Page 820 | Astronomy Magazine (2024)

“Zombie” stars explode like bombs as they die, only to revive themselves by sucking matter out of other stars. According to an astrophysicist at the University of California, Santa Barbara (UCSB), this isn’t the plot for the latest 3-D blockbuster movie. Instead, it’s something that happens every day in the universe — something that can be used to measure dark energy.

This special category of stars, which explode as type Ia supernovae, helps probe the mystery of dark energy, which scientists believe fuels the expansion of the universe. Supernovae have been observed since at least A.D. 1054, when an exploding star formed the Crab Nebula, a supernova remnant.

Andy Howell from UCSB calls stars that have undergone a type Ia supernova “zombie” stars, because they’re dead with a core of ash, but can come back to life by sucking matter from a companion star. Over the past 50 years, astrophysicists have discovered that such stars are often part of binary systems — two stars orbiting each other. The one that explodes is a white dwarf star. “That’s what our Sun will be at the end of its life,” Howell said. “It will have the mass of the Sun crammed into the size of the Earth.”

The white dwarf stars that tend to explode as type Ia supernovae all have approximately the same mass. This was considered a fundamental limit of physics. However, in an article about 5 years ago, Howell reported stars that go beyond this limit. These previously unknown objects have more than the usual mass before they explode — a fact that confounds scientists.

Howell presented a hypothesis to understand this new class of objects. “One idea is that two white dwarfs could have merged together; the binary system could be two white dwarf stars,” he said. “Then, over time, they spiral into each other and merge. When they merge, they blow up. This may be one way to explain what is going on.”

Astrophysicists are using type Ia supernovae to build a map of the history of the universe’s expansion. “What we’ve found is that the universe hasn’t been expanding at the same rate,” said Howell. “And it hasn’t been slowing down as everyone thought it would be due to gravity. Instead, it has been speeding up. There’s a force that counteracts gravity and we don’t know what it is. We call it dark energy.”

Howell said that dark energy is probably a property of the fabric of the universe. “Space itself has some energy associated with it,” said Howell. “That’s what the results seem to indicate, that dark energy is distributed everywhere in space. It looks like it’s a property of the vacuum, but we’re not completely sure. We’re trying to figure out how sure we are of that; if we can improve type Ia supernovae as standard candles, we can make our measurements better.”

Throughout history, people have noticed a few supernovae so bright they could be seen with the naked eye. With telescopes, astronomers could discover supernovae farther away. “Now we have huge digital cameras on our telescopes, and really big telescopes,” said Howell. “We’ve been able to survey large parts of the sky, regularly. We find supernovae daily.”

“The next decade holds real promise of making serious progress in the understanding of nearly every aspect of these phenomena, from their explosion physics, to their progenitors, to their use as standard candles,” said Howell. “And with this knowledge may come the key to unlocking the darkest secrets of dark energy.”

“Zombie” stars explode like bombs as they die, only to revive themselves by sucking matter out of other stars. According to an astrophysicist at the University of California, Santa Barbara (UCSB), this isn’t the plot for the latest 3-D blockbuster movie. Instead, it’s something that happens every day in the universe — something that can be used to measure dark energy.

This special category of stars, which explode as type Ia supernovae, helps probe the mystery of dark energy, which scientists believe fuels the expansion of the universe. Supernovae have been observed since at least A.D. 1054, when an exploding star formed the Crab Nebula, a supernova remnant.

Andy Howell from UCSB calls stars that have undergone a type Ia supernova “zombie” stars, because they’re dead with a core of ash, but can come back to life by sucking matter from a companion star. Over the past 50 years, astrophysicists have discovered that such stars are often part of binary systems — two stars orbiting each other. The one that explodes is a white dwarf star. “That’s what our Sun will be at the end of its life,” Howell said. “It will have the mass of the Sun crammed into the size of the Earth.”

The white dwarf stars that tend to explode as type Ia supernovae all have approximately the same mass. This was considered a fundamental limit of physics. However, in an article about 5 years ago, Howell reported stars that go beyond this limit. These previously unknown objects have more than the usual mass before they explode — a fact that confounds scientists.

Howell presented a hypothesis to understand this new class of objects. “One idea is that two white dwarfs could have merged together; the binary system could be two white dwarf stars,” he said. “Then, over time, they spiral into each other and merge. When they merge, they blow up. This may be one way to explain what is going on.”

Astrophysicists are using type Ia supernovae to build a map of the history of the universe’s expansion. “What we’ve found is that the universe hasn’t been expanding at the same rate,” said Howell. “And it hasn’t been slowing down as everyone thought it would be due to gravity. Instead, it has been speeding up. There’s a force that counteracts gravity and we don’t know what it is. We call it dark energy.”

Howell said that dark energy is probably a property of the fabric of the universe. “Space itself has some energy associated with it,” said Howell. “That’s what the results seem to indicate, that dark energy is distributed everywhere in space. It looks like it’s a property of the vacuum, but we’re not completely sure. We’re trying to figure out how sure we are of that; if we can improve type Ia supernovae as standard candles, we can make our measurements better.”

