Welcome to the Double Star Section of the AAQ, dedicated to the enjoyment of observing double and multiple stars.
Read on for an introduction to Double Stars. You can then jump to further information on Double Stars for a list of books, journals and web references.
When you are ready to practice what you’ve read and see some beautiful and challenging sights, we’d invite you to take part in the AAQ Resolution Survey. By simply using a telescope, your eyes and some easy to learn techniques you can discover more about your equipment and the sky, and contribute to some useful astronomical research.
What is a double star ?
As the name suggests, it is a pair of stars close together in the sky, in fact so close together that they can only be separated using some kind of optical aid. Some wide, bright doubles can be seen in binoculars, but most need a telescope of some kind. It used to be thought that they were chance alignments of stars in the sky, but it is now known that such alignments are rare and most doubles are actually close to each other in space and bound by gravity, either orbiting each other (when they tend to be referred to as binary stars), or having common proper motion – that is, they are moving through space together. In fact more than half the stars we see in the sky are actually multiple star systems. In that sense, our own sun is in the minority because (as far as we know) it has no companion.
Alpha Centauri is one of the most famous doubles, and only accessible to us blessed southern hemisphere observers. Alp Cen is actually a triple system, with the third member, Proxima Centauri (quite far away from the bright pair and not visible in the same field), being the closest star to our sun. The bright pair are orbiting each other relatively quickly, completing a full orbit in only 79.2 years. So motion along the orbit is measurable in much less than an observer’s lifetime, which is not always true of visual doubles.
Why observe double stars ?
Why observe these fascinating objects ? Well, there are plenty of reasons. The Budget Astronomer lists them as follows:
- They are good targets for an urban or suburban location. Many of them are quite bright, and there are binaries visible all year long, whereas planets and the moon are not always up when you want to observe.
- They are aesthetically pleasing. A nice binary pair with distinct colour differences can be very pretty.
- They provide a challenge – some are faint, or very close, or have a high magnitude difference, and they provide a certain satisfaction.
- Binaries give you an excuse to push the magnification on your scope to “crazy high” powers – above 600x.
- You will never run out. There are thousands of binaries visible from any given latitude.
- Binaries provide amateurs an opportunity to contribute to “real science” – there are more binaries than professional astronomers. Backyard observers can contribute by measuring the separation and position angle, which can then contribute to calculating orbits, which in turn helps us learn more about the mass of the stars, and helps to refine the model of the nature of how stars form and evolve.
The AAQ monthly newsletter includes many interesting doubles to observe month by month, in the Visual Observing section. There are websites which include several lists of doubles worth a look. There are books which deal with double stars or include aspects of doubles and their observation.
Further reading
The 2014 Berenice and Arthur Page Medal – Tim Napier-Munn
In 2014, Tim Napier-Munn was awarded the Page Medal for work on binary stars systems and for demonstrating a deep understanding of observational techniques and processes that will progress the field.
Most recent papers by members
Real science for the time poor amateur – The study of Double Stars from the Southern Hemisphere
Graeme Jenkinson gave this presentation at the Astrocon 2017, the annual national conference of USA amateur astronomical groups/organisations. For 2017 it was held over three days just prior to the August total solar eclipse at Casper, Wyoming USA, which was on the path of eclipse totality.
Blue Star Observatory measurement of twenty neglected southern multiple stars
Graeme Jenkinson, Peter Culshaw, Diane Hughes, John Hughes and Des Janke have published a paper on neglected southern multiple systems in the Webb Society Double Star Section Circulars.
Astronomical Association of Queensland 2016 programme – Measurements of nine neglected southern multiple stars
Graeme Jenkinson has published a paper on nine neglected southern multiple systems in the Webb Society Double Star Section Circulars.
Astronomical Association of Queensland Measurement of Seven Neglected Southern Multiple Stars
This paper presents the results of a mid 2015 program of photographic measurements of seven southern multiple stars.
Measurement of neglected southern multiple stars – two listed pairs and a possible new pair
Through mid-2015 measurements were completed of the following two southern multiple stars as listed in the Washington Double Star Catalogue. A pair that appear to be previously unlisted in the WDSC was found just to the west of B2450 and B2451.
Measurement of multiple star system in Norma
This paper details the results of photographic measurement of the triple star system RST5413A-B / HJ4857A-C in Norma over two years – 2014 and 2015.
Measurement of 17 southern multiple systems
This paper presents the results of a 2013/early 2014 programme of photographic measurements of seventeen southern multiple stars. The images were obtained using a Meade DSI CCD camera in conjunction with an equatorially mounted 150-mm f/8 refractor and software programme AstroPlanner 2.1 (Rodman).
Measurement of nine neglected southern multiple stars including two possible anomalies
Through the second half of 2014 measurements were completed of the following southern multiple stars as listed in the Washington Double Star Catalogue. Using a 400mm f4.5 Newtonian reflector fitted with a Meade DSI 2 camera and software program Astroplanner V2.1 (Rodman) the obtained images were analysed using Losse’s Reduc software.
Measurement of Two Long Neglected Southern Multiple Stars
This paper presents the results of a 2014 program of photographic measurements of two multiple star systems (one a double, one a triple) not studied since their initial measurement in 1900.
Analysis of Errors in the Measurement of Double Stars Using Imaging and the Reduc Software
This paper reports quantification and explanation of some sources of error in using the Reduc software to measure the PA and separation of double star images.
Measurement of 24 southern multiple stars
Measurements have been made of 24 southern multiple stars from the Washington Double Star Catalogue. Images were acquired using a Meade DSI CCD camera coupled to a 150mm f8 refractor, and analysed using Losses Reduc software.
Measurement of some neglected southern multiple stars in Dorado and Pictor
Measurements have been made of eight neglected southern multiple stars from the Washington Double Star Catalogue. Images were acquired using a Meade DSI CCD camera coupled to a 150mm f/8 refractor, and analysed using Losse’s Reduc software.
Measurement of some neglected southern multiple stars in Pavo
Measurements of six neglected southern multiple stars have been made using a Meade DSI CCD camera coupled to a 150mm f8 refractor.