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Black Hole Search Begins In Australian Outback 68

Posted by timothy from the they-are-looking-up-not-around dept.
Sandeater writes: "BBC news is reporting that an new telescope has just been completed to search out black holes from the Australian outback. The astronomers using the telescope will be looking for huge black holes at the centres of galaxies, as well as seeing how they evolve. The Cangaroo II will be offically opened tomorrow. The BBC link can be found here."
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Black Hole Search Begins In Australian Outback More

Black Hole Search Begins In Australian Outback

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  • Re:wouldnt it have... (Score:1)

    by Anonymous Coward
    I don't think Gamma rays are deflected/attenuated so much by the earths athmosphere. Besides, the bdgets have no common measure.
  • ...given that this is only place were you can actually experience gravitation collapsing in a hole. A wombat hole to be precise.

    I certainly hope outer space black holes aren't giant wombat nests, or the research team might find themselves in deep trouble.

    Film at 11.
  • Yeah, and how many fingerpr ints [adelaide.edu.au] did these yahoos put all over that mirror? ;>
  • They never had any to begin with!
  • Ummm, The so-called "sock in the dryer phenomenon" is in fact Zaphod Beeblebrox extending his biro business.

  • Thats the biggest black hole this side of Andromeda!
  • That is a good thing to see. Actually taking shots at existing theories to see if they will hold water. I do hope they are able to prove that there is enough matter to eventually pull the universe back into the Gnab Gib. It seems lonely and pointless considering the other theory, that the universe will just consider to expand and cool, eventually fading away. Just remember, they expect large scale proton decay in about 30 billion years. That's pretty much the time limit we have. If the universe doesn't start to pull itself together by then, it's just going to fade to black.
  • That is, of course, dependent on two things. The first is that we HAVE made decent estimates of the amount of mass in galaxies, and second, that our understanding of gravity is correct. Not that I'm completely discounting the theory of dark matter -- I believe it exists, even though I have very limited knowledge in this area -- but I'm just pointing out that things the scientific community seems so sure about today may be completely disproven tomorrow, and it wouldn't upset me much at all.
  • I think they'd have more luck building a big telescope and looking into outer space rather than going walkabout...
  • Why dose this dark matter exist ? Because without it the Big Bang is called into question.

    Actaully, Dark matter is absolutely not required for the Big Bang to have happened.

    The issue is more serious than that. Without it, the whole of Newtonian Mechanics is called into question. Okay, so we already know that in the quantum and relativistic limits, Newtonian mechanics no longer holds. However, on galactic scales, Newtonian mechanics is supposed to hold true.

    This is not what is being observed. The problem is connected to the speed of rotation of stellar objects. Now, I admit that it's been a couple of years since I last studied Astrophysics, so I'm a little rusty, but IIRC the rotational speed of objects "orbiting" our galaxy is too high to be explained by the amount of visible matter. (There is more to it than that, but like I said, it's been a couple of years...)

    For more info, hit your local library, or try google [google.com]

    Cheers,

    Tim
  • It's an interesting idea, but although EM is very much stronger than gravity, we are talking about an awful lot of mass here.

    I vaguely remember that we did a rough calculation on the charge that the Earth would have to have in order to produce as strong an EM force as its gravitational one. I don't remember the numbers (or have time to do it now, but it's pretty easy), but the charge required was huge.

    You are right in saying that the effect would be indistinguishable, but I do think that the amount of charge that would be required almost certainly rules it out as an explanation.

    (You've got me thinking though - gonna have to sit down and work it out when I get home :-) )

    Cheers,

    Tim
  • Actually, I'd be willing to venture the southern skies might be more mapped than the northern skies.

    1. Less light pollution (seperated cities)
    2. Less Air pollution (from less population)
    3. Milky way is viewed better from southern hemisphere. (True - don't flame me - check it out)
    4. No northern lights (okay - this one is just a joke)

    --
    A great story I know about Northern & Southern Hempisphere astronomers is some Northern ones coming to the Australian Outback (the Alice) to look at the milky way. They go out one night with thge Southern guys, and they all look up before setting up their telescopes and such. The northern ones says it's a shame about the weather, and how they'll have to wait for the clouds to clear. The southern ones have to explain to them that those "clouds" are infact the milky way.

