Attractive Double Star STF 174

[lunator]

This is the 1st in my (very) occasional posts on Double stars that are pleasant to observe. But may not be very well known

STF 174 is in Aries just north (about 1 degree) of Beta Aries. It is also known as 1 Aries.

The primary is yellow (it is a GIII giant) and the secondary is blue.

In my scope at x96 the stars are fairly easily split although a magnification of x200 really bring out the colour contrast.

If your're in the area looking at Mars stop by and visit this Double.

Cheers

Ian

[FLO]

Thanks for that Ian; I'll search it out at the SP

[FLO]

(it is a GIII giant)

... Whats a GIII giant?

Steve

[lunator]

Steve

The star is of the spectra class G (Similar to the Sun) The standard spectral classes are OBAFGKM  decreasing in  temperature.

O class stars are 10,000 degrees C+ whilst the M class are around 3500.

The colour range Goes from Blue through white to yellow, orange and finally red.

The Sun is a about 5750 and is a nice pleasant yellow.

Stars are also grouped into 5 classes I (super giant), II (Bright Giant), III (Giant), IV (Sub-Giant), V (Main sequence Dwarf)

The Sun is a type V . That is a hydrogen fusing star on the main sequence (also known as main sequence dwarf ).

When it runs out of hydrogen and starts to fuse helium it will expand and become a type IV sub giant. This is also known as the red giant phase and the Sun will have left the main sequence.

The Hertsprung-Russell diagram which shows absolute luminosity plotted against spectral type on a graph really shows this relationship clearly.

STF 174 would nave been a larger star then the Sun and probably similar to Sirius (although this cannot be known for certain), it has finished fusing Hydrogen and is fusing helium and possibly heavier elements like carbon. It is now classed as a giant.

I would be happy to provide  a more detailed primer if anyone is interested.

I'm a bit of an 'egg-head' when it comes to this sort of thing.

Cheers

Ian

[FLO]

Thanks Ian for the quick response and explanation. 

I have learn't something today

Steve

[daz]

I would be happy to provide a more detailed primer if anyone is interested.

Ian

I think this would be a great idea

[The Warthog]

The standard spectral classes are OBAFGKM  decreasing in  temperature.

This can be committed to memory by the phrase, "Oh be a fine girl, kiss me!" They used to add "now, sweetheart!" but I haven't heard much of the N and S class stars, and I think they may have been dropped. You can remember the order of temperature by thinking that this sentence should be pronounced with rising heat, but it isn't. He kinda loses interest by the end. The unisex/PC version of this is, presumably, "Oh be a fine geek, kiss me!"

[Astroman]

WH: The S, N and C types weren't dropped, they were actually added after the chauvinistic saying was coined. They are rarely seen, since they're intrinsically faint and are mostly fusing helium to carbon, making them deep red. I'll post a link to a list of red carbon stars on my website, if you like. They are also variables mostly, changing in brightness and redness through their cycles. I have kind of a "thing" for red and variable stars, too. Nothing unhealthy, mind you...