1. Using New Techniques in the Search for Extrasolar Planetary Systems: Are we unique? Phil Hinz University of Arizona Associate Professor Director, Center for Astronomical Adaptive Optics Jupiter at 5 μm wavelength Taken with MIRAC at the 6.5 m MMT Outline: What we know about other planets Technology to directly image them. What we might find out.

2. What we know about other planetary systems

3. The Solar System (Simplified) Radius:10.010.1 Mass:10.0000050.001 Distance:15 Ang. Separation at 10 pc0.1”0.5”

4. How do we detect extrasolar planets (What’s wrong with this picture?)

5. Indirect detection techniques Doppler shift of the starlight Light from the star will have a periodic motion to the Doppler shift of its spectrum (about 1 m/s for Jupiter). The ~500 planets detected have used this technique. Movement of star’s position on the sky A star with a planet orbiting it will appear to wobble back and forth by a small amount (1 milliarsecond if it is identical to Jupiter). This technique has not yet been successful. Transit of the planet in front of the sun If the orbital plane is aligned with our line of sight we will see the starlight appear to dim once per orbit. Two planets have been detected with this technique.

6. Properties of Other Planetary Systems planets appear to be like Jupiter more massive planets than in our system planets are close to their stars Less massive planets are more common

7. Properties of extrasolar planets many more highly eccentric orbits than in our Solar System Planets are typically found around stars with a higher fraction of heavy elements (higher metallicity in astronomy jargon).

8. Planets discovered by Doppler shift The likelihood of detecting a planet appears to be dependent on how metal- rich it is.

9. A Transiting Planet The Doppler technique yields only planet masses and orbits. Planet must eclipse or transit the star in order to measure its radius. Size of the planet is estimated from the amount of starlight it blocks. We must view along the plane of the planet’s orbit for a transit to occur. –transits are relatively rare They allow us to calculate the density of the planet. –extrasolar planets we have detected have Jovian-like densities.

10. Measuring the Size of a Planet When a planet passes in front of a star it blocks out a portion of its light. The amount of light it blocks depends on how big the planet is. Change in Intensity = R planet 2 / R star 2 Transits we have seen, have decreased the star's flux by about 1%.

11. So, How common are planetary systems? We can only see the most massive (Jupiter-like) planets in other systems, and only out to about 4 Astronomical Units, yet we have found many planetary systems. The fraction of stars with planets could be quite high! Roughly 10 out of every 100 stars have been detected to have planets The actual fraction may be higher! − Planets might be in longer orbits. − Planets might have a low enough mass that they are undetectable currently.

12. Could any of these planets harbor life? A star called Gl 581 has 6(!) low mass planets, b, c, d, e,f,g. Gl 581 c is >5 Earth masses (M E ) and at 0.07 AU Gl 581 d is >7 M E and at 0.25 AU Gl 581 g is >3 (M E ) at 0.15 AU Could these be habitable? Artist's Conception! (not actual image)

13. 13 Goldilock’s planet 13

14. What might we learn in the next decade? Doppler velocity detections will find increasing numbers of planets that are less massive and in larger orbits. If other planetary systems are like our own, the massive planets are typically at larger separations. These take a long time to detect with Doppler velocity, but we may be able to see them directly. Large telescopes are needed to see the very faint planets. We need to have telescopes which can form sharp images and get rid of the glare from the star.

15. New Technology for Direct Imaging of Planets

16. Why do we want to directly “see” planets? l Light obtained directly from a planet could tell us quite a bit additional information about it. - Size - Temperature - Existence and composition of an atmosphere. l Planets far from their parent star take a long time to complete an orbit. - Indirect methods such as Doppler velocity detection becomes difficult.

17. MMT and LBT The 6.5 m MMT telescope is currently being used to search for planets just south of Tucson. The Large Binocular Telescope (2x8.4 m)‏ is being completed and will begin searching for planets soon! Telescopes on the ground will likely not be able to detect planets as small as Earth.

