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Space Science

Astronomers Find Sun's Twin 132

Posted by simoniker from the also-has-dreadlocks dept.
mroch writes "Space.com is reporting that astronomers may have found a solar twin -- a star almost exactly like our own Sun. Interesting tidbits from the article include: "The star, 18 Scorpii, sits about 47.5 light-years away in the constellation Scorpio, and has long-been suspected of being Sun-like. [...] The star burns slightly hotter than the Sun, at 5,789 degrees Kelvin compared to 5,777 degrees. It appears to rotate slightly faster than the Sun, taking 23 days to complete a rotation rather than the Sun's 25." It boggles my mind to think that we can measure temperature that exactly from 279,000,000,000,000 miles away, and that they are complaining over a 12-degree difference."
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Astronomers Find Sun's Twin

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  • Measuring temperature at great distance (Score:5, Informative)

    by Frans Faase ( 648933 ) on Thursday January 08, 2004 @06:04AM (#7913260) Homepage
    Distance actually does not matter with respect to the method used to measure the temperature, as long as you have enough light, and there is no disturbing medium in between. Both conditions seems to be met.
  • They can determine the temperature by the wavelengths of light given off by the star.

    And those dozen degrees are in Kelvin. These aren't your ordinary units of measurement we're talking about.

    • Re:They use spectrometry to measure the heat (Score:5, Funny)

      by LittleBigLui ( 304739 ) on Thursday January 08, 2004 @06:09AM (#7913283) Homepage Journal
      Yeah, there's much difference between a delta of 12 degrees kelvin and 12 degrees celcius. OTOH, you USians (and UKians?) with your funny measurements probably measure temperatures in ounces, feet or hands or something. :)
      • with your funny measurements probably measure temperatures in ounces, feet or hands or something. :)

        or maybe the body temperaure of your wife? [sizes.com]

      • Whether the measures are funny depends on how you look at it I guess, as 373K is as arbitrary as 212F for boiling water. Not to mention you have to memorize arbitrary names like nano and deci in the metric system.

        Temperature could be measured in fractions of an inch if you're looking at the wavelength of the light.

        (And a delta of 12K is the same as a delta of 12C.)

        • (And a delta of 12K is the same as a delta of 12C.)


          Exactly, that's why i found that whole "That's not your ordinary degrees, that's Kelvin" thing funny, because for me "ordinary degrees" = Celsius.
        • Whether the measures are funny depends on how you look at it I guess, as 373K is as arbitrary as 212F for boiling water. Not to mention you have to memorize arbitrary names like nano and deci in the metric system.

          Actually, if anything Kelvin is a lot less 'arbitrary' than Farenheit. Kelvin is based on Celsius, with the only difference being the 0K is absolute zero (there are no negatives on the Kelvin scale). Celsius is based on wanter. 0 for freezing, and 100 for boiling. Unlike F, which is loosely b

          • Celsius is based on wanter. 0 for freezing, and 100 for boiling. Unlike F, which is loosely based on the body temperature of a feverish woman.

            Well, unless I'm mistaken, water has different boiling and freezing points at different pressures..."less arbitrary" is probably not as good a description as "more consistent on earth at sea level".

            Kelvin, being based on Celsius, (which is arbitrary because it's boundaries are defined by the reaction of a substance that is only reliable under specific conditions...p

          • Well, 1/100 of the difference between the freezing and boiling points of water at sea level is more closely tied to a measurable physical quantity than the Farenheit scale, but the size of the degree is no less arbitrary. It's just an artifact of using a base-10 numbering system. If I were Babylonian, I might use a temperature scale where the boiling point of water is 60 degrees instead of 100. Here's the definition of the SI unit kelvin, courtesy of the US National Institute of Standards and Technology:
        • You know, these arbitrary names come after greek words. They used these words to refer to small things, so scientists, centuries after them, use these words to refer to powers of ten.

          If you are measuring in inches, you have to memorize arbitrary numbers, because there are 5280 inches in one mile, and 12 inches in a feet, which makes calculations cumbersome and prone to error.

          Metric system is intuitive, because every unit is a power of ten of a meter. This is the only thing arbitrary.

