Cat’s Eye Nebula

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The Cat’s Eye nebula, also known as NGC 6543, is a planetary nebula in the Draco constellation and is about 3300 light years from Earth. It is one of the most complex nebulae known. High resolution observations from the Hubble space telescope reveal remarkable structures like knots, jets, bubbles and sinewy arc features. At the center of the nebula there is a bright, hot star. Around 1000 years ago, this star lost its outer envelope and produced the nebula.

The Cat’s Eye nebula was discovered in mid-February, 1786 by William Herschel. Also, it was the first nebula whose spectrum was explored by an amateur astronomer named William Huggins. The results of his investigation proved that planetary nebulae consist of hot gases, but not stars. Currently, nebula have been observed across the full electromagnetic spectrum, from far infrared to X-rays. Modern studies have revealed several mysteries about the nebula. The intricate structure may have been caused by materiel from a central binary star, but there is no concrete evidence of the companion star. Hubble Telescope observations revealed a number of faint rings around the Cat’s Eye. These rings are spherical shells ejected by the central star in the distant past. No one seems to be able to figure out the mechanism of those past ejections.

The Cat’s Eye nebula is a well-studied planetary nebula. It is fairly bright with a magnitude of 8.1. It has a high surface brightness. The constellation is situated at right ascension 17h 58 m 33.4 s and declination +66°37’59?. The Eye’s high declination means it is easily observable from the Northern Hemisphere. NGC 6543 is almost exactly in the direction of the North Ecliptic Pole. The bright inner nebula itself is rather small. The major axis of the inner ellipse is 16.1 arcseconds. The distance between the condensations is 24.7 arcseconds. It has an extended halo of matter that the creating star ejected during its red giant phase. This halo extends over a diameter of about 5 arcminutes. The Cat’s Eye really covers a nice chunk of the galaxy.

The central star of the Cat’s Eye nebula is a WR type star. It has a temperature of approximately 80,000 degree kelvin. It is approximately 10,000 times as luminous as our Sun and its radius is about 0.65 times that of Sol. Spectroscopic analysis shows that the star is currently losing mass in a fast stellar wind at a rate of about about 20 trillion tons per second. The velocity of this wind is about 1900 km/s. Calculations indicate that the central star currently weighs just over one solar mass, but theoretical calculations show that it may have had an initial mass of five solar masses.

There is a nice article about the Cat’s Eye nebula at this link. Here on Universe Today we have a great article that looks right into the Cat’s Eye. Most of the images we see of the nebula today were taken from the Hubble Space Telescope. Astronomy Cast offers a good episode about the man himself, Edwin Hubble.

Sources: Caltech Astronomy, SEDS

Tagged as: Cat's Eye Nebula, NGC6543