M-Dwarfs: the Fast Track to Inhabited Exoplanets

M-Dwarfs: The Fast Track to Inhabited Exoplanets

David Charbonneau, Harvard University Exoplanet Exploration Program Analysis Group 7, 6 January 2013 The Fast Track to Finding an Inhabited Planet The Usual Cabal Cabal: a group of persons secretly engaged in artifices and intrigues to bring about an overturn or usurpation Recent Alumni (past 3 years): Sarah Ballard grad student Sagan fellow, U. Washington Jacob Bean Sagan fellow Asst Prof. U. Chicago Cullen Blake grad student Asst Prof., U. Pennsylvania Christopher Burke postdoc Scientist, NASA Ames Jessie Christiansen postdoc Scientist, NASA Ames Jean-Michel Desert postdoc Asst Prof., U. Colorado, Boulder Heather Knutson grad student Asst Prof., Caltech Philip Nutzman grad student Postdoc, UC Santa Cruz

Current Group Members: Jonathan Irwin (Astrophysicist, Smithsonian Astrophysical Observatory) Francois Fressin (postdoc) Graduate Students: Zach Berta, Jason Dittmann, Courtney Dressing, Elisabeth Newton, Sukrit Ranjan

We acknowledge support from the NSF through an A&A Research Grant, NASA through the Spitzer, HST, Discovery & Kepler Participating Scientist programs, the David and Lucile Packard Foundation. The Usual Cabal Cabal: a group of persons secretly engaged in artifices and intrigues to bring about an overturn or usurpation Recent Alumni (past 3 years): Sarah Ballard grad student Sagan fellow, U. Washington Jacob Bean Sagan fellow Asst Prof. U. Chicago Cullen Blake grad student Asst Prof., U. Pennsylvania Christopher Burke postdoc Scientist, NASA Ames Jessie Christiansen postdoc Scientist, NASA Ames Jean-Michel Desert postdoc Asst Prof., U. Colorado, Boulder Heather Knutson grad student Asst Prof., Caltech Philip Nutzman grad student Postdoc, UC Santa Cruz

Secondary Eclipse See thermal radiation and reflected light from planet disappear and reappear

Transit Only transiting planets See radiation from star offer direct estimates of the masses and radii. transmitted through the planet’s atmosphere As a result, studies of the atmospheres are more penetrating. Transits Allows Studies of the Atmospheres That Are Not Possible for Non-Transiting Planets

Transit See radiation from star transmitted through the planet’s atmosphere Perhaps the GMT and JWST can do for terrestrial exoplanets what ground-based telescopes and Spitzer/Hubble did for hot Jupiters and Neptunes.

The only challenge: We do not yet know where to point these observatories. M Dwarf Properties --sizes to scale--

0.07 < mass < 0.6 Msun

M = 0.12 Msun

R = 0.18 Rsun T = 2900 K

G2 M3 Earth M = 1 M sun M = 0.45 Msun R = 1 R sun R = 0.45 Rsun T = 5800 K T = 3500 K Slide by Jacob Bean wd 20

O 0

B 0

A 4

F 6

G 20

wd 20

O 0

B 0

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K 44

M 246

Data from RECONS, image courtesy Todd Henry Zachory K. Berta MIT Brown Bag Astrophysics 10 December 2012

G2V 1.0 R⊙ super-Earth planets M5V 0.25 R⊙ in the habitable zone 2 R⊕, 7 M⊕, Earth-like insolation transit depth = 0.03% 0.5%

Doppler wobble = 60 cm/s 5 m/s

transit probability = 0.5% 1.5%

orbital period = 1 year 2 weeks

Nutzman & Charbonneau (2008) The MEarth Project Nutzman & Charbonneau 2008; Irwin et al. 2008

MEarth

• Using 8 X 40cm telescopes, we are surveying the 2000 nearest low-mass stars for planets as small as 2 REarth orbiting within the habitable zone.

• MEarth is different: Monitor stars sequentially & detect transits in progress

• We moved into an existing building on Mt Hopkins, Arizona September 2008

• Expanding to southern hemisphere (Chile) in 2013

The MEarth Project Nutzman & Charbonneau 2008; Irwin et al. 2008

• Using 8 X 40cm telescopes, we are surveying the 2000 nearest low-mass stars for planets as small as 2 REarth orbiting within the habitable zone.

