Stellar Vista Observatory Sky Report: May 17-23

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].

Saturn Nebula | Image by Fort Lewis College Observatory courtesy of Stellar Vista Observatory, St. George News

This is the final week that all five planets are visible. Mercury is low in the west after sunset, where it has been all month, but this week it leaves us.

A few weeks ago, Mercury was on the far side of the sun and approaching us in a big arc. On May 27 it’s as far from the sun as it will be, angle-wise, and that’s 22 degrees. Then it’s coming straight at us and telescopically it looks like a tiny half-moon. As it continues to approach, it grows larger and becomes an ever-slimmer crescent – and grows fainter — until it’s between the us and the sun on June 9. On what day will you last see it? Incentive will be strong on May 28; more on that next week.

Look for Mercury low in the west a half hour after sunset, and use binoculars because the sky is still so bright. If your horizon is low enough you’ll see Venus, which is much brighter, below Mercury. Venus is getting easier to see night by night, while Mercury is getting harder.

Mars is one-third of the way up the western sky an hour after sunset, in the middle of the Gemini twins. The stars Castor and Pollux, which are slightly brighter, are above Mars, while substantially brighter stars are Capella to the right and Procyon to the left. We’ll see Mars until early July.

In the morning sky, brilliant Jupiter rises four hours before the sun. An hour before sunrise – when the sky is beginning to brighten – Jupiter is one-third of the way up the southeastern sky, where it outshines everything else. Saturn is to the upper right of Jupiter and they’re separated by 17 degrees, almost twice the width of your fist held at arm’s length. Watch this separation increase in years to come. Saturn is 3 magnitudes or 15 times  fainter than Jupiter.

If you have a telescope, note that the planet Saturn is closer to the Saturn Nebula now than it will be for the next 30 years. Saturn is a planet with rings that orbits our sun, while the Saturn Nebula is a shell of gas expelled by a star at its center; the star has become a white dwarf. It lies roughly 3,000 light-years away, is magnitude 8 and superficially resembles the planet Saturn, which is 6 degrees below. Any of the astronomy apps I’ve recommended will let you find it.

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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