    Anyway, moral of the story is that The milky way is bright and visible in Australia. If you're looking for dark matter in the Galaxy - wouldn't you check out your own galaxy first?
  • When the huge-galactic black-hole is found, the astronomers are going to say to the Australian outback searchers: That's not a black hole. THIS is a black hole.
    --
    Have Exchange users? Want to run Linux? Can't afford OpenMail?
  • Now, I don't mean to be dispairaging of our readers of the Aussie persuasion. I've read a lot of truly excellent posts by those from Oz. But, from what I've heard, if they're looking for black holes, you couldn't look in a more likely place than the Aussie Outback. I mean, there's practically nothing there, and the few inhabitants that are there are so dense that their gravity well even managed to suck down SkyLab several years back.
  • This is another example of it. Notice how BBC news is reporting it. Don't the Australians have their own news service? Would the BBC even care if something noteworthy happened in any of the other commonwealth countries?

    Australian News services don't seem to care about science much. We (the viewing audience) are only interested in sport apparently. For a 30min news program, there will be 15 mins of sport.

    There are a few science programs running around. Nearly all started life on the ABC (Australian Broadcasting Corperation), and were purchased by the other TV stations when found to be successful. They were generally modified to suit the new stations ideals, and usually failed within a year or two.

    Science does not get a lot of press over here. It's a pity really. There is lots of good stuff going on.

  • i should know
    i live in redfern
    :]
  • Have a rouge crew of aussie geeks taking over slashdot?..Or maybe just invested some downunder dollars in andover.net. Has anyone else has noticed, Count them - there are 3 Australian related post's on slashdot at the moment. We have gotten this much publicity since the dingo killed a baby a few years back. Anyways Australia has already found the black hole its called burgatronics
  • Maybe they can find the one that sucked in Yahoo Serious and Paul Hogan's careers
  • Jim Pooley? Where's O'Malley? :)
    Bring on the sprouts!

    Strong data typing is for those with weak minds.

  • Yahoo Serious had a career? I must have blinked.

  • Well, we don't have a real clear view to the center of our own galaxy. There are lots of dust clouds and other stars and general Milky Way stuff in the way.

  • One thing Ive wondered about is why the rotation of galaxies cannot be explained by something else than gravity, say by electromagnetism. Since electromagnetism is some 10^40 times stronger than gravity you wouldnt need such an incredible charge (well, relatively speaking) to influence the rotation curve of a galaxy as much as a huge amount of matter would by gravity. Also, EM diminishes by the distance squared too, so the curve would look identical.

    Say the supermassive black hole in the center of the Milky Way is very strongly charged (BH:s can have charge), say positively. Also say the stars in the galaxy are negatively charged. Wouldnt they then orbit at a faster rate than with no charge?

    /Dervak

  • Forgot this: In my mind it wuld be easy for a black hole to become positively charged. The accretion disk gets heated to very high temperatures, ionizing the gas to a plasma. When the plasma is sucked in by the BH a fraction is shot out by electomagnetic fields of incredible strength, in both directions along the rotation axis of the BH in relativistic jets.

    Since electrons are some 1800 times lighter than protons, but they have as large (but opposite) charge, it seems it would be much more likely that electrons escape in the jets than protons, resulting in a net positive charge for the BH.

    /Dervak

  • The technique they're using for Cangaroo is in fact based on the Whipple experiment and uses the same technique for distinguishing between gamma rays from blazars (where on Earth did that name come from :) ) and cosmic rays, although I'm not all that certain of the exact details of the process.

  • Hey hey... nice tieing in the fart jokes from they survey there!

    greets from #linux, greyfox!
  • It's official...that's the dumbest forced acronym name I've ever seen in my life.
  • AAARRGGHH! Too... many... jokes.... Must... preserve... KARMA....

    ....

  • The telescope is called Cangaroo. :)

    It stands for Collaboration of Australia and Nippon for a Gamma Ray Observatory in the Outback. (Nippon == Japan, the two countries are collaborating on the project.)

    The outback strikes me as a good place to have a telescope. Certainly the surroundings will be sufficiently dark, with no lights from nearby civilization.

  • I think you'll find there is quite a bit of coverage on BBC news about the little spat that's currently going on in Zimbabwe, as well as Sierra Leone. Also, in the last few weeks, there have been (to the best of my recollection) stories on the BBC about the following commonwealth countries:

    Bahamas
    Bangladesh
    Cameroon
    Canada
    Cyprus
    Ghana
    India
    Jamaica
    Kenya
    Malaysia
    Mozambique
    New Zealand
    Nigeria
    Pakistan
    Singapore
    Uganda
  • Isn't this the same multi-phase project that was recently reported to be at risk of being cancelled, due to interference caused by newly installed security lights at Woomera (the former hush-hush satellite monitoring facility, more recently used as a detention centre for illegal boat-people)?

