Sky at a Glance 2020 January 18 – 25

Location of the constellation Eridanus the River in the southern winter sky to the lower right of Orion.

This Week’s Sky at a Glance, 2020 January 18 – 25 ~by Curt Nason

There is one river seen from New Brunswick that is completely ice-free all winter, but we can only see it at night. Eridanus the River, the fifth largest constellation in area of 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 twisty constellation 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. This was about 150 years ago, after Neptune was predicted and discovered based on anomalies in the orbit of Uranus. 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 7:55 am and sunset will occur at 5:03 pm, giving 9 hours, 8 minutes of daylight (7:58 am and 5:11 pm in Saint John). Next Saturday the Sun will rise at 7:49 am and set at 5:13 pm, giving 9 hours, 24 minutes of daylight (7:52 am and 5:20 pm in Saint John).

The Moon is at third quarter on Friday, January 17, and it passes near Mars on Monday and Jupiter Wednesday before reaching new Moon phase next Friday. Jupiter rises an hour before the Sun this week and about two hours after Mars. Venus rules the early evening sky, easily cutting through bright twilight in the southwest, while Mercury begins its best evening apparition for the year, setting 45 minutes after sunset by next weekend.

The provincial astronomy club, RASC NB, meets in the Rockwood Park Interpretation Centre on January 18 at 1 pm. There will be public observing at the Mactaquac Park office, across the road from the park entrance, in the early evening of Saturday, January 25. All are welcome.

Questions? Contact Curt Nason.

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