Buscando a vida fora da Terra: Al

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AGA 0316 AULA 16
Buscando a vida fora da TerraAlém do Sistema
Solar
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Extrasolar planets

• Extrasolar planetsExoplanets 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)

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Which type of star?
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Exoplanets(Oct 2013 1040 DESCOBERTOS)
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Hertzsprung-Russell (HR) Diagram
http//observe.arc.nasa.gov/nasa/space/stellardeat
h/stellardeath_1ai.html
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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

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59 planets
11 planets9 systems 1 multiple
8 planets7 systems 1 multiple
1 planet
321 planets 274 systems 33 multiples
7 planets 4 systems 2 multiple
Extra-Solar Planets Catalog (http//exoplanet.eu/c
atalog.php). Last update 30/05/2009
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How to detect exoplanets? 1) Direct
detection 2) Astrometry 3) Microlensing 4)
Velocitometry 5) Transits
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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 gt 100,000,000
for a Jupiter-like planet in the Visible
100,000 for a Jupiter-like planet in the IR ?
interferometric/coronagraphic techniques
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Direct detection planet around star Fomalhaut
(25 l-y from the Sun)
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Other examples of direct detection
Beta Pic
AB Pic
Hubble image of possible exoplanet TMR-1C (NASA)
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Four planets around HR 7899 (Palomar)
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Methods for the detection of exoplanets 3)
Gravitational microlensing (Einstein effect)
Some dozens exoplanets discovered with this
method (Mpl Atm)
Planet OB05390
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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 3rd law ?
Mpl Porb
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PROBLEM with the velocitometry method Described
by Newton's law F G x Mstar x Mplanet
distância2 ?? BIAS detected mainly planets
more massives nearer to their hosts stars
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Detection by velocitometry method the system of
Gliese 581
Discovery of 3 planets April, 2007(Udry et
al.) 2009-2012 discovery of other planets, not
all confirmed yet
Planet Mass Period Distance
Gliese 581b 15 MEarth 5,4 d 6 millions km
Gliese 581c 5 MTerra 13 d 11 millions km
Gliese 581d 15 MTerra 84 d 38 millions km
Udry et al planet d at ZH? ?
?
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GLIESE 581 PLANETARY SYSTEM?
No atmosphere
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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. ? Rpl Porb
Transit of VENUS June 6, 2012
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Method of planetary Transits
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d
d ? Rpl2 / Rstar2
CoRoT star
Porb interval between 2 eclipses
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Satellites observing transits
CoRoT
KEPLER
Europe Brazil
NASA
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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)
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The launch of CoRoT (Dec 26th, 2006) (launch no.
1735 of SOYUZ without a failure)
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Exoplanets methods of detection
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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
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Exoplanets Astrobiology
The Habitable Zone (HZ) liquid water
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Outra possibilidade interessante Rocky Moon
orbiting a Jupiter in HZ
There are many Jupiters discovered in HZ
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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 (gt 100
billion ? many planets)
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THE EXOPLANET ZOO
Number of planets in the Milky Way 400 billion
Number of Earth-like planets in the Milky Way
100 billion
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NUPESC Ago 2012
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The KEPLER CoRoT legacy (www.seti-setr.org)
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Period 20hs Mass ? 7 MEarth
CoRoT 7-b, the first planet discovered with
Earth-like density
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?
? CoRoT 7b
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NUPESC Ago 2012
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How Will We Know A Planet Supports Life?
Look for evidence of oxygen
Look for liquid water
Look for signs of biological activity (methane)
Analyze the reflected light from the planet to
see if the planet has an atmosphere
And Rule Out Other Explanations?
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NIMS Data for the Earth (from Galileo)
(A band)
But credit Toby Owen for pointing this out
(1980)
Sagan et al. (1993)
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NIMS data in the near-IR

• Simultaneous presence
• of O2 and a reduced
• gas (CH4 or N2O) is
• the best evidence for
• life
• Credit Joshua Lederburg
• and James Lovelock for
• the idea (1964)

Sagan et al. (1993)
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Wavelength
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Thermal IR spectra
Source R. Hanel, Goddard Space Flight Center
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Possibility of remote detection of life
Explore the contrast star/planet in thermal IR
(Des Marais et al. 2002, Segura et al. 2003)
Window at 8-12 µ m Tsurface
Porto de Melo et al., Astrobiology, 2006
gt 106
H2O 6.3 µm 12 µm band
O3 9.6 µm
CH4 7.7 µm
CO2 15 µm
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Darwin (ESA) 2022?
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Darwin summary

• ESAs 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
• O2 (or O3) and CH4 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

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An Integrated Program of Planet Finding Science
(NASA)
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KEPLER
Survey of distant stars for Earths
Optical signs of habitable worlds
KECK
TPF-C
Survey of nearby stars for dust and giant planets
Mid-infrared signs
of habitable worlds
SIM
Masses and orbits of large terrestrial planets
TPF-I
ARE THERE OTHER HABITABLE WORLDS?
LBTI
JWST
PLANET CHARACTERIZATION Planet chemistry in
visible and infrared
Presence of water
Radius
Surface gravity and temperature
Atmospheric conditions
Biomarkers
ARE THERE OTHER SOLAR SYSTEMS LIKE OUR OWN?

• Young Jupiters
• Transit Follow-up
• Debris Disks

PLANET DETECTION Nearby giant planets
Young, hot Jupiter's
approved
2005
2010
2015
2020
2025
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OUTRAS MISSÕES PROGRAMADAS PARA 2020-2030 SOBRE
EXOPLANETAS (NASA, ESA) PLATO (ESA), ECHO
(ESA), TESS, SIM, JWST ALMA (Atacama Large
Milimmeter Array), MATISSE (espectro-interferômetr
o, IV), etc...
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