Rings of X-ray light centered on V404 Cygni, a
binary system containing an erupting black hole (dot at center), were
imaged by the X-ray Telescope aboard NASA's Swift satellite from June 30
to July 4. A narrow gap splits the middle ring in two. Color indicates
the energy of the X-rays, with red representing the lowest (800 to 1,500
electron volts, eV), green for medium (1,500 to 2,500 eV), and the most
energetic (2,500 to 5,000 eV) shown in blue. For comparison, visible
light has energies ranging from about 2 to 3 eV. The dark lines running
diagonally through the image are artifacts of the imaging system. Credits: Andrew Beardmore (Univ. of Leicester) and NASA/Swift. Download frames from NASA Goddard's Scientific Visualization Studio
The Swift X-ray image of V404 Cygni covers a patch
of the sky equal to about half the apparent diameter of the full moon.
This image shows the rings as they appeared on June 30. Credits: NASA's Scientific Visualization Studio (left), Andrew Beardmore (Univ. of Leicester); NASA/Swift (right)
What looks like a shooting target is actually an image of nested
rings of X-ray light centered on an erupting black hole. On June 15,
NASA's Swift satellite detected the start of a new outburst from V404
Cygni, where a black hole and a sun-like star orbit each other. Since
then, astronomers around the world have been monitoring the ongoing
light show.
On June 30, a team led by Andrew Beardmore at the University of
Leicester, U.K., imaged the system using the X-ray Telescope aboard
Swift, revealing a series concentric rings extending about one-third the
apparent size of a full moon. A movie made by combining additional
observations acquired on July 2 and 4 shows the expansion and gradual
fading of the rings.
Astronomers say the rings result from an "echo" of X-ray light. The
black hole's flares emit X-rays in all directions. Dust layers reflect
some of these X-rays back to us, but the light travels a longer distance
and reaches us slightly later than light traveling a more direct path.
The time delay creates the light echo, forming rings that expand with
time.
Detailed analysis of the expanding rings shows that they all
originate from a large flare that occurred on June 26 at 1:40 p.m. EDT.
There are multiple rings because there are multiple reflecting dust
layers between 4,000 and 7,000 light-years away from us. Regular
monitoring of the rings and how they change as the eruption continues
will allow astronomers to better understand their nature.
"The flexible planning of Swift observations has given us the best
dust-scattered X-ray ring images ever seen," Beardmore said. "With these
observations we can make a detailed study of the normally invisible
interstellar dust in the direction of this black hole."
V404 Cygni is located about 8,000 light-years away. Every couple of
decades the black hole fires up in an outburst of high-energy light. Its
previous eruption ended in 1989.
The investigating team includes scientists from the Universities of
Leicester, Southampton, and Oxford in the U.K., the University of
Alberta in Canada, and the European Space Agency in Spain.
Swift was launched in November 2004 and is managed by NASA's Goddard
Space Flight Center in Greenbelt, Maryland. Goddard operates the
spacecraft in collaboration with Penn State University in University
Park, Pennsylvania, the Los Alamos National Laboratory in New Mexico and
Orbital Sciences Corp. in Dulles, Virginia. International collaborators
are located in the United Kingdom and Italy. The mission includes
contributions from Germany and Japan.
Related Links
- NASA Missions Monitor a Waking Black Hole
- INTEGRAL light curve of V404 Cygni
- NASA’s Chandra Captures X-Ray Echoes Pinpointing Distant Neutron Star
