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Science

Bright Star Getting Brighter 133

Posted by Hemos from the first-star-i-see-tonight dept.
jwhyche writes "Just what the heck is Eta Carinae doing? Well astronomers are not quite sure. After being one of the brightest stars in the Southern sky it dimmed for a few decades. Now it's back, emiting five time the energy of the sun, and is right next door. So, how big is a hypernova explosion anyways? Big boom anyone? "
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Bright Star Getting Brighter

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  • Very nice recap.

    A couple minor points:

    1) there is not really any evidence that supernovae typically result in black holes. While theory does *predict* black holes, they are notoriously hard to detect. In fact most theories predict neutron stars and many have been been found in supernova remnants, including the Crab Pulsar in the remnant of the 1054 AD supernova.

    2) LBVs are thought to be of order 70-100 solar masses, as opposed to the 30 or 40 suggested.
  • That's kind of tough if they don't know where our doorstep is.

    You may then think that "if they know how to create a huge burst of gamma radiation, then they must be advanced enough to find us", but I say nay, not neccessarily. They may have the means to spray a little lighter fluid on a nearby sun without killing themselves, (no small feat, I admit), but they may well be no further along than us in terms of actual interstellar travel and communications.

    Remember the soldier's curse about lighting more than 2 smokes with a single match? Crouch in a field on a moonless night and no one can see you. Now light a single match...

    I admire the work of SETI, but I think our time would be better spent drawing attention to ourselves in conjunction with scanning the heavens at random.

    I really don't think 'THEY' have seen us. When they do, we'll hear about it, for better or worse.



  • Perhaps you know of a way to transmit data faster than the speed of light. :)

    This is what confuses me about this theory:

    1) Obviously they wouldn't do this to their own star, it would be too risky. They'd have to go to another solar system to do this.

    2) They couldn't do it to a star that was too close for the same reason. They'd have to go a good distance, just in case they completely screwed up and caused a hypernova. They don't want to wipe out their civilization.

    3) Why would they travel the many many light years it would take just to send a message no one is going to receive for centuries and probably won't understand, anyway, when they get it?

    I suppose that if they have the capability of manipulating a star, they could conceivably have faster than light travel IF faster than light travel is possible, which wouldn't make the trip so bad.

    Of course I'm also assuming that they can't manipulate the star from a great distance also, which isn't neccessarily so.

    Pretty much, this whole post is a waste, then.


    -

  • Re:the Death Star (Score:1)

    by Anonymous Coward
    The schwartschild radius of the black hole would be roughly that of the initial radius of the star. Don't worry about it. The gravitational effects of the black hole on us, would be the same as the star's.
  • would a black hole that close have effects on us?
  • If only it were that simple. There is a SETI theory that the reason the galaxy is not full of migrating life forms is because life was being killed earlier.

    The "resetting the clock" theory is that the young Milky Way galaxy was being sterilized by stellar radiation bursts about every 200 million years. Any life was destroyed. We hope the galaxy is old enough now that it won't happen again too soon. Of course, we're not a colony planet already because other life began at around the same time as us, so has not had time to spread throughout the galaxy already.

    As long as we can live through whatever it does, now that the astronomers have noticed it they'll be getting a good show. Even becoming a quiet star will be interesting.

  • Also, the so called "homunculus", the dust cloud that surrounds eta carina, points to what youm were saying
  • Anthropo-centricity! They were sending news broadcasts to their neear-neghbors the Clongdinthers, we just happened to get the message as well.

  • # If Eta Carinae becomes a black hole, would it
    # be the closest known black hole, or does
    # anyone know of one that is closer to us?

    It would be the closest known black hole. (Unless Sagittarius A, at the center of the Milky Way, is closer??)

    And we'd get a big radiation blast, due to its proximity. Esp. if it goes hypernova! Unfortunately, I don't think we're quite sure what causes hypernovae, so its hard to say whether this is a possibility.

