Andrew Yee
March 14th 06, 05:18 AM
Public Affairs Office
Harvard-Smithsonian Center for Astrophysics
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
For Release: Embargoed until 8:00 p.m. EST, Monday, March 13, 2006
Release No.: 06-14
Super-Earths May Be Three Times More Common Than Jupiters
Cambridge, MA -- Astronomers have discovered a new "super-Earth" orbiting
a red dwarf star located about 9,000 light-years away. This newfound world
weighs about 13 times the mass of the Earth and is probably a mixture of
rock and ice, with a diameter several times that of Earth. It orbits its
star at about the distance of the asteroid belt in our solar system, 250
million miles out. Its distant location chills it to -330 degrees
Fahrenheit, suggesting that although this world is similar in structure to
the Earth, it is too cold for liquid water or life.
Orbiting almost as far out as Jupiter does in our solar system, this
"super-Earth" likely never accumulated enough gas to grow to giant
proportions. Instead, the disk of material from which it formed
dissipated, starving it of the raw materials it needed to thrive.
"This is a solar system that ran out of gas," says Harvard astronomer
Scott Gaudi of the Harvard-Smithsonian Center for Astrophysics (CfA), a
member of the MicroFUN collaboration that spotted the planet.
The discovery is being reported today in a paper posted online at
http://arxiv.org/abs/astro-ph/0603276
and submitted to The Astrophysical Journal Letters for publication.
Gaudi performed extensive data analysis that confirmed the existence of
the planet. Further analysis simultaneously ruled out the presence of any
Jupiter-sized world in the distant solar system.
"This icy super-Earth dominates the region around its star that, in our
solar system, is populated by the gas giant planets," said first author
Andrew Gould (Ohio State University), who leads MicroFUN.
The team also calculates that about one-third of all main sequence stars
may have similar icy super-Earths. Theory predicts that smaller planets
should be easier to form than larger ones around low-mass stars. Since
most Milky Way stars are red dwarfs, solar systems dominated by
super-Earths may be more common in the Galaxy than those with giant
Jupiters.
This discovery sheds new light on the process of solar system formation.
Material orbiting a low-mass star accumulates into planets gradually,
leaving more time for the gas in the protoplanetary disk to dissipate
before large planets have formed. Low-mass stars also tend to have less
massive disks, offering fewer raw materials for planet formation.
"Our discovery suggests that different types of solar systems form around
different types of stars," explains Gaudi. "Sun-like stars form Jupiters,
while red dwarf stars only form super-Earths. Larger A-type stars may even
form brown dwarfs in their disks."
Astronomers found the planet using a technique called microlensing, an
Einsteinian effect in which the gravity of a foreground star magnifies the
light of a more distant star. If the foreground star possesses a planet,
the planet's gravity can distort the light further, thereby signaling its
presence. The precise alignment required for the effect means that each
microlensing event lasts for only a brief time. Astronomers must monitor
many stars closely to detect such events.
Microlensing is sensitive to less massive planets than the more common
planet-finding methods of radial velocity and transit searches.
"Microlensing is the only way to detect Earth-mass planets from the ground
with current technology," says Gaudi. "If there had been an Earth-mass
planet in the same region as this super-Earth, and if the alignment had
been just right, we could have detected it. By adding one more two-meter
telescope to our arsenal, we may be able to find up to a dozen Earth-mass
planets every year."
The OGLE (Optical Gravitational Lensing Experiment) collaboration
initially discovered the microlensed star in April 2005 while peering in
the direction of the galactic center, where both foreground and background
stars are widespread. OGLE identifies several hundred microlensing events
per year, however only a small fraction of those events yield planets.
Gaudi estimates that with one or two additional telescopes located in the
southern hemisphere to monitor the galactic center, the planet count could
jump drastically.
The discovery was made by 36 astronomers, including members of the
MicroFUN, OGLE, and Robonet collaborations. The name of the planet is
OGLE-2005-BLG-169Lb. OGLE-2005-BLG-169 refers to the 169th microlensing
event discovered by the OGLE Collaboration toward the Galactic bulge in
2005, and "Lb" refers to a planetary mass companion to the lens star.