          Face it. Metric syste
    • And those dozen degrees are in Kelvin. These aren't your ordinary units of measurement we're talking about.

      Speak about yourself, Bushlover! I'm a European, and am not using any stinky Fahrenheit!

    • Re:They use spectrometry to measure the heat (Score:5, Informative)

      by ottawanker ( 597020 ) on Thursday January 08, 2004 @06:44AM (#7913406) Homepage
      Actually, 12 a degree difference in Kelvin is the same as a 12 degree difference in Celcius.

      Really, you shouldn't use the word 'degree' with the work 'Kelvin' as in the case used in the Story. It's preferable to write simply 5789 Kelvin.
    • Measuring the temperature of a star is no problem, no matter how long the distance. All you need to do is compare the number of Linux users to the number of Windows users. If the solar system has more Windows users, the star is naturally going to produce more heat due to the pent up frustrations of end-users caused by Windows crashing on a daily basis. Our own Star is only a mere 12 degrees cooler because of the growing number of Linux users to have alleviated themselves of Windows Hell.
    • "these aren't your ordinary units of measurement we're talking about"?

      Yes. They are.

      An increment of 1 degree Kelvin is exactly the same as a 1 degree Celsius increment. The difference between the two scales is only where the 0 is.

      0 degrees Kelvin is absolute zero, or -273.15 degrees Celsius (approximately). 0 degrees Celsius is 273.15 degrees Kelvin. To convert between the two, simply add or subtract 273.15 depending on the direction of conversion.

      For example: 1 degree Celsius would be 273.15 K

  • Measuring a star's temperature. (Score:5, Informative)

    by DjReagan ( 143826 ) on Thursday January 08, 2004 @06:07AM (#7913271)
    IIRC, the temperature is measured by the colour of the sun. That doesn't change the further away you get, so its just as accurate over long distances as short. However, there is the problem of dopler shift if the stars are moving away/toward each other.

    • Re:Measuring a star's temperature. (Score:5, Informative)

      by Dr. GeneMachine ( 720233 ) on Thursday January 08, 2004 @06:40AM (#7913392)
      Doppler shift should not be a problem, you can always determine the shift rate from the known frequency of certain absorption lines in the spectrum and reference your spectrum to those lines.
    • IIRC, the temperature is measured by the colour of the sun. That doesn't change the further away you get, so its just as accurate over long distances as short. However, there is the problem of dopler shift if the stars are moving away/toward each other.

      True, with minor nitpicks. Temperature is indeed based on careful spectroscopic measurement of colour. However, intervening interstellar dust will slightly redden the appearance of more distant stars. (Shorter, bluer wavelengths are scattered more effect

  • Earth's twin? (Score:5, Interesting)

    by eggstasy ( 458692 ) on Thursday January 08, 2004 @06:09AM (#7913281) Journal
    What do we know about that star and its surroundings? Is it likely to have inhabitable planets or is it bathed by lethal radiation from neighboring novas?
    How long before we can actually check these stars for Earth-like planets? Last I heard, we now had the ability to detect planets slightly smaller than Jupiter. Will we find, or even see, an inhabitable planet within a few decades?
    • Just point a big dish in its general direction and send them this message:

      APPLE UNVEILS IPOD MINI, XSERVE G5

      In 100 years time we will know the answer :)

    • Earth's twin, 300e6 years ago (Score:4, Interesting)

      by RobertB-DC ( 622190 ) * on Thursday January 08, 2004 @10:53AM (#7915095) Homepage Journal
      What do we know about that star and its surroundings? Is it likely to have inhabitable planets...

      As cool as it is to find a star that's a twin to ours, it's incredibly unlikely that we'll find a planet even remotely similar to Earth.

      For one thing, the article notes that 18 Sco is 4.2 billion years old, while Sol is 4.5 billion years old. If everything else were exactly equal, it would be like stepping back 300 million years back in time. A quick Google finds that one of the more complex forms of life found 300e6 years ago [brown.edu] on this planet was the Velvet Worm [vic.gov.au] -- not a species known for its technology.

