The planet – stellar chemical composition connection

Jorge Meléndez Departamento de Astronomia IAG - Univ. São Paulo

Ivan Ramirez (Austin), J. Bean (Chicago), P. Baumann, M. Bergemann, K. Lind (MPA),

B. Gustafsson (Uppsala), D. Yong, A. Karakas, M. Asplund, A. Alves Brito (Stromlo),

T. Monroe, M. Tucci Maia (IAG/USP), M. Castro, J.D. do Nascimento (UFRN)

Outline

• Metallicity – giant planet connection

• Lithium: is there a link to planets ?

• Signatures of terrestrial planets

• Signatures of giant planets

• Solar twin planet survey with HARPS at ESO

Sunset in Paracas, Peru (c) www.flickr.com/photos/rodrigocampos/

Metallicity – giant planet connection

Metallicity – giant planet connection

Stars with

giant planets Comparison

sample

Metallicity – giant planet connection

metallicity

1040 FGK-type stars

Lithium: is there a planet connection?

• Li is severely depleted in the Sun

• The Sun is a planet host ...

• Is the solar Li abundance typical of other Suns ?

Meléndez et al. 2010 Ap&SS 328, 193

Orgueil meteorite

CI carbonaceous chondrite

0 1 2 3 4 5

Is the Sun

peculiar in Li? Sun vs. Stars with

Planets (SWP) and

without Planets

Gonzalez et al (2010):

Sun has a Li

abundance 0.7 dex

lower than 50

comparison stars

ʘ

Lithium: is there a planet connection?

Solar twins in M67 (Pasquini et al. 2008)

Sun seems normal in Li with respect to solar twins in M67.

Open cluster with solar age (~ 4 Gyr) and

slightly higher [Fe/H] = +0.03

Randich et al. 2006, Pace et al. 2008)

Lithium: is there a planet connection?

Using solar twins to learn more on the solar Li abundance and Li-depletion

High resolution

(R=65,000) high S/N

(200-450) spectra

McDonald 2.7m

Magellan 6.5m

- Meléndez et al. 2010, Ap&SS, 328, 193

- Baumann, Ramirez, Melendez, Asplund

& Lind 2010, A&A, 519, A87

Lithium in

solar

twins (Meléndez et al. 2010

Ap&SS 328, 193)

The solar Li is “normal” for a 1-solar-mass of solar metallicity at 4.6 Gyr

Yonsei-Yale isochrones

Solar

twins in

open

cluster

and field

stars

The solar Li is

normal for a

1-solar-mass

star at 4.6 Gyr

M67

NGC762 Hyades

Coma Benerices

(Meléndez et al. 2010 Ap&SS 328, 193)

Non-

standard

solar

models

roughly fit

data Montalban &

Schatzmann:

mixing by internal waves

Xiong & Deng: Convective overshooting

+ gravitational settling

Do Nascimento et al: Difussion + grav settling +

rotation-induced mixing

(Meléndez et al. 2010 Ap&SS 328, 193)

What about lithium in

stars with giant planets ?

Conclusion: the Sun has

a normal Li abundance (for a solar-metallicity solar-

age one-solar-mass star)

Planet-host

stars around

solar Teff seem

depleted in Li

Planet hosts

Comparison

You cannot compare apples and oranges ...

comparer des pommes avec des oranges

comparer des pommes et des poires

comparar peras con manzanas

You cannot add pears and apples … No puedes sumar peras con manzanas

Comparing

apples &

apples

Lu

min

os

ity

Li depletion is not enhanced in planet hosts !

Planet hosts

Comparison

Baumann,

Ramírez,

Meléndez, &

Asplund 2010,

A&A, 519, A87

Comparing apples & apples (only stars with similar stellar

parameters within 2-sigma)

Li depletion is not enhanced in planet hosts !

Planet hosts

Comparison

Apples &

apples Baumann,

Ramírez,

Meléndez, &

Asplund 2010,

A&A, 519, A87

Apples &

oranges Israelian et al.

2009, Nature

Conclusion on lithium:

there is no difference in Li abundance between stars with and without planets

Li-7 : no planet connection

The Sun has a normal Li abundance, but what about other chemical elements ?

Are the solar abundances typical of

other Suns ?

