An Etymological Dictionary of Astronomy and Astrophysics
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A systematic trend in the motion of some → Galactic halo→ old stars thought to be a relic of the → merging of a dwarf satellite galaxy devoured by our Milky Way. Using kinematic data from the → Hipparcos satellite, Helmi et al. (1999, Nature 402, 53) found two halo star streams which share a common progenitor: a single coherent object disrupted during or soon after the Milky Way's formation, and which probably resembled the Fornax and Sagittarius dwarf spheroidal galaxies.

See also Helmi & White 1999, MNRAS 307, 495; → stream.

A service in an organization or computer system where users are directed for technical support or assistance.

M.E., O.E. help (m.), helpe (f.) "assistance, succor," helpan "o help" (cf. O.N. hjialp, hjalpa, M.Du., Du. hulp, helpen, O.H.G. helfa, helfan, Ger. Hilfe, helfen); PIE base *kelb- "to help" (cf. Lith. selpiu "to support, help"); desk, from M.E. deske; M.L. desca, descus "table to write on," from L. discus "quoit, platter, dish," from Gk. diskos "disk, dish."

Yâigâh, from yâri "help, assistance," → gravity assist, + -gâh "place; time," → station.

A mineral that is often found in meteorites. It is an oxide of iron (Fe₂O₃) that is similar to magnetite. It does not attract a magnet. When it is rubbed against an object harder than itself, it leaves a reddish-brown stain. Hematite is also sometimes called bloodstone.

From M.Fr. hematite, from L. hæmatites, from Gk. haimatites lithos "bloodlike stone," from haima (genitive haimatos) "blood" + -ites, → -ite, + lithos "stone."

A defect of the eyes in which sight is normal in the night or in a dim light but is abnormally poor or wholly absent in the day or in a bright light. Also called day blindness. Opposite of → nyctalopia

From N.L., from Gk hemeralop- (stem of hemeralops having such a condition, from hemer(a) "day" + al(aos) "blind" + -ops having such an appearance) + -ia a noun suffix.

Ruzkuri, from ruz, → day, + kuri "blindness," from kur, → blind.

Half of a sphere bounded by a great circle, especially one of the halves into which the earth or the celestial sphere is divided.

From L. hemisphærium, from Gk. hemisphairion, from hemi- "half," (from PIE base *semi-; cf. Skt. sami, L. semi-, O.H.G. sami- "half," and O.E. sam-) + sphaira, → sphere.

From nim-, → half + sepehr, koré, → sphere.

A catalog of stars in which every star is classified by its stellar spectrum. This system is named for the astronomer Henry Draper, but was cataloged by Annie J. Cannon (225,300 stars), and later extended by Margaret W. Mayall.

Henry Draper (1837-1882), an American pioneer of astronomical spectroscopy who established the observing techniques and program for the work that would bear his name when published, seven years after his early death; → system.

A powerful numerical technique to solve the stellar structure equations where the star is sub-divided in a finite number of grid cells for which the local conditions are evaluated and computed from the surface inwards to the center by utilizing a Newton-Raphson solver. Relevant physical quantities are either defined at the cell boundaries or as mean values over the complete cell.

Henyey, L. G.; Forbes, J. E.; Gould, N. L., 1964, ApJ 139, 306; → method.

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).

A combining form meaning "seven."

From Gk. hepta "seven;" cognate with L. septem; Pers. haft, as below; Du. zeven, O.H.G. sibun, Ger. sieben, E. seven.

Haft-, from haft "seven;" Mid.Pers. haft; Av. hapta; cf. Skt. sapta; Gk. hepta, L. septem; PIE *septm.

A → polygon with seven → angles and seven → sides.

→ hepta-; → -gon.

A young → A-type or → B-type star showing → emission lines in its spectrum. Herbig AeBe stars are → pre-main sequence stars of → intermediate mass (→ intermediate-mass star). They are often called the higher mass counterparts of → T Tauri stars.

Named after George H. Herbig (1920-2013), who first classified them (Herbig 1960, ApJS 4, 337); → A star; → B star; e indicating → emission.

