HR 4887 (HD 111904) is a suspected

variable star A variable star is a star whose brightness as seen from Earth (its apparent magnitude) changes with time. This variation may be caused by a change in emitted light or by something partly blocking the light, so variable stars are classified as e ...

in the

open cluster An open cluster is a type of star cluster made of up to a few thousand stars that were formed from the same giant molecular cloud and have roughly the same age. More than 1,100 open clusters have been discovered within the Milky Way galaxy, an ...

NGC 4755 The Jewel Box (also known as the Kappa Crucis Cluster, NGC 4755, or Caldwell 94) is an open cluster in the constellation Crux, originally discovered by Nicolas Louis de Lacaille in 1751–1752. This cluster was later named the Jewel Box by Jo ...

, which is also known as the Kappa Crucis Cluster or Jewel Box Cluster.

Location

HR 4887 is one of the brightest members of the NGC 4775 open cluster, better known as the Jewel Box Cluster. It forms the apex of the prominent letter "A" 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, and HR 4887 itself, is just to the south-east of β Crucis, the lefthand star of the famous

Southern Cross Crux () is a constellation of the southern sky that is centred on four bright stars in a cross-shaped asterism commonly known as the Southern Cross. It lies on the southern end of the Milky Way's visible band. The name ''Crux'' is Latin for ...

Properties

HR 4887 is a B9 bright supergiant (luminosity class Ia). It is over 100,000 times the luminosity of the sun, partly due to its higher temperature over 12,680 K, and partly to being seventy times larger than the sun. The κ Crucis cluster has a calculated age of 11.2 million years, and HR 4887 itself eight million years. In 1958, HR 4887 was reported to be at visual magnitude 6.80 and on this basis is included in the

New Catalogue of Suspected Variable Stars The ''New Catalogue of Suspected Variable Stars'' (NSV) is a star catalogue A star catalogue is an astronomical catalogue that lists stars. In astronomy, many stars are referred to simply by catalogue numbers. There are a great many different ...

with a range of variation of 5.70 - 6.80. No other observer has measured it far from magnitude 5.75, but measurements of known variable class B stars found that HR 4887 is variable by about a tenth of a magnitude. It is thought likely to be an α Cygni-type variable.

References

External links

* {{DEFAULTSORT:HR 4887 Crux (constellation) 111904 B-type supergiants 062894 4887 Durchmusterung objects J12532189-6019424 Suspected variables Alpha Cygni variables