      But even that is unlikely, given the Earth's unusual formation. This planet has an unusual mix of minerals on its crust, plus plate tectonics to keep them mixed, and an iron core that's magnetic enough to keep out the sun's ionizing radiation. Plus, a moon big enough to stir up the oceans, and a tilt to generate asymmetrical solar heating... and all that apparently due to a one-in-a-million collision [ohio-state.edu] between a proto-Earth and a Mars-sized planet not long after Sol formed.

      I can't find the quote, but someone calculated the odds of finding another sentient species as tiny. It's not that it doesn't develop elsewhere in the galaxy... there are billions of chances, so surely more than one came up all 7s. It's just that the distances are so vast, and the chances of favorable development so small, that entire civilizations (or species) could rise and fall by the time their transmissions reach another civilization's satellite dishes.

      But still, at less than 50 light years, it would only take a few hundred years to get there and back. Are the generation ships [univelt.com] ready yet?
      • do we really know enough to assume that sentient life is only possible in conditions similar to earth? Can we rule out life developing in silicon compounds, plasmas, or even (as Cairns-Smith believes could have happened on Earth) clay?
      • The fact is that we really don't have any firm data on how easily life arises and how often it evolves intelligence. A 300,000,000 year difference in the age of the star is probably largely irrelevant to the probability that it has intelligent life versus our own.

        Life on our own planet spent the 1st 2.5-3.5^9 years on this planet being unicellular. Only in the last ~650^6 years have complex organisms been around to our knowledge. All of the genetic and fossil evidence seem to point toward the evolution
      • firs we quabble over a delta of 12 kalvin, now we fight over 300 million years.

        The way I see it why dont we go there an colonize the planet before any inteligent life forms so we dont have to have some giant war over it.
      • Velvet Worm -- not a species known for its technology.

        Don't forget the star is 12 degrees warmer, who knows what those Velvet Worms could have accomplished with an extra 12 degrees! :D

        -

  • Kelvin, not degrees Kelvin (Score:1, Informative)

    by Anonymous Coward
    nt

  • hey idiot mroch (Score:3, Interesting)

    by DrSkwid ( 118965 ) on Thursday January 08, 2004 @06:55AM (#7913438) Journal
    "... and that they are complaining over a 12-degree difference."

    Who's complaining?

    Observation != complaint.

    for my 2 pence, this twin bit is just bunkum

    They are 0.3 billion years different in age (presumably USian billions)

    Which is almost 10% of their total age, that's like your human twin being born when you are 8 years old but you both weigh the same!

    It is a bad analogy.

  • 50 closest, closest matches to the sun (Score:5, Informative)

    by nimblebrain ( 683478 ) on Thursday January 08, 2004 @07:41AM (#7913625) Homepage Journal

    I like David Nash's list of 50 nearby sunlike stars within 50 light years [astronexus.com].

    18 Scorpii is on there, as is the infamous Tau Ceti. 18 Scorpii was one of the four closest matches.

  • I don't believe it, how can they possibly know? (Score:1, Funny)

    by Anonymous Coward
    They determine the temperature of a star, based on the light it gives off? That is bogus. What if something in between the star and Earth is changing the wavelength of the light? I can shine a light-bulb through a green sheet of plastic, and change it, but the temperature of the bulb doesn't change.
    • You don't change the wavelength of the light, you just absorb the wavelengths which don't make up green.
    • Astronomers look at the spectrum of the star--the relative intensities of each wavelength of light produced by the star's heat. Assuming the star is a black-body radiator (which isn't totally true, but pretty darn close), using first principles you can solve for the temperature of such and object as a function of the peak wavelength of light radiated. See "Thermal Physics" by C. Kittel and H. Kroemer for a better discussion.

      Also, single wavelength filters (like your green sheet of plastic) aren't a natur
    • What if something in between the star and Earth is changing the wavelength of the light? I can shine a light-bulb through a green sheet of plastic, and change it

      Wrong. Your filter can reduce the brightness at various wavelengths, but you CANNOT(*) change the wavelength. You can forget about brightnesses and calculate the temperature by measuring frequency behaviours.

