dwarf irregular galaxy
kahkašân-e bisâmân-e kutulé
Fr.: galaxie irrégulière naine
An irregular galaxy that is much smaller than other irregulars. Dwarf irregulars are generally metal poor and have relatively high fractions of gas. They are thought to be similar to the earliest galaxies that populated the Universe, and are therefore important to understand the overall evolution of galaxies.
1) bisâmân (#); 2) nârazan-mand
From O.Fr. irregulier, from M.L. irregularis, from → in- "not" + L. regularis from regula "rule," from PIE *reg- "move in a straight line," hence, "to direct, rule" (cf. Pers. râst "right, straight;" O.Pers. rāsta- "straight, true," rās- "to be right, straight, true;" Av. rāz- "to direct, put in line, set," razan- "order;" Skt. raj- "to direct, stretch," rjuyant- "walking straight;" Gk. orektos "stretched out;" L. regere "to lead straight, guide, rule," p.p. rectus "right, straight;" Ger. recht; E. right).
Bisâmân, from bi- "not, without" + sâmân "order, arrangement, disposition; boundary, limit," Lârestâni sâmon "sign or mark separating one field from another," Gilaki, Tabari šalmân "a straight peace of wood or beam, post;" Mid.Pers. sâmânak, sahmân "limit;" loaned into Arm. sahmân; cf. Skt. sīmān-, sīmā- "boundary, border, limit."
Fr.: galaxie irrégulière
A galaxy with no spiral structure and no symmetric shape. Irregular galaxies are usually filamentary or very clumpy in shape and tend to smaller than others. Two types of irregular galaxies are defined, → Irr I galaxy and → Irr II galaxy.
bandevâr-e bisâmân, mâh-e ~
Fr.: satellite irrégulier
A satellite whose orbit around its planet is eccentric, inclined with respect to the equatorial plane, and relatively far from the planet. Strong solar perturbations cause the orbit to precess. → regular satellite.
Fr.: variable irrégulière
A type of variable star in which variations in brightness show no regular periodicity. There are two main types, irregular eruptive variables and irregular pulsating variables.
Sagittarius Dwarf Irregular Galaxy
kahkešân-e kutule-ye bisâmân-e Nimasb
Fr.: galaxie naine irrégulière du Sagittaire
A dwarf irregular galaxy, discovered in 1977, that is a member of the Local Group of galaxies. It has a diameter of 1,500 light-years and lies about 3.5 million light-years away. SagDIG contains as much as about 108 solar masses of H I gas and is one of the most metal-poor galaxies. It should not be confused with the → Sagittarius Dwarf Elliptical Galaxy.