NGC 3603
Encyclopedia
NGC 3603 is an open cluster
of star
s situated in the Carina
spiral arm of the Milky Way
around 20,000 light-years away from the Solar System.
NGC 3603 has been subject to intense study as a starburst region for more than a century because it represents a unique combination of proximity, low visual extinction
, brightness and compactness.
It was observed by John Herschel
on the 14th of March 1834 during his visit to South Africa, who remarked that it was "a very remarkable object...perhaps a globular cluster
". Herschel catalogued it as nebula
3334 in his Results of Astronomical Observations made at the Cape of Good Hope, published in 1847. In 1864 the Royal Society
published his General Catalogue of Nebulae and Clusters, where he listed it as number 2354. It was subsequently incorporated into the New General Catalogue
as by J. L. E. Dreyer as NGC 3603.
and plasma
known as a H II region
in the Milky Way. HD 97950
is the central star of star cluster
, the densest concentration of very massive stars known in the galaxy.
Strong ultraviolet radiation and stellar winds have cleared the gas and dust, giving an unobscured view of the cluster.
Three prominent Wolf-Rayet stars have been detected within the cluster. These three massive stars have been observed and their solar mass
measured using the Very Large Telescope
. The largest of the three, NGC 3603-A1 is a blue double star
that orbit around each other once every 3.77 days. The two combined have a solar mass
that is 200 times more massive than our Sun: (A1-a) is the largest known star in our galaxy with an estimated mass of 116 solar masses, while its companion (A1-b) has a mass of 89 solar masses.
NGC 3603 is visible in the telescope as a small rather insignificant nebulosity with a yellowish tinge due to the effects of interstellar absorption. In the mid-1960s optical studies coincided with radio astronomical observations which showed it to be an extremely strong thermal radio source. Later observations in other galaxies introduced the concept of 'starburst' regions, in some cases whole galaxies, of extremely rapid star formation and NGC 3603 is now considered to be such a region.
In 1987 a supernova (known as SN 1987A
) occurred in the Large Magellanic Cloud
. This was the first supernova to be close enough for detailed observation with satellite based telescopes. One result was the discovery that prior to the main explosion it had thrown off a relatively small amount of material in a very distinctive pattern, a bit like an hourglass perpendicular to a detached glowing ring. One star in NGC 3603 (Sher 25
, the number comes from the 1960s optical observations) was found to have thrown off matter in a pattern similar to that found for the supernova 1987A. This coincidence has aroused intense interest.
Open cluster
An open cluster is a group 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, and many more are thought to exist...
of star
Star
A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...
s situated in the Carina
Carina (constellation)
Carina is a constellation in the southern sky. Its name is Latin for the keel of a ship, and it was formerly part of the larger constellation of Argo Navis until that constellation was divided in three.-Stars:...
spiral arm of the Milky Way
Milky Way
The Milky Way is the galaxy that contains the Solar System. This name derives from its appearance as a dim un-resolved "milky" glowing band arching across the night sky...
around 20,000 light-years away from the Solar System.
NGC 3603 has been subject to intense study as a starburst region for more than a century because it represents a unique combination of proximity, low visual extinction
Visual extinction
Visual extinction is a neurological disorder which occurs following damage to the parietal lobe of the brain. It is similar to, but distinct from, hemispatial neglect...
, brightness and compactness.
It was observed by John Herschel
John Herschel
Sir John Frederick William Herschel, 1st Baronet KH, FRS ,was an English mathematician, astronomer, chemist, and experimental photographer/inventor, who in some years also did valuable botanical work...
on the 14th of March 1834 during his visit to South Africa, who remarked that it was "a very remarkable object...perhaps a globular cluster
Globular cluster
A globular cluster is a spherical collection of stars that orbits a galactic core as a satellite. Globular clusters are very tightly bound by gravity, which gives them their spherical shapes and relatively high stellar densities toward their centers. The name of this category of star cluster is...
". Herschel catalogued it as nebula
Nebula
A nebula is an interstellar cloud of dust, hydrogen gas, helium gas and other ionized gases...
3334 in his Results of Astronomical Observations made at the Cape of Good Hope, published in 1847. In 1864 the Royal Society
Royal Society
The Royal Society of London for Improving Natural Knowledge, known simply as the Royal Society, is a learned society for science, and is possibly the oldest such society in existence. Founded in November 1660, it was granted a Royal Charter by King Charles II as the "Royal Society of London"...
published his General Catalogue of Nebulae and Clusters, where he listed it as number 2354. It was subsequently incorporated into the New General Catalogue
New General Catalogue
The New General Catalogue of Nebulae and Clusters of Stars is a well-known catalogue of deep sky objects in astronomy. It contains 7,840 objects, known as the NGC objects...
as by J. L. E. Dreyer as NGC 3603.
