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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