Pyxis – the compass box

Pyxis is a constellation in the southern sky that honors the mariner’s compass. Short of the Internet itself, few things have shrunk our world like a free-floating magnetized needle.

The constellation is basically just three stars in a line and over the centuries star maps have shown it as various things, usually something nautical because it’s near the stars of the good ship Argo. For example it has been called “the ship’s mast” by some, and by others “the rope thingy that sailors use to measure speed.” Nicolas Lacaille settled on the compass in the mid 1700’s and everyone sort of said “Oh yeah, a compass, good one Nick.”

In 1995 a globular cluster was discovered in Pyxis and it looks like the Milky Way might have ripped it away from the Large Magellanic Cloud, or perhaps it was tossed out by the LMC due to some gravitational transgression. Galaxies can be rather unforgiving like that.

NGC 2818 is a planetary nebula in Pyxis. It’s the thrown-off outer layers of an aging, dying star. Actually in this case the star appears to be quite dead, interred into the white dwarf mausoleum of the H-R diagram. But the nebulous remnants look pretty amazing providing you own a huge space-based telescope like the Hubble.

The plane of the Milky Way runs through Pyxis and there is a lot of dust blocking our view in that direction. It’s part of the so-called “zone of avoidance” which means it’s a bad place to look if you want to see far. Even if you can see through the dust at what’s behind, you have to account for whatever the dust is doing to the light when you analyse it. The nature of the light depends on the nature of the dust. The problem is, you also have to analyse the nature of the dust based on the nature of the light, so there is a bit of circular logic there. Still, we have more or less figured it out by sweeping up the lab floor and dumping the debris in front of a laser beam. The conclusion is that the Milky Way is rather messy and the lab could use a bit of a touch-up as well.

Carpe Noctem.