Sagittarius A*
Credit: X-ray: NASA/CXC/UCLA/Z.Li et al; Radio: NRAO/VLA
New evidence has been uncovered for the presence of a jet of high-energy particles blasting out of the Milky Way's supermassive black hole. As outlined in the press release, astronomers have made the best case yet that such a jet exists by combining X-ray data from NASA's Chandra X-ray Observatory with radio emission from the NSF's Very Large Array (VLA).
This composite image features both X-rays from Chandra (purple) and
radio data from the VLA (blue). A labeled version of this image - seen
by mousing over the image - reveals the position of Sagittarius A* (Sgr A* for short) and the suspected jet.
The location of a shock front is also marked. As the jet fires away
from Sgr A*, it travels through space until it hits gas several light years
away. (The region around the Milky Way's black hole has many clumps
of gas and dust.) Once the jet hits, it triggers the formation of a
shock front. This interaction also accelerates electrons, generating X-rays as the electrons stream down the path of the jet, past the shock front.
The shock front is also of interest because it is unusually wide in
the radio emission compared to the more narrow profile of the jet in
X-rays. This suggests that there may be a secondary, weaker outflow,
which might be like a sheath or cocoon surrounding the jet with an
opening angle of around 25 degrees.
Sgr A* is about 4 million times the mass of the Sun and lies about 26,000 light years from Earth in the center of the Galaxy. Astronomers have been looking for a jet from Sgr A* for years
since it is now common to find jets tied to a range of cosmic objects
on both big and small scales. Prior to this latest study, there have
been reports of possible evidence of a jet associated with Sgr A*.
However, these have contradicted one another and have thus not been
considered definitive.
A paper describing these results is available online and will appear in an upcoming issue of The Astrophysical Journal.
Fast Facts for Sagittarius A*:
Scale: Image is 1.2 arcmin across (about 9 light years)
Category: Black Holes, Milky Way Galaxy
Coordinates (J2000): RA 17h 45m 40s | Dec -29° 00' 28.00"
Constellation: Sagittarius
Observation Date: 54 pointings between Sep 1999 and Mar 2011
Observation Time: 477 hours 21 min (19 days 21 hours 21 min)
Obs. ID: 242, 945, 1561, 2273, 2276, 2282, 2284, 2943, 2951-2954, 3392, 3393, 3549, 3663, 3665, 4500, 4683, 4684, 5360, 5950-5954, 6113, 6363, 6639-6646, 7048, 7554-7559, 9169-9174, 10556, 11843, 12949, 13438, 13508
I
Instrument: ACIS
Also Known As: Galactic Center
References: Li, Z. et al, 2013, ApJ (accepted); arXiv:1310.0146
Color Code: X-ray (Pink); Radio (Blue)
Radio Distance Estimate: About 26,000 light years
