Friday, March 02, 2007

Hiding in plain sight": A new star in the Southern Cross

Sub-title: What X-ray astronomy can do for you.

One of the most familar constellations to observers in the Southern Hemisphere is the Southern Cross (Crux Australis), which surprisingly for a constellation, actually looks like its name (the image is a cut out of an image at APOD, looking from Mauna Kea looking towards Mauna Loa).

Astronomers using the Chandra X-ray Observatory have discovered that one of the stars in the Crux Australis, specifically Beta Crucis (left hand middle, in the image shown) has a previously-unknown companion (NYT article here). Although many stars have faint companions, this newly-discovered star should actually be moderately bright in the visible part of the spectrum (11th magnitude).

How could you miss such a bright star? Easily, as Beta Crucis is much brighter than it. Beta Crucis is a massive star (about 16 times the mass of the Sun), while the newly discovered star appears (from my reading of the NYT article) to be about Solar mass.
Crudely stellar luminosity is proportional to the cube of the mass, so Beta Crucis should be about 4000 times brighter than the new star.

Other interesting things to be found in the Crux Australis: The coalsack and (famous) horsehead nebulae - you can even see the darkness of the coalsack in the APOD image above.

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