M51
Credit X-ray: NASA/CXC/Wesleyan Univ./R.Kilgard, et al;
Optical: NASA/STScI
-
Nearly a million seconds of observing time with NASA's Chandra X-ray Observatory has revealed a spiral galaxy similar to the Milky Way glittering with hundreds of X-ray points of light.
The galaxy is officially named Messier 51 (M51) or NGC 5194, but
often goes by its nickname of the "Whirlpool Galaxy." Like the Milky
Way, the Whirlpool is a spiral galaxy with spectacular arms of stars and
dust. M51 is located about 30 million light years from Earth, and its face-on orientation to Earth gives us a perspective that we can never get of our own spiral galactic home.
By using Chandra, astronomers can peer into the Whirlpool to uncover
things that can only be detected in X-rays. In this new composite
image, Chandra data are shown in purple. Optical data from the Hubble
Space Telescope are red, green, and blue.
Most of the X-ray sources are X-ray binaries (XRBs). These systems consist of pairs of objects where a compact star, either a neutron star or, more rarely, a black hole,
is capturing material from an orbiting companion star. The infalling
material is accelerated by the intense gravitational field of the
compact star and heated to millions of degrees, producing a luminous
X-ray source. The Chandra observations reveal that at least ten of the
XRBs in M51 are bright enough to contain black holes.
In eight of these systems the black holes are likely capturing material
from companion stars that are much more massive than the Sun.
Because astronomers have been observing M51 for about a decade with
Chandra, they have critical information about how X-ray sources
containing black holes behave over time. The black holes with massive
stellar companions are consistently bright over the ten years of Chandra
observations. These results suggest that the high-mass stars in these
X-ray sources also have strong winds that allow for a steady stream of material to flow onto the black hole.
A difference between the Milky Way and the Whirlpool galaxy is that
M51 is in the midst of merging with a smaller companion galaxy seen in
the upper left of the image. Scientists think this galactic interaction
is triggering waves of star formation. The most massive of the newly
formed stars will race through their evolution
in a few million years and collapse to form neutron stars or black
holes. Most of the XRBs containing black holes in M51 are located close
to regions where stars are forming, showing their connection to the
oncoming galactic collision.
Previous studies of the Whirlpool Galaxy with Chandra revealed just
over 100 X-ray sources. The new dataset, equivalent to about 900,000
seconds of Chandra observing time, reveals nearly 500 X-ray sources.
About 400 of these sources are thought to be within M51, with the
remaining either being in front of or behind the galaxy itself.
Much of the diffuse, or fuzzy, X-ray emission in M51 comes from gas that has been superheated by supernova explosions of massive stars.
The new Chandra observations were presented at the 224th meeting of
the American Astronomical Society in Boston, Mass. by Roy Kilgard of
Wesleyan University in Middletown, Conn. NASA's Marshall Space Flight
Center in Huntsville, Ala., manages the Chandra program for NASA's
Science Mission Directorate in Washington. The Smithsonian Astrophysical
Observatory in Cambridge, Mass., controls Chandra's science and flight
operations.
Fast Facts for Whirlpool Galaxy:
Scale: Image is about 6 x 10 arcmin (About 52,000 x 87,000 light years)
Category: Normal Galaxies & Starburst Galaxies
Coordinates (J2000): RA 13h 29m 55.7s | Dec +47° 13' 53"
Constellation: Canes Venatici
Observation Date: 11 pointings between Mar 2000 and Oct 2012
Observation Time: 232 hours 10 min (9 days 16 hours 10 min).
Obs. ID: 353,354,1622,3932,13812-13816,15496,15553
Instrument: ACIS
Also Known As: NGC 5194, NGC 5195
References: Kilgard, R. et al, AAS 224, 1-5 June 2014
Color Code: X-ray (Purple); Optical (Red, Green, Blue)
Distance Estimate: About 30 million light years
Source: NASA’s Chandra X-ray Observatory
