This Week’s Sky at a Glance, 2022 January 15 – 22 ~by Curt Nason
There is one river seen from New Brunswick that is completely ice-free all winter, but we can only see it on clear nights. Eridanus the River, the fifth largest constellation in area of the sky, has its head just off the foot of Orion near Rigel. Even when it is at its highest in our sky, the river’s meandering path takes it more than ten degrees below the horizon to where it terminates at Achernar, the ninth brightest star.
In mythology the river is associated with Phaethon, a mortal son of Apollo. Apollo drove the Sun, a golden chariot powered by mighty steeds, across the sky by day. Phaethon was allowed to drive it one day but he couldn’t control the steeds. They ran amok, scorching the sky (the Milky Way) and the Earth (Sahara), until Zeus blasted Phaethon with a thunderbolt and he fell to his death in the river. The asteroid 3200 Phaethon, which is the source of the Geminid meteor shower in December, orbits from outside Mars to within the orbit of Mercury and is one of the Apollo family of Earth-crossing asteroids. The twisty constellation Eridanus was also considered to be the path of souls.
Although we can’t see Achernar without travelling to Florida, there is a notable star in Eridanus that we can see from outside a city. Omicron-2 Eridani, also called 40 Eridani or Keid (circled on the map), has a famous fictional and fascinating planet: Vulcan, the home of Spock. Did you know that there was once believed to be a planet closer to the Sun than Mercury? It was named Vulcan after the Roman god of fire, metalworking and the forge. Anomalies in Mercury’s orbit were thought to be due to an interior planet, and some astronomers even claimed to have seen it crossing the Sun. The anomalies of Mercury’s orbit were finally explained by some guy named Einstein in his General Theory of Relativity. Coincidentally, regarding the god Vulcan, the constellation Fornax the Furnace barely crests our horizon near Eridanus.
This Week in the Solar System
Saturday’s sunrise in Moncton is at 7:57 am and sunset will occur at 5:00 pm, giving 9 hours, 3 minutes of daylight (7:59 am and 5:07 pm in Saint John). Next Saturday the Sun will rise at 7:52 am and set at 5:09 pm, giving 9 hours, 17 minutes of daylight (7:54 am and 5:17 pm in Saint John).
The smallest full Moon of the year, the Puny Moon, occurs on Monday. At midweek Mercury sets around 5:50 pm, followed by Saturn at 6:15 and Jupiter at 8:00. Venus rises an hour before sunrise this Saturday, an hour behind Mars. By spring the planetary action will have shifted to the morning sky.
On Sunday evening at 8 pm, tune in to the Sunday Night Astronomy Show via the Facebook page or YouTube channel of Astronomy by the Bay.
Questions? Contact Curt Nason.