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 = 90 -10 (orbit seen Radial Velocity (m/s) 11.86 yrs edge-on)
-20 0 5 10 15 20 Time (Years) Semi-Amplitude, K, of 2 G 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- 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
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. The 10.3 seconds of arc it travels annually amounts to a quarter of a degree in a human lifetime, roughly half the angular diameter of the full Moon.[18]
Barnard Star: Animation from http://www.hwy.com.au/~sjquirk/images/film/barnard. html Choi et al. (2012) - No evidence of planets (lower mass limit > 2 Me) hosted inside the Habitable Zone (HZ) of Barnard’s Star
Wolf 359 (CN Leonis) 7.79 LY (3rd nearest star system) No planets found (yet)
Red Dwarf (M6 V) Very Active Flare Star Teff = 2800 K L = 0.001Lo; M=0.08Mo Age: X-ray (<2 Gyr) Rotation Period (v(rot) ~ 3 km/s) Wolf 359 (CN Leonis) 7.79 LY (3rd nearest star system) No planets found (yet)
A FAMOUS STAR IN STAR TREK NEXT GENERATION WHY? Red Dwarf (M6 V) Very Active Flare Star Teff = 2800 K L = 0.001Lo; M=0.08Mo Age: X-ray (<2 Gyr)
Wolf 359 Famous in Science Fiction: In Star Trek NG as the site of the defeat of the Federation by the Borg (2367; TNG/ BoBW)
Wolf 359 has its own website http://en.wikipedia.org/wiki/Battle_of_Wolf_359 Epsilon Eridani (ε Eri): 2nd nearest Star with a known planet: 3rd mag K2 V star at d = 10.5 LY (so far) to host a planet. Epsilon Eri b; M > 1.5 MJ; a = 3.0 AU , P ~ 7 yrs. But it is very young star system (age: ~600 Myr) & has a significant (& dangerous) debris disk. Could have smaller planets/ but too young for advanced life. tau Ceti Planetary System: Nearest (so far) potentially habitable planets Star: G8.5V d = 11.9 ly P(rot)= 34d (Ca II HK) Age = 5.5-7.5 Gyr (Kullberg et al 2014)
Toumi et al. 2012 2012arXiv1212.4277T 5 possible planets/ 2 or 3 --in/near HZ Tau Ceti Planetary System –five super-Earth planets Super Earths Mass~ 2-10Me; Radius ~ 1.2-2.5 Re R
Gliese 581 Planetary System at ~20.4 LY Two or Three HZ SuperEarth Planets GJ 581 Planetary System
Fig. 5 - Phased reflex barycentric velocities of the host star due to the planets at 3.15days, 5.37days, 12.9days, 32days, 67days, and 433days from the all- circular fit. Red hexagons are from Keck while blue triangles are from HARPS. Gliese 581 Planetary System at ~20 LY (best choice so far) Extended Habitable Zone GJ 581 Planetary System f d c g ? b
e
Substellar Ice Point
X water
Computer simulations of oceans /Temperatures on a Tidally locked planet. (Y. Hu -Astrobiology March 2014) Left frames -white = ice ;blue = water; Colors on right-frames are surface air temperatures. The top images are models without ocean heat flow; The bottom images include heat flow via ocean. Artistic Representation of Exoplanet GJ 581c High Surface Gravity
• Larger life vs. smaller life • Dense life vs. porous life
Image Credit: http://wattsupwiththat.com/2009/03/10/heavy-global-warming-linked-to-gravity/ Interstellar Travel To Boldly Go? http://100YSS.org
Mae Jemison ,MD Star Voyager Interstellar - Human Exploration of Nearby Stars & Planetary Systems
Saving Humanity: Human Settlements on the Moon, Mars and on Planets Around other Stars Earth: The (Only)Home of the Human Species (But for how Long?)
Life could be wiped-out by human or astronomical Catastrophes
All of our eggs are in one basket –the Earth. Life could be wiped out by human or astronomical Catastrophes…. International Space Station (ISS) occupied since November 2000 Next Step- Moon Bases NASA Lunar Crater Observation and Sensing Satellite (LCross Mission finds water on the Moon Space Elevators http://spaceelevator.com Moon Base (2025?) Humans on Mars 2030-2040?
Humans on Mars Fatwa Issued 2030 against-2040? Travel to Mars
Humans on Mars 2030-2040?
Establishing the Mars Base Mars ~2075 Planetary Engineering : Terraforming Mars
World-renowned astrophysicist Stephen Hawking —has said “humanity will face a choice between space colonization and extinction” Interstellar Travel Much more difficult! (Nearest Star- the alpha Centauri System is 4.3 LY (25 trillion miles away)
[1 LY = 5.85 x 1012 miles] How Do We Get There? • Chemical Rockets • Nuclear Propulsion Engines • Anti-Matter Engines • Ramjet Fusion Engines
• Solar Sails • Space Elevators • Physics of the Future?
