Space, Stargazing

Stargazing 101- The Gas Giants

Recently, we had a weekend of 3 beautifully clear nights in a row, and I managed to convince my dad to drive up the hill with me for a better look at Jupiter and Saturn. It was the first time I had ever observed the two through a telescope successfully, and I definitely caught the astronomy bug (even more than I already was!), and got my telescope out the next two nights as well, this time from my back garden! It was a totally different experience, and you can see the vlog of the first night up on my youtube channel this evening!

The first thing we looked for was Jupiter, as it was highest in the sky and brightest (as it is both bigger than the saturn and closer to the sun- ooo I’ve just learnt the maths for this, maybe I’ll do a blog post on that next!). It was breathtaking, stunning, awe-inspiring… all the adjectives! Or perhaps it was simply ~out of this world~ (sorry for the pun it was just too perfect a moment). It was amazing being able to see not only Jupiter, but also its 4 closest moons (and a nearby background star which I initially thought was a 5th moon): Io, Europa, Ganymede and Callisto. To start with, I thought that the order of the moons from Jupiter was also the order I saw them down the telescope, but upon checking on stellarium this morning, that wasn’t actually correct! This is because the moon’s have circular orbits, and from 619 million km away, depth is dificult to percieve, so a moon that is actually further from Jupiter may seem to be the closest, if it is about to duck in front or behind the planet (and thus being hidden from view). This is more clear if you look how the order changes over the 3 days of observation. So, keep reading to see some stunning (if I do say so myself) images of Jupiter and its moons through my telescope, followed by the labelled order of the moons via stellarium!

Observation 1a

10/7/20, ~ 22:50

I love this one as you can actually see detail on Jupiter! Look for the 2 parallel horizontal lines

Observation 1b

I couldn’t help but get another look before we left so:

10/7/20, ~ 23:40

You can see here that Io has moved ‘further away’ from Jupiter from our perspective, even in just the hour between the two shots! (oops terrible quality though)

Observation 2

11/7/20, ~23:35

24 hours later, Io is completely round the other side, and Europa is just peaking around behind Jupiter next to Io

Observation 3

12/7/20, ~23:45

Another 24 hours later, Io is back where it started, and Europa is completely on the other side! Ganyemede and Callisto have only moved slightly.

So, you can easily see that the order of the moons varies greatly day to day, as they orbit fairly quickly, at least for the inner ones! And although I took them at slightly different times, a few minutes only really makes a difference for Io, Jupiter’s closest moon, as you can see between the shots at the start and end of the first night! Callisto however, has hardly moved across the 3 days, as it is the outermost Galilean Moon.

Table of Interesting Values

You can see from the orbital period of Ganymede, Europa and Io that they are in orbital resonance, which prevents their orbits from becoming circular, creating tidal heating that warms Europa’s ocean and makes Io so volcanically active!

These are called the Galilean moons as their discovery is attributed to Galileo. However, Simon Marius also discovered them independently at roughly the same time, though published his results after Galileo, but there is some uncertainty as to who actually observed them first. However, it is Marius’ names for each moon that we use today.

I also observed Saturn for the first time, and seeing its rings in full glory was magnificent! Here are my best photos of it.

Unfortunately, I could not find any moons, although technically I should have been able to. I think it was because I was looking closer to the rings, when the largest ones actually orbit a bit further out.

Make sure you check out my first vlog detailing Observations 1 & 2, and I will upload the second vlog next week. And keep an eye out for another blog about the Moon and Mars!

Stay Curious!


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