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Lauren Farmer
5 years ago
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The Ancient History of Comparative Planetology There

Devarian, JPL false and damnable... G. Galilei (b.

suns and countless earths Giordano Bruno (b.

2 The Ancient History of Comparative Planetology There are infinite worlds both like and unlike this world of ours Epicurus (c. 300 BCE) (died painfully 269 BCE) From Mike Devarian, JPL false and damnable... G. Galilei (b. 1564) (life imprisonment 1633) "There are countless suns and countless earths Giordano Bruno (b. 1584) in De L'infinito Universo E Mondi (burned at the stake in Campo dei Fiore, Rome, 1600)

4 Ultimate goal: To find Earth-like planets, if they exist, and to search for evidence of life So, how do we do that?

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9 !"#$M&'G*4&-#?%3/3(&-#$M<(/# /#;#/$*;#'$/*45$-31#$.(&/#. &4>$"&.$&(-#>$&.$&$7/&4#-&'<$-"#'1*.-&-$>D'345$1D("$*)$$+&'-".$"3.-*'<I GD3/>.$D7$&.$-"#$(/31&-#$(**/. Z-$&/.*$#4.D'#.$-"&-$-"#$/3RD3>$T&-#'$"&G3-&G/#$W*4#$&'*D4>$-"#$%D4$&4> *-"#'$.-&'.$3.$)&3'/<$T3>#$P'*D5"/<$KH\?=H\$N:$)*'$-"#$%D4Q

10 ZAMS habitable zone Kasting et al., Icarus (1993) The habitable zone is considered to be reasonably wide as a consequence of stabilizing feedbacks between atmospheric CO 2 and climate Bad things happen, though, to planets around stars much different from the Sun --F and A stars: high stellar UV fluxes, short main sequence lifetimes --Late K and M stars: tidal locking, stellar flares, initial volatile inventories?

11 +,-'&.*/&' 7/&4#-.$T3-"34$-"#$Y] 0D4#I$JKK^ M*D'-#.<$*)$6&''#4$`3//3&1. N77'*,31&-#/<$JKa$*)$A4*T4$#,-'&.*/&' 7/&4#-.$&-$-"3.$-31#$T#'# T3-"34$-"#$Y]$ N//$*)$-"#.#$7/&4#-.$&'#$P7'*G&G/<Q$5&.$*'$3(#$53&4-. M&4$T#$>*$-"#$.&1#$-"345$)*'$'*(A<$7/&4#-.b

$8/3#.# U\=$.<.-#1 %7#(-'&/$-<7#E$Xcd$ PKHc=$X! I$KHK=cU$C! Q c$7/&4#-.$>3.$

12 8/3#.# U\=$.<.-#1 %7#(-'&/$-<7#E$Xcd$ PKHc=$X! I$KHK=cU$C! Q c$7/&4#-.$>3.(*;#'#>$ G<$'&>3&/$;#/*(3-<E &$PN:Q X&..$PX " Q G$ KHK^= e=uh_ ( KHK[c euhk_ > KHJUc e\hc V#)HE$%H$:>'< #-$&/HI$NON$PJKK[Q PZ1&5#$)'*1$`3AA37#>3&Q

13 The Gliese 581 planetary system compared to our own FH$%#/.3. #-$&/HI$NON$PJKK[Q

14 Tentative conclusions for the Gliese 581 system * Gliese 581c (> 5.1 M " ) is probably not habitable Wikkipedia is wrong! Stellar flux is 30% higher than that for Venus Gliese 581d (>8.3 M " ) could conceivably be habitable, but it is probably an ice giant Near the (poorly determined) outer edge of the HZ But, the good news is that searching for habitable planets around M stars using ground-based RV looks doable! f %#/.3. #-$&/HI$NON$PJKK[Q f ;*4$g/*" #-$&/HI$NON$PJKK[Q

15 Finding M-star planets using transits Presentation to the ExoPTF by Dave Charboneau (February, 2007) Relative radii: Sun 1 Jupiter 0.1 M star Earth 0.01 Thus, the light curve for Earth around a late M star is about as deep (~1%) as for Jupiter around a G star The HZ around an M star is also close in! transits are reasonably probable!'& $53&4-$7/&4#-$y6$jkl^u\g P6H$M"&'G*44#&D$#-$&/H$N7H$0HI$JKKKQ

Possible problems for planets around M stars Tidal locking But this can probably be overcome by atmospheric and oceanic heat transport Lack of magnetic field!

