NGC 4550 — S0 in Virgo
S0 in Virgo, 3.2 arcminutes across, its light 20 million years old. Measured by HyperLEDA, photographed by Pan-STARRS1. Recorded once.
About NGC 4550
NGC 4550 is a rare galaxy made of two discs of stars rotating in opposite directions, one inside the other, probably the result of a past merger.
What you are looking at
NGC 4550 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 turned almost exactly side-on to us: the galaxy appears as a narrow blade of light, and its dust as a dark seam running along it. From edge to edge its visible disc spans about 18,000 light-years (taking its redshift distance, which for a galaxy this near is approximate), about a fifth the width of the Milky Way.
What astronomers have recorded
SIMBAD, the reference database astronomers use, classes it as one of a pair of galaxies. It is cited in 563 scientific papers indexed by SIMBAD, and recorded there under 22 different catalogue designations.
When this light set out
The light that reaches us from NGC 4550 today set out about 20 million years ago, when grasslands were spreading across the continents. The galaxy is moving away from us at about 410 km/s (0.9 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 4550 sits within the constellation Virgo. It is best placed on spring evenings: around 9:30 pm in May it stands about 62° 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: IC 3459 (0.9° away on the sky, at least 300,000 light-years from it); NGC 4491 (1.3° away on the sky, at least 460,000 light-years from it); NGC 4506 (1.4° away on the sky, at least 500,000 light-years from it); IC 3393 (1.8° away on the sky, at least 620,000 light-years from it), and 7 more.
By apparent size it is number 462 of the 12,657 galaxies on the Galaxy Origins register.
Measurements
| Catalogue | PGC 41943 |
|---|---|
| Morphological type | S0 |
| Angular diameter | 3.15′ |
| Right ascension | 12h35m30.6s |
| Declination | +12°13′15.2″ |
| Constellation | Virgo |
| Inclination | 90.0° |
| Light travel time | 20 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 3.2 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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