SKY GUIDE: This chart represents the sky as it appears over Maine during May. The stars are shown as they appear at 10:30 p.m. early in the month, at 9:30 p.m. at midmonth and at 8:30 p.m. at month’s end. Venus is shown in its midmonth position. To use this map hold it vertically and turn it so that the direction you are facing is at the bottom. Sky Chart prepared by George Ayers.
The month of May is named for Maia, the Greek goddess of fertility. As of the first of this month we are half way into spring with the nights getting warmer and shorter. Despite what is going on now, the scenery of our hemisphere will be transformed into spring greenery as leaves will be emerging once more along with many migrating birds returning and the spring peepers singing up a storm in our marshes, adding a joyful terrestrial chorus to the celestial harmonies always going on above us.
May 2 marks the first of two International Astronomy Days this year. The other one is Sept. 26. Hopefully we can celebrate that one with large groups of people again. Started in 1973 as a way for the whole world to appreciate our heritage and bringing more people to astronomy and its benefits, a second International Astronomy Day each year was started in 2006, the same year that Pluto was reclassified as a dwarf planet.
Many people probably have extra time now to get out into nature including the sky at night. There are many great events this month that people should not miss while they are outside gaining much-needed inspiration from nature itself. These include a nice conjunction of Mercury and Venus in the evening sky, a challenge you can accept concerning Venus, three bright planets still close together in the morning sky, another meteor shower, and another comet.
Venus has been our lone evening star for many months, but it will finally be gaining a companion starting on May 11. Mercury will start to emerge very low in the evening twilight in the west-northwestern sky well below Taurus. Then keep watching as Mercury climbs higher even as Venus sinks lower. They will be only one degree apart on May 21. Mercury is on its way to greatest eastern elongation from the sun in early June just when Venus finally sinks out of sight after its best apparition in eight years. Venus moved higher in the sky for several months as it slowly got brighter, but it will undergo a radical transformation this month as it gets much larger and thinner even as it rapidly sinks out of sight.
The challenge you may accept concerning Venus is attempting to see its thin crescent without a telescope or even binoculars. Normally that is not possible because the resolution of an object would have to be at least 1 arc minute for the human eye to be able to discern it. The full moon and the sun are each 30 arc minutes, or half a degree of the sky. Venus starts this month at 40 arc seconds in size and 25% illuminated by the sun. Then it rapidly gets less illuminated and larger in our sky as it is catching up with Earth in its faster orbit around the sun. It will be just 1% lit by the end of the month and will cover almost one full arc minute of the sky.
As a trick to help you see it, look at it through a piece of cardboard with a 1-2 mm wide hole in it to cut any glare. Then confirm that you saw the crescent just by looking at it with a pair of binoculars. Then Venus heads off to its inferior conjunction with the sun on June 3. That is when Venus transits like the ones we had in June 2004 and June 2012. I was lucky enough to see both of those. Now we have to wait until 2117 for the next one. The one in 2004 was much more dramatic since I could clearly see the black disk of Venus glide across the right limb of the sun for several minutes. I even saw the hot and poisonous atmosphere of Venus glowing against the blackness of space as a thin, semicircular arc of ephemeral light. I expected to see the black drop effect as Venus was exiting the sun, but I did not expect the nice bonus of seeing its dense atmosphere, nearly 100 times as dense as ours, a real runaway greenhouse effect.
The rest of the action is still unfolding in the morning sky. Jupiter, Saturn, and Mars are keeping the same order from right to left, but Mars is moving faster to the left, or east, of the pair now. All are getting higher and brighter even as they are getting closer to Earth. Orange Mars will change the most, gaining nearly half a magnitude in brightness on its way to a good October opposition. Notice that Jupiter in Sagittarius and golden Saturn in Capricorn will remain about 5 degrees apart while Mars will drift farther east to the other side of Capricorn, about 15 degrees east of Saturn by the end of the month.
As the earth is catching up with these slower moving planets now, two will go into retrograde this month. Saturn will start its westward or retrograde motion on May 11 and Jupiter will follow on May 14. Jupiter and Saturn start this month by rising around 1:30 a.m., but will end the month rising before midnight on their way to their oppositions in the middle of July, two months later. Then they will both return to their direct, or prograde, motion by the middle of September.
If you missed the Lyrid meteor shower last month, which happened right at new moon and in the middle of International Dark Sky Week, you will get another chance this month. This one is caused by Halley’s Comet, the only comet that creates two meteor showers for us each year, the May 5 Eta Aquarids and the Oct. 21 Orionids. The only problem will be that the moon will be 91% full and waxing gibbous, washing out about half of the meteors. The best time to see these tiny, grain-of-sand-sized pieces of Halley’s Comet burn up at 70 miles high in our atmosphere will be from 3-5 a.m. on the morning of May 5. You may also see other unrelated meteors that came from other parts of the sky.
Comet Atlas recently broke up into at least four pieces and is rapidly fading out. A comet named Swan took its place, but is currently only visible in the southern hemisphere. However, Comet PanSTARRS is still on track. It will reach perihelion, or closest to the sun, on May 4 at 150 million miles away. It should reach about eighth magnitude, or 6 times fainter than what the naked eye can see, through all of May and into June. It starts off this month in Camelopardalis the Giraffe and then heads south into the Big Dipper by the middle of May. It will pass very close to the large galaxies M81 and M82 on May 24. That would be a great time to photograph it.
MAY HIGHLIGHTS
May 5: The Eta Aquarid meteor shower peaks this morning.
May 7: Full moon is at 6:46 a.m. This is also called the flower, milk, or planting moon.
May 12: The first planetarium in this country, the Adler in Chicago, was opened on this day in 1930. The waning gibbous moon is right below Jupiter this morning.
May 13: The moon is near Saturn this morning.
May 14: The moon is near Mars this morning. Skylab was launched on this day in 1973. Last quarter moon is at 10:04 a.m.
May 21: Mercury and Venus are just one degree apart this evening.
May 22: New moon is at 1:40 p.m.
May 23: A very thin waxing crescent moon is below Venus and Mercury and just to the left of the pair the next evening.
May 28: In 1959, the first primates – Able and Baker – were launched into space.
May 29: First quarter moon is at 11:31 p.m.
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