Medulla Nebula (CTB 1)

CTB-1 (Abell 85)
CTB-1 (Abell 85): Contrast enhanced section of DSS2 [147]


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. [331]

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°. [597]

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). [270]

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.» [332]

In 1968 CTB 1 was then confirmed to be a supernova remnant by A. Poveda and L. Woltjer. [598]

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: Image from «Canadian Galactic Plane Survey» (CGPS). The green cross marks the geometric center of the SNR. The circles indicate the position of pulsar PSR J0002+6216. A faint tail of emission is visible from the PSR to the SNR, pointing back toward the geometric center. The inset is a higher angular resolution VLA image. [599]

Physical Properties

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. [599]

Data from Simbad [145]
Designation CTB 1, Abell 85, LBN 576
RA 23h 59m 13s
Dec +62° 26' 12"
Size 34' x 34'

Finder Chart

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.

Chart Medulla Nebula (CTB 1)
Medulla Nebula (CTB 1) in constellation Cassiopeia. Chart created using SkySafari 6 Pro and STScI Digitized Sky Survey. [149, 160]

Visual Observation

Pending ...

More Objects Nearby (±15°)


145SIMBAD astronomical database;
147Aladin Lite; (2020-12-23)
149SkySafari 6 Pro, Simulation Curriculum;
160The STScI Digitized Sky Survey;
270«Catalogue of Bright Nebulae» Lynds, Beverly T.; Astrophysical Journal Supplement, vol. 12, p.163 (1965); DOI:10.1086/190123
331«Globular Clusters and Planetary Nebulae Discovered on the National Geographic Society-Palomar Observatory Sky Survey» Abell, G. O.; Publications of the Astronomical Society of the Pacific, Vol. 67, No. 397, p.258-261, August 1955; DOI:10.1086/126815; Bibcode:1955PASP...67..258A
332«Properties of Some Old Planetary Nebulae» Abell, G. O.; Astrophysical Journal, vol. 144, p.259, April 1966; DOI:10.1086/148602; Bibcode:1966ApJ...144..259A
597«A Survey of Galactic Radiation at 960 Mc/s» R. W. Wilson and J. G. Bolton; Publications of the Astronomical Society of the Pacific, Volume 72, Number 428, 1960; DOI:10.1086/127538
598«Supernovae and Supernova Remnants» Poveda, A. ; Woltjer, L.; Astronomical Journal, Vol. 73, p. 65 (1968); DOI:10.1086/110600; Bibcode:1968AJ.....73...65P
599«The Tail of PSR J0002+6216 and the Supernova Remnant CTB 1» F. K. Schinzel, M. Kerr, U. Rau1, S. Bhatnagar, and D. A. Frail; The Astrophysical Journal Letters, Volume 876, Number 1, 2019; DOI:10.3847/2041-8213/ab18f7