Universe Today

January 10, 2008December 26, 2015 by Fraser Cain

Black Holes Seen Spinning at the Limits Predicted by Einstein

The supermassive black holes that lurk at the hearts of the most massive galaxies might be spinning faster than astronomers ever thought. In fact, they might be spinning at the very limits predicted by Einstein’s theory of relativity. Perhaps it’s this extreme rotational speed that generates the energetic jets that blast out of the most massive and active galaxies.

Astronomers used NASA’s Chandra X-Ray Observatory to study 9 giant galaxies that seem to contain rapidly spinning supermassive black holes. These galaxies have large disturbances in their gaseous atmosphere, so the researchers calculated that these black holes must be spinning at near their maximum rates.

“We think these monster black holes are spinning close to the limit set by Einstein’s theory of relatively, which means that they can drag material around them at close to the speed of light,” said Rodrigo Nemmen, a visiting graduate student at Penn State University.

According to Einstein, when a black hole rotates at extreme speeds, it can actually catch up the surrounding space time and make that rotate as well. This effect, linked with the inflowing streams of gas can produce rotating, tightly wound towers of powerful magnetic fields. These fields channel the energy and inflowing gas into powerful jets which blast away from the black hole at nearly the speed of light.

It’s believed that black holes can acquire these extreme rotational speeds when galaxies merge. Fresh material falling onto the black hole just boosts its speed higher and higher until it reaches the hard limits allowed by relativity.

And it’s this extreme rate of spin that forms the power source for the jets. With the number of powerful jets seen pouring out of many galaxies, it might be that most supermassive black holes are spinning at extreme rates; we just haven’t detected them yet.

Supermassive black holes can be very disruptive to their local environments. The jets pump enormous amounts of energy into their surroundings, heating up gas. Since stars can only form when there are large clouds of cold gas, these process of heating can stall star formation in the host galaxy.

Astronomers want to work out the relationship between supermassive black holes and the rates of star formation in the most massive galaxies in the Universe.

Original Source: Chandra News Release

January 10, 2008December 29, 2015 by Fraser Cain

Carnival of Space #36

While we’re here blogging our little hearts away at the 211th meeting of the American Astronomical Society, Steinn Sigurdsson is back at home herding all the dynamic news cats we left behind. This week he’s the lucky host for the 36th Carnival of Space, and has pulled together a compelling list of interesting stories for your reading pleasure.

Get the scoop on India’s space plans, read reviews of 200 lunar exploration stories, and see what the quadrantids looked like out the window of an airplane.

Click here to visit the Carnival of Space #36.

And if you’re interested in looking back, here’s an archive to all the past carnivals of space. If you’ve got a space-related blog, you should really join the carnival. Just email an entry to [email protected], and the next host will link to it. It will help get awareness out there about your writing, help you meet others in the space community – and community is what blogging is all about. And if you really want to help out, let me know if you can be a host, and I’ll schedule you into the calendar.

Finally, if you run a space-related blog, please post a link to the carnival of space. Help us get the word out.

January 10, 2008December 26, 2015 by Fraser Cain

The Building Blocks of the Grand Spirals

We live in a beautiful grand spiral galaxy. But how did we get from the primordial elements after the Big Bang to the intricate and complex structure we live in today? Astronomers have found some of the earliest galactic building blocks; the ancestors of galaxies like our own Milky Way.

The discovery was made by researchers from Rutgers and Penn State universities, and announced at the 211th meeting of the American Astronomical Society in Austin, Texas.

These newly discovered galaxies are tiny, between one-tenth and one-twentieth the mass of the Milky Way. From ground-based telescopes, they just look like individual stars. But the powerful gaze of the Hubble Space Telescope reveals them as regions of active star formation.

The researchers learned that these galaxies are hotbeds of star formation, blazing in a telltale spectrum of ultraviolet radiation that just screams, “I’ve got stellar nurseries”. In many cases, more than 10 of these proto-galaxies came together to form a single spiral galaxy.

“The Hubble Space Telescope delivered striking images of these early galaxies, with 10 times the resolution of ground-based telescopes,” said Caryl Gronwall, a senior research associate in Penn State’s Department of Astronomy & Astrophysics. “They come in a variety of shapes – round, oblong , and even somewhat linear – and we’re starting to make precise measurements of their sizes.”

The galaxies were discovered as part of a five-year census of galaxies in the early Universe. The astronomers searched for these specific kinds of galaxies by detecting the ultraviolet radiation from their bursts of star formation. They then performed follow up observations to find their distance and mass.