  • If I remember correctly, a black hole will add the things it sucks in to its mass, thus increasing it's gravitational pull. It would take a pretty unimaginable amount of mass in order to have an effect on us though. We (humans that is) probably won't be around long enough for that to happen anyway. Something else will likely kill most or all of us off long before we have to worry about black holes. Right now they are just a curiosity and are mainly interesting due to the fact that they are the most efficient producer of energy in the known universe.

    I'm not an astronomer (not even an amateur), so I'm sure someone will correct whatever I screwed up :)

  • Posted by FascDot Killed My Previous Use:

    So you won't be killed in the initial burst. Great! You'll just die a slow painful death in the aftermath.


    --
    "Please remember that how you say something is often more important than what you say." - Rob Malda
  • Someone (I forget who) once theorized that the best way for aliens to contact us would be to modulate heavenly phenomenon in such a way that we would take note of it. For one, seeing as how we are constantly observing astonomical phenomenon, this would be a good way for the aliens to improve our chances of actually seeing the message, and two, we'd probably notice any glaring anomalies. So, Could this be the one? The SETI guys should sic their signal processing algorithms on the spectrum coming from this star.


  • Where's the Immodium P38 Space Modulator when you need it?

    Obviously the aliens think we have a case of intergalactic diarrhea if they're launching Immodium at us.

    Okay, tag this at "-1" and move on...
  • just pray the message isn't encrypted.
  • Well... Astronomy is a difficult system..

    I'm sure some of you have tred debugging a system via the internet and wished you could get your hands on teh machien to figure it out.

    In astronomy we only see things from one angle.

    Anyway... we don't get enough money to do all the research we';d like to - if you want answers you need to get the Governments to give us the resources to get them ;-)

  • Obi Wan: That's not a star, it's a space station.
    Han: I have a bad feeling about this.
    Obi Wan: Dang, that was my line.
  • Posted by FascDot Killed My Previous Use:

    Visible light is kind of a narrow band. Why not include all EM?

    Better yet, why not use tachyons? That way we can break the speed barrier. True, it may not be possible to indicate more than "LOOK HERE", but isn't that enough?
    --
    "Please remember that how you say something is often more important than what you say." - Rob Malda
  • Pretty close. Basically, a black hole, from far enough away, affects you just like any other object of the same mass. If the sun turned into a black hole right now, it's get dark and cold and we'd have other problems after a while but our orbit wouldn't be affected and we wouldn't have to worry about getting "sucked in".

    Basically, if Eta Carinae did turn into a black hole, we would be trading a visible 100+ solar mass for an invisible 100+ solar mass. (Okay, we'd see the accretion disk, but that's chickenfeed.)
  • On your everday life? Not much, probably...

    It will however give the scientists a better view at a Black Hole. They might be able to study it and find new stuff out about it.

    But don't worry, it's not going to gobble us up.

  • The lower limit for a stellar mass black hole is only about 3 solar masses. Eta Carinae is about 100 solar masses. This doesn't mean every star over 3 solar masses will become a black hole. It just means if what is left after the super(or hyper)nova is bigger than 3 solar masses, the remnant will collapse into a black hole.
  • Nuetrinos don't have any effect on the human body (for the same reason rock won't protect you)they just don't interact with matter much at all.
    --
  • It's been a while since I read up on this type of thing, but I seem to remember reading that as more stuff gets pulled into the black hole its radius increases in size. Is the schwartschild radius the actual "boundary" of the black hole, or is it the radius that feels the effects of the gravity? Well I guess there isn't really a limit on the second one... I don't know if any of what I said is correct. But I don't think the original guy was asking if the black hole would be "big" enough to engulf us, I think he was asking if its gravity would be enough to pull us in. And since the black hole will grow, I guess it's conceivable that it will someday pull us in.

    But like I said, I don't know what I'm talking about.

    -----BEGIN ANNOYING SIG BLOCK-----
    Evan

  • 3) Why would they travel the many many light years it would take just to send a message no one is going to receive for centuries and probably won't understand, anyway, when they get it?

    Maybe because they are French?

  • Check out the Space Telescope Science Institute [stsci.edu] for many Hubble pictures of Eta Carinae by doing a search [stsci.edu] for "eta carinae".



