Jasper Dark Sky Festival

This Week’s Sky: October 17 – 24

A dwarf-planet opposition and Aldebaran occultation.

Joe Bonner captured this scene of the crescent Moon and Venus (and a flock of Canada Geese) from Manotick, Ontario, on October 3, 2016. As autumn progresses, Venus is becoming easier to see.

Joe Bonner captured this scene featuring the crescent Moon and Venus (and a flock of Canada geese) from Manotick, Ontario, on October 3, 2016. As autumn progresses, Venus is becoming easier to see.

All Week


The view facing south-southwest, 45 minutes after sunset.

For planet watchers, the evening sky presents a good news/bad news story. The good news is that Venus is slowly climbing higher and is now easy to find low in the west at dusk. The evening “star” blazes away at magnitude –3.9, which means you can spot it shortly after sunset. The bad news is that Saturn is nearly done for this apparition. The ringed planet hangs just 10 degrees above the southwest horizon as twilight fades. For Mars, our third planet, the news is mixed. Shining at magnitude 0.3, Mars is still bright enough to attract naked-eye attention as it drifts eastward through Sagittarius, but it long ago ceased to be much of a telescopic target. Perhaps the best news is that Jupiter has resurfaced in the morning sky following its September 26 solar conjunction. Shining at magnitude –1.7, Big Jove rises more than 1½ hours before the Sun. However, another month or so will pass before before Jupiter looks good in a telescope. (It will be worth the wait!)

October 19


Aldebaran as it appears in 10×50 binoculars moments before it’s eclipsed by the Moon.

This morning the waning gibbous Moon occults Aldebaran for observers in eastern Ontario, Quebec and the Maritimes. Unfortunately, it’s the bright limb of the lunar disc that covers the star, which is less dramatic than a dark-limb occultation. None the less, the event will be worth viewing in binoculars or a small telescope. From Toronto, Aldebaran disappears at 1:47 a.m., EDT, and reappears at 2:37 a.m. From Montreal, these events occur 10 minutes later (1:57 a.m. and 2:47 a.m.). For observers in Halifax, Nova Scotia, the occultation begins at 3:05 a.m., ADT, and ends at 4:08 a.m. Sky watchers farther west than central Ontario will simply see the Moon pass very near the star.

October 20/21

The Orionid meteor shower peaks tonight. Unfortunately, a bright waning gibbous Moon will make seeing any sign of this modest shower difficult.

October 21

Dwarf planet Ceres reaches opposition today and is at its brightest for 2016. (For more, see Weekend Stargazer, below)

October 22

Last quarter Moon occurs at 3:14 p.m., EDT.

Weekend Stargazer


Use this chart to locate Ceres this weekend. The shaded circle indicates the field of view in 10×50 binoculars. (Click on the chart for a full-size version.)

Here’s a riddle for you: What solar system object has been a comet, a planet, an asteroid and a dwarf planet? The answer is Ceres. When Giuseppe Piazzi discovered Ceres in 1801, he originally believed he’d found a comet. Later, Ceres was thought to be the long-searched-for planet expected to circle the Sun between the orbits of Mars and Jupiter. When similar “planets” started turning up in the same zone, astronomers realized they’d stumbled across a whole new class of solar system object. These bodies were called “minor planets” or “asteroids.” And Ceres remained categorized as such until 2006, at which time it was reclassified as a “dwarf planet.” So, take your pick. You can think of Ceres as being the biggest asteroid, or the nearest dwarf planet. Either way, Ceres comes to opposition and reaches peak brightness early in the October 21 – 23 weekend.

At the moment Ceres appears as a 7.5-magnitude point of light in the constellation Cetus. Your best route to it is to scan roughly four degrees south of alpha (α) Piscium. (Use the chart above to locate the field.) How can you be sure you’ve located the dwarf planet and not just a field star? By using the same method Giuseppe Piazzi used. Note your suspect’s position over a period of two or three nights. If it moves, you’ve found Ceres.

At SkyNews we love to read about your experiences and see your photos. You can share them with us by e-mailing skynews@skynews.ca.

Categories: This Week's Sky
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