M106 and friends...

M106 and adjacent galaxies

Object: Messier 106 (NGC 4258)
Type: Spiral Galaxy (morphological classification SABbc)
Constellation: Canes Venatici
Distance: 24 million light years

Date: April 22nd 2020
Equipment: ATIK 460EX with EFW2, Skywatcher f5.5 Esprit 100 ED refractor, Avalon Linear mount, guiding with Lodestar X2/PHD

Subframes: 12 x 600s luminance, 12 x 300s (2x2 binned) each for RGB, flats for each channel, bias as darks (hot pixel removal in Astroart).

High overhead in on April evenings, the galactic north pole looks out beyond the arms of our own Milky Way galaxy and into the chilling depths of intergalactic space. 

Stellarium map showing location of image field

Mid-way between Beta Canum Venaticorum (a 4^th magnitude star called Chara, second brightest star in the rather obscure constellation of Canes Venatici – the Hunting Dogs – which is tucked beneath the handle of the Plough) and gamma Ursae Majoris (Phecda, also called Phad, the left-hand star in the bowl of the Plough), lies the distant spiral galaxy Messier 106.

It was discovered by the French astronomer Pierre Méchain in July of 1781. Méchain mentioned the discovery in a letter to fellow astronomer Johann Bernoulli dated May 6, 1783:

The galaxy, however, was not included in the Messier Catalogue until 1947, when Canadian astronomer Helen Sawyer Hogg added it (along with galaxies M105 and M107) based on Méchain’s letter.

William Herschel independently discovered M106 on March 9, 1788

M106 - crop from above image

Located a little over 20 million light-years away, practically a neighbour by cosmic standards, Messier 106 is one of the brightest and nearest spiral galaxies to our own. NGC 4248, a small galaxy which can be seen next to M106 in the cropped image opposite and which lies at a similar distance, is thought to be a satellite of M106.

M106 occupies an area of 18.6 by 7.2 arc minutes of apparent sky, corresponding to a spatial diameter of 135,000 light years. It has a high surface brightness (an apparent magnitude of 9.1) and can be glimpsed in binoculars, which reveal a faint patch of light.

  

Messier 106 is classified as a SABbc type galaxy, which means that it is an intermediate between a normal and barred spiral galaxy. It is home to at least 400 billion stars, being similar in size and luminosity to the Andromeda Galaxy (M31) and making it one of the brightest, largest nearby galaxies.

It is also classified as a Seyfert II galaxy, having an active nucleus. It has a considerably larger extent in radio than in visible light and exhibits emission line spectra from the nucleus. M106 shows unusual emission lines and X-rays, indicating that a portion of the galaxy is falling into an active central super-massive black hole.

Luminance frame, showing galaxies in the field of M106

Several other NGC galaxies occupy the same field of view shown in the main image. The edge-on spiral NGC 4217 is thought to be approximately 60 million light years away, whilst the galaxy pair NGC 4231 and 4232 are thought to be 350 million light years away. Other un-named tiny galaxies, rendered as mere smudges of light by their unimaginable distances, can be seen scattered across the luminance frame shown opposite. Even given the vast distance of M106, it is a mere foreground object compared to the remoteness offered up by intergalactic space.

The evening of April 22^nd was very clear, but the seeing was initially somewhat shaky. I therefore set out to gather blue binned data, but the seeing improved and as the guiding accuracy dropped to 0.6” RMS, I switched to collecting full frame luminance, finishing off with some red and green binned data before the sky began to brighten. The green frames were plagued by a bit of a gradient, partly because a haze had set in, and partly because the dawn light was making itself apparent

The final luminance image was a bit noisy, and probably requires more than the 2 hours of data that I collected. 

One bonus of seeing the dawn come in was the sight of Jupiter and Saturn, a mere 5 degrees apart, rising above my south-eastern horizon.