Stellar Vista Observatory Sky Report: Feb. 22-28

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].

Castor and Pollux shine in the night sky | Image courtesy of Stellar Vista Observatory, St. George News

Only two months ago we enjoyed the remarkable sight of Jupiter and Saturn sitting extremely close together in the evening sky, and then Mercury made a great appearance when it was easy to see. These three planets then moved close to the sun, but they’re back – now on the other side of the sun in the morning sky. Theoretically you can see all three in morning twilight if you have a low eastern horizon and binoculars, although in practice they are so low that it will be tough to see them against the brightening sky. Remember that you can easily generate a simple chart of the sky, planets included, at Heavens-Above.

Far easier to spot is Mars, which remains a bright orange “star” high in the southwest as darkness falls. It’s in the news as a fleet of spacecraft launched last summer arrive to go into orbit and land to begin their studies.

The moon is just below Castor and Pollux, the two brightest stars in Gemini, the twins, on Tuesday evening. Castor, the topmost of the two, is an especially interesting star. It’s not just one star but six. The sun is a single star with planets (plus assorted asteroids and comets) for companions, but Castor is six stars orbiting around each other and a common center of gravity.

Point a typical amateur telescope at Castor and you’ll see two stars of nearly equal brightness that are almost touching (their separation is 6 arcseconds or 0.0017 degrees). Each is a bit larger and brighter than our sun and the distance between them is 100 times the distance between the Earth and sun, and they take about 460 years to complete one orbit. What you won’t see are much fainter dwarf stars which orbit ultra-close to each, making four. You could search for yet another pair of dwarf stars that appear as one faint star some distance away (73 arcseconds; magnitude 9) and that take thousands of years to orbit the main group.

Castor is 51 light-years away, so the light we see tonight left it in 1970, when Nixon was President. Its twin Pollux, which is a single star, is 34 light-years distant, so the two are not connected; they just happen to lie near each other in our sky.

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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