webb Space Telescope (for which his institute will manage the mission operations and science). Hubble is able to peer back at galaxies that formed about 450 million years after the Big Bang. After James Webb launches in 2018, astronomers anticipate they can look as far back as 200 million years after the Big Bang.
“The numbers are not going to change much,” Livio added, pointing out the first galaxies probably formed not too long before that. “So a number like 200 billion [galaxies] is probably it for our observable universe.”
The central black holes in dwarf galaxies — the “seeds” that grow into the monsters at the core of the Milky Way and other large galaxies — are probably surprisingly weighty, containing 1,000 to 10,000 times the mass of our sun, a new study reports.
The finding goes against one popular theory of supermassive black hole evolution, suggesting that galaxy mergers aren’t necessary to create these behemoths, which can harbor billions of times more mass than the sun.
“We still don’t know how the monstrous black holes that reside in galaxy centers formed,” lead author Shobita Satyapal, of George Mason University in Virginia, said in a statement. “But finding big black holes in tiny galaxies shows us that big black holes must somehow have been created in the early universe, before galaxies collided with other galaxies.”
It’s also possible that supermassive black holes grow primarily by gobbling up gas and dust, getting bigger relatively sedately along with their host galaxies, researchers said.
Satyapal and her colleagues analyzed observations of dwarf galaxies made by NASA’s Wide-field Infrared Survey Explorer spacecraft, or WISE.
Dwarf galaxies have changed relatively little over time, and they resemble the types of galaxies that existed when the universe was young. So they’re a good place to look for nascent supermassive black holes, researchers said.
WISE’s all-sky survey picked out hundreds of dwarf galaxies, which appear to sport strikingly large black holes.
“Our findings suggest the original seeds of supermassive black holes are quite massive themselves,” Satyapal said.
While the results are intriguing, follow-up study will be necessary to fully flesh them out, outside researchers said.
“Though it will take more research to confirm whether the dwarf galaxies are indeed dominated by actively feeding black holes, this is exactly what WISE was designed to do: find interesting objects that stand out from the pack,” astronomer Daniel Stern, of NASA’s Jet Propulsion Laboratory in Pasadena, Calif., said in a statement. Stern was not part of the study team.
WISE launched to Earth orbit in December 2009 on a 10-month mission to scan the entire sky in infrared light. It was shut down in February 2011, then reactivated in September 2013 with a new mission and a new name. Now called NEOWISE, the spacecraft is hunting for potentially dangerous asteroids, some of which could be promising targets for human exploration.
The new study was published in the March issue of The Astrophysical Journal.
The first direct evidence of cosmic inflation — a period of rapid expansion that occurred a fraction of a second after the Big Bang — also supports the idea that our universe is just one of many out there, some researchers say.
On Monday (March 17), scientists announced new findings that mark the first-ever direct evidence of primordial gravitational waves — ripples in space-time created just after the universe began. If the results are confirmed, they would provide smoking-gun evidence that space-time expanded at many times the speed of light just after the Big Bang 13.8 billion years ago.
The new research also lends credence to the idea of a multiverse. This theory posits that, when the universe grew exponentially in the first tiny fraction of a second after the Big Bang, some parts of space-time expanded more quickly than others. This could have created “bubbles” of space-time that then developed into other universes. The known universe has its own laws of physics, while other universes could have different laws, according to the multiverse concept.
“It’s hard to build models of inflation that don’t lead to a multiverse,” Alan Guth, an MIT theoretical physicist unaffiliated with the new study, said during a news conference Monday. “It’s not impossible, so I think there’s still certainly research that needs to be done. But most models of inflation do lead to a multiverse, and evidence for inflation will be pushing us in the direction of taking [the idea of a] multiverse seriously.”
Other researchers agreed on the link between inflation and the multiverse.
“In most of the models of inflation, if inflation is there, then the multiverse is there,” Stanford University theoretical physicist Andrei Linde, who wasn’t involved in the new study, said at the same news conference. “It’s possible to invent models of inflation that do not allow [a] multiverse, but it’s difficult. Every experiment that brings better credence to inflationary theory brings us much closer to hints that the multiverse is real.”
When Guth and his colleagues thought up cosmic inflation more than 30 years ago, scientists thought it was untestable. Today, however, researchers are able to study light left over from the Big Bang called cosmic microwave background radiation (CMB).