Magellan ultra high

precision study of

solar twins - Magellan 6.5m Clay Telescope

& Mike spectrometer

- R = 65,000

- S/N = 450 per pixel

- coverage 340 – 1000 nm

- Solar spectrum: Vesta

- 3 nights of observations

BLUE frame RED frame

Observations of the solar twin 18 Sco

Small part (597-603nm)

of solar twin &

Sun’s spectra

Example of Magellan

spectra (total spectral

coverage

3400 A -1um)

Meléndez et al. 2009, ApJ, 704, L66

Our solar

system is not

host by a

typical ‘Sun’

Δ abundance:

Sun - <twins>

vs. atomic

number Z

Sun typical :

Δ = 0

Sun weird :

Δ ≠ 0

Meléndez et al. 2009

~ 0.08 dex ~ 20%

Correlation is

highly significant

probability ~10-9 to

happen by chance It’s most likely to win

the lottery

Sun’s

anomalies are

strongly

correlated to

dust

condensation

temperature of

the elements!

Meléndez et al. 2009

Dust condensation temperature (K)

Condensation in the solar nebula

Venus

Mercury

Cond

en

satio

n

The late accreted gas in the

convection zone was deficient in

refractories The missing

refractories were

used to form dust,

planetesimals &

terrestrial planets

Melé

nde

z et

al. 2

009

Relation with terrestrial

planet formation:

Tcond trend in meteorites

The abundance

pattern seen in

meteorites is a

mirror-image of the

Sun’s chemical

composition

Alexander et al. (2001)

How much dust-cleansed gas is required to affect

the Sun in this way?

Assume gas accretion until

solar convection zone reached

~ present size (~0.02 Msun):

Refractories depleted in the

Sun: ~2*1028 g ≈ 4 M

Refractories locked-up in

terrestrial planets:

~8*1027 g ≈ 1.3 M

Relation with terrestrial planet formation:

Amount of dust removed from the Sun is

enough to form terrestrial planets

Earth-like

material

SUN

Meteorite-like material

SUN

Earth-like

material

Meteorite-like material

SUN

Could it be a problem in the abundance analysis ?

Is the effect confirmed by other samples ?

Can you really get this unprecedented precision ?

Any problems with the asteroids used ?

Could it be just pollution by a supernova or AGB ?

Perhaps it is just galactic chemical evolution ?

What about random line-of-sight effects ?

Could it be an age effect?

No matter what, I don’t believe it

Are there other solutions besides rocky planets?

Results are almost independent of adopted model atmospheres

As the stars are solar twins, the results do not depend much on the adopted models.

Effect of using different sets of models is only ~0,001 dex

Meléndez et al. 2012, A&A, 543, A29

Yes, the abundance trend is real The abundance

signature is also

seen in other

samples and

using different

instruments and

different asteroids

Our Sun is

indeed

anomalous in

its chemical

makeup Meléndez et al. 2012, A&A, 543, A29

High precision (0,005 dex) is possible !

Analysis of solar spectra using two

different asteroids

shows that it is possible to achieve

a precision of about 0,005 dex !

Meléndez et al. 2012, A&A, 543, A29

Asteroids are suitable for high precision high resolution spectroscopy

Comparison of asteroids of

different spectral types shows

no meaningful trend with

condensation temperature

Juno

Ceres

Chapman, Morrison & Zellner (1975) Meléndez et al. 2012, A&A, 543, A29

There is no line-of-sight (inclination) effect

There are no changes in

the abundances obtained

at different latitudes in the

Sun for both volatile (to

within 0.005 dex) and

refractory (to within 0.002

dex) elements.

Pollution by AGB stars, supernova type II,

supernova type Ia, or hypernova, are not responsible for the

abundance signature

Meléndez et al. 2012, A&A, 543, A29

Also, the abundance signature cannot be explained by age by galactic chemical

evolution effects

The most likely explanation for the

abundance signature seems to be

the formation of terrestrial planets

HIP 56948 : the most likely candidate for hosting other Earths ? Meléndez et al. 2012

Object: the star HIP 56948

Size: same as the Sun

Temperature: same as the Sun

Composition: same as the Sun

Planets: same as the Sun?

ScienceNews, 30/8/2012, Star's

missing elements could signal lurking

small planets: solar chemistry

suggests best places to hunt.

Rádio USP - Revista FAPESP,

6/7/2012, Um outro Sol.

