For Your Astronomers: ESA Star Mapper

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Link: ESA Star Mapper

 

...The ESA Star Mapper visualisation shows 59 921 stars from the Hipparcos Catalogue. This subset of the entire catalogue was selected as follows:

 

• we include stars with the best parallaxes – the criterion is parallax/parallax error > 5. Parallaxes give a measure of the distance to these stars;
  
• we do not include stars that have no catalogue record of the magnitude or colour information;
  
• we include all stars from the constellations, even if their parallax values do not satisfy the criterion above. For those stars we assign an artificial parallax value of 1 mas. In practice, this is needed only for one of the stars in Orion's belt (Alnilam);
  
• for the 27 435 stars for which there is no radial velocity measurement from the XHIP catalogue, a random value between -30 and 30 kilometres per second.
  

FEATURES OF THIS VISUALISATION

 

Click on Start to begin your exploration. The tour is divided into five sections: Apparent Magnitude, Absolute Magnitude, Hertzsprung-Russell, Motion, and Explore.

Each section displays a short explanation of the current view; click on the cross to hide the explanation, or on the horizontal lines to open the explanation panel.

To move around the sky use scroll to zoom and drag to rotate the view.

In the Apparent Magnitude section you can drag the slider to set the limit on what stars are displayed.

In the Absolute Magnitude section toggle between the Apparent Magnitude and Absolute Magnitude buttons to how the brightness of the stars differs with distance.

The Hertzsprung-Russell diagram can be shown with stars plotted in white or colour.

The Motion section lets you see how stars move through space. To help orient yourself you can toggle Star names, the outline of the Constellations, or a Graticule of grid lines.

The Explore section lets you apply the different filters together and to change the projection...