In the new study, a team led by John Kovac of the Harvard-Smithsonian Center for Astrophysics found telltale signs of inflation in the microwave background. The researchers discovered a distinct curl in the polarization pattern of the CMB, a sign of gravitational waves created by the rapid expansion of space-time just after the Big Bang.
Linde, one of the main contributers to inflation theory, says that if the known universe is just one bubble, there must be many other bubbles in the cosmic fabric.
“Think about some unstable state,” Linde explained. “You are standing on a hill, and you can fall in this direction, you can fall in that direction, and if you’re drunk, eventually you must fall. Inflation is instability of our space with respect to its expansion.
“You have something growing exponentially,” he added. “If you just let it go … it will continue exponentially growing, so this [the known universe] is one possibility of something going wrong with this instability, which is very, very right for us because it has created all of our space. Now, we know that if anything can go wrong, it will go wrong once and a second time and a third time and into infinity as long as it can go.”
Hundreds of wandering “rogue” black holes may dwell in the Milky Way — and now researchers say they know how to detect them. Discovering these strange objects could shed light on the formation of the Milky Way and other galaxies.
No one knows exactly how the Milky Way came to exist. But according to one popular model of galaxy formation, the building blocks of the Milky Way were dwarf galaxies that collided and merged shortly after the Big Bang.
This idea assumes that floating black holes, each containing 1,000 to 100,000 more mass than the sun, could be left over from those early cosmic times — fossil evidence for the growth and mergers of black holes in the infant universe. [The Strangest Black Holes in the Universe]
Each of the Milky Way’s building-block galaxies had its own central black hole. During mergers between dwarf galaxies, these black holes also came together. In the process, the new single black hole received a rocket-like kick from the emission of excess gravitational waves in the opposite direction, said astrophysicist Avi Loeb of Harvard University, who wrote the paper together with his graduate student Xiawei Wang.
In most cases, this kick would make the black hole speed up enough to move it away from its newly enlarged dwarf galaxy — but not far enough to leave the region that eventually would become the Milky Way. (A new central black hole could then form in the dwarf galaxy via gas accretion.)
Once the host galaxy became massive enough, the black holes near it would have been unable to escape. One of them grew and became the supermassive black hole that is believed to exist at the center of the Milky Way, weighing four million suns. But there should be hundreds of rogue black holes floating in the distant “halo” of the Milky Way, left over from the pre-Milky Way time when only dwarf galaxies existed, Loeb said.
“The Milky Way halo serves as a kind of a ‘reservoir’ of wandering black holes that originally lived in the cores of the small galaxies that merged to make it,” he said.
Black Hole Quiz: How Well Do You Know Nature’s Weir…
Bow shock detection
But how does one detect them, if it is impossible to observe black holes directly, and they are”rogues” floating somewhere in space? Loeb and Wang say they have founda way.
“When such black holes pass through the gas disk of the Milky Way galaxy, they produce a bow shock — similar to the sonic boom produced intheair by supersonic jets,” said Loeb. “The shock accelerates electrons to high energies and these emit radio waves that we can detect.”
“And the radio emission from these bow shocks should be detectable with existing radio observatories,” he added. “Of course, if such a bow shock is discovered, one would be able to also observe the cluster of stars attached to the floating black hole and possibly the X-ray emission from the black hole itself as it accretes gas.”
This method would be”a nice new way to identify the theoretically predicted [wandering black holes],” said astrophysicist Jeremy Darling of the University of Colorado, who did not take part in the study. “The Wang and Loeb paper shows how these black holes can create a bow shock as they pass through the disk of our galaxy, effectively lighting up and making themselves available for observation.”
And he agrees that in principle, these bow shocks should be “easily detectable with current facilities,” using radio and infrared waves.
But it won’t be easy, cautions Darling, as the difficulty is “the ‘needle-in-a-haystack” problem common in astronomy: There are many objects emitting in the radio and infrared range in the disk of our galaxy, and Wang and Loeb predict that only a few black holes (in some scenarios maybe not even a single one) should be in the disk at any given time.
“Moreover, we view our galaxy edge-on, so there is tremendous confusion as objects overlap one another and pile up along the line of sight. Extant radio surveys of the galaxy lack the angular resolution to distinguish the black hole bow shock from other phenomena, which is a pity.”
During earlier research, Loeb and his former student Ryan O’Leary proposed another way to detect these floating black holes. They suggested that such black holes are likely surrounded by a cluster of stars that were originally tightly bound to them.
