Ejected Black Holes May Take Their Fuel With Them

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The huge majestic spiral galaxy we live in today was built up over billions of years through mergers with other galaxies. And in 5-10 billion years from now, we’ll merge together with the Andromeda Galaxy. Since both galaxies are thought to have a supermassive black hole at their centre, what will happen when they merge together? One possibility is that one black hole will get ejected from the combining galactic core at a tremendous velocity.

Astronomers have suspected this kind of interaction might happen. The velocities and gravitational forces are so great during a black hole merger, that one of the objects could be flung out like a slingshot. It was believed that the black hole would be stripped of its accretion disk as it’s flung out into the galaxy, so it would be impossible to detect.

But new calculations by Avi Loeb, a researcher with the Harvard-Smithsonian Center for Astrophysics, indicate that an ejected black hole might be able to bring its accretion disk along for the ride. And the radiation pouring out of this disk might be detectable here on Earth.

If the calculations are correct, the two merging black holes will be releasing torrents of gravitational radiation in the direction they’re orbiting. The momentum from this radiation will give one black hole a kick in the opposite direction, ejecting it at 16 million km/hour (10 million mph). At this speed, a black hole would traverse its galaxy in just 10 million years.

According to Loeb, as long as the gas within the disk was orbiting at a speed far great than the black hole ejection speed, it would follow the black hole on its journey. It could last a few million years, consuming this disk of material, and blazing brightly enough that powerful telescopes could detect it. The host galaxy would seem to have a double quasar.

Original Source: CfA News Release

Longer Lasting Gamma Ray Bursts

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When a gamma ray burst detonates, it releases more energy in just a few minutes than our Sun does in its entire lifetime. For a brief time, a gamma ray burst outshines its entire host galaxy. And now NASA’s Swift satellite has found evidence that some bursts can remain active for minutes, or even hours.

Gamma ray bursts are now believed to be a special kind of supernova, where the core of a massive star collapses into a black hole or neutron star. Inrushing gas forms a disk around the central core, and magnetic fields channel material into twin jets emanating from the black hole at nearly light speed.

Early observations by NASA’s Swift satellite found that gamma ray bursts are often followed minutes or hours later by short-lived X-ray flares. These flares suggested that the object that created the gamma ray burst is still active, after that initial flash. Instead of consuming all the material in a single burst of energy, there seem to be ongoing waves of material falling into the black hole. With each wave of consumption, the black hole gives off a torrent of X-ray radiation until everything is gone.

Original Source: NASA News Release

Saturn’s Rings Could Be Twice as Massive as Previously Believed

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New observations from NASA’s Cassini spacecraft have revealed that Saturn’s largest ring isn’t a smooth distribution of particles like it looks in photographs. Instead, it’s actually made up of tightly packed clumps of material surrounded by empty spaces.

According to researchers, these clumps of material are constantly colliding, breaking up, and reforming. And these clumps have hidden the mass of Saturn’s rings. Scientists originally estimated the mass of Saturn’s rings, assuming that particles were evenly distributed. But taking these clumps into account, the rings could be two or more times previous estimates.

To make the calculation, astronomers measured the brightness of a stars as they passed behind the rings. This allowed Cassini to measure the amount of material obscuring the stars, and so scientists could determine the thickness of the rings. Instead of fading gradually, the stars flickered in brightness as they passed behind these clumps.

These observations confirm that theory that the particles in Saturn’s rings gravitationally attract one another, bunching up into “self-gravity wakes”. If they were further from Saturn, the clumps would eventually form moons. But Saturn’s gravity tears them apart, halting their growth when they get larger than 30 to 50 meters (about 100 to 160 feet) across.

Original source: NASA/JPL/University of Colorado News Release

Brown Dwarf Discovered with Jets

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Jets of material have been seen blasting out of quasars, young stars, black holes and other massive objects. But now astronomers have discovered that even a lowly brown dwarf can have jets of outflowing material.

The discovery was made using the European Southern Observatory’s Very Large Telescope, which observed the brown dwarf 2MASS1207-3932. It was already a very interesting object because it has a 5 Jupiter mass planetary companion, and it’s surrounded by a planetary disc, like a young star. And like many young stars, it’s spewing jets of material from its poles.

The brown dwarf only has about 24 times the mass of Jupiter, so it’s not large enough to ignite solar fusion. But even so, it has these twin jets of outflow, stretching out a billion kilometres into space.

With an object this small having jets, astronomers think that young giant planets could also have outflows.

Original Source: ESO News Release

Astrosphere for May 23, 2007

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Once again, it’s time to see what’s happening on other space-related blogs.

Ever wonder what goes into making up a meal for astronauts? Here’s a link to a cool video called “Food in Space”.

I know you enjoy Astronomy Cast, but did you know there are dozens of space-related podcasts now? There’s a great tool called the Astronomy Media Player, which lists them all, and lets you play recent episodes.

Colony Worlds has an interesting analysis of Ceres as a future target for human exploration.

Want to find your planets? Softpedia has an article pointing the way to finding 4 of them with the unaided eye this week.

Centauri Dreams discusses an interesting way to sail through space, propelled by a magnetic field.

