NGC 2685 — S0-a in Ursa Major
S0-a in Ursa Major, 4.3 arcminutes across, its light 42 million years old. Measured by HyperLEDA, photographed by Pan-STARRS1. Recorded once.
About NGC 2685
NGC 2685 is a polar ring galaxy, sometimes called the Helix Galaxy. Rings of gas and dust wrap around it at a steep angle to its main body, the remains of material it captured from another galaxy.
What you are looking at
NGC 2685 is a lenticular galaxy: a disc galaxy that has largely used up the gas it needs to form new stars, so its disc is smooth and has no spiral arms. Its disc is steeply tilted, about 68° from face-on, so it appears as a long oval. From edge to edge its visible disc spans about 53,000 light-years (taking its redshift distance, which for a galaxy this near is approximate), about half the width of the Milky Way.
What astronomers have recorded
SIMBAD, the reference database astronomers use, classes it as a Seyfert galaxy: its nucleus is lit by gas falling into its central black hole, though dust hides part of that glow from us. Halton Arp included it in his 1966 Atlas of Peculiar Galaxies as Arp 336, a list of galaxies with unusual, disturbed shapes. It is cited in 461 scientific papers indexed by SIMBAD, and recorded there under 27 different catalogue designations.
When this light set out
The light that reaches us from NGC 2685 today set out about 42 million years ago, when the planet had come through its hottest interval since the dinosaurs. The galaxy is moving away from us at about 877 km/s (2.0 million mph), carried by the expansion of the universe. For a galaxy this close, its own motion through space is a large share of that speed, so the distance worked out from it is approximate; distances measured from individual stars in it can differ.
Finding it in the sky
In the sky, NGC 2685 sits within the constellation Ursa Major. From most of the United States it never sets: it circles the north celestial pole all year, and stands highest on spring evenings, around March.
Its neighbours
At almost the same distance from us, and so its neighbours in space as well as on the sky: UGC 4683 (0.5° away on the sky, at least 340,000 light-years from it).
By apparent size it is number 182 of the 12,657 galaxies on the Galaxy Origins register.
Measurements
| Catalogue | PGC 25065 |
|---|---|
| Morphological type | S0-a |
| Angular diameter | 4.33′ |
| Right ascension | 08h55m34.7s |
| Declination | +58°44′03.8″ |
| Constellation | Ursa Major |
| Inclination | 68.4° |
| Light travel time | 42 million years |
| Bar | yes, from the catalogue |
Check every figure above in the NASA/IPAC Extragalactic Database
What is sold
A print of this galaxy and the record of the calculation, once. When it sells it leaves the register and is not offered again. We assign no names and no ownership — nobody can sell you those.
At 4.3 arcminutes this is a Exceptional galaxy, which is the tier where a real photograph shows clear structure and dust lanes. The tier comes from the measured diameter, not from a price list.
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