Stellar Vista Observatory Sky Report
John Mosley
Aug. 1 – 7
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].
First, meteors. The Delta Aquarid meteors continue from July. A huge number of meteors fall in this shower but they’re spread over several weeks so the number per hour is only around a dozen. They radiate from the constellation Aquarius in the south in the morning.
By far the most popular shower of the year is the Perseids, which begins about now, but the Perseids have a short peak of a few days at most, and this is because the swarm of particles that produce the Perseids is narrower and more concentrated than the older Delta Aquarid, which has had time to disperse and spread out.
Perseids radiate from the direction of Perseus (no surprise!), which rises toward midnight, so you see these meteors from late evening through the night. Unfortunately this year bright moonlight will ruin the shower when it’s at its best on the night of July 12. I had more on meteors last week. The Sky Report is archived, and you can read back issues at this link.
Regarding the planets, once again all naked-eye planets are out tonight. Mercury is back in the evening sky although it’s so near the horizon it will be difficult to spot. Look about 10 degrees to the left of where the sun set during twilight and use binoculars.
Saturn rises an hour or so after dark. Much brighter Jupiter rises by midnight, and Mars, which is the same brightness as Saturn, rises an hour after midnight. They’re nearly equally spaced with Jupiter in the middle. I had asked if Sky Report readers could estimate when the three planets are precisely evenly spaced just by watching them nightly, noting that Mars is moving eastward against the stars faster than the other two. That day is coming up soon.
Mars passes Uranus this week. From Saturday through Thursday, they’re within 2 degrees of each other, and on Monday and Tuesday mornings, Uranus is only 1-1/3 degrees above Mars, and the two can be seen together in a spotting telescope. Uranus is 18 times more distant than Mars and 1/200th as bright – but still bright enough at 6th magnitude to be seen naked-eye by people with perfect eyesight.
With a 6-inch or larger telescope, both planets look like disks, not point-like stars; Mars has a diameter of 8.3” and Uranus 3.6”. When William Herschel discovered Uranus in 1781, he immediately realized that it was not a star because it had a disk and did not look starlike. At first he thought it was a comet because the idea that there could be unknown planets beyond Saturn was too strange to be entertained.
Venus rises 1-3/4 hours before the sun where it shines brilliantly through morning twilight low in the east-northeast.
Comet C/2017 K2 remains bright enough to see in any amateur telescope and possibly binoculars, and it’s nicely placed in the Ophiuchus and then Scorpius for viewing in the early evening. Catch it soon before the moon becomes too bright.
Caption: Mars and Uranus Aug. 1-5. Distant Uranus is virtually stationary in the sky while speedy Mars moves past it at the rate of over half a degree per day. The two are closest on the mornings of Monday and Tuesday but Uranus remains within 3 degrees of Mars through Saturday. The circle is 4 degrees in diameter. This is an opportunity to spot Uranus with binoculars or any telescope. Graphic created with SkySafariAstronomy.com. https://stellarvistaobservatory.org/discover-the-night-sky/.