M 106

Spiral Galaxy M106 (NGC 4258), type Sbp,

M109, while Tully lists it in the Coma-Sculptor

cloud. While M106 is usually classified as peculiar “normal” spiral of type Sb

(or Sbp), Tully classifies it as SABbc, i.e., intermediate between Sb and Sc,

and intermediate between normal and barred spirals.

As its equatorial plane is similarly inclined to the

line of sight, many features resemble what we know from the Andromeda

galaxy M31. As Alan Sandage mentions in the Hubble

Atlas of Galaxies, this orientation explains partly why the dust lanes are

so prominent in this galaxy. They form a spiral pattern which can be traced

well into its bright central region to the core. The spiral arms apparently

end in bright blue knots. These knots are most probably young star clusters

which are dominated by their very hot, brightest and most massive stars;

the occurance of these hot stars indictes that these clusters cannot be

very old, as such massive stars have only a short lifetime of a few million

years. So the blue knots show us the regions of very recent star formation!

Following the spiral arms in the sense of rotation, and most conspicuous on

the right of our image, is the yellowish remnant of an older spiral arm.

The color of this arm indicates that its more massive stars have ceased to

shine long ago, the color of the remaining ones sums up to the

yellow-greenish appearance. The age of the stellar population in this

fossil spiral arm is estimated by J.D. Wray to amount several hundred

million years.

Since the 1950s, M106 has been known to have a much larger extent in the

radio radiation than in visual light. In 1943, Carl K. Seyfert had listed

this galaxy among the galaxies with emission line spectra from their nuclei,

which are now called Seyfert galaxies, but modern studies of Seyfert galaxies

normally do not include it.

M106 is one of Mechain’s findings which were appended as

additional objects to Messier’s catalog.

it H V.43.

equipment gave evidence that M106 is possibly the home of a massive dark

objects, which could be traced to the lowest distance from the center ever

possible up to now: 36 million solar masses apparently reside within a

volume of about 1/24 to 1/12 light year radius (27,000 to 54,000 AU). This

was then the densest matter concentration ever detected.

The active center also emits jets, as was described by Brent Tully, Jon

Morse, and Patrick Shopbell in Sky & Telescope, Nov 1995 (p 20).

This makes it similar to the central “engines” in other active galaxies.

A supernova (1981K) occured im M106 in August 1981 and reached 16th

magnitude (Kenneth Glyn Jones’s book, in the table on page 32, misprints

“1931K”).