The Earth, Moon and Sun hold a final dress rehearsal before the debut of their long-awaited Montreal show in 2024.
A partial Sun
The astronomical highlight of October 2023 is the annular solar eclipse set to occur on the 14th—the last solar eclipse before the highly anticipated total eclipse on April 8, 2024. On October 14, we’ll be able to see a partial eclipse throughout almost all of Canada. In Montreal, the phenomenon will unfold between 12:12 p.m. and 2:24 p.m. EDT, reaching its maximum at 1:18 p.m., with the Moon covering 17% of the Sun’s surface and making it look like a large cookie with a bite taken out of it.
During an annular eclipse, part of the Sun remains visible as a ring of light around the Moon’s silhouette. But you have to be in the right place on Earth to see it, somewhere inside the path of annularity. In the case of the eclipse of October 14, 2023, this narrow corridor, no more than 245 kilometres wide, extends over 13,700 kilometres! It begins west of Vancouver Island, then travels from Oregon in the US to northeastern Brazil.
Why isn’t this eclipse total? Actually, total solar eclipses only happen because of an amazing coincidence between the size and distance of the Moon compared to the Sun: The Moon is 400 times smaller than the Sun, but approximately 400 times closer. This means that the two celestial bodies appear roughly the same size in the sky, allowing the Moon to perfectly block out the Sun.
On closer inspection, however, the orbits of the Earth and Moon are not perfect circles, but rather ellipses. Our distance from the Moon and the Sun varies throughout the month and year. As a result, the angular size of these celestial bodies in the sky is not constant: The Moon appears to be slightly smaller than the Sun about 63% of the time. When the celestial bodies align during these periods, the Sun “spills out,” so to speak, and the eclipse is annular rather than total.
Remember to use approved solar filters to safely observe the phenomenon! For more information, visit our website at espacepourlavie.ca/en/eclipse2023.
Evening giants
Saturn and Jupiter are both magnificently positioned for evening observation.
The beautiful ringed planet, Saturn, appears at dusk, between 15 and 20 degrees above the southeastern horizon; it culminates at 31 degrees in the south, around 10:30 p.m. in early October and 8:30 p.m. by month’s end. It’s the brightest point in this region of sky, much brighter than the stars of the constellation Aquarius, which it will pass through over a period of more than two years. The much faster waxing gibbous Moon approaches Saturn on the evenings of October 23 and 24.
As Jupiter journeys toward opposition in early November, it rises increasingly early after sunset. In fact, don’t miss your chance to see it rise on October 1 (around 8:30 p.m.) and on October 28 (around 6:45 p.m.), when the Moon looms just a few degrees over the planet at the time of conjunction—it’s definitely worth a look. Even that close to the full Moon, Jupiter’s brightness is impressive as it reaches its maximum magnitude for 2023 (–2.8) by month’s end.
If you can get your hands on a telescope, watch the ever-fascinating dance of the four Galilean moons, whose positions relative to Jupiter change from hour to hour. And like our Moon, they also cast their shadows on Jupiter. A double shadow transit will occur as of 2 a.m. on the night of October 19-20: For nearly two hours, we’ll be able to see the shadows of Io and Ganymede simultaneously cross the cloud bands in Jupiter’s atmosphere.
Venus, the Morning Star
Venus reserves its finest appearance of 2023 for early risers this fall. The planet never strays too far from the Sun as seen from Earth, since its orbit is closer to the Sun than ours. This year, the configuration of the planets on October 23 places it at its furthest distance from our daytime star (greatest elongation of 46.4 degrees), allowing it to gain more altitude (around 35 degrees) in a dark sky well before dawn. Blazing like a beacon after it rises above the eastern horizon at around 4 a.m., Venus steals the show from Jupiter, in the opposite direction in the sky, and invariably provokes shock and awe among many novice observers...
Clear skies!
