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?"
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