A small patch of → nebulosity in a → star-forming region, created when fast-moving → jets of material (with speeds up to about 1000 km per sec) from a newborn star collide with the → interstellar medium.

→ Herbig AeBe star; Guillermo Haro (1913-1988), who first in 1940s studied these objects in detail and recognized that they were a by-product of the star formation process; → object.

An ancient → constellation (right ascension about 17h, declination 30° north), one of the largest in the sky, which is located between → Lyra and → Corona Borealis. It is traditionally depicted as the hero Hercules in a kneeling position. There are no very bright stars in Hercules, the brightest one is → Rasalgethi, a variable → red supergiant of magnitude about 3.5. Abbreviation: Her; Genitive: Herculis.
See also: → Hercules cluster.

L. Hercules, from Gk. Heracles "glory of Hera," the most popular hero of Gk. mythology, son of Zeus and the woman Alcmena, who the god seduced in the shape of her husband Amphitryon, king of Thebes.

Herâkles, as above; Herkul, from Fr. Hercule, as above; Arabicized name of the constellation: هرقل. Other Ar. renderings: (al-jâthi, jâthi 'alâ rukbataihi (الجاثی، الجاثی علی‌رکبتیه) "the kneeling one," râqes (راقص) "the dancing one."
Bar zânu nešasté "the kneeling one," Pers. descriptive rendering of the Gk. mythological figure, by the famous 11-th century astronomer Biruni.

A small, irregular → cluster of galaxies with fewer than 100 galaxies in its core. It has no strongly dominant central galaxy and is notable for the high proportion of spirals. It lies some 500 million → light-years away in the constellation → Hercules; also known as Abell 2151.

→ Hercules; → cluster.

→ inheritable.

→ inherit; → -able.

1) Passing, or capable of passing, naturally from parent to offspring through the genes: Blue eyes are hereditary in our family.
2) Of or relating to inheritance or heredity (Dictionary.com).

Of or relating to → heredity.

The passing on of physical or mental characteristics genetically from one generation to another (OxfordDictionaries.com).

M.E., from M.Fr. hérédité, from O.Fr. eredite "inheritance, legacy," from L. hereditatem (nominative hereditas) "heirship, inheritance," → heritage.

Rigandâšt, literally "possessing heritage," from rigan, → heritage, + dâšt past stem of dâštan "to have, hold, possess, maintain," → property.

→ inheritable.

→ inherit; → -able.

1) Something inherited at birth, such as personal characteristics, status, and possessions.
2) Anything that has been transmitted from the past or handed down by tradition (Dictionary.com).

M.E. from M.Fr., from O.Fr. iritage, eritage, heritage "heir; inheritance, ancestral estate, heirloom," from heriter "inherit," from L.L. hereditare, ultimately from L. heres (genitive heredis) "heir, heiress," from PIE root *ghe- "to be empty, left behind" (related Gk. word khera "widow").

Rigan from rig "left, abandoned" (in mordé rig "heritage, effects of a dead person, anything hereditary, heirloom") + noun suffix -an (as in rowzan, rowšan, suzan, rasan, zaqan, hâvan, etc.); ultimately from Proto-Ir. *raic- "to leave, abandon;" cf. Av. raēc- "to leave, let;" Mid.Pers. (+ *pati-) phryz-, Mod.Pers. parhêz, parhiz "to keep away from, abstain, avoid;" Khotanese (+ *fra-) hars- "to be left, remain;" Mod.Pers. rištan "to set at liberty, absolve;" Mid.Pers. (+ *ui-) wirēz-, Mod.Pers. gurēz, goriz, gurēxtan, gorixtan "to flee, run away;" Gk. leipein "to leave;" L. linquere "to leave;" PIE *leik^w- "to leave, let" (Cheung 2006).

Biology: An individual, animal, or plant possessing both male and female reproductive organs.

From L. hermaphroditus, from Gk. hermaphroditos the mythical son of Hermes and Aphrodite who merged bodies with a naiad and thereafter possessed both male and female qualities.

Narmâde, literally "male-female," → male, → female.