Andrew Yee[_1_]
April 3rd 08, 03:24 AM
Office of News and Public Affairs
Harvard University
Cambridge, Massachusetts
April 2, 2008
Laser precision added to search for new Earths
Measuring ability leaps with new instrument
Alvin Powell, Harvard News Office
Harvard scientists have unveiled a new laser-measuring device that they say
will provide a critical advance in the resolution of current planet-finding
techniques, making the discovery of Earth-sized planets possible.
The discovery of planets outside of our solar system, called "exoplanets,"
is one of the hottest fields in astronomy and holds great promise to
increase our understanding of Earth's solar system and of how life first
took hold on this planet.
The problem, however, is that the two main techniques to find exoplanets
rely on the planet's very small effect on its star. One measures the star's
"wobble" due to the planet's gravitational pull as it circles, while the
other measures the dimming of a star's light as a planet passes in front of
it. With current technology, both of these techniques can identify
relatively large planets that have a noticeable effect on their star.
Large planets, however, tend to be gaseous giants, like our solar system's
Jupiter and Saturn, incapable of supporting life. Smaller, rocky planets,
like Earth and Mars, are thought to be the likeliest candidates for life,
but are too small to be detected by current techniques.
The new device, called an astro-comb, uses femto-second (one millionth of
one billionth of a second) pulses of laser light linked to an atomic clock
to provide a precise standard against which light from a star can be
measured. Ronald Walsworth, senior lecturer on physics in the Faculty of
Arts and Sciences, senior physicist at the Smithsonian Astrophysical
Observatory and in whose lab the astro-comb was developed, said it may
increase the resolution of the star "wobble" technique by about 100 times,
which would allow detection of a planet the size of Earth.
"The existing tools, prior to astro-comb, couldn't do the job," Walsworth
said.
Both Walsworth and Astronomy Professor Dimitar Sasselov, director of the
Harvard University Origins of Life Initiative, said that the final
resolution of astronomical observations taken using the astro-comb may be
somewhat lower than what would be ideally possible because other factors,
such as "noise" in stellar atmospheres, may affect the quality of
measurements. Still, Sasselov said, planets close to the size of Earth --
and that share enough of Earth's characteristics to harbor the conditions of
life -- should be detectable within the next few years using the astro-comb.
The ability to find and analyze Earthlike planets is an important step in
obtaining baseline information with which to understand how life on Earth
arose, said Sasselov. The Origins of Life Initiative, he said, brings
together experts from a variety of fields whose expertise is pertinent to
understanding the planetary roots of life in the universe. By studying
conditions on Earthlike planets circling other stars, he said, scientists
may be better able to understand what conditions were like on Earth before
life arose. That understanding, he said, could inform the research of
chemists and molecular biologists seeking to learn how organic chemicals
came to create the chemistry of life.
"I think this is super-exciting, from the point of view of furthering this
new field of science: the exploration of environments out of this solar
system," Sasselov said.
The astro-comb was developed in a collaboration between physicists and
astronomers working at the Harvard-Smithsonian Center for Astrophysics and
Harvard's Department of Physics and Origins of Life Initiative, as well as
Massachusetts Institute of Technology's Department of Electrical
Engineering. In particular, both Walsworth and Sasselov credited the
interdisciplinary environment of the Center for Astrophysics and the vision
of the Origins of Life Initiative for bringing together experts in diverse
fields whose work made the advance possible.
Three years ago, as a classroom exercise in a physics course he was
teaching, Walsworth began mulling ways that an existing instrument, called a
laser comb, could be used to solve the knotty problems of astrophysics. At
about the same time, Andrew Szentgyorgyi, an associate of the Harvard
College Observatory and senior astrophysicist at the Smithsonian
Astrophysical Observatory, began hearing about laser combs and was trying to
find someone knowledgeable enough about them to tell him if they could be
adapted to his astronomy research. Finally, in frustration, he went to
Walsworth's office.
