Buscando a vida fora da Terra: Além do Sistema Solar AGA 0316 AULA 16

Extrasolar planets Extrasolar planets=Exoplanets= planets around stars other then the Sun Planets are the environments for the origin and evolution of life. Giordano Bruno: “There are countless suns and earths all rotating around their suns in exactly the same way as the seven planets of our system..” (1584) First confirmed planet – 51 Pegasi on October 1995 by Mayor and Queloz (1995)

Which type of star?

Exoplanets (Oct 2013: ~ 1040 DESCOBERTOS)

Hertzsprung-Russell (HR) Diagram

Prospects for finding habitable planets Best candidates are F, G, and early K-type stars, i.e., stars not too different from the Sun Early-type stars (blue stars) –High UV fluxes –Short main sequence lifetimes Late-type stars (red dwarfs) – M-class –Tidal locking –Lots of flares

321 planets 274 systems 33 multiples 11 planets 9 systems 1 multiple 8 planets 7 systems 1 multiple 7 planets 4 systems 2 multiple Extra-Solar Planets Catalog ( Last update: 30/05/ planets 1 planet

9 How to detect exoplanets? 1) Direct detection 2) Astrometry 3) Microlensing 4) Velocitometry 5) Transits

10 Methods for detection of Exoplanets 1) Astrometry: changing on spatial star position  exoplanet detection Inconclusive and marginal. 2) Direct (imaging) detection: only for BIG and sufficiently distant planets: weak contrast Contrast Star-Planet: > 100,000,000 for a Jupiter-like planet in the Visible ~ 100,000 for a Jupiter-like planet in the IR  interferometric/coronagraphic techniques

11 Direct detection: planet around star Fomalhaut (25 l-y from the Sun)

12 Beta Pic AB Pic Hubble image of possible exoplanet TMR-1C (NASA) Other examples of direct detection

13 Four planets around HR 7899 (Palomar)

14 Methods for the detection of exoplanets 3) Gravitational microlensing (Einstein effect) Planet OB05390 Some dozens exoplanets discovered with this method (Mpl ~Atm)

15 Methods for the detection of exoplanets 4) Velocitometry : stellar radial velocity variations   presence of unseen body Many hundred exoplanets discovered by this method Radial velocity variations + Kepler's 3 rd law  Mpl ; Porb

16 PROBLEM with the velocitometry method Described by Newton's law: F = G x M star x M planet distância 2 ►► BIAS: detected mainly planets more massives & nearer to their hosts stars

17 Detection by velocitometry method: the system of Gliese 581 PlanetMassPeriodDistance Gliese 581b 15 M Earth 5,4 d6 millions km Gliese 581c 5 M Terra 13 d11 millions km Gliese 581d 15 M Terra 84 d38 millions km  Udry et al: planet d at ZH? ? Discovery of 3 planets: April, 2007(Udry et al.) : discovery of other planets, not all confirmed yet

18 GLIESE 581 PLANETARY SYSTEM? No atmosphere

19 Methods for the detection of exoplanets 5) Transit method: detection of the tiny eclipse caused by the passage (transit) of a planet in front of its star.  R pl ; P orb Transit of VENUS June 6, 2012

20 Method of planetary Transits

21 CoRoT star Porb = interval between 2 eclipses d  R pl 2 ⁄ R star 2 d

22 Satellites observing transits CoRoT KEPLER Europe + Brazil NASA

23 KEPLER and CoRoT have found tens of multiplanetary systems The moment of the eclipse by one planet is perturbed by the presence of other planet(s)

24 The launch of CoRoT (Dec 26 th, 2006) (launch no of SOYUZ without a failure)

25 Exoplanets: methods of detection

26 The Habitable Zone (HZ) Definition: region around a star where the temperature on the surface of an eventual planet or moon can afford the presence of liquid water. Conditions: the position and width of the HZ depends on the presence and composition of the atmosphere (greenhouse effect - GE). On EARTH: GE raises temperature by ~32 °C

27 Exoplanets & Astrobiology The Habitable Zone (HZ): liquid water

Outra possibilidade interessante: Rocky Moon orbiting a Jupiter in HZ There are many Jupiters discovered in HZ

29 Planets and Astrobiology Most favorable cases: F-G-K stars (similar to the Sun): stability and evolution time Hot (blue) stars: too much UV radiation and short MS evolution time Cold (red dwarf) stars: energetic explosions (flares) and tidal lock problem. But: 85% of stars in Milky Way are red dwarfs (> 100 billion  many planets)

30 THE EXOPLANET ZOO Number of planets in the Milky Way: ~ 400 billion Number of Earth-like planets in the Milky Way: ~ 100 billion

NUPESC Ago

The KEPLER + CoRoT legacy ( )

33 CoRoT 7-b, the first planet discovered with Earth-like density Period ~20hs Mass  7 M Earth

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37NUPESC Ago 2012  =  CoRoT 7b

How Will We Know A Planet Supports Life? Look for evidence of oxygen Look for liquid water Analyze the reflected light from the planet to see if the planet has an atmosphere Look for signs of biological activity (methane) And Rule Out Other Explanations? 17

NIMS Data for the Earth (from Galileo) Sagan et al. (1993)* *But credit Toby Owen for pointing this out (1980) (‘A’ band)

NIMS data in the near-IR Sagan et al. (1993) * Simultaneous presence of O 2 and a reduced gas (CH 4 or N 2 O) is the best evidence for life * Credit Joshua Lederburg and James Lovelock for the idea (1964)

Wavelength

Thermal IR spectra Source: R. Hanel, Goddard Space Flight Center

Possibility of remote detection of life Explore the contrast star/planet in thermal IR (Des Marais et al. 2002, Segura et al. 2003) > 10 6 Porto de Melo et al., Astrobiology, 2006 CO 2 15 μm O μm CH μm H 2 O 6.3 μm + 12 μm band Window at 8-12 μ m: T surface

Darwin (ESA) 2022?

Darwin summary ESA’s Darwin mission may eventually be able to locate Earth-sized planets around other stars and take either visible or thermal-IR spectra of their atmospheres O 2 (or O 3 ) and CH 4 have absorption bands in both wavelength regions that may be used as potential indicators of extraterrestrial life But, We need other bio-indicators for reduced, early-Earth type atmospheres

An Integrated Program of Planet Finding Science 1 KECK LBTI SIM JWST TPF-C TPF-I KEPLER Optical signs of habitable worlds Masses and orbits of large terrestrial planets Mid-infrared signs of habitable worlds Survey of distant stars for Earths Survey of nearby stars for dust and giant planets ARE THERE OTHER HABITABLE WORLDS? ARE THERE OTHER SOLAR SYSTEMS LIKE OUR OWN? PLANET DETECTION Nearby giant planets Young, hot Jupiter's PLANET CHARACTERIZATION Planet chemistry in visible and infrared Presence of water Radius Surface gravity and temperature Atmospheric conditions Biomarkers Navigator Program Young Jupiters Transit Follow-up Debris Disks Delayed 3 yrs Overcost Cancelled (NASA) approved

OUTRAS MISSÕES PROGRAMADAS PARA SOBRE EXOPLANETAS (NASA, ESA) PLATO (ESA), ECHO (ESA), TESS, SIM, JWST ALMA (Atacama Large Milimmeter Array), MATISSE (espectro-interferômetro, IV), etc...