S0409: The Boyfriend Complexity

Lucky Raj.  This week he gets time on the biggest optical telescope in the world, the Keck Observatory.  (Well now second biggest, see comments.)  “The Keck” has two telescopes each 10 meters (33 feet) in diameter.

The Keck Telescopes are the largest optical telescopes in the world. Operated by University of California (my own university) and Caltech, they sit atop Mauna Kea in Hawaii at 13,800 feet above sea level

A large telescope helps you twice.  First of all, a larger area means a bigger bucket with which to catch light from distant objects.  The more light you can collect, the fainter objects you can see.  Second, it is an inescapable law of optics that  the finer detail (resolution) you want see, the bigger the lens (or in this case, curved mirror) diameter must be.    That’s the main reason you might use binoculars at a baseball game or opera.  There’s plenty of light.  But instead of your own quarter-inch pupils you can see more detail using the 1-2 inch lenses of binoculars to create an image you can see in finer detail.

What about the Hubble Space Telescope, surely the best telescope in the world?  Actually the Keck telescope is better than Hubble in all but one aspect.   It is on the ground.  Ground-based telescopes have to look through the air between them and space. Most of us are  familiar with when looking a great distance, either down from a mountain or across a large body of water, objects on the other side are seen moving around as if they are under water.   That distortion is due to rapid changes in the air, called turbulence, which mess up the image you are trying to see.  Hubble’s strength is that it is above all the atmospheric turbulence.

Still Keck’s astronomers are up to a challenge.  They monitor what should be point-like stars and they deform their telescopes’ mirrors within thousandths of a second to undo the atmospheric distortion.  They call it “adaptive optics”.  Under the right conditions, Keck can use adaptive optics to observe objects better than even the Hubble Space Telescope.

The best ground-based telescopes are located on tops of mountains to be above as much of the atmosphere as possible, or at least in locations with very stable atmosphere.  Astronomers say such locations have “good seeing”.   The Keck telescopes are located atop Mauna Kea, the highest point in Hawaii, at almost 14,000 feet elevation.  So lucky Raj, not only does he get time on the biggest optical telescope in the world, he gets to go to Hawaii, right?

Not so fast.  He only went down the hall. Professional operators point the telescopes.   Modern astronomers don’t look through an eye-piece anyway, they record images with digital cameras.  They receive images over the internet.   So Raj just went down the hall, to a dingy little conference room with a bunch of computers.  (Did anybody notice what email client Raj still uses?)    If you are interested in becoming an astronomer don’t despair.  Students and faculty still sometimes do go to Hawaii, or even Chile, to observe.

Modern astronomers don't look through eye pieces. They record images with digital cameras.

Raj had something exciting to do tonight, looking for planets in a stellar system outside our own.  Also called extrasolar planets or exoplanets, astronomers’ instruments are actually sensitive enough to find planets orbiting other stars.  But generally not by direct imaging.  The nearby star is too bright and the planet is almost always too dim.   In Raj’s case he was looking for a star passing in front of the star Epsilon Eridani, a star from Sheldon’s song.

Imagine you were an extra-terrestrial watching our own Earth go around the Sun from another stellar system.   Our Earth has a diameter about 1/100-th the size of the Sun.  So a distant observer around another star could hardly see the little bit of light reflected by the Earth from the Sun compared to the enormously bright Sun itself.  But if you, the alien observer, are in just the right place, sometimes the Earth will pass between us and the S It makes a kind of tiny eclipse called a “transit”. Because area goes as the square un. of the diameter, our Earth would block out 1/10,000-th of the Sun’s brightness.   A sensitive enough measurement would see its transit in principle.    Observers in our stellar neighborhood would see this dimming for at most a few hours, but regularly every year.     Jupiter would be much easier, it would block a full 1% of the Sun’s intensity, although only once every twelve years, the time it takes Jupiter to orbit the Sun.

During a "transit", an extra-solar planet passes in front of a star, dimming it ever-so-slightly ever-so-briefly.

