Saturday, March 20, 2010

A Very Red Star

Sorry for all the astronomy posts lately. I know some of you would rather see remodeling pictures, or photos of our feathered friends than yet another astronomy post, but consider yourselves lucky - we've finally gotten some clear skies, and I attacked a number of projects last Wednesday!

This is sort of a follow-up to a post from 3 January when I talked a little about detecting R Leporis, a very red carbon star from town while imaging the ISS. For those amateur astronomers among you, put it on your observing list before Orion/Lepus sets for the season. It is just a few degrees below Rigel, and while a long period variable (as most carbon stars usually are), it is still easily visible in binoculars at about 6.5-7.0 magnitude. Shown here is a wide shot showing a recognisable chunk of Orion, then a closeup with a 70mm, then finally a short (couple seconds) exposure with a 5" telescope (1250mm focal length). Yes, I know the last exposure is out of focus, but while out of focus, it saturates less easily and the dramatic red color is more obvious. As it is, it is only a 10 second exposure and the ones in focus only show it as yellowish (all shots with Canon XSi).

The color is supposed to get more vivid as it gets fainter, so I'll try to get it as it comes around the sun in the fall when much fainter. The red color is due to both the low temperature of the star which makes it redder (as opposed to a much hotter, blue star like Rigel), and also because carbon molecules in it's atmosphere block the bluer part of it's spectrum, making it redder still.

While strictly not a variable star observer, I do pay attention when objects you look at directly show strong colors. Most objects viewed through a telescope are not bright enough to trigger the eye's color sensors, so galaxies and nebulae appear in shades of grey.

1 comment:

David A. Harvey said...

Very cool - pardon the pun.