Caoimhín's Content

This is the 100 Subscriber Q&A special, so I’ll be answering a couple of questions viewers have submitted. It turns out, I really did only answer couple of questions, just two in this video, hence the “Part 1”, the second part coming Thursday will finish up. I ended up giving almost two answers to every question, so we’ll dig into those here. Although the next Q&A may be a while, feel free to submit more questions here, on YouTube or on Instagram. I will be doing more Q&A videos in the future and if you’d like to make them happen faster, all you need to do is subscribe to the YouTube channel so another milestone can be hit.

To begin, the first question is “What is my favourite fun fact about astronomy?”

I couldn’t help but differentiate a fun fact about astronomy from a fun astronomical fact. To start, eclipses, especially total solar eclipses, are associated with a pretty nice fact to do with space. Having a Moon that just perfectly blocks out the bright disk of the Sun, leaving the wispy glowing corona visible, on long but regular intervals, may be unique to us. Firstly, we need a Moon, no guarantee of that happening, as with Mercury or Venus. Secondly, that Moon needs to be exactly the right fraction of the size of the star, and exactly that fraction as far away. The Sun is 400 times as wide as our Moon, and the Moon is 400 times closer to us than the Sun. This is what makes them appear the exact same size when one is in front of the other. Even if you cover the first two factors, the Moon and the Sun need to line up. This is likely, especially if a planet is less tilted than the Earth, though it is less likely on highly inclined planets.

Uranus for example is completely tilted on its side. This means eclipses are pretty close to impossible on Uranus, at least for the vast majority of Uranus’ year, when its equator doesn’t line up with the Sun at all. If your pole’s are pointing at the Sun, the Moons around your equator couldn’t possibly line up with it. During the Uranian vernal and autumnal equinox when the equator is pointing towards the Sun, those moons could move in front of it. At the great distance between there and the Sun, some of Uranus’ moons will block it out, but not with a corona visible around the outside like on Earth, the Sun is pretty small and faint from Uranus, almost like distant star. For planets like Mars, with moons that are very very small, they’ll never block out the Sun completely, their eclipse will look more like a transit, just a small black dot crossing the Sun’s disk, or at best an annular eclipse.

With all of these factors, having a perfectly sized Moon at the perfect distance from the star, capable of lining up, it may be that these eclipses are rare in the universe as a whole. Even here on Earth, when the Moon was closer in the past, it would have blocked the Sun’s corona as well, and in the distant future when the Moon has spiraled further away, we will be left with only annular eclipses as well. It has been suggested that this phenomenon may be so rare in the Universe, if we want to catch aliens, we should be looking for them during total solar eclipses in case they came as tourists to see the spectacle. 

That’s got to be my favourite fun astronomical fact, but I also want to give a fun fact about astronomy, about the topic itself, the natural science of astronomy. Of course, I end up giving two, just how broad it is and how useful amateurs are.

With a lot of sciences, especially when you look at them at their most broad, things like chemistry and biology, they cover a lot. Biology covers everything from the smallest components of life, through to how they combine, first as cells and then collections of cells, right through to how populations of the interact and effect the land around them and even the climate. From biomolecules up to whole biomes, biology covers a lot. For simplicity of course it is broken up into smaller subparts, like zoology or biochemistry. As subjects like biochemistry demonstrate, the sciences do bleed together a little bit. This includes astronomy, with the well known astrophysics as well as astrobiology and astrochemistry.

Even without mixing it with different subjects, astronomy can be subdivided in numerous different ways. We can study the sky by looking at it, in observational astronomy, which is probably my favourite type and the oldest. By going out and finding things to look at, charting their progress across the sky, new things can be discovered. On the other hand, you can sit down and study the maths and physics, like the orbital dynamics behind moons orbiting planets, and discover things without ever looking at the sky in theoretical astronomy. It’s an incredibly broad and varied science, with a variety of subjects and disciplines. This leads to the many ways that you can study it or contribute to the science. For example, if you look up in a dark countryside sky, free of clouds or light pollution, you should see 2500 or so star is visible. Personally, I can’t keep track of exactly which ones are where, and if a new star was introduced between one night and another, there’s a good chance that I wouldn’t even notice it. However, some people can and discovering transient events like this, supernovae and even comets, this part of astronomy still gets a lot of help from ordinary people. By going outside, looking at the sky regularly and becoming familiar with it themselves, people have discovered things like comets and supernovae, as amateurs, before any of the big observatories with telescopes. Even without a perfect sky, measuring things like light pollution is something you can do and help with. If you want to know if your sky is as clear and as beautiful as this countryside sky, well you can go and you can look, you can make comparisons between the number of Pleiades you can see and how many you should, or haw much of Orion is visible. By submitting your information at to one of various sources, you can contribute o the citizen science of astronomy. It is one of the best sciences to be an amateur in, you can still discover things, you can still contribute, even if the way you do so is just look at the sky. Even as as a hobby in your spare time you can still make an impact and that’s probably my favourite fun fact about the discipline of astronomy.

