The Jewell Box

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Obj Type
Date Taken:
NGC 4755
Star cluster
CTIO, Chile

This test image represents the first SSRO collaborative effort with SKYNET using one of their PROMPT 16"  f/12 RCOS telescopes located at CTIO (Cerro Tololo Inter-American Observatory) in Chile.

This cluster was one of the finest open clusters discovered by Abbe Lacaille when he was in South Africa during 1751-1752.

The "Jewell Box" cluster is one of the youngest known, with an estimated age of only 7.1 million years.  Its hottest star is of spectral type B0. According to Burnham, the 3 brightest stars are blue giants of mag 5.75 and spectral type B9, mag 5.94 and type B3, and mag 6.80/B2, while the fourth brightest star is a mag 7.58 M2 red supergiant. Another mag 5.7/spectral type A1 star is probably also a member, another white supergiant:  This star would be the brightest of the cluster at about absolute magnitude -7.7 (83,000 solar luminosities).

Situated close to the cluster is a huge dark area of the sky, right within the band of the Milky Way called the "Coal Sack".  This is a huge dark nebula, probably the nearest at 500 to 600 light years distance, and 60 to 70 light years diameter

Processed by Rick Gilbert and Jack Harvey

Technical Details
Exposure Time:
RGB (25 x 10 seconds for each color)
Apogee Alta U47
RCOS Carbon Truss 16 inch f/11.3 Ritchey-Chretien
Software Bisque Paramount ME
© 2024 Harvey
Used with permission, No reproduction of these images are permitted without written approval from Harvey.