16 Possible problems for planets around M stars Tidal locking But this can probably be overcome by atmospheric and oceanic heat transport Lack of magnetic field! atmospheres may be removed by flares and sputtering (H. Lammer et al., Astrobiol., 2007) Initial deficiency in volatiles due to smaller orbits, hotter accretion environment, more energetic collisions (J. Lissauer, Ap. J., 2007) 8VZSE$8'#&-$Z1&5#.$34$SN%N "--7EhhTTTH)&4G*<H(*1h.(3#4(#h

26 !#''#.-'3&/$9/&4#-$F34>#'$P!9FQ Visible or thermal-ir?!9f?m! =K =K!9F?Z! =K [ Contrast ratio: in the visible 10 7 in the thermal-ir Resolution: % & '/D Required aperture: ~8 m * in the visible 80 m in the IR M*D'-#.<E$M"&.$g#3("1&4I$09C f$6#7#4>345$*4$<*d' (*'*4&5'&7"$&4>$*4$( "

28 !9F?Z$P*'$6&'T34QE$F'##?)/<345$ZV$ 34-#')#'*1#-#' This idea has now evolved into a free-flying interferometer, similar to ESA s proposed (but now postponed) Darwin mission Advantages: good contrast ratio, excellent spectroscopic biomarkers Disadvantages: needs cooled, multiple spacecraft

29 !"#'1&/$ZV.7#(-'& C3)#b %*D'(#E VH$Y&4#/I$8*>>&'>$ %7&(#$F/35"-$M#4-#'

30 !9F?ME$d3.3G/#h4#&'?ZV$ (*'*4&5'&7" It may be easier, however, to do TPF in the visible, using a single telescope and spacecraft Advantages: single spacecraft and telescope Disadvantages: high contrast ratio between planet and star

33 Visible Spectrum of Earth C3)#b Integrated light of Earth, reflected from dark side of moon; Rayleigh, chlorophyll, O 2, O 3, H 2 O. Ref.: Woolf, Smith, Traub, & Jucks, ApJ 2002; also Arnold et al. 2002

34 M*4(/D.3*4. Y&G3-&G/#$W*4#.$&'*D4>$FI$8I$&4>$#&'/<$2$.-&'.$&'#$ '#/&-3;#/<$T3>#$$! +&'-"?/3A#$7/&4#-.$135"-$$G#$ (*11*4 X$.-&'.$&'#$5**>$-&'5#-.$)*'$.#&'("345$)*'$"&G3-&G/#$ 7/&4#-.$34$-"#$4#&'$)D-D'# N$.7&(#?G&.#>$&.-'*1#-'<$13..3*4$(*D/>$"#/7$7&;#$ -"#$T&<$)*'$!9F$G<$3>#4-3)<345$-&'5#-$.-&'. Z4-#'#.-345$G3*1&'A#'.$&'#$&;&3/&G/#$&-$G*-"$;3.3G/#$ &4>$-"#'1&/?ZV$T&;#/#45-". SN%N$."*D/>$(*113-$-*$>#;#/*7345$-"#$'#RD3'#>$ -#("4*/*53#.$&4>$-*$)/<345$.*1#$-<7#$*)$!9F$13..3*4$ T3-"34$-"#$4#,-$=U?JK$<#&'.

35 V#)#'#4(#. 2&.-345I$0HFHI$6H9H$`"3-13'#I$&4>$VH!H$V#<4*/>.H$Y&G3-&G/#$W*4#.$ &'*D4>$1&34$.#RD#4(#$.-&'.H$Z(&'D. =K=E$=K\?=J\$P=LLcQ 6H$0H$6#.$X&'&3.I$XH$Y&'T3-I$2H$0D(A.I$0H$2&.-345I$6H$C34I$0H$CD434#I$0H$ %("4#3>#'I$%H$%#&5#'I$`H$!'&DGI$&4>$SH$`**/)#I$V#1*-#$.#4.345$*)$ 7/&4#-&'<$7'*7#'-3#.$&4>$G3*.354&-D'#. *4$#,-'&.*/&' -#''#.-'3&/$7/&4#-.I$ N.-'*G3*/*5<$JI$=Uc?=\=$PJKKJQ %#5D'&I$NHl$2'#/*;#I$2HI$0H$FH$2&.-345I$6H$%*11#'/&--I$dH$X#&>*T.I$6H$ )/D,#.$*4$+&'-"?/3A#$7/&4#-.$&'*D4>$*-"#'$.-&'.I$N.-'*G3*/*5<$cI$_\L?[K\$ PJKKcQ %#5D'&I$NHI$0H$FH$2&.-345I$dH$X#&>*T.I$XH$M*"#4I$0H$%(&/*I$6H$M'3.7I$VH$ NH$YH$gD-/#'I$&4>$8H$!34#--3I$g3*.354&-D'#. )'*1$+&'-"?/3A#$7/&4#-.$ &'*D4>$X$>T&').I$N.-'*G3*/*5<$UI$[K_?[JU$PJKKUQ All available at:

Where are the Boundaries of the Habitable Zone? James Kasting Department of Geosciences Penn State University

Where are the Boundaries of the Habitable Zone? James Kasting Department of Geosciences Penn State University Talk outline Part 1: What are the basic planetary requirements for life, and where should we