Seeing Double ~ Crux
Welcome to the first instalment of my new project,
Seeing Double. My aim here is to show people who are new to astronomy some of the great double/multiple stars we have in the sky and to give people something to look at while the moon is out drowning all the DSOs in its glorious (debatable) light.
We'll be looking at visual doubles, multiples and binaries of course so no special equipment (which is probably beyond us all anyhow) has to be used, just your telescope. I am hoping to do this on a monthly or bi-monthly basis depending on when I can get out doing constellation each month including 5-10 doubles drawing information from my own knowledge, various websites and a program called
cartes du ciel.
Definition: I could have put this in my own words, but alas I am to lazy... so here is an excerpt from the Eagle Creek Observatory site in their doubles section...
Quote:
|
A "double star", or multiple star, is exactly that. It's a set of two or more stars that appear next to each other. There are two types of double or multiple stars. There are "true" binaries or multiples and "optical" binaries or multiples. True binaries or multiples are stars that are actually physically close and are bound together by gravity. Optical binaries or multiples are stars that are lined up just right so that the appear to be physically close.
|
Anyhow, enough dribble lets do some observing!
This months constellation is our very own Southern Cross (aka crux). Nestled between Centaurus and Musca (the fly) it is our great southern lands best known constellation and it holds a number of really nice double stars.
**note, colours mentioned are how they appeared to me and not necessarily their true colour**
- 1-Alpha Crux: well... if the cross was up the right way it would be the bottom star. This star is actually a multiple consisting of 3 parts, 2 bright stars close together and one dimmer star out from the rest. All 3 stars show as blue in my 8" newt. Stars A and B are mag1.25 and 1.55 and are 3.9” apart star C is mag 4.8
- 2-HJ 4524: a great little double near the edge of NGC 4439 (open cluster) consisting of a white star (A) and a yellow star (B). Star A is mag 8.05 and star B is 9.93 and separation is 30.3”. quite pretty next the the cluster really…
- 3-HJ 4547: marked on the map for your convenience a double of white and what looked like blue in my 8” scope. The 2 near stars could be mistaken for part of the double and look nice next to it. A is mag 4.72 and B is considerable dimmer at 10.24 but the split is easy due to the 28.1” separation.
- 4-Dun 117: It’s a triplet! Yup 3 stars in one. This group contains t whites and one dimmer blue. A and B are 7.40 and 7.83 respectively, C is 10.24 mag. Seperation of A and B is 27.7” its another easy split… I didn’t do any hard ones
- 5-BSO 8: put your hand up if you love yellow stars! We have to lovely yellow stars of similar magnitude here right next to NGC 4337. Their magnitudes are 7.84 and 7.98 with a separation of 5.2”… A lovely sight by any standards.
- 6-Gama Crux: did you know that 3 of the 4 points are doubles/multiples? Well Gama Crux is one of them. Three stars in this one and they are very purdy. A is white and 1.8 mag, B is blue and 6.45 mag, the bonus star C is 9.25 mag. This is practically for binos (except C is bit dim).
- 7- Beta Crux: another triple system and one I did not conquer, so I thought I’d put this in as an added bonus because of the blood red carbon star near by. A is 1.25 mag and B is 11.4 mag. Although the aren’t close (42.3”) the dimness of B makes it very hard to see… but hey, check out the carbon star anyway
Now get out there and search for them
Please feel free to reply here with any feedback, pics or reports of these objects… I want to know how you go
also tell if you want more of these and any changes to the format you could suggest.
and heres a map to help yas.
http://img.photobucket.com/albums/v4...h_map-crux.jpg