J.D. Harrington
Headquarters, Washington
202-358-5241
j.d.harrington@nasa.gov
Ray Villard
Space Telescope Science Institute, Baltimore
410-338-4514
villard@stsci.edu
RELEASE: 13-172
NASA'S HUBBLE MAPS 3-D STRUCTURE OF EJECTED MATERIAL AROUND ERUPTING STAR
WASHINGTON -- A flash of light from a stellar outburst has provided a
rare look at the 3-D structure of material ejected by an erupting
nova.
Astronomers used NASA's Hubble Space Telescope to observe the light
emitted by the close double-star system T Pyxidis, or T Pyx, a
recurring nova, during its latest outburst in April 2011.
A nova erupts when a white dwarf, the burned-out core of a sun-like
star, has siphoned off enough hydrogen from a companion star to
trigger a thermonuclear runaway. As hydrogen builds up on the surface
of the white dwarf, it becomes hotter and denser until it detonates
like a colossal hydrogen bomb, leading to a 10,000-fold increase in
brightness in a little more than one day. Nova explosions are
extremely powerful, equal to a blast of one million billion tons of
dynamite. T Pyx erupts every 12 to 50 years.
Contrary to some predictions, the astronomers were surprised to find
the ejecta from earlier outbursts stayed in the vicinity of the star
and formed a disk of debris around the nova. The discovery suggests
material continues expanding outward along the system's orbital
plane, but it does not escape the system.
"We fully expected this to be a spherical shell," says Arlin Crotts of
Columbia University, a member of the research team. "This observation
shows it is a disk, and it is populated with fast-moving ejecta from
previous outbursts."
Team member Stephen Lawrence of Hofstra University in Hempstead, N.Y.,
will present the results Tuesday at the American Astronomical Society
meeting in Indianapolis.
Team member Jennifer Sokoloski, also of Columbia University and
co-investigator on the project, suggests these data indicate the
companion star plays an important role in shaping how material is
ejected, presumably along the system's orbital plane, creating the
pancake-shaped disk. The disk is tilted about 30 degrees from face-on
toward Earth.
Using Hubble's Wide Field Camera 3, the team took advantage of the
blast of light emitted by the erupting nova to trace the light's path
as it lit up the disk and material from previous ejecta. The disk is
so vast, about a light-year across, that the nova's light cannot
illuminate all of the material at once. Instead, the light sweeps
across the material, sequentially illuminating parts of the disk, a
phenomenon called a light echo. The light reveals which parts of the
disk are nearer to Earth and which sections are farther away. By
tracing the light, the team assembled a 3-D map of the structure
around the nova.
"We've all seen how light from fireworks shells during the grand
finale will light up the smoke and soot from shells earlier in the
show," Lawrence said. "In an analogous way, we're using light from T
Pyx's latest outburst and its propagation at the speed of light to
dissect its fireworks displays from decades past."
Although astronomers have witnessed light propagating through material
surrounding other novae, this is the first time the immediate
environment around an erupting star has been studied in three
dimensions.
Astronomers have studied light echoes from other novae, but those
phenomena illuminated interstellar material around the stars instead
of material ejected from them.
The team also used the light echo to refine estimates of the nova's
distance from Earth. The new distance is 15,600 light-years from
Earth. Previous estimates were between 6,500 and 16,000 light-years.
T Pyx is located in the southern constellation Pyxis, or the
Mariner's Compass.
The team is continuing to analyze the Hubble data to develop an
outflow model. T Pyx has a history of outbursts. Besides the 2011
event, other previous known eruptions were seen in 1890, 1902, 1920,
1944, and 1966.
Astronomers call erupting stars novae, Latin for "new," because they
abruptly appear in the sky. A nova quickly begins to fade in several
days or weeks as the hydrogen is exhausted and blown into space.
The team also includes Helena Uthas of Columbia University. The team's
results will appear online Wednesday, June 5 and will be published in
the June 20 issue of the Astrophysical Journal Letters. Sokoloski is
the paper's lead author.
For images, and more information about T Pyxidis, visit:
http://hubblesite.org/news/2013/21 For more information about NASA's Hubble Space Telescope, visit:
http://www.nasa.gov/hubble
