In astronomy, an open cluster family is a group of approximately coeval (age range

\sim

Myr The abbreviation Myr, "million years", is a unit of a quantity of (i.e. ) years, or 31.556926 teraseconds. Usage Myr (million years) is in common use in fields such as Earth science and cosmology. Myr is also used with Mya (million years ago). ...

) young open star clusters located in a relatively small region of the

Galactic disk A galactic disc (or galactic disk) is a component of disc galaxies, such as spiral galaxies and lenticular galaxies. Galactic discs consist of a stellar component (composed of most of the galaxy's stars) and a gaseous component (mostly composed ...

(radius

\sim

250 pc).

Introduction

Open clusters do not form in isolation but in complexes (Efremov 1978), within star forming regions. When age, spatial distribution, and

kinematics Kinematics is a subfield of physics, developed in classical mechanics, that describes the Motion (physics), motion of points, Physical object, bodies (objects), and systems of bodies (groups of objects) without considering the forces that cause ...

are taken into account simultaneously, a significant number of known young open clusters are found in groups. Piskunov et al. (2006) found evidence for four open cluster complexes (OCCs) of different ages containing up to a few tens of clusters. The existence of at least five dynamical families of young open clusters in the Milky Way disk has been confirmed using statistical analysis by de la Fuente Marcos and de la Fuente Marcos (2008). They are, in order of increasing distance: Orion,

Scutum The ''scutum'' (; plural ''scuta'') was a type of shield used among Italic peoples in antiquity, most notably by the army of ancient Rome starting about the fourth century BC. The Romans adopted it when they switched from the military formati ...

- Sagittarius, Cygnus, Scorpius, and Cassiopeia-

Perseus In Greek mythology, Perseus (Help:IPA/English, /ˈpɜːrsiəs, -sjuːs/; Greek language, Greek: Περσεύς, Romanization of Greek, translit. Perseús) is the legendary founder of Mycenae and of the Perseid dynasty. He was, alongside Cadmus ...

. These families are associated to the Galactic spiral structure, they are short-lived as they disperse in a relatively short timescale and they are progenitors of classical superclusters, moving groups, and stellar streams (de la Fuente Marcos & de la Fuente Marcos 2008). The Cassiopeia-Perseus open cluster family is located 2 kpc from the Sun between the constellations of Cassiopeia and Perseus, embedded in the Perseus spiral arm (de la Fuente Marcos & de la Fuente Marcos 2009). The structure roughly defines a plane that is inclined almost 30° with respect to the plane of the Milky Way. It has a diameter of about 600 pc and includes 10 to 20 members. Most candidate members are located below the

and moving away from it. It started to form about 20 to 40 Myr (1 Myr = 10⁶ yr) ago.

References

* Efremov, Y. N. 1978, ''Soviet Astronomy Letters'', 4, 66-69
ADS entry
* de la Fuente Marcos, Raúl; & de la Fuente Marcos, Carlos (2008), ''Astrophysical Journal'', 672, 342-351
ADS entry
* de la Fuente Marcos, Raúl; & de la Fuente Marcos, Carlos (2009), ''New Astronomy'', 14, 180-195
ADS entry
* Piskunov, A. E., Kharchenko, N. V., Röser, S., Schilbach, E., & Scholz, R.-D. 2006, ''Astronomy and Astrophysics'', 445, 545-565
ADS entry
{{DEFAULTSORT:Open Cluster Family Star clusters Family

Introduction

See also

References