Observing Binary Star Periods

[PeteF]

I'm sorry if this question is stupid, however I'm new to astronomy and couldn't find an answer through the usual searches.

I've noted that many of the stars I've seen with the naked eye are often binary stars orbiting each other and with the telescope I can differentiate the different stars. I wondered if there are some with orbital periods fast enough to be able to detect angular changes between the two stars over a period of time (ie weeks/months)? I've tried to work that out for myself using planetarium software, but can't determine if the changes are from the stars normal annual movement and therefore change in perspective, or even if the apps model that relationship properly in the first place.

[Saturnine (Jeff)]

Welcome Peter

Most double stars have orbital periods of 100s' to 1000s' of years so detecting any separation and angular change in a lifetime let alone weeks or months is doubtful at best. However there are a few notable exceptions such as Alpha Centauri, Sirius, Porrima ( Gamma Virginis ) and more, that have orbital periods of around 80 years and change can be noted over a few years.
Any doubles out there with faster periods would probably be too close together to be able to separate with amateur telescopes.

[Merlin66 (Ken)]

Amateurs can record the movements of close binary stars using spectroscopy.
The spectral lines of each star show the movement as they rotate around each other.

[PeteF]

Thank you for your replies.

Yes my understanding was the binary stars close enough to have small periods (by our lifetime standards) are too close together to optically resolve by conventional observation, however there were pairs (ie those mentioned) that were close enough to us that I thought it should be possible with appropriate time and patience.

Sadly I seem to have insufficient of either of the above Which brings me to spectroscopy and is something I would like to pursue further down the road. I hadn't considered it for this purpose, but it did come up when I was researching an answer to my question. Astro-spectroscopy is a field I've been fascinated by since learning about it. It strikes me as serious science on a pauper's budget and I'm definitely looking forward to pursuing that when the opportunity presents itself.

[Merlin66 (Ken)]

Pete,
You can start "Spectroscopy 101" with nothing more than a transmission grating and camera. This allows you to understand the requirements of a "good" spectral image and how to process them.
http://www.astronomicalspectroscopy.com/How_to.html

Ken

[PeteF]

Thanks Ken, yes that's exactly what I was going to do. It will come

Thanks for the link, I'll enjoy reading through that properly. I've already read quite a few sources on the subject as it's right up my alley. Believe it or not however, as things stand even "just" a camera and a computer at the telescope is a logistical PIA the way things stand. Even though it's out in my own backyard!

That will all get sorted but my buckets are all rather full at the moment, so once I get back on top of work a little it's something I'll pursue. I'm still taking baby steps in astronomy in general, but it's coming along and a wonderful journey to be enjoyed; no need to rush. With specialist astro cameras now quite inexpensive that will probably be the next step, a few happy snaps of a pleasant evening. Eventually I planned to get a grating a play around with spectroscopy as it's just, well plain cool!

[Saturnine (Jeff)]

Don't know if you have seen this ( Wiki is your friend ) but it does a good job of explaining the movements of Alpha Centauri A & B and shows how the PA and Separation change over time. When I first saw them through a telescope in the mid 60s' they were quite wide apart, about 12.0" I think and now they have closed to about 4.0". Just a game of patience and long memory but the spectroscopy angle for short period binaries looks interesting.




https://en.wikipedia.org/wiki/Alpha_Centauri

[PeteF]

Thanks Jeff, no I hadn't seen that entry, I'll have a good read of it when I get some time off work. I had a skim through and the apparent v true orbits was an interesting thought. Obvious in hindsight, like most good statements are.

[Terry B]

Originally Posted by Saturnine

Don't know if you have seen this ( Wiki is your friend ) but it does a good job of explaining the movements of Alpha Centauri A & B and shows how the PA and Separation change over time. When I first saw them through a telescope in the mid 60s' they were quite wide apart, about 12.0" I think and now they have closed to about 4.0". Just a game of patience and long memory but the spectroscopy angle for short period binaries looks interesting.




https://en.wikipedia.org/wiki/Alpha_Centauri

I have measured lots of binary stars using spectroscopy. It is quite interesting.
An example is del1 Tel that I have attached. The zip file is an animated gif showing the change in the Hydrogen alpha line with time. It is slightly too big to upload as a gif to this forum. Each frame is 1 day apart. The period is 18.8 days so easy to observe from night to night. Some are much faster with periods of a few days.
All were taken with a commercial LHIRES spectrograph.
Terry

[Merlin66 (Ken)]

If you can image the double stars, then Florent Losse's Reduc program is the one to use.

Email him for a copy. florent_losse@yahoo.fr

http://astrosurf.com/hfosaf/