Welcome to the Ontario Parks “Eyes on the skies” series. This will cover a wide range of astronomy topics with a focus on what can be seen from the pristine skies found in our provincial parks.
October is a month of transition as the last few warm days depart and we prepare ourselves for winter.
But cold weather does not mean we should abandon the great outdoors. On the contrary, the peace and serenity found at this time of the year make a trip to any park all the more enjoyable.
Here are our astronomical highlights for October, 2024:
The sun
The sun continue to appear lower and lower in the sky as it drives toward its lowest point at the time of December’s winter solstice.
We now experience longer nights than days. While decreasing the amount of time for daylight activities, we can look forward to more time to appreciate the night sky’s splendours.
Here are the sunrise and sunset times for October:
| October 1 | October 15 | October 31 | |
| Sunrise | 7:24 a.m. | 7:43 a.m. | 8:07 a.m. |
| Midday | 1:15 p.m. | 1:13 p.m. | 1:09 p.m. |
| Sunset | 7:05 p.m. | 6:39 p.m. | 6:11 p.m. |
The moon
The moon has long captivated observers of all ages.
October’s lunar phases of the moon occur as follows:
The planets: the return of the three closest outer planets
Making a very quick appearance in the western sky at sunset is the planet Venus.
While normally a spectacularly bright object, Venus is very close to the sun and sets shortly after sunset.
Saturn rises before sunset, is due south around 11:00 p.m., and sets around 4:30 a.m.
Saturn is a spectacular object to observe in even the smallest telescope due to its prominent rings. However, this year, the planet’s rings are tilted in such a way as to make them difficult to see (see last month’s edition).
Jupiter begins to make what will be its best appearance for the next 12 years!
It takes Jupiter about 12 years to go around the sun. We see Jupiter at opposition (opposite the sun) typically around midnight, but if the sun is high in the sky during the day (such as during the summer solstice), an object that is opposite the sun will be at its lowest point (such as where Jupiter was about six years ago).
But if the sun is low in the sky (such as during winter solstice), then a planet in opposition (such as Jupiter is this December), will be at its highest point and further away from the turbulent air that often distorts planet images nearer to the horizon.
This is such a year and Jupiter, coming to opposition in December, will shine long and bright! For now (in October), it rises around 9:30 p.m. and is due south around 5:00 a.m.
Mars follows Jupiter a couple of hours later. It rises around midnight and is due south around 7:30 a.m.. However, Mars is far away from us at the moment and noticeably dimmer than when it is at opposition.
Comets, meteor showers, and satellites – possibly a bright comet!
Comets are notorious for avoiding prediction. Many times the public has been disappointed by what was supposed to be a spectacular comet or have been unaware of a spectacular comet (at least back in the days before social media)!
What we can say is that a comet that may become somewhat bright is rapidly gaining attention while rapidly closing in on the sun.
This comet – Comet C/2023 A3 (Tsuchinshan-ATLAS) is already visible to viewers best situated in the Southern Hemisphere, but in the second week of October (October 10-17) it may become quite visible low in the west at sunset as captured in these images generated from SkySafari Pro 7.0.
Our night sky seems to be a fixture of perfection. While the stars rise and set and the sun, moon, and planets do appear to move against the starry backdrop, little other changes are apparent. However, that stillness does get punctuated from time to time by ghostly interlopers – the comets!
A comet is a leftover from the formation of the solar system. Usually no more than 5 to 10 km in diameter, these “dirty snowballs” are composed of mostly ice and rocky material. As they near the inner part of the solar system, the sun’s heat begins to warm up the nucleus and the materials sublimates (goes from a frozen state directly to gas without passing through a liquid phase).
In this picture, the nucleus of comet 67P / Chuyumov-Gerasimenko can be seen sublimating into gas jets that release icy/dusty material away from the nucleus itself.
When we look at a comet from the Earth, we do not see the comet’s nucleus, but the shell of material released by the comet’s nucleus – the coma. A coma is, in essence, the localized atmosphere of the comet’s nucleus.
While comet nucleuses are quite small, the material left behind in the wake of its journey can stretch back over 100 million km. Sunlight, reflecting from this long chain of dust and gas reflects, is visible as the comet’s tail.
In detailed photos (such as the one taken by Killarney Provincial Park astronomer in residence Bill Gardner) two different tails can be seen.
The brightest is the “dust tail” composed of, as you might expect, largely dust and gas. It points generally away from the sun, but also is somewhat affected the speed and direction of the comet’s travel and often appears somewhat bent.
The ion tail tends to be blue in colour and always points directly away from the sun due to the effect of solar wind.
So what happens to a comet after it passes by?
Most comets are in long orbits around the sun that can take them far beyond the dwarf planet Pluto. Some of these visitors may be on a one-time pass through our neck of the woods, never to be seen again.
It is estimated that Comet C/2023 A3 (Tsuchinshan-ATLAS) will eventually travel so far away from the sun, on its return to the Oort Cloud, that it may completely leave the solar system altogether.
Interestingly, the dust that is left in the wake of the comet’s travels stays in orbit around the sun, following the same path that the comet did. Should the Earth encounter this material, it will burn up in our atmosphere and we call that a meteor.
So now you have the origin of the other item that we see that changes in our night sky – meteor showers. Comets are indeed the source for most of the meteor showers that we are privileged to see adorn the starry night sky best enjoyed from our provincial parks.
How to find Comet C/2023 A3 (Tsuchinshan–ATLAS)
There are many good sources and guides to help you find the comet. Here are but a few of those sources that are online:
- Comet Tsuchinshan-ATLAS: The comet of the year is here – Astronomy
- Can you see Comet A3 Tsuchinshan-ATLAS with the unaided eye? – EarthSky
- Update: Comet Tsuchinshan-Atlas Might Outshine Predictions – Sky & Telescope
Observing the comet
While you can easily see the comet with the unaided eye in dark skies, binoculars are probably your best optical tool to enjoy some of the comet’s details.
Meteor showers
Meteor observing, especially in the dark skies of our provincial parks, is one of the most enjoyable ways to get into astronomy.
You don’t need any special equipment other than your eyes! A lounge chair, sleeping bag, and a friend are all welcome additions to enjoying the spectacle. If you look at our constellation charts, you can practice learning your constellations while you watch for the meteors.
A meteor shower occurs when the Earth enters the debris field of a comet that has long ago passed around the sun.
These bits of dust and grit, often no bigger than your thumbnail, enter the Earth’s atmosphere and burn up high above the ground (see our post on meteor showers for more information).
This year, the Orionid meteor shower peaks on the night of October 21 and — once the moon has set — observers should may be able to see up to 20 meteors per hour before the moon rises!
Featured constellations
In last month’s edition we discussed Pegasus, Aquarius, and the southern fish – Piscis Austrinus.
In October’s featured constellations, we discuss the more popular northern fish (Pisces), Aries the Ram, and Triangulum the Triangle.
