Catch Mercury Before Dawn on July 20

http://messenger.jhuapl.edu/news_room/status_report_07_18_07.html

MESSENGER Mission News
July 18, 2007

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CATCH MERCURY BEFORE DAWN ON JULY 20

Mercury's orbit is so close to the Sun that we can see it from Earth
only just before sunrise or just after sunset. The best time to
glimpse
the planet is during one of the six or so times a year when it is at
what is called "greatest elongation," referring to the angle between
the
Sun and a planet as seen from the Earth.

Mercury reaches its greatest western elongation Friday, and hosts of
the
Earth & Sky radio program will discuss this prime viewing opportunity
on
their show tomorrow, July 19. Mercury, the innermost planet and
MESSENGER's main target, will swing to its greatest distance from the
Sun Friday morning. "Even so, Mercury is rising
<http://aa.usno.navy.mil/data/docs/mrst.html> less than 1.5 hours
before
the Sun now," says Earth & Sky's writer Bruce McClure. "If you're up
for
the challenge, these July mornings present an opportunity to catch
Mercury before sunrise."

After July 20, Mercury's remaining elongation days this year are
September 29 (in the eastern sky) and November 8 (in the western sky).
Earth & Sky's radio program on the topic will be available online
tomorrow at
http://www.earthsky.org/radioshows/51376/mercury-best-before-dawn-on-july-20.

For a diagram of the orbits of the inner planets, as they appear
today,
visit the MESSENGER "Where Is Mercury Now?" site at:
http://btc.montana.edu/messenger/wheremerc/wheresmerc.php.

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MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and
Ranging) is a NASA-sponsored scientific investigation of the planet
Mercury and the first space mission designed to orbit the planet
closest
to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and
after flybys of Earth, Venus, and Mercury will start a yearlong study
of
its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie
Institution of Washington, leads the
mission as principal investigator. The Johns Hopkins University
Applied
Physics Laboratory built and operates the
MESSENGER spacecraft and manages this Discovery -class mission for
NASA.

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