    The new security lights were installed - after several of the boat-people escaped from the detention centre - in a bid to preclude for future escape-attempts.

    It seems that light from the security lights makes this bush location too much like any urban centre... defeating the purpose of being out there, i.e. so far from the bright cities...

    A decision is due shortly on whether to procede or not with an extention of the project...

  • Sandeater writes: "BBC news is reporting that an new telescope has just been completed to search out black holes from the Australian outback.
    Austrailia has black holes?! How many? When did they discovere black holes there? How come they haven't swallowed up the continent? Or will they? hey, I didn't write it, I just read it.

    ~svoboda

  • Another advantage is that free, naturally occurring oxygen you get on Earth. I couldn't hold my breath nearly as long as those guys on the Hubble.

    I met my new friend Jimbo at the bar just the other night, and he was one of the guys who worked on the telescope up in space. He had to quit after he got sick of hilding his breath for a couple of years. He says it was hard work because it was really hot in space, and the sun was BRIGHT GREEN. The sky soaks up the blue and makes the sun look yellow. I like my friend Jimbo -- he's so smart.

    --

  • Any science related to the subject of "creation" requires a certain amount of faith and a great deal of patience. Theologians haven't gotten too far over the past few millennia, but astronomers have (comparatively) made significantly more progress in just a few centuries!

    --

  • Oh great! Now I have to clean coke off my keyboard!

  • You know, if you read regularly, you would see that there is PLENTY of other science areas. One of my favorite links (of course) is Fun with Hookes' Law. Plus, there is LOTS of biology / genetics up quite frequently. If you're not interested in astronomy, then DON'T READ THAT STUFF. Just like I don't read stuff that I'm not interested in. It's THAT easy.
  • Why dose this dark matter exist ? Because without it the Big Bang is called into question. Of course the BB can't be wrong. We have built whole curriculums around this. It MUST be true.

    The big bang theory isn't the only reason why there must be dark matter.

    For example, it turns out that galaxies as we observe them could not be stable, if they were only composed of the visible stars.

    I've heard of some other points that make dark matter necessary, but unfortunately, I can't think of any at the moment.

  • I wish them all the best, but in the outback?

    I suppose there's no lights out there except for spotlights on the kangaroo shooter's van.

    I'm from australia and i know what is out there... pretty much nothing. There was a tourist about 2 - 3 years ago that got lost out there, in the blazing heat this japanese tourist sat, while his motorbike (which had run out of fuel) rested quietly in the shade of a shrub. For 3 days he sat in the sun waiting for his motorbike and him to be rescued.

    I really hope that they use common sense and dont get stuck or anything.

    Oh and one more thing, there is a guy out in the desert somewhere taking a 'spiritual journey' in a red fire truck, he's been gone for a few weeks and no one's seen or heard from him since he left.

    I am dead serious when i say that. Perhaps they could spot him as well.

  • Canadian actors don't have time for British Television

    They are too busy taking over the U.S.

  • >Had it crossed these peoples minds that Woomera is a MISSILE RANGE?!?!?!

    Yes.

    "Sited on a former rocket range at Woomera [...]"
  • Firstly if teh last 5 posts 3 have involved australia, 2 of these however you would hope would be interesting to most /. readers, ie a new way of observing space (i know it isn't in america but it does still exist) and the other one is about what someone in australia wrote, how this renders it only interesting to australians i am not sure. What do you want /. the American version, and /. for Greater America (read the rest of the world)
  • You said, "Why does this dark matter exist?". The answer is not that the big bang's validity rests on the potential existence of dark matter. Rather, that without dark matter, be it MACHOs or WIMPs or baryonic particles, the universe would not be expanding at its current rate. If all that we see is all there is, then there isn't enough matter in the universe to slow it down to it's current rate of expansion. This the consensus within the field of cosmology today. Tomorrow things cound change, and yes, dark matter could be disproven. But for now all evidence points to its existence... Dark matter is real... just really dark.
  • Ah, but do the disclaimers apply to the disclaimers? If not, then if a disclaimer should break down, you could be sued! :)
  • Somehow I get the feeling that Astronomers are working against the grain of normal science right now. I.e. they theorize that something exists because it would have to in order for some other theory to be true. Then they go off and do whatever it takes to prove it's existence.

    When they fail to achieve this they just try again.