These clusters would bevery different from globular star clusters, as they would be held together by the gravity of the black hole. As a result, they would be very compact, just a few light-years in size.
Loeb and O’Leary have identified candidate star clusters and are currently collecting spectroscopic data on some,to test if any of them has a central black hole.
“There may be a treasure trove in the backyard of the Milky Way that could inform us about the first generation of black holes in the universe,” Loeb said.
The oceans soured into a deadly sulfuric-acid stew after the huge asteroid impact that wiped out the dinosaurs, a new study suggests.
Eighty percent of the planet’s species died off at the end of the Cretaceous Period 65.5 million years ago, including most marine life in the upper ocean, as well as swimmers and drifters in lakes and rivers. Scientists blame this mass extinction on the asteroid or comet impact that created the Chicxulub crater in the Gulf of Mexico.
A new model of the disaster finds that the impact would have inundated Earth’s atmosphere with sulfur trioxide, from sulfate-rich marine rocks called anhydrite vaporized by the blast. Once in the air, the sulfur would have rapidly transformed into sulfuric acid, generating massive amounts of acid rain within a few days of the impact, according to the study, published today (March 9) in the journal Nature Geoscience.
The model helps explain why most deep-sea marine life survived the mass extinction while surface dwellers disappeared from the fossil record, the researchers said. The intense acid rainfall only spiked the upper surface of the ocean with sulfuric acid, leaving the deeper waters as a refuge. The model could also account for another extinction mystery: the so-called fern spike, revealed by a massive increase in fossil fern pollen just after the impact. Ferns are one of the few plants that tolerate ground saturated in acidic water, the researchers said.
The Chicxulub impact devastated the Earth with more than just acid rain. Other killer effects included tsunamis, a global firestorm and soot from burning plants. [The 10 Best Ways to Destroy Earth]
The ocean-acidification theory has been put forth before, but some scientists questioned whether the impact would have produced enough global acid rain to account for the worldwide extinction of marine life. For example, the ejected sulfur could have been sulfur dioxide, which tends to hang out in the atmosphere instead of forming aerosols that become acid rain.
Lead author Sohsuke Ohno, of the Chiba Institute of Technology in Japan, and his co-authors simulated the Chicxulub impact conditions in a lab, zapping sulfur-rich anhydrite rocks with a laser to mimic the forces of an asteroid colliding with Earth. The resulting vapor was mostly sulfur trioxide, rather than sulfur dioxide, the researchers found. In Earth’s atmosphere, the sulfur trioxide would have quickly combined with water to form sulfuric acid aerosols. These aerosols played a key role in quickly getting sulfur out of the sky and into the ocean, the researchers said. The tiny droplets likely stuck to pulverized silicate rock debris raining down on the planet, thus removing sulfuric acid from the atmosphere in just a matter of days.
“Our experimental results indicate that sulfur trioxide is expected to be the major sulfide component in the sulfur oxide gas released during the impact,” Ohno told Live Science in an email interview. “In addition to that, by the scavenging or sweeping out of acid aerosols by coexisting silicate particles, sulfuric acid would have settled to the ground surface within a very short time,” Ohno said.
For the first time, astronomers have directly measured how fast a black hole spins, clocking its rotation at nearly half the speed of light.
The distant supermassive black hole would ordinarily be too faint to measure, but a rare lineup with a massive elliptical galaxy created a natural telescope known as a gravitational lens that allowed scientists to study the faraway object.
“The gravitational lens is crucial,” study co-author Mark Reynolds of the University of Michigan told Space.com via email..”Without this, we would not be able to collect X-ray photons to measure the spin of a black hole that is so distant.”
Nature’s free telescope
Just more than 6 billion light-years from Earth, a supermassive black hole powers the quasar . Quasars, the most luminous objects in the universe, shine brightly across vast distances, fed by material that falls into their black holes.
Black holes are massive objects whose gravitational pull is so powerful that even light cannot escape their grasp. Most form when a star at the end of its lifetime explodes, its outer core collapsing into a tiny dense ball.
Supermassive black holes have masses millions of times that of the sun and are found at the center of most galaxies, including the Milky Way. Their origins are still unknown.
The only features scientists are able to measure about the voracious objects are their mass and spin. Astronomers can determine the mass of a black hole by measuring its interactions with gas and other objects, but characterizing its rotation has remained a challenge, especially for more distant supermassive black holes.