      (*) Footote: Yes, there are a handful of materials that can double or halve the wavelength of light, but there is no way in hell an enormous

  • Interseteller Probes (Score:4, Interesting)

    by T.Hobbes ( 101603 ) on Thursday January 08, 2004 @08:16AM (#7913758)
    I'm undoing my moderations to post this, but:

    does anyone here know what advances would be necessary to send probes & recover data about nearby star systems? Ion drives seem to be moving in the right direction, to use a phrase, but would they be sufficient in longevity & speed to make a multi-light year journey? And what sort of remote communication would be possible at such distances?
    A corollory to this is, does anyone know what (if any) systems the Voyager spacecraft are going to encounter, and when?

    • Re:Interseteller Probes (Score:3, Interesting)

      by turgid ( 580780 )
      does anyone here know what advances would be necessary to send probes & recover data about nearby star systems?

      Would it be possible to use the sun for a gravitational assist to "slingshot" something at realativistic speeds, and out of the solar system, or would practical considerations (tidal forces, acceleration, heat) get in the way?

      How about a huge solar sail? Would an RTG be any use for on-board electrical supply, or even a very small fission reactor using plutonium or enriched U, or even used as a

      • If we send a probe now, in the next X years we'll be able to send a better probe. It will go faster and arrive sooner than the first one.

      • Re:Interseteller Probes (Score:4, Funny)

        by jhoffoss ( 73895 ) on Thursday January 08, 2004 @10:07AM (#7914582) Journal
        What I want to know is would it be possible to fly backwards around the sun faster than the speed of light and travel back in time?
      • The sun can't be used for a gravitational assist, at least not for an launch from something orbiting the sun. A gravitational assist transfers the momentum of a planet to the spacecraft. If we go around the back side of the planet, the planet drags the spacecraft in the direction that it's moving. Since we're already orbiting the sun, we're moving on average at the same speed and direction as the sun, so we can't gain any more momentum from the sun.

      • Would it be possible to use the sun for a gravitational assist to "slingshot" something at realativistic speeds, and out of the solar system...?

        Did you just read Rendezvous with Rama? :)
        The answer is probably "no" because anything launched from Earth will be in orbit around Sol. If you're in orbit around a body, you're stuck in its gravity well. You'll always need to expend (or capture) some kind of energy to escape that well and that amount of energy is a fixed quantity. For example, the Voyager probe

        • Better catch this before someone else jumps on it -- IRRC should be IIRC.
          I apologize for any computer crashes, wars, or deaths this may have caused.
        • That's rather interesting. I wonder...remember this story [slashdot.org] about the fact that we don't seem to need a leap second anymore? If the Earth transferred enough energy to other bodies, we would drop into a lower, faster orbit around the sun.

          That said, I seriously, seriously doubt we've transferred enough energy to tiny spacecraft to accomplish this.
        • Don't we also affect spin by moving mass around on the earth? Building large buildings slightly slow the spin, while filling in sea level areas with fill-dirt from higher regions would counter-it. Of course, all of this should be an extremely small effect, right?

          • Don't we also affect spin...

            Nothing near to what the drag from the tides do. The tidal drag will slow Earth's rotation down until it's locked with Luna's orbit. One day, Luna will only be visible from one of Earth's hemispheres -- just as Earth is only visible from one of Luna's hemispheres.
    • Well, given the problems that present launches have with getting to Mars, I think that some steps backwards in design need to be made. Pull out the design of Voyager and learn why it lasted this long, and improve on it, to make something that's durable, like Voyager, with more modren information gathering techniques.

      Unfortantly, i don't think that the Voyager craft will meet up any systems, at least not while under power, as I think they have about 20 years left before thier power is gone.
      • Pull out the design of Voyager and learn why it lasted this long,

        Let's see. Oh, look here: Voyager isn't attempting to crash at high speeds onto a planet with almost no atmosphere. Instead, we gave it a shove and it's just floating away passively now, far away from any body that could harm it. Maybe that could just be the reason???

