M91 (NGC 4548) — Sb in Coma Berenices
Sb in Coma Berenices, 5.5 arcminutes across, its light 23 million years old. Measured by HyperLEDA, photographed by Pan-STARRS1. Recorded once.
About M91 (NGC 4548)
Messier 91 was for a long time one of the 'missing' objects in Messier's catalogue, because of an error in the position he recorded. It is now identified as NGC 4548, a barred spiral in the Virgo Cluster with a clear bar and a ring of arms around it.
What you are looking at
M91 is a spiral with a sizeable central bulge and well-defined arms, close in type to the Milky Way. It is tilted about 37° to our line of sight, enough to show both the shape of its arms and the depth of its disc. From edge to edge its visible disc spans about 37,000 light-years (taking its redshift distance, which for a galaxy this near is approximate), about a third the width of the Milky Way.
What astronomers have recorded
SIMBAD, the reference database astronomers use, classes it as a LINER galaxy: its nucleus shows the faint, low-level activity of a black hole feeding slowly. It is cited in 648 scientific papers indexed by SIMBAD, and recorded there under 29 different catalogue designations.
When this light set out
The light that reaches us from M91 today set out about 23 million years ago, when Antarctica had begun to freeze. The galaxy is moving away from us at about 481 km/s (1.1 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
M91 lies in Coma Berenices. It is best placed on spring evenings: around 9:30 pm in May it stands about 64° high in the south, seen from the middle of the United States.
Its neighbours
It lies in the direction of the Virgo Cluster and at a matching speed, which places it among the cluster’s more than a thousand galaxies, the nearest large cluster to the Milky Way. At almost the same distance from us, and so its neighbours in space as well as on the sky: NGC 4571 (0.5° away on the sky, at least 180,000 light-years from it); IC 3522 (0.7° away on the sky, at least 300,000 light-years from it); NGC 4523 (0.8° away on the sky, at least 320,000 light-years from it); NGC 4595 (1.3° away on the sky, at least 540,000 light-years from it), and 9 more.
By apparent size it is number 95 of the 12,657 galaxies on the Galaxy Origins register.
Measurements
| Catalogue | PGC 41934 |
|---|---|
| Morphological type | Sb |
| Angular diameter | 5.55′ |
| Right ascension | 12h35m26.5s |
| Declination | +14°29′45.9″ |
| Constellation | Coma Berenices |
| Inclination | 36.9° |
| Light travel time | 23 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 5.5 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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