Sunday October 25 2020




Village Sky At Night with Brian Watkiss

Size matters in solar system and beyond

Posted on January 31 2016 at 10:23:41 0 comments


Amateur astronomer Brian Watkiss peers into the Village night sky.

I’ve recently viewed an interesting video on the interweb thingy, which compared the relative sizes of the planets in our solar system and our Sun with the brighter stars that can be seen in the night sky.

It dawned on me that a lot of these stars are visible at this time of year, so let’s have a look.

The video starts with the Moon, which is new on the 10th, so look for a really thin crescent on the 11th or 12th as soon as the sky starts to darken. Full Moon is on the 24th.

Then come the three smaller planets and Earth. I’m sure you’ll know them and their relative sizes.

The planets continue till we reach the largest, Jupiter. This is visible from about eight thirty, really low in the east.

Our Sun comes next, showing a leap in size from even Jupiter. You should never look at the Sun, of course, so I’ve included a picture of it, in case you‘ve forgotten what it looks like (right).


One of the most beautiful stars comes next, Sirius, although it’s not that much bigger than the Sun, being about twice the size.

It is easily seen because it’s the brightest star in the sky and has a distinct bluish hue. Look for it low in the south, below Orion.

Look up above Orion and left to find a pair of stars, Castor below and Pollux above. The latter is next, being an orange giant about eight times larger than our Sun.

Now we move on to the first of the red giants with Arcturus, which has a diameter roughly thirty times that of the Sun. Unfortunately, it doesn’t rise till about eleven, again in the east, close to where Jupiter was earlier.

Aldebaran is next, on the opposite side of Orion to Pollux, in the Horns of Taurus the Bull. This is actually a system of four stars but the main one is an orange giant nearly fifty times as big as our Sun.

Down at the bottom of Orion, on the right hand side, is Rigel, next in the video. This is also a system of stars but the large one is a blue supergiant roughly sixty times the diameter of the Sun.

After a star no-one has heard of, comes Antares at nearly eight hundred solar diameters. This one is only visible in the mornings at the moment, low in the east, near Saturn, halfway between Venus and Mars.

Slightly smaller is Betelgeuse but at least we can see that at the top left of Orion, looking distinctly like the red supergiant that it is at over six hundred times the size of the Sun.

The whole sequence ends with a couple of stars that are over a thousand times the size of our little star, but there is some dispute over their sizes anyway because they are so far away.

This also means that they can’t be seen without specialised optical equipment – and we don’t want to get into astronomy, do we?

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