Page last updated June 28, 2017|
A magnitude 14.5(?) irregular galaxy (type dIm?) in Sextans (RA 10 39 25.2, Dec +01 43 07)
Physical Information: Based on a recessional velocity of 705 km/sec (and H0 = 70 km/sec/Mpc), PGC 31693 is about 30 to 35 million light years away, in good agreement with a single redshift-independent distance estimate of 30 to 35 million light years. Given that and its apparent size of about 0.65 by 0.65 arcmin (from the images below), the galaxy is about 6 thousand light years across (hence its classification as a "dwarf" irregular), while its fainter outer regions span about 0.95 by 0.9 arcmin, or about 9 thousand light years. It is known as a starburst galaxy because it is undergoing a period of unusually intense star formation, resulting in a large number of hot bright young stars. It is also an "emission-line" galaxy, because those young stars are heating and lighting up surrounding clouds of gas and dust, causing them to fluorescence at wavelengths corresponding to their chemical composition.
Above, a 12 arcmin wide SDSS image centered on PGC 31693
Below, a 1.2 arcmin wide SDSS image of the galaxy
Below, a 1.2 arcmin wide HST image of the galaxy
(Image Credit ESA/Hubble & NASA; Acknowledgement Luca Limatola)