DU Crucis

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The centre of NGC 4755, with DU Cru at top right. Credit to NASA/ESA and Jesús Maíz Apellániz (Instituto de Astrofísica de Andalucía, Icons-flag-es.png Spain)

DU Crucis
Observation data
Epoch J2000      Equinox J2000
Constellation Crux
Right ascension 12h 53m 41.33485s[1]
Declination −60° 20′ 57.9647″[1]
Apparent magnitude (V) 7.45[2]
Spectral type M2- Iab[3]
U−B color index +2.57[2]
B−V color index +2.22[2]
Variable type Lc[4]
Radial velocity (Rv)−21.24[5] km/s
Proper motion (μ) RA: −4.703[6] mas/yr
Dec.: −1.162[6] mas/yr
Parallax (π)0.5075 ± 0.0516[6] mas
Distance2,600[7][8] pc
Absolute magnitude (MV)−5.52[9]
Radius598[10] R
Diameter598[10] D
Luminosity46,600 L
Temperature3,467 K
Other designations
DU Cru, CD−59°4459, HIP 62918, SAO 252073, 2MASS J12534132-6020578, IRAS 12506-6004
Database references

DU Crucis is a red supergiant and slow irregular variable star in the open cluster NGC 4755, which is also known as the Kappa (κ) Crucis Cluster or Jewel Box Cluster.


A Snapshot of the Jewel Box cluster (Credit: ESO VLT).

DU Crucis is one of the brighter members of the Jewel Box Cluster and the brightest red supergiant, strongly contrasting with the other bright members which are blue supergiants.[11] It is part of the central bar of the prominent letter "A"-shaped asterism at the centre of the cluster. The cluster is part of the larger Centaurus OB1 association and lies about 8,500 light years away.

The cluster is just to the south-east of β Crucis, the lefthand star of the Southern Cross.


DU Crucis is an M2 intermediate luminosity supergiant (luminosity class Iab). Despite its low temperature, it is 46,600 times the luminosity of the sun, due to its very large size. The κ Crucis cluster has a calculated age of 11.2 million years.[7]


Photometry from the Hipparcos satellite mission showed that DU Crucis varies in brightness with an amplitude of 0.44 magnitudes.[12] No periodicity could be detected in the variations and it was classified as a slow irregular variable of type Lc, indicating a supergiant.[4]


  1. 1.0 1.1 van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics 474 (2): 653–664, arXiv:0708.1752, Bibcode 2007A&A...474..653V, doi:10.1051/0004-6361:20078357.
  2. 2.0 2.1 2.2 Dachs, J.; Kaiser, D. (November 1984), "UBV photometry of the southern galactic cluster NGC 4755 = Kappa Crucis", Astronomy and Astrophysics Supplement Series 58: 411–429, Bibcode 1984A&AS...58..411D.
  3. Keenan, Philip C.; McNeil, Raymond C. (1989). "The Perkins catalog of revised MK types for the cooler stars". Astrophysical Journal Supplement Series 71: 245. Bibcode 1989ApJS...71..245K. doi:10.1086/191373. ISSN 0067-0049.
  4. 4.0 4.1 Samus, N. N.Expression error: Unrecognized word "etal". (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/gcvs. Originally published in: 2009yCat....102025S 1. Bibcode 2009yCat....102025S.
  5. Mermilliod, J. C.; Mayor, M.; Udry, S. (2008). "Red giants in open clusters. XIV. Mean radial velocities for 1309 stars and 166 open clusters". Astronomy and Astrophysics 485: 303–314. Bibcode 2008A&A...485..303M. doi:10.1051/0004-6361:200809664.
  6. 6.0 6.1 6.2 Brown, A. G. A. (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics 616: A1. arXiv:1804.09365. Bibcode 2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  7. 7.0 7.1 Aidelman, Y.; Cidale, L. S.; Zorec, J.; Arias, M. L. (2012). "Open clusters. I. Fundamental parameters of B stars in NGC 3766 and NGC 4755". Astronomy & Astrophysics 544: A64. Bibcode 2012A&A...544A..64A. doi:10.1051/0004-6361/201219069.
  8. Corti, M. A.; Orellana, R. B. (2013). "Members of Centaurus OB1 and NGC 4755: New spectroscopic and astrometric studies". Astronomy & Astrophysics 553: A108. Bibcode 2013A&A...553A.108C. doi:10.1051/0004-6361/201220743.
  9. 9.0 9.1 Harris, G. L. H. (1976). "Evolved stars in open clusters". Astrophysical Journal 30: 451. Bibcode 1976ApJS...30..451H. doi:10.1086/190368.
  10. {{{1}}}
  11. Kharchenko, N. V.; Piskunov, A. E.; Röser, S.; Schilbach, E.; Scholz, R.-D. (2004). "Astrophysical supplements to the ASCC-2.5. II. Membership probabilities in 520 Galactic open cluster sky areas". Astronomische Nachrichten 325 (9): 740–748. Bibcode 2004AN....325..740K. doi:10.1002/asna.200410256.
  12. Adelman, Saul J. (2001). "Stars with the Largest Hipparcos Photometric Amplitudes". Baltic Astronomy 10: 589. Bibcode 2001BaltA..10..589A. doi:10.1515/astro-2001-0403.

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