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 and Earth at 10pc (~32 Ly) would be separated from the Sun by only ~0.1 arcsec. from the Sun by only ~0.1 arcsec. 1 arc second = angular extent of a penny seen 3.9 km (2.45 miles) away 3.9 km (2.45 miles) away

Direct Imaging of Exo-Planets (Jovian Planets) Reflected light detection of Jovian planets requires contrast ratio at  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’“young” = planets are still ‘hot’ thus, much brighter than older planets! thus, much brighter than older planets! “ nearby ” = large separation between stars and planets!“nearby” = large separation between stars and planets! normal stars (old & distant)young distant starsyoung & nearby stars!!!

Coronagraph Blocking the bright region to see nearby faint stuffs…

Angular Resolution of Telescopes Larger telescopes will produce sharper images…

Effect of Earth Atmosphere Light = wave Light = wave Perfect wave form got deformed due to turbulence… Perfect wave form got deformed due to turbulence… breezeturbulence in atmosphere

Eliminate the effect of Atmosphere (Adaptive Optics)

Power of Adaptive Optics

Need for a confirmation! Actual Example from Keck AO Actual Example from Keck AO

Need for a confirmation!

Some early discoveries… European Very Large Telescope European Very Large Telescope o 2M1207b  central obj is a brown dwarf o AB Pic B  companion is a BD o GSC B  companion is a BD AB Pic B GSC B 2M1207b

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

Fomalhaut direction of Fomalhaut movement

HR 8799

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

4 th planet was discovered in th planet was discovered in 2010

HR 8799 A Scaled-up version of the Solar System A Scaled-up version of the Solar System

If we replace HR8799 with our Sun… Our Solar System Planets JupiterNeptuneUranusSaturn 5 AU30 AU19 AU9.5AU Observed HR 8799 planetary system ebcd After replacing the central star with our Sun HR8799 is about 2.5 times more massive than our Sun.

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

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

β Pictoris b about 11 M Jupiter planet orbiting around a 2.5 M sun star 63 lightyears away. about 11 M Jupiter planet orbiting around a 2.5 M sun star 63 lightyears away.

Future Gemini Planet Imager (34 million USD device) Gemini Planet Imager (34 million USD device) Simulation of a planet detected with GPI. Simulation of a planet detected with GPI. First light in 2012 First light in 2012 Will look at thousands of nearby stars 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 M Jupiter a young (100Myr) Sun-like star at 55 Lyrs

James Webb Space Telescope 2018 Launch? 2018 Launch?

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

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

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

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

Nulling Interferometry

Observing with Hubble Space Telescope HST observations of several hundred stars HST observations of several hundred stars Using two spacecraft rolls for better contrast… Using two spacecraft rolls for better contrast… Roll 1Roll 2 HIP 77199, background object Roll 1 – Roll 2