Messier 53 (also known as M53 or NGC 5024) is a

globular cluster A globular cluster is a spheroidal conglomeration of stars that is bound together by gravity, with a higher concentration of stars towards its center. It can contain anywhere from tens of thousands to many millions of member stars, all orbiting ...

in the

Coma Berenices constellation Coma Berenices is an ancient asterism in the northern sky, which has been defined as one of the 88 modern constellations. It is in the direction of the fourth galactic quadrant, between Leo and Boötes, and it is visible in both hemispheres ...

. It was discovered by

Johann Elert Bode Johann Elert Bode (; 19 January 1747 – 23 November 1826) was a German astronomer known for his reformulation and popularisation of the Titius–Bode law. Bode determined the orbit of Uranus and suggested the planet's name. Life and career B ...

in 1775. M53 is one of the more outlying globular clusters, being about

light-year A light-year, alternatively spelled light year (ly or lyr), is a unit of length used to express astronomical distances and is equal to exactly , which is approximately 9.46 trillion km or 5.88 trillion mi. As defined by the International Astr ...

s away from the

Galactic Center The Galactic Center is the barycenter of the Milky Way and a corresponding point on the rotational axis of the galaxy. Its central massive object is a supermassive black hole of about 4 million solar masses, which is called Sagittarius A*, a ...

, and almost the same distance (about ) from the

Solar System The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Sola ...

. The cluster has a core radius (''r_c'') of 2.18 pc, a half-light radius (''r_h'') of 5.84 pc, and a tidal radius (''r_tr'') of 239.9 pc. This is considered a

metal-poor In astronomy, metallicity is the abundance of elements present in an object that are heavier than hydrogen and helium. Most of the normal currently detectable (i.e. non-dark) matter in the universe is either hydrogen or helium, and astronomers ...

cluster and at one time was thought to be the most metal-poor cluster in the

Milky Way The Milky Way or Milky Way Galaxy is the galaxy that includes the Solar System, with the name describing the #Appearance, galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars in other arms of the galax ...

. Abundance measurements of cluster members on the

red giant branch The red-giant branch (RGB), sometimes called the first giant branch, is the portion of the giant branch before helium ignition occurs in the course of stellar evolution. It is a stage that follows the main sequence for low- to intermediate-mass st ...

show that most are first-generation stars. That is, they did not form from gas recycled from previous generations of stars in the cluster. This differs from the majority of globular clusters that are more dominated by second generation stars. The second generation stars in NGC 5024 tend to be more concentrated in the core region. Overall, the stellar composition of cluster members is similar to members of the Milky Way halo. The cluster displays various tidal-like features including clumps and ripples around the cluster, and tails along the cluster's orbit in an east–west direction. A tidal bridge-like structure appears to connect M53 with the close, very diffuse neighbor NGC 5053, as well as an envelope surrounding both clusters. These may indicate a dynamic tidal interaction has occurred between the two clusters; a possibly unique occurrence within the Milky Way since there are no known binary clusters within the galaxy. In addition, M53 is a candidate member of the Sagittarius dwarf galaxy tidal stream. Among the

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

population in the cluster, there are 55 known to be

RR Lyrae variable 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 a ...

s. Of these, a majority of 34 display behavior typical of the

Blazhko effect The Blazhko effect, also known as the Tseraskaya–Blazhko effect, and which is sometimes called long-period modulation, is a variation in period and amplitude in RR Lyrae type variable stars. Sergey Blazhko first reported its observation by Lid ...

, including 23 of type RRc – the largest known population of the latter in any globular cluster. There are also at least three variables of type SX Phe and a semi-regular red giant.

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Notes

References

External links

SEDS: Messier Object 53

Messier 53, Galactic Globular Clusters Database page
* {{DEFAULTSORT:Messier 53 Messier 053 Messier 053

053 53 may refer to: * 53 (number) * one of the years 53 BC, AD 53, 1953, 2053 * FiftyThree, an American privately held technology company that specializes in tools for mobile creation and visual thinking * 53rd Regiment Alabama Cavalry * 53rd Regiment ...

Messier 053 Astronomical objects discovered in 1775 Discoveries by Johann Elert Bode

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External links