Detail View: NASA Astronomy Picture of the Day Collection: NGC 4755: A Jewel Box of Stars

Title: 
NGC 4755: A Jewel Box of Stars
Explanation: 
The great variety of star colors in this open cluster [ http://www.seds.org/messier/open.html ] underlies its name: The Jewel Box [ http://www.seds.org/messier/xtra/ngc/n4755.html ]. One of the bright central stars is a red supergiant, in contrast to the many blue stars that surround it. The cluster [ http://adsabs.harvard.edu/cgi-bin/nph- bib_query?bibcode=1963MNRAS.126...11F ], also known as Kappa Crucis [ http://adsabs.harvard.edu/cgi-bin/nph- bib_query?bibcode=1984A%26AS...56..373D ] contains just over 100 stars, and is about 10 million years old. Open clusters [ http://antwrp.gsfc.nasa.gov/apod/open_clusters.html ] are younger, contain few stars, and contain a much higher fraction of blue stars than do globular clusters [ http://antwrp.gsfc.nasa.gov/apod/globular_clusters.html ]. This Jewel Box [ http://www.iucaa.ernet.in/~vam/akksem/clusters/ngc4755.html ] lies about 7500 light-years [ http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/980211a.html ] away, so the light that we see today was emitted from the cluster before even the Great Pyramids [ http://www.pbs.org/wgbh/nova/pyramid/ ] in Egypt [ http://www.cia.gov/cia/publications/factbook/geos/eg.html ] were built. The Jewel Box, pictured above [ http://www.mso.anu.edu.au/~bessell/thumbnails/ ], spans about 20 light-years, and can be seen with binoculars towards the southern constellation [ http://www.astro.wisc.edu/~dolan/constellations/extra/constellations.ht ml ] of Crux [ http://www.astronomical.org/constellations/cru.html ].
Credit and Copyright: 
Michael Bessell (RSAA, ANU [ http://msowww.anu.edu.au/ ]), MSO [ http://msowww.anu.edu.au/msovc/ ]
keyword: 
Jewel Box
facet_where: 
Egypt
facet_what: 
Crux
original url: 
http://antwrp.gsfc.nasa.gov/apod/ap010618.html
UID: 
SPD-APOD-ap010618