Original Source: Rutgers News Release

January 10, 2008December 26, 2015 by Fraser Cain

A Quartet of Stars, Locked in a Tight Embrace

Astronomers think that many star systems actually contain multiple stars. There are doubles, triples and even quadruple groupings of stars locked together in a gravitational embrace. Astronomers recently discovered a system with 4 stars orbiting within the orbit of Jupiter. It’s a surprising discovery considering no telescope on Earth is powerful enough to separate them into distinct points of light.

The star system, located 166 light-years from here, is called BC 22 5866, and its discovery was announced the Winter meeting of the American Astronomical Society in Austin. An international team of astronomers described how they had been monitoring several hundred star systems when they saw something unusual.

They were analyzing the light from one of hundreds of stars when they realized that its light could be broken into 4 separate stars. Even the most powerful telescopes on Earth can’t actually resolve the stars into separate objects, and that means they’re close together… really close.

The stars are paired up together into binary groupings, and then these two pairs orbit a common centre of gravity. One pair orbits each other in less than 5 days – at a distance of a mere 0.06 astronomical units (1 AU is the distance from the Earth to the Sun). The second pair takes 55 days to complete an orbit, at a distance of 0.26 AU.

And finally, the two pairs take about 9 years to orbit one another at a distance of 5.8 AU – within the orbit of Jupiter in our own Solar System.

It must have been a very special system to allow 4 individual stars to form this closely together.

“The extraordinarily tight configuration of this stellar system tells us that there may have been a single gaseous disk that forced them into such small orbits within the first 100,000 years of their evolution, as the stars could not have formed so close to one another. This is the first evidence of a disk completely encompassing four stars,” says Dr. Shkolnik of the University of Hawaii’s Institute for Astronomy. “It is remarkable how much a single stellar spectrum can tell us about both the present and the past of these stars.”

Original Source: IfA News Release

January 10, 2008December 26, 2015 by Fraser Cain

Hubble Sees a Double Einstein Ring

An Einstein Ring happens when two galaxies are perfectly aligned. The closer galaxy acts as a lens, magnifying and distorting the view of a more distant galaxy. But today astronomers announced that they’ve discovered a double Einstein Ring: three galaxies are perfectly aligned, creating a double ring around the lensing galaxy. The odds of finding something like this are pretty low. And yet… here it is.

The double Einstein Ring image was captured by the Hubble Space Telescope, and shows a central galaxy surrounding by an almost complete ring, with another fainter ring around that. Think of a bull’s-eye.

It was found by an international team of astronomers led by Raphael Gavazzi and Tommaso Treu of the University of California, Santa Barbara, and the results were presented at the 211th meeting of the American Astronomical Society in Austin, Texas.

Treu was pretty excited, “the twin rings were clearly visible in the Hubble image. When I first saw it I said ‘wow, this is insane!’ I could not believe it!”

Here’s how it works. As Einstein predicted, gravity has the power to bend light. So instead of traveling on a straight curve, light that passes close to a large mass is pulled into a curved path. When you have a foreground galaxy perfectly lined up with a background galaxy, the light from the more distant galaxy is distorted into a ring of light.

Although the background galaxy is distorted, it’s also tremendously magnified, allowing astronomers to use the foreground galaxy as a natural telescope to peer much more deeply into the Universe than they would be able to see normally.

In the case of this double ring, the foreground galaxy is 3 billion light-years away. The background galaxy that forms the first ring is 6 billion light-years away, and the second background galaxy is 11 billion-light years away. This means that the background galaxy is being seen when the Universe was less than 3 billion years old.

The alignment also allowed astronomers to measure the mass of the middle galaxy to 1 billion solar masses. This is the first time the mass of a dwarf galaxy has been measured at this kind of distance.

Original Source: Hubble News Release

January 10, 2008December 26, 2015 by Fraser Cain

Supercluster Ruled By the Pull of Dark Matter

Enough of this small stuff, let’s look at the big picture. The really really big picture. In this case, one of the largest patches of the sky ever observed by the Hubble Space Telescope. A new detailed survey was released today that combines 80 separate Hubble images together. In addition to a framework of galaxy clusters, the images show the distribution of dark matter that holds the clusters together – and tears it all apart.

The dark matter survey is part of the Space Telescope Abell 901/902 Galaxy Evolution Survey (STAGES), which looks at one of the larger structures in the Universe: the Abell 901/902 superclusters. This is a region of tremendous violence and chaos. Galaxies are being pulled into the core of the superclusters, and getting distorted and stripped of their gas and dust.