Revista FAPESP, 6/2012, Um

segundo sol.

Veja, 4/5/2012, Astrônomo da USP

revela estrela 'gêmea' do Sol.

Discovery News, 26/4/2012, Sun's

twin discovered ? the perfect seti

target ?

New Scientist, 20/4/2012, Astrophile:

an alien sunrise just like Earth's. Meléndez et al. 2012, A&A, 543, A29

HIP 56948: best solar twin

Comparison

of HIP56948

(red circles)

and the Sun

(solid line)

HIRES spectra

R ~ 95,000, S/N=600

Meléndez et al. 2012, A&A, 543, A29

HIP 56948 is very similar

to the Sun in physical

parameters and chemical abundances

Meléndez et al. 2012, A&A, 543, A29

Abundance pattern of HIP 56948 is compatible with 1,5 Earth masses of Earth-like material (using Earth’s composition from Chambers 2010)

Meléndez et al. 2012, A&A, 543, A29

Planet search for HIP 56948

No giant planets in the terrestrial planet region around HIP 56948 !

Looks promising for hosting Earth-like planets in the habitable zone

Meléndez et al. 2012, A&A, 543, A29

What about the effect of giant planet formation?

16 Cyg: pair of solar analogs

16 Cyg A : no planets

16 Cyg B : giant planet

16 Cyg B (planet-host) is 0,04 dex more metal-poor in all elements (photospheric abundances)!

Was the missing material used to form the giant planet around the

solar analog 16 Cyg B ?

Large Programme: 88 nights at La Silla 3.6m telescope + HARPS spectrograph

Planets around solar twins PI: Jorge Meléndez (IAG/USP)

Collaborators: T. Monroe (IAG/USP)

Australia: Alan Alves Brito, M. Asplund, L. Casagrande

USA: I. Ramírez, J. Bean Germany: P. Baumann, S. Dreizler, K. Lind

© Ana M. Molina at La Silla

Brasil no ESO: primeiros resultados

3af, 14:30 (Salão Pentágono)

Our Large Programme explores the planet – star connection using precise chemical abundances (0,01

dex) and precise radial velocities (1m/s) obtained with HARPS @ 3,6m telescope.

88 nights from Oct 2011 – Oct 2015

Large Programme: 88 nights at La Silla 3.6m telescope + HARPS spectrograph

Current Status - Whole sample observed with VLT and Magellan for high precision (0,01 dex) abundance analysis - About 70 solar twins being observed for planets using HARPS at 1m/s precision - Visitor observing runs in Oct 2011, Feb 2012, April 2012, August 2012, January 2013, …, 2015

© Jorge Meléndez at La Silla

First results from our HARPS planet search around solar twins: Jupiter candidate

O estudo se viabilizou graças ao acesso recém-obtido pelo Brasil às instalações do ESO (Observatório Europeu do Sul).

O governo assinou no fim do ano passado o acordo que torna o país o

mais novo membro do consórcio. Embora o acerto ainda careça de

aprovação do Congresso para entrar em vigor, o ESO já trata o Brasil como

parceiro, concedendo o direito de solicitar tempo de observação nos

telescópios da organização.

Foi por conta disso que a equipe de Jorge Meléndez, peruano que trabalha

no IAG (Instituto de Astronomia, Geofísica e Ciências Atmosféricas) da

USP, conseguiu aprovação num projeto que pode finalmente revelar alguns dos segredos mais bem guardados

sobre os exoplanetas.

Pesquisa sobre procura de planetas com o HARPS é destaque na mídia nacional

Help

most welcome

Pesquisa sobre procura de planetas com o HARPS é destaque na mídia internacional

Melendez and his colleagues are

currently looking for small

planets around roughly 75 solar

twins, using the super-sensitive

HARPS instrument at the La Silla

Observatory in Chile.

Treinamento de estudantes da disciplina de Astrofísica

Observacional no ESO (La Silla) Palestra da Andressa Ferreira

3af, 16:45 (Salão Turquesa)

Conclusions

• Metallicity is related to frequency of giant planets

• Lithium is not related to planets

• Trend with condensation temperature may be related to the formation of terrestrial planets

• Abundances at the 0,01 dex level can give us important information on planets

• Ongoing solar twin planet survey at ESO should allow better studies of the planet-stellar chemical composition connection