Stellar Vista Observatory Sky Report: Feb. 15-21

Stock image, St. George News

SOUTHERN UTAH — The Sky Report is presented as a public service by the Stellar Vista Observatory, a nonprofit organization based in Kanab, Utah, which provides opportunities for people to observe, appreciate and comprehend our starry night sky. Additional information is available online. Send questions and comments to [email protected].

The moon passing in front of the star cluster M35 on the morning of Feb. 22, 2021 | Graphic created with courtesy of Stellar Vista Observatory, St. George News

This will be true for some time: Mars is the one planet in the evening sky (not counting Uranus, which is nearby), and it’s high in the southwest at sunset. Mars is 11 light minutes away, which means that the light of Mars we see now left Mars 11 minutes ago. This is true of radio waves too, which travel at the speed of light. If you were to text “hello” to Mars, your text would arrive 11 minutes later. This distance in miles is 125 million, or 500 times the distance to our moon.

Our moon, by the way, is just 4 degrees below Mars on Thursday evening, and both will comfortably fit in the field of view of binoculars.

Monday and Tuesday are good nights to see the thin crescent moon low in the west after sunset. Especially look for “the old moon in the young moon’s arms” – the dark part of the moon that is lit by light reflected up from Earth. To us, the moon is a thin crescent, but to whoever is on the moon at this time, Earth is nearly full and enormously bright in the lunar sky. Just as the full moon lights Earth, so too the full Earth lights the moon, and the part lit by Earthshine is easy to see. With binoculars, you can even make out the lunar seas.

If you have binoculars or a small telescope and you’re up late (or very early), watch the moon move in front of the bright star cluster M35 in the constellation Gemini the Twins. M35 is a cluster of around 120 stars that were born together about 100 million years ago and remain as a small group that is easily visible in binoculars – and even to the unaided eye from a dark location.

The moon begins to move in front of the cluster at 2 a.m. MST on Feb. 22 and completely covers it an hour later. During that hour, the dark leading edge of the moon covers, or occults, the cluster’s stars one by one. The moon seldom moves in front of a star cluster, so this is a rare and unusual sight. The stars of the cluster, by the way, are about 3,000 light years from Earth. The moon is 1¼ light seconds distant.

Thinking of star clusters, the first-quarter moon lies halfway between the two brightest and best-known on Friday night – the Pleiades, or Seven Sisters, and the Hyades, which forms the face of Taurus the Bull. Wide-angle binoculars will show the moon and either cluster at the same time. The Pleiades is compact so it’s especially pretty, while the Hyades is closer and more spread-out. The bright orange star Aldebaran, the eye of the bull, looks like it is in the Hyades but is actually in the foreground and the cluster is a hundred light years beyond.

Written by JOHN MOSLEY. John Mosley was program supervisor of the Griffith Observatory in Los Angeles for 27 years and is the author of “Stargazing for Beginners” and “Stargazing with Binoculars and Telescopes”. He and his wife live in St. George where he continues to stargaze from his retirement home while serving on the advisory committee for Stellar Vista Observatory.

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