    ~afniv
    "Man könnte froh sein, wenn die Luft so rein wäre wie das Bier"

  • only one major mistake (Score:2)

    by Anonymous Coward
    It's always fun watching the news media try to get astronomy right.

    Actually, I'm fairly impressed that there were only two glaring errors that were obvious without having read the press release or paper. The first was on the caption that shortened Eta Carinae to just "Eta". Ca ne marche pas. Eta Car would have been okay, but might have confused people?

    The other one was a biggie, though. They say that hCar is about 100 times the mass of the sun (right) and shines 5 times brighter (wrong). I'm guessing what was actually said was either "10^5 times brighter" or "5 orders of magnitude brighter". Might also have been "5 magnitudes brighter", but that would only be 100x brighter, which wouldn't be right.

    Still, if they're only off by a factor of 20,000, that's better than a lot of other astronomy news stories I've seen... :-)=
  • What a really lame web-article this is? I mean really, there were relatively few blatant errors, but what about a proper set of related links? No links to the hubble page, none U Colorado, not even a link under the picture that I can click to get a high-res version. Sure it's an AP wire article, but they could put in some links to pages besides their own and their ad links, don't you think, perhaps just one, for those that might want some more info?

    Geez ABC, WAKE UP! This is not the evening news on TV or radio!

  • Oh, yes, I have a Nova Velorum. Doesn't accelerate very fast, but the gas mileage is good. And the seat covers feel so nice when I'm wearing short pants.
  • It would theoretically be the closest black hole Though scientists have hypothesized that a black hole exists outside our solar system for a while now.
  • That would be true if this was likely to be your common or garden-variety supernova. If it's a hypernova, that 5625 doesn't seem quite so large a safety-margin.
  • Perhaps because the existence of Tachyons has never been proved by anyone except by people that went beyond incredibility long ago?
  • And yeah was there a vast a mightly light shining down fron the heavens and lo did the many run in fear, for they felt the day of reckoning was at hand. Or maybe a star exploded 7500 years ago in a galaxy far, far away, who can tell.....


    (whisper: first post, and a silly one at that)
  • Well, I'm sure going to miss those Australian aborigines, but at least the rest of us will be okay!

    Radio waves are great, but there's nothing like a flash in the pan to get some attention.
  • I cought this on cnn.com, and one of the things that truly amazed me was that the astronomers were publicly admitting that they didn't know what was happening.

    You won't see many people admitting to the press that they don't have a clue. I mean when was the last time that you heard someone at any computer company say "Yep, that's a problem. Don't have any idea what it could possibly be"

    Most of the time they'll deny that it exists, or just say, "oh, yes, we've been working on that at some time, expect a press release in the near future"

    I'm just glad that _someone_ out there admits when they're wrong or clueless.
  • Wouldn't spending a few thousand years to blow up a star at a suitable distance be an interesting way of saying "hey, check out this part of the universe".

    or maybe a good way to kill the organisms that just sprouted on a moon in the planet's system. :)
    (hey, it's a pessimism post, so I feel out of place)
  • I'm really curious how you figure that visible light is faster than radio or microwaves? They are all electromagnetic radiation, but of different wavelengths and frequencies. As such, they all travel at 3.0e8 m/s, our good friend c.
  • Uhmm... Neutrino don't *DO* anything.
    That's their characteristic, and thats why the're
    so incredibly hard to detect.
  • It is 5 or maybe just 4 million times brighter depended on where you get your information.

    Apparently we are getting more heat from this thing than from any other object in space (outside the solar system.)
  • You see twinkling stars because of the planet's atmosphere that you're looking through.
  • A friend of my gave a presentation of the work he did with Don Lamb's group where they showed that the odds of GRBs being associated with type IIa(?) supernovae was something like 30000 to 1, the odds for other types were better (on the order of 10 to 1) but that was only because they didn't have as much data on these other supernovae(type IIc). So I'm not sure that supernovae are associated with GRBs
  • They look like they're covers to Pink Floyd albums, similar to Meddle and Saucerful of Secrets.

