De Vaucouleurs Atlas Type: SAB(rs)cd

Filter: B

Telescope: USNO 1.0-m
North up , East left
Field Dimensions: 23.2 x 21.4 arcminutes

RC3 Type: SAB(rs)cd
RSA Type: Sc(s)I
Surface Brightness Range Displayed: 18.5-26.0 mag per square arcsec
Absolute Blue Magnitude: -21.1
Elmegreen Spiral Arm Class: AC 9

De Vaucouleurs Atlas Description:

The bar of NGC 5457 (M101 ) is a very weak feature oriented east-west in the Atlas image; its weakness is the reason we have used the underline notation . At least one leading dust lane is visible in this feature, which is slightly more obvious in an I-band image (not shown). The inner pseudoring is fairly well-defined as a circular feature from which the two main inner arms wind. Although the ring is defined only by these two spiral arms, the arm structure gets more complex and more multi-armed at larger radii. In addition, the outer disk is very asymmetric. The B-I color index map reveals recent star formation in the center and a very complex dust distribution throughout the disk.

M101 has been the subject of many studies. These have shown that M101 is a very large spiral that is likely to be interacting with one or more of its smaller neighbors. Evidence for tidal interactions is provided by Waller et al. (1997).