For the last several months skywatchers have been able to focus on great views of the planets. This will prove to be true throughout the month of May as well. Those of us with telescopes can obtain dramatic views of phase changes in Venus, spectacular rings around Saturn, and neat surface markings on Mars. But if we lived on the west coast of the USA, we would be treated to the first “annular” solar eclipse to touch any of the states since 1994 on the late afternoon of May 20th. Unfortunately for us east of the Rocky Mountains, the Sun will already have set, and we will miss it entirely.
An annular solar eclipse happens when the Moon directly on the Earth-Sun line also reaches the farthest point from Earth in its orbit around us, and therefore appears a little too small to fully block the Sun. About 90% of the Sun will be blocked in this eclipse, but at mid-point of eclipse, the Sun will appear as a “ring” of light in the sky. (The name annular comes from the Latin word for ring, annulus ——- thus it is an annular eclipse). The next such event will not happen until 2023. But let’s get back to what we CAN see.
Venus will jump out at us early in May as soon as the sky darkens. Look west for this brilliant “evening star.” It is at maximum brightness of -4.7. On May 1st it will be some 30 degrees above the west horizon and not set until 11:30 pm. But its orbit around the Sun, smaller than ours and inside ours, is bringing it closer to us and “tucking” it between us and the Sun. Indeed by May 31st, Venus will only be about 10 degrees above the horizon, and will set just 40 minutes after the Sun. But look at it on May 22nd when the crescent Moon will be seen just 5 degrees below and left of it.
Venus’s orbital motion will also cause the telescopic views of it to change as well. It will appear crescent all month, but the crescent will shrink (less lit-surface seen) while the overall size of the planet image will increase by about 40%. Next month I will feature a Venus transit event for June 5/6 in my article, when with eye protection we can look at the Sun and watch the planet Venus appear as a black dot crossing in front of the Sun’s surface.
Mars begins May just a little left(east) of Leo’s brightest star Regulus, high up in the southern sky. Its orbit will take it away from Regulus through the month, so it will be twice that distance left of it by May 31st. Mars outshines Regulus by almost 4 times and its reddish color makes a nice contrast with the blue-white color of this hot star. Telescope views this month will reveal the white north polar cap and some dusky surface markings.
Saturn can be found by shifting your gaze due east. It too is among the stars of a zodiac constellation; in this case, Virgo. And it too is near the brightest star of this constellation, Spica. This month these two will appear to remain about 5 degrees apart; with Saturn to the left of Spica. Saturn is so far away that its orbital motion over a month’s time is not as noticeable in reference to background stars as the motion of Mars, which is much closer to us. Telescopes will show Saturn’s lovely rings, tilted 13 degrees to our line of sight, and can reveal several of the planet’s over 60 moons.
Full Moon is early this month; on May 5th, with last quarter on the 12th. First quarter phase will be seen on May 28th, and on May 29th, the Moon will appear just 7 degrees below Mars in the southern sky.
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