And one of the primary forces of this violence comes from the completely invisible dark matter that makes up the bulk of the matter in the region. Instead of being equally distributed, though, this dark matter has pooled into enormous clumps.

An international team of astronomers used Hubble to measure how individual galaxies are distorted by clouds of dark matter. The dark matter is invisible, but it does have mass, which can pull at the light as it moves past. The astronomers know what different galaxies should probably look like, and then can figure out how much dark matter is in between, distorting the view. It’s actually pretty incredible to see the dark matter map imposed over top of the visible light image.

“Thanks to Hubble’s Advanced Camera for Surveys, we are detcting for the first time the irregular clumps of dark matter in this supercluster,” said Catherine Heymans of the University of British Columbia. “We can even see an extension of the dark matter toward a very hot group of galaxies that are emitting X-rays as they fall into the densest cluster core.”

The Hubble study identified 4 separate regions where the dark matter has pooled into dense clumps, adding up to 100 trillion times the mass of the Sun. They can even make out irregular clumps of dark matter in the supercluster. These areas match the locations where hundreds of old galaxies have already experienced the violent passage from the outskirts of the supercluster into the denser regions.

Original Source: Hubble News Release

January 10, 2008December 26, 2015 by Nancy Atkinson

Asteroid 2007 WD5 Won’t Hit Mars

Sorry to disappoint those of you hoping for some Martian fireworks the end of this month. NASA’s Near Earth Object (NEO) Program office has effectively ruled out the possibility of Asteroid 2007 WD5 impacting Mars. The probability of such an event has dropped dramatically, to approximately 0.01% or 1 in 10,000 odds of an impact. Observers also say the asteroid has no possibility of impact with either Mars or Earth anytime in the next century.

Recent tracking measurements of the asteroid from several Earth-based observatories have provided a significant reduction in the uncertainties of the asteroid’s position during its close approach to Mars on Jan. 30, 2008. The best estimates now have 2007 WD5 passing about 26,000 km (16,155 miles) from the planet’s center at approximately 12:00 UTC (4:00 am PST) on Jan. 30th. The NEO office at the Jet Propulsion Laboratory has 99.7% confidence that the pass should be no closer than 4000 km (2,485 miles) from Mars’ surface.

The 50 meter (164 feet) wide asteroid was discovered in late November of 2007 by astronomers at the University of Arizona as part of the Catalina Sky Survey. Other telescopes used to track the asteroid are the Kitt Peak telescope in Arizona, the Sloan Digital Sky Survey telescope in New Mexico, New Mexico Tech’s Magdalena Ridge Observatory, the Multi-Mirror Telescope in Arizona, the Mauna Kea telescope in Hawaii and the Calar Alto Observatory in Spain.

An impact on Mars by 2007 WD5 could have created a .8 km (1/2 mile) wide crater on the planet’s surface. Many scientists were excited by the prospect of such an event, one that could possibly be tracked by the many spacecraft orbiting and on the surface of the red planet.

NASA’s Spaceguard Survey continually searches for Near-Earth Asteroids such as 2007 WD5, and their goal is to discover 90% of those larger than 1 km in size. JPL’s NEO office says that goal should be met within the next few years. Each discovered asteroid is continually monitored for the possibility of impact on Earth.

Original News Source: Near Earth Object Program press release

January 9, 2008December 26, 2015 by Fraser Cain

Researchers Find a Planet, Right Where They Expected

Before Neptune was discovered in the 1840s, astronomers predicted its location based on how it was interacting with Uranus. Once again, this technique was used to find a planet, but this time orbiting a star 200 light-years away. It turns out planets like to be packed together in star systems. Find a gap, and you might have discovered a planet.

Astronomers from the University of Arizona in Tucson announced their findings today at the meeting of the American Astronomical Society in Austin.

Rory Barnes, a post-doctoral associate at UA’s Lunar and Planetary Laboratory, and a team of colleagues studied the orbits of several planetary systems. They found that the planets are generally packed as close together as possible without actually gravitational disrupting each other – if you get them any closer, planets will be kicked inward or outward from the system. This is called the Packed Planetary Systems hypothesis.

“The Packed Planetary Systems hypothesis reveals something fundamental about the formation of planets,” Barnes said. “The process by which planets grow from clouds of dust and gas around young stars must be very efficient. Wherever there is room for a planet to form, it does.”

The researchers studied the orbits of several planetary systems and noticed that there was a big gap between two planets orbiting the star HD 74156. So if their hypothesis was correct, there should be a planet orbiting in between the gap.

