A Ten-Year, Time-Lapsed Movie of the Galaxy
(caption for the "New ASM Movie: 10 years of RXTE!" on the RXTE Movies page.)
The night sky has been a source of wonder since the dawn of
humankind. The countless stars seem immaculate and immutable.
Although the positions of stars change from season to season, the
stars themselves appear as steady beacons to our eyes. But
viewed in X-ray light, the universe is radically different.
If our eyes could detect X-ray radiation, we would see objects far
more energetic than ordinary stars---some flickering on and off like
fireflies, others erupting like volcanoes. Black holes, neutron
stars and pulsars locked in tight binary star systems... these are
objects that suddenly "turn on" for weeks or months at a
time before growing dormant for years or decades. They are
powered by the whims of accretion---unpredictable flows of hot gas
from companion stars under the force of extreme gravity.
This movie depicts 10 years of continuous monitoring of the X-ray sky
based entirely on actual data from NASA's Rossi X-ray Timing Explorer,
launched on December 30, 1995. Note how some objects flicker
into existence and disappear for months on end. Others are
relatively steady sources of X-rays yet they glow brighter and dimmer
depending on their fuel supply.
Blue represents the most energetic X-rays detected; green, less
energetic; and red, the least energetic. In general, blue
sources are high-mass X-ray binary pulsars; red sources are low-mass X-ray
binaries. Many steady sources are green, such as the Crab pulsar which is
the source at the far right.
The bright source in the center above the galactic plane is
Scorpius-X1, the first cosmic X-ray source ever detected and now
believed to be a neutron star. Cygnus X-1, a black hole candidate,
is a bright source on the galactic equator just to the left of the
activity in the galactic center.
The movie was created by Donald A. Smith (MIT), Michael Muno (UCLA),
Alan M. Levine (MIT), Ronald Remillard (MIT), Edward Morgan (MIT) and
Hale Bradt (MIT). The data comes from the MIT-built All-Sky
Monitor, one of three instruments on the Rossi Explorer.
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