Gavin James
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M106 is an intermediate spiral galaxy located in the constellation Canes Venatici. It has a spiral diameter of 135,000 light years and is similar in size to the Andromeda Galaxy (M31). It has a high surface brightness so can be seen with binoculars as a faint patch of light.

It was discovered by the French astronomer Pierre Méchain in July 1781. Méchain discovered many of the object in the Messier catalogue as he often observed with messier when they were working in the Depôt de la Marine.

At the centre of this galaxy is a supermassive black hole, pretty normal for the galaxies that we are able to observe. However, this black hole is particularly active, eating up much more material that the black hole of our galaxy, and emitting a large amount of microwave radiation in the process.

The galaxy appears to have four arms, the second pair of which can be seen faintly in visible light but observe them in an electromagnetic wave we can’t see such as X-ray or radio waves and it reveals a much more prominent arm made of hot gas unusually. Astronomers have an idea that these are actually a phenomenon caused by the active supermassive black hole in the heart of the galaxy. The arms may be jets of material produced by the violent churning of the black hole. As the jets pass through the galactic matter, they excite the particles in the dense gas and cause them to produce light and other radiation.

M106 is classed as a SABbc type galaxy. This means that it is an intermediate between a normal and barred spiral galaxy.
The galaxy is also classed as a Seyfert II galaxy. It has a considerably larger emission in radio rather than visible light and exhibits emission line spectra from the nucleus. These unusual emission lines and X-rays indicates that a portion of the galaxy may be falling into the central active supermassive black hole. This is what usually classifies Seyfert galaxies.

M106 is also a water maser galaxy. It has a dense disk that works as a maser (Microwave Amplifier by Stimulated Emission of Radiation). A maser is a microwave laser on a galactic scale and in our case is caused by water vapour. The nuclear megamaser ring, which made it possible to directly measure the distance a galaxy for the first time, is responsible for its purple colour. This measurement or the maser’s positions, velocities and accelerations played an important role in calibrating the cosmic distance ladder.

Another way M106 helped with the cosmic distance ladder was through Cepheid Variables. These are a type of star that pulsates radially, varying in both diameter and temperature and producing changes in brightness with a well-defined stable period and amplitude.  Before, Cepheid variables from other galaxies could not be used to measure distances as they covered ranges of metallicities different from the Milky Way’s. The variable in M106 contains Cepheid variables similar to both the metallicities of the Milky Way and other galaxies’ Cepheids. By measuring the distance of the Cepheids with metallicities similar to our own Milky Way astronomers were able to recalibrate the other Cepheids with different metallicities.

Observations by the Very Large Baseline Array radio telescope in 1995 show that M106 may contain a number of massive dark objects, with 36 million solar masses contained within a volume of about 1/24 to 1/12 light year radius.

Two supernovae have been discovered in M106, the most recent being detected on May 20, 2014 at magnitude 14.8. it was classified as a Type II supernova. There was also a supernova detected in 1981 which reached magnitude 16.

Research Assistant: Charlotte Greenham




Messier 106
M106, NGC 4258
Spiral Galaxy
Canes Venatici
24 million light years
18 arcminutes
136,000 light years
1781, Pierre Mechain
12h 20m 03s
+47º 10’ 54”
Celestron EdgeHD 8" & 0.7x Reducer
10 nights in March & April 2022
RGB = 12 x 600s each
L = 70 x 1200s
29 hours 20 minutes


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