June 6th 06, 05:32 PM
http://www.cfa.harvard.edu/press/pr0616.html
Harvard-Smithsonian Center for Astrophysics
Release No.: 06-16
For Release: 9:30 a.m. MDT (11:30 a.m. EDT) Monday, June 5, 2006
Note to editors: High-resolution artwork to accompany this release is
online at http://www.cfa.harvard.edu/press/pr0616image.html
Jupiter's "Big Brother" Has Moon-Forming Dust Disk
Calgary, AB - Earth's Moon was created by an early collision with
another large planetary body. It was a "chip off the old block." Mars
captured its asteroidal moons as they passed by. But Jupiter made its
own moons out of dust and gas remaining from its formation. Now,
observations by astronomer Subhanjoy Mohanty of the Harvard-Smithsonian
Center for Astrophysics (CfA) and his colleagues provide the first
direct evidence for a dusty disk around a distant planet that in mass
would be Jupiter's "big brother."
"It is quite possible that moons or moonlets could form out of this
disk, just as they have around the giant planets in our own solar
system," said Mohanty.
Mohanty presented the discovery today in a press conference at the
208th
meeting of the American Astronomical Society. Other members of the team
are Ray Jayawardhana (University of Toronto), Nuria Hu?lamo (ESO) and
Eric Mamajek (CfA).
The team studied a planetary mass object known as 2MASS1207-3932B,
which
is located about 170 light-years from Earth in the direction of the
constellation Centaurus. 2M1207B, as it is abbreviated, orbits a tiny
brown dwarf star at a separation of about 40 astronomical units, or 3.7
billion miles - comparable to the size of Pluto's orbit. That
separation
is much larger than typical for binary brown dwarf systems. The wide
separation may indicate that the duo formed in relative isolation, far
from passing stars that could have pulled them apart.
"This system probably won't survive for long. It won't last 5 billion
years like our solar system has," said Mamajek. "All it would take is
for a more massive interloper star to come along and yank the planet
away from the brown dwarf."
Observations by Mohanty's team showed that the brown dwarf has a mass
of
about 25 Jupiters and a temperature of 4100 degrees Fahrenheit (2600
K).
Its companion 2M1207B weighs about 8 times Jupiter and has a
temperature
of 2400 degrees F (1600 K). Both objects are warm due to their young
age
of 5-10 million years, having retained the heat of formation.
Given those temperatures, the team then calculated the expected
brightness of both objects. The brown dwarf matched predictions but its
companion was about 8 times fainter than expected. After examining
several potential causes, the team concluded that the only plausible
explanation was the presence of an edge-on dusty disk that blocked most
of the planet's light. The planet is seen only in light scattered from
the disk.
Spectral analysis shows that 2M1207B is a gas giant like Jupiter with
no
solid surface. As a result, it would be a poor abode for life. Any
moons
that might form around it, however, could prove more hospitable.
The large mass of 2M1207B relative to the brown dwarf star poses a
puzzle for planetary formation theories. Typical planets like those in
our solar system are less than one-hundredth the size of the central
star. In contrast, 2M1207B holds one-third as much mass as the brown
dwarf.
"Mass ratios of that size are more typical for binary stars than for
planetary systems," said Mohanty. "2M1207B probably formed like a star,
together with the brown dwarf, rather than from core accretion like
giant planets around other stars."
Mohanty and his colleagues plan to study the polarization of light from
2M1207B in order to investigate the inclination of its disk as well as
the size of dust grains within the disk. Further studies await the next
generation of large telescopes, such as the Giant Magellan Telescope
and
the Atacama Large Millimeter Array, which may be able to directly
detect
the disk around the planetary mass companion.
Headquartered in Cambridge, Mass., the Harvard-Smithsonian Center for
Astrophysics (CfA) is a joint collaboration between the Smithsonian
Astrophysical Observatory and the Harvard College Observatory. CfA
scientists, organized into six research divisions, study the origin,
evolution and ultimate fate of the universe.
