Messier 56 - the NGC 6779

Description:

"We surveyed a 6.5'×6.5' field centered on the globular cluster M56 (NGC 6779) in a search for variable stars detecting seven variables, among which two objects are new identifications. One of the new variables is an RRLyrae star, the third star of that type in M56. Comparison of the new observations and old photometric data for an RV Tauri variable V6 indicates a likely period change in the star. Its slow and negative rate of -0.005±0.003 d/yr would disagree with post-AGB evolution, however this could be a result of blue-loop evolution and/or random fluctuations of the period."

"Classical nova outbursts are the result of thermonuclear explosions on the surface of a white dwarf star in a close binary system. Material from the other star in the system (one not unlike our own sun) falls onto the surface of the white dwarf over thousands of years. The pressure at the base of this layer of accreted material builds up until thermonuclear reactions begin explosively. An Earth's mass or more of material is ejected from the surface of the white dwarf at speeds of a few hundred to a few thousand kilometres per second. Old novae are therefore surrounded by shells of ejected matter illuminated by the light from the central binary system."

"We report the possible detection of diffuse X-ray emission in the environment of NGC 6779, and find the emission to be well aligned with the proper motion of the cluster. The position of the emission suggests we are observing heated ISM in the wake of the cluster that could be the result of an interaction between the intracluster medium and the halo gas surrounding it."

History of Observation:

"Nebula without stars, having little light; M. Messier discovered it on the same day as he found the comet of 1779, January 19. On the 23rd, he determined its position by comparing it with the star 2 Cygni, according to Flamsteed: it is near the Milky Way; and close to it is a star of 10th magnitude. M. Messier reported it on the chart of the comet of 1779."

"A globular cluster, in a splendid field, between the eastern joke of Lyra's frame and the Swan's head: it is 5 1/4 deg distant from Beta Lyrae, on the south-east line leading to Beta Cygni, which is about 3 1/2 deg further. This object was first registered by M. Messier in 1778, and, from his imperfect means, described as a nebula of feeble light, without a star. In 1784, it was resolved by Sir William Herschel, who, on gauging, considered its profundity to be of the 344th order."

Locating Messier 56: