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Messier 3

Globular cluster in the constellation Canes Venatici

Messier 3
Globular cluster Messier 3 in Canes Venatici
Observation data (J2000 epoch)
Class	VI[1][2]
Constellation	Canes Venatici
Right ascension	13h42m 11.62s[3]
Declination	+28° 22′ 38.2″[3]
Distance	33.9 kly (10.4 kpc)[4]
Apparent magnitude (V)	6.39[5]
Apparent dimensions (V)	18′.0
Physical characteristics
Absolute magnitude	-8.93
Mass	4.5×105[6] M☉
Radius	103.0 pc (335.9 ly)[7]
Tidal radius	113 pc (370 ly)[mean][7]
Metallicity	${\displaystyle {\begin{smallmatrix}\left[{\ce {Fe}}/{\ce {H}}\right]\end{smallmatrix}}}$ = –1.34[8] dex
Estimated age	11.39 Gyr[8]
Other designations	NGC 5272[9]
See also: Globular cluster, List of globular clusters

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

It was discovered on May 3, 1764,^[10] 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.^[11] Since then, it has become one of the best-studied globular clusters. Identification of the cluster's unusually large variable star population was begun in 1913 by American astronomer Solon Irving Bailey and new variable members continue to be identified up through 2004.^[12]

Many amateur astronomers consider it one of the finest northern globular clusters, following only Messier 13.^[1] M3 has an apparent magnitude of 6.2,^[9] making it a difficult naked eye target^[13] 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 25 cm (9.8 in) aperture, the cluster has a bright core with a diameter of about 6 arcminutes and spans a total of double that.^[1]

This cluster is one of the largest and brightest, and is made up of around 500,000 stars.^[11] It is estimated to be 11.4 billion years old.^[8] It is centered at 32,600 light-years (10.0 kpc) away from Earth.^[14]

Messier 3 is quite isolated as it is 31.6 kly (9.7 kpc) above the Galactic plane and roughly 38.8 kly (11.9 kpc) from the center of the Milky Way. It contains 274 known variable stars, by far the most found in any globular cluster. These include 133 RR Lyrae variables, 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, is in the range of −1.34 to −1.50 dex. This value gives the logarithm 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 cluster, which is considered "metal-rich". That is, for a globular cluster, Messier 3 has a relatively high abundance of heavier elements.^[15]

• List of Messier objects

Wikimedia Commons has media related to Messier 3.

• SEDS Messier pages on M3
• M3, Galactic Globular Clusters Database page
• M3 Photo detail Dark Atmospheres
• Merrifield, Michael. "M3 – Globular Cluster". Deep Sky Videos. Brady Haran.
• Messier 3 on WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Astrophoto, Sky Map, Articles and images

Stars

Outer space