Andrew Yee
January 10th 06, 03:16 PM
Office of Public Affairs and Educational Outreach
National Optical Astronomy Observatory
Tucson, Arizona
For More Information:
Douglas Isbell
Office of Public Affairs and Educational Outreach
National Optical Astronomy Observatory
Phone: 520/318-8230
Whitney Clavin
Jet Propulsion Laboratory
Phone: (818) 354-4673
EMBARGOED FOR RELEASE: 9:20 a.m. EST, Tuesday, January 10, 2006
RELEASE NO: NOAO 06-04
Spitzer Reveals Unexpected Disks Around Interacting Stars
New Spitzer Space Telescope observations of an unusual class of
interacting binary stars detected excess amounts of infrared radiation,
suggesting that these odd objects are surrounded by large disks of cool
dust.
The results reported today in Washington, DC, at the 207th meeting of the
American Astronomical Society (AAS) were produced by one of six teams of
professional astronomers and high school teachers participating in a
unique program co-sponsored by the Spitzer Science Center and the National
Optical Astronomy Observatory (NOAO).
The type of cataclysmic variable system being studied by the team consists
of a highly magnetic white dwarf star (a "dead" remnant star formed from
the core of a star like our Sun when it exhausts the available fuel to
support nuclear fusion) and a very low mass, cool object similar to a
brown dwarf. The two objects orbit so closely -- about the distance from
Earth to the Moon -- that they make a complete revolution about each other
in only 80-90 minutes. The white dwarf is Earth-sized but weighs about 60
percent of the mass of the Sun, while the companion star is Jupiter-sized
but has about 40-50 times the mass of Jupiter.
The high mass of the white dwarf and the closeness of the companion result
in mass exchange between the two stars. The gravitational influence of the
white dwarf squeezes the companion star into a teardrop shape, and matter
squirts from its pointed end toward the white dwarf, like water from the
nozzle of a garden hose. This material eventually falls onto the white
dwarf, causing tremendous heating of its atmosphere and the emission of a
large amount of energy from X-rays to the far infrared.
A team of astronomers and teachers led by Steve B. Howell of NOAO observed
four of these types of binaries with NASA's Spitzer Space Telescope in an
attempt to study the cool, low-mass object in the pair: EF Eridanus, V347
Pav, GG Leo and RX J0154.
To their surprise, excess infrared emission was discovered around all
four. The team's current best model for its origin is a large, cool
circumbinary dust disk with a temperature of about 800-1,200 Kelvin
(980-1,700 degrees Fahrenheit).
"Our explanation at this point is that the emission originates from a
large, relatively cool disk of dust encircling the entire binary system,"
Howell says. "The discovery of dust disks around these old interacting
binaries is very exciting. We have shown our initial results to a variety
of specialists, and nobody yet has a better idea of what we are seeing."
Such circumbinary disks have been predicted on theoretical grounds and a
few observational studies have attempted to find them, with mixed results.
The disks may be the remains of the large "mass-loss" episode that
occurred during the formation of the white dwarf. They also could be
composed of material spewed from the binary in the form of strong winds
(like a very dense version of our Sun's solar wind), or material that was
ejected during one or more previous nova explosions. Cyclotron emission
due to the large magnetic field of the white dwarfs in these particular
binaries cannot be eliminated completely as another potential source of at
least part of the infrared emission.
"A number of ideas are on the table, as well the possibility of some
still-unknown process," Howell adds. "These objects are ripe for further
study."
Only two other white dwarfs (including one newly discovered) are known to
be encircled by a dust disk -- stars named G29-38 and GD362. Unlike the
cataclysmic variables studied by Howell's team, both of these are single
white dwarfs, and the source of their dust disks is not known for certain.
Dust disks made up of "left over" material from the star formation process
are known to exist around very young stars and have been discovered around
Sun-like stars as well. Some of these latter disks are known to harbor
planetary-type objects, orbiting in cleared out "rings" within the disk.
"While we have no evidence for planetary objects in our disks, the
possibility does exist," Howell adds. "More work must be done to prove the
infrared excess is from a disk and, if true, to discover its properties
such as density and composition. We also would like to see if these disks
exist in every interacting binary of this type or only in some. Their
presence would greatly change our concept of the evolution of such
systems."
These types of systems are important because they give astronomers insight
into the accretion, or "mass transfer," process that also plays a role in
the formation of stars and planets, according to team member Donald W.