0.1c 44 yrs Project Icarus Icarus Interstellar: Interstellar Exploration Missions To nearby stars
www.icarusinterstellar.org/ Voyager 1 The first Interstellar Mission NASA: Launched in 1977 Now: 123 AU (~11 billion miles from the Sun) (1 AU = 93 x 106 miles) Voyager 1 and Voyager 2 Crossing the Heliopause Into Interstellar Space Chemical Rockets Hydrogen Bombs Project Orion (nuclear pulse propulsion) In the scheme, advanced in the 1950s, thermonuclear bombs expelled by the spacecraft would explode against a “pusher plate” propelling the ship forward.
Pros: Feasible now but would not use bombs but more sophisticated nuclear fusion pellets. Cons: Massive radiation hazards and dangers Large size/ high cost ($2T) Top speed 0.05 – 0.12 c Designs of Nuclear Fusion Rockets – NASA/DOE Joint DOE and NASA team demonstrates simple, robust fission reactor prototype (Nov. 27, 2012) A team of researchers, including engineers from Los Alamos, has demonstrated a new concept for a reliable nuclear reactor that could be used on space flights. The research team recently demonstrated the first use of a heat pipe to cool a small nuclear reactor and power a Stirling engine at the Nevada National Security Site's Device Assembly Facility near Las Vegas.
A nuclear Stirling engine that generates electricity using more-abundant uranium would reduce the demand for plutonium-238 Nuclear Fusion Interstellar spaceship From Icarus Interstellar Fusion Engines using heavy Hydrogen 3H =Tritium • 2H + 3H -> 4He + n + energy • 17.6 MeV • Half-life of 12.32 years • Radiation leaks
• Maybe collect Tritium from the Moon
Slyuta Bussard Ramjet Fusion
0.2c in one year Anti-Matter Engines
The NASA Institute for Advanced Concepts (NIAC) is funding a team of researchers working on a new design for an antimatter- powered spaceship that avoids this nasty side effect by producing gamma rays with much lower energy From Craig Kolobow Anti-Matter Engines
When Protons + Antiprotons collide, they annihilate transforming into bursts of charged particles (muons) that travel near the speed of light – ideal thrust for an interstellar rocket. Very efficient but magnets must be made to channel the particles in the right direction.
Pros: Extremely efficient , high speed (~10 g of anti-protons to get to Mars) Cons: Long radiators needed to dump the waste heat; gamma radiation dangers require shielding; Collecting enough anti-matter.
Travel speed: Up to ~0.2C Solar Sails
V ~ 0.1 c (if enhanced) Solar Sails Solar Sails
Captured Asteroid Concept Star Voyager Interstellar - Human Exploration of Nearby Stars & Planetary Systems [email protected]
[email protected] Faster than Light (FTL) Propulsion systems Harold “Sonny”White NASA / Propulsion Lab Experiments with hyper-space drives
An Alcubierre warp drive bubble, showing spatial compression ahead of the bubble, and spatial expansion behind (Image: NASA)
Pros and Cons for Interstellar Travel Some CONS: For human travel –huge space ship needed with a very high price: >3 Trillion USD?
Current Lack of Political and Science Motivation
Technology: Many new technologies are needed: New propulsion technologies needed to reach >10% speed of light (67 million mph) / fusion, anti-matter, long-distance communications etc.
Surviving the long duration of the trip: 50 yrs to the nearest star Alpha Centauri (at 10% speed of light) at least 120 yrs and 220 yrs to tau Ceti and GJ 581, respectively with known potentially habitable planets
Pros and Cons for Interstellar Travel Survival of human species in case of a catastrophe for Earth and Solar System / Mars Colony first
Exploration, Inspiration, Curiosity, Discovery, International cooperation, Science/Tech potential
Creating a new space-based economy- a better Earth.
Through reaching for the stars, humanity will incite a new era of thought & capabilities with the potential to transform our culture & technology, heal the Earth & enrich the human experience. Andreas Tziolas (V.P. Icarus Interstellar).
A recent statistical analysis of Kepler Mission exoplanet data indicates ~ 50-100 billion planets in the Galaxy. There should be many (several billion Earth-size planets) - maybe some with life.
T 35 potentially habitable planets within 25 LY expected.
To boldly Go…
THANK YOU. Extra Slides
Star Voyager Interstellar - Human Exploration of Nearby Stars & Planetary Systems
International Space Development Hub (ISDHub), Moffett Field http://www.isdhub.com/hangar-one/
ISDHub is being proposed as a re-use concept for Hangar One. The immense and historic Hangar One at Moffett Field, NASA Ames Research Park, is undergoing its first phase of a rehabilitation program, and re-use strategies have been in the public domain for some time. Battle of Wolf 359
Date 2367 Location Wolf 359 Result Borg victory Belligerents United Federation of Borg Collective Planets Commanders and leaders Admiral Hansen Locutus of Borg Strength 40 ships 1 Borg cube Casualties and losses 39 ships destroyed, 11,000 Unknown killed or assimilated Life on GJ 581c ?
Hot & dry with gravity 2.5x that of Earth.