Crucial roles in the discovery were played by OGLE team leader Andrzej
Udalski of Warsaw University Observatory and graduate students Deokkeun An
of Ohio State and Ai-ying Zhou of Missouri State University. Udalski
noticed that this microlensing event was reaching a very high
magnification on May 1, and he quickly alerted the MicroFUN group to this
fact, since high magnification events are known to be very favorable for
planet detection. MicroFUN's regular telescopes were unable to get many
images, so MicroFUN leader Gould called the MDM Observatory in Arizona
where An and Zhou were observing. Gould asked An and Zhou to obtain a few
measurements of the star's brightness over the course of the night, but
instead An and Zhou made more than 1000 measurements. This large number of
MDM measurements was crucial for the determination the observed signal
must really be due to a planet.
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.
Note to editors:
High-resolution artwork to accompany this release is available online at
http://www.cfa.harvard.edu/press/pr0614image.html
*****
Research Communications
Ohio State University
Contact:
Andrew Gould, (614) 292-1892
Written by:
Pam Frost Gorder, (614) 292-9475
3/13/2006
New planet found: Icy 'super-Earth' dominates distant solar system
COLUMBUS , Ohio -- An international collaboration of astronomers has
discovered a "super-Earth" orbiting in the cold outer regions of a distant
solar system about 9,000 light-years away. The planet weighs 13 times as
much as Earth, and at -330 degrees Fahrenheit, it's one of the coldest
planets ever discovered outside our solar system.
Andrew Gould, leader of the MicroFUN collaboration and professor of
astronomy at Ohio State University, pointed to two key implications of the
discovery. "First," Gould said, "this icy super-Earth dominates the region
around its star that in our solar system is populated by the gas-giant
planets, Jupiter and Saturn. We've never seen a system like this before,
because we've never had the means to find them."
"And second," he added, "these icy super-Earths are pretty common. Roughly
35 percent of all stars have them."
The astronomers have submitted a paper on the planet to Astrophysical
Journal Letters, and posted a copy on the Internet preprint server
arXiv.org.
MicroFUN searches for planets using a phenomenon called gravitational
microlensing, which occurs when a massive object such as a star crosses in
front of another star shining in the background. The object's strong
gravity bends the light rays from the more distant star and magnifies them
like a lens. Here on Earth, we see the magnified star get brighter as the
lens star crosses in front of it, and then fade as the lens gets farther
away.
The OGLE (Optical Gravitational Lensing Experiment) collaboration
initially discovered the microlensed star in April 2005. Piecing together
their observations, Gould and OGLE leader Andrzej Udalski of Warsaw
University Observatory suddenly realized on May 1 that the star was
brightening extremely quickly, meaning that it would be exceptionally
fertile ground for planet hunting. "It was 4:00 a.m.," Gould said. "I was
very excited and frantic to get someone to observe that star."
So Gould called the MDM Observatory in Arizona, where the astronomer on
duty happened to be Ohio State graduate student Deokkeun An.
Gould asked An to spare a few minutes during his night's work to
occasionally measure the star's brightness. But when An and his
co-observer Ai-ying Zhou of Missouri State University heard how intense
the signal was, they decided to put aside their own project to take more
than 1,000 measurements of the event.
"It's a good thing that they did -- their observations turned out to be
critical to our determination that there was a planet," Gould said.
"I thought this was a good chance to take many images of the event, to
erase any doubt as to whether this was a planet signal," An remembered.
"Since the target could only be seen through the telescope during a short
time window, we did not hesitate to follow it."
The event was also observed by astronomers in New Zealand and Hawaii.
But after the astronomers gathered all the data, they faced more
difficulties. There remained a chance that the tiny warping they saw in
the signal wasn't caused by a planet, and Ohio State graduate student Subo
Dong had to write special software to speed their computer models to weed
out the other possibilities.
Finally, the models confirmed the presence of a Neptune-mass planet, 13
times heavier than Earth, orbiting a star about half as big as our sun.
Gould suspects that the planet is a bare, icy terrestrial one -- a cold
super-Earth. Judging from the absence of Jupiter-like planets in its
vicinity, that solar system may lack the gas necessary to make gas
planets, he said.
"We can't really tell for sure," he admitted. "If we start getting more
statistics on this type of planet, we could piece together a better
story."
Until a decade ago, scientists had no evidence of what other solar systems
were like. Since then, some 170 planets have been discovered, and most of
them have been gas giants similar to Jupiter.
Only a handful of Neptune-mass planets have ever been detected, and only
two in the cold outer regions of their solar systems. "The next step is to
push the sensitivity of our detection methods down to reach Earth-mass
planets," Gould said, "and microlensing is the best way to get there."
The technique is the only one sensitive enough to detect these types of
planets, he added. To increase the chance of finding planets like Earth,
he would like to see a new generation of telescopes dedicated to
microlensing planet searches.