Astronomers have other techniques, too.   Just as stars’ gravity pulls on planets to make them go around their orbits, the planets pull on stars.   Newton’s third law requires it.  For every force (in this case gravitational pull of a star on a planet) there must be an equal and opposite force (in these case the pull of the planet on the star).   The only difference is the stars are much more massive and don’t change their velocity anywhere near as much as the planets do in response to the same force.   Thus the stars move in tiny circles with the period of the planets orbiting them.   For the same reason when you jump off a table, not only does the Earth pull you down, but you pull the Earth  up towards you with exactly the same force.  Astronomers can measure this tiny dance of the stars by measuring their motion towards and away from us.  A star that is heading towards us will emit radiation just a little bluer than one heading away from us which is just a little redder, due to a shift called the Doppler effect (remember the Halloween episode?):

The "Doppler Effect" precisely measures the motion of stars, which changes as their own planets pull on them.

Want to find more exoplanets?  There’s an app for that.  The  iPhone has a (free) exoplanet app.  It beeps every time a new extra-solar planet has been discovered.  (And besides, the app has really cool animations.)   So far, it is easiest to find the largest, Jupiter-sized, planets,  which are closest to their host star.  But as the technique improves astronomers will find smaller and smaller planets.  We have not yet found a planet at the right size and distance to host water on an Earth-like surface.  But it may come soon.  The Kepler satellite uses the same technique as Raj, but using a space telescope so it is even more sensitive.   I would not be surprised if they announce an Earth-like neighbor within the next year or so.

Astronomers know of over 500 exo-solar planets to date.    Since the technique only finds really large ones so far, they are safe from Drs. Tyson and Brown.

22 Responses to “S0409: The Boyfriend Complexity”

  1. Roy Thompson Says:

    Very ironic, I was watching my astronomy prof’s lecture right before it. Don’t steal him away from us, btw. 😛


  2. Joe Puente Says:

    I did NOT notice the email client raj was using. What was it? Eudora?

  3. Mezga0153 Says:

    I saw it! pine!

  4. Aitor Robleto Says:

    Nice article, but, btw, the largest opyical telescope in the world is no longer keck, is the spanish Gran Telescopio Canarias, in Canary Islands, with 10,4 meters diameter!!

    • David Saltzberg Says:

      Indeed it wins by 40 cm. Someone should let the Keck people know to fix their website: http://keckobservatory.org/about/the_observatory which still says “Their instruments are the twin Keck telescopesthe worlds largest optical and infrared telescopes.”

      • feldfrei Says:

        The discussion may have a bit of record hunting regarding the fact that the difference is only 4%. However, the two Keck telescopes form world’s largest pair of optical telescopes and provide a feature which is not seen on the Canary Islands: interferometry – http://en.wikipedia.org/wiki/Nulling_interferometry
        The effective resolution is then given by the telescopes’ baseline of 85 m.

        Apropos binoculars – world’s largest is this one in Arizona: http://medusa.as.arizona.edu/lbto/ Our neighbouring Institute here in Heidelberg (MPI for Astronomy) is one of its collaboration partners.

        Most of the very large mirror mounts are made of Zerodur, a glass-ceramics of nearly zero thermal expansion coefficient. This technology from space research found its way to everyman’s homes – in form of cooktops: http://upload.wikimedia.org/wikipedia/commons/thumb/3/36/Ceranfeld.jpg/800px-Ceranfeld.jpg

      • Anonymous Says:

        Yes, but if we go fo interferometry, by far the champio is the european VLT in Chile, 4 tlescopes of 8 meters plus 4 of two in a baseline of more than 200 meters. By far more powerful.

        Also think that a telescope mirror is a circle, and that the area grows with the sqaure of the radius, so thos 40 cm gives a light collector area 25.6 square meter greater!!! that is a lot. Also GTC is10 years more modern, and is using technologies that has not been used before, with its mirror made to a few nanometers precission, and many interesting instruments never used before. But what ever the true is that this was like an essay for the EELT of 45 meters, that will be a monster with the 30 meter telescope, thos will open a new era in astronomy for sure.

      • Aitor Robleto Says:

        I also forgot to mention the SAALT south african telescope, its diameter is 11 meters!!! the problem is that has a huge central obstruction that reduces the collector area bellow the GTC or Keck.

  5. Michael Says:

    I also noticed pine! It was my main email client during my PhD. It’s great to have these exclusive in-jokes. Keep the riff raff out I say!

