Astronomy On-Line

Variable Stars

In the footsteps of John Goodricke

The sky is full of variable stars and many of them are regularly observed by professional and amateur astronomers. This project will give you the chance to contribute actively to such observations, by making your own brightness estimates of one or more selected objects!

This Astronomy On-Line Collaborative Project has been set up with the kind support of The American Association of Variable Star Observers (AAVSO, the prime organisation of its kind in the world. It unites many hundreds of variable star observers, not only in the United States, but all over the world, including Europe. It is quite likely that many of the amateur astronomers who participate in Astronomy On-Line are already connected with AAVSO.

There are also other specialized groups of variable star observers in many countries. You may obtain information about these by contacting the main astronomical clubs or the Astronomy On-Line National Steering Committee in your country.

Note in particular OAT-SISSA Variable Star Zoo. This site gives a complete set of instructions and some real stars to observe with naked eye or binoculars.

Within this project you will learn how to do such measurements with the unaided eye. You will also find interesting information about the first observations of a variable star, Delta Cephei, by a dedicated young English amateur astronomer in the late 18th century. Despite his serious handicap, he made this historical discovery that later led to the establishment of the first, reasonably correct distance scale in the Universe.

In order to participate in this Astronomy On-Line project, you should observe the same star, Delta Cephei, which is well situated in the evening sky in November. By using the method that is described in detail here, you will be able to judge its brightness (magnitude) with amazing precision (better than you ever thought!), especially if all members of your group do this individually and you then calculate the mean of your estimates. By combining measurements from many groups, it will be possible to draw the lightcurve (change of brightness with time) of this pulsating star.

How to submit your observations

Once you have made some observations, that is, you have measured the magnitude at a certain time, you may submit it to the AAVSO by means of a standard report form. It is available here in three different formats (GIF, 12k), (Postscript, 304k), (Zipped Postscript, 53k); pull over the format you prefer. This form is used by all variable star observers who report to AAVSO.

Please send your observations by email to Janet Mattei (AAVSO)

When you send your observations, be sure to indicate your Astronomy On-Line Group Designation! Only if you do so, will the AAVSO know that your observations belong to this Astronomy On-Line Collaborative Project!

When the observations by your group have been submitted to the AAVSO via this form, the AAVSO register them and will after some time put a light curve online showing all Astronomy On-Line observations that were submitted together in one diagram.

One or two months later, these observations may finally appear "in the big picture" where there are combined with observers from other sites.

Unexpected events

Unexpected events some happens in the sky which are related to variable stars, for instance Novae and, more rarely, Supernovae. If you want to be informed about the latest developments, you may like to consult the AAVSO Alert Notices, the IAU Central Bureau for Astronomical Telegrams (IAU CBAT) or Astronomical Headlines of the IAU CBAT.

If there would be an important event in the sky during the duration of the Astronomy On-Line Programme that is suitable for observation by the groups, a request will be made immediately! In that case, we hope that you and your group will not hesitate to participate!

This exercise has been prepared by Janet Mattei (AAVSO) to whom you should address all questions.

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