“When I realized that six out of seven multi-planet systems appeared packed,” Barnes said, “I naturally expected that there must be another planet in the HD 74156 system so that it, too, would be packed.”

With this prediction in hand, a team of astronomers from the University of Texas made careful observations of the HD 74156 system, looking for the theorized planet.

And guess what… they found it!

With this prediction confirmed, Barnes and his colleagues also predicted that there should be another planet orbiting around 55 Cancri. This was found by a different team of astronomers.

The researchers have predicted a specific planet orbiting a third star, but so far they haven’t found it.

But as more planetary systems are discovered, the Packed Planetary Systems hypothesis will fill in the holes. Astronomers will know where to look for more planets.

Original Source: University of Arizona News Release

January 9, 2008December 26, 2015 by Fraser Cain

Some Stars Can Go through a Second Stage of Planet Formation

Newly forming planetary systems follow a routine. They collapse down from a cloud of gas and dust to form a central star and orbiting planets. But astronomers have found two unusual stars that went through a second phase of planetary formation, hundreds of millions or even billions of years after the first.

The announcement was made by Carl Melis, an astronomy graduate student at UCLA, at the 211th meeting of the American Astronomical Society held in Austin, Texas.

“This is a new class of stars, ones that display conditions now ripe for formation of a second generation of planets, long long after the stars themselves formed,” Melis said.

The two bizarre stars are known as BP Piscium, in the constellation Pisces, and TYCHO 4144 329 2, in the constellation Ursa Major. They have characteristics similar to young stars, such as the rapid accretion of gas, extended disks of material, infrared emissions of radiation, and even jets.

They may act young, but these stars are very old. The astronomers measured the quantities of lithium in the stars; an element which is consumed when stars get older. If they were young, they would still have their reserves of lithium, but they have very little of it left.

So you have older stars behaving like young stars; what happened?

The researchers think that these stars were once part of a binary system where a solar-mass star was matched with a much less massive star. The more massive star ran out of fuel first and ballooned up as a red giant, engulfing the smaller star. At this point, the smaller star would actually be orbiting inside the envelope of the red giant, forcing material out into space, while slowly spiraling inward to meet its destruction.

This ejected material would actually contain the building blocks of terrestrial planets, and so, the planetary formation process would get going all over again. The size of the new planets that could form would depend on how much material was ejected during this red giant phase.

Original Source: UCLA News Release

January 9, 2008December 26, 2015 by Fraser Cain

There’s a Lopsided Halo of Antimatter Surrounding the Centre of the Milky Way

Bring matter and anti-matter together, and you get a potent explosion. Since antimatter is annihilated almost as soon as it forms, you wouldn’t think you could find any out there in the Universe. But you’d be wrong. There’s a giant cloud of the anti-stuff in the central regions of the Milky Way. Oh, and the cloud is lopsided.

An international team of astronomers have gathered together 4 years of observations from ESA’s Integral space observatory. The gamma ray observatory is able to detect the telltale burst of radiation when a particle of antimatter meets its normal matter counterpart. The two particles annihilate each other in a powerful blast of gamma rays.

This burst of radiation is very specific; the gamma rays from a matter/antimatter annihilation carry exactly 511 thousand electron-volts of energy. So the astronomers just used Integral to scan the skies looking for these 511 keV emissions.

So where does all this antimatter come from? Astronomers think that exploding stars could produce it during stellar outbursts. But they’re not sure if this antimatter could actually be released in significant quantities to explain the large cloud near the centre of the galaxy.

Perhaps there’s a more exotic process going on. Other astronomers have theorized that the shape and position of the antimatter cloud matches the expected distribution of dark matter in the centre of the galaxy. Perhaps dark matter is somehow being annihilated or decaying into other particles – including antimatter.

The new results from Integral actually point away from this theory. The antimatter cloud is lopsided, with twice as much material on one side of the galaxy as the other. Astronomers would expect that the antimatter should match the distribution of the dark matter.

There’s one last explanation. Theorists have proposed that a certain kind of binary star system, where an exotic compact object, like a white dwarf, neutron star or black hole, is a gravitational dance with a regular star. The exotic star siphons away material, which piles up on its surface. In this extreme environment, antimatter could be spontaneously generated in the intense radiation field.

Integral found a large population of binary stars located off-centre in the galaxy, corresponding to the distribution of the antimatter. So instead of a cloud of antimatter, there’s just a diffuse glow of gamma rays coming from all these binary star systems.

Original Source: ESA News Release