This Week’s Sky at a Glance, 2024 Dec 14 – Dec 21
This Week’s Sky at a Glance, 2024 Dec 14 – Dec 21
Evening stargazing can be tricky this time of year with all the festive lights, especially if you have a neighbourhood Griswald. If you happen to be out, try identifying a few constellations. In the northeast there is pentagonal Auriga the Charioteer, with bright Capella the Goat Star at one corner. To the right is the V-shaped face of Taurus the Bull, with the dipper-like star cluster of the Pleiades marking its shoulder and Jupiter currently residing within its horns. Orion and Gemini follow below Taurus and Auriga. Above Auriga is Perseus, seemingly standing on the bull’s back. It is here a patient stargazer can watch a marvel of the night sky.
In mythology, Perseus beheaded Medusa and used her snaky head to seek revenge on tormentors by turning them to stone. The second brightest star in the constellation Perseus represents the evil eye of Medusa and it is called Algol, the ghoul or demon. There is a reason for this name. Every three days, minus about three hours, this star slowly dims by a factor of three and regains brightness over several hours. Algol is an eclipsing binary, two stars orbiting each other closely and aligned to our line of sight. When the smaller, dimmer star passes in front of the brighter star we can see the stars’ combined light dim and recover. By comparing it with nearby stars of similar brightness you might notice Algol putting on its show. Our next convenient evening opportunity to watch this is on Wednesday when Algol is dimmest around 7:50 pm, so start watching an hour or two sooner and check on it every 15 minutes.
This Week in the Solar System
Saturday’s sunrise is at 7:56 and sunset will occur at 4:42, giving 8 hours, 46 minutes of daylight. Next Saturday the Sun will rise at 8:00 and set at 4:44, giving 8 hours, 44 minutes of daylight. The Sun reaches the Winter Solstice point around 5:21 on the morning of December 21, the shortest daylight of the year (by one second).
The Moon rises near Jupiter around sunset this Saturday; it is full early Sunday and within a binocular view above Mars on Tuesday evening. Brilliant Venus can be seen in the southwest soon after sunset, slowly gaining altitude nightly and setting after 8 pm. Saturn is at its highest and best for observing around 6 pm, showing its rings nearly edge on. On Tuesday evening at 8:05 telescope users might see Jupiter’s moon Io begin transiting the planet, followed by Io’s shadow at 8:20 when the Red Spot is in mid-transit. Mars slowly edges westward against the background stars over the week but remains within a binocular view of the Beehive star cluster. The Geminid meteor shower is at its peak early this weekend, a worthy view despite the bright moonlight.
Tune in to the Sunday Night Astronomy Show at 8 pm on the YouTube channel and Facebook page of Astronomy by the Bay.