Skylights featured on Astronom y Picture of the Day

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Skylights featured nine times on Earth Science Picture of the Day: 1 2 3 4 5 6 7 8 9 -- Full List Restored!

Greenland 12

Photo of the Week. Planet Earth: the ninth of twelve in the "Flight across Greenland," going from east to west above the fantastic glacier and a river of ice. See full resolution.

Astronomy news for the week starting Friday, April 4, 2014.

The Moon starts off our week as a fat waxing crescent as it heads toward its first quarter on the morning of Monday, April 7th, after moonset. The night of Sunday the 6th it will be seen just shy of the phase, the following night just past it. It then brightens in the waxing gibbous phase, full Moon not reached until Tuesday the 15th, when there will be a total eclipse visible throughout North America. Early in the week, the near-quarter Moon will play with Jupiter. The night of Saturday the 5th, the Moon will appear to the west of the giant planet, and then the evening of Sunday the 6th, the Moon will glide five degrees below Jupiter, the two making a fine sight against the stars of Gemini, which include bright Castor and Pollux. Even the evening of Monday the 7th it's worth a look to see the Moon moving off to the east of the far more slowly moving planet. The Moon reaches its apogee, the farthest point in its orbit from Earth (405,500 kilometers, 252,000 miles), on Tuesday the 8th.

Though night by night slowly shifting off to the west, Jupiter still rules the evening skies, at least until it sets just after 2 AM Daylight Time. It's really a week to celebrate Mars, however, as the red planet achieves opposition to the Sun on Tuesday the 8th, when it will rise at sunset, cross the meridian to the south at local midnight, and set at sunrise. With the Sun just east of the vernal equinox in Pisces, Mars must then be just east of the autumnal equinox in Virgo, where it is found a few degrees northwest of Spica. Since Mars's orbit is rather eccentric (by about nine percent, quite a bit more than any other planet except Mercury and Pluto, but the latter is no longer considered a planet and that's another story), closest approach to Earth (0.62 Astronomical Units, 93 million kilometers, 58 million miles) does not take place until next week, on Monday the 14th. Ah the oddities one finds. In contrast to Mars, the asteroid 3 Juno, third discovered, but with an average diameter of 240 km tenth largest (their irregularity making asteroids hard to rank in size), is in conjunction with the Sun on Thursday the 10th. Which means it's not visible at all. Saturn, though, certainly is, rising in Libra around 10 PM, an hour after twilight ends. Then just before the sky begins to lighten, near 5 AM, up comes Venus. Now in its role as "morning star," the planet's luster does not fade in southeastern skies until bright dawn.

In the evening we look now not at the Milky Way, but perpendicular to it, away from the pervasive obscuring dust of the Galaxy's disk, which allows us to see to great distances and into the swarms of other galaxies that surround us. The nearest large grouping, the Virgo Cluster of galaxies, lies "only" 55 million light years away, many of its members visible in a small telescope. Farther on, 330 million light years away, is the Coma Berenices cluster of galaxies (not to be confused with the nearby star cluster of the same name) south of the Big Dipper. Four galaxies are visible to the naked eye, in the northern hemisphere M31 in Andromeda and M33 in Triangulum (the latter just barely), and in the southern hemisphere the two Magellanic Clouds, the larger in Dorado, the smaller in Tucana.

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