Three planets orbiting the nearby young star HR 8799 Christian Marois Herzberg Institute of Astrophysics

B. Macintosh, T. Barman, B. Zuckerman, I. Song, J. Patience, D. Lafreniere & R. Doyon

Pasadena AAS, June 2009 Searching for faint objects near bright objects

Burrow Select young & nearby stars to minimize contrast

The first ADI Survey

No detection (Lafreniere et al 2007) The 2nd ADI survey

Remove “late-type” bias Focus an young nearby “massive” stars IR excess Low in HR diagram

Johnson et al. 2007 RV of evolved A-stars HR 8799 Characteristics The 2nd ADI survey

A5V star

V~6

39 pc (130 ly)

Pegasus

Lambda Boo, Gamma Dor and Vega-like star Discovery made with Gemini North with Altair/Niri

Gemini N, Altair/NIRI &10s K-band

ADI processing Voyager 1 (43 AU) 18 cm diameter Keck 2 (130 ly), 10m diameter

Neptune

8 200 000 AU A bunch of “archive recoveries”

Keck 2004 HST 1998 Subaru 2002

Marois et al 2008 Lafreniere et al 2009 Fukagawa et al 2009

2 others in prep.

A search for a wide companion

Lowrance et al. 2005 Close & Males 2009 Multi-band photometry @ Keck

HR 8799 age? HR 8799 Age Estimation Low in the HR diagram, under Pleiades.

Galactic Space motion consistent with being young - between TW Hya and Pleiades

Lambda Boo & Gamma Dor stars generally considered young.

Massive debris disk - lower probability at older ages.

Isolated field star. HR 8799 age = 30-160 Myr Mass, radius & Teff estimations from cooling tracks The 3 planet’s colors are more consistent with Pleiades low mass Bright ~11MJup objects and 2M1207b than field BDs.

Physics untested - No Blue Faint Red corresponding objects in the field. Planetary System Formation Solar system

Niel Brandt

Solar system formation leftover vs HR 8799 Spitzer IR excess, dust at ~10 AU (asteroid belt?) Chen et al. 2006 IRAS/ISO IR excess, dust at ~100 AU (Kuiper belt?) Rhee et al. 2007 Spitzer resolve dust emission, dust at ~1000 AU (Oort cloud?) Lu et al. No. 2, 2004 DUSTY DEBRIS DISKS AS SIGNPOSTS OF PLANETS 743

