NGC 2841

NGC 2841
A Hubble Space Telescope image of NGC 2841
Observation data (J2000 epoch)
Constellation	Ursa Major
Right ascension	09h 22m 02.655s[1]
Declination	+50° 58′ 35.32″[1]
Redshift	0.002130[2]
Heliocentric radial velocity	638 km/s[3]
Distance	46.0 ± 4.9 Mly (14.1 ± 1.5 Mpc)[4][5]
Apparent magnitude (V)	10.1[3]
Characteristics
Type	SAa[2]
Mass	7×1010 M☉[6] M☉
Apparent size (V)	8.1′ × 3.5′[6]
Notable features	Flocculent galaxy with LINER nucleus
Other designations
UGC 4966, PGC 26512[3]

NGC 2841 is an unbarred spiral galaxy in the northern circumpolar constellation of Ursa Major. It was discovered on 9 March, 1788 by German-born astronomer William Herschel. J. L. E. Dreyer, the author of the New General Catalogue, described it as, "very bright, large, very much extended 151°, very suddenly much brighter middle equal to 10th magnitude star".^[7] Initially thought to be about 30 million light-years distant, a 2001 Hubble Space Telescope survey of the galaxy's Cepheid variables determined its distance to be approximately 14.1 megaparsecs or 46 million light-years.^[4] The optical size of the galaxy is 8.1′ × 3.5′.^[6]

This is the prototype for the flocculent spiral galaxy,^[5] a type of spiral galaxy whose arms are patchy and discontinuous.^[8] The morphological class is SAa, indicating a spiral galaxy with no central bar and very tightly-wound arms. There is no grand design structure visible in the optical band, although some inner spiral arms can be seen in the near infrared.^[5] It is inclined by an angle of 68° to the line of sight from the Earth, with the major axis aligned along a position angle of 148°.^[5]

The properties of NGC 2841 are similar to those of the Andromeda Galaxy.^[4] It is home to a large population of young blue stars, and a few H II regions.^[9] The luminosity of the galaxy is 2×10¹⁰ L_☉ and it has a combined mass of 7×10¹⁰ M_☉.^[6] Its disk of stars can be traced out to a radius of around 228 kly (70 kpc). This disk begins to warp at a radius of around 98 kly (30 kpc), suggesting the perturbing effect of in-falling matter from the surrounding medium.^[5]

The rotational behavior of the galaxy suggests there is a massive nuclear bulge,^[6] with a low-ionization nuclear emission-line region (LINER) at the core; a type of region that is characterized by spectral line emission from weakly ionized atoms.^[10] A prominent molecular ring is orbiting at a radius of 7–20 kly (2–6 kpc), which is providing a star-forming region of gas and dust.^[6] The nucleus appears decoupled and there is a counter-rotating element of stars and gas in the outer parts of the nucleus, suggesting a recent interaction with a smaller galaxy.^[6]

Four supernovae have been observed in NGC 2841: SN 1912A (type Ia, mag. 13),^[11] SN 1957A (type Ia, mag. 14),^[12] SN 1972R (mag. 16),^[13] and SN 1999by (type Ia, mag. 15).^[14]

References

External links

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