The Hercules stream is a large
moving group
In astronomy, stellar kinematics is the observational study or measurement of the kinematics or motions of stars through space.
Stellar kinematics encompasses the measurement of stellar velocities in the Milky Way and its satellites as well a ...
of
stars that are trailing behind the local rate of galactic rotation and are heading further out in the
disk relative to the
galactic core
The Galactic Center or Galactic Centre is the rotational center, the barycenter, of the Milky Way galaxy. Its central massive object is a supermassive black hole of about 4 million solar masses, which is called Sagittarius A*, a compact rad ...
. Members of this stream may sometimes be referred to as Hercules stars. This stream was first hypothesized to be the remnants of a
cluster of
stars that has evaporated over time, becoming
gravitationally unbound. Alternatively, the Hercules stream may have been created as a resonant effect of the
galactic bar at 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. ...
. This stream
of stars has a
space velocity component ''V'' equal to about −40 km/s.
References
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Moving groups