|
November 22, 2010
Newsletter:
Gammas in the Mist
There have been
some new
cosmic discoveries: Gamma Ray Bubbles and a new Black Hole, both decked
out in bright holiday colors.
NASA’s
newest major space observatory, the Fermi Gamma Ray Space Telescope
(FGST) has detected an immense structure coming from the center of our
galaxy, the Milky Way. The FGST image, released two weeks ago, shows
the entire sky imaged with gamma rays, light from the highest energy
part of the spectrum. The Milky Way, mostly seen in white, spans the
mid-line of this image. At image center is Sagittarius A*, a
super-massive black hole at the center of our galaxy. Two large
“bubbles” are seen, in white and red, billowing up and down from the
galaxy center. The bubbles span 50,000 light-years (300 million,
billion miles), about half the diameter of our galaxy.
Scientists
will ponder these bubbles for many years to come, but initial
indications are that they are caused by gamma rays made by intense jets
of very high-energy particles coming from the fringes of Sagittarius
A*. As gas, stars, or the odd planet plunge toward a black hole, that
material is heated to millions of degrees and a portion of it shoots
out along the magnetic field lines emanating from the black hole’s
north and south poles. Fortunately, these jets aren’t aimed at Earth—we
are within the galactic disk and far from its center. Sagittarius A* is
relatively svelte, “only” 4 million times more massive than our Sun,
indicating that it has dined modestly for billions of years and emitted
much less radiation than central black holes in other galaxies, some of
which are 2000 times more massive.
More on the
Fermi gamma ray telescope is available on my on-line radio
show “Gamma
Ray Astronomy”, an interview with one of its key
developers, Dr. Leon Rochester.
More on black
holes and their eating habits is available on my show “Peek Into
a Black Hole.”
My Radio
Shows Are Back.
Some people reported problems accessing my older on-line radio shows.
Turns out, old files are eventually deleted by the broadcast network.
To fix this, web mistress Joan moved all my radio shows to our website
www.guidetothecosmos.com. There shouldn’t be any more problems, but
please let us know if you have trouble listening to the shows you want.
(You may have to reload a radio show page before you can listen to the
updated version if your browser loads the old pages from your cache
memory. Just hit the funny arrow at the top of the page to reload.)
The beautiful spiral Galaxy
M100,
one of the brightest galaxies in the Virgo Cluster, is shown below.
Virgo contains over 1500 galaxies and dominates the Local Supercluster,
of which our own Local Group of over 40 galaxies is a small and distant
member.
M100 is 160,000 light-years across (1 billion,
billion miles), 55 million light-years away, and was first seen in
1781. Nearly 200 years later, Gus Johnson, an amateur astronomer and
middle school teacher, discovered a supernova (an exploding massive
star) in M100. It was the third supernova discovered in 1979 and was
therefore named SN1979C. The star that created this supernova is
estimated to have been 20 times as massive as our Sun.
Supernovae
can be billions of times brighter than a normal star, but they fade
away within a few months. Astronomers kept a careful telescope on that
spot ever since. They discovered SN1979C has been replaced by a strong,
steady x-ray source, consistent with x-ray emission from the accretion
disk of a black hole. The accretion disk is formed by material falling
toward the black hole. The disk swirls around the black hole, slightly
beyond its event horizon. If so, this is the newest (31 years old)
nearby black hole ever detected. Welcome to the “neighborhood”.
Saying
the supernova occurred in 1979 and the black hole is only 31 years old
is common shorthand in astronomy, referring to the dates we observed
such events. To be more precise, since M100 is 55 million light-years
away, SN1979C occurred in M100 55 million years before 1979. We only
saw it in 1979 because its light took 55 million years to reach us. The
image we see is a time capsule made of light that has been traveling
toward us for all that time.
For
more on
finding supernova and
the contribution made by amateur
astronomers, check out two of my on-line radio shows: “Hunting
Supernovae in Your Spare Time” with Tim Puckett, head of a
large group of amateur supernova hunters; and “World’s
Youngest Supernova Discoverer” with Caroline Moore, who
discovered SN2008ha at age 14.
This
image was released one week ago, and is a combination of images taken
in different parts of the light spectrum by NASA’s Chandra x-ray space
telescope and the ESA’s VLT land-based optical telescope.
Wishing you
all a TASTY and HAPPY THANKSGIVING!!
Regards,
Robert
www.guidetothecosmos.com
Author of "Everyone's
Guide to Atoms, Einstein, and the Universe"
and "Can
Life Be Merely An Accident?"
|
|