NGC 1637
Galaxy in the constellation Eridanus
From Wikipedia, the free encyclopedia
NGC 1637 is an isolated, non-interacting[7] intermediate spiral galaxy in the constellation Eridanus, about a degree to the WNW of the star Mu Eridani.[8] It was discovered by German-British astronomer William Herschel on 1 February 1786.[9][10] It is located at a distance of about 9.77 ± 1.82 Mpc (31.9 ± 5.9 Mly) from the Milky Way.[3] The galaxy is inclined at an angle of 31.1° to the line of sight from the Earth and the long axis is oriented along a position angle of 16.3°.[3]
| NGC 1637 | |
|---|---|
NGC 1637 imaged by the Very Large Telescope | |
| Observation data (J2000 epoch) | |
| Constellation | Eridanus |
| Right ascension | 04h 41m 28.229s[1] |
| Declination | −02° 51′ 28.94″[1] |
| Redshift | 0.00239[2] |
| Heliocentric radial velocity | 717.1±1.2 km/s[2] |
| Distance | 9.77 ± 1.82 Mpc (31.9 ± 5.9 Mly)[3] 9.18 Mpc (29.9 Mly) h−1 0.73[4] |
| Apparent magnitude (V) | 11.5[5] |
| Apparent magnitude (B) | 11.25[6] |
| Characteristics | |
| Type | SAB(rs)c[3] or SBc(s)II.3[7] |
| Size | ~57,000 ly (17.48 kpc) (estimated)[5] |
| Apparent size (V) | 4.0′ × 3.2′[5] |
| Other designations | |
| AGC 440323, IRAS 04389-0257, UGCA 93, MCG +00-12-068, PGC 15821, CGCG 393-066[5] | |
In 1991, Gérard de Vaucouleurs and associates assigned a morphological classification of SAB(rs)c to NGC 1637, indicating a spiral galaxy with a weak bar structure (SAB) across the nucleus, surrounded by a partial ring (rs) and somewhat loosely-wound arms (c).[7] While the inner section of the galaxy shows a symmetrical two-arm structure,[6] it has a single outer spiral arm that wraps 180° around the nucleus,[6] giving the galaxy an overall asymmetric, lopsided appearance.[7] The outer spiral arm has a red component that indicates a significant age.[6] However, the existence of this structure is difficult to explain.[7] The galaxy shows indications of recent starburst activity that may have terminated around 15 million years ago.[6]
The active central nucleus shows weak LINER behavior, and it may be an intermediate form between a LINER and an H II region.[7] The luminosity of the X-ray source at the nucleus is 1.2×1038 ergs s−1 in the 0.3–7 keV band.[6]
Supernovae
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Two supernovae have been observed in NGC 1637:
- SN 1999em (Type II-P, mag. 13.5) was discovered by the Lick Observatory Supernova Search (LOSS) on 29 October 1999, at an angular separation of 24″ to the southwest of the galaxy center.[11][12] It was the brightest supernova discovered that year, reaching magnitude 13.1.[13] The location corresponds to a deprojected galactocentric separation of 1.3 kpc (4.2 kly).[3]
- SN 2025pht (Type II-P, mag. 13.3) was discovered by All Sky Automated Survey for SuperNovae on 29 June 2025.[14] A study of archival images taken with the Hubble Space Telescope and the James Webb Space Telescope found a suspected progenitor, a red supergiant star with a mass of ~15M☉.[15]
Image and Video Gallery
NGC 1637 imaged by the Hubble Space Telescope- Video showing the location of NGC 1637
