PinWheel galaxy – The most detailed galaxy captured by Hubble telescope

On March 27. 1781 Pierre Mèchain discovered Messier 101, also know as the PinWheel galaxy. The galaxy is described as a nebula without a star. It’s 21 million light-years away from the planet earth, and it’s based in the constellation Ursa Major. Once it was discovered, it was communicated to Charles Messier, who confirmed, its position and includes it in its own catalog of stars and comets, called Messier Catalogue.

Back on February 28. 2006, Nasa and also the European Space Agency released the most detailed image ever captured by Hubble. It was an image of Measier 101 ( Pinwheel Galaxy, M101 or NGC5457) which was very detailed and obscure, it was composed of 51 individual exposure, + ground-based photos. 

In 2011 on August 24, M101 has discovered a Type Ia Supernova, SN 2011fe in it.

This beautiful galaxy was one of the greatest images captured by the Hubble space telescope.

Discovery of the M101

As we mentioned earlier, Piere Mèchain, described his discovery as a “nebula without a star” the galaxy it’s self is pretty large and very obscure. Its diameter is between 6 to 7 it’s between the left hand of Bootes and the tail of the Great Bear. It’s very difficult to differentiate when one lits the wires.

William Herschel noted that in 1784 in his 7-, 10-, and 20-feet [focal lenghts] reflectors, revealed a mottled kind of nebulosity, which he called resolvable. He also stated “I expect my present telescope will, perhaps, render that stars visible of which I supposed them to be composed.

Another scientist observed the PinwheelGalaxy, his name is Lord Rosse. He used Newtonian reflector during(72-inch-diameter) the second half of the 19th century. He was the first scientist to made large notes about the spiral structure of M101 and he did sever sketches. This step was very hard back in the century, in the modern world, to be able to observe the spiral structure, will require a really big instrument, black skies, and a low-power eyepiece.

Structure and arrangement of M101

The Pinwheel galaxy is a very large galaxy with a diameter of 170,000 light-years. If we compare it with the Milky way it has 70 000 light-years more. It has 1 trillion stars, which is twice the number in the Milky Way. Its disk mas on the order of 100 billion solar masses, froward with a small bugle in the center of 3 billion solar masses.

The galaxy has a high density of H II regions, a lot of which are very bright and large. HII regions usually follow the enormous clouds of high-density molecular hydrogen gas, getting under their personal gravitational force where stars form. Those regions are ionized by a large quantity of extremely bright and heated young stars, those M1010 are capable of inventing hot superbubbles.

In a study that was made in 1990, 1264 H II regions were cataloged in the galaxy, but only three were notable enough to receive New General Catalogue numbers -NGC 5461, NGC 5462, AND NGC 5471.

M101 is asymmetrical because of the strong forces from its partner galaxies. These strong gravitational interactions, reduce the interstellar hydrogen gas, which then triggers a powerful star formation activity in M101’s spiral arms that can be recognized in ultraviolet images.

PinWheels arms

M101 spiral arms are spattered with the vast region of star-forming nebulae. Pinwheels are of nebulae are areas of great star formation within molecular hydrogen clouds. Bright young clusters of sizzling newborn blue stars trace out the spiral arms. The disk of the galaxy is that thin that Hubble easily can see many more far galaxies lying behind the foreground galaxy.

If we look through a low-power, wide-field eyepiece, we can see that M101 is a huge galaxy, faintly glowing orbicular area with a lightly brighter round core pierced at its center, by a little, nonstellar nucleus.

The determined examination will reveal, it’s spiral arms curving outward from the central core. The three arms are named Easter, Western, and Far western, based on where the arms lie related to the core.

A picture of M101's arms span and direction. Source

A picture of M101’s arms span and direction. Source


Keep in mind that even the experienced deep space observers can meet difficulties to decipher the patterns of M101’s faint spiral arms.

The eastern spiral arms start on the southwest side of the M101’s core and curve to the south. The arm then hooks around the core, narrowing into a long projection pointing northeast, and ending in a narrow tip east of the core.

 The far western arm begins on the east side of the core and heads directly north. It becomes fainter as it angles sharply to the northwest, and remains barely visible (or vanishes in smaller scopes) as it broadly curves southwest. 

Then it brightens again, as it travels and surpasses the east side of a group, of three foreground stars that form a perfect triangle.

The arms end southwest of the core, by tapping into a bright, southward-pointing spearhead shape. The western starts near the forefront star on the north side of the core and aims west toward another front star. where it abruptly turns south and then fans out. A broad dark path separates it from the final portion of the far western arm and a narrow dark lane separates it from the eastern arm.



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