The great variety of star colors in this open cluster [ http://www.seds.org…] underlies its name: The Jewel Box [ http://www.seds.org…]. One of the bright central stars is a red supergiant, in contrast to the many blue stars that surround it. The cluster [ http://adsabs.harva…bib_query?bibcode=19 63MNRAS.126...11F ], also known as Kappa Crucis [ http://adsabs.harva…bib_query?bibcode=19 84A%26AS...56..373D ] contains just over 100 stars, and is about 10 million years old. Open clusters [ http://antwrp.gsfc.…] are younger, contain few stars, and contain a much higher fraction of blue stars than do globular clusters [ http://antwrp.gsfc.…]. This Jewel Box [ http://www.iucaa.er…] lies about 7500 light-years [ http://imagine.gsfc…] away, so the light that we see today was emitted from the cluster before even the Great Pyramids [ http://www.pbs.org/…] in Egypt [ http://www.cia.gov/…] were built. The Jewel Box, pictured above [ http://www.mso.anu.…], spans about 20 light-years, and can be seen with binoculars towards the southern constellation [ http://www.astro.wi…ml ] of Crux [ http://www.astronom…].
