Medulla Nebula (CTB 1)
In 1955 the American astronomer George Ogden Abell discovered during a survey of the «Palomar Observatory Sky Survey» (POSS) a large arc-like nebula with low surface brightness that he first thought was an old planetary nebula. He listed it in his 1955 publication as number 72. 
R. W. Wilson and J. G Bolten of the California Institute of Technology Radio Observatory did a survey of galactic radiation in 1959. They scanned the sky at a frequency of 960 Mc/s with an antenna of 0.8° beam width over a range of 300° in galactic longitude and found 110 discrete radio sources. Some of them could not be identified visually with objects on the POSS plates, so also the entry listed as number 1 (CTB 1, CTB = Caltech Observation List B), which had a diameter of about 1°. 
In 1965 the American astronomer Beverly T. Lynds published her catalog of bright nebulae. The nebula is listed there as H-II region LBN 116.81+00.03 (LBN 576). 
In Abells second publication of his survey of old planetary nebulae in 1966 he listed the nebula with the number 85 and a diameter of 2077 x 2077 arcseconds. He described it as a not symmetrical ring with bright spots or regions. He also noted: «The center of the extended radio source CTB-1 [...] is 0.4° east of the nebula; it may be a supernova remnant.» 
In 1968 CTB 1 was then confirmed to be a supernova remnant by A. Poveda and L. Woltjer. 
On very long exposure images, the nebula appears as a gas bubble, which resembles a cross section through a human brain with spinal cord extension (medulla oblongata), which is why CTB 1 got the nickname «Medulla Nebula» among amateur astronomers.
CTB 1 is the remnant of a supernova, the death of a massive star whose core collapses after its nuclear fuel is consumed. The radio pulsar PSR J0002+6216 has been identified to be born from the same supernova. The pulsar lies at the apex of a narrowly collimated cometary-like 7 arcminutes long tail of nonthermal radio emission, which was identified as a bow-shock pulsar wind nebula. The tail of the nebula points back toward the geometric center of the supernova remnant CTB 1. At a distance of 2 kpc the pulsar shows a large transverse velocity of 1100 km/s. An asymmetric supernova explosion could be the cause for this pulsar natal kick velocity. The age of the supernova is estimated to 10'000 years. 
The supernova remnant CTB 1 is located in the constellation Cassiopeia and is circumpolar for Central Europe. The best time to observe is July to January, when it is highest at night.