"I knocked on his door and asked, 'Do you know anything about these laser
combs?' He said, 'Do I know anything? I have one,' " Szentgyorgyi said.
Laser combs have been around for a decade and are used in creating extremely
precise clocks. The combs work by creating regular spikes of laser light
that are evenly spaced in wavelength -- like the teeth of a comb -- and can
be projected onto a light-spectrum measuring device called a spectrograph.
Against such a precise background, physicists and astronomers can accurately
measure the light from various sources, including the light from stars.
Laser combs hadn't been used in astrophysics before now, however, because of
technical problems that made them too precise -- the teeth on the light
"comb" they created were too close together to be useful in measuring
starlight. Walsworth and colleagues added a filtering device that spreads
the laser comb's teeth apart by a factor of about ten, and stabilized the
system to an atomic clock, creating the first laser comb appropriate for
astrophysical research.
"Now we can tune the system and get out exactly the light out that a
particular astrophysical spectrograph needs," Walsworth said.
Though its most high-profile application will be the search for exoplanets,
the astro-comb can measure other light coming from the heavens as well. In
fact, it will get its first tryout in late spring at the Mount Hopkins
Observatory in Arizona examining stars in a nearby globular cluster to see
if their motion is affected by the theorized presence of dark matter there.
Once that trial is complete, a new astro-comb will be constructed as part of
the Harvard University Origins of Life Initiative with the aim of deploying
it at a project being built in the Canary Islands for exoplanet research,
called the New Earths Facility. Szentgyorgyi, who will head the Canary
Island team, said they will first take the astro-comb to Geneva to calibrate
it with equipment being built by European collaborators and then install it
in the Canary Islands. It will be operational sometime in 2010, he said.
IMAGE CAPTION:
[http://harvardscience.harvard.edu/files/large/040108_laser_015BIG.jpg
(228KB)]
Post Doc Chih-Hao Li and Ronald Walsworth with new laser device. Credit: Jon
Chase Photo/Harvard News Office
Harvard University
Cambridge, Massachusetts
April 2, 2008
Laser precision added to search for new Earths
Measuring ability leaps with new instrument
Alvin Powell, Harvard News Office
Harvard scientists have unveiled a new laser-measuring device that they say
will provide a critical advance in the resolution of current planet-finding
techniques, making the discovery of Earth-sized planets possible.
The discovery of planets outside of our solar system, called "exoplanets,"
is one of the hottest fields in astronomy and holds great promise to
increase our understanding of Earth's solar system and of how life first
took hold on this planet.
The problem, however, is that the two main techniques to find exoplanets
rely on the planet's very small effect on its star. One measures the star's
"wobble" due to the planet's gravitational pull as it circles, while the
other measures the dimming of a star's light as a planet passes in front of
it. With current technology, both of these techniques can identify
relatively large planets that have a noticeable effect on their star.
Large planets, however, tend to be gaseous giants, like our solar system's
Jupiter and Saturn, incapable of supporting life. Smaller, rocky planets,
like Earth and Mars, are thought to be the likeliest candidates for life,
but are too small to be detected by current techniques.
The new device, called an astro-comb, uses femto-second (one millionth of
one billionth of a second) pulses of laser light linked to an atomic clock
to provide a precise standard against which light from a star can be
measured. Ronald Walsworth, senior lecturer on physics in the Faculty of
Arts and Sciences, senior physicist at the Smithsonian Astrophysical
Observatory and in whose lab the astro-comb was developed, said it may
increase the resolution of the star "wobble" technique by about 100 times,
which would allow detection of a planet the size of Earth.
"The existing tools, prior to astro-comb, couldn't do the job," Walsworth
said.
