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Exoplanets : direct detection

Exoplanets : direct detection. ASTR 1420 Lecture 17 Sections 11.2. Imaging planet is hard!. Direct imaging is very hard, because … tremendous brightness contrast ratio between stars and planets ( e.g.) Sun outshines Earth about 10 billion times

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Exoplanets : direct detection

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  1. Exoplanets:direct detection ASTR 1420 Lecture 17 Sections 11.2

  2. Imaging planet is hard! Direct imaging is very hard, because… tremendous brightness contrast ratio between stars and planets (e.g.) Sun outshines Earth about 10 billion times and Earth at 10pc (~32 Ly) would be separated from the Sun by only ~0.1 arcsec. 1 arc second = angular extent of a penny seen 3.9 km (2.45 miles) away

  3. Direct Imaging of Exo-Planets (Jovian Planets) • Reflected light detection of Jovian planets requires 10-9 contrast ratio at  0.5 • Current state-of-the-art achieves 10-4~-5 at 1.0 sensitivity curve

  4. How can we do then? Focus on nearby young stars • “young” = planets are still ‘hot’ thus, much brighter than older planets! • “nearby” = large separation between stars and planets! normal stars (old & distant) young distant stars young & nearby stars!!!

  5. Coronagraph Blocking the bright region to see nearby faint stuffs…

  6. Angular Resolution of Telescopes Larger telescopes will produce sharper images…

  7. Effect of Earth Atmosphere • Light = wave • Perfect wave form got deformed due to turbulence… breeze turbulence in atmosphere

  8. Eliminate the effect of Atmosphere (Adaptive Optics)

  9. Power of Adaptive Optics

  10. Need for a confirmation! • Actual Example from Keck AO

  11. Need for a confirmation! • Actual Example from Keck AO

  12. Some early discoveries… 2M1207b • European Very Large Telescope • 2M1207b  central obj is a brown dwarf • AB PicB companion is a BD • GSC 8047-0232 B  companion is a BD AB Pic B GSC 8047-0232 B

  13. Recent Discoveries • In 2008, by Canadians, about 350 lightyears away in a star forming region… • In 2010, common proper motion was confirmed. • Wide separation (about 300 AU)  probably not formed as a planet. • In 2012, the companion is estimated to be a brown dwarf.

  14. Fomalhaut direction of Fomalhaut movement

  15. HR 8799

  16. Direct Imaging of Planetary System! Science (2008) C. Marois, B. Macintosh, T. Barman, B. Zuckerman, Inseok Song, J. Patience, D. Lafreniere, R. Doyon

  17. 4th planet was discovered in 2010

  18. HR 8799 • A Scaled-up version of the Solar System

  19. If we replace HR8799 with our Sun… HR8799 is about 2.5 times more massive than our Sun.

  20. Against the best model predictions • We can get spectra of exoplanets now!!

  21. Another Imaged planet around massive star. • 2008 November reanalysis of 2003 data The putative planet was not visible in early 2009 follow up data!?

  22. βPictorisb • about 11 MJupiter planet orbiting around a 2.5 Msun star 63 lightyears away.

  23. Future • Gemini Planet Imager (34 million USD device) • Simulation of a planet detected with GPI. • First light in 2012 • Will look at thousands of nearby stars  capable of imaging true Solar System analogs (i.e., a Jupiter at 5AU) 10 yr orbit of a 2 MJupiter a young (100Myr) Sun-like star at 55 Lyrs

  24. James Webb Space Telescope • 2018 Launch?

  25. Terrestrial Planet Finder • considered two versions • TPF-C : 3-4 meter telescope • TPF-I : 5-6 ~3 meter telescopes Demised!!

  26. Darwin European version of TPF • European mission • smaller version of TPF • NASA collaboration • Ended in 2009 Demised also!!

  27. Ground-based Observation Only… • In a coming decade, we will have dozens of (if not hundreds) exoplanet images • And, we will have spectra of those exoplanets  able to check their habitabilities and eventual biosignatures! 40m European-Extremely Large Telescope Thirty Meter Telescope

  28. In summary… Important Concepts Important Terms Direct Imaging Detection! Adaptive Optics • Images and spectra of exoplanets are obtainable already! • Young and nearby stars as best targets • Needs for 2nd epoch observation for confirmation. • Chapter/sections covered in this lecture : 11.2 • Biosignatures of the Earth : next class

  29. NullingInterferometry

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