Messier 48 or M48, also known as NGC 2548, is an
open cluster of stars in the
equatorial constellation
A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object.
The origins of the e ...
of
Hydra
Hydra generally refers to:
* Lernaean Hydra, a many-headed serpent in Greek mythology
* ''Hydra'' (genus), a genus of simple freshwater animals belonging to the phylum Cnidaria
Hydra or The Hydra may also refer to:
Astronomy
* Hydra (constel ...
. It sits near Hydra's westernmost limit with
Monoceros,
[ about to the east and slightly south of Hydra's brightest star, Alphard.][ This grouping was discovered by Charles Messier in 1771, but there is no cluster precisely where Messier indicated; he made an error, as he did with M47. The value that he gave for the ]right ascension
Right ascension (abbreviated RA; symbol ) is the angular distance of a particular point measured eastward along the celestial equator from the Sun at the March equinox to the (hour circle of the) point in question above the earth.
When paired w ...
matches, however, his declination
In astronomy, declination (abbreviated dec; symbol ''δ'') is one of the two angles that locate a point on the celestial sphere in the equatorial coordinate system, the other being hour angle. Declination's angle is measured north or south of the ...
is off by five degrees.[ Credit for discovery is sometimes given instead to Caroline Herschel in 1783.][ Her nephew ]John Herschel
Sir John Frederick William Herschel, 1st Baronet (; 7 March 1792 – 11 May 1871) was an English polymath active as a mathematician, astronomer, chemist, inventor, experimental photographer who invented the blueprint and did botanical wor ...
described it as, "a superb cluster which fills the whole field; stars of 9th and 10th to the 13th magnitude – and none below, but the whole ground of the sky on which it stands is singularly dotted over with infinitely minute points".[
M48 is visible to the naked eye under good atmospheric conditions. The brightest member is the star HIP 40348 at visual magnitude 8.3.][ The cluster is located some from the Sun.][ The age estimated from ]isochrone
Isochrone may refer to:
* Stellar isochrone, the curve on the Hertzsprung–Russell diagram representing stars of the same age
*Isochrone curve, the curve (a cycloid) for which objects starting at different points finish at the same time and point ...
s is Myr, while gyrochronology Gyrochronology is a method for estimating the age of a low-mass (cool) Main sequence, main sequence star (spectral class F8 V or later) from its stellar rotation, rotation period. The term is derived from the Greek language, Greek words ''gyros, chr ...
age estimate is Myr – in good agreement.[ This makes it intermediate in age between the Pleiades, at around 100 Myr, and the Hyades, at about 650 Myr. The ]metallicity
In astronomy, metallicity is the abundance of elements present in an object that are heavier than hydrogen and helium. Most of the normal physical matter in the Universe is either hydrogen or helium, and astronomers use the word ''"metals"'' as a ...
of the cluster, based on the abundance of iron (Fe), is e/H= , where −1 would be ten times lower than in the Sun. It is more metal-poor than the Pleiades, Hyades, and Praesepe clusters.[
The cluster has a tidal radius of ][ with at least 438][ members and a mass of .][ The general structure of the cluster is fragmented and lumpy, which may be due to interactions with the galactic disk. The cluster is now subdivided into three groups, each of which has its own collective ]proper motion
Proper motion is the astrometric measure of the observed changes in the apparent places of stars or other celestial objects in the sky, as seen from the center of mass of the Solar System, compared to the abstract background of the more dista ...
.[
]
See also
* List of Messier objects
References
External links
Messier 48, SEDS Messier pages
*
{{DEFAULTSORT:Messier 48
Messier 048
Orion–Cygnus Arm
Messier 048
048
48 may refer to:
* 48 (number)
* one of the years 48 BC, AD 48, 1948, 2048
* ''48'' (novel)
* 48'' (magazine)
* "48", a song by Tyler, the Creator from the album ''Wolf''
* 48, a phone network brand of Three Ireland
* "Forty Eight", a song by ...
Messier 048
17710219