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This page is intentionally blank. Big Telescopes. for a Small World. A new view of the Universe II Fred Watson, AAO April 2005. Big Telescopes for a Small World. The secret obsessions of astronomers. Characteristics of astronomy today. Highly comprehensive range of instrumentation

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  1. This page is intentionally blank

  2. Big Telescopes for a Small World A new view of the Universe II Fred Watson, AAO April 2005

  3. Big Telescopes for a Small World The secret obsessions of astronomers

  4. Characteristics of astronomy today • Highly comprehensive range of instrumentation • Infinite computing power • Access to every part of the electromagnetic spectrum:-rays,X-rays,UV,visible (optical),IR,mm-wave,radio • Not to mention particles, gravitational waves… (So we won’t.) Big Telescopes for a Small World

  5. The Universe through different eyes... Big Telescopes for a Small World

  6. What’s so good about opticalastronomy? • Visible light is emitted by ‘ordinary matter’ in the Universe—i.e. stars • The visible spectrum is rich in the ‘bar-code’ of atomic and molecular features • Optical observations bridge long and short wavebands • You can do it with your feet on the ground Big Telescopes for a Small World

  7. The Schematic Ground-Based Optical Telescope • Something large to collect and focus the radiation • A complicated bit in the middle for analysis • An optical detector • A ground-based mounting Big Telescopes for a Small World

  8. Detectors… Big Telescopes for a Small World

  9. Astronomical cameras are not small…(This is IRIS2, a multi-purpose infrared camera on the AAT)

  10. Subtracting the sky…

  11. Other complicated bits… Spectrographs conventionally use a grating, prism or grism Sends light of different wavelengths in different directions… Hence (via the spectrograph camera) to different positions on the detector (which is a CCD or an infrared array). (This slide and the next three courtesy Gordon Robertson)

  12. Reflection grating spectrograph (schematic) collimator slit grating  b cc  d i detector camera Big Telescopes for a Small World

  13. Volume phase holographic (VPH) gratings • 3-d modulations of refractive index in gelatin layer • Peak efficiency up to ~90% • Wavelength of peak efficiency can be tuned • Transmission gratings • DCG layer (hologram) is protected on both sides • Each grating is an original, made to order • Large sizes possible Big Telescopes for a Small World

  14. Test of a prototype VPH grating Big Telescopes for a Small World Note: no antireflection coatings

  15. Why make telescopes ever bigger? • To gather more light from faint sources because there are no further gains to be made in detector sensitivity • To improve resolution: R= 1.22 / D As the mirror diameter Dgets bigger, the resolution R gets finer.

  16. Large Telescope Mirror, 1969

  17. A 3.9-metre mirror can resolve 0.03 arcsec BUT… r0is Fried’s parameter for wavefront distortion Cn2is the refractive index structure constant Cn2 is integrated over the full height of the atmosphere

  18. 1 arcsecond The end-product is… This is very depressing indeed 

  19. Big Telescopes for a Small World Can you do anything useful in such conditions?

  20. Detection of extra-solar planets

  21. The answer to life, the Universe and everything... Spectrograph Slit Detector Multi-object spectroscopy with fibre optics

  22. Basic building-blocks of the Universe If this was our Galaxy, we’d be here Galaxies… • Around 100,000,000,000 stars • Lots of gas and dust (in spirals) • Around 100,000 light years across (or 1,000,000,000,000,000,000 km)

  23. Big Telescopes for a Small World Antidotes to atmospheric turbulence

  24. The Eagle Nebula—stellar birthplace

  25. But – the Hubble project’s total cost is$US 6 billion. That would buy 60 of today’s ground-based 8-metre telescopes…

  26. The world’s largest telescopes, 2005

  27. The crowded summit of Mauna Kea

  28. Antu, Kueyen, Melipal and Yepun

  29. It’s all to do with atmosphere… 1 arcsecond But at the VLT, on the same scale…

  30. Big Telescopes for a Small World What do we do next?

  31. The thinking goes like this…

  32. VLT: Very Large Telescope 4×8 m (16 m equiv.) ELT: Extremely Large Telescope 25 m CELT: California Extremely Large Telescope 30 m GSMT: Giant Segmented-Mirror Telescope 30m TMT: Thirty-metre Telescope (US + Canada + ?) Euro50: formerly SELT… Future plans for large telescopes...

  33. OWL—Sharp-eyed and OverWhelmingly Large

  34. Big Telescopes for a Small World …And what can we do with such monsters?

  35. What might we study with OWL? Earth-like planets out to about 75 l.y. by direct imaging Individual stars in moderately distant galaxies – galactic archaeology Galaxies forming at look-back times up to 10 billion years Exploding stars at look-back times up to 12.5 billion years

  36. Not to mention the completely unexpected …

  37. Big Telescopes for a Small World The End

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