IC 349, also known as Barnard's Merope Nebula, is a
nebula
A nebula ('cloud' or 'fog' in Latin; pl. nebulae, nebulæ or nebulas) is a distinct luminescent part of interstellar medium, which can consist of ionized, neutral or molecular hydrogen and also cosmic dust. Nebulae are often star-forming regio ...
which lies 3500
AUs (0.06
light year
A light-year, alternatively spelled light year, is a large unit of length used to express astronomical distances and is equivalent to about 9.46 trillion kilometers (), or 5.88 trillion miles ().One trillion here is taken to be 1012 ...
s)
from the star
Merope in the
Pleiades
The Pleiades (), also known as The Seven Sisters, Messier 45 and other names by different cultures, is an asterism and an open star cluster containing middle-aged, hot B-type stars in the north-west of the constellation Taurus. At a distance ...
cluster
may refer to:
Science and technology Astronomy
* Cluster (spacecraft), constellation of four European Space Agency spacecraft
* Asteroid cluster, a small asteroid family
* Cluster II (spacecraft), a European Space Agency mission to study th ...
.
It was discovered in November 1890 by the American astronomer
Edward Emerson Barnard
Edward Emerson Barnard (December 16, 1857 – February 6, 1923) was an American astronomer. He was commonly known as E. E. Barnard, and was recognized as a gifted observational astronomer. He is best known for his discovery of the high proper mo ...
, who described it as "a new and comparatively bright round cometary nebula close south and following Merope (23 Tau) ... about 30" in diameter, of the 13 (magnitude), gradually brighter in the middle, and very cometary in appearance.”
The British astronomer
Charles Pritchard, however, disputed Barnard's discovery announcement, claiming to have discovered it himself on a photographic plate obtained at Oxford on 29 January 1889. Pritchard dismissed IC 349 as an "apparently insignificant fleck," dismissing a distinct identity for the object and instead regarding it simply as the brightest part of the broader reflection nebulosity enveloping the Pleiades.
agreed with Barnard's estimation of the importance of the nebula, calling it "far more interesting than any of the nebulae heretofore discovered in the Pleiades by visual and photographic method" and "one of the most singular objects in the heavens."
Burnham further speculated as to whether IC 349 was kinematically related to the Pleiades, suggesting that its proper motion might provide a definitive answer.
IC 349 may be an example of a cold, dense, very small-scale condensation of the
interstellar medium
In astronomy, the interstellar medium is the matter and radiation that exist in the space between the star systems in a galaxy. This matter includes gas in ionic, atomic, and molecular form, as well as dust and cosmic rays. It fills interstella ...
.
Morphologically, it appears to have a roughly pentagonal shape with a bright knot situated closest to
Merope. This knot was examined for evidence of an embedded protostar, but none was found to a luminosity upper limit of 0.23 ± 0.05 times the luminosity of the
Sun.
This implies an upper limit of 0.15 times the mass of the Sun for a deuterium-burning protostar embedded in the knot, whose existence is further rendered dubious by a lack of emission lines characteristic of pre–
Main Sequence
In astronomy, the main sequence is a continuous and distinctive band of stars that appears on plots of stellar color versus brightness. These color-magnitude plots are known as Hertzsprung–Russell diagrams after their co-developers, Ejnar Her ...
stars in its optical spectrum. Further searches in the near-infrared also failed to show any evidence of an embedded protostar in the bright knot, showing only wavelength-dependent scattering of light consistent with the presence of very fine dust particles.
Analysis of the nebula's space motion indicate it does not share the velocity and direction of the Pleiades, suggesting a chance encounter between the objects.
Because IC 349 shares the velocity of molecular gas in the nearby
Taurus Molecular Cloud complex, it may have originated there.
[
]
IC 349 is now sufficiently close to
Merope that its envelope is undergoing disruption by either the star's
radiation pressure
Radiation pressure is the mechanical pressure exerted upon any surface due to the exchange of momentum between the object and the electromagnetic field. This includes the momentum of light or electromagnetic radiation of any wavelength that is a ...
, a
stellar wind
A stellar wind is a flow of gas ejected from the upper atmosphere of a star. It is distinguished from the bipolar outflows characteristic of young stars by being less collimated, although stellar winds are not generally spherically symmetric. ...
, or both.
References
IC 349 (Barnard's Merope Nebula)
External links
*
Pleiades
Taurus (constellation)
0349
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