02/09/2026
Friday February 6, 2026
I've mentioned Rigel several times on the outings; that it is about 70 times bigger than our star, bright, but Far more powerful in ultra violet (which we can't see) and far enough away ( about 900 light years away) that the light we see left Rigel about the time Vikings arrived in North America. But what I have often wanted to show people is a star in about the same area, a little west of Orion.
I set up a 90mm refractor thinking we'd concentrate on Saturn and Jupiter. The sky was clear, but that doesn't really guarantee good seeing for certain things, like planets or the moon, which a smaller 90mm refractor might be good for. It wasn't, and Saturn is far enough west, getting low enough, that although you could see the rings were brighter, have opened up just a little more than we last saw, higher power (160x) didn't really help. Jupiter was better, but still 'soft'. So, on to other things.
We saw M42, the Orion Nebula, and the clear skies were good for that. Then we went on to observe and discuss some stars and their spectra, and then some doubles. Sirius was twinkling, but bright, and at low power, with a diffraction grating, it's spectra showed up on both sides. We got to discussing what the spectra can tell and what we have found.
It is easy to think of the sky as some sort of dome and imagine everything is just plain 'Far', kind of 'all the same kind of Far'! But it certainly isn't. We can't see the distance with our eyes, and there are all sorts of examples where far stars are bright and near stars, well, you need a scope to see them. They are 'Close' but Faint !
The star I have often wanted to show is called 40 Eridani or Omicron 2 Eridani. At 16 light years away, fairly 'close', it is hard to see from uptown. The main star is a little smaller, a little fainter than our sun. It is a K spectral class star And it is a great help in finding 2 other kinds of stars, stars that are usually hard to find because they are so small and faint. These stars are good examples of how stars burn and age. A pair of stars, a red dwarf and a white dwarf, form a double star that orbit the K star, so it is a triple star system. The red dwarf is much smaller than our sun and a lot of its energy goes out as heat, infrared energy. Far smaller, about the size of our Earth, the white dwarf is the remains of an old star, the left over core that no longer has hydrogen to fuse and gravity takes over, crushing what is left of the star to very high temperatures and pressures, leaving it nothing to do but Slowly cool off.
We could see the main star and the close double that orbits it, but the 90mm was small enough it had trouble, in turbulent air, separating that 'double' into its two stars. This is a 'close' star, so, it also indicates that if you were on a planet around 40 Eridani, looking back at our sun, our sun would not be the brilliant thing we see here! Yes, it would be visible to the eye, but not 'bright'. This is why our star is called a 'dwarf'. It is not 'big' as stars go, and huge, Bright stars are really rare in comparison.
Also, a white dwarf is not the 'last' possibility. It was the invention of the spectroscope that opened up all sorts of possibilities, realities, and what we can imagine, well, we are still struggling to understand. Beyond a 'white dwarf', there are neutron stars and black holes, with variations we are still learning about. Try to imagine a neutron star, where they think densities are so great, atoms don't just get crushed, but the nuclei, too, are crushed, so you don't just have a 'solid', but some strange DENSE fluid, some sort of 'soup' of quark particles.
Maybe, in comparison, you might wonder if walking along on a sidewalk, the cement, or the steel supporting our skyscrapers, are built of 'light and fluffy' stuff.