18. What type of planets might we see directly? l From the ground: - Telescopes on the ground are beginning by looking for Jovian planets. l Larger (brighter)‏ l More massive (bigger effect on star)‏ Using a telescope in space: Space missions will extend the search to look for Terrestrial planets. Fainter (smaller)‏ Less massive (smaller effect on star)‏ Concepts for NASA's Terrestrial Planet Finder Mission The Large Binocular Telescope on Mt. Graham, AZ

19. The physics behind planet emission The light peaks at a particular wavelength which depends on an object's temperature. T (deg. Kelvin) = 2900 / λ (microns)‏ Any object at a temperature above absolute zero (0 K= -273 C) emits light. If we plot the amount of light versus wavelength it has a characteristics shape called a blackbody curve

20. The advantage of looking for planets in the Infrared l Planets in the habitable zone will mainly radiate infrared radiation. Wavelength Brightness

21. The difficulty of detection: Brightness differences l Earth, seen from a distance, is ten billion times fainter than the Sun. - In the infrared it is only ten million times fainter. l Jupiter in the infrared is a million times fainter than the Sun. l Earth around a nearby star will be 0.1 arcsec away (this is about the resolution limit of HST)‏ Trying to see a Planet around another star is like trying to detect a firefly circling a distant spotlight

22. Contrast Demonstration

23. Motivation for Direct Detection Planets Verification, mass determination – For known radial velocity planets we could verify existence and determine the mass Look for long-period planets – Separations >5 AU require a long period of observations for detection (>10 years) Learn about size, temperature, and composition of planets – Most information about a planet can be obtained from direct detection. Zodiacal Dust Disks Disks are the “smoking gun” of a planetary system – Material is cleared away on short timescales requiring large planetessimal bodies as reservoirs for transitory dust around mature stars. Dust may prevent terrestrial planet detection – A dust disk brighter than the solar system’s would add background and force longer integration times. If the dust is irregular it may mimic a planet signal.

24. Extrasolar Giant Planet Spectra IR spectra by Adam Burrows and team predicting the flux of known planets around 55 Cnc

25. Nulling Interferometry: Concept Cause starlight to interfere destructively in order to suppress the “glare” of the star. ConstructiveDestructive Detector Telescope 1 Telescope 2 Light from star

26. First Telescope Demonstration of Nulling Nulling at the MMT Nature 1998; 395, 251. Ambient Temperature Optics

27. The Bracewell Infrared Nulling Cryostat (BLINC)

28. BLINC has been in routine use for mid-IR observations with the MMT and Magellan since June 2000. Primary targets have been young, luminous (A-type) stars with significant IR excess. We are also starting to look at older (main sequence) stars for evidence of zodiacal dust emission. BLINC at the MMT and Magellan Telescopes from N. Smith et al., 2002

29. HD 100546: A young Solar System? Constructive Null ε Mus HD 100546 Disk approximately 25 AU in diameter. disk shape is consistent with Near- Infrared scattered light images. Disk similar in size at 11 microns and 24.5 microns. Consistent with an inner hole? (Bouwman et al.) 10.3 microns (~silicates) 11.7 microns (~PAH) 12.5 microns (continuum) position angle null

30. MMT Adaptive Optics Adaptive optics (AO) are needed to allow high- precision suppression of the starlight. Deformable secondary system integrates the AO system into the telescope, keeping the reflections to a minimum for good IR sensitivity. Deformable secondary mirror of the MMT during engineering tests in June 2002 (courtesy Francois Wildi). IC 2149 at 2.1 microns. (courtesy Patrick A. Young, Donald W. McCarthy, and the ARIES-MMTAO team.)

31. The MMT AO System

32. [7736-12] Astronomical Telescopes and Instrumentation 2010, June 27-July2, San Diego, 2010 Paper 7736-12 Intensities between open and closed loop rescaled for displaying purposes. LBT InfraRed Test Camera images: H band, 10mas/pixel scale The object: HD 124085, K0, R=7.5, I=6.9, H=5.8, Triple Star The atmosphere: seeing 0.6arcsec V band Elevation 58..64 FLAO parameters: 1 KHz, 30x30 subaps, 400 corrected modes Results: SR H 65%..73% 3.2 arcsec

33. From the MMT to the LBT The MMT provides a testbed for developing nulling interferometry in preparation for the LBT. It will provide sensitive nulling observation of the very nearest stars The Large Binocular Telescope will have both better sensitivity and resolution for exo-system searches MMT LBT 6.5 m 8.4 m 22.8 m

34. Why combine the light? LBT Deformable Secondary Mirror LBTI installed on the telescope LBTI uses both mirrors to create a 23 m telescope The AO system increases the resolution by 20x. Combining the telescopes increase the resolution by another 3x

35. The Large Binocular Telescope The Large Binocular Telescope is currently being constructed on Mt. Graham in Arizona. It is a collaboration of Arizona, Germany, Italy, Ohio State University, and the Research Corporation. When completed it will be the world’s largest single-mount telescope.