    Eventually. some theories will have to be abandoned and others that were previously called laughable are found to be true. This whole "dark matter" thing is an example. I.e. there is a vast amount of matter in the universe that doesn't show up on any of the scans. In fact, vastly more than dose show up or can be accounted for in interstellar gas and black holes etc...

    Why dose this dark matter exist ? Because without it the Big Bang is called into question. Of course the BB can't be wrong. We have built whole curriculums around this. It MUST be true.

    Other scientists are quicker to throw away used theories. Maybe I am being too harsh. After all it's hard to sit in one far corner of the universe and see what the whole looks like.
  • Those guys are still working! Yahoo's website is www.yahoo.com, and Paul Hogan was working on a show called Hogan's Heroes.

  • The theory of what the dark matter actually is that I seem to like the most is that its dead white dwarf stars that have cooled beyond the limit which is visible by today's telescopes. This would mean that the vast majority of stars are therefore small whitedwarf stars, and that there's a whole hell of a lot of them.
    WIMPs, MACHOs, etc. they're just patch work. Neat ideas with absolutely no backup evidence.
    White Dwarves on the other hand have more potential. I wish I had a link to some info... I'll need to find one.
  • Having something up in space will mean it is not going be hearing all the crap from ground based transmitters - or a lot less of it anyway. Of course, being in the part of OZ they are in, I really don't think there is going to be much of a problem with that. It is pretty desolate there.

    An example of this is the boundary around the telescope at Green Bank. I know Part 97 of the FCC rules states that you have to have permission to set up amateur radio beacons if you are near it (check the ARRL Website [arrl.org] and do a search on 'Green Bank'). I am not sure about some of the other radio services. The reason is because of the interference generated by transmitters.

    Radio receivers can cause lots of noise also if they are not properly designed, btw.

  • Huh? (Score:2)

    by doogieh ( 37062 )
    Black holes come from the Australian Outback? Well, at least they're exporting something these days. Too bad the market for black holes, well, really sucks.

    Be careful in Perth. Its near the Schwartzchild radius.
  • It's amazing! First you think that Australia has been completely discovered and explored, now you find out that they're discovering blackholes in the outback!

    What? What's that you say? Oh. I see. Maybe I should wake up more thuroughly before posting.

    -------
    CAIMLAS

  • How are they going to find a black hole now that all their Athlons have been tampered with? Sounds like sabotage to me...

    -JD
  • Why all the rush to study remote galaxies as such, why not turn our eyes towards the center of our own galaxy? Is it such that our galaxy doesn't fit their parameters that have been postulated to contain a black hole?

    I say point those bad boys to the center of the milky way and see what beats in the heart of all that matter. Even if there is no black holes to be found I would surely help determine which galaxies would and wouldn't contain a black hole. Thus raising the chance of finding a black hole in a remote galaxy.

  • 10) Your grocer's freezer.

    9) My first girlfriend's [CENSORED.] I mean, it seemed to suck everything in...

    8) California. Don't all the ... holes come from there?

    7) The press coverage surrounding Elian will soon achieve critial mass and implode.

    6) What the hell is that space between Letterman's teeth, anyway?

    5) The fox sunday night line up. Between Futurama and the Simpsons and between the Simpsons and the X files.

    4) Hey Terence! How'd you like to look for black holes [FART]! Ooo! You farted on my head! Ha ha ha ha ha!

    3) The space between a first poster's ears.

    2) Any song in the top 40.

    And the number 1 place to look for black holes:

    1) The Microsoft E-mail backups.

  • I mean - i understand that every techie/geek here
    has to be brought up on Star Treck and all, so
    let it be here. But how did it get to be the
    only science field getting any coverage on /.?

    It has little to do with computers, as for
    "stuff that matters" - i am sure , say automotive
    news or medical science, matter a lot to great
    many here. And the list can go on.

    So i'd say either discuss them *all* or get the
    damn astronomy out of here. Personal tastes of
    site founders should not be a guiding line in
    what is posted for a site that is used and trusted
    by as many people as this one.

  • While I applaud the ingenuity of checking in Australia for black holes, I think they may wish to start with outer space, instead. Still, all those weird-ass animals have to be coming from somewhere.

  • For all of you who are not that familiar with Cerenkov radiation (that includes me), here is the Encyclo pedia Britannica page [britannica.com] for it.

  • Having something in space will mean it is not going to be hearing all the crap from ground based transmitters

    The telescope is supposed to detect gamma rays, so I don't see why there should be any problems with ground based transmitters.