Our Lonely Future, 3 Trillion Years From Now

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When astronomers look into the night sky, they see back into time. The light from the most distant galaxies has taken billions of years to reach us. Astronomers can measure that these galaxies are hurtling away from us, as part of the Universe’s expansion after the Big Bang. The more distant a galaxy is, the more quickly it’s moving away from us.

We know that the Universe started from a single point billions of years ago, we know that it’s expanding, and thanks to the mysterious dark energy, we know that this expansion is accelerating. In billions of years, distant galaxies will be speeding away from the Milky Way so quickly that they will recede from us faster than the speed of light. Their light will dim and fade away, and disappear from our view of the cosmos, forever inaccessible and unknowable.

And three trillion years from now, all the galaxies will have passed over the horizon, and faded from view. Future cosmologists will know of only one galaxy: ours. The Universe will appear static and unchanging, slowly cooling away. And this view will be the same from all points of view in the Universe. Physicists in every galaxy will only know of their own home, and nothing else.

This bleak view of our lonely future is all thanks to some new calculations from Lawrence Krauss from Case Western Reserve University and Robert J. Scherrer from Vanderbilt University. Their new article, called the “The Return of the Static Universe and the End of Cosmology,” was recently award a prize by the Gravity Research Foundation, and will be published in the October issue of the Journal of Relativity and Gravitation.

“While physicists of the future will be able to infer that their island universe has not been eternal, it is unlikely they will be able to infer that the beginning involved a Big Bang,” report the researchers.

Another powerful tool that astronomers use to know the Universe is the cosmic microwave background radiation; the afterglow from the Big Bang. The light from these early moments of our Universe has already been red shifted to longer and longer wavelengths with the expansion of the Universe. What used to be visible light is now microwave radiation, and will move through the radio spectrum. Eventually the wavelengths will be so large that astronomers will have no way to detect it.

Researchers also measure the quantities of hydrogen, helium and deuterium across the Universe. Their quantities match predictions for what should have occurred in the Big Bang. For a period, the entire Universe was like a giant star, converting primordial gas into heavier elements. Rapid expansion ended this period, and future elements were formed only within stars. Although the quantities of these elements match predictions today, our future galaxy will have dispersed them and combined them so thoroughly that they’ll be indiscernible as the helium produced in stars will dominate.

“Eventually, the universe will appear static,” said Krauss. “All evidence of modern cosmology will have disappeared.”

We can only hope that research done by cosmologists today is preserved, so future physicists can know that the true nature of the Universe, and not the static place they see around them.

Evidence of Catastrophic Floods on Mars

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This amazing image was captured by ESA’s Mars Express spacecraft, and shows the Deuteronilus Mensae on Mars, a region shaped by glaciers millions of years ago.

The large depression in the middle of the image is approximately 2 km (1.2 miles) deep, and measures 110 km (68 miles) across. Many deep valleys cut by intense flooding feed into the region. It’s believed that these valleys were caused by intense flooding from melted water ice. This water froze quickly, turning into glaciers that flowed downhill.

Although it’s cold and dead now, Mars was once geologically active. It’s believed that rising magma, or impact events could melt vast regions of ice, resulting in major flooding events.

Original Source: ESA News Release

Chandra’s Look at the Andromeda Galaxy

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NASA’s Chandra X-Ray Observatory took this image of the Andromeda Galaxy (aka M31), the closest major galaxy to the Milky Way. The wider-field image is in optical, and then the zoomed in region is a composite X-ray and optical light image. The purpose of the research was to find X-ray regions and point sources in M31’s central core.

The diffuse blue glow around the centre of the galaxy comes from hot, bright gas. The bright point sources are mostly binary stars interacting with one another. In some situations, a white dwarf is gathering material from a companion star. When too much gas piles up, an explosion occurs on the surface of the white dwarf, which astronomers see as a flash of X-rays called a nova.

By studying these novae for a long period of time, using multiple X-ray observatories, astronomers discovered that many of these novae last for a surprisingly short amount of time. This means that many novae were probably missed during previous observations.

One theory is that the shorter novae occur on the white dwarfs that are the highest mass, and could be ready to explode as type 1a supernovae.

Original Source: Chandra News Release

Spirit Scrapes Up Evidence of Mars’ Wet Past

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Although they’re not so much in the news these days, the Martian rovers, Spirit and Opportunity are still hard at work on their primary mission: discovering evidence of past water on Mars. A new patch of soil uncovered by Spirit is so rich in silica, that scientists think that water must have helped concentrate it eons ago.

While it was exploring a region of hills inside Gusev crater, Spirit uncovered a patch of soil that was clearly different from the surrounding environment. Further examination by the rover’s alpha particle X-ray spectrometer calculated that it was more than 90% pure silica.

This concentration of silica would have required some process involving water. One theory is that the soil might have interacted with acid vapours produced by volcanic activity in the presence of water. Another possibility is that the region might have had many hot springs.

Scientists are celebrating the discovery as one of the most conclusive pieces of evidence for past water that the rovers have turned up so far.

Original Source: NASA/JPL News Release

Podcast: Gravitational Lensing

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Astronomers are always trying to get their hands on bigger and more powerful telescopes. But the most powerful telescopes in the Universe are completely natural, and the size of a galaxy cluster. When you use the gravity of a galaxy as a lens, you can peer right back to the edges of the observable Universe.

Click here to download the episode

Gravitational Lensing – Show notes and transcript

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