• MEarth is different: Monitor stars sequentially & detect transits in progress

• We moved into an existing building on Mt Hopkins, Arizona September 2008

• Expanding to southern hemisphere (Chile) in 2013

Zachory K. Berta MIT Brown Bag Astrophysics 10 December 2012

symbol area depth ∝ photon noise

GJ1214b is easy to observe

Berta, Charbonneau, et al. 2012 –53–

GJ1214b is <570K

Kepler planet Jupiter 10 candidates

e 4 Neptune / R p R GJ1214b is 2.7R⊕ 1 Earth Planet Radius (Earth radii) Planet Radius (Earth

500 1000 1500 2000 2500 T [K] Planet Equilibriumeq Temperature (K) Batalha et al. (2012) Fig. 9.—Z. RadiusBerta versus equilibrium temperature for each of the planet candidates in the B10 catalog (blue points), the B11 catalog (red points), and this contribution (yellow points). Horizontal lines marking the radius of Jupiter, Neptune, and Earth are included for reference. Also included for reference are vertical lines marking the inner and outer edges of the Habitable Zone as deﬁned by Kaltenegger & Sasselov (2011) as well as the equilibrium temperature for an Earth-Sun analog (middle line) under the same assumptions as those described in Section 7.3. Why is GJ1214b so big?

big dense core small dense core

puffy hydrogen + thick Adams et al. (2008), helium Rogers & Seager (2010), water-rich Nettelmann et al. (2011) envelope? envelope? modeling GJ1214b’s WFC3 transmission spectrum

models from Miller-Ricci (Kempton) & Fortney (2010) Berta, Charbonneau, et al. 2012 modeling GJ1214b’s WFC3 transmission spectrum

water fractions above 20% (70% by mass) are good ﬁts to models from Miller-Ricci (Kempton) & Fortney (2010) the WFC3 spectrum Berta, Charbonneau, et al. 2012 Slide Redacted!

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correction, rotated and offset for clarity. Bottom panel: the λ = 1.5 micron GJ1214b’s Transmission Spectrum from WFC3

Zachory K. Berta MIT Brown Bag Astrophysics 10 December 2012 If GJ1214b transited a Sun- like star, its transit depth would be 0.06%. divide-oot visit throughout.

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shows the transmission spectra inferred from each of unity, indicating that the ﬂux residuals show 9 σ ), we combine the three values of Top panels: spectroscopic transit light curves for GJ1214b, before and after the

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For most spectroscopic bins, the inferred value of

of thespectrophotometric three light curves visits, from whichFor as they the were derived. well ﬁnalFigure transmission as spectrum the (shown as black points in each wavelength bin byweighting averaging proportional them to

within 1 scatter commensurate with(1400–1900 that ppm predicted across wavelengths). fromlated No photon noise evidence is noise for seen corre- criterion as in for any the white of light the curves (see bins, Figure as judged by the same

The Astrophysical Journal Figure 9. combined transmission spectrum of GJ1214btop (black panel circles is aligned with to error its bars), respective along wavelength with bin the in spectra the measured panel below. for Colors each denote visit (colorful circles). Each l MEarth can detect transits in two ways.

example: (post-discovery) light curves of GJ1214b 1) By phase-folding old data and looking for periodic events (as most

surveys do). (mag.) Flux

2) By reducing data in low-cadence start of trigger! realtime and triggering high-cadence follow-up of

ongoing possible events. Flux (mag.)

This magniﬁes sensitivity to long-period planets.

Charbonneau, Berta, et al. (2009), Berta et al. (2011), Berta et al. (2012) MEarth’s discovery light curve for GJ1214b

MEarth marginalizes over corrections for systematics Figure 1: The original MEarth discovery light curve of GJ1214b, shown as function of time (left) and phased to the planet’s 1.6 day and period (right). My MISS MarPLE frameworkstarspot searches for planets by generatingvariability a simultaneous probabilistic model (blue swaths) for instrumental/ telluric systematics (dominating the top panels), stellar variability (middle panels), andwhen planetary searching transits for (bottom panels). planetary transits in light curves of nearby M dwarfs.

