Stellar halo around Mirfak on January 10, 2023, at 7 p.m. (Chris Vaughan and Starry Night Education | SkyNews
Stellar halo around Mirfak on January 10, 2023, at 7 p.m. (Chris Vaughan and Starry Night Education

This Week’s Sky: January 9-15

Keep an eye out for a collection of about 100 young, massive hot B- and A-class stars around bright star Mirfak on January 10.

Every week, SkyNews publishes a list of key events in the Canadian sky in This Week’s Sky. This series gives you all the latest news in Solar System movements, including where the planets are in our sky and Moon phases. From eclipses to meteor showers, This Week’s Sky keeps you updated on the best in upcoming astronomical highlights.

Tuesday, January 10 – Stellar halo around Mirfak (evening)

Stellar halo around Mirfak on January 10, 2023, at 7 p.m. (Chris Vaughan and Starry Night Education) | SkyNews
Stellar halo around Mirfak on January 10, 2023, at 7 p.m. (Chris Vaughan and Starry Night Education)

The constellation of Perseus is positioned nearly overhead in the northern sky in mid-evenings this month. 

This constellation’s location straddling the outer reaches of the Milky Way has filled it with rich star clusters. The largest of these surrounds the bright star Mirfak, or Alpha Persei. Melotte 20, also known as the Alpha Persei Moving Group and the Perseus OB3 Association, is a collection of about 100 young, massive hot B- and A-class stars spanning three degrees of the sky. 

The cluster can be seen with unaided eyes and improves in binoculars (green circle). It is approximately 600 light years from the Sun and is moving as a group. Mirfak is moving with them. This elderly yellow supergiant star has evolved out of its blue phase and is now fusing helium into carbon and oxygen in its core. 

Thursday, January 12 – Mars stands still (all night)

Mars stands still on January 12, 2023, at 7 p.m. (Chris Vaughan and Starry Night Education) | SkyNews
Mars stands still on January 12, 2023, at 7 p.m. (Chris Vaughan and Starry Night Education)

On Thursday, January 12, the bright reddish planet Mars will cease its westward motion through the stars of northern Taurus, ending a retrograde loop (red path with labeled dates:time) that began in late October. From this point on, Mars will ramp up its regular easterly prograde motion above the bright reddish star Aldebaran, moving farther away from the nearby Pleiades star cluster (also designated Messier 45) each night. 

Saturday, January 14 – Third quarter Moon (at 02:10 GMT)

Third quarter Moon on January 14, 2023, at 9:10 p.m. EST. (Chris Vaughan and Starry Night Education) | SkyNews
Third quarter Moon on January 14, 2023, at 9:10 p.m. EST. (Chris Vaughan and Starry Night Education)

The Moon will reach its third quarter phase on Saturday, January 14 at 9:10 p.m. EST and 6:10 p.m. PST, which converts to 02:10 GMT on Sunday. The Moon will rise at about midnight local time and remain visible until late on Sunday morning in the southern sky. At third quarter, the Moon is illuminated on its western side, towards the pre-dawn Sun. 

Last quarter moons are positioned ahead of the Earth in our trip around the Sun. About three and a half hours later, Earth will occupy that same location in space. The week of moonless evening skies that follows the third quarter period will be ideal for observing deep sky targets.

Chris Vaughan is a science writer, geophysicist, astronomer, planetary scientist and an “outreach RASCal.” He writes Astronomy Skylights, and you can follow him on Twitter at @astrogeoguy. He can also bring his Digital Starlab portable inflatable planetarium to your school or other daytime or evening event. Contact him through AstroGeo.ca to tour the Universe together.

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