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Object description
The open star cluster Collinder 228 in the large Carina Nebula

Short objekt description:

Collinder 228 is one of several very bright open star clusters in the Carinae Nebula NGC 3372, located about 25 arc minutes south of Eta Carinae. Its many luminous stars of spectral classes of type O ionise the surrounding nebular masses and energize them to glow. The brightest star in Collinder 228 is QZ Carinae (HD 93 206), it is a multiple star system and probably consists of four massive stars with the designations A1 and A2 as well as B1 and B2. Pairs A1/A2 and B1/B2 take no more than 25 years to orbit each other, while pair A orbits every 20.7 days and pair B every 6.0 days. The overall system is slightly variable, the brightness varies by roughly 0.5 magnitude classes.
QZ Carinae A1 is a blue supergiant of spectral type O 9.7 I with about 40 times the mass of the Sun. With a surface temperature of 32,000 Kelvin, it shines about 500,000 times as brightly as our Sun.

QZ Carinae B1 is a hot blue giant, it belongs to the spectral type O8 III and has about 14 times the solar mass and 30 times the radius of the Sun. With a surface temperature of 33,000 K, it shines about 200,000 times as brightly as the Sun. All four stars together have about 100 times the mass of the Sun.

The stars of Collinder 228 are probably not older than 1 million years, their distance to the solar system is about 8,500 light years. A complete overview of the Carinane Nebula in a mosaic view we show here.

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