Throughout history, people have noticed a few supernovae so bright they could be seen with the naked eye. With telescopes, astronomers could discover supernovae farther away. “Now we have huge digital cameras on our telescopes, and really big telescopes,” said Howell. “We’ve been able to survey large parts of the sky, regularly. We find supernovae daily.”

“The next decade holds real promise of making serious progress in the understanding of nearly every aspect of these phenomena, from their explosion physics, to their progenitors, to their use as standard candles,” said Howell. “And with this knowledge may come the key to unlocking the darkest secrets of dark energy.”

Galaxies once thought of as voracious tigers are more like grazing cows, according to a new study using NASA’s Spitzer Space Telescope.

Astronomers have discovered that galaxies in the distant universe continuously ingested their star-making fuel over long periods of time. This goes against previous theories that galaxies devoured their fuel in quick bursts after run-ins with other galaxies.

“Our study shows the merging of massive galaxies was not the dominant method of galaxy growth in the distant universe,” said Ranga-Ram Chary from NASA’s Spitzer Science Center at the California Institute of Technology in Pasadena, California. “We’re finding this type of galactic cannibalism was rare. Instead, we are seeing evidence for a mechanism of galaxy growth in which a typical galaxy fed itself through a steady stream of gas, making stars at a much faster rate than previously thought.”

According to Chary’s findings, these grazing galaxies fed steadily over periods of hundreds of millions of years and created an unusual amount of plump stars, up to 100 times the mass of our Sun.

“This is the first time that we have identified galaxies that supersize themselves by grazing,” said Hyunjin Shim from Spitzer Science Center. “They have many more massive stars than our Milky Way galaxy.”

Galaxies like our Milky Way are giant collections of stars, gas, and dust. They grow in size by feeding off gas and converting it to new stars. A long-standing question in astronomy is: Where did the distant galaxies that formed billions of years ago acquire this stellar fuel?

The most favored theory was that galaxies grew by merging with other galaxies, feeding off gas stirred up in the collisions.

Chary and his team addressed this question by using Spitzer to survey more than 70 remote galaxies that existed 1 to 2 billion years after the Big Bang. (Our universe is approximately 13.7 billion years old.) To the surprise of the astronomers, these galaxies were blazing with a type of light called H-alpha (Hα), radiation from hydrogen gas that has been hit with ultraviolet light from stars. High levels of Hα indicate rigorous star formation. Seventy percent of the surveyed galaxies show strong signs of the Hα signature in contrast to only 0.1 percent of galaxies in our local universe.

Previous studies using ultraviolet-light telescopes found about six times less star formation than Spitzer, which sees infrared light.

Scientists think this may be due to large amounts of obscuring dust, through which infrared light can sneak. Spitzer opened a new window onto the galaxies by taking long-exposure infrared images of a patch of sky called the GOODS fields, named for Great Observatories Origins Deep Survey.

Galaxies once thought of as voracious tigers are more like grazing cows, according to a new study using NASA’s Spitzer Space Telescope.

Astronomers have discovered that galaxies in the distant universe continuously ingested their star-making fuel over long periods of time. This goes against previous theories that galaxies devoured their fuel in quick bursts after run-ins with other galaxies.

“Our study shows the merging of massive galaxies was not the dominant method of galaxy growth in the distant universe,” said Ranga-Ram Chary from NASA’s Spitzer Science Center at the California Institute of Technology in Pasadena, California. “We’re finding this type of galactic cannibalism was rare. Instead, we are seeing evidence for a mechanism of galaxy growth in which a typical galaxy fed itself through a steady stream of gas, making stars at a much faster rate than previously thought.”

According to Chary’s findings, these grazing galaxies fed steadily over periods of hundreds of millions of years and created an unusual amount of plump stars, up to 100 times the mass of our Sun.

“This is the first time that we have identified galaxies that supersize themselves by grazing,” said Hyunjin Shim from Spitzer Science Center. “They have many more massive stars than our Milky Way galaxy.”

Galaxies like our Milky Way are giant collections of stars, gas, and dust. They grow in size by feeding off gas and converting it to new stars. A long-standing question in astronomy is: Where did the distant galaxies that formed billions of years ago acquire this stellar fuel?

The most favored theory was that galaxies grew by merging with other galaxies, feeding off gas stirred up in the collisions.

Chary and his team addressed this question by using Spitzer to survey more than 70 remote galaxies that existed 1 to 2 billion years after the Big Bang. (Our universe is approximately 13.7 billion years old.) To the surprise of the astronomers, these galaxies were blazing with a type of light called H-alpha (Hα), radiation from hydrogen gas that has been hit with ultraviolet light from stars. High levels of Hα indicate rigorous star formation. Seventy percent of the surveyed galaxies show strong signs of the Hα signature in contrast to only 0.1 percent of galaxies in our local universe.

