April greetings. In the column this month, I’ll focus on the solar system. That will include all five naked-planets, a blue moon, and a visible meteor shower.
Four of the five planets will be visible in the morning sky before sunrise, but you’ll need to act fast to see the swiftest one, Mercury. Go out this week about 5:45 a.m. to a place with a nice, flat eastern horizon. You’ll find brilliant Venus just above the horizon in the east. It may seem low, but Mercury is even lower and to the left, by about the width of four fingers held at arm’s length. By the end of April it will be too close to the sun to be seen. Jupiter and Saturn are also visible in the morning sky. Look to the south and you’ll find those two planets shining brighter than any of the surrounding stars. Jupiter is brighter and to the right; Saturn, fainter and yellowish, is to the left. If you go out before the light of dawn (say 5 a.m.) you’ll spot the teapot shape of the constellation Sagittarius between and below the two planets. Jupiter and Saturn are currently 26 degrees apart; that’s about the width of an outstretched thumb-to-pinky. They engage in a complex dance in the night sky as a result of our one-year orbit, Jupiter’s 12-year orbit, and Saturn’s 30-year orbit. This dance brings them close together in the sky every 18-20 years. The last such “great conjunction” was in 2000, and the next is coming up in December 2020. Jupiter will be becoming an evening sky object in the next few weeks, at least if you define that as rising before midnight. Currently it’s coming up about 12:30 a.m., but by the middle of May it will be up at 10:30 p.m. Saturn follows it about two hours later. Mars, currently located on the other side of the sun from our perspective, is not very bright right now, but you can find it in the evening sky in the west just after dark. Look for it to the right of Aldebaran, the “eye” of Taurus the Bull. Both the star Aldebaran and Mars are reddish, but Aldebaran is the brighter of the two.
The moon is full this month on April 19. In the waning half of its cycle it will pass near Jupiter on April 23 and Saturn on April 25 (both as a waning gibbous). As a waning crescent it will be near Venus and Mercury, very low in the east, before sunrise on May 1 and 2. This should be a beautiful sight. The next full moon, May 18, will be a blue moon as that term was originally defined: the third full moon in a calendar season containing four full moons. (Most seasons contain three.) The definition which has caught on in modern times is the second full moon in a month containing two. The next by that definition will be in October 2020. Weirdly, the term “blue moon” has nothing to do with the moon actually appearing blue. Maybe “extra moon” would be a better term.
Finally we can look forward to the Eta Aquarid meteor shower. It occurs every year when the earth passes through the dust trail left by Halley’s Comet and tiny particles burn up in the earth’s atmosphere as “shooting stars.” They aren’t stars, of course, but it’s still a good description of what meteors look like. The peak this year will occur on May 5, which is fortuitous because the moon is near new and will not be in the sky to interfere. Go out between midnight and dawn, far from artificial lights, allow your eyes to dark-adapt, and look up. You may see a few of the bright streaks of light left behind by dust particles hitting the earth’s atmosphere at a whopping 148,000 mph and burning up.
I’ll see you in May with more to say about “What’s Up.”