Page last updated Dec 28, 2021|
Added entry for PGC 52091
(= UGC 9391 = CGCG 296-013 = MCG +10-21-011)
A magnitude 14.4 spiral galaxy (type SBcd?) in Draco (RA 14 34 37.0, Dec +59 20 18)
Physical Information: Based on a recessional velocity relative to the Cosmic Microwave Background radiation of 1985 km/sec (and H0 = 70 km/sec/Mpc), PGC 52091 is about 90 to 95 million light-years away, in good agreement with redshift-independent distance estimates of about 40 to 140 million light-years (the HST press release uses a value of 130 million light-years). Given that and its apparent size of about 1.55 by 1.3 arcmin (from the images below), the galaxy is about 40 thousand light-years across if at the Hubble Flow distance, and about 55 to 60 thousand light-years across if at the HST press release distance. The galaxy is one of a number of relatively nearby galaxies in which HST studies are being used to calibrate the Cosmic Distance Scale by comparing brightnesses of Cepheid variables in our own galaxy to similar variables in the other galaxies, and supernova observations in those galaxies to similar supernovae in much more distant galaxies, whence the press release that led to this entry.
Above, a 12 arcmin wide SDSS image centered on PGC 52091
Below, a 1.8 arcmin wide SDSS image of the galaxy
Below, a 1.8 arcmin wide image of the galaxy (Image Credit ESA/Hubble & NASA, A. Riess et al.)
Below, a 1 arcmin wide image of the central portion of the galaxy (Image Credit as above)
A magnitude 15(?) spiral galaxy (type Sbc) in Virgo (RA 14 34 50.5, Dec +03 38 43)
Physical Information: Based on a recessional velocity of 8590 km/sec (and H0 = 70 km/sec/Mpc), a straightforward calculation indicates that PGC 52112 is about 400 million light years away. However, for objects at such distances we should take into account the expansion of the Universe during the time it took their light to reach us. Doing that shows that the galaxy was about 385 to 390 million light years away at the time the light by which we see it was emitted, about 390 to 395 million years ago (the difference between the two numbers being due to the expansion of the intervening space during the light-travel time). Given that and an apparent size for the main galaxy of about 0.35 by 0.3 arcmin, and for its fainter outer regions of about 0.5 by 0.4 arcmin (from the HST images below), the galaxy is about 40 thousand light years across, and its fainter outer regions span more than 55 thousand light years. PGC 52112 is a Seyfert galaxy (type Sy 1), and a strong X-ray emitter.
Above, a 12 arcmin wide SDSS image centered on PGC 52112
Below, a 0.6 arcmin wide SDSS image of the galaxy
Below, a 0.6 arcmin wide HST image of the galaxy (Image Credit ESA/Hubble & NASA)
Below, the above image enhanced to show fainter outer regions