Helix Nebula (NGC 7293)

Comet-like knots revealed by Hubble

The nearest planetary nebula to the Sun. The Helix Nebula lies in the constellation Aquarius and was discovered by Karl Ludwig Harding before 1824. In apparent size (including an outer halo) it is almost as big as the full Moon.

Observations by the Hubble Space Telescope of the inner edge of the Helix's main ring have resolved fine details associated with the long-known radial structures. These details include thousands of comet-like knots, the heads of which are larger than our solar system. Hot, fast moving shells of nebular gas overrunning cooler, denser, slower shells ejected by the star during an earlier expansion may have produce these droplet-like condensations as the two shells intermixed and fragmented.¹ An intriguing, if somewhat remote, possibility is that instead of dissipating over time, these objects might eventually collapse to form Pluto-like bodies. If so, small icy worlds created near the end of a star's life would be numerous in our galaxy.

visual magnitude	7.3
angular size	core: 16'; halo: 28'
linear diameter	2.5 light-years
distance	~650 light-years (200 pc)
position	R.A. 22h 29m 38.6s; Dec. -20° 50' 13.6"
other designations	PN G036.1-57.1, ESO 602- 22, PN ARO 17

Reference

Dyson, J. E., Pittard, J. M., Meaburn, J., and Falle, S. A. E. G. "The tails in the Helix Nebula NGC 7293." Astronomy & Astrophysics, 457, 561-567 (2006).

Related category

• NEBULAE AND STAR CLUSTERS

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