Where is hourglass nebula

The central white dwarf that illuminates the nebula lies off centre, which is unusual for a planetary nebula, because progenitor stars are expected to lie at the centre of symmetry. The anomaly may be explained by the presence of a companion, which would make the central star part of a binary system. Mayall between and , during their work on an extended Henry Draper Catalogue, an astronomical star catalogue providing spectroscopic classifications for hundreds of thousands of stars.

At the time, the object was noted simply as a small faint planetary nebula because its shape was not discovered until much later, when advanced imaging techniques and improved telescopes became available.

About 10 thousand million years after they are born, stars like the Sun become cooler, larger, and redder, becoming what are known as 'red giant' stars. As red giants age, they eventually cast off the outer layers of their surfaces. Ultraviolet light from the remaining stellar cores makes the surrounding material glow, producing what are known as 'planetary' nebulae, like the Hourglass Nebula, MyCn The hot star which has been thought to eject and illuminate the nebula, and therefore expected to lie at its center of symmetry, is clearly off center.

Hence MyCn18, as revealed by Hubble, does not fulfill some crucial theoretical expectations. Hubble has also revealed other features in MyCn18 which are completely new and unexpected.

For example, there is a pair of intersecting elliptical rings in the central region which appear to be the rims of a smaller hourglass. The Hourglass nebula , also called the Engraved Hourglass nebula or the Etched Hourglass nebula, is a planetary nebula in the constellation of Musca. The star , a white dwarf, at the centre of the nebula is somewhat offset from the exact centre also puzzles astronomers. This throws into question the current belief of how planetary nebulae form, as this would mean the star should be along the axis of symmetry of the nebula.

Mayall, some time between and The structure of the nebula was not established until , when better telescopes and advanced imaging techniques became available. Then nebula is composed of two large lobes that meet at a central star , giving it a shape like an hourglass.