230325 - M101 "Pinwheel" galaxy
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click image to enlarge
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ASTRO:
type=Spiral galaxy const=Ursa Major mag=7.9 dist=21 M ly size=170 k ly IMAGE: location=EB Driveway BrtlCls=4 exposure=CMOS OSC: 137x180s (6.9h), Gain123* EQUIPMENT: camera=ZWO ASI2600MC-Pro optics=ES102, 24mmEP prjtn, FL(eff)=1238mm, f/12.1 filter=Optolong L-Pro LPS mount=Celestron AVX guiding=Orion 60x240mm, ZWO ASI224MC SOFTWARE: acquisition=Stellarium, APT, PHD2, Processing=DSS, PhotoshopCC, RCAstro, StarNet++, TopazDeNoiseAI, LrC |
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The Pinwheel Galaxy, also known as Messier 101 (or M101) and NGC 5457 is a face-on spiral galaxy located appx 21 M light-years away from Earth in the constellation Ursa Major. It was discovered by Pierre Méchain in 1781 and was communicated that year to Charles Messier, who verified its position for inclusion in the Messier Catalogue as one of his final entries.
On February 28, 2006, NASA and the ESA (European Space Agency) released a very detailed image of the Pinwheel Galaxy, which was the largest and most-detailed image of a galaxy by Hubble Space Telescope at the time. The image was composed of 51 individual exposures, plus some extra ground-based photos.
M101 is a large galaxy, with a diameter of 170,000 light-years, making it comparable to the Milky Way in size. But it is more massive, containing around a trillion stars, and having a disk mass on the order of 100 billion solar masses, along with a central bulge that, although small in size, contains a mass of appx 3 billion solar masses. These latter characteristics can be compared to those of Andromeda Galaxy. M101 is asymmetrical due to tidal forces generated from interactions with companion galaxies. These gravitational interactions compress interstellar hydrogen gas, which then triggers strong star formation activity in M101's spiral arms that can be detected in ultraviolet images. It is estimated that M101 has about 150 globular clusters, comparable to the 147 presently known in the Milky Way.
M101 has a high population of H-II regions, many of which are very large and bright. H-II regions usually accompany the enormous clouds of high density molecular hydrogen gas contracting under their own gravitational force, and are locations where stars form. H-II regions are ionized by large numbers of extremely bright and hot young stars; those in M101 are capable of creating hot superbubbles. In a 1990 study, 1,264 H-II regions were cataloged inside the galaxy. Three (3) were prominent enough to receive New General Catalogue numbers—NGC 5461, NGC 5462, and NGC 5471.
In 2001, using the Chandra X-ray Observatory, scientists observed the X-ray source P98 inside M101, and identified it as an ultra-luminous X-ray source—a source more powerful than any single star. It received the designation M101 ULX-1. Then in 2005, Hubble together with the XMM-Newton space observatory showed the presence of an optical counterpart, strongly indicating that M101 ULX-1 is an X-ray binary. Further observations showed that the system deviated from expected models, and more closely resembled that of a Black Hole. The mass of this black hole is small (as black holes typically go), with a mass of just 20 to 30 solar masses; but, it consumes material (including captured stellar wind) at a very high rate.
To observe the spiral structure of M101 in modern telescopes requires a fairly large instrument, very dark skies, and a low-power eyepiece. Thanks to their large apertures, Dobsonian reflector telescopes make an excellent choice for such observations. The Pinwheel's face-on orientation and fairly large apparent size in the sky make it a favorite of amateur astrophotographers. Instruments having 8 - 10" diameter, in either reflector or catadioptric configurations, seem to be ideal allowing the galaxy to fill the telescope field of view ("FOV") for photographic purposes.
On February 28, 2006, NASA and the ESA (European Space Agency) released a very detailed image of the Pinwheel Galaxy, which was the largest and most-detailed image of a galaxy by Hubble Space Telescope at the time. The image was composed of 51 individual exposures, plus some extra ground-based photos.
M101 is a large galaxy, with a diameter of 170,000 light-years, making it comparable to the Milky Way in size. But it is more massive, containing around a trillion stars, and having a disk mass on the order of 100 billion solar masses, along with a central bulge that, although small in size, contains a mass of appx 3 billion solar masses. These latter characteristics can be compared to those of Andromeda Galaxy. M101 is asymmetrical due to tidal forces generated from interactions with companion galaxies. These gravitational interactions compress interstellar hydrogen gas, which then triggers strong star formation activity in M101's spiral arms that can be detected in ultraviolet images. It is estimated that M101 has about 150 globular clusters, comparable to the 147 presently known in the Milky Way.
M101 has a high population of H-II regions, many of which are very large and bright. H-II regions usually accompany the enormous clouds of high density molecular hydrogen gas contracting under their own gravitational force, and are locations where stars form. H-II regions are ionized by large numbers of extremely bright and hot young stars; those in M101 are capable of creating hot superbubbles. In a 1990 study, 1,264 H-II regions were cataloged inside the galaxy. Three (3) were prominent enough to receive New General Catalogue numbers—NGC 5461, NGC 5462, and NGC 5471.
In 2001, using the Chandra X-ray Observatory, scientists observed the X-ray source P98 inside M101, and identified it as an ultra-luminous X-ray source—a source more powerful than any single star. It received the designation M101 ULX-1. Then in 2005, Hubble together with the XMM-Newton space observatory showed the presence of an optical counterpart, strongly indicating that M101 ULX-1 is an X-ray binary. Further observations showed that the system deviated from expected models, and more closely resembled that of a Black Hole. The mass of this black hole is small (as black holes typically go), with a mass of just 20 to 30 solar masses; but, it consumes material (including captured stellar wind) at a very high rate.
To observe the spiral structure of M101 in modern telescopes requires a fairly large instrument, very dark skies, and a low-power eyepiece. Thanks to their large apertures, Dobsonian reflector telescopes make an excellent choice for such observations. The Pinwheel's face-on orientation and fairly large apparent size in the sky make it a favorite of amateur astrophotographers. Instruments having 8 - 10" diameter, in either reflector or catadioptric configurations, seem to be ideal allowing the galaxy to fill the telescope field of view ("FOV") for photographic purposes.