Gould's work was supported by the National Science Foundation and NASA.
Harvard-Smithsonian Center for Astrophysics
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
For Release: Embargoed until 8:00 p.m. EST, Monday, March 13, 2006
Release No.: 06-14
Super-Earths May Be Three Times More Common Than Jupiters
Cambridge, MA -- Astronomers have discovered a new "super-Earth" orbiting
a red dwarf star located about 9,000 light-years away. This newfound world
weighs about 13 times the mass of the Earth and is probably a mixture of
rock and ice, with a diameter several times that of Earth. It orbits its
star at about the distance of the asteroid belt in our solar system, 250
million miles out. Its distant location chills it to -330 degrees
Fahrenheit, suggesting that although this world is similar in structure to
the Earth, it is too cold for liquid water or life.
Orbiting almost as far out as Jupiter does in our solar system, this
"super-Earth" likely never accumulated enough gas to grow to giant
proportions. Instead, the disk of material from which it formed
dissipated, starving it of the raw materials it needed to thrive.
"This is a solar system that ran out of gas," says Harvard astronomer
Scott Gaudi of the Harvard-Smithsonian Center for Astrophysics (CfA), a
member of the MicroFUN collaboration that spotted the planet.
The discovery is being reported today in a paper posted online at
http://arxiv.org/abs/astro-ph/0603276
and submitted to The Astrophysical Journal Letters for publication.
Gaudi performed extensive data analysis that confirmed the existence of
the planet. Further analysis simultaneously ruled out the presence of any
Jupiter-sized world in the distant solar system.
"This icy super-Earth dominates the region around its star that, in our
solar system, is populated by the gas giant planets," said first author
Andrew Gould (Ohio State University), who leads MicroFUN.
The team also calculates that about one-third of all main sequence stars
may have similar icy super-Earths. Theory predicts that smaller planets
should be easier to form than larger ones around low-mass stars. Since
most Milky Way stars are red dwarfs, solar systems dominated by
super-Earths may be more common in the Galaxy than those with giant
Jupiters.
This discovery sheds new light on the process of solar system formation.
Material orbiting a low-mass star accumulates into planets gradually,
leaving more time for the gas in the protoplanetary disk to dissipate
before large planets have formed. Low-mass stars also tend to have less
massive disks, offering fewer raw materials for planet formation.
"Our discovery suggests that different types of solar systems form around
different types of stars," explains Gaudi. "Sun-like stars form Jupiters,
while red dwarf stars only form super-Earths. Larger A-type stars may even
form brown dwarfs in their disks."
Astronomers found the planet using a technique called microlensing, an
Einsteinian effect in which the gravity of a foreground star magnifies the
light of a more distant star. If the foreground star possesses a planet,
the planet's gravity can distort the light further, thereby signaling its
presence. The precise alignment required for the effect means that each
microlensing event lasts for only a brief time. Astronomers must monitor
many stars closely to detect such events.
Microlensing is sensitive to less massive planets than the more common
planet-finding methods of radial velocity and transit searches.
"Microlensing is the only way to detect Earth-mass planets from the ground
with current technology," says Gaudi. "If there had been an Earth-mass
planet in the same region as this super-Earth, and if the alignment had
been just right, we could have detected it. By adding one more two-meter
telescope to our arsenal, we may be able to find up to a dozen Earth-mass
planets every year."
The OGLE (Optical Gravitational Lensing Experiment) collaboration
initially discovered the microlensed star in April 2005 while peering in
the direction of the galactic center, where both foreground and background
stars are widespread. OGLE identifies several hundred microlensing events
per year, however only a small fraction of those events yield planets.
Gaudi estimates that with one or two additional telescopes located in the
southern hemisphere to monitor the galactic center, the planet count could
jump drastically.
The discovery was made by 36 astronomers, including members of the
MicroFUN, OGLE, and Robonet collaborations. The name of the planet is
OGLE-2005-BLG-169Lb. OGLE-2005-BLG-169 refers to the 169th microlensing
event discovered by the OGLE Collaboration toward the Galactic bulge in
2005, and "Lb" refers to a planetary mass companion to the lens star.
Crucial roles in the discovery were played by OGLE team leader Andrzej
Udalski of Warsaw University Observatory and graduate students Deokkeun An
of Ohio State and Ai-ying Zhou of Missouri State University. Udalski
noticed that this microlensing event was reaching a very high
magnification on May 1, and he quickly alerted the MicroFUN group to this
fact, since high magnification events are known to be very favorable for
planet detection. MicroFUN's regular telescopes were unable to get many
images, so MicroFUN leader Gould called the MDM Observatory in Arizona
where An and Zhou were observing. Gould asked An and Zhou to obtain a few
measurements of the star's brightness over the course of the night, but
instead An and Zhou made more than 1000 measurements. This large number of
MDM measurements was crucial for the determination the observed signal
must really be due to a planet.
