February 15 – The Cat’s Eye Nebula

NGC 6543

Everybody’s seen photographs of this one, but that’s no reason to not show it again: it’s the Cat’s Eye Nebula, otherwise known as NGC 6543, (or “Caldwell 6″ in Patrick Moore’s list of more challenging, non-Messier objects), an expanding cloud of mostly hydrogen and helium, discovered on February 15th 1786 by William Herschel.

Hubble image of the Cat's Eye Nebula (image credit: NASA/ESA)
Hubble image of the Cat’s Eye Nebula (image credit: NASA/ESA)

The nebula is one of the most complex we know of, and was formed around 1,000 years ago when the star (or stars – it may be a binary system) at its centre lost its outer shell. That star, smaller than the Sun but approximately 10,000 times as luminous, is what is responsible for the nebula being lit up like a Christmas tree.

NGC 6543 is around 3,000 light years away and has an observed density of about 5,000 particles per cubic cm.

Launched on February 15th 1973 from the Baikonur Cosmodrome, Prognoz 3‘s purpose was to study solar flares, and help increase our understanding of how the Sun’s activity affects the Earth’s magnetosphere. Prognoz launches took place at an impressive rate. Getting the entire fleet of 10 satellites off the ground only took 54 weeks.

Asteroid 442 Eichsfeldia was discovered on February 15th, 1899, by Max Wolf and Arnold Schwassman. It’s a C-type main belt asteroid of approximately 65 km diameter.


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