M1 0n 12-17-2007
Done with my 17.5 inch scope and SBIG ST-9E CCD camera
Supernova Remnant M1 (NGC 1952) in Taurus
The Crab Nebula
The most conspicuous known supernova remnant. The supernova was noted on July 4, 1054 A.D. by Chinese astronomers, and was about as bright as the Full Moon, and visible in daylight for 23 days. It was probably also recorded by Anasazi Indian artists (in present-day Arizona and New Mexico), as findings in Navaho Canyon and White Mesa (both AZ) as well as in the Chaco Canyon National Park (NM) indicate. The Supernova 1054 was also assigned the variable star designation CM Tauri.
The nebulous remnant was discovered by John Bevis in 1731, according to Messier, who independently found it on August 28, 1758, and first thought it was a comet. Of course, he soon recognized that it had no apparent proper motion and cataloged it on September 12, 1758. It was christened the "Crab" on the ground of a drawing made by Lord Rosse about 1844.
The nebula consists of the material ejected in the supernova explosion, which has spread over a volume of approximately 10 light years. It is still expanding at a very high velocity of about 1,800 km/sec. It emits light which consists of two major contributions: A reddish component which forms a chaotic web of bright filaments, which has an emission line spectrum like that of diffuse gaseous (or planetary) nebulae, and a blueish diffuse background of highly polarized "synchrotron radiation", which is emitted by high-energy (fast moving) electrons in a strong magnetic field. Synchrotron radiation is also apparent in other explosive processes in the cosmos, e.g. in the active core of the irregular galaxy M82 and the peculiar jet of giant elliptical galaxy M87.
In 1948, the Crab nebula was identified as a strong source of radio radiation. X-rays from this object were first detected in 1964 with a high-altitude rocket; the energy emitted in X-rays by the Crab nebula is about 100 times more than that emitted in the visual light. Nevertheless, even the luminosity of the nebula in the visible light is enormous: At its distance of 6,300 light years, its apparent brightness corresponds to an absolute magnitude of about -3.2, or more than 1000 times the suns brightness.
In 1968, a pulsating radio source, named the Crab Pulsar (also cataloged as NP0532), was discovered in M1. It has now been established that this pulsar is a rapidly rotating neutron star. It rotates about 30 times per second. The neutron star emits pulses in virtually every part of the electromagnetic spectrum from a "hot spot" on its surface. The neutron star is an extremely dense object, denser than an atomic nucleus, concentrating more mass than contained in the sun in a volume only 30 kilometers across. It's rotation is slowly decelerating by magnetic interaction with the nebula. The magnetic interaction is a major energy source which makes the nebula shine.
In the visible light, the pulsar is 16th apparent magnitude. This means that this very small star has an absolute magnitude of +4.5, or about the same luminosity as our sun in the visible part of the spectrum!
Right Ascension 05 : 34.5 (hours : minutes)
Declination +22 : 01 (degrees : minutes)
Distance 6,300 light years
Visual Magnitude 8.2
Apparent Dimension 6x4 (arc minutes)
M1 on 12-12-2005
Done with my 17.5 inch scope and SBIG ST-7E CCD camera
OBJECT = M1
TELESCOPE = 17.5 inch f4.5
CAMERA = ST7-E
OBSERVER = Rusty Fletcher
LOCATION = Seguin Outdoor Learning Center
DATE (Yr-Mo-Dy) = 2004-12-11
TIME (UT) = 04:43:06
TOTAL EXPOSURE = 480 sec
IMAGES STACKED = 8
To Home Page