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Quasars & Active Galaxies
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Quasars & Active Galaxies
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Quasars & Active Galaxies
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Quasars & Active Galaxies
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1. Tour of NGC 5128
QuicktimeMPEG Astronomers have found a pair of extraordinary objects that dramatically burst in X-rays. This discovery, made using data from NASA's Chandra X-ray Observatory and ESA's XMM-Newton observatory, may represent a new class of explosive events.

The mysterious sources flare up and become about a hundred times brighter in X-rays in less than a minute, before returning to the original X-ray levels after about an hour. One of the sources, located near and presumably associated with the galaxy NGC 4636 at a distance of 47 million light years, was observed to flare once. Five flares were detected from the other source, which is located near the galaxy NGC 5128 at a distance of 12 million light years.

What could these objects be? Probably not magnetars, which are young neutron stars with powerful magnetic fields. Magnetars are also known to have giant X-ray flares, but they are different from these newly discovered objects in a few different ways including how long they flare and where they are found.

While the nature of these flares is unknown, researchers have begun to search for answers. One idea is that the flares represent episodes when matter being pulled away from a companion star falls rapidly onto a black hole or neutron star. This could happen when the companion makes its closest approach to the compact object in an eccentric orbit. Another explanation could involve matter falling onto an intermediate-mass black hole, with a mass of about 800 times that of the Sun for one source and 80 times that of the Sun for the other.

These new flaring objects will likely keep both observational and theoretical astrophysicists busy for quite some time. Using telescopes like Chandra and XMM-Newton, they undoubtedly hope to come up with more answers soon.
[Runtime: 03:04]
(NASA/CXC/UA/J.Irwin et al.)

Related Chandra Images:

Click for high-resolution animation
2. Tour of IC 2497
QuicktimeMPEG Citizen science projects have done some remarkable things in recent years and those in astronomy are no exception. One of the early success stories of the Galaxy Zoo citizen science project was the discovery of an unusual object in 2007. This object was found by Hanny van Arkel who, at the time, was a school teacher in the Netherlands. Today, the object is known as "Hanny's Voorwerp," which means "Hanny's object" in Dutch.

Professional astronomers have also taken an interest in Hanny's Voorwerp. This unusually-shaped cloud of gas, which also has another nickname of the "green blob," is located only about 200,000 light years from the galaxy IC 2497. While this sounds like a huge distance, it is actually very close in cosmic terms. Because of that, Hanny's Voorwerp is affected by what goes on in IC 2497, in particular by the behavior of the giant black hole at its center. In fact, the green blob gets its color because oxygen atoms in the gas cloud have been excited by the incoming ultraviolet and X-ray radiation from regions close to the black hole.

Even though astronomers suspect this black hole was a so-called quasar in the past, recent Chandra observations indicate that it has since faded. So far, Hanny's Voorwerp shows no sign of dimming, but with the 200,000 light year separation, astronomers in the upcoming millennia might just see the lights in the green blob start to flicker off.

New observations with Chandra suggest that the black hole is still producing large amounts of energy even though it is no longer generating intense radiation as a quasar. The X-ray data suggest that jets powered by the black hole have blown a large bubble in surrounding gas. This shows that giant black holes can have a big effect on their environments.
[Runtime: 3.00]
(NASA/CXC/A. Hobart)

Related Chandra Images:

Click for high-resolution animation
3. Tour of IC 2497
QuicktimeMPEG Citizen science projects have done some remarkable things in recent years and those in astronomy are no exception. One of the early success stories of the Galaxy Zoo citizen science project was the discovery of an unusual object in 2007. This object was found by Hanny van Arkel who, at the time, was a school teacher in the Netherlands. Today, the object is known as "Hanny's Voorwerp," which means "Hanny's object" in Dutch.

Professional astronomers have also taken an interest in Hanny's Voorwerp. This unusually-shaped cloud of gas, which also has another nickname of the "green blob," is located only about 200,000 light years from the galaxy IC 2497. While this sounds like a huge distance, it is actually very close in cosmic terms. Because of that, Hanny's Voorwerp is affected by what goes on in IC 2497, in particular by the behavior of the giant black hole at its center. In fact, the green blob gets its color because oxygen atoms in the gas cloud have been excited by the incoming ultraviolet and X-ray radiation from regions close to the black hole.

Even though astronomers suspect this black hole was a so-called quasar in the past, recent Chandra observations indicate that it has since faded. So far, Hanny's Voorwerp shows no sign of dimming, but with the 200,000 light year separation, astronomers in the upcoming millennia might just see the lights in the green blob start to flicker off.