    To the moderators: Don't mark this as offtopic -- humor is a good thing.
  • Now I'm no serious physicist, but I do know that 7500 LHY is a stone's throw interstellar-wise. It's important to remember that stellar events involve a shitload of relativistic phenomena that can make them very interesting. I could see a potential simultaneous collapse/hypernova scenario that could cause those polar jets to spew all sorts of elementary particles a distance that could equal the radius of a small galaxy, albeit briefly. Sort of like a flash bulb. Wouldn't want to be caught in that.

  • Anyone remember that Slashdot article a few months back about the radio pulse technology that would allow for nice high speed, wide area wireless? It operated within the noise threshold of normal radio broadcasts, and if you weren't "in sync" with the transmitter, it wansn't possable to detect it against background radiation at more than 20-30 ft from the source. Good luck spotting that from a few lightyears away...
  • My best understanding is that while mass will accumulate faster than the physical radius of the object, the physical radius is relatively meaningless... theoretically, the black hole is a point entity, having no physical radius at all. The Schwartschild radius, on the other hand, is calculated by Rsch = (2GM)/(c^2) is apparently synonomous with the "event horizon", that radius from the center of mass at which light is captured.

    Reference (one among several)
    http://www.nd.edu/~bennett/Phys171/mid_rev.html
    and find in page for Black Holes ...

    Shandon
  • fit models around your hypothesis :)
  • 7500 light years is a good amount of elbow room. Now if it was say 100 LY away I'd start to worry. A supernova at that distance would probably sterilize the earth. It's a good thing we live out in the unfashionable end of a spiral arm of our galaxy. The core probably has some fearsome radiation levels.
  • I hope we have "gamma-block 1Million" sun-screen lotion by then........
  • I'm just glad that _someone_ out there admits when they're wrong or clueless.

    I just wish they were more forthcoming with phrases like 'our THEORY is' and 'we BELIEVE'. In so many of the sciences, there is so much faith (belief without demonstrable proof) put into conjectures. So the equations all add up? What happens when you factor in the constant that you didn't know about because it had such a small effect withing your test cases? For learned people this isn't a problem. A good college trains to be skeptical -- both from our explicit studies, and by exposing us to some of the most idiotic people in the world who come up with 'scientific' garbage.

    Excuse the rant, but I get bothered when people derive an large amount of otherwise unsupportable 'facts' from some tiny amount of energy. Think about it. You see some light, determine that it was emitted from a start 7.5 eons ago, determine how big, bright that star is. Even through a relatively empty universe, light has got to run through quite a bit of space junk in 7500 years. How did any of it reach Earth. My theory is that it isn't a star at all, but an alien monitoring outpost. The outpost radiates the Earth and monitors the return signal to see what we're up to. A while back they had a new protectionist adminstration move into place that wanted to cut funding on emerging species expenses, so they had to cut the power output to their observation deck. Now the old power is back in control, so their turning their sensory devices back on us. Without a whole lot more information, my theory is just as valid as a list of esoteric equations no matter how much faith some put into them.

    I respect the guy who claims that he doesn't know what is going on. I will stop respecting him when he has no more empirical evidence, and yet claims to know because he has done some math that would prove such-n-such.
  • Part of being a scientist of any flavour is realizing and admitting you're wrong or don't know the answer. That's how scientific progress works. You start with a model of reality, as reality starts not to fit well with the model you discard it and use a revised model, repeat ad infinitum. Try reading A Demon Haunted World by Carl Sagan, it spends some time talking about the scientific principle.
  • If Eta Carinae becomes a black hole, would it be the closest known black hole, or does anyone know of one that is closer to us?

    Should make for an interesting show if it goes nova... I wonder if we'd get any sort of increase in cosmic radiation (which has happened from other supernovas, apparently).

    -tbo

  • Hubble image URL (Score:3)

    by jabber ( 13196 ) on Friday June 04, 1999 @09:08AM (#1866820) Homepage
    Here is a link [rice.edu]. And another [gco.org.au], and another [nasa.gov]. Funky!