a star of age P a few hundred million years with a similarly 5 massive planet on a wide orbit would have  k 10À . Spitzer 6 should generally be capable of detecting  as small as 10À . Thus, if the dust-planet connection is as strong as we suggest, then Jupiter-mass planets on wide orbits will rarely, if ever, be detected around young stars that lack Spitzer-detected far-IR excess emission. The same may be true for Saturn or even Neptune mass planets, although these, of course, will be much Fig. 8.—Same as Fig. 1 harder to detect. 3. CONCLUSIONS Table 1 should be observed with AO and at what wavelength. Indeed, an AO system has been commissioned on the VLT only Recent imaging observations and analysis of structure in the within the past year, and Gemini North and South and Subaru dusty debris disks that surround a handful of nearby stars have had no or only rudimentary AO systems. suggest that they possess planets on wide orbits (tens of AU). That said, for a given star/dust angular separation (col. [10] Thus, dusty stars, whether imaged or not, are excellent targets in Table 1), planet detectability is maximized by observing the for planet searches. Young stars with cool dust make the best youngest, closest stars to Earth. For example, a 2 MJ planet targets for adaptive optics and HST imaging programs. Older will fade by 5–6 mag, in an absolute sense and also relative to stars and those with somewhat warmer dust might be better the brightness of its star, at the H and K bands as it ages from investigated with precision radial velocities. While the ear- 10 to 100 Myr. Similarly, a planet 50 pc from Earth will be liest searches of the IRAS catalogs revealed mostly A-type 3.5 mag fainter than a comparably warm one only 10 pc away Vega-like stars, which are not suitable for study by the (while the star/planet contrast is independent of distance). precision radial velocity technique, a majority of stars in Then there is stellar spectral type to consider. A planet of Table 1 are of later spectral types. given mass, age, and semimajor axis will be harder to detect Looking toward the future, one anticipates that Spitzer will close to an intrinsically luminous A-type star than one of search for dusty debris at all nearby stars that have been K type. However, if more massive planets, perhaps with identified as very young (e.g., Zuckerman et al. 2001a; Song larger semimajor axes, form near the relatively more massive et al. 2003). Since the presence of cool dust would point stars, then this might more than compensate for the unfavor- toward the existence of planets on wide orbits accessible to able contrast ratio. In any event, because AO systems (unlike adaptive optics, it is important that the Spitzer programs HST/NICMOS) are not well suited to detection of extended include measurements with the 160 m filter. objects, near-infrared light scattered by dust, even for stars with large , is very unlikely to hamper planet detection. Both observation (Spangler et al. 2001; Metchev, Hillenbrand, & Meyer 2004) and theory suggest that, on aver- We thank Murray Silverstone for information regarding the age, young stars will have a dustier ‘‘Kuiper Belt’’ than old relative positions of IRAS 12 and 60 m sources and M. Jura, stars. On the basis of the mass of Neptune, the mass ( 3 MNep) E. Becklin, and B. Macintosh for helpful comments. This of the proposed planet on a wide orbit at  Eri, and thedecrease research was supported by a NASA grant to UCLA and by of  with time indicated in Figure 2 of Spangler et al. (2001), NASA’s Astrobiology Institute.

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July 2004

July 2004

PM

July 2008

Star slow rotation HR 8799bcd Characteristics

Separation Period Temperature Radius Mass HR 8799 (AU) (years) (K) (RJup) (MJup)

b 68 ~460 820 1.30 7

c 38 ~190 1000 1.25 10

d 25 ~100 1000 1.20 10

Circular 60 Myr face-on HR 8799bcd vs Radial Velocities

Previous ADI GKM survey = NO DETECTION

~335 exoplanets known, 309 by RV - limited to ~5 AU.

RV: 31 multi-planet systems, only 10 >= 3 planets (only ~3%)

Planets are probably more likely around more massive stars.

Multi-planet systems are also probably more likely at wide separations. Dynamic Analysis Fabrycky & Murray-Clay 2009 Not perfectly face-on & not perfectly circular Non-resonance cases = masses need to be lower (< 2Mjup) 4:2:1 resonance 2:1 resonance for c & d: some cases stable for age

4:2:1 resonance: stable up to ~20 MJup & 60 Myr.

Younger age / model over predict mass / 4:2:1 resonance Dynamic Analysis Gozdziewski & Migaszewski 2009

Heavy mutual interactions

Most likely 1:2:4 resonance

Lower masses?

1:2:4 system may be unstable in a few 100 Myr. Dynamic Analysis Reidemeister et al. 2009

Dust & planets analysis.

Nearly face-on circular orbits (20< i < 30 degrees)

Lower mass, younger age (<50 Myr) lower than 7-10 MJup

Asteroid belt (10 AU) & Kuiper belt > 100 AU.

Dust & planetesimals stable for planet masses at location found by IR measurements. GPI Imaging of HR 8799 10s

20 minutes (ADI) 10s Conclusions

HR 8799, first directly image of a multi-planet system. First at separation similar to the outer planets of our solar system.

Peculiar star: Lambda boo, Gamma Dor & Vega-like.

Cooling tracks: ~7-10 MJup from 25-70 AU, twice the SS size. ~800-1000K and 1.2 RJup. Supported by color - look like 2M1207b

Evidences ~face-on orbits/~circular orbits/~coplanar/ star view ~ by the pole - formed in a disk.

Dynamic simulations = lower masses & 4:2:1 resonance.

More to come...

Gemini Observatory/Lynette Cook