Stellar Vista Observatory Sky Report for November 22 – 28

Twilight with stars at Zion National Park, Utah, courtesy of the National Park Service, St. George News

Stellar Vista Observatory Sky Report
John Mosley

Nov. 22 – 28

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 at www.stellarvistaobservatory.org. Send questions and comments to [email protected]

The bright planets Venus, Jupiter and Saturn are nearly equally spaced in the southwest in the evening sky, with Saturn slightly closer to Jupiter than to Venus. Venus’ motion around the sun is carrying it eastward against the background stars of Sagittarius and closer to the outer planets, which, being slower in their orbits, are barely moving against the distant stars.

Watch carefully, and by your own observations on which night is Saturn exactly between Jupiter and Saturn? The planets’ motions are a continuous process, not a series of isolated events.

These three bright planets have graced the early evening sky and we are used to seeing them there, so enjoy them now. But in only a month Jupiter and Saturn will be low in the west, setting early, and Venus will be gone, and beginning in February the evening sky will be entirely devoid of bright planets. Don’t take their appearance for granted.

Because the earth moves 1 degree a day eastward as we orbit the sun (360 degrees in 365-1/4 days), the distant planets Jupiter and Saturn move 1 degree a day westward. So do the stars behind them; this is the consequence of the earth’s annual motion around the sun. Moving 1 degree westward means they set four minutes earlier each day, or a half-hour earlier each week, or two hours earlier each month. Where the planets are at 7 p.m. now is where they will be at 6 p.m. in two weeks.

This general guideline applies to the outer planets and stars near the ecliptic – the path of the planets – but not to Mercury and Venus. Their individual motions also must be taken into account. This week alone, for example, Venus’ angular distance from sun decreases from 44 degrees to 42 degrees, causing it to set even earlier than the above formula would suggest. You’ll see that dramatically in mid-December when Venus rapidly disappears from the evening sky.

Mars is very slowly returning to view in the morning sky where it is not very bright. Look for it very low in the east-southeast during morning twilight. It’s especially close to the star Zubenelgenubi on Monday morning when the star is only 1/5-degree above Mars. Zubenelgenubi is 1/3 as bright as Mars and it has a companion star traveling with it, so the two make a beautiful pair in binoculars; three including Mars.

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