36. LBT Structure in 2002 The telescope enclosure is complete on Mt. Graham in Arizona LBT enclosure on Mt. Graham

37. LBT Structure Construction The structure is being assembled inside the enclosure

38. LBT under Construction

39. The LBT Interferometer (LBTI)

40. The Main Components of LBTI UBC= Universal Beam Combiner NIL= Nulling Interferometer for the LBT NOMIC= Nulling Optimized Mid-Infrared Camera UBC=Universal Beam Combiner NIL=Nulling Interferometer for the LBT NOMIC=Nulling-Optimized Mid-Infrared Camera

41. 41 Large Binocular Telescope Interferometer (UA) The beginning of high resolution science

42. What might we find out?

43. Earth: A pale blue dot Voyager 1 mapped the outer planets in the 1970-80s. On its way out of the solar system in 1990 it turned around an image of our Earth. At this point it was 27 AU (0.0004 light years) from the Earth. The Earth appears as a single blue pixel in the image.

44. Other planets imaged by Voyager 1 Even at this distance the planets are almost indistinguishable. Jupiter appears to be slightly bigger than the Earth (it is really 10 times bigger) but by how much is difficult to tell.

45. A more recent view from the Cassini mission Even from 10 AU the Earth is essentially a point of light, bluish in color. We can barely see the Moon in a blow-up of the image. A planet around a nearby star is nearly a million times further away. It will be even fainter. The angle between a planet and its parent star will be very small.

46. How can we learn more about other planets? Planets will appear as points of light We will not be able to see things like clouds or continents We will see their brightness vary for different wavelengths.

47. What could we see once we “null” the star? 5 micron image15 micron image 25 micron image We may soon be able to see planets around other stars as single points of light. The information about these planets will come from their brightness at each wavelength. Simulated Images of what we might see

48. Spectrum of 4 planets in the infrared

49. Deriving Planetary Information: Size l The planets are unresolved points of light. l The bigger they are the more light they will emit. - If one planet is twice the size of another it would appear four times as bright.

50. Which planet is the largest?

51. Deriving Temperature The light peaks at a particular wavelength which depends on an object's temperature. Hotter objects have a peak brightness that is at shorter wavelength − You might say it is “bluer”

52. Which planet is the hottest?

53. Deriving Atmospheric Composition l The gases in an atmosphere will absorb the infrared light being emitted by the planet's surface. l Absorption lines tell us what is in the atmosphere around a planet. l The amount of transmission is less for a more abundant gas. - Levels in the drawing are marked relative to the amount in Earth's atmosphere. 0.33 1.0 3.0 10.0 0.33 1.0 3.0 10.0 CO2 CH4 H2O O3

54. Which planet has ozone?

55. How can we learn more about other planets? CO 2 -> planet has atmosphere H 2 O -> planet is habitable O 3 -> planet has life! We will see their brightness vary for different wavelengths.

56. Recap: Spectra of Planets l We can derive several parameters from the spectra of these planets: - Size of the planet l Mass - Temperature l can compare to distance from star. - Albedo - Greenhouse effect? - Atmosphere Constituents l Surface conditions l Habitability l Life

57. Points to Take Away: Other planetary systems exist! They appear to be relatively common (~10% of stars have them). We are just beginning to develop the capability to “see” other planetary systems. Earth-like planets are much more difficult to detect, but are the ultimate goal of most of this research. Jupiter-like planets are being pursued as a good signpost of other systems. The systems we have found so far indicate we may have more diversity in other systems than we expected. Are we unique?

58. Interesting Websites LBT:http://www.lbto.org LBTI:http://lbti.as.arizona.edu MMT: http://www.mmto.org NASA: http://planetquest.jpl.nasa.gov http://planetquest.jpl.nasa.g

59. BACK UP SLIDES

60. Original Bracewell nulling interferometer concept Target: Jupiter in solar system twin at 10 pc, 0.5 arcsec Method;two element interferometer in space, set for destructive interference for star, constructive for planet. Spin about line of sight to modulate planet signal Wavelength:40 um req’d element separation7 m (planet on 1st constructive peak) planet / star @ 40 mm1/5000 sin 2 leak1/400,000 planet / nulled star80 Bracewell proposed space infrared nulling interferometer to detect thermal emission of giant exo-planets (Nature, 1978)

61. Planet Modulation from Bracewell and McPhie, Icarus, 1979 1. The pitch of the sin 2 fringes is chosen so the first constructive peak is at the expected planet location. The leak due to the finite star disc is then minimized 2. The interferometer is rotated at frequency w during an observation so the planet is alternately transmitted and blocked, appearing as a signal at 2w.