The spiral arms of M91 (NGC 4548) in Coma Berenices were photographed here, for the study of Cepheid variables in order to determine this Virgo Cluster galaxy's distance.

A considerable number of dark patterns, caused by interstellar dust in M91, can be traced along the spiral arms. Some blueish star clouds, containing blue and hot young massive stars, and small reddish diffuse nebulae, presumably H II regions in which star formation is under way, can be recognized. Of the individual bright stellar objects visible here, some may be Cepheid variables, others may be foreground stars, other bright giant stars in M91, or small star clusters.

There is a broken asteroid trail crossing the outer regions of this galaxy. Five trail segments (shown in white) were extracted from individual exposures and added to a cleaned color image of the galaxy. The asteroid enters the image at top center and moves down toward the lower left. Large gaps in the trail occur because the telescope is orbiting the Earth and cannot continuously observe the galaxy. This asteroid has a visual magnitude of 20.8, a diameter of one mile (1.6 kilometers), and was seen at a distance of 254 million miles from Earth and 292 million miles from the sun.
Credit: R. Evans and K. Stapelfeldt (Jet Propulsion Laboratory) and NASA

Original Press Release STScI PRC 98-10 on HST asteroid detection, photo 98-10d.

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Hartmut Frommert
Christine Kronberg
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Last Modification: November 15, 2001