Previous studies using ultraviolet-light telescopes found about six times less star formation than Spitzer, which sees infrared light.

Scientists think this may be due to large amounts of obscuring dust, through which infrared light can sneak. Spitzer opened a new window onto the galaxies by taking long-exposure infrared images of a patch of sky called the GOODS fields, named for Great Observatories Origins Deep Survey.

The European Space Agency’s (ESA) Integral gamma-ray observatory has provided results that will dramatically affect the search for physics beyond Einstein. It has shown that any underlying quantum “graininess” of space must be at much smaller scales than previously predicted.

Einstein’s general theory of relativity describes the properties of gravity and assumes that space is a smooth, continuous fabric. Yet quantum theory suggests that space should be grainy at the smallest scales, like sand on a beach.

One of the great concerns of modern physics is to marry these two concepts into a single theory of quantum gravity.

Now, Integral has placed stringent new limits on the size of these quantum “grains” in space, showing them to be smaller than some quantum gravity ideas would suggest.

According to calculations, the tiny grains would affect the way gamma rays travel through space. The grains should “twist” the light rays, changing the direction in which they oscillate, a property called polarization.

High-energy gamma rays should be twisted more than the lower-energy ones, and the difference in the polarization can be used to estimate the size of the grains.

Philippe Laurent from the Commission of Atomic Energy (CEA) in Saclay, France, and his collaborators used data from Integral’s IBIS instrument to search for the difference in polarization between high- and low-energy gamma rays emitted during one of the most powerful gamma-ray bursts (GRBs) ever seen.

GRBs come from some of the most energetic explosions known in the universe. Most are thought to occur when massive stars collapse into neutron stars or black holes during a supernova, leading to a huge pulse of gamma rays lasting just seconds or minutes, but briefly outshining entire galaxies.

GRB 041219A took place December 19, 2004, and was immediately recognized as being in the top 1 percent of GRBs for brightness. It was so bright that Integral was able to measure the polarization of its gamma rays accurately.

Laurent and colleagues searched for differences in the polarization at different energies, but found none to the accuracy limits of the data.

Some theories suggest that the quantum nature of space should manifest itself at the “Planck scale”: the minuscule 10^-35 of a meter, where a millimeter is 10^-3 (0.001) m.

However, Integral’s observations are about 10,000 times more accurate than any previous and show that any quantum graininess must be at a level of 10^-48 m or smaller.

“This is a very important result in fundamental physics and will rule out some string theories and quantum loop gravity theories,” said Laurent.

Integral made a similar observation in 2006 when it detected polarized emission from the Crab Nebula, the remnant of a supernova explosion just 6,500 light-years from Earth in our own galaxy.

This new observation is more stringent, however, because GRB 041219A was at a distance estimated to be at least 300 million light-years.

In principle, the tiny twisting effect due to the quantum grains should have accumulated over the large distance into a detectable signal. Because nothing was seen, the grains must be even smaller than previously suspected.

“Fundamental physics is a less obvious application for the gamma-ray observatory, Integral,” said Christoph Winkler from ESA. “Nevertheless, it has allowed us to take a big step forward in investigating the nature of space itself.”

Now, it’s over to the theoreticians, who must re-examine their theories in the light of this new result.

Astronomers are puzzled by the announcement that the masses of the largest objects in the universe appear to depend on which method is used to weigh them. The new work was presented at a specialist discussion meeting on “Scaling Relations of Galaxy Clusters” organized by the Astrophysics Research Institute (ARI) at Liverpool John Moores University and supported by the Royal Astronomical Society.

Clusters of galaxies are the largest gravitationally bound objects in the universe, containing thousands of galaxies like the Milky Way, and their weight is an important probe of their dark matter content and evolution through cosmic time. Measurements used to weigh these systems carried out in three different regions of the electromagnetic spectrum — X-ray, optical, and millimeter wavelengths — give rise to significantly different results.

Eduardo Rozo from the University of Chicago explained that any two of the measurements can be made to fit easily enough but that always leaves the estimate using the third technique out of line. Dubbed the “Axis of Evil,” it is as if the universe is being difficult by keeping back one or two pieces of the jigsaw and deliberately preventing researchers from calibrating our weighing scales properly.

More than 40 of the leading cluster astronomers from the United Kingdom, Europe, and the United States attended the meeting to discuss the early results from the Planck satellite, currently scanning the heavens at millimeter wavelengths, looking for the smallest signals from clusters of galaxies and the cosmic background radiation in order to understand the birth of the universe. The Planck measurements were compared with optical images of clusters from the Sloan Digitized Sky Survey and new X-ray observations from the XMM-Newton satellite.

ARI astronomers are taking a leading role in this research through participation in the X-ray cluster work and observations of the constituent galaxies using the largest ground-based optical telescopes.

