To Boldly Go? Interstellar Destinations: Nearby Potentially Habitable Worlds

To Boldly Go? Interstellar Destinations: Nearby Potentially Habitable Worlds

To Boldly Go? Interstellar Destinations: Nearby Potentially Habitable Worlds AAPT Regional Meeting March 21, 2014 Edward Guinan Dept. Astrophysics & Planetary Science. With Scott Engle, Larry Dewarf & Gal Matijevic Students: Evan Kullberg, Allyn Durbin, Anna Marion, Connor Hause & Scott Michener Talking Points • Introduction: Finding Exoplanets & Planet Census • Living with a Red Dwarf Program: Summary • of Findings • • Nearby Stars and Exoplanetary Systems • The red dwarf / planetary system GJ 581 Habitable Planets? So far best choice. • To Boldly go? Interstellar Travel: Summary & Prospects Planet Hunting Finding Exoplanets very short summary For student projects: www.planethunters.org Many Exoplanets (400+) have been detected by the Spectroscopic Doppler Motion Technique (now can measure motions as low 1 m/s (3.6 km/h = 2.3 mph)) Reflex Radial Velocity Motion 20 of Sun Produced by Jupiter Typical 10 Error K 13 m/s 0 i = 90è -10 (orbit seen Radial Velocity (m/s) 11.86 yrs edge-on) -20 0 5 10 15 20 Time (Years) Semi-Amplitude, K, of 2pG ⅓ m sin i 1 _ K = p Radial Velocity induced P (M + m )⅔ √1 – e2 by a companion: * p Exoplanet Transit Eclipses Rp/Rs ~ [Depth of Eclipse] 1/2 Kepler Mission See: kepler.nasa.gov February 2014: Kepler Mission Discovers 715 New Planets (in multiple Planetary systems) Total confirmed Exoplanets: 1700 (Mar 2014) New Large Earth-size Planets discovered Around Nearby Red Dwarf Stars March 2014 Toumi et al. 2014 MNRAS Study indicates that 1/5 red dwarfs host Habitable planets Breaking News: March 2014 Habitable planets common around red dwarf stars (Toumi et al. 2014) Exoplanet Census (Febuary 2014) Confirmed exoplanets: 1700+ (Doppler / Transit) (Confirmed Systems: 900+ Jan. 2013 AAS Meeting) Exoplanet Candidates: 3538 - orbiting 2000+ stars (Mostly from the Kepler Mission) 03/2014 Other unconfirmed (mostly from CoRot)Exoplanets ~186 Potentially Habitable Exoplanets: 12 (March 2014) (Unconfirmed ~ 27) Estimated Planets in the Galaxy ~50-100 Billion! Most expected to be hosted by red dwarf stars Number of known planets with life: 1 so far. From NASA Kepler data it has been estimated that our Galaxy has least ~8.8 billion Earth-sized planets orbiting Inside Habitable Zone of solar-type stars. (~50 billion HZ Planets hosted by more numerous red dwarf stars – Toumi et al. 2014) ~50% of stars host planets ~25% solar type stars ~20% red dwarf stars are expected to have Habitable Earth-size Planets! Toumi et al 2014 NASA Kepler Mission 21 ly 22 ly 620 ly 42 ly 36 ly 12 ly 49 ly 21ly 12 ly dM3 dM1.5 G5V K2.5V K5V G8V M3.5V dM3 G8V 4-6 Ga 5-8 2: 3-5 4-7 5-8 TBD 4-6 5-8 Living with a Red Dwarf NSF/NASA Program Villanova University www.astronomy.villanova.edu/livingwithareddwarf/opener.htm The original “Living With a Red Dwarf” Program Logo Stellar Distribution Within 10 pc 250 Data Obtained from the RECONS Program www.chara.gsu.edu/RECONS/ 239 200 150 # of Stars 100 50 44 4 6 21 16 18 0 A F G dK dM L,T,P WD Spectral Type M-stars comprise ~75% of nearby stars Physical properties of dM0-dM8 stars compared to the Sun. Habitable Zones dG Outer HZ Edge 2AU dK Outer HZ Edge dM 1AU 0.8AU Inner HZ Edge Earth-equiv Pos. Outer HZ Edge 0.5AU 0.2AU Inner HZ Edge Earth-equiv Pos. 0.3AU 1AU Earth-equiv Pos. 0.14AU Inner HZ Edge 0.1AU * Earth not drawn to scale Liquid Water Habitable Zones for mid-dM, -dK and -dG stars. Note that the HZs of dM-stars are located <0.3 AU from host star. Primary Goals (since 2006): Determine physical properties of red dwarfs that are important to habitability of hosted planets: Ages, Luminosity, X-UV-IR irradiance (as function of age and Spectral Type), Flare properties: Irradiance/ flare frequencies Establish Rotation-Age-Activity relations (M0-M6V) 150 stars in primary sample / ~40 with ages. Ages from memberships in clusters, moving groups, wide binaries kinematics-metal relations (high velocity stars = Pop II) Stellar Astrophysics of dM stars: Study magnetic dynamos for fully convective stars – Coronae, Chromospheres, Activity Cycles/ starspots etc. Supported by grants from NSF/ NASA (HST/Chandra) Evolution of F-G-K-M Stars Over Time 4 1.4 M.; F4-5 1.0 M.; G2 “stable” lifetime “stable” lifetime 3 ~2.5 Gyr ~8 Gyr 2 L/L . 