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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