NASA's Deep Impact Begins Hunt for Alien Worlds
- From: baalke@xxxxxxxxxxxxx
- Date: Thu, 7 Feb 2008 18:04:22 -0800 (PST)
http://www.jpl.nasa.gov/news/news.cfm?release=2008-021
NASA's Deep Impact Begins Hunt for Alien Worlds
Jet Propulsion Laboratory
February 07, 2008
NASA's Deep Impact spacecraft is aiming its largest telescope at five
stars in a search for alien (exosolar) planets as it enters its
extended
mission, called Epoxi.
Deep Impact made history when the mission team directed an impactor
from
the spacecraft into comet Tempel 1 on July 4, 2005. NASA recently
extended the mission, redirecting the spacecraft for a flyby of comet
Hartley 2 on Oct. 11, 2010.
As it cruises toward the comet, Deep Impact will observe five nearby
stars with "transiting exosolar planets," so named because the planet
transits, or passes in front of, its star. The Epoxi team, led by
University of Maryland astronomer Michael A'Hearn, directed the
spacecraft to begin these observations Jan. 22. The planets were
discovered earlier and are giant planets with massive atmospheres,
like
Jupiter in our solar system. They orbit their stars much closer than
Earth does the sun, so they are hot and belong to the class of
exosolar
planets nicknamed "Hot Jupiters."
However, these giant planets may not be alone. If there are other
worlds
around these stars, they might also transit the star and be discovered
by the spacecraft. Deep Impact can even find planets that don't
transit,
using a timing technique. Gravity from the unseen planets will pull on
the transiting planets, altering their orbits and the timing of their
transits.
"We're on the hunt for planets down to the size of Earth, orbiting
some
of our closest neighboring stars," said Epoxi Deputy Principal
Investigator Drake Deming of NASA's Goddard Space Flight Center in
Greenbelt, Md. Epoxi is a combination of the names for the two
extended
mission components: the exosolar planet observations, called
Extrasolar
Planet Observations and Characterization (Epoch), and the flyby of
comet
Hartley 2, called the Deep Impact Extended Investigation (Dixi).
Goddard
leads the Epoch component.
More than 200 exosolar planets have been discovered to date. Most of
these are detected indirectly, by the gravitational pull they exert on
their parent star. Directly observing exosolar planets by detecting
the
light reflected from them is very difficult, because a star's
brilliance
obscures light coming from any planets orbiting it.
However, sometimes the orbit of an exosolar world is aligned so that
it
eclipses its star as seen from Earth. In these rare cases, called
transits, light from that planet can be seen directly.
"When the planet appears next to its star, your telescope captures
their
combined light. When the planet passes behind its star, your telescope
only sees light from the star. By subtracting light from just the star
from the combined light, you are left with light from the planet,"
said
Deming, who is leading the search for exosolar worlds with Deep
Impact.
"We can analyze this light to discover what the atmospheres of these
planets are like."
Deep Impact will also look back to observe Earth in visible and
infrared
wavelengths, allowing comparisons with future discoveries of Earth-
like
planets around other stars.
NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages Epoxi for
NASA's Science Mission Directorate, Washington. The University of
Maryland is the Principal Investigator institution. NASA Goddard leads
the mission's exosolar planet observations. The spacecraft was built
for
NASA by Ball Aerospace & Technologies Corp., Boulder, Colo.
For information about Epoxi, visit http://www.nasa.gov/epoxi . More
information about JPL is at www.jpl.nasa.gov <http://
www.jpl.nasa.gov> .
More information about NASA programs is at www.nasa.gov .
------------------------------------------------------------------------
Media contacts: DC Agle 818-393-9011
Jet Propulsion Laboratory, Pasadena, Calif.
agle@xxxxxxxxxxxx
Nancy Neal-Jones 301-286-0039
NASA Goddard Space Flight Center, Greenbelt, Md.
Nancy.N.Jones@xxxxxxxx
Lee Tune 301-405-4679
University of Maryland, College Park
ltune@xxxxxxx
.
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