1 log 0 “stable” lifetime >20 Gyr 0.7 M.; K2-3 -1 “stable” lifetime >40 Gyr 0.4 M.; M1-2 -2 0.0 5.0e+9 1.0e+10 1.5e+10 2.0e+10 Age (years) Examples of Photometry of Red Dwarf Stars ( ~85 nearby dM stars now with reliable period) 11.74 GJ 4247 RCT Photometry DS Leo (GJ 410) APT Photometry 0.35 11.76 0.37 11.78 0.39 11.80 0.41 11.82 0.43 V-mag V-mag 11.84 0.45 dM4 dM2 11.86 0.47 0.447-d 13.9644-d 11.88 Age = 200 ± 20 Myr Castor Group Age = 400 ± 150 Myr UMa Group 0.49 11.32 0.89 GJ 669A RCT Photometry GJ 176 APT Photometry 11.34 0.91 11.36 0.93 11.38 0.95 11.40 0.97 V-mag V-mag 11.42 0.99 dM4 dM2.5 11.44 20.43-d P = 37.7-d 1.01 11.46 Age = 600 ± 150 Myr Hyades Group Age = 2 ± 0.5 Gyr (HR 1614 Moving Group) 1.03 0.0 0.5 1.0 1.5 0.0 0.5 1.0 1.5 Phase Phase Determining Far-UV Irradiances with Age - An example: 2.0e-11 FUSE O VI 1032, 1038 A Region 1.5e-11 AD Leo (100 Myr) 1.0e-11 26x 5.0e-12 Proxima Cen (5.8 Gyr) 0.0 1030 1032 1034 1036 1038 1040 Comparison of the FUV O VI emissions in a young (AD Leo) and middle-aged (Proxima Cen) dM star. 100 Myr dG-K-M-star IUE Comparison 60 ) EK Dra (G1 V: 1 AU) 2 V833 Tau (K2 V: 0.5 AU) 50 AD Leo (M3.5: 0.15 AU) DNA Damage 40 Ly-a FUV NUV Atmospheric Cutoff (no radiation penetrates to ground level) 30 20 Mg II 10 EK Dra V833 Tau AD Leo 0 Flux within Habitable Zone (ergs/s/cm Flux within Habitable 1000 1500 2000 2500 3000 3500 Wavelength Comparison of FUV/NUV fluxes expected in the Habitable Zones of young G-M stars. Note the low NUV fluxes for dM stars. Some Results (Engle and Guinan 2011) dM Stars Rotation Over Time dM Stars X-ray Activity Over Time 100 29 b y = y + a*x y = 16.004x Castor 0 80 Proxima y0 = 40.913 Cen UMa G 130-6 a = -13.09 Hyades 60 28 b = 0.044 LHS 26 HR X 1614 40 LHS G 111-72 LP 672-2 Eri C 40 GJ 176 26 log L log HR 1614 Proxima G 121-21 27 Cen G 148-6 K-stars G 111-72 Activity Cycle 20 UMa GJ 1015 G-stars Old Disk Rotation Period (Days) & Halo Castor 0 Hyades (3x) 26 0 1 2 3 4 5 6 0 2 4 6 8 10 12 14 Age (Gyr) Age (Gyr) Nearest Stars < 16 LY 1 LY ~10 x 1012 km ~6 Trillion miles Alpha Centauri Star System 4.3 LY 1.0 LY = 5.9x1012 miles (=5.9 trillion miles) = 9,625 billion km α Cen Star System D= 4.3 LY ; Age ~ 5 +/ 0.6 Gyr a = 23 AU (not to scale) P = 79.9 years eccentricity = See: Dewarf et al. 2010 Astrophys. J. α Cen A α Cen B α Cen C G2 V; K1 V; M5 V; 5800K 5300K ~3040K 1.10 Mo 0.91 Mo ~0.12 Mo R = 1.22 Ro 0.84 Ro 0.145 Ro L= 1.52 Lo 0.50 Lo 0.00014 Lo <HZ>:1.25AU ~0.74 AU ~0.07 AU Proxima Cen Rot: ~22 d 36.2 d 82.6 d Porb ~ 0.5-1.5 Myr Alpha Cen A & B is an eccentric 79.9-yr binary system- Spectroscopic Doppler studies indicate no Planets (upper mass limit of >2.0 Mj). Many theoretical studies indicate that planets are unlikely due to binary star tidal interactions…But … Earth size Planet found around the Nearest Star - Alpha Centauri Alpha Centauri B and its planet -- European astronomers have discovered a planet with about the mass of the Earth orbiting a star in the Alpha Centauri system -- the nearest to Earth. The results published in Nature on 17 Oct. 2012. Alpha Cen Bb Exoplanet P = 3.236 d A = 0.04 AU K = 0.51+/- 0.04 m/s Min.Planet mass (Mp): 1.13 Mearth T = 1800- 2200 K Dunusque et al. Nature 2012 Proxima Centauri ---Red Dwarf (M5V) Distance= 4.24 LY; Mass = 0.12 Mo, R = 0.14 Ro; T = 3,050 K; L = 0.00014 Lsun, HZ = 0.04-0.10 AU Proxima Centauri Compared to the Sun and Jupiter From our study Proxima is 5-6 BY old and. has a rotational period of 83-d & 5% spot covered ~1 major flare/30 hrs Anna Marion Scott Engle Barnard’s Star (2nd nearest star system) Dim Red dwarf – ( at 6 LY) The proper motion of Barnard's Star corresponds to a relative lateral speed ("sideways" relative to our line of sight to the Sun) of 90 km/s.

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