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03/07/2007
Major Swallowing and Spitting
We’re back home in New Jersey after a bumpy flight over the
disastrous weather in the South last week. While my wife had
the misfortune of sitting with a mother and her obnoxious 7-year-
old daughter, across the aisle I had a pleasant three hours
chatting with Julie and Sam, an interesting couple traveling back
to their home in Scotland. I think there were also two stowaways
on our flight and they must have followed us home from the
airport. Specifically, I saw two robins yesterday that clearly had
arrived too early, considering the bitter cold weather with wind
chills in the –5 to –15 degrees below zero Fahrenheit! And this
morning we have a couple inches of snow to contend with. You
may recall that while on Marco Island I wrote about residents in
Southwest Florida being upset about robins from up here in the
north pooping pepper tree seeds down there. Perhaps the robins I
saw were escaping the ire of those Floridians?
The temperature was much hotter Sunday in the Birchwood
Manor, where we attended the Pee Wee Russell Memorial
Stomp. The Stomp was a 5-hour jazz festival under the auspices
of the New Jersey Jazz Society and the joint was really jumping.
My wife and I anticipated leaving after 2 or 3 hours but we
stayed for the whole afternoon. Jazz fans may know of the
closing group, New York-based Vince Giordano and the
Nighthawks. Many years ago, my wife and I served wine and
cheese at jazz concerts sponsored by our local art center. There
we got to meet such jazz greats as Doc Cheatham, Dick
Wellstood, Bucky and John Pizzarelli, Warren Vache, Milt
Hinton and others. On Sunday, it was good to see that many of
the musicians were young, boding well for the preservation and
propagation of this truly American music form.
On Marco Island, I wrote mostly about my beach walks, the flora
and fauna and some environmental issues of most concern down
in Florida. While there, I read an article by Wallace Tucker,
Harvey Tananbaum and Andrew Fabian in the March issue of
Scientific American on a subject considerably wider in scope.
The title of the article, “Black Hole Blowback”, suggests that I’m
again about to indulge my passion for writing occasionally about
astronomical subjects that boggle my mind and are beyond my
feeble brain’s ability to comprehend. Tucker and Tananbaum are
with the Chandra X-ray center while Fabian is a professor at the
University of Cambridge. Among them, they’ve published
hundreds of papers and some books on galaxy clusters, black
holes, dark matter and the like. They obviously know their stuff.
I was intrigued by their opening sentence describing the universe
as being something like our U.S. interstate highway system, with
its freeways spanning relatively open spaces and intersecting
with other freeways. The freeways are akin to the filaments of
galaxies that thread their way through our universe, occasionally
crossing other filaments of galaxies. These intersections are the
sites of clusters of galaxies, which the authors liken to cosmic
megacities.
These galaxy clusters are humongous and may contain a
thousand or so galaxies. Gravity holds the galaxies in the cluster,
where they move about, tugged this way and that way by all
those neighboring galaxies. In such a chaotic situation, it’s not
surprising that galaxies collide with other galaxies, often forming
larger galaxies. Indeed, at the center of a galaxy cluster there is
likely to be a larger than normal galaxy and at the center of this
extra large galaxy is likely to be an extra large black hole.
We’ve discussed before how a black hole forms when a star
significantly larger than our sun runs out of hydrogen fuel,
contracts, then explodes shedding its outer layers, then contracts
to a drastically smaller size forming a black hole. The force of
gravity of a black hole is so great that even light cannot escape
its clutches and the black hole gobbles up anything that gets
close enough to it. Galaxies typically have a black hole at their
centers. If a galaxy collides with another galaxy, chances are the
two black holes will gobble up each other to make one really
massive black hole. Black holes with masses equivalent to
hundreds of millions of suns are not uncommon.
OK, suppose we have at the center of a cluster one of these super
large galaxies with a super massive black hole at the galaxy’s
center. Anything that comes near the black hole will get gobbled
up, right? WRONG! A black hole not only swallows stuff, it
can also spit it out! At least that’s the way it might look to an
outside observer. That observer might also be startled to find the
black hole appear to be blowing gigantic bubbles! Of course, the
observer can’t actually see the black hole itself – remember, we
said light cannot get out of a black hole.
How does a black hole spit? As it gobbles up stuff from its
surroundings it begins to spin. The infalling stuff is spinning and
when the black hole swallows it, the hole spins faster. A
supermassive black hole’s outer surface may end up spinning
very fast, even at almost the speed of light. The spinning creates
magnetic fields extending outside the black hole. These
magnetic fields act on some of the stuff falling towards the black
hole as a catapult flinging some of the material back out into
space in the form of two super energetic jets emerging from
opposite poles of the black hole.
Strictly speaking, the black hole didn’t spit those jets of material
out into space. The stuff in the jets never made it into the black
hole (more exactly, beyond the hole’s event horizon for you
purists out there); the field of the spinning hole deflected it. The
article states that for a very large black hole as much as a fourth
of the incoming stuff may be deflected out into the jets. These
are powerful jets, so powerful that, shooting out into space away
from the black hole, the two jets form gigantic bubbles of hot
gas. The energy of the gas in these bubbles is so large that it
compares with the energy released in millions or even billions of
supernovae.
When a supernova appears it can outshine the entire galaxy in
which it resides! So, these bubbles are truly loaded with energy
and furthermore are, as I said, gigantic. A galaxy cluster may be
some 10 million light-years in diameter (a light-year is about 6
trillion miles). The article contains one picture of an eruption
that has been going on for 100 million years from a central
galaxy in the cluster MS 0735. Bubbles of hot gas spawned by
the jets from this eruption are a few hundred thousand light-years
in diameter and their outer reaches extend out almost a million
light-years in both directions from the central galaxy containing
the parent black hole. The influence of this one supermassive
black hole extends way beyond its own galaxy.
There’s a lot more to the jet story but I’m having trouble
comprehending the enormity of all this. I’m wondering if we
Milky Way residents are in a cluster containing a supermassive
black hole that may shoot a jet in our direction. Hopefully, none
of us, or our foreseeable descendants, will have to experience
such a jet or bubble headed this way! Now, in contrast to our hot
topic, it’s out into our frigid 19-degree weather to clear the snow
off our sidewalk – wish I were back on Marco Island!
Allen F. Bortrum
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