This rich view of an array of
colorful stars and gas was captured by the Wide Field Imager (WFI)
camera, on the MPG/ESO 2.2-meter telescope at ESO's La Silla Observatory
in Chile. It shows a young open cluster of stars known as NGC 2367, an
infant stellar grouping that lies at the center of an immense and
ancient structure on the margins of the Milky Way.
Credit: ESO/G. Beccari
Discovered from England by the tireless
observer Sir William Herschel on 20 November 1784, the bright star
cluster NGC 2367 lies about 7000 light-years from Earth in the
constellation Canis Major. Having only existed for about five million
years, most of its stars are young and hot and shine with an intense
blue light. This contrasts wonderfully in this new image with the
silky-red glow from the surrounding hydrogen gas.
Open clusters like NGC 2367 are a common sight in spiral galaxies
like the Milky Way, and tend to form in their host's outer regions. On
their travels about the galactic centre, they are affected by the
gravity of other clusters, as well as by large clouds of gas that they
pass close to. Because open clusters are only loosely bound by gravity
to begin with, and because they constantly lose mass as some of their
gas is pushed away by the radiation of the young hot stars, these
disturbances occur often enough to cause the stars to wander off from
their siblings, just as the Sun is believed to have done many years ago.
An open cluster is generally expected to survive for a few hundred
million years before it is completely dispersed.
In the meantime, clusters serve as excellent case studies for stellar
evolution. All the constituent stars are born at roughly the same time
from the same cloud of material, meaning they can be compared alongside
one another with greater ease, allowing their ages to be readily
determined and their evolution mapped.
Like many open clusters, NGC 2367 is embedded within an emission
nebula), from which its stars were born. The remains show up as wisps
and clouds of hydrogen gas, ionised by the ultraviolet radiation being
emitted by the hottest stars. What is more unusual is that, as you begin
to pan out from the cluster and its nebula, a far more expansive
structure is revealed: NGC 2367 and the nebula containing it are thought
to be the nucleus of a larger nebula, known as Brand 16, which in turn
is only a small part of a huge supershell, known as GS234-02.
The GS234-02 supershell lies towards the outskirts of our galaxy, the
Milky Way. It is a vast structure, spanning hundreds of light-years. It
began its life when a group of particularly massive stars, producing
strong stellar winds, created individual expanding bubbles of hot gas.
These neighbouring bubbles eventually merged to form a superbubble, and
the short life spans of the stars at its heart meant that they exploded
as supernovae at similar times, expanding the superbubble even further,
to the point that it merged with other superbubbles, which is when the
supershell was formed. The resulting formation ranks as one of the
largest possible structures within a galaxy.
This concentrically expanding system, as ancient as it is enormous,
provides a wonderful example of the intricate, interrelated structures
that are sculpted in galaxies by the lives and deaths of stars.
Story Source:
The above post is reprinted from
materials provided by
ESO.
Note: Materials may be edited for content and length.
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