Space Shuttle and ISS Cross the Sun

French astronomer Thierry Legault has taken some amazing images of the Space Shuttle crossing the Sun whilst docked with the International Space Station.

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The ISS is travelling at 25000 kmh and took just 0.7 seconds to cross the Sun. He started taking four pictures a second, two seconds before it was due to cross the Sun. Distance to the ISS – 500km, distance to the Sun – 150000000km.

Some more pictures he took in May this year of the Space Shuttle crossing the Sun…

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The background texture in the images is not noise, it’s solar granulation. Each grain is a bubbling cell of solar gas that is approximately the size of Texas.

How is it possible that the Space Shuttle and the Sun are sharp simultaneously?
Beyond several kilometers, a telescope does not show a difference of focus, all objects seem to be at infinity whatever their distance: 600 km (Atlantis and Hubble), 150 millions km (the Sun) or a galaxy at billions light-years. In other words, the photographic notion of “depth of field” does not exist in astronomy.

Why do the ships seem so big compared to the Sun?
The Sun is 250000 times farther than Hubble and therefore appears 250000 times too small in comparison. If Hubble was placed at the distance of the Sun, it would occupy in the photographs about 1/50000 of a pixel and would be of course invisible. The Sun could contain one million of small, very small planets like the Earth…

Why don’t we see sunspots or prominences (flares) on the Sun?
The Sun goes through a period of calm and does not currently shows spots. The prominences are visible only with a special narrow-band filter (Hydrogen-alpha), the filters being used here are broad-band and cannot show them.

Is it the true color of the Sun?
The Sun emits a white-yellow light. But to observe and to photograph it, one must use very powerful solar filters that can transmit different colors; some filters give a bluish color, other a white color, others an orangey color. Most astronomers choose a yellow-orange tint for their images of the Sun; www.spaceweather.com shows the daily Sun under an orangey color.

Why is the edge of the Sun darker than its center?
This darkening at the edge is a physical effect due to the fact that the Sun is not a solid object but a sphere of gas whose surface transmits and diffuses the light emitted by its core.

How can Atlantis cast on shadow on the surface of the Sun?
It’s not a shadow but a silhouette.

Visit Thierry Legaults site for more amazing photographs

3 thoughts on “Space Shuttle and ISS Cross the Sun”

  1. Awesome indeed, some inspiration for the cover or the inner sleeve of the next Gas / High Skies releases ?
    The silhouettes are quite precise and sharp, to bas that the resolution is a little small to make a wallpaper instead of the saturn’s moon ;)

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