One possible resolution to the “Axis of Evil” problem discussed at the meeting is a new population of clusters that is optically bright but also X-ray faint. Jim Bartlett from the University of Paris, who is one of the astronomers who presented the Planck results, argued that the prospect of a new cluster population that responds differently was a “frightening prospect” because it overturns age-old ideas about the gravitational physics being the same from cluster to cluster.

“I saw this meeting as an opportunity to bring together experts who study clusters at only one wavelength and don’t always talk to their colleagues working at other wavelengths,” said Chris Collins from ARI. “The results presented are unexpected, and all three communities — optical, X-ray, and millimeter — will need to work together in the future to figure out what is going on.”

Astronomers are puzzled by the announcement that the masses of the largest objects in the universe appear to depend on which method is used to weigh them. The new work was presented at a specialist discussion meeting on “Scaling Relations of Galaxy Clusters” organized by the Astrophysics Research Institute (ARI) at Liverpool John Moores University and supported by the Royal Astronomical Society.

Clusters of galaxies are the largest gravitationally bound objects in the universe, containing thousands of galaxies like the Milky Way, and their weight is an important probe of their dark matter content and evolution through cosmic time. Measurements used to weigh these systems carried out in three different regions of the electromagnetic spectrum — X-ray, optical, and millimeter wavelengths — give rise to significantly different results.

Eduardo Rozo from the University of Chicago explained that any two of the measurements can be made to fit easily enough but that always leaves the estimate using the third technique out of line. Dubbed the “Axis of Evil,” it is as if the universe is being difficult by keeping back one or two pieces of the jigsaw and deliberately preventing researchers from calibrating our weighing scales properly.

More than 40 of the leading cluster astronomers from the United Kingdom, Europe, and the United States attended the meeting to discuss the early results from the Planck satellite, currently scanning the heavens at millimeter wavelengths, looking for the smallest signals from clusters of galaxies and the cosmic background radiation in order to understand the birth of the universe. The Planck measurements were compared with optical images of clusters from the Sloan Digitized Sky Survey and new X-ray observations from the XMM-Newton satellite.

ARI astronomers are taking a leading role in this research through participation in the X-ray cluster work and observations of the constituent galaxies using the largest ground-based optical telescopes.

One possible resolution to the “Axis of Evil” problem discussed at the meeting is a new population of clusters that is optically bright but also X-ray faint. Jim Bartlett from the University of Paris, who is one of the astronomers who presented the Planck results, argued that the prospect of a new cluster population that responds differently was a “frightening prospect” because it overturns age-old ideas about the gravitational physics being the same from cluster to cluster.

“I saw this meeting as an opportunity to bring together experts who study clusters at only one wavelength and don’t always talk to their colleagues working at other wavelengths,” said Chris Collins from ARI. “The results presented are unexpected, and all three communities — optical, X-ray, and millimeter — will need to work together in the future to figure out what is going on.”

By tracking atmospheric features on Neptune, a University of Arizona scientist has accurately determined the planet’s rotation, a feat that had not been previously achieved for any of the gas planets in our solar system except Jupiter.

A day on Neptune lasts precisely 15 hours, 57 minutes, and 59 seconds, according to the first accurate measurement of its rotational period made by Erich Karkoschka from University of Arizona, Tucson.

His result is one of the largest improvements in determining the rotational period of a gas planet in almost 350 years since Italian astronomer Giovanni Cassini made the first observations of Jupiter’s Red Spot.

“The rotational period of a planet is one of its fundamental properties,” said Karkoschka. “Neptune has two features observable with the Hubble Space Telescope that seem to track the interior rotation of the planet. Nothing similar has been seen before on any of the four giant planets.”

Unlike the rocky planets — Mercury, Venus, Earth, and Mars — which behave like solid balls spinning in a rather straightforward manner, the giant gas planets — Jupiter, Saturn, Uranus and Neptune — rotate more like giant blobs of liquid. Because they are believed to consist of mainly ice and gas around a relatively small solid core, their rotation involves a lot of sloshing, swirling, and roiling, which has made it difficult for astronomers to get an accurate grip on exactly how fast they spin around.

“If you looked at Earth from space, you’d see mountains and other features on the ground rotating with great regularity, but if you looked at the clouds, they wouldn’t because the winds change all the time,” Karkoschka said. “If you look at the giant planets, you don’t see a surface, just a thick cloudy atmosphere.”

“On Neptune, all you see is moving clouds and features in the planet’s atmosphere. Some move faster, some move slower, some accelerate, but you really don’t know what the rotational period is, if there even is some solid inner core that is rotating.”

In the 1950s, when astronomers built the first radio telescopes, they discovered that Jupiter sends out pulsating radio beams, like a lighthouse in space. Those signals originate from a magnetic field generated by the rotation of the planet’s inner core.

No clues about the rotation of the other gas giants, however, were available because any radio signals they may emit are being swept out into space by the solar wind and never reach Earth.

“The only way to measure radio waves is to send spacecraft to those planets,” Karkoschka said. “When Voyager 1 and 2 flew past Saturn, they found radio signals and clocked them at exactly 10.66 hours, and they found radio signals for Uranus and Neptune, as well. So based on those radio signals, we thought we knew the rotation periods of those planets.”