In the new study, a team led by Rubens Reis of the University of Michigan used NASA’s Chandra X-ray Observatory and the European Space Agency’s XMM-Newton — the largest X-ray space telescopes currently available — to observe the X-rays generated in the innermost regions of the disk of material circling and feeding the supermassive black hole that powers the quasar J1131.
Measuring the radius of the disk allowed the astronomers to calculate the black hole’s spin speed, which was almost half the speed of light.
The team would have been unable to measure the spin without a rare lineup in space. A giant elliptical galaxy lies between Earth and the quasar J1131. The huge galaxy acts as a gravitational lens to bend and magnify objects that lie behind it — in this case, the supermassive black hole.
“It acts like a telescope, but a free one provided by nature,” Reynolds said.
“Such a quadruple lens of a quasar is a very rare object,” Guido Risaliti, of the Harvard-Smithsonian Center for Astrophysics, told Space.com in an email. “Until a few years ago, none of them was known.”
Risaliti, who was not involved in the research, also studies supermassive black holes. Last year, he made the first reliable measurement of the spin of a nearby supermassive black hole. He authored a News & Views article that appeared along with the research in the journal Nature today (March 5). [No Escape: Dive Into a Black Hole (Infographic)]
The spin of a supermassive black hole can reveal information about how it accretes the material it consumes. To achieve a rapid spin, material must fall into the black hole in a direction similar to its rotation, ultimately revving it up like a child spinning a merry-go-round.
A slower spin indicates that the gas and dust supplying the black hole fall into it from multiple directions, spinning the black hole up or down depending on whether it comes in with or against the rotation. In this case, the random influx of material acts like a child alternating pushing and pulling the merry-go-round.
The quick spin of J1131 indicates that the black hole is being fed by a bountiful supply of gas and dust. These large volumes could be provided by collisions and mergers between galaxies, among other sources, Reynolds said.
A slower spin and more haphazard feeding process would be caused by material arriving in spurts, from interstellar gas clouds and stars wandering too close from a variety of directions.
“Observational studies over the past 20 years have shown a clear link between the mass of the supermassive black hole at the center of a galaxy and the properties of the galaxy in which it resides,” Reynolds said. “These relations suggest a symbiotic relationship between the central black hole and its host galaxy.”
By studying the black hole, astronomers can learn more about the origin and evolution of galaxies — and spin plays a very important role.
“The growth history of a supermassive black hole is encoded in its spin,” Reynolds said.
High spin values throughout most black holes would suggest that galaxy mergers have played a significant role in galactic evolution throughout the life of the universe. Determining how common rapid spin rates are will require the study of multiple distant supermassive black holes that lie in the active galactic nuclei (AGN) of nearby galaxies.
“The next immediate step is to obtain a few more black hole spins in the nearby AGN, but it will be difficult to repeat observations like the one of Reis’ team due to the rarity of these sources,” Risaliti said. “The big step forward will be the measurements of the black hole spins with the next generation of high sensitivity X-ray telescopes, such as the ESA’s Athena.”
In-pouring rivers of hydrogen gas could explain how spiral galaxies maintain the constant star formation that dominates their hearts, a new study reports.
Using the Green Bank Telescope (GBT) in West Virginia, scientists observed a tenuous filament of gas streaming into the galaxy NGC 6946, known as the “Fireworks Galaxy” because of the large number of supernovae observed within it. The find may provide insight into the source of fuel that powers the ongoing birth of young stars, researchers said.
“We knew that the fuel for star formation had to come from somewhere,” study lead author D.J. Pisano, of West Virginia University, said in a statement. “So far, however, we’ve detected only about 10 percent of what would be necessary to explain what we observe in many galaxies.”
Located 22 million light-years from Earth on the border of the constellations Cepheus and Cygnus, NGC 6946 is a medium-sized spiral galaxy pointed face-on toward the Milky Way.
Previous studies revealed a halo of hydrogen gas around NGC 6946 common to spiral galaxies. Such halos are formed by hydrogen ejected from the galaxies by star formation and violent supernova explosions. These interactions heat the gas in the halo to extreme temperatures.
When Pisano turned the GBT toward the spiral galaxy for further examination, however, he discovered a ribbon of gastoo cool to have suffered the heating processes undergone by halo gas.
On average, the Milky Way churns out between 1 to 5 new stars per year. Rich in gas, NGC 6946 is far more active. For example, it has hosted at least 9 explosive supernovae in the past century.