  • They didn't have to light up their sun. It might have been a probe they sent out milliuons of years ago that reached it's destination and proceeded to "spray the lighter fluid". Mabey an experiment, mabey a way to draw attention so that someone out there will point a radio telescope at the event and hear the history of a dieing race?

    Or it could jus be a natural event. But hey! we can all fantasize a bit.

    Ex-Nt-User
  • I don't think a blast of neutrinos would have any health side-effects. They typically pass harmlessly through the body.
  • I like this story. I read in New Scientist recently that some astronomers think that occasional hypernovas wipe out all advanced life in a galaxy every few billion years which explains why none have yet contacted us.

    So they're not sure what is going on and the most likely explanation seem to be either its some ET trying to get our attention, or its some big bad hypernova which could conceivably irradicate us and finally answer the question of why you should use spare cycles to crack RC5 instead of SETI.

    It seems like sending a radio message would be less work than making a star behave strangely, so my money is on the hypernova.


  • > Are there any other stars by Eta Carinae they > can compare this to?

    Some, yes. And they all seem normal for the most part.

    > And how does this tie in to the way we usually
    > predict stars die, if that is what this thing is
    > indeed doing?

    It doesn't ... astronomers just can't figure out (pardon my french) what the fuck is going on with this thing.

    In a way, it kind of sucks that it's already blown up or whatever 7500 years ago; we're just now getting to see what went on (and are just now going to be affected by it). At least it looks cool.
    ---
  • Theoretically the energetic modus operandi of gravity. Read:
    http://www.corepower.com/~relfaq/grav_radiation.ht ml [corepower.com]

  • And on the gripping hand ... (Score:1)

    by Anonymous Coward
    Looks like the Moties turned on the propulsion laser again ... :-)
  • What's surprising about the admission of ignorance is that the media allowed it! The whole point of science is to explore the limits of our ignorance. We astronomers always admit our vast ignorance, it just usually doesn't make the newspaper when we do.

  • Clearing Up Some Things (Score:5)

    by Anonymous Coward on Friday June 04, 1999 @09:19AM (#1866830)
    This isn't a very good article. Eta Carinae is merely the closest example of a class of stars known as Luminous Blue Variables (LBVs) which have been found in other galaxies and in the center of our own galaxy, obscured by dust.

    When a massive star (more than thirty or forty times the Sun's mass) forms, the luminosity is so high that radiation pressure causes the star to lose mass. In the largest stars there is instability- the luminosity will sometimes increase to a few times its normal level and be emitted at shorter wavelengths humans can see, leading to a several hundredfold increase in visible radiation. This is accompanied by ejection of the star's surface layers.

    Eta Carinae is believed to have been a bit brighter than it is now before around 1800, and then it underwent an outburst for a few decades in the mid-nineteenth century, becoming the second brightest star in the sky for a while. The star then faded to the limits of human vision for a while and has recovered somewhat in the twentieth century.

    The luminosity of Eta Carinae has (for the past couple of centuries, at least) been tens of thousands of times that of the Sun. Most of the energy is emitted in the far ultraviolet, and the star is also behind a thick screen of dust that blocks most of the light which is visible (around ten percent is believed to get through).

    A conventional supernova explosion at this distance would be a very bright star, comparable roughly to the planet Venus (currently visible in the west just after sunset). Supernovae of comparable intensity were seen in 1006, 1054, and 1572, so this is not an uncommon event. Supernovae of this size typically result in a black hole. Since these are not terribly uncommon, the nearest example of a black hole is probably at a distance of only a few hundred light years. The local interstellar medium has been cleared out by a supernova shock wave recently which is believed to be in the Scorpius-Centaurus Association [honeylocust.com], a group of easily visible stars around 500 light years away.

    There are some theories which suggest that maybe large systems might do something more exotic, such as conversion of several solar masses of material into energy by gravitational collapse. This is an attempt to explain bright flashes seen in gamma-ray bursters (you can see one for a few minutes in binoculars from a distance of billions of light years) without having to have the energy come out preferentially in one direction. This competes with other theories in which the energy output of gamma-ray bursters is beamed.

