July 20th 05, 06:50 PM
http://web.mit.edu/newsoffice/2005/charon.html
MIT-Williams team catches rare light show
MIT
July 20, 2005
On a clear summer night, the stars aligned for MIT researchers watching
and waiting for one small light in the heavens to be extinguished, just
briefly.
Thanks to a feat of both astronomical and terrestrial alignment, a
group
of scientists from MIT and Williams College succeeded in observing
distant Pluto's tiny moon, Charon, hide a star. Such an event had been
seen only once before, by a single telescope 25 years ago, and then not
nearly as well.
The MIT-Williams consortium spotted it with four telescopes in Chile on
the night of July 10-11.
The team expects to use data from this observation to assess whether
Charon has an atmosphere, to measure its radius and to determine how
round it is.
The data and results from the observation will be presented at the 2005
meeting of the American Astronomical Society's Division of Planetary
Sciences meeting to be held in Cambridge, England, in September.
MIT team leader James L. Elliot headed the group at the Clay Telescope
at Las Campanas Observatory in Chile.
"We have been waiting many years for this opportunity. Watching Charon
approach the star and then snuff it out was spectacular," said Elliot,
a
professor in the Department of Earth, Atmospheric and Planetary Science
and the Department of Physics at MIT in Cambridge, Mass.
Jay M. Pasachoff, team leader from Williams College in Williamstown,
Mass., and a professor in that school's Department of Astronomy, said,
"It's amazing that people in our group could get in the right place at
the right time to line up a tiny body 4 billion miles away. It's quite
a
reward for so many people who worked so hard to arrange and integrate
the equipment and to get the observations."
With the Clay Telescope's 6.5-meter mirror (more than 21 feet across,
the size of a large room) the researchers were able to observe changes
throughout the event, which lasted less than a minute. While their
electronic cameras sensitively recorded data, the light of the faint
star was seen to dim and then, some seconds later, brighten. This kind
of disappearance of a celestial body behind a closer, apparently larger
one is known as an occultation.
Studying how the light dimmed and brightened will let the MIT-Williams
consortium look for signs that Charon has an atmosphere. It has very
little mass and thus little gravity to hold in an atmosphere, but it is
so cold (being some 40 times farther from the sun than the Earth) that
some gases could be held in place by the small amount of Charon's
gravity.
Other telescopes around Chile used by the MIT-Williams consortium
included the 8-meter (more than 26 feet across) Gemini South on Cerro
Pachon, the 2.5-meter (more than 8 feet across) DuPont Telescope at Las
Campanas Observatory and the 0.8-meter (almost 3 feet across) telescope
at the Cerro Armazones Observatory of Chile's Catholic University of
the
North near Cerro Paranal.
The team had searched for a distribution of telescopes along a
north-south line in Chile since the predictions of the starlight shadow
of Charon were uncertain by several hundred kilometers. Since the star
that was hidden is so far away, it casts a shadow of Charon that is the
same size as Charon itself, about 1,200 kilometers in diameter. To see
the event, the distant star, Charon and the telescopes in Chile had to
be perfectly aligned. All of these telescopes had clear views of the
event.
Other MIT affiliates involved in the observation were MIT graduate
students Elisabeth Adams, Michael Person and Susan Kern and
postdoctoral
associate Amanda Gulbis.
The images from three telescopes in Chile, including the Clay
Telescope,
and one in Brazil, were taken with new electronic cameras and computer
control obtained by MIT and Williams with an equipment grant from NASA.
The expeditions were sponsored by NASA's Planetary Astronomy Program.
A video showing the star dimming as Charon passes in front of it and
then brightening again is posted on the Web at
http://occult.mit.edu/research/occultations/Charon/C313.2/C313OccMovie.html
..
Teams from the Observatory of Paris at Meudon and from the Southwest
Research Institute in Boulder, Colo., also observed the occultation.
MIT-Williams team catches rare light show
MIT
July 20, 2005
On a clear summer night, the stars aligned for MIT researchers watching
and waiting for one small light in the heavens to be extinguished, just
briefly.
Thanks to a feat of both astronomical and terrestrial alignment, a
group
of scientists from MIT and Williams College succeeded in observing
distant Pluto's tiny moon, Charon, hide a star. Such an event had been
seen only once before, by a single telescope 25 years ago, and then not
nearly as well.
The MIT-Williams consortium spotted it with four telescopes in Chile on
the night of July 10-11.
The team expects to use data from this observation to assess whether
Charon has an atmosphere, to measure its radius and to determine how
round it is.
The data and results from the observation will be presented at the 2005
meeting of the American Astronomical Society's Division of Planetary
Sciences meeting to be held in Cambridge, England, in September.
MIT team leader James L. Elliot headed the group at the Clay Telescope
at Las Campanas Observatory in Chile.
"We have been waiting many years for this opportunity. Watching Charon
approach the star and then snuff it out was spectacular," said Elliot,
a
professor in the Department of Earth, Atmospheric and Planetary Science
and the Department of Physics at MIT in Cambridge, Mass.
Jay M. Pasachoff, team leader from Williams College in Williamstown,
Mass., and a professor in that school's Department of Astronomy, said,
"It's amazing that people in our group could get in the right place at
the right time to line up a tiny body 4 billion miles away. It's quite
a
reward for so many people who worked so hard to arrange and integrate
the equipment and to get the observations."
With the Clay Telescope's 6.5-meter mirror (more than 21 feet across,
the size of a large room) the researchers were able to observe changes
throughout the event, which lasted less than a minute. While their
electronic cameras sensitively recorded data, the light of the faint
star was seen to dim and then, some seconds later, brighten. This kind
of disappearance of a celestial body behind a closer, apparently larger
one is known as an occultation.
Studying how the light dimmed and brightened will let the MIT-Williams
consortium look for signs that Charon has an atmosphere. It has very
little mass and thus little gravity to hold in an atmosphere, but it is
so cold (being some 40 times farther from the sun than the Earth) that
some gases could be held in place by the small amount of Charon's
gravity.
Other telescopes around Chile used by the MIT-Williams consortium
included the 8-meter (more than 26 feet across) Gemini South on Cerro
Pachon, the 2.5-meter (more than 8 feet across) DuPont Telescope at Las
Campanas Observatory and the 0.8-meter (almost 3 feet across) telescope
at the Cerro Armazones Observatory of Chile's Catholic University of
the
North near Cerro Paranal.
The team had searched for a distribution of telescopes along a
north-south line in Chile since the predictions of the starlight shadow
of Charon were uncertain by several hundred kilometers. Since the star
that was hidden is so far away, it casts a shadow of Charon that is the
same size as Charon itself, about 1,200 kilometers in diameter. To see
the event, the distant star, Charon and the telescopes in Chile had to
be perfectly aligned. All of these telescopes had clear views of the
event.
Other MIT affiliates involved in the observation were MIT graduate
students Elisabeth Adams, Michael Person and Susan Kern and
postdoctoral
associate Amanda Gulbis.
The images from three telescopes in Chile, including the Clay
Telescope,
and one in Brazil, were taken with new electronic cameras and computer
control obtained by MIT and Williams with an equipment grant from NASA.
The expeditions were sponsored by NASA's Planetary Astronomy Program.
A video showing the star dimming as Charon passes in front of it and
then brightening again is posted on the Web at
http://occult.mit.edu/research/occultations/Charon/C313.2/C313OccMovie.html
..
Teams from the Observatory of Paris at Meudon and from the Southwest
Research Institute in Boulder, Colo., also observed the occultation.