The Sky This Week
U.S. Naval Observatory's Weekly Blog

The Never Ending Celestial Chase

by Geoff Chester, USNO Public Affairs
22 February 2022

Messier 42, the Great Nebula in Orion, imaged from Alexandria, Virginia, 2022 February 21
with an Explore Scientific AR102 10.2-cm (4-inch) f/6.5 refractor and a ZWO ASI183MC CMOS imager.

The Moon retreats to the morning sky this week, waning from Last Quarter as she dives to the southernmost reaches of the ecliptic.  New Moon occurs on March 2nd at 12:35 pm Eastern Standard Time.  If you are up before the Sun you will have some interesting sight to see as morning twilight begins to brighten the sky.  On the morning of the 24th you’ll find the Moon just three degrees northeast of the bright star Antares in Scorpius.  On the 27th Luna, Venus, and ruddy Mars greet early risers with an attractive grouping in the southeastern sky.

The Moon’s absence from the evening sky means that it’s time for the February observing campaign for the Globe at Night citizen science program.  The target constellation for February is Orion, which is high in the southern sky, crossing the meridian at 7:30 pm local time.  Orion is the easiest constellation to view in the program, with his distinctive outline visible from just about anywhere, including the centers of light polluted cities.  The basic idea of Globe at Night is to have people look at a patch of the night sky centered on a familiar constellation, then use the online star charts to determine the faintest stars that you can see from your location.  Choose a clear night and try to view the sky from a location away from the direct glare of artificial light sources.  Let your eyes adapt to the darkness for at least 10 minutes before you look at the sky.  Report your observations on the Globe at Night web app.  In 2021 over 25,000 observations were recorded from all 50 states and 90 countries around the world.  

We have reached a time of year when we can observe two constellations on opposite sides of the sky that share both physical and mythological characteristics.  We have already mentioned Orion in past editions of “The Sky This Week”.  This constellation is known for its red supergiant star Betelgeuse and it bright, blue-tinted companion stars.  These blue stars are part of what is known as an “O-B Association”, a physically bound group of very young, energetic stars of spectral types O and B that have a common origin.  The site of their birth is the Great Nebula, which can be easily seen in binoculars as a small fuzzy patch in the asterism known as The Sword.  Halfway around the sky, and now rising in the southeast before the beginning of morning twilight, is the red-tinted star Antares, the brightest star in the constellation of Scorpius, the Scorpion.  It, too, is a red supergiant star, and it is surrounded by bright blue stars that form another O-B association.  These physical similarities are remarkable in their own right, but the two constellations are also linked in the Greco-Roman mythology that defines our sky lore.  According to these traditions, Orion was a half-mortal demi-god gifted with extraordinary hunting prowess.  At one time he boasted that he could kill any animal on Earth.  This claim angered Gaia, the Earth Goddess, who decided to teach the brash Orion a lesson.  She sent a lowly scorpion to kill him, and almost succeeded.  The scorpion stung Orion on his foot, and he came perilously close to death before being saved by Ophiuchus, the Serpent Bearer, identified by the Romans as the healer Asclepius.  When Zeus placed the participants in the sky, he put them on opposite sides of the sky so they would never encounter each other again.

All of the bright planetary action now takes place in the pre-dawn sky.   Venus is the most prominent object in the early morning hours, blazing away over the southeastern horizon.  She rises at around 4:15 am local time and is easily seen as morning twilight gathers.
 
Just to the south of Venus is ruddy Mars.  While Venus dazzles, Mars is much more subdued.  He is best identified by his pale reddish hue.  He seems to track Venus as both planets move eastward against the stars, and over the course of the week they inch closer together.  Get up early on the morning of the 27th to see a beautiful grouping of Venus, Mars, and the waning crescent Moon.
 
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