Circinus – the compass

October 1, 2017


Circinus is a constellation named for the drafting compass, which is the thingy you use to draw perfect circles like Charlie Brown’s head. At first glance you probably thought Circinus was about the circus, but sadly, no. Navigators also use this sort of compass to measure and make marks on maps during long boring days at sea.

French astronomer Nicolas Louis de Lacaille named the constellation and as astronomers have known for a long time, he was fascinated with weird stuff. If you are like most people, the one nice thing about your drafting compass is that you always know where it is. It’s in that drawer with all the other crap you never use.

I had to have one in fourth grade, to go in the little bag with lots of other awesome school supplies. The teacher had a great big one that held chalk, but mine was a cheapie, with a little lever that barely held the pencil and a super-sharp pointed part for scratching your initials in the desk. Then in eighth grade I took an actual drafting class and bought the five dollar model.

Then one day years later when I had a real job I got excited and bought one for $29.99 to go with my tilty drafting table. So now I’m totally ready if I ever need to draw a meme that involves Charlie Brown’s head.

Circinus X-1 is an object in Circinus that is cranking out some major x-ray action. It appears to be two stars actually, a neutron star and a regular star. Neutron stars are strange animals. They are dead stars that are rather heavy and have crushed themselves under their own weight. They are therefore made of neutrons which, unlike some particles I could mention, don’t mind touching each other.

Think of it this way, if a hydrogen atom were the size of a big football stadium, the proton would be a golf ball on the 50 yard line and the electron would be orbiting the stadium somewhere in the outer parts of the parking lot.

That’s a lot of empty space. Also, the electron would still be too small to see. But with a neutron star, all the empty space is filled. It’s like you filled the stadium with golf balls. If you did that to the atoms of Mount Everest the whole damn mountain would fit in a tablespoon. But it would still weigh the same so don’t even try to pick up the spoon, it will just bend. Anyway, some of the stuff from the regular star is streaming over to the neutron star. Do you want x-rays? Because that is how you get x-rays.

PSR B1509-58 is a pulsar in Circinus. A pulsar is really just a neutron star with an attention-seeking disorder. Atoms and the bits that compose atoms are near the surface and are being accelerated to high velocities. They get shot out into space from both the north and south poles. If either one of those poles happens to be aimed at Earth, we see a rapid pulse.

The pulse happens because these things are spinning fast and they wobble. This pulsar, PSR B1509-58, has a spin rate of 7 revolutions per second. Some of them spin even faster, extremely fast, as much as several hundred times per second. Pulsars are spinning so fast that they pooch themselves out at the equator. There is no way they can be perfect circles.

Carpe Noctem

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