Skywatch Line for Monday and Tuesday, June 18th and 19th, 2018

This is the Skywatch Line for Monday and Tuesday, June 18th and 19th.

The Sun sets at 8:36 PM; night falls at 10:53. Dawn begins at 3 AM and ends with the Sun rising at 5:16.

The 6-day-old Moon dominates the evening sky. Blazing with minus 9th magnitude, the 35% crescent occupies Leo. Tuesday’s Moon is brighter and fuller and migrates to Virgo. The Moon sets at 12:39 AM on Tuesday, and at 1:12 AM on Wednesday. The Moon is officially First Quarter at 6:51 AM on Wednesday.

Mercury makes its appearance, a low 1º in the western sky. It shines with minus 1st magnitude, appears about 5 arc-seconds in size and displays an 83% crescent. Mercury sets at 9:47 PM.

Venus, 23º to Mercury’s left, blazes with minus 4th magnitude in Cancer. It is about 20º high, about 15 arc-seconds in size and sports a 75% crescent. Venus lies about 1º from M-44, The Beehive star cluster, a great binocular object for beginners. Venus sets at 11:07 PM.

Jupiter, in Libra, lies 31º high in the southern sky. It blazes with minus 2nd magnitude. The largest planet continues to hug close to Alpha Librae, also called Zubenelgenubi. Telescopic observers can see the Great Red Spot (a giant storm) centered at 2:02 AM on Wednesday. Jupiter is best observed at 9:54 PM and sets at 3:03 AM.

Saturn rises at 9 PM in Sagittarius, shines at zero magnitude and appears about 18 arc-seconds in size. By nightfall, it lies about 15º high and is best observed at 1:38 AM.

Asteroid 4Vesta lies about 7º to Saturn’s upper right and close to open star cluster M23 – another great binocular view. Tuesday, the brightest asteroid reaches Opposition, when it lines up with Earth and the Sun. It is also historically close, only 170 million kilometers (105 million miles). At magnitude 5.3, Vesta is actually visible to the naked eye under dark skies. The best window for observation in moonless skies is from June 8th – 22nd. Vesta will look like a star which moves a bit westward nightly. Vesta has baffled astronomers. While the Moon reflects only 12% of its sunlight, Vesta reflects 43%. The DAWN spacecraft visited Vesta and found that its surface is not weathered, which accounts for its brilliance. 4Vesta is best observed at 1:06 AM and sets at 5:51 AM.

Mars rises at 11:20 PM in Capricornus. It shines with minus 2nd magnitude, appears 18 arc-seconds in size and is about 94% illuminated. Telescopic observers can see a giant dust storm that has covered a quarter of the planet; it has silenced the rover Opportunity by coating the solar panels that charge the rover’s batteries. Mars continues to brighten and appear larger in preparation for its own Opposition in July. It is best observed at 3:58 AM.

Neptune rises in Aquarius at 12:41 AM, near the star Phi Aquarii. It glows with 8th magnitude and appears a tiny 2 arc-seconds in size but has a distinctive blue-green tint. By Dawn, it is about 23º high. Uranus follows by rising in Aries at 2:21 AM, is brighter and slightly larger than Neptune, but only 6º high by Dawn. Both require detailed star charts available from astronomy websites and magazines.

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