Object of the Week - Jan 28th, 2018 - NGC 4395

Object of the Week - Jan 28th, 2018 - NGC 4395 = UGC 7524 = MCG 6-27-53 = PGC 40596 in Canes Venatici

R.A.: 12h25m49.0s Dec.: +33°32'49"
Apparent size of 13.2 by 11.0 arcmin
Magnitude: 10.80 B
Type; SABdm C (per Simbad)

NGC 4395 was discovered on Jan 2, 1786, by William Herschel and is the second largest galaxy in the CVn I galaxy group, with only NGC 4244 being larger. It is a tumultuous oddball galaxy, with several bright ionized hydrogen (HII) regions, three of which received their own NGC designations, those being NGC 4399, NGC 4400, and NGC 4401. Here is a labeled DSS pic…

Attachment 2872

NGC 4395 has a recessional velocity of only about 320 km/sec, which corresponds to a distance of about 15 million light years, fairly close as galaxies go, and this calculates to a diameter of about 55,000 light years, or about ½ the diameter of our own Milky Way Galaxy. NGC 4395 has a couple of very interesting features. While it is very unusual for a Magellanic spiral (Sm) to host an Active Galactic Nucleus (AGN), NGC 4395 holds the distinction of containing the faintest and nearest Seyfert nucleus currently known, as well as one of the intrinsically weakest nuclear x-ray sources observed to date (Ho & Ulvestad, 2001). Nearly all galaxies are known to contain a supermassive black hole in the center, and NGC 4395 has one of the smallest known such black holes, being six times smaller than the one at the center of our own Milky Way Galaxy.

Attachment 2873

Visually, NGC 4395 is a very low surface brightness spiral galaxy, and it takes a little work to fully appreciate it all. In my 25” dob, using a 106X eyepiece it took a while before I could hold the full extent of the galaxy with direct vision. Using higher power, the central core is still pretty dim, but is bigger and brighter than any of the HII knots, which are all faint and small, and barely detectable. Without a good reference photo I would have been lost.

As always, give it a go and let us know

Here is a sketch made with 12" (125-375x, SQM 21.6):

https://3.bp.blogspot.com/-cz_tmQbXE...1+NGC+4395.jpg

Hello All,

Here is my skectch with a 25" Obsession
http://www.deepsky-drawings.com/ngc-...635/dsdlang/en

Attachment 2876

Clear skies
Bertrand
http://www.deepsky-drawings.com/dsdlang/en/

Observation from 13 April 2013 in the southern Alps of France, elevation 1400 meters with good transparency and SQM 21.34. 12" SCT @ 179x/27':

The galaxy is an extremely faint, slightly NW to SE elongated glow, the HII regions are most obvious. Using AV the faint nucleus is visible.
On the NE edge is a mag. 14.5 star, to its SSW is a slightly east to west elongated, brighter area (NGC4401), resembles a faint elliptical galaxy.
With AV a very small, faint, round patch is visible to the SW of NGC4401, visible only with AV (NGC4400), on the threshold of visibility.
To the NW of the HII regions NGC4401 and NGC4400 is the brightest part of the galaxy.
The southwestern HII region NGC4399 is not visible.

Rated it 4/10.

I observed NGC 4395 in 2011 with my little 4" Newtonian (48x, 58' field of view). I expected this notoriously low surface brightness galaxy to be much more difficult. It was faint but definitely visible with a few uncertain details. Of course I didn't see the HII regions.

Attachment 2877
"Ny" stands for West.

Weird galaxy, I tried it to seperate the HII regions years ago with my former 16-inch under bad seeing but very good transparency.

16", 100x - 180x, seeing IV, NELM 7m0+
Attachment 2879

Viewed this last May in poor transparency 21.1 skies, without knowing what it was in advance. An example of how it pays to have done one's homework in advance, I would have spent more time to identify the HII regions. With a 20-inch:

"NGC 4395: Needed to switch to 121x for this one as it is large and spread out. Brighter almost stellar core area in middle of very faint, diffuse round glow uneven surface brightness. Probably a face-on spiral. Don't see any arms, just unevenness. [Turns out those uneven patches are distinct NGC designations, HII knots in the spiral]"