    • Ricardo Says:

      I also used Pine during my PhD at the Stevens Institute of Technology (Hoboken, NJ). I didn’t know, at the time, that it was a requisite for getting the degree!

  6. Arturo Quirantes Says:

    I´m also a former pine user, and, well, I find it a bit odd. I mean, Raj is operating the (second?) largest telescope in the world, in a state-of-the-art facility, and he´s using pine? Next time, he´ll be storing the data on a floppy disk!

    • David Saltzberg Says:

      Yup, pine! That was a tribute to my colleagues. Look around a meeting I go to and you will see half the physicists and astronomers are still using pine. We can be early adopters for computers, but once we find something we like, we don’t change very quickly.

      • Arturo Quirantes Says:

        Well, I´m a physicist myself (University of Granada, Spain), and I waved Pine goodbye a long time ago, I´m now with TheBat! But yes, when we like something we change hard. I´ll only let Fortran77 go from my dead, cold hands.

        Trivia: my Pine was configured white letters on black background. Raj´s is the other way around. Nobody ever told us how to change colors.

        Next suggestion for Raj (now that he´s getting a bit, er, soft). Have him cry after Sagan´s clip hit (http://www.youtube.com/watch?v=XGK84Poeynk). No charge for the idea. Well, maybe an XXL redshift T-shirt …

      • Aitor Robleto Says:

        And in astronomy we have IRAF for example that has changed just a bit since the 80’s…not to mention that most astronomers I know like to run IRAF in the oldest version of linux they can find LOL.

  7. Christopher Blizzard Says:

    It was totally pine! I recognized it instantly.

    I was also trying to figure out what was on the terminals on the other computers. Had lots of random stuff, but it was hard to make out the paths on my TV.

    • David Saltzberg Says:

      Some of the other displays were given to the show to use by the people at the Keck telescope as examples of displays you would be monitoring when observing.

  8. Andres Ospina Says:

    I understand that you can calculate the volume of the planet by measuring the area that covers the star. But how can you calculate de distance from the star? Which technique do astronomers use to do that? Because the planet and the star are almost in the same linear plane

    • Arturo Quirantes Says:

      You mean the distance to the star being occulted? You don’t. You just find our the distance to our Sun (by watching it move and the using Kepler’s 3rd Law) and the planet’s speed. Diameter = occultation time * speed. Of course, you must take into account Earth’s motion, too.

  9. stephaniecrocker Says:



    This next link says, “While the presence of water hasn’t been confirmed yet, it is likely. And so is the presence of life.” And I don’t know how she figures that, but here’s the link anyway.


  10. Ritchie Annand Says:

    Of course, the Keck has been involved with the ‘possible direction-dependent change in the fine structure constant’ craziness: http://www.science20.com/news_articles/if_finestructure_constant_varies_then_laws_physics_throughout_universe_do_too

    I cannot for the life of me figure out what implications this would have. If the phenomenon turns out to approximate a sphere (e.g. there are poles of maximum alpha change and no change at the ‘equator’), then what meaning would that axis have?

    If true (always hedging, yes), it would be an aperture to new experiments and possibly theories. On an otherwise even playing field, it is the ability to handle the exceptions where explanations shine.

    Weird is the way forward.

    I love the PINE reference. Astronomers can be a funny bunch when it comes to computing. I’ve seen them write tortured code in C to convert hard-coded files saved in a browser out of a NED (NASA/IPAC Extragalactic Database) search, spit out data with commas to be imported into Excel and Excel macros to make the cells color-coded and square so that they can get a picture.

    It’s like the last 15-20 years in computing didn’t happen 🙂 Who knew that you could draw pictures, save them and even make web requests inside a program these days? 😉

    (Apologies to my astronomy friend – I will help develop the QSO-counting program again when my children let me sleep enough to have a clear mind!)

  11. GV Says:

    Dr. Saltzberg, have you heard about this 12 year old astrophysics prodigy who has an iq of 170? You should get him to stump Sheldon on the show (smile)


  12. Zaith Says:

    Yes, I also read that keck is no longer the largest optical telescope in the world. But to some extent article is nice and very informative.

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