NGC 6266:
X-Ray Binaries In Globular Clusters
Credit: NASA/CXC/MIT/D.Pooley et al.
Chandra's unique ability to precisely locate and resolve individual X-ray sources in 12 globular clusters in our Galaxy has given astronomers a crucial clue as to the origin of these sources. Two clusters, known as NGC 6266 (or M62) and NGC 7099 (or M30), are shown here.
A globular cluster is a spherical collection of hundreds of thousands and even millions of stars buzzing around each other in a gravitationally bound stellar beehive that is about a hundred light years in diameter. The stars in a globular cluster are often only about a tenth of a light year apart. For comparison, the nearest star to the Sun, Proxima Centauri, is 4.2 light years away.
Most of the point-like sources in these images are binary star systems containing a collapsed star, such as a neutron star or a white dwarf star, that is pulling matter off a normal companion star. While direct, head-on collisions between stars are rare even in these crowded circumstances, close encounters occur and can lead to the formation of binary star systems containing a collapsed star.
The images illustrate a general trend observed for globular clusters. Clusters such as M62 where the stars are packed very closely together and the rate of close encounters is high have more X-ray binaries than those such as M30 in which close encounters occur less often. This is strong evidence that the X-ray binaries in globular clusters are formed by close encounters.
Fast Facts for
NGC 6266:
|
Credit
|
NASA/CXC/MIT/D.Pooley et al.
|
Scale
|
Image is approx. 1.9 arcmin on a side.
|
Category
|
Normal Stars & Star Clusters, Neutron Stars/X-ray Binaries
|
Coordinates
(J2000)
|
RA17h 01m 12.60s | Dec -30° 06' 44.50"
|
Constellation
|
Scorpius |
Observation
Date
|
May 12, 2002
|
Observation
Time
|
18 hours
|
Obs.
ID
|
2677
|
Also Known As | M62, | References | D. Pooley et al. 2003, Dynamical Formation of Close Binary Systems in Globular Clusters. Astrophys. Journal, 591, L131
C. Heinke et al. Analysis of the Quiescent Low-Mass X-ray Binary Population in Galactic Globular Clusters, 2003, Astrophysical Journal (in press) |
Color
Code
|
Energy (Red 0.5-1.2 keV, Green 1.2-2.5 keV, Blue 2.5-6 keV)
|
Instrument |
ACIS |
Distance
Estimate
|
About 20,000 light years from Earth
|
Release Date
|
July 30, 2003
|
|
Fast Facts for
NGC 7099:
|
Credit
|
NASA/CXC/UIn/H.Cohn & P.Lugger et al.
|
Scale
|
Image is approx. 1.9 arcmin on a side.
|
Category
|
Normal Stars & Star Clusters, Neutron Stars/X-ray Binaries
|
Coordinates
(J2000)
|
RA 21h 40m 22.00s | Dec -23° 10' 45.00"
|
Constellation
|
Capricornus |
Observation
Date
|
November 19, 2001
|
Observation
Time
|
13.9 hours
|
Obs.
ID
|
2679
|
Also Known As | M30, | References | D. Pooley et al. 2003, Dynamical Formation of Close Binary Systems in Globular Clusters. Astrophys. Journal, 591, L131
C. Heinke et al. Analysis of the Quiescent Low-Mass X-ray Binary Population in Galactic Globular Clusters, 2003, Astrophysical Journal (in press) |
Color
Code
|
Energy (Red 0.5-1.2 keV, Green 1.2-2.5 keV, Blue 2.5-6 keV)
|
Instrument |
ACIS |
Distance
Estimate
|
About 30,000 light years from Earth
|
Release Date
|
July 30, 2003
|
|