One of these can dramatically improve the appearance of emission nebulae and will also improve many planetary nebulae
. While UHCs darken the sky background substantially, they are not so strong as to render dim stars in the field invisible, so they present the most attractive and normal-looking views.
Since then, and especially since the repair of Hubble in 1993, scientists have found planetary nebulae
in a bewildering variety of shapes.
Only 900 light-years away and shining at magnitude 7.3, the Dumbbell is one of the brightest planetary nebulae
in the heavens.
International Conference on Planetary Nebulae
as Astronomical Tools (2005: Gdansk, Poland) Ed.
A few planetary nebulae
have been reported to have a variable brightness .
For instance acetylene, detected around red giants, served as a building block for molecules such as benzene and more complicated aromatic hydrocarbons present in planetary nebulae
In a tour of planetary nebulae
in the February 1960 issue of Sky & Telescope, Leland S.
Prof Zijlstra adds: "Old, low mass stars should make much fainter planetary nebulae
than young, more massive stars.
Speakers at the meeting included the Director, who gave his review of the Section year and showed a selection of images received, Bob Winter on the death of stars, Robin Leadbeater on the spectra of dying stars, Owen Brazell on new planetary nebulae
, Chris Longthorn on observing from New Mexico Skies, Andrew Robertson on building and using a large Dobsonian telescope and David Boyd on the behaviour of Gyulbudaghian's Nebula and PV Cephei.
The topics here are hot and cool white dwarves, carbon and oxygen in cool white dwarves, planets orbiting white dwarves, observations of white dwarf circumstellar disks, the origin and evolution of white dwarf dust disks, and revelations from the infrared about planetary nebulae
about white dwarves.
At a distance of 650 light-years, Helix is one of the closest known planetary nebulae
. These glowing bodies got their moniker a century ago when astronomers, using the smaller telescopes of the time, described their appearance as planetary disks.