What is the M101 Pinwheel Galaxy?
The M101 Pinwheel Galaxy (also known as Messier 101 or NGC 5457) is a spiral galaxy that is located about 21 million light years from Earth in the constellation Ursa Major in the Northern Hemisphere. It is one of the nearest galaxies to the Milky Way. The M101 Pinwheel Galaxy was discovered by the French astronomer and surveyor Pierre Méchain 1781, who was a colleague of Charles Messier. Charles Messier listed M101 as one of the final entries in his list of Deep Sky objects, better known as the Messier Catalogue.
Size and Appearance of the M101 Pinwheel Galaxy
The M101 Pinwheel Galaxy is one of the largest and brightest known disk galaxies in the sky, with well-defined spiral arms formed by stars, gas, and dust. It contains over one trillion stars. This face-on spiral galaxy is also one of the most colorful and rich in detail. It has a disk mass of about 100 billion times the sun, with a central bulge (= the core) of about 3 billion times the sun. This galaxy has a diameter of about 170,000 light years. By comparison, the Milky Way has a diameter of between 100,000 and 120,000 light-years.
Messier 101 has an unusual appearance because it features a large central bulge, or nucleus, which appears to be rotating. This spinning motion is caused by the centrifugal force exerted by the large mass at the center of the galaxy. The outer edges of the nucleus are slowed down as they pass around the central bulge, resulting in a spiral pattern.
The appearance of Messier 101, just like other galaxies, can change depending on the wavelength of light in which they are observed.
How Did the M101 Pinwheel Galaxy Get Its Name?
The M101 Pinwheel Galaxy is named after its distinctive shape, which is created by the numerous swirling arms of stars that stretch out from its center, looking like a rotating pinwheel. Therefore its nickname is “The Pinwheel Galaxy”.
It was Edwin Hubble in the first place who thought that galaxies should be named according to their appearance in photographic images. He arranged the different groups of galaxies in a sequence that is still used today to classify galaxies. This system is known as the Hubble sequence. The Hubble sequence is the most commonly used system for classifying galaxies, as well in professional astronomical research as in amateur astronomy.
History and Features of the M101 Pinwheel Galaxy
The M101 Pinwheel Galaxy is one of the most well-known galaxies in the universe and has been studied by many astronomers like William Herschel and Lord Rosse ever since.
The Anglo-Irish astronomer Lord Rosse was the first to document the galaxy’s spiral structure in more detail than previous astronomers. He observed M101 in a 72-inch Newtonian telescope during the second half of the 19th century.
The history of the M101 Pinwheel Galaxy is interesting because it illustrates how astronomers use different types of observations to piece together the history of galaxies. In particular, using data from the Hubble Space Telescope, researchers were able to study how masses within a galaxy are distributed and how this affects its overall evolution. This information has helped us to better understand how galaxies form and change over time.
Another interesting historical fact: Hubble proved that many objects previously thought to be clouds of dust and gas classified as “nebulae” were galaxies beyond the Milky Way. This was also the case for M101.
The M101 Pinwheel Galaxy is very active, meaning that it has a lot of star formation happening. It’s rich in red and blue stars, making Messier 101 one of the most colourful galaxies in the universe. The pink areas in the spiral arms are known as “HII regions”. That’s because these regions contain huge amounts of Hydrogen. Hydrogen is the lightest element and is the most abundant chemical substance in the universe. It constitutes roughly 75% of all matter.
The Pinwheel Galaxy is peculiar because it does not have a black hole at its center like most other large galaxies. Instead, the galaxy has a large number of X-ray sources. Stars die and their material falls into stellar-mass black holes. This material heats up when it falls and throws off X-rays.
The M101 Pinwheel Galaxy is a member of the Local Group of galaxies which includes the Milky Way and other nearby galaxies like M31 The Andromeda Galaxy and M33 The Triangulum Galaxy. The “Local Group” is a term introduced by Edwin Hubble.