Features
It is surrounded by the most massive visible cloud of glowing gasGas
Gas is one of the three classical states of matter . Near absolute zero, a substance exists as a solid. As heat is added to this substance it melts into a liquid at its melting point , boils into a gas at its boiling point, and if heated high enough would enter a plasma state in which the electrons...
and plasma
Plasma (physics)
In physics and chemistry, plasma is a state of matter similar to gas in which a certain portion of the particles are ionized. Heating a gas may ionize its molecules or atoms , thus turning it into a plasma, which contains charged particles: positive ions and negative electrons or ions...
known as a H II region
H II region
An H II region is a large, low-density cloud of partially ionized gas in which star formation has recently taken place. The short-lived, blue stars forged in these regions emit copious amounts of ultraviolet light, ionizing the surrounding gas...
in the Milky Way. HD 97950
HD 97950
HD 97950, is a multiple system consisting of a core of 4 stars A1-A3 and B, plus 5 other stars. The system is sometimes considered a stellar cluster....
is the central star of star cluster
Star cluster
Star clusters or star clouds are groups of stars. Two types of star clusters can be distinguished: globular clusters are tight groups of hundreds of thousands of very old stars which are gravitationally bound, while open clusters, more loosely clustered groups of stars, generally contain less than...
, the densest concentration of very massive stars known in the galaxy.
Strong ultraviolet radiation and stellar winds have cleared the gas and dust, giving an unobscured view of the cluster.
Three prominent Wolf-Rayet stars have been detected within the cluster. These three massive stars have been observed and their solar mass
Solar mass
The solar mass , , is a standard unit of mass in astronomy, used to indicate the masses of other stars and galaxies...
measured using the Very Large Telescope
Very Large Telescope
The Very Large Telescope is a telescope operated by the European Southern Observatory on Cerro Paranal in the Atacama Desert of northern Chile. The VLT consists of four individual telescopes, each with a primary mirror 8.2m across, which are generally used separately but can be used together to...
. The largest of the three, NGC 3603-A1 is a blue double star
Double star
In observational astronomy, a double star is a pair of stars that appear close to each other in the sky as seen from Earth when viewed through an optical telescope. This can happen either because the pair forms a binary star, i.e...
that orbit around each other once every 3.77 days. The two combined have a solar mass
Solar mass
The solar mass , , is a standard unit of mass in astronomy, used to indicate the masses of other stars and galaxies...
that is 200 times more massive than our Sun: (A1-a) is the largest known star in our galaxy with an estimated mass of 116 solar masses, while its companion (A1-b) has a mass of 89 solar masses.
NGC 3603 is visible in the telescope as a small rather insignificant nebulosity with a yellowish tinge due to the effects of interstellar absorption. In the mid-1960s optical studies coincided with radio astronomical observations which showed it to be an extremely strong thermal radio source. Later observations in other galaxies introduced the concept of 'starburst' regions, in some cases whole galaxies, of extremely rapid star formation and NGC 3603 is now considered to be such a region.
In 1987 a supernova (known as SN 1987A
SN 1987A
SN 1987A was a supernova in the outskirts of the Tarantula Nebula in the Large Magellanic Cloud, a nearby dwarf galaxy. It occurred approximately 51.4 kiloparsecs from Earth, approximately 168,000 light-years, close enough that it was visible to the naked eye. It could be seen from the Southern...
) occurred in the Large Magellanic Cloud
Large Magellanic Cloud
The Large Magellanic Cloud is a nearby irregular galaxy, and is a satellite of the Milky Way. At a distance of slightly less than 50 kiloparsecs , the LMC is the third closest galaxy to the Milky Way, with the Sagittarius Dwarf Spheroidal and Canis Major Dwarf Galaxy lying closer to the center...
. This was the first supernova to be close enough for detailed observation with satellite based telescopes. One result was the discovery that prior to the main explosion it had thrown off a relatively small amount of material in a very distinctive pattern, a bit like an hourglass perpendicular to a detached glowing ring. One star in NGC 3603 (Sher 25
Sher 25
Sher 25 is an old blue supergiant star located approximately 20,000 light years from the Sun in the H II region NGC 3603 of the Milky Way galaxy. It's a spectral type B1.5Iab star with an apparent magnitude is 12.2, and located at right ascension , declination in the constellation Carina...
, the number comes from the 1960s optical observations) was found to have thrown off matter in a pattern similar to that found for the supernova 1987A. This coincidence has aroused intense interest.