New observations with Chandra suggest that the black hole is still producing large amounts of energy even though it is no longer generating intense radiation as a quasar. The X-ray data suggest that jets powered by the black hole have blown a large bubble in surrounding gas. This shows that giant black holes can have a big effect on their environments.
[Runtime: 3.00]
(NASA/CXC/A. Hobart)

Related Chandra Images:

Click for high-resolution animation
4. Tour of B3 0727+409
QuicktimeMPEG Astronomers have used NASA's Chandra X-ray Observatory to discover a jet from a very distant supermassive black hole being illuminated by the oldest light in the Universe. This discovery shows that black holes with powerful jets may be more common than previously thought in the first few billion years after the Big Bang.

The light detected from this jet, found in the system known as B3 0727+409, was emitted when the Universe was only 2.7 billion years old, or a fifth of its present age. At this point, the intensity of the cosmic microwave background radiation, the glow left over from the Big Bang, was much greater than it is today.

The significance of the discovery of an X-ray jet in B3 0727+409 is heightened because astronomers essentially stumbled across this jet while observing a galaxy cluster in the field. Historically, such distant jets have been discovered in radio waves first, and then followed up with X-ray observations to look for high-energy emission. If bright X-ray jets can exist with very faint or undetected radio counterparts, it means that there could be many more of them out there because astronomers haven't been systematically looking for them.

Jets in the early Universe such as B3 0727+409 give astronomers a way to probe the growth of black holes at a very early epoch in the cosmos.
[Runtime: 02:25]
(NASA/CXC/A. Hobart)

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5. A Tour of Pictor A
QuicktimeMPEG The Star Wars franchise has featured the fictitious "Death Star," which can shoot powerful beams of radiation across space. The Universe, however, produces phenomena that often surpass what science fiction can conjure.

The Pictor A galaxy is one such impressive object. This galaxy, located nearly 500 million light years from Earth, contains a supermassive black hole at its center. Material falling onto the black hole is driving an enormous beam, or jet, of particles at nearly the speed of light into intergalactic space. Even though it is hundreds of thousands of light years away, the jet in Pictor A is actually the closest one to Earth that displays continuous X-ray emission over a distance of 300,000 light years.

Scientists used NASA's Chandra X-ray Observatory at various times over 15 years to obtain data on this impressive system. They combined these X-ray data from Chandra with radio waves from the Australia Telescope Compact Array to try to gain a deeper understanding of these huge collimated blasts.

The researchers determined that the X-ray emission in the Pictor A jet likely comes from electrons spiraling around magnetic field lines -- a process called synchrotron emission. In this case, the electrons must be continuously re-accelerated as they move out along the jet. While they think that's probably what's going on, astronomers do not know exactly how this process happens. Yet another ongoing mystery in a galaxy far, far away.
[Runtime: 02:34]
(NASA/CXC/A. Hobart)

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6. A Tour of RGG 118
QuicktimeMPEG Oxymorons are often thought of as gaffes in language, but a new black hole discovery shows they can also represent important scientific advances. Astronomers using NASA's Chandra X-ray Observatory and the 6.5-meter Clay Telescope in Chile have identified the smallest giant black hole known. This oxymoronic object could provide clues to how much larger black holes formed along with their host galaxies billion of years in the past.

Astronomers estimate this supermassive black hole is about 50,000 times the mass of the Sun. This is less than half the previous lowest mass for a black hole at the center of a galaxy. The tiny heavyweight black hole is located at the center of a dwarf disk galaxy, called RGG 118, about 340 million light years from Earth.

Researchers estimated the mass of the black hole by studying the motion of cool gas near the center of the galaxy using visible light data from the Clay Telescope. They used the Chandra data to figure out the brightness in X-rays of hot gas swirling toward the black hole. They found that the outward push of radiation pressure of this hot gas is about 1% of the black hole's inward pull of gravity. This matches the properties of other supermassive black holes.

The black hole in RGG 118 is nearly 100 times less massive than the supermassive black hole found in the center of the Milky Way. It is also about 200,000 times less massive than the heaviest black holes found in the centers of other galaxies.

Researchers will keep looking for other supermassive black holes that are comparable in size or even smaller than the one in RGG 118. It is important to gather a large sample because black holes of this size might be seeds that lead to the formation of much larger supermassive black holes.
[Runtime: 02:10]
(NASA/CXC/A. Hobart)

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7. Tour of Space-time Foam
QuicktimeMPEG At the smallest scales of distance and duration that we can measure, space-time - that is, the three dimensions of space plus time - appears to be smooth and structureless. Think of flying over the ocean in an airplane. From 30,000 feet or so, the ocean appears completely smooth. However, if your plane were to descend low enough, you could make out the waves and swells of the water. Certain aspects of quantum mechanics, the highly successful theory scientists have developed to explain the physics of atoms and subatomic particles, predict that space-time may act the same way. Instead of being totally smooth, it would have a foamy, jittery nature if we could look at small enough scales -- like those waves on the ocean. In these models, space-time would consist of many small, ever-changing, regions for which space and time are constantly fluctuating.

