Tuesday, December 18, 2007
Story of the Day-Jet From Supermassive Black Hole Seen Blasting Neighboring Galaxy
Galaxy blasts neighbor with deadly jet
‘Death star galaxy’ could obliterate the atmospheres of planets
For the first time astronomers have witnessed a supermassive black hole blasting its galactic neighbor with a deadly beam of energy.
The "death star galaxy," as NASA astronomers called it, could obliterate the atmospheres of planets but also trigger the birth of stars in its wake of its destructive beam. Fortunately, the cosmic violence is a safe distance from our own neck of the cosmos.
"We've seen many jets produced by black holes, but this is the first time we've seen one punch into another galaxy like we're seeing here," said Dan Evans, astronomer at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. "This jet could be causing all sorts of problems for the smaller galaxy it is pummeling."
Evans and his colleagues detail their findings in an upcoming issue of the Astrophysical Journal.
The deadly galaxy — the largest of two in a system known as 3C321 — is aiming the high-energy jet from its center at a smaller galaxy 20,000 light-years away from it, or roughly the distance from Earth to the Milky Way's core. The entire system is located about 1.4 billion light-years away from Earth.
A bright spot in a NASA composite image reveals that the beam is striking the edge of the smaller galaxy, deflecting the spindle of energy into intergalactic space. While not a direct hit, astronomers said the consequences are frightening.
"This is a fascinating result, and we can be glad that we're seeing it from a safe distance," said Neil deGrasse Tyson, an astrophysicist at the American Museum of Natural History in New York who did not contribute to the study. "Knowing how lethal the radiation from the jet could be, I wouldn't want to be anywhere near its line of fire."
Jets from supermassive black holes produce tremendous radiation in the form of X-rays, gamma rays and electrons traveling close to the speed of light. Evans said, however, that the X-ray and gamma-ray photons would ultimately do the most damage to planets.
"The photons can have a really dramatic, profound effect on a planetary atmosphere," he said, including vaporizing ozone and other gases. With the protective layers gone, life at the surface would be subject to the jet's full wrath.
The offending galaxy probably began hosing its companion about 1 million years ago, which is relatively recent on a cosmic time scale. Evans said the unusual event makes 3C321 an important object for learning more about the universe.
"We've seen jets do pretty weird things to their environments, but a head-on collision is really rare and generates a [large] amount of information about physics that we can understand and use," Evans said. "For that galaxy to be looking right down ... the barrel of the gun of that jet is incredibly rare, so this makes it a really exciting discovery."
Turns out that the "death ray" may not be all bad news for the victimized galaxy, at least theoretically, as such a massive influx of energy and radiation could help form new stars and solar systems by ripping apart older ones.
To fully view the galactic violence and rebirth, astronomers used NASA's Chandra X-ray observatory, Hubble and Spitzer space telescopes, and the Very Large Array and MERLIN radio telescopes on Earth.
Jet From Supermassive Black Hole Seen Blasting Neighboring Galaxy
A jet of highly charged radiation from a supermassive black hole at the center of a distant galaxy is blasting another galaxy nearby -- an act of galactic violence that astronomers said yesterday they have never seen before.
Using images from the orbiting Chandra X-Ray Observatory and other sources, scientists said the extremely intense jet from the larger galaxy can be seen shooting across 20,000 light-years of space and plowing into the outer gas and dust of the smaller one.
The smaller galaxy is being transformed by the radiation and the jet is being bent before shooting millions of light-years farther in a new direction.
"What we've identified is an act of violence by a black hole, with an unfortunate nearby galaxy in the line of fire," said Dan Evans, the study leader at the Harvard-Smithsonian Center for Astrophysics in Cambridge. He said any planets orbiting the stars of the smaller galaxy would be dramatically affected, and any life forms would likely die as the jet's radiation transformed the planets' atmosphere.
Black holes are generally thought of as mysterious cosmic phenomena that swallow matter, but the supermassive ones that occur at the center of many -- possibly all -- galaxies also set loose tremendous bursts of energy as matter swirls around the disk of material that circles the black hole but does not make it in.
That energy, often in the form of highly charged gamma rays and X-rays, shoots out in powerful jets that can be millions of light-years long and 1,000 light-years wide.
Scientists are just beginning to understand these jets, which not only transform matter in their path but also help produce "stellar nurseries," where new stars are formed.
Evans's collaborator, Martin Hardcastle of the University of Hertfordshire in England, said the collision they have identified began no more than 1 million years ago and could continue for 10 million to 100 million more years. Hardcastle called the collision a great opportunity to learn more about the jets.
"We see jets all over the universe, but we're still struggling to understand some of their basic properties," he said. "This system . . . gives us a chance to learn how they're affected when they slam into something -- like a galaxy -- and what they do after that."
The two galaxies are more than 1.4 billion light-years away from the Milky Way galaxy (a light-year equals about 6 trillion miles). But they are close to each other in cosmic terms -- about as far as the distance from Earth to the center of the Milky Way. That the two appear to be moving toward a merger may have played a role in creating such a powerful jet from the larger galaxy's central black hole.
The researchers said that the collision would have no effect on Earth, but the process is one that could play out in our galaxy a billion years into the future.
The galaxy Andromeda is the closest to the Milky Way, and the two are gradually coming closer to each other. In time, astronomers say, the two will merge, and the process may cause the dormant central black holes in either the Milky Way or Andromeda to become active and begin sending out similarly powerful jets.
If a jet were to hit Earth, Evans said, it would destroy the ozone layer and collapse the magnetosphere that blankets the planet and protects it from harmful solar particles. Without the ozone layer and magnetosphere, he said, much of life on Earth would end.
"This jet could be causing all sorts of problems for the smaller galaxy it is pummeling," Evans said.
Neil deGrasse Tyson, an astrophysicist from the American Museum of Natural History in New York, said the discovery illustrates how researchers can now observe astronomical phenomena using many different tools and understand how they behave at many different points along the electromagnetic spectrum. Only when scientists measure a galaxy at all different wavelengths, he said, "can you really understand what's going on."
In making their discovery, the researchers used data from three orbiting instruments -- the Chandra X-ray Observatory, the Hubble Space Telescope and Spitzer Space Telescope -- as well as ground-based observatories including the Very Large Array telescope in New Mexico and Britain's Multi-Element Radio Linked Interferometer Network. The Astrophysical Journal will publish the results next year.