“Starburst” galaxies are even more prolific. These productive galaxiesshould have burned through the gas they were born with over the course of their lifetimes, bringing star formation to a sudden halt. Instead, the process continues today, suggesting that something is continuing to supply them with sufficient gas to keep creating more stars.
“A leading theory is that rivers of hydrogen — known as cold flows — may be ferrying hydrogen through intergalactic space, clandestinely fueling star formation,” Pisano said. “But this tenuous hydrogen has simply been too diffuse to detect, until now.”
The immense, unblocked dish of the Green Bank Telescope, combined with its location in the National Radio Quiet Zone, where radio transmissions are limited, allow the large disk to detect the faint hydrogen signal that would be present in a cold flow.
Another possibility is that the hydrogen detected originated from a close encounter with another galaxy in the past. The gravitational interaction between the two could have stretched out a ribbon of neutral atomic hydrogen, researchers said. Such a ribbon would contain stars that astronomers should be able to easily observe, though none have yet been spotted. Further studies of the streamer hydrogen gas will help clarify its role.
After decades of wondering why young massive stars don’t blow away the gas surrounding them, astronomers have finally found a process that explains how these stellar youngsters hang on to their gassy envelopes.
This star type — more than 10 times the mass of the sun and most active in ultraviolet light — begins shining as a gigantic gas cloud collapses, fusing hydrogen into helium and igniting the star’s nuclear engine. The new research shows that this gas accretion continues even as the star shines, counteracting the stellar radiation that “pushes” against the gas.
A new model reveals that the gas falls unevenly onto the star and also clumps into spiral “filamentary concentrations” because there is so much gas in a small area. When the star moves through the spirals, these filaments absorb the ultraviolet radiation the star emits, protecting the surrounding gas. Once the absorption stops, the gas nebulas shrink. [Top 10 Star Mysteries]
“These transitions from rarefied to dense gas and back again occur quickly compared to most astronomical events,” Mac Low, a curator in the American Museum of Natural History’s Department of Astrophysics and co-author of the paper, said in a statement. “We predicted that measurable changes could occur over times as short as a few decades.”
Massive stars only influential not only when they are alive but also when they die. When a star of this size finishes burning the elements inside it, this triggers a massive collapse and explosion known as a supernova. These explosions created all elements in the universe that are heavier than iron, making Earth and other rocky planets possible.
Young massive stars have been closely studied for decades. Nobody could figure out why the gas around them didn’t blow away, however, as simpler models used previously implied that the gas would expand and dissipate.
The new models, based on observations from the Karl G. Jansky Very Large Array (VLA) in New Mexico, suggest that there are many small ionized hydrogen regions around these stars. The accretion process on the star kept going even after the hydrogen hotspots had formed, which was the opposite of what astronomers expected. Using models, astronomers then supposed that the gas falls unevenly on the star, creating the filaments.
Researchers came to this conclusion after using VLA observations of Sagittarius B2, a huge gas and dust cloud almost 400 light-years away from the center of the Milky Way galaxy. Between observations made in 1989 and 2012, researchers spotted four ionized hydrogen or HII regions getting brighter.
“The long-term trend is still the same, that HII regions expand with time,” said study leader Christopher De Pree, an astronomer at Agnes Scott College. “But in detail, they get brighter or get fainter and then recover. Careful measurements over time can observe this more detailed process.”
The research was recently published in Astrophysical Journal Letters and is also available in preprint form on Arxiv.
For the first time, astronomers have precisely calculated the rotation rate of a galaxy by measuring the tiny movements of its constituent stars.
Observations by NASA’s Hubble Space Telescope reveal that the central part of the nearby Large Magellanic Cloud galaxy (LMC) completes one rotation every 250 million years — coincidentally, the same amount of time it takes the sun finish a lap around the core of our own Milky Way.
“Studying this nearby galaxy by tracking the stars’ movements gives us a better understanding of the internal structure of disk galaxies,” study co-author Nitya Kallivayalil, of the University of Virginia, said in a statement today (Feb. 18). “Knowing a galaxy’s rotation rate offers insight into how a galaxy formed, and it can be used to calculate its mass.”
The Large Magellanic Cloud is one of the Milky Way’s nearest neighbors, located just 170,000 light-years away. The LMC has a central bar but an irregular shape, suggesting that it was once a Milky Way-like spiral that has been bent out of shape by gravitational interactions.
In the new study, the research team used Hubble’s Wide Field Camera 3 and Advanced Camera for Surveys to measure the motion of hundreds of LMC stars over a seven-year period. Hubble is the only instrument precise enough to make such observations, scientists said.
