Can run anytime A new ultraviolet image produced by the European Space Agency's XMM-Newton orbiting telescope has given researchers a more detailed look at the strangely active center of a relatively nearby galaxy.
The galaxy, M81, is roughly 22,000 light-years across and just 12 million light-years away. Scientists said the new image, which combines three 1,000-second shots, is 10 times more detailed than previous UV images of the galaxy.
At the center is a very bright nucleus. Researchers say the emissions from the region might represent a maturing black hole or, instead, could be the result of intense star formation and explosion, which would result in a phenomenon called a starburst.
"Starbursts are regions of intense and violent stellar activity where massive stars are being born and quickly go
supernova," explains Alice Breeveld of the Mullard Space Science Laboratory (MSSL) at University College in London. Breeveld led the team that produced the new image. In more distant parts of the universe, where researchers can observe galaxies when they were younger, strange objects called
quasars are common. These quasars are thought to be galaxies that harbor young black holes that consume matter voraciously, causing a chaos of emissions that astronomers can study. "Quasars are the brightest and most distant known objects producing radiation covering the full range of the electromagnetic spectrum," Breeveld said.
The center of M81 has puzzled astronomers, who have debated whether the emissions are associated with a quasar's black hole or a starburst region.
"Some believe that [galaxies like M81] harbor a mini-quasar, where a supermassive black hole is accreting gas and stars at a very slow rate," Breeveld said. A natural explanation for M81 is that it is a transition phase from being a quasar to being an ordinary galaxy, Breeveld said.
Our own
Milky Way harbors a supermassive black hole that is strangely quiet.About the image
The picture of M81, produced in April and released June 19, is expected to help researchers figure out what causes the central emissions. The image reveals several bright regions of stellar activity throughout the galaxy, shown in blue.
"The UV images pick out intense regions of star formation," said Breeveld. "The shortest wavelength filters isolate the hottest and the most intense regions, so these look blue in the image."
The coolest regions are shown in red. These are concentrated in the central bulge of the galaxy, where most stars are older and less massive and have reached the ends of their lives.
The predominantly red-colored and brightest point-like objects in the image are foreground stars in our own Galaxy.
About the galaxy
The spiral galaxy M81 (also called NGC 3031) lies in the constellation Ursa Major. It is one of the most luminous galaxies in the Northern Hemisphere. It can easily be observed with small amateur telescopes and has even been seen with the naked eye by a handful of people.
M81 also has an interesting neighbor,
M82 (not seen in the new image). The two galaxies probably had a close encounter a few ten million years ago, astronomers say. The collision left the spiral pattern of M81 more pronounced.
"We believe that a collision with the nearby galaxy M82 could have led to the formation of the spiral arm structure," Breeveld said. "The high densities and pressures involved would have triggered the star formation."
The center of the two galaxies are still relatively close, separated by about 150,000 light-years.
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