Jewel Box (star cluster)

Coordinates: Sky map 12h 53m 42s, −60° 22′ 00″
Source: Wikipedia, the free encyclopedia.
This article is about article is about the star cluster. For other uses, see Jewel box.
Jewel Box
kly[2] (1.968 kpc[3])
Physical characteristics
Mass– M☉
Radius–
Estimated age16 Myr[3]
–
Other designationsHerschel's Jewel Box,[1] Kappa Crucis Cluster,[1] NGC 4755,[1] Caldwell 94,[4] Cr 264
Associations
ConstellationCrux
See also: Open cluster, List of open clusters

The Jewel Box (also known as the Kappa Crucis Cluster, NGC 4755, or Caldwell 94) is an

Nicolas Louis de Lacaille in 1751–1752. This cluster was later named the Jewel Box by John Herschel when he described its telescopic appearance as "...a superb piece of fancy jewellery". It is easily visible to the naked eye as a hazy star some 1.0° southeast of the first-magnitude star Mimosa (Beta Crucis). This hazy star was given the Bayer star designation "Kappa Crucis", from which the cluster takes one of its common names. The modern designation Kappa Crucis has been assigned to one of the stars in the base of the A-shaped asterism
of the cluster

This cluster is one of the youngest known, with an estimated age of 14 million years. It has a total integrated

light years
from Earth, and contains just over 100 stars.

Discovery and observation

The Jewel Box as a star cluster was first found by

Cœlum Australe Stelliferum at the Cape of Good Hope in South Africa. He saw this as a nebulous cluster in his small 12mm. (½-inch) telescope, but was first to recognise it as a group of many stars.[5][6]
The name "Jewel Box" comes from John Herschel's own description of it: "...this cluster, though neither a large nor a rich one, is yet an extremely brilliant and beautiful object when viewed through an instrument of sufficient aperture to show distinctly the very different colour of its constituent stars, which give it the effect of a superb piece of fancy jewellery."[5]

Herschel recorded the positions of just over 100 members of the cluster in 1834–1838.[7]

Prominent members

The central part of the cluster is framed by bright stars making up an A-shaped asterism.[8] The upper tip of this asterism is HD 111904 (

DS Cru (HD 111613, HR 4876), which lies well beyond the A asterism. It is a B9.5 α Cyg variable supergiant with an average visual brightness of magnitude 5.72, but is thought to be a foreground object.[9]

The bar of the "A" consists of a line of four stars. On the right (south) is

eclipsing binary. Next to it is BV Cru, a magnitude 8.662 B0.5 giant and Beta Cephei variable. Next in line is DU Cru, an M2 red supergiant that varies irregularly between magnitude 7.1 and 7.6. The last of the four is CC Cru, a magnitude 7.83 B2 giant and ellipsoidal variable.[9]

Each leg of the base of the asterism's outline is marked by a blue supergiant star. HD 111990 (HIP 62953) is magnitude 6.77 and B1/2. The star κ Cru itself is magnitude 5.98 and B3.[9]

Physical characteristics

The Jewel Box cluster is one of the youngest known

Milky Way galaxy.[10]

Calculating its distance is difficult due to the proximity of the Coalsack Nebula, which obscures some of its light.[11]

Observation

The Jewel Box cluster is regarded as one of the finest objects in the southern sky.[12] It is visible to the naked eye as a hazy object of the fourth magnitude.

Beta Crucis as a guide, and appears as a fourth magnitude object.[14] It is impressive when viewed with binoculars or a small or large telescope. Three members along the crossbar of the A-shaped asterism lie in a straight line known as the 'traffic lights' due to their varying colours.[15]

Gallery

  • Wide Field Image of the Jewel Box
    Wide Field Image of the Jewel Box
  • Digitized Sky Survey 2 image of the Jewel Box
    Digitized Sky Survey 2 image of the Jewel Box
  • Hubble image of the Jewel Box
    Hubble image of the Jewel Box
  • Putting the images in perspective
    Putting the images in perspective
  • The Jewel Box seen through a small amateur telescope
    The Jewel Box seen through a small amateur telescope

References

  1. ^ a b c d e "NGC 4755". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2006-12-14.
  2. ^ "WEBDA Open cluster". Results for NGC 4755. Retrieved 2007-01-12.
  3. ^
    S2CID 54222753
    .
  4. ^ "Deepsky Observer Companion Database". Results for NGC 4755. Retrieved 2013-06-08.
  5. ^ a b http://www.docdb.net/show_object.php?id=ngc_4755, DOCdb : Jewel Box
  6. ^ James, Andrew (22 April 2016). "History of the Jewel Box Part One : 1752–1834". Southern Astronomical Delights. Retrieved 2016-04-22.
  7. Bibcode:1949MNSSA...8...30T
    .
  8. ^ James, Andrew (22 April 2016). "NGC 4755 : The Jewel Box "The Jewel of the South" : Introduction". Southern Astronomical Delights. Retrieved 2016-04-22.
  9. ^
    doi:10.1002/asna.200410256
    .
  10. ISBN 978-0-486-23568-4
    .
  11. ISBN 978-0-521-78190-9
    .
  12. ISBN 978-0-521-58570-5
    .
  13. ISBN 978-0-691-13556-4
    .
  14. ISBN 978-1-4419-0325-9
    .
  15. ISBN 978-1-85233-709-4
    .

External links

Wikimedia Commons has media related to NGC 4755.


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