    My guess is that gamma-ray bursters are not connected with LBVs because there should be a much higher rate of LBVs dying than observed gamma-ray bursts.
  • > For one, seeing as how we are constantly
    > observing astonomical phenomenon, this would be
    > a good way for the aliens to improve our chances
    > of actually seeing the message, and two, we'd
    > probably notice any glaring anomalies. So, Could
    > this be the one?

    What, by modulating the brightness of the star? I can just picture it ...

    SETI researcher #1: Hey, Dale, get over here ... I think I've got the first character of the alien transmission...

    SETI researcher #2: 'N' ...

    SETI researcher #1: I wonder what it means...

    SETI researcher #2: Someday, in ages to come, our children shall know...

    --- a couple hundred years later ---

    SETI4 researcher #1: Enod, we've got another character of the transmission... five characters now...

    SETI4 researcher #2: 'N' ... 'E' ... 'E' ... 'D' ... 'H'?

    SETI4 researcher #1: Yeah ... but, what's "needh"?

    SETI4 researcher #2: Someday, in ages to come, our children shall know...

    --- a few thousand years pass ---

    N'GANTHOK researcher #1: The alien message is complete, Miznok! Finally, we shall read together the cosmic truth sought by our anscestors for so many ages...

    N'GANTHOK researcher #2: "NEED HELP SEND MORE BEER"...

    ---
  • Remember, these stories don't just magically appear. Slashdot consists mostly of user-submitted stories. If you see something of significance that should be posted here, submit it! That's what the link on the left side of everything titled "submit story" is for, after all!
  • that is by no means a wierd phenomenon, ever see a twinkling star? its just a star that rotating fast enough to create a fast bright/dark/bright/dark effect. not a big deal

    Just some rough calculations here. Let's say it's twinkling at a rate of one strobe every five seconds (this seems slow, most stars I've seen twinkle go much faster). Now, assume it's a normal sun-sized star, call it 1,300,000 km in diameter. Now, find the circumference and we get roughly 4,000,000 km in circumference. Dividing, we find that this star is rotating, at the edge, at roughly 800,000 km/sec.

    Yes, you read correctly. A hair under three times the speed of light.

    In reality, the only stars which rotate this fast are neutron stars/pulsars, and they're very, very small so can get away with rotating that fast.

    I think I'll stick with the atmospheric-disturbances-causes-twinkling theory.
  • Would we want to contact or avoid any creatures which can manipulate physics on a stellar scale?

    Personally, I'd consider an intentional massive radiation burst as an act of war, particularly if I'm close enough for it to be ionizing radiation. Particularly as when the burst is made the creators would have no idea whether we're shielded by our planet or if we have millions of people wandering around the solar system, a matter of only a few hundred years.

  • Your probably looking for the sci-tech section of of the bbc news page.

    BBC Science News [bbc.co.uk]
  • "Visible light is the most efficient possible means of drawing attention. It goes out in all directions and it's faster than anything."

    A: All directions: Not necessarily.

    B: Faster than anything: No. All EM radiation travels at the same speed.

    Considering the kind of energy it would take to out send more visible, omnidirectional (ooh, big word) light than our sun, I'd suggest that we look elsewhere in the spectrum.

    --Mark
  • Its called science.. you notice phenomenon, hypothesize, fit models around your hypothesize and see if they fit the available evidence.

    Eta Carinae is just not quite accounted for by current models. The data collected will simply help revise those models in the right direction.

  • Nope, it would not be the closest. At 7,500 light years, it is somewhat further than Cygnus X-1 [d-n-a.net] at 6,000 light years.

    It already is an interesting show, although it would become less interesting if it goes nova as it will blind us for a while from seeing the nearby stuff which presently makes it so pretty. At least the southern hemisphere would get to see the bright light in the sky for a while.

    We'd get some increase, but it would probably have to go supernova for a significant amount of radiation to get past our atmosphere.

    Of course, a supernova would geneate a neutrino burst (most supernova models require it, or else the blast does not happen). I think we already have 300 neutrinos per cubic centimeter, and I don't know at what level they ...um.. become toxic.