    According to the article, the telescope doesn't even detect the gamma rays directly, but only detects secondary radiation, that is emmitted, when the gamma rays hit the atmosphere, so sending it into space would be couterproductive.

    It would probably be impossible to build a telescope of equivalent angular resolution in space without spending a few billion dollars, about thousand times the budget of this one.

  • Couldn't they just rent that Disney Sci-Fi flick instead of going to Austrailia to find a copy? Sheesh...
  • According to the article, the telescope scans for gamma waves. These aren't suject to atmospheric effects the way light is. This means they can build a much bigger telescope, which is considerably easier to maintain, for a lot less money.

  • I'm not surprised... (Score:3)

    by pb ( 1020 ) on Monday May 08, 2000 @04:10AM (#1085856)
    Once you get past the event horizon, it *does* look suspiciously like Australia. I got there through L-space once, purely by accident. There I was, in the back of a Barnes & Noble, browsing the Terry Pratchett section, and before I knew it, BLAM! There I was in a rather demented futuristic Australian Outback. I know it was a black hole because they worshipped people from the movie. Needless to say, I found the nearest local bookseller, and got back home before dinner got cold.

    It's probably the space time flux caused by that wandering entity who likes to add on bits to worlds that look like Australia retroactively that causes the black holes in the first place. Just another case of Science imitating Science Fiction...
    ---
    pb Reply or e-mail; don't vaguely moderate [ncsu.edu].

  • Black Holes (Score:3)

    by jd ( 1658 ) <imipak@yahoGINSBERGo.com minus poet> on Monday May 08, 2000 @04:55AM (#1085857) Homepage Journal
    I think the Australians have come up with an ingenious scheme to observe Black Holes. Personally, I think they'd have more success looking into the ears of politicians.

    IMHO, Australia is a brilliant place for such observations. The sky is crystal-clear (relative to anywhere in the northern hemisphere) and there is a lot of empty space to build a telescope without burger bars, shopping malls and strip joints surrounding it within a week.

    I've often wondered if Australia might be a good place for SETI, for the same reason. Sod the 1Km array! It would be practical to build a 5 mile array Down Under. (A 5 mile array would give you an image 18 pixels x 18 pixels of an Earth-sized planet, 1 Astronomical Unit from a Sol-like star, up to 100 light-years away. That would be enough resolution to check the atmosphere, determine the climate and look for radio leakage rather than deliberate signals.)

  • Re:Why it's ground based (Score:3)

    by Conor ( 2745 ) on Monday May 08, 2000 @05:05AM (#1085858)
    Good reply, you obviously know what you're talking about. However the main reason you use a ground based telescope is that you require a detector the size of a football pitch to see enough gamma rays of this energy to say anything useful. Thus it's impractical to launch one into space. Instead you use the atmosphere as your detector. Space based telescopes exist already which see lower energy gamma radiation from blazars, such as CGRO [nasa.gov]. I should also mention the experiment which discovered very high energy gamma rays from blazars, using the Cerenkov technique: The Whipple experiment [arizona.edu] (a blatant plug for my own PhD experiment!).

  • Re:wouldnt it have... (Score:3)

    by EricWright ( 16803 ) on Monday May 08, 2000 @03:48AM (#1085859) Journal
    The purpose of orbiting telescopes is to avoid atmospheric absorption/distortion of the signal. Earth's atmosphere is opaque to many bands of IR and UV lights corresponding to atomic and molecular transition lines. Of course, atmospheric turbulence can wreak havoc with visible light. However, at the high X-ray energies they are looking at, the atmosphere is practiaclly transparent.

    Also, the cost of an orbiting satellite is significantly higher than that of a ground based instrument, and with the booming Australian and Japanese space programs, they would have had to shell out more bucks to NASA or ESA to launch the thing.

    Eric

  • Advantages of an atmosphere.. (Score:3)

    by MosesJones ( 55544 ) on Monday May 08, 2000 @04:07AM (#1085860) Homepage

    The interesting thing I found about this is that unlike the reasoning behind Hubble (the atmosphere distorts light so get outside it) the Cangaroo II telescopes will use that very distortion to view the black holes.

    I'd assume that the Southern Skies are a lot less mapped than their Northern cousins given the dearth of countries south of the equator.

    But if they'd really wanted to go to a place where the atmosphere distorts the view then a Cafe Bar in Amsterdam would be their best bet :-)

  • Re:You won't find them there. (Score:3)

    by MosesJones ( 55544 ) on Monday May 08, 2000 @04:20AM (#1085861) Homepage
    Umm so modern Astro-physics is all bollocks then.