Charbonneau, Berta, et al. (2009), Berta et al. (2011), Berta et al. (2012) MEarth’s discovery light curve for GJ1214b

Charbonneau, Berta, et al. (2009), Berta et al. (2011), Berta et al. (2012) Zachory K. Berta MIT Brown Bag Astrophysics 10 December 2012 MEarth’s sensitivity to exoplanets: (from 2008-2012, in a phased search with 7.5σ threshold, accounting for uncertainties in stellar parameters + binarity)

window function (expected planets) MEarth Sensitivity MEarth

Berta et al. (in prep.) Zachory K. Berta MIT Brown Bag Astrophysics 10 December 2012 MEarth’s sensitivity to exoplanets: (from 2008-2012, in a phased search with 7.5σ threshold, accounting for uncertainties in stellar parameters + binarity)

If every star hosts (expected planets) one GJ1214b (1.6 days, 2.7R⊕), MEarth Sensitivity MEarth MEarth should have found 20 transiting.

If every star hosted a habitable zone Neptune MEarth should have found 4. Berta et al. (in prep.) MEarth Data Release #1, 1 September 2012 http://www.cfa.harvard.edu/MEarth/

all M dwarf light curves (fall 2008 - summer 2011)

1.2 million observations spread across 1255 unique stars Please use these data! The need for new RV capability

Slide courtesy Jacob Bean The need for new RV capability

normal RV measurements @ 10 pc Sun V=4.8 M0 V=9.0 M8 V=18.7

Slide courtesy Jacob Bean The need for new RV capability

normal RV measurements more ﬂux in the red/NIR

Slide courtesy Jacob Bean So, how can we push from GJ1214b to smaller and cooler worlds? • We need to know the true radii and masses of the target stars.

• We need an estimate of the rate of occurrence of the planets we seek.

• We need excellent students to figure this out.

The next few slides will highlight recent unpublished work from Jason Dittmann, Courtney Dressing and Zach Berta. So, how can we push from GJ1214b to smaller and cooler worlds? • We need to know the true radii and masses of the target stars.

• We need an estimate of the rate of occurrence of the planets we seek.

• We need excellent students to figure this out.

The next few slides will highlight recent unpublished work from Jason Dittmann, Courtney Dressing and Zach Berta. MEarth Parallax Results: 5 slides redacted

Dittmann, Charbonneau et al. in prep MEarth: Star Spots Can be Useful for Determining Rotation Periods

Irwin et al. (2011 ApJ) MEarth Gyrochronology (Irwin et al. 2011)

Kinematically Old

Kinematically Young

Published study contained only the 41 stars with parallaxes. However, there are hundreds of detected rotation periods and now we have parallaxes for all! So, how can we push from GJ1214b to smaller and cooler worlds? • We need to know the true radii and masses of the target stars.

• We need an estimate of the rate of occurrence of the planets we seek.

• We need excellent students to figure this out.

The next few slides will highlight recent unpublished work from Jason Dittmann, Courtney Dressing and Zach Berta. The Kepler M Dwarfs

Ten Slides Redacted

Dressing & Charbonneau (submitted to ApJ) Zachory K. Berta MIT Brown Bag Astrophysics 10 December 2012 How do we increase MEarth’s “planets/year”?

“less is more” observe half the stars, twice the photons (= double up telescopes)

Berta et al. (in prep) Take Home Message • The Nearest Habitable Planet Orbits an M-dwarf within 8 pc • There is likely a transiting example within 30 pc • We may characterize the atmospheres of super-Earths with JWST and ELTs: This is big aperture science. – Studies are compelling as we will know the masses & radii – We must locate these planets – Doing so required characterizing the stars • Development of ground-based detection techniques is essential to realize the full potential of NASA exoplanet missions. NASA knows how to do technology development. – Planets Discovered by NASA Missions (Kepler; future missions) must be characterized from the ground (RV, atmospheric studies) – Planets Discovered from the ground have been prime targets for atmospheric studies by NASA Missions (HST; SST; JWST)