The HST images have allowed researchers to view in unprecedented detail the spiral arms and dust clouds of M51, which are the birth sites of massive and luminous stars. This Hst image, a composite of several observations, shows starlight as well as light from glowing hydrogen, which is associated with the brightest young stars in the spiral arms. Dust 'spurs' M51, also known as NGC 5194, is having a close encounter with a nearby companion galaxy, NGC 5195, just off the edge of the latest HST image. The companion's gravitational pull is causing turbulence in M51's gas and dust clouds triggering star formation in them, as can be seen by the many luminous clusters of bright, young, energetic stars. These bright clusters are highlighted in red by the light from associated glowing hydrogen gas.
Astronomers can see for the first time intricate structure in the dust clouds.
The regularity and large number of these features suggests to astronomers that discarded ideas about spiral galaxies may have some merit after all. The new images also reveal a dust disc in the very core of the galaxy. This dust, astronomers speculate, may provide fuel for a central black hole. Several groups of astronomers are also studying M51 at infrared wavelengths which can be observed by Hubble using special detectors. At these wavelengths, the dusty clouds are more transparent and the true distribution of stars in the galaxy is seen more easily.