  • Well. I wouldn't count on it NOT giving the earth
    a good dose or two... The amount of radiation it could emit would be amazingly intense. Previous supernovas were felt on earth, a tiny bit. I think they caught like 23 nutrinos (there were many more but those were the only ones detected) from the last big supernova. What happens when star that is this close (it's not THAT far) blows, and blows big? I'd rather not find out.

    But, it problably won't happen in our lifetime.
    - Paradox
  • would a black hole that close have effects on us?

    The formation of a black hole (i.e. the radiation from its cataclysmic collapse) could have an effect on us, but the resulting black hole would have no more effect on us than the current star does. At this distance, mass is just mass. After the collapse, space time will be warped in its vicinity, but we won't be able to tell except through indirect measurements.

    Though it seems to me that we'd have as good a chance as any for detecting gravity waves from the collapse. Anyone know more about this?
  • Something tells me that if aliens had the ability to modulate a "heavenly phenomenon" such as a enormous burst of gamma radiation, that they would have no trouble getting us to notice them using much easier methods. Namely, showing up on our doorstep.

    --synaptik
  • The other one was a biggie, though. They say that hCar is about 100 times the mass of the sun (right) and shines 5 times brighter (wrong). I'm guessing what was actually said was either "10^5 times brighter" or "5 orders of magnitude brighter". Might also have been "5 magnitudes brighter", but that would only be 100x brighter, which wouldn't be right.

    Almost certainly the original was "five million times brighter" than the Sun. The bolometric absolute magnitude of Eta Car is about -12 at the moment and the Sun is +5. That's a factor of 6 million. The visual difference is a little less, because a LBV (Luminous Blue Variable) star like Eta Car emits much of its power in the ultraviolet. (Other notable LBVs are P Cygni and maybe Mu Cephei in our galaxy, and S Doradus in the Large Magellenic Cloud. (There are only a half dozen LBVs at any one time out of a couple hundred billion stars in a galaxy. They are exceedingly rare in the first place, and exceedingly short-lived besides.))
  • Hmmm... Maybe the radiating patches on the sides of pulsars are signals too... Maybe those are beacons for interstellar space travelers.

    I wonder how many other blatant clues we've been overlooking? ;)

  • This is old news (Score:3)

    by cthonious ( 5222 ) on Friday June 04, 1999 @09:12AM (#1866853)
    ... it happened thousands of years ago. Can't you find some real news? :-)

  • Hypernova [eurekalert.org] are approximately 100 times more powerful than supernova. This still gives a fudge factor of approximately 55 times. So it's equivalent to a supernova at a distance of about 750 light years. A supernova at this distance would be harmful, but again not a complete killer. It still wouldn't be healthy but nothing like a close up view of a supernova. Now if a hypernova went off within ~1000 light years, we would be completely screwed.

    Of course if the hypernova are a factor of 10,000 times as energetic as a supernova we would be cooked. Though since it probably won't happen in the next millenium or so gives us plenty of time to advance and prevent this kind of thing from wiping us out.
  • Well if we're streatching things this far. Mabey they f-ed up royally and knew they were about to become extinct. As a last act of good will they decided to disperse all of their worldly knowledge as well as a warning on wht NOT to do to the rest of the universe. What better way is there to get your message noticed? A universal "You've got mail!" (tm).

    Ex-Nt-User

  • Hmm... not exactly an ideal method. First of all, it took 7500 years for the light to travel to earth. Talk about lag....

  • I think it's very exciting that they dont know what is going on. Now they have to re-think it all over again and hopefully they'll be moving closer to the truth.

    Without discovery there is no science.

    -Rich
  • Yes, you are right. Eta Car's total luminosity is about 10^5 times that of the Sun. This star is about as bright as any stable star can get. Any brighter, and the photons trying to escape the core of the star start knocking off the outer layers of the star's atmosphere (this is what one of the previos commenters called luminosity pressure).
  • Yes, it does grow the only thing is that it doesn't grow that fast. Consider that a white dwarf (~1 solar mass) is about the size of the earth. A neuton star (~1.5-2.5 solar masses) is about 10 miles wide. A stellar black hole (>3 solar masses) has a Shwarzchild diameter of about 1 mile. Last I checked the largest galactic blackholes (millions [billions?] of solar masses) have diameters no bigger than the diameter of our solar system.

