NGC 2808 is a

globular cluster A globular cluster is a spheroidal conglomeration of stars. Globular clusters are bound together by gravity, with a higher concentration of stars towards their centers. They can contain anywhere from tens of thousands to many millions of membe ...

in the constellation

Carina Carina may refer to: Places Australia * Carina, Queensland, a suburb in Brisbane * Carina Heights, Queensland, a suburb in Brisbane * Carina, Victoria, a locality in Mildura Serbia * Carina, Osečina, a village in the Kolubara District ...

. The cluster belongs to the

Milky Way The Milky Way is the galaxy that includes our Solar System, with the name describing the galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars that cannot be individually distinguished by the naked eye. ...

, and is one of our home galaxy's most massive clusters, containing more than a million stars. It is estimated to be 12.5-billion years old. The cluster is being disrupted by the

galactic tide A galactic tide is a tidal force experienced by objects subject to the gravitational field of a galaxy such as the Milky Way. Particular areas of interest concerning galactic tides include galactic collisions, the disruption of dwarf or satelli ...

, trailing a long tidal tail.

Star generations

It had been thought that NGC 2808, like typical

s, contains only one generation of stars formed simultaneously from the same material. In 2007, a team of astronomers led by

Giampaolo Piotto Giampaolo or Gianpaolo is an Italian male given name or surname. Its English translation is " John Paul". It is often short for "Giovanni Paolo". Notable people with the name include: Given name * Gianpaolo Ambrosi, Italian luger *Gianpaolo Belli ...

of the

University of Padua The University of Padua ( it, Università degli Studi di Padova, UNIPD) is an Italian university located in the city of Padua, region of Veneto, northern Italy. The University of Padua was founded in 1222 by a group of students and teachers from ...

in Italy investigated

Hubble Space Telescope The Hubble Space Telescope (often referred to as HST or Hubble) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It was not the first space telescope, but it is one of the largest and most vers ...

images of NGC 2808 taken in 2005 and 2006 with Hubble's

Advanced Camera for Surveys The Advanced Camera for Surveys (ACS) is a third-generation axial instrument aboard the Hubble Space Telescope (HST). The initial design and scientific capabilities of ACS were defined by a team based at Johns Hopkins University. ACS was assembl ...

. Unexpectedly, they found that this cluster is composed of three generations of stars, all born within 200 million years of the formation of the cluster. Astronomers have argued that globular clusters can produce only one generation of stars, because the radiation from first generation stars would drive the residual gas not consumed in the first star generation phase out of the cluster. However, the great mass of a cluster such as NGC 2808 may suffice to gravitationally counteract the loss of gaseous matter. Thus, a second and a third generation of stars may form. An alternative explanation for the three star generations of NGC 2808 is that it may actually be the remnant core of a

dwarf galaxy A dwarf galaxy is a small galaxy composed of about 1000 up to several billion stars, as compared to the Milky Way's 200–400 billion stars. The Large Magellanic Cloud, which closely orbits the Milky Way and contains over 30 billion stars, is so ...

that collided with the Milky Way, the

Sausage Galaxy A sausage is a type of meat product usually made from ground meat—often pork, beef, or poultry—along with salt, spices and other flavourings. Other ingredients, such as grains or breadcrumbs may be included as fillers or extenders. W ...

References

External links

* {{DEFAULTSORT:NGC 2808 Globular clusters Carina (constellation) 2808 Canis Major Overdensity

Star generations

See also

References

External links