“This precision is crucial, because the apparent stellar motions are so small because of the galaxy’s distance,” lead author Roeland van der Marel, of the Space Telescope Science Institute in Baltimore, said in a statement. “You can think of the LMC as a clock in the sky, on which the hands take 250 million years to make one revolution. We know the clock’s hands move, but even with Hubble we need to stare at them for several years to see any movement.”
The new Hubble data complement previous observations of the LMC, which estimated the galaxy’s rotation rate by measuring shifts in the spectrum of its starlight, researchers said. (The light from stars moving toward Earth shifts slightly toward the blue end of the spectrum, while that from stars receding from our planet appears redder.)
The LMC is an attractive target for astronomers interested in galactic structure and evolution, since it’s close enough to observe in detail but far enough away to take in completely.
“The LMC is a very important galaxy because it is very near to our Milky Way,” van der Marel said. “Studying the Milky Way is very hard because everything you see is spread all over the sky. It’s all at different distances, and you’re sitting in the middle of it. Studying structure and rotation is much easier if you view a nearby galaxy from the outside.”
Astronomers have found what appears to be one of the oldest known stars in the universe.
The ancient star formed not long after the Big Bang 13.8 billion years ago, according to Australia National University scientists. The star (called SMSS J031300.362670839.3) is located 6,000 light-years from Earth and formed from the remains of a primordial star that was 60 times more massive than the sun.
“This is the first time that we’ve been able to unambiguously say that we’ve found the chemical fingerprint of a first star,” lead scientist Stefan Keller, of the ANU Research School of Astronomy and Astrophysics, said in a statement. “This is one of the first steps in understanding what those first stars were like. What this star has enabled us to do is record the fingerprint of those first stars.” [See amazing photos of supernova explosions]
Scientists think SMSS J031300.362670839.3 is probably at least 13 billion years old, though they do not know its exact age, Anna Frebel, an MIT astronomer associated with the research, said
Keller and his team found that the star actually has an unexpected composition. Astronomers thought that primordial stars — like the one that SMSS J031300.362670839.3 formed from — died in huge supernova explosions that spread large amounts of iron throughout space.
However, the new observations have shown that SMSS J031300.362670839.3′s composition harbors no iron pollution. Instead, the star is mostly polluted by lighter elements like carbon, ANU officials said.
“This indicates the primordial star’s supernova explosion was of surprisingly low energy,” Keller said. “Although sufficient to disintegrate the primordial star, almost all of the heavy elements such as iron, were consumed by a black hole that formed at the heart of the explosion.”
The scientists also found that the early star’s composition is very different from the sun.
“To make a star like our sun, you take the basic ingredients of hydrogen and helium from the Big Bang and add an enormous amount of iron — the equivalent of about 1,000 times the Earth’s mass,” Keller said. “To make this ancient star, you need no more than an Australia-sized asteroid of iron and lots of carbon. It’s a very different recipe that tells us a lot about the nature of the first stars and how they died.”
Because of its low mass, the star, located in the Milky Way, has a long lifetime, Anna Frebel, an MIT astronomer associated with the research, told Space.com via email.
Keller and his team found SMSS J031300.362670839.3 by using the ANU SkyMapper telescope. SkyMapper is surveying the sky at the Siding Spring Observatory in Australia to produce the first-ever digital map of the sky in the Southern Hemisphere. They confirmed their observations using the Magellan telescope in Chile.
Black holes acting as companions to early stars may have taken more time to raise the temperature of the ancient universe than previously thought, a new study suggests.
Scientists found that the energy streaming from these early pairings took longer to raise the temperature of the universe, which means astronomers could detect signs of the heating process previously thought to be out of bounds. Two cosmic milestones occurred in the universe a few hundred million years after the Big Bang— dominating hydrogen gas was both heated and made transparent.
“Previously, it was thought that these two milestones are well separated in time, and thus in observational data as well,” study co-author Rennan Barkana, of Tel Aviv University, told Space.com via email. [The History and Structure of the Universe (Infographic Slideshow)]
Barkana worked with lead study author Anastasia Fialkov, also of Tel Aviv University, and Eli Visbal, of Columbia University, to determine that the heating most likely overlapped the early, and perhaps middle, part of reionization, the process that allowed the events of the early universe to become visible to scientists today, making the heating potentially observable to astronomers today.
