X-ray Stars of Orion (APOD 06 Oct 2007)

[tvkrys]

A stupid question perhaps - but the center star of "the Belt" has a blue dot in the center of the corona. None of the other stars has that. Is it because the star is so much brighter that it's burned in, or because there is a fortuitous eclipse happening, or am I missing the point?

TIA, Krys

[Case]

My guess would be that it is a mask to block out radiation from that location to prevent overexposure.

Funny how some stars that are present in visible light are gone in [url=hhttp://chandra.harvard.edu/photo/2007/orion/orion_xray.jpg]x-ray[/url], and vise versa. And that the four main Trapezium stars that seem so equal in visible light are so different in x-ray.

[Chris Peterson]

A stupid question perhaps - but the center star of "the Belt" has a blue dot in the center of the corona. None of the other stars has that. Is it because the star is so much brighter that it's burned in, or because there is a fortuitous eclipse happening, or am I missing the point?

It is an imaging artifact. It may be the result of saturation, or of the way the different energy values were mapped to colors. Resolving an eclipse or transit would be impossible, as all the stars are point sources. They only appear larger because of diffraction. For the same reason, you are not resolving the star, and are therefore not seeing the corona, or any other part of the star's structure.

BTW, these are the Trapezium stars at the heart of the Orion Nebula. The belt stars are far outside this field.