The NGC 4631 Group is a poorly-defined group of galaxies, about 25 million light years from Earth in the Coma Berenices

Coma Berenices

Coma Berenices is a traditional asterism that has since been defined as one of the 88 modern constellations. It is located near Leo, to which it formerly belonged, and accommodates the North Galactic Pole...

 and Canes Venatici

Canes Venatici

Canes Venatici is one of the 88 official modern constellations. It is a small northern constellation that was created by Johannes Hevelius in the 17th century. Its name is Latin for "hunting dogs", and the constellation is often depicted in illustrations as representing the dogs of Boötes the...

 constellation

Constellation

In modern astronomy, a constellation is an internationally defined area of the celestial sphere. These areas are grouped around asterisms, patterns formed by prominent stars within apparent proximity to one another on Earth's night sky....

s.

Members

• spiral galaxy
  Spiral galaxy
  A spiral galaxy is a certain kind of galaxy originally described by Edwin Hubble in his 1936 work The Realm of the Nebulae and, as such, forms part of the Hubble sequence. Spiral galaxies consist of a flat, rotating disk containing stars, gas and dust, and a central concentration of stars known as...
  
   NGC 4631
  NGC 4631
  NGC 4631 is an edge-on spiral galaxy in the constellation Canes Venatici. This galaxy's slightly distorted wedge shape gives it the appearance of a herring or a whale, whence its nickname...
  
   (Whale Galaxy), brightest galaxy in the group
• interacting galaxies NGC 4656 and NGC 4657
  NGC 4656 and NGC 4657
  NGC 4656 and NGC 4657 are a pair of interacting galaxies located in the constellation Canes Venatici. The pair is sometimes informally called the Hockey Stick Galaxies or the Crowbar Galaxy. Both galaxies are members of the NGC 4631 Group....
  
   (Hockey Stick Galaxies)
• dwarf elliptical galaxy
  Dwarf elliptical galaxy
  Dwarf elliptical galaxies, or dEs, are elliptical galaxies that are much smaller than others. They are classified as dE, and are quite common in galaxy groups and clusters, and are usually companions to other galaxies.- Examples :...
  
   NGC 4627
  NGC 4627
  NGC 4627 is a dwarf elliptical galaxy in the constellation Canes Venatici....
  
  , which is a companion of NGC 4631, is also by default a member of the group, although it is not listed in most catalogs

Aside from these four galaxies, however, the determination of group membership is quite variable. The group lies in a relatively crowded part of the sky near the Virgo Cluster

Virgo Cluster

The Virgo Cluster is a cluster of galaxies whose center is 53.8 ± 0.3 Mly away in the constellation Virgo. Comprising approximately 1300 member galaxies, the cluster forms the heart of the larger Local Supercluster, of which the Local Group is an outlying member...

, so exact determination of the group membership is extremely difficult. Some studies have estimated that the NGC 4631 Group contains as few as 5 galaxies, while others place the estimate as high as 27. Additionally, it is unclear as to whether the galaxies near NGC 4631 and NGC 4656/NGC4657 form one large group or two smaller groups.

See also

Virgo Cluster

Virgo Cluster

The Virgo Cluster is a cluster of galaxies whose center is 53.8 ± 0.3 Mly away in the constellation Virgo. Comprising approximately 1300 member galaxies, the cluster forms the heart of the larger Local Supercluster, of which the Local Group is an outlying member...

 - a large cluster of galaxies that is near the NGC 4631 group

External links

• The Whale and the Hockey Stick Astronomy Picture of the Day
  Astronomy Picture of the Day
  Astronomy Picture of the Day is a website provided by NASA and Michigan Technological University . According to the website, "Each day a different image or photograph of our universe is featured, along with a brief explanation written by a professional astronomer."The photograph is not necessarily...
  
  of 2009 August 21