Hoard, an astronomer at the Spitzer Science Center in Pasadena,
California.
"Cataclysmic variable accretion is one of the least complicated forms of
mass transfer in the Universe," Hoard says. "These systems are great to
observe, because unlike accretion during the formation of stars and
planets, or around supermassive black holes in far off galaxies, the
process in cataclysmic variables happens on relatively short, human
timescales."
A color graphic to illustrate this result is available at
http://www.noao.edu/outreach/press/pr06/pr0604.html#images
Other members of the research team reporting in poster 70.17 today at the
AAS meeting include Carolyn Brinkworth of the Spitzer Science Center, and
physics teachers Howard Chun from Cranston High School in East Cranston,
Rhode Island; Beth Thomas of Great Falls Public Schools in Great Falls,
Montana; and, Linda Stefaniak of Allentown High School, Allentown, New
Jersey.
Chun, Thomas and Stefaniak are graduates of NOAO's Teacher Leaders in
Research Based Science Education (TLRBSE)
[http://www.noao.edu/outreach/tlrbse/], a teacher professional development
program funded by the National Science Foundation. Twelve TLRBSE teachers
were competitively selected in the fall of 2004 to work in six teams that
were awarded three hours of Director's discretionary observing time with
Spitzer.
"This opportunity has allowed my students and myself to participate in
authentic astronomy research," Thomas says. "It has given me a deeper
understanding of the world of infrared and astronomy, while reinforcing
how we teach the process of problem solving and how answers are sought in
the science community. The experience has been very enlightening,
extremely rewarding and genuinely stimulating."
Another six TLRBSE teachers were just selected for a second round of the
program, and these teachers met with their astronomer partners during this
AAS meeting to begin planning new research. Background information on the
Spitzer-TLRBSE program and the experience of the teachers and their
students in this group can be found on the Web at the Spitzer Web Site,
http://www.spitzer.caltech.edu/Media/happenings/20050816/
The National Optical Astronomy Observatory is operated by the Association
of Universities for Research in Astronomy Inc. (AURA), under a cooperative
agreement with the National Science Foundation.
The Jet Propulsion Laboratory manages the Spitzer Space Telescope mission
for NASA's Science Mission Directorate. Science operations are conducted
at the Spitzer Science Center at Caltech. JPL is a division of Caltech.
National Optical Astronomy Observatory
Tucson, Arizona
For More Information:
Douglas Isbell
Office of Public Affairs and Educational Outreach
National Optical Astronomy Observatory
Phone: 520/318-8230
Whitney Clavin
Jet Propulsion Laboratory
Phone: (818) 354-4673
EMBARGOED FOR RELEASE: 9:20 a.m. EST, Tuesday, January 10, 2006
RELEASE NO: NOAO 06-04
Spitzer Reveals Unexpected Disks Around Interacting Stars
New Spitzer Space Telescope observations of an unusual class of
interacting binary stars detected excess amounts of infrared radiation,
suggesting that these odd objects are surrounded by large disks of cool
dust.
The results reported today in Washington, DC, at the 207th meeting of the
American Astronomical Society (AAS) were produced by one of six teams of
professional astronomers and high school teachers participating in a
unique program co-sponsored by the Spitzer Science Center and the National
Optical Astronomy Observatory (NOAO).
The type of cataclysmic variable system being studied by the team consists
of a highly magnetic white dwarf star (a "dead" remnant star formed from
the core of a star like our Sun when it exhausts the available fuel to
support nuclear fusion) and a very low mass, cool object similar to a
brown dwarf. The two objects orbit so closely -- about the distance from
Earth to the Moon -- that they make a complete revolution about each other
in only 80-90 minutes. The white dwarf is Earth-sized but weighs about 60
percent of the mass of the Sun, while the companion star is Jupiter-sized
but has about 40-50 times the mass of Jupiter.
The high mass of the white dwarf and the closeness of the companion result
in mass exchange between the two stars. The gravitational influence of the
white dwarf squeezes the companion star into a teardrop shape, and matter
squirts from its pointed end toward the white dwarf, like water from the
nozzle of a garden hose. This material eventually falls onto the white
dwarf, causing tremendous heating of its atmosphere and the emission of a
large amount of energy from X-rays to the far infrared.
A team of astronomers and teachers led by Steve B. Howell of NOAO observed
four of these types of binaries with NASA's Spitzer Space Telescope in an
attempt to study the cool, low-mass object in the pair: EF Eridanus, V347
Pav, GG Leo and RX J0154.
