Messier 94: Difference between revisions

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-[[Messier 92]] (also known as M92 or NGC 6341) is a globular cluster of stars in the northern constellation of Hercules. It was discovered by Johann Elert Bode in 1777, then published in the Jahrbuch during 1779.The cluster was independently rediscovered by Charles Messier on March 18, 1781 and added as the 92nd entry in his catalogue. M92 is at a distance of about 26,700 light-years away from Earth.
-M92 is one of the brighter globular clusters in the northern hemisphere, but it is often overlooked by amateur astronomers because of its proximity to the even more spectacular Messier 13. It is visible to the naked eye under very good conditions.
-Among the Milky Way population of globular clusters, Messier 92 is among the brighter clusters in terms of absolute magnitude. It is also one of the oldest clusters. Messier 92 is located around 16 kly (4.9 kpc) above the galactic plane and 33 kly (10 kpc) from the Galactic Center.[11] The heliocentric distance of Messier 92 is 26.7 kly (8.2 kpc). The half-light radius, or radius containing half of the light emission from the cluster, is 1.09 arcminutes, while the tidal radius is 15.17 arcminutes. It appears only slightly flattened, with the minor axis being about 89% ± 3% as large as the major axis.<ref>[http://en.wikipedia.org/wiki/Messier_92 Messier 92]</ref>
+[[Messier 94]] (also known as NGC 4736) is a spiral galaxy in the constellation Canes Venatici. It was discovered by Pierre Méchain in 1781,and catalogued by Charles Messier two days later. Although some references describe M94 as abarred spiral galaxy, the "bar" structure appears to be more oval-shaped.The galaxy is also notable in that it has two ring structures.
+M94 contains both an inner ring with a diameter of 70" and an outer ring with a diameter of 600". These rings appear to form at resonance locations within the disk of the galaxy. The inner ring is the site of strong star formation activity and is sometimes referred to as a starburst ring. This star formation is fueled by gas that is dynamically driven into the ring by the inner oval-shaped bar-like structure.[9]
+A 2009 study conducted by an international team of astrophysicists revealed that the outer ring of M94 is not a closed stellar ring, as historically attributed in the literature, but a complex structure of spiral arms when viewed in mid-IR and UV. The study found that the outer disk of this galaxy is active. It contains approximately 23% of the galaxy's total stellar mass and contributes about 10% of the galaxy's new stars. In fact, the star formation rate of the outer disk is approximately two times greater than the inner disk because it is more efficient per unit of stellar mass.<ref>[http://en.wikipedia.org/wiki/Messier_94 Messier 94]</ref>