High energy, low heat
Like stars today, stars in the early universe often had companions. When one of the two companion stars exploded to create a black hole, the new system — known as an X-ray binary (XRB) — emitted energy in the X-ray spectra. Although other systems emit X-rays, XRBs are the brightest, dominating the total cosmic intensity of X-rays.
In the early universe, energetic X-rays served to heat the hydrogen gas that filled space. Previously, scientists suspected that low-energy X-rays provided the energy to heat the early universe. But recent improved models of XRBs revealed that high-energy X-rays dominated the scene.
Fialkov’s team used new models to recalculate the amount of time required to increase the temperature of the hydrogen spread throughout the universe. Surprisingly, the researchers said, the higher-energy X-rays took longer to raise temperatures than the less-powerful rays.
“High-energy X-rays typically travel a long distance, over a long time, before their energy is absorbed and heats the gas,” Barkana said. “Eventually, all their energy is deposited, but ‘eventually’ is too late in the early universe, when galaxy and star formation are ramping up.”
After the Big Bang, protons and neutrons joined together to form neutral hydrogen, the most basic element on the periodic table and the dominate gas in the universe. The dominance of neutral hydrogen rendered the universe opaque, in a period known as the cosmic ‘Dark Ages’ that existed during the first 100 million years after the Big Bang. Only after stars and galaxies began to form and release ultraviolet light did the universe begin the process of reionization, clearing the hydrogen gas and making the universe once again transparent.
The early stars didn’t manage to clear the darkness of the early universe until nearly a billion years had passed since the Big Bang. As a result, astronomers cannot peer through the darkness to observe the first billion years in the life of the 13.8-billion-year-old universe.
With low-energy X-rays dominating the scene, hydrogen gas in the early universe would have heated quickly as it absorbed energy. Under this model, scientists would not be able to observe any signs of the heating, which would have finished before reionization was complete.
But the slowdown caused by the presence of high-energy X-rays means that the heating should overlap the spreading transparency, allowing scientists to capture glimpses of the process.
The research was published online today (Feb. 5) in the journal Nature.
Observing the unobservable
Several radio telescopes have been constructed with the goal of observing the properties of the first stars and galaxies. The Low-Frequency Array in the Netherlands, the Precision Array for Probing the Epoch of Reionization in South Africa, and the Murchison Widefield Array in Western Australia all study the 21-centimeter (8.3 inches) wavelength, the frequency where hydrogen emission can be observed. Other telescopes are currently in the works, including the Square Kilometer Array (SKA), the 5,000-mile-wide (8,000 kilometers) grouping of telescopes spreading across South Africa and Australia.
According to experimental cosmologist Judd Bowman of Arizona State University, telescopes like the SKA should be able to detect signals emitted from the heating of the early universe, if the designers take the new research into account.
In a companion News and Views article published in the same issue of Nature, Bowman wrote, “The results should prompt astrophysicists to reconsider the wavelength range that the telescopes will target.”
Bowman, who was not part of the recent study, studies the early universe and the 21-cm line.
Though engineers designed the arrays under the assumption that reionization would be visible to the radio telescopes, the new discovery suggests that these instruments may be able to detect signs of heating by early black holes once thought to be out of reach.
Made up predominantly of gas when spotted while the Milky Way was only about 3 billion years old, the galaxy, DLA2222-0946, should one day evolve into a common spiral galaxy like the Milky Way. Yet its commonness is what makes it so important, as it should provide insights into the formation of the bulk of galaxies early in the life of the universe.
“It’s sort of extraordinary for being ordinary,” Regina Jorgenson, of the University of Hawaii, said in early January at a press conference at the American Astronomical Society meeting in Washington, D.C.
Jorgenson and her team used the Keck Telescope in Hawaii to obtain the first spatially resolved images of these young, normal galaxies. Although their existence has been known for decades, they have been a challenge to clearly resolve.
“It’s equivalent to detecting a 50-watt light bulb on Mars,” Jorgenson said.
Early galaxies contained primarily dust, the food for star formation. Jorgenson compared the process of galaxy formation to baking a cake, which requires a lot of different ingredients, the most of important of which is flour. In a galactic cake, the flour is equivalent to neutral gas, the prime fuel for star formation.
Gas doesn’t shine like stars, so astronomers had to get creative to find it in distant space. Enter a quasar, a very bright and distant astronomical source. As light from a quasar passes through these kinds of galactic systems known as DLAs, scientists can take measurements of the clouds of gas that make them up.
