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May 4, 2015 - A Glimpse of Mercury

A Glimpse of Mercury  Mercury, the innermost planet, orbits the Sun every eighty-eight days and never strays more than 70 million km (43 million mi) from it. From our perspective, Mercury is always near the Sun, and often too close for viewing. Several times each year, however, Mercury appears at one of its extreme separations, or elongations, from the Sun, and spotting it with the naked eye becomes somewhat less of a challenge. This week Mercury reaches its greatest eastern elongation, a separation of 21° from the Sun, and is visible low in the western sky at sunset, about 20° below brighter Venus. Catching a glimpse of elusive Mercury is worth the effort, but if you don’t see it you can enjoy this even closer view of Tansen, a 27 km-wide (17 mi) crater on Mercury imaged by MESSENGER in 2013.

Image credit: NASA/Johns Hopkins University Applied Physics Laboratory / Carnegie Institution of Washington

Weekly Calendar

May 4-10, 2015

Holidays - Sky Events - Space History


Monday 4

1967: Lunar Orbiter IV launched
1989: STS-30 Atlantis launched, releases Magellan spacecraft
2002: Aqua satellite launched

Tuesday 5

Cinco de Mayo

Saturn 2° south of Moon
Eta Aquarid meteor shower

1961: Freedom 7 suborbital flight; Alan Shepard is first American in space

Wednesday 6

Eta Aquarid meteor shower

1968: Neil Armstrong ejects safely from Lunar Landing Research Vehicle before it crashes
1975: NASA announces that Canada will build the Shuttle robot arm

Thursday 7

Mercury at greatest elongation (21° E)

1992: STS-49 Endeavour launched

Friday 8

Saturday 9

2003: Hayabusa launched, first mission to retrieve a sample from an asteroid

Sunday 10

Mother's Day

1967: M2-F2 lifting body crash-lands; footage later becomes opening scene of “The Six Million Dollar Man”

Suggestions for new history dates or better links? Corrections for errors on this page? Please e-mail me.