  We report the discovery of a confirmed supernova (SN) and a
supernova-candidate in near-infrared images from the ALTAIR/NIRI adaptive
optics system on the Gemini-North Telescope and NICMOS on the Hubble Space
Telescope. The Gemini images were obtained as part of a near-infrared K-band
search for highly-obscured SNe in the nuclear regions of luminous infrared
galaxies. SN 2008cs apparent in the Gemini images is the first SN discovered
using laser guide star adaptive optics. It is located at 1500 pc projected
distance from the nucleus of the luminous infrared galaxy IRAS 17138-1017. The
SN luminosity, JHK colors and light curve are consistent with a core-collapse
event suffering from a very high host galaxy extinction of 15.7 +- 0.8
magnitudes in V-band which is to our knowledge the highest yet measured for a
SN. The core-collapse nature of SN 2008cs is confirmed by its radio detection
at 22.4 GHz using our Very Large Array observations 28 days after the SN
discovery, indicating a prominent interaction of the SN ejecta with the
circumstellar medium. An unconfirmed SN apparent in the NICMOS images from 2004
is located in the same galaxy at 660 pc projected distance from the nucleus and
has a lower extinction.