The M101 Group of Galaxies is a collection of about 50 galaxies located in the constellation Ursa Major. The group is named after the M101 Galaxy, which is the brightest member and also the largest. Most of the other members of the M101 Group are companions of the Pinwheel Galaxy.
The M101 Group contains a wide variety of galaxy types. There are spiral galaxies like our own Milky Way, elliptical galaxies, and lenticular galaxies. Some of these types are easier to see than others because they have brighter stars or more prominent features. The group is one of the many other galaxy groups within the Virgo Supercluster.
How to Find the M101 Pinwheel Galaxy in the Night Sky?
The M101 Pinwheel Galaxy is easily found in the night sky, located in the constellation Ursa Major. To find it, start by looking for the Big Dipper (or “The Great Bear” as it is called in Belgium :-)) and locate its handle. The Pinwheel Galaxy is located close to the end of the handle. It can also be found using a sky chart or by using the Messier catalogue.
What Can I Expect When Viewing the M101 Pinwheel Galaxy?
The M101 Pinwheel Galaxy is a beautiful sight to behold and can be found using a medium to high-powered telescope. Messier 101 has an apparent magnitude of 7.9.
Messier 101 is large but faint and looks like an indistinct smudge through a small telescope from a suburban area. Observing with a large telescope and a low-power eyepiece from a dark site location, you can see slightly a spiral structure.
Astrophotography
The M101 Pinwheel Galaxy is one of the most iconic galaxies in the night sky and is rich with detail as stated in the text above.
When imaging this target in March this year, I wanted to go for a wide-field image (please, see picture 2). Therefore, I used an 86mm/464mm Quadruplet refractor from Telescope Optics, the TS86SDQ. The last time I imaged M101 (please, see picture 1), I was using my 8″ Newtonian telescope. For both images, I used the same filter: the STC Astro Multispectra, a broadband anti-light pollution filter that is great for galaxies. Another well-known broadband anti-light pollution filter is the L-Pro from Optolong.
The camera was a ZWO ASI533 MC Pro that I like to use for imaging larger galaxies. Many galaxies fill in nicely the FOV (Field Of View) of the square sensor of this one-shot colour camera. I’ve been experimenting with several gain and exposure settings for my wide-field image of the M101 Pinwheel Galaxy. But if you want to reveal the faintest details out of the spiral arms, it is best to use exposures of 300 seconds for each frame. The best results you’ll get are when the more or most faint details are extracted in LRGB. To highlight the HII regions, you can gain red data by using a part of your luminance data with either a red or an H-alpha filter.
The STC Astro Multsipectra filter I used, passes the predominant Hydrogen-Alpha line at 656.3nm. Therefore the HII regions (pink regions) in the M101 Galaxy of my image are already emphasized.
Image details (picture 1)
- Telescope: Sky-Watcher Explorer Black Diamond F5 N200/1000
- Mount: iOptron CEM60 on a iOptron tri-pier
- Camera: ZWO ASI294 MC Pro
- Filter: STC Astro Multispectra 2″
- Telescope control: ZWO ASIair Gen.1
- Software: Astro Pixel Processor (stacking & pre-processing); PixInsight (processing) & Affinity Photo (final touch)
No guiding, no coma corrector
Image details (picture 2)
- Telescope: Telescope Optics TS86SDQ F5.4 Quadruplet Apo
- Mount: Sky-Watcher NEQ5 Synscan GoTo
- Camera: ZWO ASI533 MC Pro
- Filter: STC Astro Multispectra 2″
- Dew Heater: DEW NOT
- Telescope control: ZWO ASIair Gen.1
- Software: Astro Pixel Processor (stacking & pre-processing); PixInsight (processing) & Affinity Photo (final touch)
Total integration time: 13.46 hours
No guiding
Data was captured on the nights of 10/03-11/03/2022, 24/03-25/03/2022, and 26/03-27/03/2022.
SQM-L (average): 18.91 -> Bortle Class 6
