M27 - The Dumbell Nebula
The Dumbbell Nebula is one of the brightest of its type. This is also the first image of a planetary nebula photographed by the recently completed College View Observatory near Warren Wilson College. The designation "planetary nebula" for this kind of object was given by Sir William Herschel mainly because its image resembled a disk-like planet in the primitive telescopes of the 18th century.
Such a nebula will probably be the ultimate fate of the
Sun in about 6 billion years from now. When a star
like the Sun uses up all its nuclear fuel (Hydrogen, Helium,
Carbon, ... all converging to Iron), compression by the
star's strong gravitational force no longer leads to nuclear
fusion into heavier elements, and the nuclear process shuts
down. The star collapses to form an extremely dense
star at the center called a white dwarf (the star at the
center of this nebula). Much of the outer envelope of
the former sun-like star has rebounded and is expanding over
time. The white dwarf is about the size of the Earth,
(1/100 the solar diameter) and it contains about the mass of
the Sun. This collapse results in a volume about
1/millionth the original star, hence the white dwarf is
about a million times more dense than the Earth (and
Sun). At these densities, the matter in a white dwarf
is unlike ordinary matter. The electron orbits in the
atoms of the white dwarf have all collapsed from the extreme
pressure. The electrons in white dwarf matter are said
to be "degenerate". One electron cannot be
localized from another. All the electron orbitals that
we learn in elementary Chemistry are collapsed.
The nebular material (the glowing halo) consists of gas
from the parent star that is expanding out into space.
The estimated distance from the Earth to this nebula is
about 1200 light years. The angular size in the
photographs predict the physical size of the expanding gas
to be about 3 light years in diameter. That is about
90,000 times the diameter of Earth's orbit around the
Sun! Thus when the Sun "dies" into a planetary nebula,
all the planets will be engulfed by the nebula. Life
on Earth would be terminated - not so much by the expanding
Sun's atmosphere - but by the sheer ultimate brightness of
the white dwarf compared to the Sun. The Sun's surface
temperature is about 6000 deg K. In contrast a white
dwarf is about 30,000 deg K - about 5 times hotter.
The radiation emitted, proportional to the 4 power of the
absolute temperature, will be about 54 = 625
times greater - incinerating all life on the Earth as we
Keep tuned. Shortly we plan to obtain an image of
another planetary nebula - the ring nebula - at the College
View Observatory. This image was made with a DSLR
camera mounted on a 14 inch aperture telescope given to
Warren Wilson by alumnus Gary Starkweather (WWC class of
Physics Photo of the Week is published weekly during the academic year on Fridays by the Warren Wilson College Physics Department. These photos feature interesting phenomena in the world around us. Students, faculty, and others are invited to submit digital (or film) photographs for publication and explanation. Atmospheric phenomena are especially welcome. Please send any photos to firstname.lastname@example.org.
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