But when the Cassini probe arrived at Saturn 15 years later, its sensors detected its radio period had changed by about 1 percent.
Karkoschka said that because of its large mass, it was impossible for Saturn to incur that much change in its rotation over such a short time.

“Because the gas planets are so big, they have enough angular momentum to keep them spinning at pretty much the same rate for billions of years,” he said. “So something strange was going on.”

Even more puzzling was Cassini’s later discovery that Saturn’s northern and southern hemispheres appear to be rotating at different speeds.

“That’s when we realized the magnetic field is not like clockwork but slipping,” Karkoschka said. “The interior is rotating and drags the magnetic field along, but because of the solar wind or other, unknown influences, the magnetic field cannot keep up with respect to the planet’s core and lags behind.”

Instead of spacecraft powered by billions of dollars, Karkoschka took advantage of what one might call the scraps of space science — publicly available images of Neptune from the Hubble Space Telescope archive. With determination and patience, he then pored over hundreds of images, recording every detail and tracking distinctive features over long periods of time.

Other scientists before him had observed Neptune and analyzed images, but nobody had sleuthed through 500 of them.

“When I looked at the images, I found Neptune’s rotation to be faster than what Voyager observed,” Karkoschka said. “I think the accuracy of my data is about 1,000 times better than what we had based on the Voyager measurements — a huge improvement in determining the exact rotational period of Neptune, which hasn’t happened for any of the giant planets for the last 3 centuries.”

Two features in Neptune’s atmosphere, Karkoschka discovered, stand out in that they rotate about 5 times more steadily than even Saturn’s hexagon, the most regularly rotating feature known on any of the gas giants.

Named the South Polar Feature and the South Polar Wave, the features are likely vortices swirling in the atmosphere, similar to Jupiter’s famous Red Spot, which can last for a long time due to negligible friction. Karkoschka was able to track them over the course of more than 20 years.

An observer watching the massive planet turn from a fixed spot in space would see both features appear exactly every 15.9663 hours, with less than a few seconds of variation.

“The regularity suggests those features are connected to Neptune’s interior in some way,” Karkoschka said. “How they are connected is up to speculation.”

One possible scenario involves convection driven by warmer and cooler areas within the planet’s thick atmosphere, analogous to hot spots within the Earth’s mantle, giant circular flows of molten material that stay in the same location over millions of years.

“I thought the extraordinary regularity of Neptune’s rotation indicated by the two features was something really special,”
Karkoschka said.

“So I dug up the images of Neptune that Voyager took in 1989, which have better resolution than the Hubble images, to see whether I could find anything else in the vicinity of those two features. I discovered six more features that rotate with the same speed, but they were too faint to be visible with the Hubble Space Telescope, and visible to Voyager only for a few months, so we wouldn’t know if the rotational period was accurate to the six digits. But they were really connected. So now we have eight features that are locked together on one planet, and that is really exciting.”

In addition to getting a better grip on Neptune’s rotational period, the study could lead to a better understanding of the giant gas planets in general.

“We know Neptune’s total mass but we don’t know how it is distributed,” Karkoschka said. “If the planet rotates faster than we thought, it means the mass has to be closer to the center than we thought. These results might change the models of the planets’ interior and could have many other implications.”

In December 2010, a pair of mismatched stars in the southern constellation Crux whisked past each other at a distance closer than Venus orbits the Sun. The system possesses a so-far unique blend of a hot, massive star with a compact fast-spinning pulsar. The pair’s closest encounters occur every 3.4 years, each marked by a sharp increase in gamma rays, the most extreme form of light.

The unique combination of stars, the long wait between close approaches, and periods of intense gamma-ray emission make this system irresistible to astrophysicists. Now, a team using NASA’s Fermi Gamma-ray Space Telescope to observe the 2010 encounter reports that the system displayed fascinating and unanticipated activity.

“Even though we were waiting for this event, it still surprised us,” said Aous Abdo from George Mason University in Fairfax, Virginia.

Few pairings in astronomy are as peculiar as high-mass binaries, where a hot blue-white star many times the Sun’s mass and temperature is joined by a compact companion no bigger than Earth — and likely much smaller. Depending on the system, this companion may be a burned-out star known as a white dwarf, a city-sized remnant called a neutron star — also known as a pulsar — or, most exotically, a black hole.

Just four of these “odd couple” binaries were known to produce gamma rays, but in only one of them did astronomers know the nature of the compact object. That binary consists of a pulsar designated PSR B1259-63 and a 10th-magnitude Be-type star known as LS 2883. The pair lies 8,000 light-years away.

The pulsar is a fast-spinning neutron star with a strong magnetic field. This combination powers a lighthouse-like beam of energy, which astronomers can easily locate if the beam happens to sweep toward Earth. The beam from PSR B1259-63 was discovered in 1989 by the Parkes radio telescope in Australia. The neutron star is about the size of Washington, D.C., weighs about twice the Sun’s mass, and spins almost 21 times per second.

