Andrew Yee[_1_]
April 24th 08, 06:14 PM
Office of Public Information
Penn State
University Park, Pennsylvania
Contacts:
Andrea Messer, 814-865-9481
Vicki Fong, 814-865-9481
Thursday, April 24, 2008
Plan to identify watery earth-like planets develops
Erie, Pa. -- Astronomers are looking to identify Earth-like watery worlds
circling distant stars from a glint of light seen through an optical space
telescope and a mathematical method developed by researchers at Penn State
and the University of Hawaii.
"We are looking for Earth-like planets in the habitable zone of their star,
a band not too hot nor too cold for life to exist," says Darren M. Williams,
associate professor of physics and astronomy, Penn State Erie, the Behrend
College. "We also want to know if there is water on these planets."
For life to exist, planets must have habitable temperatures throughout a
period long enough for life to evolve. For life as we know it, the planet
must have a significant amount of water. Scientists already know how to
determine the distance a planet orbits from its star, and analysis of light
interacting with molecules in the atmosphere can indicate if water exists.
However, Williams and Eric Gaidos, associate professor of geobiology,
University of Hawaii, want to identify planets with water on their surfaces.
The researchers' method, reported in an upcoming issue of Icarus and
currently available online, relies on the reflective properties of water.
"A planet like Venus, with a dense atmosphere, will scatter the sunlight in
all directions," Williams says. "If you look at Venus in phases, when it is
full, it is brightest and when it is crescent, it is faintest."
When a planet is full in respect to its sun with the whole disk illuminated,
water would actually be darker than dirt. However, when a planet is in
crescent, with the sun glancing off the watery surface, the reflection will
be brightest.
The image of the Blue Marble, taken by Apollo 17 in December 1972, is
striking because the Earth is 70 percent covered in water. The researchers
believe that large enough amounts of water will provide a glint of light
visible in the infrared and visible spectrum if they watch the planet for
long enough.
"We are going to look at the planets for a long time," says Williams. "They
reflect one billionth or one ten billionth of their sun. To gain enough
light to see a dot requires observation over two weeks with the kinds of
telescopes we are imagining. If we stare that long, unless the planet is
rotating very slowly, different sides of the planet will come through our
field of view. If the planet is a mix of water, we are going to see the mix
travel around the planet."
The researchers want to monitor the light curve of a distant planet as the
planet spins on its axis and moves around its star. By looking at the
changes in brightness, correlated to the planet's phase, they should be able
to tell if the planet has liquid oceans. If the temperatures are correct,
the liquid is probably water.
While there are currently no telescopes capable of identifying watery
planets, astronomers hope that a terrestrial planet finder telescope will
orbit the earth in the next 10 to 20 years. In the meantime, the Penn State
researcher has arranged for the current Mars Express and Venus Express
missions of the European Space Agency, to look back at the Earth
occasionally from a great distance and observe what our watery planet looks
like in various phases.
"Any time that the Earth is in a crescent phase as viewed by a distant space
vehicle, we should take advantage of the situation and look back at the
Earth," says Williams.
Penn State
University Park, Pennsylvania
Contacts:
Andrea Messer, 814-865-9481
Vicki Fong, 814-865-9481
Thursday, April 24, 2008
Plan to identify watery earth-like planets develops
Erie, Pa. -- Astronomers are looking to identify Earth-like watery worlds
circling distant stars from a glint of light seen through an optical space
telescope and a mathematical method developed by researchers at Penn State
and the University of Hawaii.
"We are looking for Earth-like planets in the habitable zone of their star,
a band not too hot nor too cold for life to exist," says Darren M. Williams,
associate professor of physics and astronomy, Penn State Erie, the Behrend
College. "We also want to know if there is water on these planets."
For life to exist, planets must have habitable temperatures throughout a
period long enough for life to evolve. For life as we know it, the planet
must have a significant amount of water. Scientists already know how to
determine the distance a planet orbits from its star, and analysis of light
interacting with molecules in the atmosphere can indicate if water exists.
However, Williams and Eric Gaidos, associate professor of geobiology,
University of Hawaii, want to identify planets with water on their surfaces.
The researchers' method, reported in an upcoming issue of Icarus and
currently available online, relies on the reflective properties of water.
"A planet like Venus, with a dense atmosphere, will scatter the sunlight in
all directions," Williams says. "If you look at Venus in phases, when it is
full, it is brightest and when it is crescent, it is faintest."
When a planet is full in respect to its sun with the whole disk illuminated,
water would actually be darker than dirt. However, when a planet is in
crescent, with the sun glancing off the watery surface, the reflection will
be brightest.
The image of the Blue Marble, taken by Apollo 17 in December 1972, is
striking because the Earth is 70 percent covered in water. The researchers
believe that large enough amounts of water will provide a glint of light
visible in the infrared and visible spectrum if they watch the planet for
long enough.
"We are going to look at the planets for a long time," says Williams. "They
reflect one billionth or one ten billionth of their sun. To gain enough
light to see a dot requires observation over two weeks with the kinds of
telescopes we are imagining. If we stare that long, unless the planet is
rotating very slowly, different sides of the planet will come through our
field of view. If the planet is a mix of water, we are going to see the mix
travel around the planet."
The researchers want to monitor the light curve of a distant planet as the
planet spins on its axis and moves around its star. By looking at the
changes in brightness, correlated to the planet's phase, they should be able
to tell if the planet has liquid oceans. If the temperatures are correct,
the liquid is probably water.
While there are currently no telescopes capable of identifying watery
planets, astronomers hope that a terrestrial planet finder telescope will
orbit the earth in the next 10 to 20 years. In the meantime, the Penn State
researcher has arranged for the current Mars Express and Venus Express
missions of the European Space Agency, to look back at the Earth
occasionally from a great distance and observe what our watery planet looks
like in various phases.
"Any time that the Earth is in a crescent phase as viewed by a distant space
vehicle, we should take advantage of the situation and look back at the
Earth," says Williams.