The Heading Abbreviations

You will note that the constellation tables are incomplete! The first few constellation tables have the column HIP filled, others down the alphabetical list do not. The last updated constellation is Auriga (as well as Cygnus).

If the HIP column is not filled in, then the data is pre-Hipparcos.

You can find the HIP value from the HD catalogue number by using the conversion list provided on this web site: HD-HIP.

If the HD number is missing from this list, a number of online conversion tables is available; visit google.com and use the search words "hipparcos catalogue".

StarHDHIPVis. Mag.light yearsparallaxLuminosityOrbit?

1: Star

This is pretty obvious: the star's name, or ‘label’. That is, the Greek letter that Johann Bayer assigned to this star.
    Bayer introduced the idea of Greek letters in his 1603 star atlas, Uranometria, an idea that has proved very useful.

If your Greek is a bit shakey, you may wish to check out the Greek alphabet.

The present tables only treat selected Bayer ("numbered") stars.

2: HD

There are several catalogues devoted to listing hundreds of thousands of stars. One of the most often quoted is the Henry Draper Catalogue which was the result of efforts by Edward Pickering's team at the Harvard College Observatory begun in the late 1890s, named in honour of the astronomer Henry Draper.

By 1936 over 300,000 stars were listed in the catalogue. The "HD" reference has therefore remained a common designation for nearly all catalogued stars .

3: HIP

In August of 1989 a consortium of European countries launched an astrometric satellite named Hipparcos. Its task was to plot the position, parallax, and proper motion of about a hundred thousand stars with an accuracy hitherto unknown. (A similar task, dubbed Tycho, gathered less accurate information on about a million stars.)

The data has now been published and is in general use; this Hipparcos data should eventually become the standard reference for most observable stars.

In the links which follow, use the "Find" function then type in the star you wish (e.g. alpha And). Note however that if the star is a double (such as gamma Andromedae) you must have the exact label for "Find" to work. If you come up blank the first time, try putting in either a "1" or the component "A". For instance, "gamma And" yields no results but "gamma 1 And" does. (Make sure you put a space between the label and the number and the constellation abbreviation.)

Because of the size of this guide, it is divided into three files.

For a quick reference to HD and HIP numbers.

4: Vis. Mag. (Visual Magnitude)

The visual magnitude of the star is the star's brightness as it appears to observers on earth. Originally judged with the naked eye, the visual magnitude is now measured with photometric devises.

5: Light years

The distance of a star, calculated by the distance light travels in a given year. A particle of light (photon) covers 299,792,458 metres in one second (which for all practical purposes is usually given as 300,000 km). In one year, this photon covers 9.46x1012 kilometres.

6: Parallax

The distance of a star is first determined by measuring its parallax.

The parallax of a star is its angular displacement when measured from two different positions. Therefore, typically, a star's parallax will be measured six months apart. Even so, ground-based measurements of stellar parallaxes results in distances with rather large errors, hence these are generally reported to no more than three decimal places.

Hipparcos has measured star parallaxes with considerably more accuracy. It is now possible to improve the former standard of three decimal places to twice as many. The Constellations Web Page tables present the parallaxes to four places.

7: Luminosity

A star's luminosity is its "absolute brightness", that is, the total energy radiating from it, as compared with the sun's (which is given as equal to one). The larger the absolute magnitude of a star, the greater its luminosity.

8: Orbit?

If the star is a visual binary, and its orbit has been drawn, you can click on this link to view it.


Last updated 8 September 2003

Richard Dibon-Smith
Toronto