The pulsar follows an eccentric and steeply inclined orbit around LS 2883, which weighs roughly 24 solar masses and spans about nine times its size. This hot blue star sits embedded in a disk of gas that flows out from its equatorial region.

At closest approach, the pulsar passes less than 63 million miles (101 million kilometers) from its star — so close that it skirts the gas disk around the star’s middle. The pulsar punches through the disk on the inbound leg of its orbit. Then it swings around the star at closest approach and plunges through the disk again on the way out.

“During these disk passages, energetic particles emitted by the pulsar can interact with the disk, and this can lead to processes that accelerate particles and produce radiation at different energies,” said Simon Johnston from the Australia Telescope National Facility in Epping, New South Wales. “The frustrating thing for astronomers is that the pulsar follows such an eccentric orbit that these events only happen every 3.4 years.”

In anticipation of the December 15, 2010, closest approach, astronomers around the world mounted a multiwavelength campaign to observe the system over a broad energy range, from radio wavelengths to the most energetic gamma rays detectable.

“When you know you have a chance of observing this system only once every few years, you try to arrange for as much coverage as you can,” said Abdo, the principal investigator of the NASA-funded international campaign. “Understanding this system, where we know the nature of the compact object, may help us understand the nature of the compact objects in other, similar systems.”

Despite monitoring of the system with the EGRET telescope aboard NASA’s Compton Gamma-Ray Observatory in the 1990s, gamma-ray emission in the billion-electron-volt (GeV) energy range had never been seen from the binary.

Late last year, as the pulsar headed toward its massive companion, the Large Area Telescope (LAT) aboard Fermi discovered faint gamma-ray emission.

“During the first disk passage, which lasted from mid-November to mid-December, the LAT recorded faint yet detectable emission from the binary,” Abdo said. “We assumed that the second passage would be similar, but in mid-January 2011, as the pulsar began its second passage through the disk, we started seeing surprising flares that were many times stronger than those we saw before.”

Stranger still, the system’s output at radio and X-ray energies showed nothing unusual as the gamma-ray flares raged.

“The most intense days of the flare were January 20 and 21 and February 2, 2011,” said Abdo. “What really surprised us is that on any of these days, the source was more than 15 times brighter than it was during the entire month-and-a-half-long first passage.”

“One great advantage of the Fermi LAT observations is the continuous monitoring of the source, which gives us the most complete gamma-ray observations of this system,” said Julie McEnery from NASA’s Goddard Space Flight Center in Greenbelt, Maryland.

Astronomers are continuing to analyze their bounty of data and working to understand the surprising flares. And in May 2014, when the pulsar once again approaches its giant companion, they’ll be watching.

Space shuttle Atlantis‘ Commander Chris Ferguson and his three crewmates are scheduled to begin a 12-day mission to the International Space Station with a launch July 8 at 11:26 a.m. EDT from NASA’s Kennedy Space Center in Florida. The STS-135 mission is the final flight of the Space Shuttle Program.

The launch date was announced June 28 at the conclusion of a flight readiness review at Kennedy. During the meeting, senior NASA and contractor managers assessed the risks associated with the mission and determined the shuttle and station’s equipment, support systems, and personnel are ready.

Atlantis‘ STS-135 mission will deliver the Raffaello multipurpose logistics module filled with supplies and spare parts to sustain space station operations after the shuttles are retired.

The mission also will fly the Robotic Refueling Mission (RRM), an experiment designed to demonstrate and test tools, technologies, and techniques needed to robotically refuel satellites in space — even satellites not designed to be serviced. The crew also will return an ammonia pump that recently failed on the station. Engineers want to understand why the pump failed and improve designs for future spacecraft.

Space shuttle Atlantis‘ Commander Chris Ferguson and his three crewmates are scheduled to begin a 12-day mission to the International Space Station with a launch July 8 at 11:26 a.m. EDT from NASA’s Kennedy Space Center in Florida. The STS-135 mission is the final flight of the Space Shuttle Program.

The launch date was announced June 28 at the conclusion of a flight readiness review at Kennedy. During the meeting, senior NASA and contractor managers assessed the risks associated with the mission and determined the shuttle and station’s equipment, support systems, and personnel are ready.

Atlantis‘ STS-135 mission will deliver the Raffaello multipurpose logistics module filled with supplies and spare parts to sustain space station operations after the shuttles are retired.

The mission also will fly the Robotic Refueling Mission (RRM), an experiment designed to demonstrate and test tools, technologies, and techniques needed to robotically refuel satellites in space — even satellites not designed to be serviced. The crew also will return an ammonia pump that recently failed on the station. Engineers want to understand why the pump failed and improve designs for future spacecraft.

