More Images of GRO J1655-40
Illustration of a Stellar-Mass Black Hole
This is an artist's representation of GRO J1655-40, a binary star system observed in April 2005 by Chandra. This binary consists of a black hole and a normal star shown in blue. Gas is being pulled away from the star and falling onto a red disk spinning around the black hole. Some of this gas spirals in towards the black hole, generating copious amounts of light along the way. This infall of matter is only possible if the gas loses some of its energy either through a wind, shown in blue, or friction in the disk.
Chandra X-ray Spectrum of GRO J1655-40
This shows an X-ray spectrum obtained by Chandra observations. The dips
seen in the spectrum are produced by absorption from a wide variety of
atoms in the gas around the black hole, ranging from oxygen to nickel. A
detailed study of these absorption features shows that the atoms are
highly ionized and are moving away from the black hole in a high-speed
wind. The conclusion of this study is that this wind is driven by
(Credit: NASA/CXC/U.Michigan/J.Miller et al.)
Evidence for Wind in the GRO J1655-40 Spectrum
The X-ray spectra in this figure show evidence for a wind in GRO
J1655-40. The dips seen here are produced by absorption from a wide variety
of atoms in the gas around the black hole. The blue line shows the Chandra
spectrum of J1655 and the yellow line shows a model spectrum. In the model
spectrum the absorption dips are plotted at their natural wavelengths, that
is their expected location for gas that is not undergoing bulk motion
either towards or away from us. Comparing the two spectra shows that the
Chandra spectrum is shifted towards shorter wavelengths because of the
Doppler effect, giving evidence for a wind blowing towards us.
(Credit: NASA/CXC/U.Michigan/J.Miller et al.)
Illustration of Magnetic Fields in GRO J1655-40
This artist's representation shows how magnetic fields may drive a wind in
GRO J1655-40. Rotation in the disk plus magnetic actions in the disk can
cause magnetic fields, shown here in this simplified version as black
lines, to become coiled up like a snake. This can result in gas being
driven upwards and away from the disk by pressure created by the magnetic
fields, resulting in the wind observed by Chandra.
This is an artist's representation of an active galactic nucleus (AGN) at
the center of a galaxy. Gas is pulled towards a supermassive black hole and
falls onto a disk, shown in red. Some of this gas spirals inwards,
generating massive amounts of radiation before falling onto the black
hole. This infall of matter is only possible if the gas loses some of its
energy either through a wind, shown in blue, or friction in the disk. The
most spectacular AGN behavior is seen in quasars, the brightest objects
known in the Universe.
Comparison of an AGN and a Stellar-Mass Black Hole
These two illustrations compare the basic structure of an active galactic
nucleus (AGN) and a stellar-mass black hole in a binary system. The AGN
contains a supermassive black hole attracting gas from the central regions
of a galaxy, while the stellar-mass black hole, typically with a mass about
5-10 times that of the Sun, is rapidly pulling gas from a normal companion
star. Although the stellar-mass black hole is millions of times smaller
than the black hole in the AGN, there are many similarities in structure
between these two types of object. As shown here, both contain black holes
surrounded by a disk of hot gas, and a wind blowing away from the disk.
There are also many similarities in observational properties. Stellar-mass
black holes can therefore be used as scale-models of AGN, and the mechanism
that drives the wind - causing gas in the disk to lose energy and fall onto
the black hole - is expected to be the same for both classes.
A Familiar Disk: Saturn
This illustration shows the rings of Saturn, an example of a disk that is
very familiar to us. The material in this disk loses very little energy
because of friction. Therefore, compared to a black hole such as GRO
J1655-40, the disk is very stable, and is much cooler and fainter.
Return to GRO J1655-40
(June 21, 2006)
Image Sequence of a Black Hole Pulling Matter from Companion Star
This image sequence shows the orbit of the binary system GRO J1655-40. Gas is
being pulled away from a normal star, shown in blue, and crashes onto a
red disk that is spinning around a central black hole. The animation
then zooms in to show a closer view of the disk. Some of the gas in the
disk spirals inwards and falls onto the black hole, generating light
along the way, and some of it is blown away in a wind.