Jul 16

Sky Report: July 18-24

All the planets except Mercury are visible tonight.

Saturn rises around 10 p.m. so it’s in the evening sky. You’ll find it low in the east-southeast at midnight. Saturn is in eastern Capricornus.

Jupiter rises two hours later and follows Saturn across the sky. Being both larger and closer it’s much brighter — 16 times brighter, and Jupiter outshines every star in the sky. Jupiter is in northern Cetus through August, according to the way modern astronomers define the constellations.

Mars rises an hour and a half after Jupiter, also rising a bit north of east, and it’s the same brightness as Saturn (Mars is closer but smaller so the two balance). After 2 a.m. you can see these three planets strung out in a line 70° long with Jupiter roughly in the middle.

See if you can predict this (a project for night-owls): All three planets are moving eastward against the background stars. Mars is moving fastest, Jupiter next-fastest, and Saturn the slowest. On which date this summer will Jupiter be precisely in the middle? It’s an experiment you can do with pencil and paper, a ruler, and your eyes.

Venus is nearly in line with the sun (on the far side of it) and rises 2 hours before the sun, but it’s great brilliance (3 times brighter than Jupiter) lets you see it low in the east-northeast in morning twilight, if you have a low horizon. It’s 20° high at the moment of sunrise.

Every month the moon passes all the planets, since the moon orbits the earth and circles the sky in a month (“moon-th”). The planets lie nearly in the same plane as the moon’s path around the sky and so it has to pass them, sometimes close and sometimes not so close. It will be close to Mars on the morning of the 21st (and near Venus on the 26th). That morning Mars will be only 2½° from the moon and the two will fit comfortably in the field-of-view of binoculars and some spotting ‘scopes. This is the closest a planet will come to the moon this month.

If you could measure the distance precisely between the moon and Mars you’d see that the moon’s orbital motion, which carries it eastward at an average of 13° per day or approximately ½° per hour, is carrying it toward Mars. At about 11 a.m. MDT they’re separated by only ½°, or the diameter of the moon. You can easily see the moon then, half-way up the western sky, but Mars is far too faint to see with your eyes alone. But if you have a telescope you might try; Mars is at the 8:30 o’clock position from the moon and you might barely see it if the air is clean, free from dust and haze. But if you were in northern Japan or eastern Russia the moon would cover, or “occult” Mars before sunrise and that would be especially interesting to see.

Stellar Vista Observatory provides portable telescopes and tripod mounted binocular kits on loan for free to residents and visitors in Kane County. Enhance your enjoyment of the night sky! For details or to request a loan, visit https://stellarvistaobservatory.org/discover-the-night-sky/ or drop in to the Kane County Office of Tourism.

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 John@StargazingAdventures.org.

About the Author:

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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