Heads UP! for May 2018
Jupiter is the brightest dot in the sky after Venus. The giant planet is further away, but being so large, is very bright. Jupiter’s as big as it’s going to get in 2018. Saturn and Mars are getting larger, but they rise later in the evening. The International Space Station is visible up to five times a night in late May.
Got a telescope? Get it out and practice focusing on Jupiter! (Ok, if the moon is out, start with that – it’s a great target to practice focusing!) Jupiter’s four brightest moons are visible with any optical aid, even (steadily held) binoculars. Leaning them up against the corner of a building is good. This great view is thanks to our opposition with Jupiter on May 8th, when Jupiter is directly opposite from the Sun in our sky, and closest to us. Don’t worry about seeing Jupiter on the exact date – it’s be great for the next two month.
Watch for the Great Red Spot. It’s smaller than in past centuries. Make your own estimate of the hue and brightness of the Great Red Spot.
Jupiter’s four brightest moons would be visible to the unaided eye as faint stars, brighter than Uranus or Neptune. However, they are in the glare of Jupiter and we need optical aid to separate them from the planet. It helps to have a chart of which moon is where. Charts are available on many web sites and in astronomy magazines. Some observers with large telescopes and good skies will be able to show us some details on these distant worlds.
My favorite site to see the latest shots from planetary paparazzi is http://alpo-j.asahikawa-med.ac.jp/indexE.htm . One of the best of these photographers is Christopher Go from the Philippines. Check out his latest photos at his facebook page. I’ve shared a few on my public page.
As Jupiter, Saturn and Mars approach opposition, the photos will get better and better. Since Jupiter rises at sunset this month, it is highest in the sky just after midnight, but the King of the Planets is still worth taking the time to see in evening or morning skies.
Mars is highest in the sky by sunrise, but even then, it sits low in the southern sky. Its apparent size increases by one-third in May. By the end of the month, the southern polar cap starts tilting a bit toward us and is still substantial as winter is ending in Mars’ southern hemisphere. The white polar cap compared with the reddish Martian dust may give us enough contrast to be seen in smaller telescopes. Mars is 90 percent sunlit, noticeable in all telescopes.
Saturn tops the teapot portion of Sagittarius, low in the south at dawn. Saturn’s rings are still opened wide toward us, rewarding the early morning observer. Its largest moon, Titan, at magnitude +8.4, is visible in telescopes. Iapetus, at magnitude +11, passes south of the planet on the 23rd. The two-faced moon is on its way toward showing its more reflective side, peaking in brightness to the west of Saturn in mid-June.
While you are in northern Sagittarius, use binoculars or a telescope to check out minor planet 4Vesta at magnitude plus 6. Look for a finder chart with both Saturn and Vesta at sites like http://www.nakedeyeplanets.com/vesta-2018.htm . Open cluster M18 is just north of Vesta’s location.
The Moon hangs as if lounging in a hammock between Mars and Saturn on the 5th.
Venus dazzles in the western sky for two and a half hours after sunset through June. Get out there just after dark in early May to see Venus positioned near the Hyades open star cluster and their honorary member, bright Aldebaran. Best views of Venus, in the telescope, are during early twilight. (Or, daytime, if you can find Venus when it’s highest in the sky in the early afternoon. Remember to keep the Sun behind a solid, opaque object!) Our evil twin planet is just starting to look a bit out of round, almost as gibbous as Mars (and nearly the same apparent size as Venus is larger, but further away).
Mercury peeks out from the Sun in the morning sky early in the month. It doesn’t stray too far and it even harder to see than usual, rising less than an hour before the Sun.
The Eta Aquariid meteors give a strong show for southern hemisphere observers. However, if you are up early on the 6th, be on the watch for a few long-path meteors streaking across the eastern sky from right to left. Since the radiant is near the horizon at dawn, the resulting meteors at our latitude skip sideways across the top of our atmosphere. The gibbous moon will be out that morning, making it harder to see these grains from Comet Halley. While you are out, compare the Moon and Mars, just four moon-widths apart.
The International Space Station is visible every for a few minutes of each 93-minute-long orbit after midnight for much of the month. During the last third of the month, our out-of-this-world human outpost is visible in the evening skies, as well. There are five overflights visible on the night of May 21/22; some a bit low in our sky. That’s because the ISS is in daylight all the time for several days around the 21st. Check NASA or heavens-above.com for updated times and directions to look.