To their surprise, excess infrared emission was discovered around all
four. The team's current best model for its origin is a large, cool
circumbinary dust disk with a temperature of about 800-1,200 Kelvin
(980-1,700 degrees Fahrenheit).
"Our explanation at this point is that the emission originates from a
large, relatively cool disk of dust encircling the entire binary system,"
Howell says. "The discovery of dust disks around these old interacting
binaries is very exciting. We have shown our initial results to a variety
of specialists, and nobody yet has a better idea of what we are seeing."
Such circumbinary disks have been predicted on theoretical grounds and a
few observational studies have attempted to find them, with mixed results.
The disks may be the remains of the large "mass-loss" episode that
occurred during the formation of the white dwarf. They also could be
composed of material spewed from the binary in the form of strong winds
(like a very dense version of our Sun's solar wind), or material that was
ejected during one or more previous nova explosions. Cyclotron emission
due to the large magnetic field of the white dwarfs in these particular
binaries cannot be eliminated completely as another potential source of at
least part of the infrared emission.
"A number of ideas are on the table, as well the possibility of some
still-unknown process," Howell adds. "These objects are ripe for further
study."
Only two other white dwarfs (including one newly discovered) are known to
be encircled by a dust disk -- stars named G29-38 and GD362. Unlike the
cataclysmic variables studied by Howell's team, both of these are single
white dwarfs, and the source of their dust disks is not known for certain.
Dust disks made up of "left over" material from the star formation process
are known to exist around very young stars and have been discovered around
Sun-like stars as well. Some of these latter disks are known to harbor
planetary-type objects, orbiting in cleared out "rings" within the disk.
"While we have no evidence for planetary objects in our disks, the
possibility does exist," Howell adds. "More work must be done to prove the
infrared excess is from a disk and, if true, to discover its properties
such as density and composition. We also would like to see if these disks
exist in every interacting binary of this type or only in some. Their
presence would greatly change our concept of the evolution of such
systems."
These types of systems are important because they give astronomers insight
into the accretion, or "mass transfer," process that also plays a role in
the formation of stars and planets, according to team member Donald W.
Hoard, an astronomer at the Spitzer Science Center in Pasadena,
California.
"Cataclysmic variable accretion is one of the least complicated forms of
mass transfer in the Universe," Hoard says. "These systems are great to
observe, because unlike accretion during the formation of stars and
planets, or around supermassive black holes in far off galaxies, the
process in cataclysmic variables happens on relatively short, human
timescales."
A color graphic to illustrate this result is available at
http://www.noao.edu/outreach/press/pr06/pr0604.html#images
Other members of the research team reporting in poster 70.17 today at the
AAS meeting include Carolyn Brinkworth of the Spitzer Science Center, and
physics teachers Howard Chun from Cranston High School in East Cranston,
Rhode Island; Beth Thomas of Great Falls Public Schools in Great Falls,
Montana; and, Linda Stefaniak of Allentown High School, Allentown, New
Jersey.
Chun, Thomas and Stefaniak are graduates of NOAO's Teacher Leaders in
Research Based Science Education (TLRBSE)
[http://www.noao.edu/outreach/tlrbse/], a teacher professional development
program funded by the National Science Foundation. Twelve TLRBSE teachers
were competitively selected in the fall of 2004 to work in six teams that
were awarded three hours of Director's discretionary observing time with
Spitzer.
"This opportunity has allowed my students and myself to participate in
authentic astronomy research," Thomas says. "It has given me a deeper
understanding of the world of infrared and astronomy, while reinforcing
how we teach the process of problem solving and how answers are sought in
the science community. The experience has been very enlightening,
extremely rewarding and genuinely stimulating."
Another six TLRBSE teachers were just selected for a second round of the
program, and these teachers met with their astronomer partners during this
AAS meeting to begin planning new research. Background information on the
Spitzer-TLRBSE program and the experience of the teachers and their
students in this group can be found on the Web at the Spitzer Web Site,
http://www.spitzer.caltech.edu/Media/happenings/20050816/
The National Optical Astronomy Observatory is operated by the Association
of Universities for Research in Astronomy Inc. (AURA), under a cooperative
agreement with the National Science Foundation.
The Jet Propulsion Laboratory manages the Spitzer Space Telescope mission
for NASA's Science Mission Directorate. Science operations are conducted
at the Spitzer Science Center at Caltech. JPL is a division of Caltech.