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.
Monday, October 17 – Third Quarter Moon (at 17:15 GMT)
The moon will complete three quarters of its orbit around Earth, measured from the previous new moon, on Monday, October 17 at 1:15 p.m. EDT and 10:15 a.m. PDT or 17:15 GMT.
At the third (or last) quarter phase the moon appears half-illuminated, on its western, sunward side. It will rise around midnight local time, and then remain visible until it sets in the western daytime sky in early afternoon. Third 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 dark, moonless evening skies that follow this phase are the best ones for observing fainter deep sky targets.
Tuesday, October 18 – Half Moon approaches the Beehive (pre-dawn)
During the wee hours of Tuesday morning, October 18, the waning crescent moon will be climbing the eastern sky above the faint stars of Cancer. The moon’s easterly orbital motion (green line) will steadily carry it closer to central Cancer. Towards dawn, the moon will shine binoculars-close to Cancer’s large open star cluster, which is known as Messier 44 or the Beehive. To see the cluster’s swarm of stars, which span more than twice the moon’s diameter, hide the moon just above your binoculars’ field of view (green circle).
Tuesday, October 18 – Juno reverses course (all night)
On Tuesday, October 18, the westward motion of the main belt asteroid designated (3) Juno will slow to a stop as it completes a retrograde loop that it began in late July. After tonight it will resume eastward prograde motion through the stars of central Aquarius. The magnitude 8.6 minor planet can be spotted in binoculars (green circle) and any telescope. This evening it will sit partway up the southern sky between Jupiter and Saturn, within a triangle formed by the medium-bright stars Lambda, Tau, and Sigma Aquarii.
Wednesday, October 19 – Two shadows and the Great Red Spot cross Jupiter (17:20 to 19:00 GMT)
From time to time, observers with good telescopes can watch the small, round and black shadow of one of the Galilean moons slip across Jupiter’s disk. On the evening of Wednesday, October 19, sky-watchers across Africa, Europe, and Asia will be able to see a rare treat when two shadows cross the southern hemisphere of Jupiter, together with the Great Red Spot!
At 7:19 p.m. Central European Summer Time or 17:20 GMT, the Great Red Spot and the small shadow of Europa will join the large shadow of Ganymede, which began its own crossing of the planet an hour earlier. Ganymede’s shadow will leave Jupiter around 9:00 p.m. CEST or 19:00 GMT, leaving Europa’s shadow to continue on until 9:45 p.m. CEST or 19:45 GMT.
The Great Red Spot will disappear about 45 minutes later.
Thursday, October 20 – Crescent Moon occults bright star Eta Leonis (pre-dawn)
In the eastern sky on Thursday morning, October 20, observers across most of the continental United States and southern Canada can use binoculars (green circle) and backyard telescopes to see the crescent moon occult the bright star Eta Leonis. The star marks the chest of Leo, the Lion.
Exact timings will vary by location, therefore using an app like Starry Night to determine the precise times can prove useful.
In Denver, the bright, leading edge of the moon will cover Eta Leonis at 4:58 a.m. MDT or 10:58 GMT. The star will emerge from behind the moon’s opposite, dark limb at 6:14 a.m. MDT. In more easterly time zones, the event will occur in a brightening sky before sunrise.
For best results, start watching a few minutes ahead of each time noted.
Friday, October 21 – Orionids meteor shower peak (pre-dawn)
The annual Orionids meteor shower is produced when the Earth crosses through a cloud of small particles dropped by repeated passages of Comet Halley in its orbit.
Viewed in a dark sky during the peak of the shower, 10 to 20 bright and fast-moving meteors are usually seen each hour. Although this shower technically runs from September 26 to November 22, it will peak in the Americas on the afternoon of Friday, October 21, when Earth will be crossing the densest region of the particle field.
Since meteors are only visible in a dark sky, the best viewing time for the United States and Canada will be the wee hours of Friday morning before the waning crescent moon rises, and late on Friday night. Those shoulder-peak times will yield somewhat fewer meteors.
Orionids meteors will appear anywhere in the sky, but they can be traced back to their radiant in the constellation of Orion.
Friday, October 21 – Old Crescent Moon near Ceres (pre-dawn)
During the hours before dawn on Friday morning, October 21, look in the eastern sky for the old crescent moon shining prettily. The dwarf planet Ceres will be positioned several finger widths to the upper left (or 3 degrees to the celestial north) of the moon — close enough to share the view in binoculars (green circle). With a magnitude of only 8.84, Ceres will be seen more easily in a backyard telescope. The somewhat brighter stars HIP 53881 and 52 Leonis can assist in your search.
Saturday, October 22 – Saturn pauses close to star Iota Cap (evening)
On Saturday night, October 22, Saturn’s westward retrograde motion through the stars of central Capricornus will slow to a stop as it completes a retrograde loop that it began in early June.
This evening, Saturn’s magnitude 0.6, yellowish dot will appear in the lower part of the southwestern sky, shining less than a finger’s width to the upper left (or 0.6 degrees to the celestial northeast) of the bright star Iota Capricorni — close enough to share the view in a backyard telescope (green circle).
As Saturn resumes its regular prograde motion in the coming weeks, it will widen its separation east of that star.
Sunday, October 23 – Morning zodiacal light for mid-northern observers (pre-dawn)
During the autumn period at mid-northern latitudes every year, the ecliptic (green line) extends nearly vertically upward from the eastern horizon before dawn. That geometry favours 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 November 8, look for a broad wedge of faint light extending upwards from the eastern horizon and centred on the ecliptic. It will be strongest in the lower third of the sky, below the bright star Regulus.
Try taking a long exposure photograph to capture the zodiacal light, but don’t confuse it with the Milky Way, which is positioned nearby in the southern sky.