Messier 3 (M3; also NGC 5272) is a globular cluster of stars in the northern

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 Canes Venatici.

Discovery

It was discovered on May 3, 1764, and was the first Messier object to be discovered by Charles Messier himself. Messier originally mistook the object for a nebula without stars. This mistake was corrected after the stars were resolved by William Herschel around 1784. Since then, it has become one of the best-studied globular clusters. Identification of the cluster's unusually large

variable star A variable star is a star whose brightness as seen from Earth (its apparent magnitude) changes with time. This variation may be caused by a change in emitted light or by something partly blocking the light, so variable stars are classified as ...

population was begun in 1913 by American astronomer

Solon Irving Bailey Solon Irving Bailey (December 29, 1854 – June 5, 1931) was an American astronomer and discoverer of the main-belt asteroid 504 Cora, on June 30, 1902. Bailey joined the staff of Harvard College Observatory in 1887. He received an M.A. from th ...

and new variable members continue to be identified up through 2004.

Visibility

Many amateur astronomers consider it one of the finest northern globular clusters, following only

Messier 13 Messier 13 or M13, also designated NGC 6205 and sometimes called the Great Globular Cluster in Hercules or the Hercules Globular Cluster, is a globular cluster of several hundred thousand stars in the constellation of Hercules. Discovery and vis ...

. M3 has an

apparent magnitude Apparent magnitude () is a measure of the brightness of a star or other astronomical object observed from Earth. An object's apparent magnitude depends on its intrinsic luminosity, its distance from Earth, and any extinction of the object's li ...

of 6.2, making it a difficult

naked eye Naked eye, also called bare eye or unaided eye, is the practice of engaging in visual perception unaided by a magnifying, light-collecting optical instrument, such as a telescope or microscope, or eye protection. Vision corrected to normal ...

target even with dark conditions with averted vision. However, with a moderate-sized telescope, the cluster can be seen as a cloudy smudge even in severely light-polluted skies, and can be further defined in darker conditions. It can be found by looking almost exactly halfway along the north-west line that would join Arcturus (α Boötis) to Cor Caroli (α Canum Venaticorum). Using a telescope with a

aperture In optics, an aperture is a hole or an opening through which light travels. More specifically, the aperture and focal length of an optical system determine the cone angle of a bundle of rays that come to a focus in the image plane. An opt ...

, the cluster has a bright core with a diameter of about 6 arcminutes and spans a total of double that.

Characteristics

This cluster is one of the largest and brightest, and is made up of around 500,000 stars. It is estimated to be 11.4 billion years old. It is centered at 32,600

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 (10.0 kpc) away from

Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...

. Messier 3 is quite isolated as it is above the Galactic plane and roughly from the center of 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 ...

. It contains 274 known

s, by far the most found in any globular cluster. These include 133

RR Lyrae variables RR Lyrae variables are periodic variable stars, commonly found in globular clusters. They are used as standard candles to measure (extra) galactic distances, assisting with the cosmic distance ladder. This class is named after the prototype and ...

, of which about a third display the Blazhko effect of long-period modulation. The overall abundance of elements other than hydrogen and helium, what astronomers term 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 ...

, is in the range of −1.34 to −1.50 dex. This value gives the

logarithm In mathematics, the logarithm is the inverse function to exponentiation. That means the logarithm of a number to the base is the exponent to which must be raised, to produce . For example, since , the ''logarithm base'' 10 o ...

of the abundance relative to the Sun; the actual proportion is 3.2–4.6% of the solar abundance. Messier 3 is the prototype for the

Oosterhoff type I A globular cluster is a spheroidal conglomeration of stars. wikt:globular, 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 mil ...

cluster, which is considered "metal-rich". That is, for a globular cluster, Messier 3 has a relatively high abundance of heavier elements. M3map

References

External links

SEDS Messier pages on M3

M3, Galactic Globular Clusters Database page

M3 Photo detail Dark Atmospheres
* * {{DEFAULTSORT:Messier 3 Messier 003 Messier 003

003 003, O03, 0O3, OO3 may refer to: *003, fictional British 00 Agent *003, former emergency telephone number for the Norwegian ambulance service (until 1986) *1990 OO3, the asteroid 6131 Towen * OO3 gauge model railway *''O03 (O2)'' and other related ...

Messier 003 17640503

Discovery

Visibility

Characteristics

References

See also

External links