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Nuno C. Santos [email protected]

Constraining planet structure from stellar chemistry

Nuno C. SantosInstituto de Astrofísica e Ciências do Espaço, PortugalDepartamento de Física e Astronomia, Fac. Ciências, University of Porto, Portugal

With: V. Adibekyan, C. Mordasini, C. Dorn, L. Noack, S. Barros, E. Delgado-Mena, O. Demangeon, S. Sousa, et al.


Constraining planet structure from stellar chemistry

Nuno C. SantosInstituto de Astrofísica e Ciências do Espaço, PortugalDepartamento de Física e Astronomia, Fac. Ciências, University of Porto, Portugal

With: V. Adibekyan, C. Mordasini, C. Dorn, L. Noack, S. Barros, E. Delgado-Mena, O. Demangeon, S. Sousa, et al.

T˙ Daily Planet06 SEP 2017

Dry law for

distracted

astronomers!

By ANONYMOUS

An independent but anonymoussource reports rumours that as-tronomers in a PLATO conferencewill have no access to wine in the con-ference dinner if they do not pay at-tention to late afternoon talks.

Reuters

International

Moose Count

Underway

By BOB O’BOBSTON

The UN-sponsored InternationalMoose Census got o↵ to a flyingstart today with hopes for an increasein the worldwide moose populationcompared to last year’s disapointingfigures. Among the traditional earlyreporters were Egypt, returning fig-ures of six moose, a twenty percentincrease on 2011’s figures of five, andUruguay whose moose population re-mains stable at eleven.

According to Robbie McRobson,head of the UN Moose Preserva-tion Council, worldwide moose num-bers are expected to grow markedlyon last year due to the traditionalmoose strongholds of Canada and theUnited States, with the larger de-veloping moose ecologies also poised

to make gains. The largest percent-agege increase in moose will likelycome from China’’, says McRobson,The Chinese government has investedheavily in moose infrastructure overthe past decade, and their committ-ment to macrofauna is beginning topay dividends’’. Since 2004 China hasexpanded moose pasture from 1.5%of arable land to nearly 3.648% andmoose numbers are expected to riseto 60,000 making China a net mooseexporter for the first time. This isgood news for neighbouring Mongo-lia, a barren moose-wasteland whoseinhabitents nonetheless have an insa-tiable desire for the creatures. The in-crease in Beijing-Ulanbataar trade isanticipated to relieve pressure on therelatively strained Russian suppliers,but increase Mongolia’s imbalance oftrade with its larger neighbour.

Historically the only competitorto China in the far eastern moosemarkets has been Singapore but thetiny island nation is set to report anet loss, expecting a decrease of morethan five percent on last year’s 50,000moose counted. The head of Singa-pore’s Agency for Agriculture, Jing-Feng Lau, explained to an incredu-lous Singaporean parliament yester-day that bad weather had contributedto this season’s poor showing, mostnotably when a cargo of 150 moosewere swept out into the Indian oceanin a monsoon.

Yet again the global demand formoose will be met largely by theUS and Canada. The recession-hitStates is taking comfort in its moosegrowth figures with gross productionexpected to break 700,000 and net ex-ports to grow by 2%. The worldwidedominance of Canada shows no signsof abating though with this year’smoose population expected to matchlast year’s record figures of one hun-dred million billion.

Europe’s rise as an internationalmoose power will slow slightly thisyear as a response to the EuropeanUnion’s move towards standardisingthe European moose. Stringent qual-

ity controls are holding back the de-velopment of the eastern europeanpopulations compared to last yearwhen they contributed significantlyto europe’s strong growth figures.Norway, which is not an EU memberbut has observer status, strengthedin numbers relative to the Euro areawith numbers of Norweigian moose,known locally as elk’’ expected to risefor the tenth consecutive year, partic-ularly thanks to a strong showing inthe last quarter.