Another question that I got was “What is something that people get wrong about the Solar System?”.

I think there’s two things that people often get wrong about the Solar System. One of them is pretty simple, and it is sort of a trick question. It is where the middle is, the middle of our solar system is not in the middle of our Sun. The Sun is huge and it Sun dominates the solar system in terms of gravitational influence. Everything orbits around the Sun and really most other things don’t have much of an effect on the Sun. If the Earth disappeared it wouldn’t really change how the Sun moves. However, if Jupiter disappeared it would. Jupiter and the Sun really share a co-orbital point, the barycenter. They both orbit a point in between the Sun’s center of mass and Jupiter’s. Really this is true for the whole solar system, but because Jupiter is so so massive the barycenter between Jupiter and the Sun isn’t directly in the middle of the Sun, it’s pulled a little bit to the side. This means that the Sun does wobble around just a little bit as the planets orbit it, dragged by Jupiter. Most other planets have their barycenter with the Sun very close to the Sun’s center of mass. Jupiter is so incredibly massive compared to everything else in the Solar System, even compared to Saturn, that it has a noticeable effect on what the center of the solar system really is. This little detail is normally left out of simulations of the solar system moving, so even though it’s not a secret, it is easy to forget and a great trick question for a quiz. The middle of our solar system is really the barycenter of Jupiter and the Sun, not the center of the Sun itself.

Another thing that many people mistake about the solar system is that our system is normal or average or typical in some way. This is less a of a trick question and more an assumption. The more we learn about other solar systems the more we see that there seems to be a great variation in how solar systems are shaped, how big they are and what kind of planets they have. We’ve also noticed some very big differences between what we’re discovering in most other solar systems and what we see in our own solar system. If we look at the orbits of planets in the solar system, they are definitely elliptical, they are not truly circular. However, the difference isn’t big, the planets’ orbits are not very eccentric. Venus has a very close to circular orbit, it’s barely eccentric at all. In other solar systems, it seems typical for planets to be quite a bit more eccentric, with far less circular orbits than in our solar system.

Outside the major planets, smaller objects, things like Pluto and other dwarf planets, as well as comets, have often very eccentric orbits. Even having a large group of major planets doesn’t seem to be typical. We don’t see that many big solar systems like ours with eight or nine planets, and very often we don’t see as much of a variety, with a few rocky and a few gassy planets. Many solar systems seem to only have one or two planets, and may have only rocky or only gassy. The large number we have may keep inner object more stable, while outer objects like Pluto are more eccentric. While it was considered a planet it was considered the most eccentric planet, in fact Pluto’s orbit passes inside the orbit of Neptune for part of its journey around the Sun. It’s so eccentric that even though on average it is further from the Sun than Neptune, it’s orbit is so squished it sometimes closer to the Sun than the path Neptune takes.

There are extrasolar planets that aren’t eccentric, but these are usually tidally locked, stuck facing their Sun with the same side all the time, like our Moon does for us. For a long time people thought that Mercury was tidally locked, but it turns out that it’s not. Mercury does in fact act spin around and there is a previous video on it’s strange path around the Sun, it is odd, but not tiaddaly locked. No planet in our solar system is, though we see it often in exoplanets.

I’m sure you can see why we’re going to have a two-part 100 Subscriber Q&A special, It took me 10 minutes to answer two, so I will deal with three more in the next part, coming out this Thursday. If you would like to submit questions you absolutely can, as a comment right here or on YouTube, you can also go through Caoimhín’s Content on Instagram. I hope that you liked these answers and that I’ll see you here for the next set.