M91
NGC 4548
Barred Spiral
Propriétés
Position et Identifiants
Visibilité
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À propos de M91
Description
M91 is a barred spiral galaxy in Coma Berenices, about 63 million light-years from Earth. It has a prominent central bar and well-defined spiral arms, making it one of the brighter barred spirals in the Virgo Cluster. The galaxy spans about 100,000 light-years. M91 was a 'lost' Messier object for nearly two centuries due to a position error.
Conseils d'Observation
Located about 1 degree south-southeast of M88 in the Virgo Cluster. In a telescope it appears as a moderately bright, oval glow with a bar-shaped central region visible in 8-inch or larger telescopes. The spiral arms are faint and require excellent conditions. It can be confused with nearby galaxies without careful chart comparison. Best observed from March through June.
Histoire
Cataloged by Charles Messier on March 18, 1781, but with incorrect coordinates that pointed to empty sky. M91 was 'lost' until William C. Williams identified it in 1969 as NGC 4548 by correcting Messier's position error. Some historians had previously speculated it was a comet or even a duplicate observation of M58.
Faits Amusants
M91 was the last 'lost' Messier object to be identified. Messier apparently made a reference frame error, recording the position relative to M89 instead of M58. When the correction is applied, the position matches NGC 4548 perfectly. M91 has the lowest surface brightness of any galaxy in the Messier catalog.
Photos de la Communauté (1)
Credit: NASA, ESA, and J. Lee (California Institute of Technology). License: CC BY-SA 4.0. (Wikimedia Commons)
Skybred Feb 28, 2026