As moose season reaches its close,researchers world wide are turning toscience in an attempt to boost nextyear’s figures. NASA stunned thescientific community today with theannouncment of their discovery thatthe moon is significantly smaller thanpreviously believed. This conclusion,which is the conclusion of a ten-year collaborative project, will haveprofound implications for the moosecommunity as the gravitational fieldis now known to be of the rightstrength to support moose in orbit.

According to John Johnson, headof the NASA Moon Sizing Experi-ment the first delivery of moose intolow moon orbit could be achieved asearly as the third quarter of next year.The technology to nurture moose inspace is available now’’, he said, ’’allthat is needed is political will’’.

Granny wins

World Wrestling

Championship

By ROY MCROYSTON

Records were smashed inNicaragua’s World Wrestling Cham-pionship last night as 78-year-oldMaud Johnson, grandmother of five,became the first woman for fifty-sixyears, and the oldest competitor ever,to claim the gold medal. She walkedaway with her million dollar share of


Planet host stars spread a large metallicity range

Planets with Mass<30MEarth

[Fe/H] varies by a factor of 16!


Stellar composition in the Galaxy

Different stars present different abundance ratios

Thick disk

Thin disk

Abundance ratios vary

factor of ~2!

Adibekyan+ (2012)

Metal-richThick disk?


Stellar composition in the Galaxy

Different stars present different abundance ratios

Thick disk

Thin disk

Abundance ratios vary

factor of ~2!

Adibekyan+ (2012)

Metal-richThick disk?


(Adibekyan et al. 2012; see also Haywood 2008)

Planet frequency: 12.3+-4.1%

Planet frequency: 2.2+-1.3%

Metal-poor planet hosts: a preference for thick disk


Planets around a variety of Galactic “populations”

(Kepler-444, Age=11.2 Gyr!!! - Campante et al. 2015)

(HD175607, [Fe/H]=-0.62, thick disk - Mortier et al. 2016)


Different stellar abundances => different planets?

See also: Delgado-Mena et al. (2010), Carter-Bond et al. (2013), Alibert et al. (2015), Thiabaud et al. (2015), Dorn et al. (2015, 2017), Santos et al. (2015), Adibekyan et al. (2016)

Simulated planets considering different C/O ratios


What do we know from our Solar System?

Solar system planets: Earth, Venus, Mars, and meteorites all have “solar” relative abundances of Fe, Mg, and Si - e.g. Sanloup et al. 1999

Can we use stellar Fe, C, O, Mg, Si to predict the composition of rocky exoplanets? (e.g. Dorn et al. 2015, 2017)


Rocky exoplanets: same composition?

Dressing+2015, Motalebi+2015


Rocky exoplanets: same composition?

Dressing+2015, Motalebi+2015

Rocky planets: follow the Earth composition line!

Is this expected from stellar composition?


Santos+2015

Rocky exoplanet composition: a simple model

Iron mass fractionWater mass fraction


Santos+2015

Input measured stellar C, O, Si, Fe

Rocky exoplanets: same composition!


Predicting rocky planet composition in the Galaxy

Sample of solar neighbourhood stars (HARPS sample, Adibekyan et al. 2012)

371 stars with well determined and very reliable values of C, O, Mg, Si, Fe

All stellar parameters are homogeneous (SWEET-Cat)

Santos+2017, subm.


SWEET-Cat (http://www.astro.up.pt/resources/sweet-cat)

(Santos+ 2013; Andreasen+ 2017)

http://www.astro.up.pt/resources/sweet-cat/


Predicting rocky planet composition in the Galaxy

Thin disk stars (like the Sun): planets should be mostly “Earth like”

Thick disk: lower iron-to-silicate ratios => bigger mantles?

Thick disk planets should have more water!

SunSun

Santos+2017, subm.


In brief…

Stellar chemistry is providing important clues for planet composition and structure!

Planets formed in different galactic regions/populations/ages may have different composition

We may be able to predict (at least statistically) planet composition from stellar chemistry

Constraints for models of planets detected by PLATO (also CHEOPS/TESS)

Implications for plate tectonics? and life?


Thank you!

Questions?

Acknowledgements:

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