A team of European astronomers has used the European Southern Observatory’s (ESO) Very Large Telescope (VLT) and a host of other telescopes to discover and study the most distant quasar found to date. This brilliant beacon, powered by a black hole with a mass two billion times that of the Sun, is by far the brightest object yet discovered in the early universe.

“This quasar is a vital probe of the early universe,” said Stephen Warren from Imperial College London. “It is a very rare object that will help us to understand how supermassive black holes grew a few hundred million years after the Big Bang.”

Quasars are bright, distant galaxies that are believed to be powered by supermassive black holes at their centers. Their brilliance makes them powerful beacons that may help to probe the era when the first stars and galaxies were forming. The newly discovered quasar is so far away that its light probes the last part of the reionization era.

The quasar that has just been found, named ULAS J1120+0641, is seen as it was only 770 million years after the Big Bang. It took 12.9 billion years for its light to reach us.

Although more distant objects have been confirmed, such as a gamma-ray burst at redshift 8.2 and a galaxy at redshift 8.6, the newly discovered quasar is hundreds of times brighter than these.
Amongst objects bright enough to be studied in detail, this is the most distant by a large margin.

The next most distant quasar is seen as it was 870 million years after the Big Bang (redshift 6.4). Similar objects farther away cannot be found in visible-light surveys because their light, stretched by the expansion of the universe, falls mostly in the infrared part of the spectrum by the time it gets to Earth. The European UKIRT Infrared Deep Sky Survey (UKIDSS), which uses the United Kingdom’s dedicated infrared telescope in Hawaii, was designed to solve this problem. The team of astronomers hunted through millions of objects in the UKIDSS database to find those that could be the long-sought distant quasars, and eventually struck gold.

“It took us 5 years to find this object,” said Bram Venemans from ESO, Garching, Germany. “We were looking for a quasar with redshift higher than 6.5. Finding one that is this far away, at a redshift higher than 7, was an exciting surprise. By peering deep into the reionization era, this quasar provides a unique opportunity to explore a 100-million-year window in the history of the cosmos that was previously out of reach.”

The distance to the quasar was determined from observations made with the FORS2 instrument on ESO’s VLT and instruments on the Gemini North Telescope. Because the object is comparatively bright, it is possible to take a spectrum of it, which involves splitting the light from the object into its component colors. This technique allowed the astronomers to find out quite a lot about the quasar.

These observations showed that the mass of the black hole at the center of ULAS J1120+0641 is about two billion times that of the Sun. This high mass is hard to explain so early on after the Big Bang. Current theories for the growth of supermassive black holes predict a slow build-up in mass as the compact object pulls in matter from its surroundings.

“We think there are only about 100 bright quasars with redshift higher than 7 over the whole sky,” said Daniel Mortlock from Imperial College London. “Finding this object required a painstaking search, but it was worth the effort to be able to unravel some of the mysteries of the early universe.”

Waukesha, Wis. — All matter and antimatter should have annihilated each other and formed an enormous flash of radiation early in the universe’s history. But matter survived. Could matter and antimatter have slightly different properties, which allowed matter to beat antimatter?

In the August 2011 issue of Astronomy magazine, science journalist Alexander Hellemans explores these questions and what scientists have learned in the past century about antimatter. Antimatter research has especially come a long way in the past decade: A 2001 “discovery of particle-antiparticle pairs that disintegrate at different rates reinforced the idea that matter and antimattter have different properties,” writes Hellemans. Now that the Large Hadron Collider in Europe is up and running, scientists anticipate even more discoveries.

For more information about antimatter and ongoing experiments to uncover its mysteries, pick up the August issue of Astronomy, on newsstands July 5.

“Storm warning”
What’s the weather like on the other planets in our solar system? In “Storm warning,” science journalist and artist Michael Carroll overviews Venus’ broken thermostat, the Red Planet’s polar caps, intriguing colors in Saturn’s cloud decks, and other meteorological features of our planetary system. Scientists can then use information about the other planets to understand Earth’s meteorological system.

“What happened to science education?”
Associate Editor Bill Andrews examines the sad state of science education in the United States and why we should care in “What happened to science educaiton?”. “The level of science education in this country has apparently sunk so low that a significant portion of the populace doesn’t even know how to distinguish verified data from personal opinion, and no one seems to care,” writes Andrews. He explains how we follow the scientific method in daily life, and offers recommendations to help improve science education.

“Why teens should care about astronomy”
Today’s youth seem to put stargazing on the backburner. But some teenagers, like author Ayla Besemer, enjoy astronomy — from the myths behind the constellations, to the pictures telescopes return and the latest scientific discoveries. She shares her love of the night sky, and why she thinks other kids should seek out space in “Why teens should care about astronomy.”

August night-sky events visible without optical aid

The European Space Agency’s (ESA) XMM-Newton space observatory has watched a faint star flare up at X-ray wavelengths to almost 10,000 times its normal brightness. Astronomers believe the outburst was caused by the star trying to eat a giant clump of matter.

The flare took place on a neutron star, the collapsed heart of a once much larger star. Now about 6 miles (10 kilometers) in diameter, the neutron star is so dense that it generates a strong gravitational field.