    • Re:Interseteller Probes (Score:2, Informative)

      by ajagci ( 737734 )
      From NASA: [nasa.gov]

      Eventually, the Voyagers will pass other stars. In about 40,000 years, Voyager 1 will drift within 1.6 light years (9.3 trillion miles) of AC+79 3888, a star in the constellation of Camelopardalis. In some 296,000 years, Voyager 2 will pass 4.3 light years (25 trillion miles) from Sirius, the brightest star in the sky . The Voyagers are destined--perhaps eternally--to wander the Milky Way.

      This [psu.edu] answers the question of what advances are needed. Basically, we need either laser-powered solar sail

    • Hmm. The old rocketry problem - you need reaction material to throw out the back end in order to push yourself, but then you need more reaction material to lift the reaction material itself - really makes useful travel between stars difficult.

      Ion drives are better about that than rockets, but they still need fuel, so the problem is still there, just smaller. Given the very small acceleration of current ion drives, you'd want to be accelerating just over half the way there, then turn around and decelerate f

  • Wrong distance... (Score:2, Informative)

    by understress ( 85878 )
    Actually, that distance would be more like 2.7862056^14 miles.
    186,000 miles/second x 60 seconds/minute x 60 minutes/hour x 24 hours/day x 365 days/year x 47.5 years.

    • Dude, if you're going to insist on filling your answer with so many digits of precision, you need your data to have that many to begin with.

      You have only 3 digits of precision in both your speed of light (186 000) and your distance in light-years (47.5), so it's 2.79 x 10^14 mi.

      • But he has even fewer digits of precision in the the "60"s, the number of seconds per minute and minutes per hour!

        (yes, I know.)

        YAW.
      • You are correct. That was a quick calculator calculation, and I just copied the answer from the screen.
        I should have known better, too early in the morning. I was just suprised that no one else had noticed the distance was so far off.
    • It boggles my mind to think that we can measure temperature that exactly from 279,000,000,000,000 miles away
      What do you mean wrong distance? This is correct: 2.79 * 10^14 -- you only have three significant digits unless you specify the 47.5 light-year term with more precision.
      • OK, i need to insert my foot into my mouth now. This just proves that I need to think more before posting.
        My thought process was after reading the article post was:

        - 279,000,000,000,000 miles?
        - Wow, light travels 186,000 miles per SECOND (roughly)
        - There can't be nearly enough zeros in that distance.
        - Calculate the value.
        - 2.79 * 10^14 sure sounds a lot bigger than 279,000,000,000,000 (at least to my feeble mind).
        - Post to Slashdot and look like an idiot!

        That said, my apologies to simoniker.
  • Now scientists just need to solve that little problem of us not being able to travel one light year yet, let alone 47 and we're good to go.
  • It boggles my mind to think that we can measure temperature that exactly from 279,000,000,000,000 miles away, and that they are complaining over a 12-degree difference."

    Considering the fact that they used the same method to measure the temp of this new sun as they probably used to measure the tmep of our existing sun which is also considerably far away (albeit it closer to us) I'd say the measurements are just as accurate as they could be.
  • That's almost as amazing as finding one's "hand twin!" I know I'd pay good money to see twin stars showcased in some type of entertainment venue. Gosh.

  • Spoiler alert! (Score:1, Funny)

    by Anonymous Coward
    I think it's going to turn out that what we call our sun is actually the twin, and that other star is the real sun.
  • ...and that they are complaining over a 12-degree difference.

    Umm.. we are talking about kelvin here. It's not like they're measuring in F or C. That would truely be impressive.
    • Umm.. we are talking about kelvin here. It's not like they're measuring in F or C. That would truely be impressive.

      What's the difference between measuring something in Kelvin and measuring it in Degrees Celsius? I mean, you just add 273.15 to the figure. It's no more or less impressive in terms of accuracy. Or did I miss a smiley somewhere there?
  • It boggles my mind to think that we can measure temperature that exactly from 279,000,000,000,000 miles away, and that they are complaining over a 12-degree difference.
    Yeah, but that's 12 kelvins, which is 21.6 degrees Fahrenheit (12*9/5).
    So it's less like the difference between a warm day and a cool day, and more like the difference between a warm day and a cold day.

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