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.
Note to editors:
High-resolution artwork to accompany this release is available online at
http://www.cfa.harvard.edu/press/pr0614image.html
*****
Research Communications
Ohio State University
Contact:
Andrew Gould, (614) 292-1892
Written by:
Pam Frost Gorder, (614) 292-9475
3/13/2006
New planet found: Icy 'super-Earth' dominates distant solar system
COLUMBUS , Ohio -- An international collaboration of astronomers has
discovered a "super-Earth" orbiting in the cold outer regions of a distant
solar system about 9,000 light-years away. The planet weighs 13 times as
much as Earth, and at -330 degrees Fahrenheit, it's one of the coldest
planets ever discovered outside our solar system.
Andrew Gould, leader of the MicroFUN collaboration and professor of
astronomy at Ohio State University, pointed to two key implications of the
discovery. "First," Gould said, "this icy super-Earth dominates the region
around its star that in our solar system is populated by the gas-giant
planets, Jupiter and Saturn. We've never seen a system like this before,
because we've never had the means to find them."
"And second," he added, "these icy super-Earths are pretty common. Roughly
35 percent of all stars have them."
The astronomers have submitted a paper on the planet to Astrophysical
Journal Letters, and posted a copy on the Internet preprint server
arXiv.org.
MicroFUN searches for planets using a phenomenon called gravitational
microlensing, which occurs when a massive object such as a star crosses in
front of another star shining in the background. The object's strong
gravity bends the light rays from the more distant star and magnifies them
like a lens. Here on Earth, we see the magnified star get brighter as the
lens star crosses in front of it, and then fade as the lens gets farther
away.
The OGLE (Optical Gravitational Lensing Experiment) collaboration
initially discovered the microlensed star in April 2005. Piecing together
their observations, Gould and OGLE leader Andrzej Udalski of Warsaw
University Observatory suddenly realized on May 1 that the star was
brightening extremely quickly, meaning that it would be exceptionally
fertile ground for planet hunting. "It was 4:00 a.m.," Gould said. "I was
very excited and frantic to get someone to observe that star."
So Gould called the MDM Observatory in Arizona, where the astronomer on
duty happened to be Ohio State graduate student Deokkeun An.
Gould asked An to spare a few minutes during his night's work to
occasionally measure the star's brightness. But when An and his
co-observer Ai-ying Zhou of Missouri State University heard how intense
the signal was, they decided to put aside their own project to take more
than 1,000 measurements of the event.
"It's a good thing that they did -- their observations turned out to be
critical to our determination that there was a planet," Gould said.
"I thought this was a good chance to take many images of the event, to
erase any doubt as to whether this was a planet signal," An remembered.
"Since the target could only be seen through the telescope during a short
time window, we did not hesitate to follow it."
The event was also observed by astronomers in New Zealand and Hawaii.
But after the astronomers gathered all the data, they faced more
difficulties. There remained a chance that the tiny warping they saw in
the signal wasn't caused by a planet, and Ohio State graduate student Subo
Dong had to write special software to speed their computer models to weed
out the other possibilities.
Finally, the models confirmed the presence of a Neptune-mass planet, 13
times heavier than Earth, orbiting a star about half as big as our sun.
Gould suspects that the planet is a bare, icy terrestrial one -- a cold
super-Earth. Judging from the absence of Jupiter-like planets in its
vicinity, that solar system may lack the gas necessary to make gas
planets, he said.
"We can't really tell for sure," he admitted. "If we start getting more
statistics on this type of planet, we could piece together a better
story."
Until a decade ago, scientists had no evidence of what other solar systems
were like. Since then, some 170 planets have been discovered, and most of
them have been gas giants similar to Jupiter.
Only a handful of Neptune-mass planets have ever been detected, and only
two in the cold outer regions of their solar systems. "The next step is to
push the sensitivity of our detection methods down to reach Earth-mass
planets," Gould said, "and microlensing is the best way to get there."
The technique is the only one sensitive enough to detect these types of
planets, he added. To increase the chance of finding planets like Earth,
he would like to see a new generation of telescopes dedicated to
microlensing planet searches.
Gould's work was supported by the National Science Foundation and NASA.