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, September 20 – Old Moon poses with Pollux (pre-dawn)
Early risers on Tuesday morning, September 20 can look in the eastern sky for the pretty, slim crescent of the old Moon shining just below the bright star Pollux in Gemini between about 2 a.m. local time and dawn. Pollux’ twin, the star Castor, will be positioned several finger widths above them. The scene will make a lovely photo opportunity when composed with some interesting landscape.
Tuesday, September 20 – Ganymede’s shadow crosses Jupiter (8:10 to 11 pm EDT)
Between 8:10 and 11 p.m. EDT on Tuesday, September 20, observers in the Americas with telescopes can watch the large, black shadow of the Galilean moon Ganymede cross Jupiter’s disk. That start time corresponds to 7:10 p.m. in the Central Time zone, or 00:10 GMT on September 21. For observers in western United States and Canada, only the later stages of the event will be visible while Jupiter climbs the eastern sky after dusk.
Wednesday, September 21 – Crescent Moon buzzes the Beehive (pre-dawn)
Between about 3 a.m. local time and dawn on Wednesday morning, September 21, look in the eastern sky for the very slim crescent of the waning Moon shining several finger widths to the upper left (or 4 degrees to the celestial north) of the big open star cluster known as the Beehive, Praesepe, and Messier 44. The Moon and cluster will be close enough to share the field of binoculars (green circle), but you’ll see more of the “bees” if you tuck the Moon just out of sight on the upper left.
Thursday, September 22 – September equinox (Sept 23 at 01:04 UTC)
On Thursday, September 22 at 9:04 p.m. EDT and 6:04 p.m. PDT, or 01:04 UTC on September 23, the Sun’s apparent motion along the ecliptic (green line) will carry it across the celestial equator traveling southward, marking the autumnal equinox in the Northern Hemisphere and the beginning of autumn there. On the equinoxes in March and September, day and night are of equal length and the Sun rises due east and sets due west (yellow arc).
Friday, September 23 – Morning zodiacal light for mid-northern observers (pre-dawn)
During autumn at mid-northern latitudes every year, the ecliptic extends nearly vertically upward from the eastern horizon before dawn. That geometry favors the appearance of the faint zodiacal light in the eastern sky for about half an hour before dawn on moonless mornings. Zodiacal light is sunlight scattered by interplanetary particles that are concentrated in the plane of the solar system – the same material that produces meteor showers. It is more readily seen in areas free of urban light pollution. Between now until the full Moon on October 9, look for a broad wedge of faint light extending upwards from the eastern horizon and centered on the ecliptic (the green line). It will be strongest in the lower third of the sky, below the twin stars Castor and Pollux. Try taking a long exposure photograph to capture it. Don’t confuse the zodiacal light with the Milky Way, which is positioned nearby in the southeastern sky.
Saturday, September 24 – Mars passes a star cluster (overnight)
For several nights centered on Saturday, September 24, the orbital motion of the red planet Mars (labelled path) will carry it telescope-close (small green circle) to a prominent open star cluster designated NGC 1746. The magnitude 6.1 cluster is wider than the full Moon. Viewed through binoculars (large green circle) during their closest approach, the cluster’s stars will be sprinkled in a loose clump a thumb’s width to the upper left of Mars. As the days pass, Mars will migrate below the cluster and to the left. Your telescope will likely invert and/or mirror image the scene shown here.
Sunday, September 25 – New Moon (at 21:54 UTC)
On Sunday, September 25 at 5:54 p.m. EDT or 2:54 p.m. PDT and 21:54 UTC, the Moon will officially reach its new Moon phase. At that time our natural satellite will be located in Virgo, 2.5 degrees north of the Sun. While new, the Moon is travelling between Earth and the Sun. Since sunlight can only illuminate the far side of the Moon, and the Moon is in the same region of the sky as the Sun, it becomes completely hidden from view from anywhere on Earth for about a day. After the new Moon phase, Earth’s celestial night-light will return to shine as a young crescent in the western evening sky.
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.