The clump of matter was much larger than the neutron star and came from its enormous blue supergiant companion star.

“This was a huge bullet of gas that the star shot out, and it hit the neutron star allowing us to see it,” said Enrico Bozzo from University of Geneva, Switzerland.

The flare lasted 4 hours and the X-rays came from the gas in the clump as it was heated to millions of degrees while being pulled into the neutron star’s intense gravity field. In fact, the clump was so big that not much of it hit the neutron star. Yet, if the neutron star had not been in its path, this clump would probably have disappeared into space without a trace.

XMM-Newton caught the flare during a scheduled 12.5-hour observation of the system, which is known only by its catalog number IGR J18410-0535, but the astronomers were unaware of their catch.

The telescope works through a sequence of observations carefully planned to make the best use of the space observatory’s time, then sends the data to Earth.

It was about 10 days after the observation that Bozzo and his colleagues received the data and quickly realized they had something special. Not only were they pointing in the right direction to see the flare, but also the observation had lasted long enough for them to see it from beginning to end.

“I don’t know if there is any way to measure luck, but we were extremely lucky,” said Bozzo. He estimates that an X-ray flare of this magnitude can be expected a few times a year at the most for this particular star system.

The duration of the flare allowed them to estimate the size of the clump. It was much larger than the star, probably 10 million miles (16 million km) across, or about 100 billion times the volume of the Moon. Yet, according to the estimate made from the flare’s brightness, the clump contained only one-thousandth of our natural satellite’s mass.

These figures will help astronomers understand the behavior of the blue supergiant and the way it emits matter into space. All stars expel atoms into space, creating a stellar wind. The X-ray flare shows that this particular blue supergiant does it in a clumpy fashion, and the estimated size and mass of the cloud allow constraints to be placed on the process.

“This remarkable result highlights XMM-Newton’s unique capabilities,” comments Norbert Schartel, XMM-Newton Project Scientist. “Its observations indicate that these flares can be linked to the neutron star attempting to ingest a giant clump of matter.”

The European Space Agency’s (ESA) XMM-Newton space observatory has watched a faint star flare up at X-ray wavelengths to almost 10,000 times its normal brightness. Astronomers believe the outburst was caused by the star trying to eat a giant clump of matter.

The flare took place on a neutron star, the collapsed heart of a once much larger star. Now about 6 miles (10 kilometers) in diameter, the neutron star is so dense that it generates a strong gravitational field.

The clump of matter was much larger than the neutron star and came from its enormous blue supergiant companion star.

“This was a huge bullet of gas that the star shot out, and it hit the neutron star allowing us to see it,” said Enrico Bozzo from University of Geneva, Switzerland.

The flare lasted 4 hours and the X-rays came from the gas in the clump as it was heated to millions of degrees while being pulled into the neutron star’s intense gravity field. In fact, the clump was so big that not much of it hit the neutron star. Yet, if the neutron star had not been in its path, this clump would probably have disappeared into space without a trace.

XMM-Newton caught the flare during a scheduled 12.5-hour observation of the system, which is known only by its catalog number IGR J18410-0535, but the astronomers were unaware of their catch.

The telescope works through a sequence of observations carefully planned to make the best use of the space observatory’s time, then sends the data to Earth.

It was about 10 days after the observation that Bozzo and his colleagues received the data and quickly realized they had something special. Not only were they pointing in the right direction to see the flare, but also the observation had lasted long enough for them to see it from beginning to end.

“I don’t know if there is any way to measure luck, but we were extremely lucky,” said Bozzo. He estimates that an X-ray flare of this magnitude can be expected a few times a year at the most for this particular star system.

The duration of the flare allowed them to estimate the size of the clump. It was much larger than the star, probably 10 million miles (16 million km) across, or about 100 billion times the volume of the Moon. Yet, according to the estimate made from the flare’s brightness, the clump contained only one-thousandth of our natural satellite’s mass.

These figures will help astronomers understand the behavior of the blue supergiant and the way it emits matter into space. All stars expel atoms into space, creating a stellar wind. The X-ray flare shows that this particular blue supergiant does it in a clumpy fashion, and the estimated size and mass of the cloud allow constraints to be placed on the process.

“This remarkable result highlights XMM-Newton’s unique capabilities,” comments Norbert Schartel, XMM-Newton Project Scientist. “Its observations indicate that these flares can be linked to the neutron star attempting to ingest a giant clump of matter.”

In my previous column, I showed you how to combine a Hydrogen-alpha (Hα) image with luminance exposures to create a “Hα-luminance hybrid.” Now I want to go further and look at a way to combine the Hα with the color-rich LRGB data.

In August’s article “Understanding antimatter,” author Alexander Hellemans explains what antimatter is, overviews its discovery history, and writes why it’s important to learn more about this missing material. In order to study it, however, physicists need to find it — or create it. And creating it is exactly what they’re doing.