The Ursa Major Molecular Clouds

Extract

The Ursa Major molecular cloud complex lies in the direction of an expanding HI shell known as the North Celestial Pole loop. The NCP loop, which is centered at (l, b) ∼ (138°,30°) and easily seen in IRAS 100 μm emission, is some 60 pc across and 150 pc distant (Meyerdierks et. al 1991). At 100 μm, the Ursa Major clouds appear in projection as “finger” (l ∼ 140, b ∼ 38) which “hangs down” towards the center of the loop and the plane of the Galaxy. Distance estimates to the molecular clouds (Penprase 1993) are consistent with that of the NCP loop, indicating that the clouds are physically associated with the loop.