Both Walsworth and Astronomy Professor Dimitar Sasselov, director of the
Harvard University Origins of Life Initiative, said that the final
resolution of astronomical observations taken using the astro-comb may be
somewhat lower than what would be ideally possible because other factors,
such as "noise" in stellar atmospheres, may affect the quality of
measurements. Still, Sasselov said, planets close to the size of Earth --
and that share enough of Earth's characteristics to harbor the conditions of
life -- should be detectable within the next few years using the astro-comb.
The ability to find and analyze Earthlike planets is an important step in
obtaining baseline information with which to understand how life on Earth
arose, said Sasselov. The Origins of Life Initiative, he said, brings
together experts from a variety of fields whose expertise is pertinent to
understanding the planetary roots of life in the universe. By studying
conditions on Earthlike planets circling other stars, he said, scientists
may be better able to understand what conditions were like on Earth before
life arose. That understanding, he said, could inform the research of
chemists and molecular biologists seeking to learn how organic chemicals
came to create the chemistry of life.
"I think this is super-exciting, from the point of view of furthering this
new field of science: the exploration of environments out of this solar
system," Sasselov said.
The astro-comb was developed in a collaboration between physicists and
astronomers working at the Harvard-Smithsonian Center for Astrophysics and
Harvard's Department of Physics and Origins of Life Initiative, as well as
Massachusetts Institute of Technology's Department of Electrical
Engineering. In particular, both Walsworth and Sasselov credited the
interdisciplinary environment of the Center for Astrophysics and the vision
of the Origins of Life Initiative for bringing together experts in diverse
fields whose work made the advance possible.
Three years ago, as a classroom exercise in a physics course he was
teaching, Walsworth began mulling ways that an existing instrument, called a
laser comb, could be used to solve the knotty problems of astrophysics. At
about the same time, Andrew Szentgyorgyi, an associate of the Harvard
College Observatory and senior astrophysicist at the Smithsonian
Astrophysical Observatory, began hearing about laser combs and was trying to
find someone knowledgeable enough about them to tell him if they could be
adapted to his astronomy research. Finally, in frustration, he went to
Walsworth's office.
"I knocked on his door and asked, 'Do you know anything about these laser
combs?' He said, 'Do I know anything? I have one,' " Szentgyorgyi said.
Laser combs have been around for a decade and are used in creating extremely
precise clocks. The combs work by creating regular spikes of laser light
that are evenly spaced in wavelength -- like the teeth of a comb -- and can
be projected onto a light-spectrum measuring device called a spectrograph.
Against such a precise background, physicists and astronomers can accurately
measure the light from various sources, including the light from stars.
Laser combs hadn't been used in astrophysics before now, however, because of
technical problems that made them too precise -- the teeth on the light
"comb" they created were too close together to be useful in measuring
starlight. Walsworth and colleagues added a filtering device that spreads
the laser comb's teeth apart by a factor of about ten, and stabilized the
system to an atomic clock, creating the first laser comb appropriate for
astrophysical research.
"Now we can tune the system and get out exactly the light out that a
particular astrophysical spectrograph needs," Walsworth said.
Though its most high-profile application will be the search for exoplanets,
the astro-comb can measure other light coming from the heavens as well. In
fact, it will get its first tryout in late spring at the Mount Hopkins
Observatory in Arizona examining stars in a nearby globular cluster to see
if their motion is affected by the theorized presence of dark matter there.
Once that trial is complete, a new astro-comb will be constructed as part of
the Harvard University Origins of Life Initiative with the aim of deploying
it at a project being built in the Canary Islands for exoplanet research,
called the New Earths Facility. Szentgyorgyi, who will head the Canary
Island team, said they will first take the astro-comb to Geneva to calibrate
it with equipment being built by European collaborators and then install it
in the Canary Islands. It will be operational sometime in 2010, he said.
IMAGE CAPTION:
[http://harvardscience.harvard.edu/files/large/040108_laser_015BIG.jpg
(228KB)]
Post Doc Chih-Hao Li and Ronald Walsworth with new laser device. Credit: Jon
Chase Photo/Harvard News Office