    Astro physics is one area where they just love to throw away theories and start with new ones. Black Holes have been postulated and the postulations found to be correct. The problem is viewing something that by definition doesn't emit light because its as dense as a Christian Coalition convention.

    A lot of Astro-physicists would just love to be the one who writes the seminal paper

    "The big bang is bollocks, the Universe is created from paper clips and buttons that disappear down the backs of sofas"

    The aim of scientists is to be respected, and respect is earnt by proving others right beyond any doubt or best of all proving as many people wrong as possible.

  • Re:You won't find them there. (Score:3)

    by spiralx ( 97066 ) on Monday May 08, 2000 @05:27AM (#1085862)

    Since electromagnetism is some 10^40 times stronger than gravity you wouldnt need such an incredible charge (well, relatively speaking) to influence the rotation curve of a galaxy as much as a huge amount of matter would by gravity. Also, EM diminishes by the distance squared too, so the curve would look identical.

    Well, the potential energy of the EM force would then be added to the gravitational PE, making the required rotational kinetic energy less so the galaxy wouldn't rotate so fast.

    Or alternatively for the same rotational velocity and kinetic energy the gravitational contribution to the potential energy would be lowered by the EM contribution, hence less mass is required.

    So sure in theory that could be an explanaition, but how on Earth would a star be negatively charged? That would imply it had an excess of electrons over protons, and since both come almost exclusively from the ionization of hydrogen where would this massive excess (and it would have to be pretty big to have a noticeable effect) come from?

    And again, since black holes form from stars where would their supposed positive charge come from? I personally can't think of any mechanism that would cause this sort of distinct charge difference between stellar objects. And while I'm not up on all the details, I'm pretty sure that you could tell whether a star was negatively charged through spectroscopy or some other technique.

  • It should be noted that this telescope will actually search for Active Galactic Nuclei (AGN), of which supermassive black holes play a small, but important role. There is alot of other really interesting physics here though! For a cool picture of an AGN, click here [nasa.gov]. For more info, click here [nasa.gov].

  • Black hole (Score:3)

    by BrianW ( 180468 ) on Monday May 08, 2000 @03:40AM (#1085864)
    Do you think they'll find the black hole that sucked away all the talent of Australian soap stars?

  • Dark matter is necessary for another reason (Score:4)

    by spiralx ( 97066 ) on Monday May 08, 2000 @04:20AM (#1085865)

    Why dose this dark matter exist ? Because without it the Big Bang is called into question. Of course the BB can't be wrong. We have built whole curriculums around this. It MUST be true.

    You forget a possibly more important reason for dark matter to exist - in order to explain why galaxies are stable. In order for a stable, rotating galaxy to exist it must satisfy the Virial Theorem which is 2V+T=0 (I think), where V is the gravitational potential energy and T the rotational kinetic energy.

    Given what we know from observations of both our own and other galaxies we can make reasonable estimates of both of these figures, using average stellar masses, the no. of stars/galaxy, the radius of a galaxy and its rotational period. What we get from these numbers is that there is only 10% of the necessary mass in the galaxies we see for them to be stable.

    If there was no dark matter then the stars within galaxies wouldn't be gravitationally bound and would be flung out by the galaxy's rotation. But since we can look out to the Universe and see stable galaxies of many different ages we have to conclude that there is extra mass present in galaxies that we simply can't see. Each galaxy is embedded in a huge disc of dark matter, and without it there would be no galaxy.

  • Why it's ground based (Score:5)

    by spiralx ( 97066 ) on Monday May 08, 2000 @04:10AM (#1085866)

    Well, for one, the cost of a ground based installation is much less than a satellite, but that's the obvious answer :)

    What they're doing is looking for the Cerenkov radiation produced when a high energy gamma ray from the "blazar" produced by a black hole hits the upper atmosphere. Cerenkov radiation is the product of electron/positron pair creation and bremmstrahlung and consists of relativistic particles which travel at velocities faster than the local speed of light. This results in the production of Cerenkov radiation in the blue part of the visible spectrum, which is what the telescopes actually detect.

    However there is a far greater amount of Cerenkov radiation from normal cosmic ray incidents than there is from gamma rays produced in blazars. Since the cosmic ray particles are charged (they are usually protons) whereas the gamma rays aren't, they can be distinguished by whether they curve in the galactic magnetic field.

    Anyway, since this is a proven technique, there's really no need for a space-based detector as of yet.

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