| NGC 685 | |
|---|---|
.jpg) NGC 685 imaged by theHubble Space Telescope | |
| Observation data (J2000epoch) | |
| Constellation | Eridanus |
| Right ascension | 01h 47m 42.8593s[1] |
| Declination | −52° 45′ 42.446″[1] |
| Redshift | 0.004546 ± 0.000010[1] |
| Heliocentric radial velocity | 1,363 ± 3 km/s[1] |
| Distance | 50–58Mly (15.2-17.8Mpc)[1] |
| Apparent magnitude (V) | 11.2[2] |
| Characteristics | |
| Type | SB(rs)d[1] |
| Size | ~74,300 ly (22.77 kpc) (estimated)[1] |
| Apparent size (V) | 3.7′ × 3.3′[1] |
| Other designations | |
| ESO 152- G 024, AM 0145-530A,IRAS 01458-5300,PGC 6581[1] | |
NGC 685 is abarred spiral galaxy in the constellationEridanus. The galaxy lies about 55 millionlight years away from Earth, which means, given its apparent dimensions, that NGC 685 is approximately 74,000 light years across.[1] It was discovered byJohn Herschel on October 3, 1834.[3]
This galaxy is seen nearly face-on, at an inclination of 23°.[4] It is a barred spiral galaxy with its bright center bar and patchy, curvingarms. The arms have low surface brightness and emerge from the bar and complete three quarters of a revolution before fading.[5] The patches of bright blue along the galaxy’s arms arestar clusters, groups of stars held together by their mutual gravitational attraction. Wisps of dark red near the central bar depict interstellar gas and dust, the matter from which stars form.[6] The southeast edge of the galaxy features three brightHII regions, whichHalton Arp argued they are a companion galaxy.H-alpha emission is stronger at the southeastern half of the galaxy.[7] The totalstar formation rate of the galaxy is estimated to be 0.42M☉ per year.[4]
The whole galaxy is about 74,000 light-years across – a little more than half the size of ourMilky Way.[6]In the centre of the galaxy is predicted to lie asupermassive black hole whose mass is estimated to be between 7.6 and 40 millionsolar masses, based on the spiral arm pitch angle.[8]
This article incorporates text from this source, which is in thepublic domain."Hubble Examines Entrancing Galaxy in Eridanus - NASA Science".NASA. 7 October 2023. Retrieved1 February 2025.
