Splitting stars?

[allen g]

What does it mean to split stars, what is purpose, how is it done and what equipment is required? thanks allen g

[Hitesh]

Hiya, I'm no expert but I think that's when you split double stars; famous ones are the doubles epsilon lyrae, also mizar a and b.

Get yourself turn left at Orion, really good book shows you how to find and what these doubles look like.

[JamesF]

There are a number of what appear to be single stars that are actually two or more stars in apparent close proximity. Some are binary pairs (or bigger multiples) and therefore physically related, whereas other we just see as multiple stars because they happen to line up when we look at them when in fact they may be many light years apart.

Splitting a double is being able to resolve the apparent single star into its component stars in your telescope so you can see a clear gap between them.

James

[umadog]

Most doubles are physically related, actually. Optical doubles are rarer.

"Splitting doubles" is just another term for observing double stars. It merits it's own term simply because a double is only classed as "observed" if the components are resolved, or "split." You can do this with any telescope.

[Qualia]

What does it mean to split stars?

What appeared as a single star under low magnification is often a star which comes in pairs or trios under higher magnification. When you can see and recognise this difference, you have effectively, ‘split a star’.

What is the purpose?

There need not be any purpose in splitting a star, just as there need not be any necessary purpose in strolling through a forest at dawn or writing a poem, but we can highlight some of the more utilitarian reasons for undertaking such a pursuit:

• star systems are among the very few objects in the night sky to show you any real colour, in some cases majestically bright and vibrant. This gives the pursuit a rather pleasing aesthetic appeal.
  

• tracking down these doubles gives you excellent practice in the art of star hopping and in reading and using star maps and charts.
  

• seeing conditions will often influence your success, so by observing double stars on different nights you can gain familiarity with how stars appear in your telescope under varying conditions.
  

• like lunar and planetary observing you can observe double stars from your own garden or roof top under quite heavy LP, so you don’t need to hang around waiting to go to a dark site.
  

• searching for double stars teaches you something about your telescope’s resolving power, that is, its ability to provide you sharp and detailed viewing, even of objects that upon initial appearance come across as a single source of light.
  

• by comparing the double and multiple star systems you can practice your understanding and skills at recognizing differing star magnitudes.
  

How is it done and what equipment is required?

Generally, you will need a decent mount, tripod, telescope (I’d say a refractor is the nicest for this particular pursuit), varying quality eyepieces and some kind of star map to help you identify a double star system in the first place and later to help you track it down, assuming you don't have a spot on GoTo system.

Hope this post has helped in some manner of ways.

Qualia

[lukebl]

I don't 'do' doubles much, but I enjoy the occasional challenge of spiltting a difficult one as a test of my eyesight, optics and seeing conditions. Something to do when the sky isn't completely dark, or when transparency isn't too good. I've yet to split Sirius, or anything with a separation less than 1.2", but that's my challnge this winter.

[acey]

"What is the purpose"

In the 18th century it was assumed that most double stars were "optical doubles", i.e. chance alignments. In that case it might be possible to observe a parallax shift as Earth orbits the sun (the stars would appear to vary in separation as Earth moved across a large distance) and this could be used to find out how far away the stars were - something that nobody knew then. So William Herschel undertook an extensive survey of double stars, and found that in most cases their apparent motion showed them to be binary systems.

Many doubles have been admired aesthetically as colour contrast shows up well in closely separated stars. They are also a standard way of testing the resolving power (optical quality) of a telescope.

[allen g]

very informative and thank you for your wisdom. Now for something new to view in our universe! thanks allen g