September 2026 Stargazing Guide

Here we go.

Greetings, junior scientists, scientists, and citizens of this great big, weird, wild, and wonderful world in which we live. As always, I'm your humble science communicator, the great Orbax. Coming to you from the Department of Physics here at the University of Guelph, I'd like to welcome you to our September 2026 Star Gazing Guide.

Welcome back, junior scientists. As many of you have returned back to your studies, so too have the long autumn nights returned to us. Sunrise moves back from 6:43 a.m. on the 1st to 7:17 a.m. on the 30th. And sunset moves up from 7:56 p.m. on the 1st to 7:04 p.m. by the month's end. This leaves us with 12 hours of dark skies as we head into the autumn. So, what's happening up there and what should we be on the lookout for? This month, we learn a trick for spotting the North Star, transition seasons with the autumnal equinox, and find out the answer to our latest Martian puzzle.

All this and more when you just take some time... to look up.

As the summer draws to a close, we note how we've watched the rise of the Summer Triangle over the last few months. One of the stars I told you to watch, Deneb, is part of the constellation Cygnus, the swan, which is one of the best seen constellations this month.

It also contains the asterism known as the Northern Cross.

The Northern Cross appears only in the northern celestial hemisphere, hence its name.

But here's a trick for finding Polaris, the North Star, using the Northern Cross.

First, you'll need to clock Deneb. This should be easy since you've been studying the summer triangle for months now. Now, you need to zero in on Aljanah. Connect the two and extend the line from Aljanah to Deneb about five times its length, and you'll be at Polaris.

If you're having a tough time, use the trick I taught you previously about how to find Polaris using the Big Dipper.

Good luck, junior scientists.

Venus will be visible all month before darkness kicks in as the sun slowly sets with its greatest brightness in 2026 taking place on September 22nd.

Over the next few weeks, Venus will swap out of our evening skies and start appearing in our morning skies.

Mars, the planet of robots, will be up and visible in the early morning hours before dawn along with Jupiter with Saturn rising a few hours earlier and high and bright in the morning sky.

Our Full Moon this month takes place on Sept 26th and is known as the Harvest Moon, a name given to the Full Moon occurring closest to the autumnal equinox. Typically our September Full Moon would otherwise be called the Corn Moon.

The Anishinaabe peoples of the Great Lakes region refer to this Sept Moon as Waatebagaa-giizis - the “Leaves Turning Moon” while the Cree nation of central Canada honour the Moon with the bull moose's mating signal calling it Nimitahamowipisim, the “Rutting Moon”. The Mi’kmaw peoples follow a similar naming convention calling the Sept Full Moon Wikumkewiku’s – the Mate Calling Moon.

As I mentioned earlier September 22nd is the first day of autumn.

And here's why.

We all remember that the earth is tilted at 23.5° with respect to the line perpendicular to the plane of our orbit around the sun.

One earth year corresponds to one full solar orbit.

In December we talked about the winter solstice and in June we talked about the summer solstice.

The solstice occurs on that day when we're either closest to or furthest away from the sun based on that tilt. These are the days when we experience the most daylight hours or the least daylight hours. The two extremes.

Exactly halfway between the solstices, we experience equal daylight and nighttime hours.

This is known as the equinox.

The autumnal equinox occurs on the 22nd of September and denotes the first day of autumn. After this point, our daylight hours will decrease in length as we approach the winter solstice in December.

This phenomena occurs again in six months once we pass through 180 degrees through our orbit around the sun in the springtime for the vernal equinox.

Hello, greetings junior scientists. Welcome to my sanctum solarum here deep in the MacNaughton building at the University of Guelph.

Some of you may remember the headlines from a few years ago when a strange greenish yellow discovery on the red planet was all over the news.

Well, a few weeks ago, the cover of Science showed this discovery yet again with a theory of how this was formed by a Guelph Physics alumni.

I'm Scott VanBommel, a research assistant professor in the department of Earth, Environmental, and Planetary Sciences and a fellow of the McDonald Center for the Space Sciences at Washington University in St. Louis.

I am a graduate of the University of Guelph Department of Physics where I received a Bachelor's degree in 2010, Master's degree in 2013, and PhD in 2017.

So Scott, can you explain to us what all this excitement is about?

Yeah.

So back in 2012, Curiosity landed in the base of Gale Crater. It's this giant 150 km or so diameter impact crater. And since landing, we've been exploring from the base of the crater and then up this mountain that's in the middle of it. And part of the reason why this landing site was selected was because this mountain has various stratographic layers and you can kind of think of it like the rings of a tree. As we're climbing up this mountain, we're able to explore different eras in the history of Mars. So while we were climbing this mountain, we noticed a field of light tone stones off in the distance. And as we drove up to investigate them further, um, we actually drove over one of those stones and fractured it with one of the wheels of the rover. And when we deployed our spectrometers to these rocks, in particular, the Canadian built, designed, managed APXS, alpha particle X-ray spectrometer, we were able to determine through a combination of X-ray fluorescence and X-ray scattering data that these rocks were compositionally unlike anything that has been seen before on Mars and that they were pure sulfur.

So my understanding is that these native sulfur deposits only occur here on Earth through high temperature processes like volcanic activity and fumeroles or uh through sulfur reducing bacteria. Was it either of these two processes?

We did not see any evidence for high temperature processes. There's also no concrete evidence for life in the past on Mars and we certainly didn't see any evidence for it in the vicinity of the deposit. What we think could explain this deposit is that an ancient volcano on Mars  had an eruption. There was some sulfur rich gases that were trapped in the subsurface.

These gases were ultimately released from the subsurface, came up to the surface of Mars where they had a chemical reaction that produced pure sulfur and water. That water would have frozen into ice which ultimately protected these stones from the debris or dust being intermixed into them.

So native sulfur or pure sulfur is very easily converted to other forms of sulfur if the conditions are not right and one of those conditions is a very arid environment.

If you have them interact... if you have native sulfur interacting with water it will rapidly convert to other forms of sulfur.

So, the fact that we found this deposit and it formed roughly 3 billion years ago, we know that this deposit has not come into contact with water in 3 billion years.

Wow.

Incredible.

 3 billion years untouched on the surface of Mars until our robots drove over it.

Stay tuned over the next couple weeks for a longer format interview that we'll release with Scott.

And don't miss out on his paper in science.

So, there we have it. What an incredible universe in which to live. So much to learn, so much to explore, and so much to discover.

And it's all out there waiting for you if you just take some time...

and look up.

See you next month, junior scientists, and don't forget to have a science-tastic day.

Special thanks to Royal City Scienc's own planetary geochemist, Dr. Glynis Perrett, for her help in preparing our stargazing guide and the Royal Astronomical Society of Canada.