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New site updates

I've made a few significant changes to the Distant Worlds Star Mapper. There are two new features available:

  1. Tooltips for star information
  2. Viewing star charts at different times (the far past and future)

Here's a sample star chart showing both features: this is what the sky from Barnard's Star will look like in 12,000 years. A certain well-known star is identified in the center of the view:

The Sun from Barnard's Star in 14,000 AD

I've created some more examples, and a description of the new features, below the break.

Star Information Tooltips

The main Distant World star chart now has "tooltip" text that appears when you move your cursor over a star. The text includes the key information for the star: its name, its distance from the chart center, and its apparent brightness (magnitude):

Screen shot of Scorpius, with "tooltip" text

Looking back towards the Sun from Achernar, with "tooltip" text for the brightest star on screen

If two or more stars are very close together, only one tooltip may appear. In this case, adjust the chart scale slightly if needed to separate the stars.

Since the tooltip information is the same as the information previously shown as "detailed labels", that labeling option is no longer available. By default, only the star names are labeled; to see more details, use the tooltips.

Past and Future Charts

The Distant World Star Mapper now supports three-dimensional velocity calculations, so you can see what the sky looks like at different times. Here are some samples involving the nearby, rapidly-moving star 61 Cygni:

61 Cygni as seen now

61 Cygni as seen 4,000 years from now (~6,000 A.D.)

The quality of the charts is limited to the quality of the input data. Almost all the stars in the Distant Worlds Star Mapper have extremely accurate measurements of 2 of the 3 velocity components, specifically the 2 components of proper motion (the motion "across" the sky). By contrast, data for radial velocity (the component towards or away from the Earth) is more limited. In particular, stars with only a Hipparcos number (a "HIP" number in the star name) normally lack radial velocity information, so only a 2D velocity is known. For these stars, Distant Worlds Star Mapper treats the radial velocity as zero.

Over fairly short time frames, up to about 10,000 years, the proper motion has a more significant effect for most stars, so ignoring radial velocities isn't a significant problem.

At longer time frames, such as 100,000 years, you may want to reduce the chart magnitude cutoff so only fairly bright stars appear. This will help ensure that most of the stars shown will be ones with a reasonably accurate radial velocity.

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