For more information, contact:
David A. Aguilar
Director of Public Affairs
Harvard-Smithsonian Center for Astrophysics
617-495-7462
Christine Pulliam
Public Affairs Specialist
Harvard-Smithsonian Center for Astrophysics
Phone: 617-495-7463, Fax: 617-495-7016
Harvard-Smithsonian Center for Astrophysics
Release No.: 06-16
For Release: 9:30 a.m. MDT (11:30 a.m. EDT) Monday, June 5, 2006
Note to editors: High-resolution artwork to accompany this release is
online at http://www.cfa.harvard.edu/press/pr0616image.html
Jupiter's "Big Brother" Has Moon-Forming Dust Disk
Calgary, AB - Earth's Moon was created by an early collision with
another large planetary body. It was a "chip off the old block." Mars
captured its asteroidal moons as they passed by. But Jupiter made its
own moons out of dust and gas remaining from its formation. Now,
observations by astronomer Subhanjoy Mohanty of the Harvard-Smithsonian
Center for Astrophysics (CfA) and his colleagues provide the first
direct evidence for a dusty disk around a distant planet that in mass
would be Jupiter's "big brother."
"It is quite possible that moons or moonlets could form out of this
disk, just as they have around the giant planets in our own solar
system," said Mohanty.
Mohanty presented the discovery today in a press conference at the
208th
meeting of the American Astronomical Society. Other members of the team
are Ray Jayawardhana (University of Toronto), Nuria Hu?lamo (ESO) and
Eric Mamajek (CfA).
The team studied a planetary mass object known as 2MASS1207-3932B,
which
is located about 170 light-years from Earth in the direction of the
constellation Centaurus. 2M1207B, as it is abbreviated, orbits a tiny
brown dwarf star at a separation of about 40 astronomical units, or 3.7
billion miles - comparable to the size of Pluto's orbit. That
separation
is much larger than typical for binary brown dwarf systems. The wide
separation may indicate that the duo formed in relative isolation, far
from passing stars that could have pulled them apart.
"This system probably won't survive for long. It won't last 5 billion
years like our solar system has," said Mamajek. "All it would take is
for a more massive interloper star to come along and yank the planet
away from the brown dwarf."
Observations by Mohanty's team showed that the brown dwarf has a mass
of
about 25 Jupiters and a temperature of 4100 degrees Fahrenheit (2600
K).
Its companion 2M1207B weighs about 8 times Jupiter and has a
temperature
of 2400 degrees F (1600 K). Both objects are warm due to their young
age
of 5-10 million years, having retained the heat of formation.
Given those temperatures, the team then calculated the expected
brightness of both objects. The brown dwarf matched predictions but its
companion was about 8 times fainter than expected. After examining
several potential causes, the team concluded that the only plausible
explanation was the presence of an edge-on dusty disk that blocked most
of the planet's light. The planet is seen only in light scattered from
the disk.
Spectral analysis shows that 2M1207B is a gas giant like Jupiter with
no
solid surface. As a result, it would be a poor abode for life. Any
moons
that might form around it, however, could prove more hospitable.
The large mass of 2M1207B relative to the brown dwarf star poses a
puzzle for planetary formation theories. Typical planets like those in
our solar system are less than one-hundredth the size of the central
star. In contrast, 2M1207B holds one-third as much mass as the brown
dwarf.
"Mass ratios of that size are more typical for binary stars than for
planetary systems," said Mohanty. "2M1207B probably formed like a star,
together with the brown dwarf, rather than from core accretion like
giant planets around other stars."
Mohanty and his colleagues plan to study the polarization of light from
2M1207B in order to investigate the inclination of its disk as well as
the size of dust grains within the disk. Further studies await the next
generation of large telescopes, such as the Giant Magellan Telescope
and
the Atacama Large Millimeter Array, which may be able to directly
detect
the disk around the planetary mass companion.
Headquartered in Cambridge, Mass., the Harvard-Smithsonian Center for
Astrophysics (CfA) is a joint collaboration between the Smithsonian
Astrophysical Observatory and the Harvard College Observatory. CfA
scientists, organized into six research divisions, study the origin,
evolution and ultimate fate of the universe.
For more information, contact:
David A. Aguilar
Director of Public Affairs
Harvard-Smithsonian Center for Astrophysics
617-495-7462
Christine Pulliam
Public Affairs Specialist
Harvard-Smithsonian Center for Astrophysics
Phone: 617-495-7463, Fax: 617-495-7016