A new infrared picture reveals the intricate structure of the Helix Nebula, the rust-colored remains of a star like our sun that puffed up as it died and shed its shells of gas and dust into space. These thin of molecular gas are difficult to see in visible light, but infrared detectors can pick them out, and they show up in the new image as a dark red haze. The Helix Nebula is a complex object composed of dust, ionized material and molecular gas, arrayed in an intricate, flower-like pattern.
The dying star at
the heart of the Helix Nebula is evolving to become a white dwarf, a shrunken,
super-dense object that can pack a sun's worth of material into a sphere the
size of Earth. The star is visible as a tiny blue dot at the center of the
The main ring of
the Helix is about 2 light-years across, roughly equivalent to half the
distance between our sun and its closest star. However, wispy material from the
nebula spreads out at least 4 light-years into space from the central star.
In visible light,
fine details in the Helix are largely obscured by dust. But the infrared
view—snapped by the European Southern Observatory's VISTA telescope—can pierce
this veil to see radiating filaments of cooler gas in the rings as well as a
faint halo of thinly spread gas that extends to at least four light-years from
the dead star's core.
Nebula, in astronomy, refers to a localized conglomerate of
the gaseous and finely divided dust particles that are spread throughout
interstellar space. Before the invention of the telescope, the term nebula
(Latin, “cloud”) was applied to all celestial objects of a diffuse appearance.
As a result, many objects now known to be star clusters or galaxies were called
Nebulas exist within other galaxies as well as in our own
Milky Way galaxy. They are classified as planetary nebulas, supernova remnants,
and diffuse nebulas, including reflecting, emission, and dark nebulas. Small,
very bright nebulas known as Herbig-Haro objects are found in dense
interstellar clouds, and are probably the products of gas jets expelled by new
stars in the process of formation.
Helix Nebula was discovered
by Karl Ludwig Harding, probably before 1824. It is one of the closest to the Earth
of all the bright planetary nebulae. The estimated distance is about 215
parsecs or 700 light-years.
Helix is a planetary nebula, a
strange object that forms when a star like our sun exhausts its hydrogen fuel.
The star's outer layers expand and cool, creating a huge envelope of dust and
gas. Radiation flowing from the dying star ionizes this envelope, causing it to
glow. Despite their name, planetary nebulas have nothing to do with planets.
Rather, the term refers to their superficial resemblance to giant planets, when
observed through early telescopes. (Adapted from National Geographic,
Wikipedia, Encarta encyclopedia, and Internet sources)