Evenings with Mercury | May 2021 Sky Happenings

May 6, 2021
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Mars continues to fade a little bit each night now that Earth has overtaken it and is pulling away. However, it fades out gradually; Mars remains almost as bright as the stars around it in May 2021. And Mars is high in the west–well placed for observing right as night falls.

Mars by Luke Jerram

Jupiter and Saturn are the morning sky this month, low in the southeast.

Mercury makes a brief appearance in May evening skies. Look low in the west northwest at dusk, over the point of sunset. Mercury is easiest to see during the second week in May.

Venus also slowly emerges into the evening sky this month. It appears under Mercury right now, but gets higher in the sky each evening this month. On May 28, Venus and Mercury are side by side, with Venus as the vastly brighter object).

A swath of brilliant winter stars sets in the west at dusk. Orion, the Hunter, is still visible in the west as May begins. His two dogs, represented by Sirius and Procyon, are to his left. Gemini, the Twins, are above Orion. The Big Dipper is above the North Star, with its handle pointing to the right. From that handle, you can ‘arc to Arcturus’ and then ‘speed on to Spica’; those stars are high in the east and in the southeast, respectively, at dusk. Leo, the Lion, passes almost overhead at dusk.

As Orion and his dogs set, look for Antares, brightest star of Scorpius, the Scorpion, to rise in the southeast. At the same time, Vega, brightest star of the Summer Triangle, appears low in the northeast. These stars remind us that summer is on the way.

On May evenings, the plane of the Milky Way roughly coincides with the horizon. (At Houston’s latitude, the two planes are off by less than three degrees). We are therefore looking straight out of the Milky Way plane when we look up early on a May evening. Thus May evening skies have fewer bright stars, as we see most of the brightest stars in the Milky Way plane which is ringing the horizon.

Map of the stars and planets during the month of May
This star map shows the Houston sky at 10 pm CDT on May 1, 9 pm CDT on May 15, and dusk on May 31.  To use the map, put the direction you are facing at the bottom.
 The Big Dipper is as high as it gets in the north. Leo, the Lion, is almost overhead at dusk. From the Big Dipper’s handle, arc to Arcturus and then speed on to Spica in the south.  As Orion and his dogs set in the west, Vega and Antares peek above the horizon, heralding the approaching summer. 

Moon Phases in May 2021:

Last Quarter May 3, 2:50 p.m.

New May 11, 2:00 p.m.

1st Quarter May 19, 2:13 p.m.

Full May 26, 6:14 a.m.

The Full Moon of May 26 enters fully into the Earth’s shadow, causing a total lunar eclipse! This eclipse occurs right at dawn, as the Moon is setting and the Sun is rising. Therefore, you need a perfectly clear horizon, with no buildings or tall trees to the west southwest, to see totality. Partial phases begin at 4:45 am, with the Moon 17 degrees high in the southwest. Then the Moon gets lower as it enters Earth’s shadow. By the time it is totally eclipsed at 6:11 am, the Moon is only one degree above the horizon. Totality is short; it last only until 6:25 am, right before moonset in Houston. Yes, the Moon sets while almost totally eclipsed. If this eclipse is too low for you to see well, wait for the eclipse of May 15, 2022, which begins in late evening.

Our George Observatory is now open every Saturday night for observing!

Clear Skies!

Look back to our March Sky Happenings.

Authored By James Wooten

James is the Planetarium Astronomer at the Houston Museum of Natural Science. He teaches students every school morning in the planetarium, and also answers astronomy questions from the public.

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