Caoimhín's Content

Today we are going to be taking a look at a quasi-satellite of the Earth. In previous pieces we have taken a look at other quasi-satellites or semi-satellites. They may be called temporary moons or semi-moons, they are given various names even though generally they are not moons in a strict sense. We have already taken a look at Kamo’oalewa in a previous piece, that is one of Earth’s quasi-satellites. It is in an orbit around the Sun that keeps it reasonably close to the Earth and it does move in front of and behind the Earth over time, but it’s not really orbiting us, it’s just orbiting the Sun about the same distance.

We are going to be taking a look at a different object today, which is apparently not in Stellarium by default, but that is okay. We can add objects to Stellarium using the Solar System Editor. The Solar System Editor is a Stellarium plugin. If you take a look at the configuration window, the wrench symbol in the left tray menu, it has a plugins tab. There various different ones you can select, the Solar System Editor, is near the bottom of the list. If you click on it, a description will come up and a small checkbox at the bottom. If you want to use it, you will need to tick this checkbox and then restart Stellarium. Once done, it will load on startup and can be found in the Solar System Objects tab of the Sky and Viewing options menu.

You can add anything you want, but we’re not adding a made up object. I am going to be adding in an object that already exists, so I don’t need to know the orbital parameters. I just need to go and find the orbital parameters on the Minor Planet Center’s Minor Planet and Comet Ephemeris Service. This is found at the bottom of the Solar System tab of the editor. It will bring up a search window that searches a database that has all of the orbital parameters. You will need an internet connection, but each entry has all of the details necessary for adding these objects to Stellarium. Unfortunately you do need to be careful with your spelling. We’re importing 2023 FW13. It was discovered in 2023 by the Pan-STARRS Observatory in Hawaii. Once the object you’ve searched for comes up, you select it and add it to Stellarium. If we bring up our search window, it will be there already.

This object is simply listed as an asteroid, and that is what it is. This is an asteroid, but it tends to follow the Earth over the course of the year. If we move through a little bit of time, we’ll get rid of the ground and the atmosphere, we’ll get an idea of where it is. It looks like it’s coming into a position between us and the Sun at the moment, it will be between us by January. Over the course of the year, it will end up behind us just like a Moon would. If we go the whole way through the year, it comes back around, back in front of the Sun. It certainly doesn’t take the month that our Moon takes but it does seem to be moving around us. It is going behind us and in front of us in a way that none of the planets do. Mercury and Venus are always closer to the Sun than we are, all of the other planets are further from the Sun than we are, but this asteroid and our Moon can go between us and the Sun as well as being behind us relative to the Sun.

Taking a closer look at it, its magnitude is at 28.44 while it is pretty much in front of the Sun. We’ll move back in time to get it into a more favorable position behind the Earth relative to the Sun. With the Sun on the opposite side of the sky, that brings its magnitude up to 22, which is still incredibly faint. This is still going to be a faint object, a tough one to see, even at its brightest. We’ll come around until it is coming back around to being pretty much in front of the Sun, and it drops to just 31st magnitude. It looks like this orbits around us once a year, but of course, it’s not actually orbiting us. It is moving around us while also traveling around the Sun, but technically, it is outside of our gravitational pull. It just happens to be moving around the Sun at roughly the same distance as we are. Currently it’s about 52 million kilometers away from us, significantly further away than our Moon at just about 370,000. If we take a look at it from the solar system observer, we should be able to see just how far away it gets.

The solar system observer is a viewpoint where we are looking down on the solar system. We’ll grab onto the asteroid 2023 FW13 again, and we’ll zoom in. I am going to try to bring up the orbits of these objects, we’re only looking at the inner solar system, so there shouldn’t be too many extraneous orbits displayed. Even set only for the selected object, I am not getting an orbit, Stellarium is not bringing up any lines showing its path around the Sun. Even zoomed in, it’s not visible. There is no image being provided by Stellarium. Stellarium will display the orbits of the planets, which will help us to figure out where this object is relative to the Earth. By following it through a little bit of time, its motion will be apparent. It moves in front of the Earth, outside of the Earth, and then falling back again, behind the Earth and inside of our orbit.

As we move through time, the asteroid drops inside the Earth’s orbit. It comes between us and the Sun while moving back towards the Earth and then ends up outside of the Earth after crossing in front of us. From outside of our orbit it then falls behind us. As it falls behind us, it will eventually drop down inside of our orbit again. This happens roughly once a year. It looks like it’s outside of us in April every year and then it drops back in and it should get between us and the Sun by January. Moving back a little bit, the asteroid gets pretty close to the orbit of Venus while it’s inside of the Earth’s orbit and as we move back further, it gets almost halfway between us and Mars. The orbit of this object is very far removed from the Earth.

Just as it crosses in front of us, around February-March, is when it’s at its closest to the Earth, but it is still quite far away. If we start zooming in, the Moon will eventually get revealed and I don’t know if Stellarium will even be able to display the asteroid and the Moon in the same field of view. It can, just barely. This view makes it clear that the Moon is much closer to the Earth. Even if we move through a few days and get the Moon in a position where it seems nice and far from the Earth, this asteroid is still significantly further away. again, this is about as close as this asteroid ever gets to the Earth. It’s not really a moon, it is is however a long term companion of the Earth. This asteroid is, based on its orbital parameters, very stable and it is likely to stay moving around the Earth for quite some time, varying almost out to the orbit of Mars, almost in to the orbit of Venus, but always crossing back over Earth’s orbit. This asteroid is thought to have been with us since 100 BCE, and it should stick around until 3700, almost four thousand years at least. It’s more stable, it is a more long term companion of the Earth, than the Kamo’oalewa asteroid that we have looked at previously.

That is 2023 FW13. It does not have a common name that I’ve been able to find, even though it is a long term follower of the Earth. There is a good chance that, due to its smallness, its distance from the Earth, and the difficulty in actually observing it, it may not get a common name, a more normal name than the set of numbers and letters it currently has. I hope that you’ve enjoyed reading about how it moves and how we see it in the sky, or at least how we would see it if we could see it. If you did enjoy this piece, then please do like it. If you enjoy this kind of content, then please subscribe to this website and my YouTube channel. Thank you very much for reading and hopefully I’ll see you back here next time.