    As for the gravitational effects at this distance, the Eta Carinae would have the same effect as before because its mass didn't change (as others have described). Case in point, if some how the Sun were instantaneously replaced with a black hole of identical mass, the only effect on the earth would be that it would become really cold and dark.
  • The mass of the black hole will be less than the mass of the parent star. A small part of the mass will be converted to energy in the supernova event (Remember E=Mc2). A far larger portion will be blown into space. Only the core will become a Black hole. Stellar fusion only produces elements with an atomic number of 26 or lower.(Iron) All elements more massive than iron are formed in supernovae events. Gold for example is the ashes of a supernova event.
  • Nova Velorum appeared about a week ago (but slashdot didn' think that a new star in the sky was worth reporting.....:-( ).

    It's the brightest Nova for 20 years - second magnitude - brighter than most of the stars in teh sky.

    Eta Carinae is fun...
  • I think I have a crude understanding of a supernova: star uses up it's fuel and collapses, core is crushed to density of a neutron star and then stops, resulting "bounce" creates shockwave which blows the star to bits, leaving a neutron star or black hole and an expanding nebula.

    So what's a hypernova? How's it different from a supernova?
  • Supernova exploding in few lightyears away will generate enough neutrinos to give you lethal dose of radiation . What is worse, the rock between you and SN makes thing even more dissapointing as some neutrinos will generate secondary particles that are more easily absorbed in you body. Most energy in SN event (99% or more) is in neutrinous.

    Fortunately, Eta Carinae seems to be pretty far from us.

    Do not worry seems like a right attitude unless you have means to move to different galaxy.

  • Sorry. I read over in sci.astro, I think, that some activity was spotted around Cygnaus X-1. That ruled it out as a black hole. I wished I had save that piece.

  • If we got sterilised we'd have to clone ourselves to keep the human race going...
  • >Of course if the hypernova are a factor of 10,000 times as energetic as a supernova we would be cooked. Though since it probably won't happen in the next millenium or so gives us plenty of time to advance and prevent this kind of thing from wiping us out.

    PFFT! (Spews drink)
    Like what?!? Switching back to lead based paint?

    This is interesting though. I never considered that there is probably no intellegent life near the core of our galaxy because exploding stars would wipe out any life nearby.

    Later
    Erik Z
  • I'm talking about the kind of radiation that would completely sterilize the earth. Nothing would live through it , not even cockroaches, not even Dick Clark. At 75 times the distance, the amount of radiation necessary for us to be wiped out would have to 5625 times as strong a source. The difference between this and a regular supernova won't be that spectacular I imagine.

    Oh sure in a worst case scenario, there might be a year or two where it would be a phenomonally bad idea to go out and suntan. There might be some species die off, and a higher mutation rate. But nothing like a close by Supernova. A close by Supernova would do quite a bit more than strip the paint off your house and give your cat a permanent orange afro.
  • Well, I've always found Eta Carina an interesting oddball. Try to find he high-res shots the Hubble took of it, it looks like something out of a sci-fi movie.
    That'll be quite a show if it blows. A heavy gamma-ray burst would kind of be a downer, but hey, I live in the Northern Hemisphere, I've got a planet's worth of rock between me and the star.

  • Yer right!

    Damn calculator...

    I did not mean to imply that visible light waves are faster than other types of electromagnetic radiation. However, for unwittingly giving this impression, I am having myself dutifully spanked by a number of nuns (all of whom were supermodels before taking their vows) so as to help me remember to Watch My Tounge When Yacking On About Things I Don't Really Understand But Enjoy Yacking On About Anyways.

    I still say, however, that a series of PMSE's (Pre-Meditated Stellar Event)is the most economical means of drawing attention to one's self in the galaxy, short of arriving personally, when compared with spewing out radio waves consisting largely of chattering talk show hosts and sounding more like static than anything even remotely intelligent.

    Most Efficient, Most Economical, not Most Fastest.


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