Herschel 171 and Messier 106

Date: 6 March 2025

Altitude: 61 - 71 degrees

Pixel scale: 0.86" per pixel

Total exposure time: 100 minutes

B filter: 60 x 44 seconds

V filter: 52 x 36 seconds

R filter: 50 x 30 seconds

Herschel 171 is also known as Messier 106 and NGC 4258.

Galaxy: Classification SAB(s)bc Sy1.9

Constellation: Canes Venatici

Diameter: ~60,000 light years

Notes

The galaxy was discovered by Pierre Méchain in 1781. It contains an active nucleus classified

as a Type 2 Seyfert, and the presence of a central supermassive black hole has been demon-

strated from radio-wavelength observations of the rotation of a disk of molecular gas orbiting

within the inner light-year around the black hole. Besides the two visible arms, it has two "an-

omalous arms" detectable using an X-ray telescope.