The May Sky
By Chuck McPartlin
The International Space Station will be appearing in our evening skies from May 13 through June 6 - more details to be posted later. Its orbit may change from time to time, so to get the latest and most complete predictions, visit Heavens Above.
May's sky events in Santa Barbara will feature the Moon and the inferior planets, Venus and Mercury. Inferior, in this context, just means that they are closer to the Sun than we are. Most people think of Mars as the Earth's nearest neighbor, as it can be about 35 million miles away during close approaches. Venus, though, can be about 24 million miles away during favorable conjunctions. However, if you take time spent close to Earth into consideration, Mercury is the closest, even though it gets no closer than 48 million miles. This is because it orbits quickly (88 days in its year), and averages only 36 million miles away from the Sun, so it's relatively close even when it's on the opposite side of the Sun from us. By that average over time metric, Mercury is also the closest planet to each of the others in our solar system!
On Monday, May 3, at about 7:50 PM PDT right after sunset, get out your binoculars to catch Mercury just 2 degrees left of the Pleiades in the western sky. If you have a low horizon, Venus will be bright and very low, almost directly below Mercury.
On Wednesday, May 12 just after sunset, a very thin crescent Moon will be snuggled up to Venus. Again, the best view will be through binoculars.
Saturday, May 15, is International Astronomy Day. The SBAU can't share the sky with the public, but you can still get out under the stars and enjoy the sights yourself.
On the 17th, again in binoculars, find Mercury at its highest altitude above the western horizon, 21 degrees up at 7:50 PM. It will be 8 degrees above, and slightly left of brilliant Venus. For scale, your closed fist held at arm's length subtends about 10 degrees of arc.
On Tuesday, May 18, look along the lunar terminator, just down from center, to catch the Lunar X as the Sun illuminates intersecting crater rims in the darkness, from about 4:45 PM to about 7:10 PM.
In the early morning of Wednesday, May 26, don't miss the shallow, but total lunar eclipse of the biggest supermoon of 2021. The dim penumbral phase starts about 1:48 AM, and our darker umbral shadow hits at about 2:45 AM. Totality starts about 4:11 AM, but the northern parts of the Moon will be barely within the umbra, and so will appear brighter. Maximum eclipse will be around 4:19 AM, and totality will end at about 4:26 AM, so we only get about 15 minutes. The Sun will rise around 5:50 AM, and the umbra will leave the Moon at about 5:52 AM, with the Moon setting shortly afterward, while still in the penumbra, at about 5:58 AM.
Just after sunset in the west on Friday, May 28, there will be a close conjunction of Mercury and Venus, with a separation of just 0.4 degrees. Mercury will be to the left and slightly below Venus, but will be about 6 magnitudes dimmer than Venus, so you'll definitely need your binoculars or a telescope and a clear sky.