Since space-time foam, as it is called, is so tiny, scientists cannot observe it directly. However, they can hunt for evidence for its existence - or non-existence - in things we can see. By looking at the light from distant quasars in X-rays from Chandra as well as gamma-ray telescopes, a team of scientists set out to test some of the models of space-time foam.

What did they find? The researchers say their evidence can help rule out two different models of space-time foam. While their work does not eliminate the existence of space-time foam entirely, it does suggest that space-time is less foamy than some models predict. Scientists will continue to test the nature of space and time on the very smallest scales using every experiment they can think of, including using high-energy light from across the Universe.
[Runtime: 02:02]
(NASA/CXC/A. Hobart)

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8. Tour of 3 Quasars
QuicktimeMPEG A group of unusual giant black holes may be consuming excessive amounts of matter, according to a new study using NASA's Chandra X-ray Observatory. This finding may help astronomers understand how the largest black holes were able to grow so rapidly in the early Universe.

Astronomers have known for some time that supermassive black holes - with masses ranging from millions to billions of times the mass of the Sun and residing at the centers of galaxies - can gobble up huge quantities of gas and dust that have fallen into their gravitational pull. As the matter falls towards these black holes, it glows with such brilliance that they can be seen billions of light years away. Astronomers call these extremely ravenous black holes "quasars."

This new result suggests that some quasars are even more adept at devouring material than previously thought, about five to ten times the rate of typical quasars. A team of astronomers examined data from Chandra for 51 quasars that are located at a distance between about 5 billion and 11.5 billion light years from Earth. Based on their findings, the researchers think some of these quasars contain black holes that are surrounded by a thick, donut-shaped disk of material. This torus would block much of the light - including X-rays and ultraviolet light -- that would otherwise be observed by Chandra and other telescopes. The important implication for these thick-disk quasars is that they may be harboring black holes that are growing an extraordinarily rapid rate.
[Runtime: 01:53]
(NASA/CXC/A. Hobart)

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9. The Most Attractive Stars in the Universe
QuicktimeMPEG Have you ever played with magnets? You might have done an experiment where you lay a magnet onto a table and place an iron nail nearby. If you push the magnet slowly toward the nail, there will come a point when the nail jumps across and sticks to the magnet. That's because magnets have something invisible that extends all around them, called a 'magnetic field'. It can cause a pushing or pulling force on other objects, even if the magnet isn't actually touching them.

The most powerful magnets in the Universe are called magnetars. These are tiny, super-compact stars, 50 times more massive than our Sun, squashed into a ball just 20 kilometers across. (That's about the size of a small city!)

Astronomers think magnetars may be created when some massive stars die in a supernova explosion. The star's gases blow out into space creating a colourful cloud like the one in this picture, called Kes 73. At the same time, the core of the star squashes down to form a magnetar.

At the center of the cosmic cloud in this photograph lies a tiny magnetar. But what this star lacks in size it makes up for in energy, shooting out powerful jets of X-rays every few seconds! You can see the X-ray jets in blue in this photograph.
[Runtime: 02:04]
(NASA/CXC/April Jubett)

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10. A Tour of IYL 2015
QuicktimeMPEG The year of 2015 has been declared the International Year of Light, or IYL for short, by the United Nations. Organizations, institutions, and individuals involved in the science and applications of light will be joining together for this year-long celebration to help spread the word about the wonders of light.

In many ways, astronomy uses the science of light. By building telescopes that can detect light in its many forms from radio waves on one end of the "electromagnetic spectrum" to gamma rays on the other, scientists can get a better understanding of the processes at work in the Universe.

NASA's Chandra X-ray Observatory explores the Universe in X-rays, a high-energy form of light. By studying X-ray data and comparing them with observations in other types of light, scientists can develop a better understanding of objects that generate temperatures of millions of degrees and produce X-rays.

To recognize the start of IYL, the Chandra X-ray Center is releasing a collection of images that combine data from telescopes tuned to different wavelengths of light. From a distant galaxy to the relatively nearby debris field of an exploded star, these images demonstrate the myriad ways that information about the Universe is communicated to us through light.

So join us in celebrating IYL and all of the amazing things that light can do, including how it helps us understand the Universe we live in.
[Runtime: 01:58]
(NASA/CXC/A. Hobart)

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