A GLOWING POOL OF LIGHT
NGC 3132 is a striking example of
a planetary nebula. This expanding cloud of gas,
surrounding a dying star, is known to amateur astronomers
in the southern hemisphere as the "Eight-Burst"
or the "Southern Ring" Nebula.
The name "planetary nebula" refers
only to the round shape that many of these objects
show when examined through a small visual telescope.
In reality, these nebulae have little or nothing
to do with planets, but are instead huge shells
of gas ejected by stars as they near the ends of
their lifetimes. NGC 3132 is nearly half a light
year in diameter, and at a distance of about 2000
light years is one of the nearer known planetary
nebulae. The gases are expanding away from the central
star at a speed of 9 miles per second.
This image, captured by NASA's Hubble
Space Telescope, clearly shows two stars near the
center of the nebula, a bright white one, and an
adjacent, fainter companion to its upper right.
(A third, unrelated star lies near the edge of the
nebula.) The faint partner is actually the star
that has ejected the nebula. This star is now smaller
than our own Sun, but extremely hot. The flood of
ultraviolet radiation from its surface makes the
surrounding gases glow through fluorescence. The
brighter star is in an earlier stage of stellar
evolution, but in the future it will probably eject
its own planetary nebula.
In the Heritage Team's rendition
of the Hubble image, the colors were chosen to represent
the temperature of the gases. Blue represents the
hottest gas, which is confined to the inner region
of the nebula. Red represents the coolest gas, at
the outer edge. The Hubble image also reveals a
host of filaments, including one long one that resembles
a waistband, made out of dust particles which have
condensed out of the expanding gases. The dust particles
are rich in elements such as carbon. Eons from now,
these particles may be incorporated into new stars
and planets when they form from interstellar gas
and dust. Our own Sun may eject a similar planetary
nebula some 6 billion years from now.
Credit: NASA and The Hubble
Heritage Team (STScI/AURA)
Acknowledgment: R. Sahai (Jet Propulsion Lab)