NGC 7419 is an open cluster in the constellation
Cepheus. It is heavily reddened and notable for containing five
red supergiants, the highest number known in any cluster until the end of the 20th century, but probably no
blue supergiants.
Members
The brightest of the five red supergiants is the exceptionally cool
MY Cephei
MY Cephei (IRC +60375) is a red supergiant located in open cluster NGC 7419 in the constellation of Cepheus (constellation), Cepheus. It is a semiregular variable star with a maximum brightness of magnitude 14.4 and a minimum of magnit ...
.
[ It has a spectral type of M7.5 which is one of the latest spectral types of any supergiant, although analysis is made difficult by the lack of comparable standard stars.][
The brightest hot stars in the cluster have a spectral type of BC2, indicating B2 stars with enhanced levels of carbon.][ One has a bright giant luminosity class of II, while the other has a luminosity class of Ib-II, indicating it is either a bright giant or supergiant. The hotter stars of the cluster are visually faint due to around six magnitudes of interstellar extinction.][
The lack of blue supergiants, particularly in a cluster of just the right size and age to include five red supergiants, is unusual. Such low ratios of blue:red supergiants occur in low ]metallicity
In astronomy, metallicity is the abundance of elements present in an object that are heavier than hydrogen and helium. Most of the normal physical matter in the Universe is either hydrogen or helium, and astronomers use the word ''"metals"'' as a ...
clusters, but NGC 7419 is young and has near-solar metallicity. Rapidly rotating stars may account for this evolutionary trend, encouraging high mass loss and rapid evolution of massive stars into red supergiants. This conclusion is also consistent with the high proportion of Be stars in the cluster.[
The age of the cluster is calculated to be million years. Clusters of this age are expected to have a main sequence turnoff at spectral type B1, and this is seen in NGC 7419. of B-type stars alone are observed, implying a total cluster mass of .][
]
Non-members
Visible in the same field and as prominent as the red supergiants in infrared images is the carbon star
A carbon star (C-type star) is typically an asymptotic giant branch star, a luminous red giant, whose atmosphere contains more carbon than oxygen. The two elements combine in the upper layers of the star, forming carbon monoxide, which consumes mos ...
MZ Cephei, which is much closer to us than NGC 7419.[ It is a slow irregular variable star with a range of 14.7 - 15.4.][
The visually brightest star in the core region of the cluster is a yellow giant, placed at around 500 parsecs by ]Gaia
In Greek mythology, Gaia (; from Ancient Greek , a poetical form of , 'land' or 'earth'),, , . also spelled Gaea , is the personification of the Earth and one of the Greek primordial deities. Gaia is the ancestral mother—sometimes parthenog ...
astrometry.[ The even brighter nearby star HD 216721 is also a foreground object.][ Further out still from the centre of the cluster is the 7th magnitude eclipsing binary V453 Cephei, around 250 parsecs distant from us.]
See also
*Stephenson 2
Stephenson 2 , also known as RSGC2 (''Red Supergiant Cluster 2''), is a young massive open cluster belonging to the Milky Way galaxy. It was discovered in 1990 as a cluster of red supergiants in a photographic, deep infrared survey by the astrono ...
*RSGC1
RSGC1 (''Red Supergiant Cluster 1'') is a young massive open cluster in the Milky Way galaxy. It was discovered in 2006 in the data generated by several infrared surveys, named for the unprecedented number of red supergiant members. The cluster ...
References
External links
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{{DEFAULTSORT:NGC 7419
Cepheus (constellation)
7419
Open clusters