Sky ArchiveTonight

Moon and Fomalhaut in late September

Moon swings by the star Fomalhaut in late September 2020.
Watch for the moon and bright star Fomalhaut, September 28-30, 2020.

These next several nights – September 28, 29 and 30, 2020 – use the bright waxing gibbous moon to find the star Fomalhaut. It’s one of our sky’s 1st-magnitude stars, or brightest stars, and appears in a part of the sky that’s largely empty of other bright stars. For this reason, Fomalhaut is often called the Lonely One or Solitary One.

It’s bright enough to withstand the lunar glare in late September.

Fomalhaut lies way south of the ecliptic, which, on sky charts, depicts the sun’s annual path in front of the constellations of the zodiac. The ecliptic also depicts the approximate monthly path of the moon in front of the zodiac. From mid-northern latitudes in the Northern Hemisphere, at about 8 to 9 p.m., you’ll find Fomalhaut peeking out at you just above the southeast horizon. No other bright star sits so low in the southeast in the evening at this time of year. From this hemisphere, Fomalhaut dances close to the southern horizon until well after midnight on these autumn nights. It reaches its highest point for the night in the southern sky at about 10 to 11 p.m. local time (11 p.m. to midnight daylight saving time). At mid-northern latitudes, Fomalhaut sets in the southwest around 2 a.m. local time (3 a.m. daylight saving time).

For the fun of it, we show Neptune, the eighth (and farthest known) solar system planet, on our chart. This world is way too distant and faint to see with the unaided eye. You need an optical aid to see Neptune, and it also helps to have a moonless night.

From the Southern Hemisphere, Fomalhaut rises in a southeasterly direction, too, but this star climbs much higher up in the Southern Hemisphere sky and stays out for a much longer period of time. At southerly latitudes, this star rises earlier and sets later than it does at northerly latitudes.

Fomalhaut is a bright white star. Depending on whose list you believe, Fomalhaut is either the 17th or the 18th brightest star in the sky, and we regard Fomalhaut as the Autumn Star in the Northern Hemisphere.

Roughly translated from Arabic, Fomalhaut’s name means mouth of the fish or whale.

By the way, Fomalhaut is famous in astronomical science as the first star with a visible exoplanet. Click here for more about Fomalhaut and its planet, Fomalhaut b or Dagon

Black circle with white rays and glowing oval ring, inset showing planet positions 2004-2012.
View larger. | This false-color composite image, taken with the Hubble Space Telescope, reveals the orbital motion of the planet Fomalhaut b, aka Dagon. Image via NASA/ ESA/ P. Kalas. Read more about Fomalhaut and Dagon.

Bottom line: Use the moon to locate Fomalhaut, the Autumn Star, in late September 2020.

September 28, 2020
Sky Archive

Like what you read?
Subscribe and receive daily news delivered to your inbox.

Your email address will only be used for EarthSky content. Privacy Policy
Thank you! Your submission has been received!
Oops! Something went wrong while submitting the form.

More from 

Bruce McClure

View All