“These DLAs contain most of the neutral gas in the universe at the time,” Jorgenson said. “They contain most of the flour.”
But the single line of sight provided by the quasar limits how much of the galaxy can be seen. Jorgenson compared it to a single car headlight in a cloudbank. Adding to the challenge, the quasar whose bright light illuminates the galaxy also outshines it, making other emissions from the young group difficult to detect.
The team utilized used the advanced technologies of the Keck telescope to resolve the image and spectra, the measure of its separated energy wavelengths, of DLA2222-0946. Keck allowed for a significant improvement in resolution.
“It’s akin to reading the President’s newspaper in the White House [from] six miles away,” she said.
The results will be published in an upcoming edition of the Astrophysical Journal.
‘Baby Milky Ways’
Located approximately 10.8 billion light-years from the Milky Way, DLA2222-0946 formed about 3 billion years after the Big Bang (the universe is estimated to be roughly 13.8 billion years old).
When spotted, it looked nothing like the spreading spirals of the Milky Way. The young galaxy is only one-sixth the size of our galaxy and 1/200th the mass. However, the massive supply of gas contained within it means it produces about 10 times as many stars as our galaxy.
Because looking over broad distances in space is akin to looking back through time, scientists are able to see the DLA the way it appeared 10.8 billion years ago. Over time, these ‘baby Milky Way galaxies,’ as Jorgenson termed them, likely grew into galaxies that resemble our own. A clear resolution of DLA2222-0946 and other DLAs will provide insight into the evolutionary steps taken by galaxies like the Milky Way.
“This is something astronomers have been trying to do for over thirty years,” said Jorgenson.
The map shows the weather on the surface of WISE J104915.57-531906.1B (called Luhman 16B for short), the nearest brown dwarf to Earth at 6.5 light-years away. Scientists mapped the light and dark features of the failed star’s surface, according to officials with the European Southern Observatory, whose Very Large Telescope in Chile contributed to the new science. You can take video tour of the brown dwarf and its weather map on SPACE.com.
Brown dwarfs are called failed stars because they are larger than gas giant planets like Jupiter, yet still too small to produce nuclear fusion like a true star. Scientists have only found a few hundred of the odd objects, with the first confirmed 20 years ago, ESO officials said. [See more photos of strange brown dwarfs]
“Previous observations have inferred that brown dwarfs have mottled surfaces, but now we can start to directly map them,” the new study’s lead author, Ian Crossfield of the Max Planck Institute for Astronomy, said in a statement. “What we see is presumably patchy cloud cover, somewhat like we see on Jupiter.”
Crossfield and his team found that Luhman 16B probably harbors gaseous clouds made of iron and other minerals in a mostly hydrogen atmosphere. The brown dwarf rotates fully about every four hours. Weather on the brown dwarf would not be favorable for humans, however. Temperatures soar to about 2,000 degrees Fahrenheit (1,100 degrees Celsius), Max Planck officials said.
Luhman 16B is one in a pair of brown dwarfs in the southern constellation of Vela, the sail. Its brighter counterpart is known as Luhman 16A. In another study, scientists were able to dissect what is happening in different atmospheric layers on both Luhman 16B and Luhman 16A.
The two brown dwarfs were first discovered in 2013 using data from NASA’s WISE space telescope, which maps the sky in infrared light.
Scientists used Doppler imaging to create the Luhman 16B weather map, which somewhat resembles satellite weather views of Earth, Max Planck officials wrote in a news release.
“In the future, we will be able to watch cloud patterns form, evolve and dissipate — eventually, maybe exo-meteorologists will be able to predict whether a visitor to Luhman 16B can expect clear or cloudy skies,” Crossfield said in a statement.
By examining weather on brown dwarfs, scientists might be able to better understand how the atmospheres of giant planets outside of the solar system work, researchers have said.
“We’ve learned that the weather patterns on these brown dwarfs are quite complex,” Beth Biller, leader of the second study detailing the atmospheric layers, said in a statement. “The cloud structure of the brown dwarf varies quite strongly as a function of atmospheric depth and cannot be explained with a single layer of clouds.”
The brown dwarf surface-mapping results appear in the journal Nature, and the atmospheric layer results are in Astrophysical Journal Letters.
Crossfield and his team have developed a foldable oragami version of the Luhman 16B map. You can download the plans and fold your own brown dwarf here: http://www.mpia.de/Public/menu_q2e.php?Aktuelles/PR/2014/PR_2014_02/PR_2014_02_en.html