Day 549 – Jupiter

There is an entire internet’s worth of information out there if you know where to look. There’s actually no excuse for not knowing stuff now if you have a device and a connection. Look at Friday evening for example.

There, up in the Eastern sky (near the top) was Jupiter. I knew this because I’d wondered what the shining star in the East was over the weekend, and I’d looked it up, before looking up at it.

As a bit of a demo, we got the tripod out, aimed and shot, hoping to get the four Galilean moons in the picture. It’s a quick and dirty image: I suppose I could have Googled for the best settings for this sort of thing, but as I say, this was a quick post-braai thing, and – much as I knew that the moons might be there – I picked the settings from my experience, rather than finding a site on the net.

Here’s what we got:

It’s not going to win any awards, other than maybe the one for demonstrating the four Galilean Moons of Jupiter to a few kids (and a couple of adults) after an early evening braai.
If I had tried harder or had more time, I could have done better, but that’s really not this was about. This was “That one there is Jupiter. Let’s see if we can see its moons and then get back to standing around the fire before I fall asleep.”

But then come the questions: How far away is that? How long will the light take to reach us? Which moon is which?

I can do a medium-rare rump over the coals and I can manage some functional camera settings, but I had to turn to the internet for these answers.

Currently, (current to when this was taken) Jupiter was 627.85 million kilometres away. That’s over four times the distance to the sun. I did a rudimentary calculation and that means that with light traveling (as it does) at 300000km per second, the light from Jupiter takes 35 minutes to get to us.
We’re essentially looking at a snapshot of Jupiter as it was just over half an hour ago.

But which moon is Io, or Europa, Ganymede or Callisto?
Well, surely there isn’t a site that can tell you that for any given moment?

Of course there is.

All I had to do was to pop in the date and time that the image was taken, allow for our longitude, and make sure they knew I was using an Erect System (stop it).

So, from the top down on our photo are: Callisto, Europa, Io, Jupiter and Ganymede. All taken from a well-lit suburban back garden, with a basic camera and lens, and all informed by the internet.

It’s not just there for being shouted at by anti-vaxxers.
Some of it is quite useful.

Look at the stars…

Please hold thumbs, cross fingers and make sacrifices to your given deity that we get some clear skies this evening.

If all has gone well (yes, I wrote this last weekend), we’ll be in famous (and infamously chilly) stargazing location, Sutherland, and I’ll definitely by braving the sub-zero temperatures tonight, assuming there aren’t any clouds between me and the sky.

So if you’re happy for your favourite blogger to risk hypothermia in order that I can try to create something beautiful, pray for a cloudless sky, and I’ll promise to share any results once we’re back just 6000 miles from civilisation…

Stay warm, folks.


There was a partial lunar eclipse this evening. Obviously, I took some photos.

I would have taken more photos, but the camera settings had been altered by Mrs 6000 while she was in Russia, and made little or no sense. I think I was lucky to get anything. I’m going to have to try and sort something out before I use the camera again, but a factory reset might just be the easiest route.

Partial lunar eclipses are arguably amongst the least exciting of all astronomical phenomena, but when you consider what they’re up against – stuff like comets and space stations and meteor showers –  they never really stood much of a chance.

Partial Lunar Eclipse’s big brother, Total Lunar Eclipse, has promised to pop in next July.

Solar System Distances

Here’s a useful Solar System resource for you:

Average distances of the planets from the sun; Total distance traveled in one complete orbit by each of the planets; Total time for one complete orbit of the sun (one planetary year).

OBJECTDistance from Sun (average) in kmDistance traveled in one complete orbit of the Sun in kmAmount of time for one complete orbit of the Sun
Mercury59,221,114359,993,5633 Earth months.
Venus108,142,903679,916,3187 Earth months.
Earth149,662,053939,813,3251 Earth year
(365.25 days)
Mars227,872,5461,429,031,22023 Earth months. Almost 2 Earth years.
Jupiter778,242,6784,887,351,143142 Earth months. Almost 12 Earth years.
Saturn1,426,617,3168,957,032,507354 Earth months. 29½ Earth years.
Uranus2,870,453,81418,025,909,2371009 Earth months. Over 84 Earth years.
Neptune4,498,229,80428,262,471,8381979 Earth months Almost 165 Earth years.

Working on a school project, we needed these figures. Plenty of copies of this information are available, but all of it was on US sites and all of it was in miles. Want it in kilometres? Well, either you have to do it yourself (like I did) or (now) you can use the table above.

Happy to help.


I was alerted to an animation by this tweet:

If the Moon were only a few hundred km away, it would look AMAZING… but you’d be way too dead to notice.

An animation artist has arted an animation of what it would look like if the moon were about 420km above the earth’s surface. That’s about the same altitude as the International Space Station. And yes, it does look amazing:

Here’s the cool stuff:

If the Moon were that close — 420 km (260 miles) over the surface of the Earth — it would be over 100º in size, literally more than half the sky! Right now it’s a mere 0.5º in size, for comparison.
It’s dark in the middle because with the Moon blocking the Sun for so much of the Earth, there’s no light to reflect and illuminate the Moon there!
The motion in the video is sped up; at that distance the Moon would orbit the Earth in about 90 minutes or so. It would cross the sky in very roughly five minutes.

And here’s the kinda weird bit:

The Earth has about 80 times the mass of the Moon, so if you could situate yourself exactly halfway between them, the Earth would pull on you 80x harder than the Moon. But it’s worse than that; gravity drops as the square of the distance, and the Moon is pretty far away. Right now, the center of the Earth is roughly 6400 km below you, and the Moon’s center is about 380,000 km above you. Take the ratio and square it, and you see that the Earth pulls on you 3500 times harder just because it’s closer. Add in the fact that the Earth is more massive, and you’ll find it pulls on you about 300,000 times harder than the Moon!
That’s why you don’t notice the gravity of the Moon. It’s only 0.0003% as strong as what you feel from the Earth.

But if the moon were 420km away,and you redo the gravity calculation, you’d find the force of gravity from the Moon on you is 1/10th that of Earth!
When the Moon passed overhead, you’d weigh 10% less.

Weight Watchers paradise.

But sadly, that’s where the good news ends. Because tides.

If we bring the Moon in really close, suddenly one side of the Earth is a lot closer to the Moon than the other: The Earth’s near side is 2158 km from the Moon’s center, and the far side is nearly 15,000 km away. That’s a huge difference, and the tides felt by the Earth would be amplified enormously — nearly 100,000 times what we experience now! There would be global floods as a tidal wave kilometers high sweeps around the world every 90 minutes (due to the Moon’s closer, faster orbit), scouring clean everything in its path.

That, and the fact that the earth would be so pulled and stretched that the crust would start to fall apart and the sea would probably boil away as the magma beneath the earth’s surface was exposed.

Oh, and the high likelihood that the moon would be pulled apart by the earth’s gravitational forces.

Look, it’s not going to end well.

In fact, the reason we are still here – and that the moon is still there – is exactly that: that we are here and it is there. Anything else would result in certain disaster. So there’s something to brighten your journey home today.

More facts and information here.