Thebacha and Wood Buffalo Dark Sky Festival August 2017

This Week’s Sky: June 19 – 26

Saturn is up all night and the Moon visits Venus.

Saturn Low in the South by Manuel Guerrero

Despite the planet’s low altitude, Manuel Guerrero was able to obtain this nicely detailed photo of Saturn from Baden, Ontario (latitude 43.4º north) on June 29, 2016.

All Week

The view facing south-southeast, one hour after sunset.

The view facing south-southeast, one hour after sunset.

Two planets dominate the evening sky at the moment—one is in its prime, the other slowly losing ground to twilight. The one slipping away is Jupiter. Shining at magnitude –2.1, Big Jove is the brightest light at dusk and sits roughly 35 degrees above the south-southwest horizon an hour after sunset. (Its exact altitude depends on your latitude—the farther north you are, the lower the planet appears.) Even though Jupiter is long past opposition, it’s still higher up during twilight than Saturn gets at any point in the night. That’s because Saturn is positioned far south on the ecliptic. When the zero-magnitude ringed planet reaches the meridian a little before 1 a.m., local daylight time, it’s 10 degrees lower than Jupiter was in the early evening. The final planetary offering is magnitude –4.3 Venus, which clears the eastern horizon around 3:15 a.m. By the time the Sun rises, the brilliant planet has climbed to an altitude of around 20 degrees—it, too, nearly matches Saturn’s height when it culminates.

June 19

Shadow transit

The double-shadow transit in progress, as seen in a large telescope at high magnification.

Observers in Eastern Canada get to enjoy a double-shadow transit on Jupiter starting at 10:05 p.m., EDT. The event begins when Europa’s shadow joins Io’s, already making its way across the Jovian disc. The double-transit wraps up when Io’s shadow egresses Jupiter, approximately half an hour later.

June 20

The view facing due east, one hour before sunrise.

The view facing due east, one hour before sunrise.

This morning, a thin crescent Moon and Venus rise together. The lunar disc will sit a little less than eight degrees to the right of the beacon-like planet. The twilight duo will make a fine, naked-eye sight.

June 21

At 12: 24 a.m., EDT, the solstice occurs, marking the official start of summer in the northern hemisphere.

June 22

The Moon just before it occults Aldebaran, as seen in a small telescope from Toronto, Ontario.

The Moon just before it occults Aldebaran, as seen in a small telescope from Toronto, Ontario.

This morning, most of Canada will have the chance to watch an extremely thin waning crescent Moon occult Aldebaran in daylight. You’ll need a telescope (preferably one with a GoTo mount) to see the Moon’s bright limb eclipse the star. The farther east you’re located, the higher the pair will be during the occultation. Here are the approximate times for the star’s disappearance and reappearance at several Canadian locations: Halifax, Nova Scotia (11:06 a.m – 12:19 p.m., ADT); Montreal, Quebec (9:51 a.m. – 11:04 a.m, EDT); Toronto Ontario (9:41 a.m. – 10:53 a.m., EDT); Winnipeg, Manitoba (8:38 a.m. – 9:33 a.m., CDT); Regina, Saskatchewan (7:37 a.m. – 8:23 a.m., CST); Calgary, Alberta (7:39 a.m. – 8:12 a.m., MDT; Vancouver, British Columbia (6:38 a.m. – 7:02 a.m., PDT).

June 23

New Moon occurs this evening at 10:31 p.m., EDT.

Weekend Stargazer

Saturn and its five brightest moons as they appear at 1 a.m., EDT, Saturday morning.

Saturn and its five brightest moons as they appear at 1 a.m., EDT, Saturday morning.

Short nights over the June 23 – 25 weekend don’t lend themselves to in-depth deep-sky observing, so why not give in to temptation and have a look at Saturn? The ringed planet was at opposition on June 15, and is visible all night long.

What does Saturn offer telescope users? Rings, obviously—that’s what Saturn is famous for. And this year is a particularly good time to view them. Saturn’s north pole is tilted nearly 27 degrees Earthward, which means the rings are fully open and at their best. But don’t neglect the planet’s brightest moons. Although most telescope user make a point of following the comings and goings of Jupiter’s four Galilean satellites, I’m struck by how rarely those same observers deliberately view Saturn’s moons.

Titan is the one you’re most likely to spot first. It shines gamely at magnitude 8.4, and is usually the brightest point of light near the planet. But if you have an 8-inch scope, you could see as many as four additional satellites, including Rhea (magnitude 9.7), Tethys (10.3), Dione (10.4) and Enceladus (11.8). You can find their current positions in the RASC’s Observer’s Handbook or with this handy on-line calculator.

Saturn is second only to Jupiter when it comes to hoarding moons. At last count, Saturn lays claim to a mind-boggling 62 satellites ranging in size from 5,149 kilometres (Titan) down to jagged moonlets smaller than Mount Everest. Unfortunately, apart from the five already mentioned, this bountiful harvest of satellites lies beyond the reach of backyard telescopes.

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