An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

In a theoretical → Hertzsprung-Russell diagram, the path taken by an evolving star.

→ evolutionary; → track.

The path on the → Hertzsprung-Russell diagram that is followed by a fully → convective  → pre-main sequence star to reach the → zero-age main sequence. Hayashi tracks for → low-mass stars are near vertical. At higher masses, stars become increasingly radiative as they contract and the Hayashi tracks are almost horizontal.

Named after the Japanese astrophysicist Chushiro Hayashi (1920-2010), who published his paper in 1961 (PASJ 13, 450); → track.

A nearly horizontal path on the → Hertzsprung-Russell diagram that a → pre-main sequence star of small mass follows in an early stage of evolution after leaving the → Hayashi track and before reaching the → main sequence. During this stage the pre-main sequence star remains almost wholly in radiative equilibrium.

After Louis George Henyey (1910-1970), American astronomer. Henyey et al. (1955, PASP 67, 154).

1a) Evidence, as a mark or a series of marks, that something has passed.
1b) A path made or beaten by or as if by the feet of people or animals; trail (Dictionary.com).
1c) A line of motion, a course followed, such as → Hayashi track. See also: → evolutionary track, → Henyey track, → white dwarf cooling track, → tracking, → tracking accuracy.
2) To follow or pursue the track, traces, or footprints of.

M.E. trak, from M.Fr. trac, from O.Fr. trac "track of horses, trace" (mid-15c.), possibly from a Germanic source (compare M.L.G. treck, Du. trek "drawing, pulling).

Tor, from Lori, Laki, Fini, Bandar-Abâsi tor "track, trace, mark;" maybe ultimately from Proto-Ir. *tar- "to cross over;" cf. Av. tar- "to cross over;" Mid.Pers. (+*ui-) widur-, widôr- "to pass (beyond, over); Pers. gozar; Baluci tar(r)- "to walk;" Yaghnobi tir-, ter- "to go, leave;" → trans-.
Tor gereftan, with gereftan "to take, seize" (Mid.Pers. griftan, Av./O.Pers. grab- "to take, seize," cf. Skt. grah-, grabh- "to seize, take," graha "seizing, holding, perceiving," M.L.G. grabben "to grab," from P.Gmc. *grab, E. grab "to take or grasp suddenly;" PIE base *ghrebh- "to seize").

The facility that allows a telescope to follow a celestial object during in its westward motion in the sky.

Verbal noun from → track.

The accuracy with which a → telescope tracks a target.

→ tracking; → accuracy

In the → Hertzsprung-Russell diagram, the evolutionary track followed by a → low-mass or an → intermediate-mass star when it can no longer produce thermonuclear energy. The track starts at the end of the → horizontal branch to lead the star to a → white dwarf phase.

→ white; → dwarf; → cooling; → track.