NGC 3621
Distance: 20.2 Million Light Years

Constellation: Hydra

text copyright Robert Gendler


NGC 3621, a member of the Leo spur of galaxies, is an isolated spiral, relatively neglected compared to other famous denizens of Hydra such as M83. In the late 1990's NGC 3621 was studied extensively by the Hubble Space Telescope as part of the project on the Extragalactic Distance Scale. NGC 3621 contributed 69 Cepheid Variable stars to the project establishing a distance of 20.2 million light years. The galaxy has rather loose spiral arms creating an overall large disk extending 93,000 light years across. It has a small bright bulgeless nucleus which was recently shown by the Chandra X-ray telescope to contain x-ray sources consistent with a supermassive black hole. Two x-ray sources each 20 arcsec from the center are thought to represent intermediate black hole systems each possessing a few thousand solar masses. The visible disk is elliptical. At radio wavelengths the HI disk has a radial extent of about 50 kpc, making NGC3621's HI disk one of the most extensive ever measured. Studies show abundant gas swept up in its spiral arms, particularly to the south and east.