proxima b the alien world next door - is anyone...

Proxima b: The Alien World Next Door

- Is Anyone Home?

Edward GuinanDept. Astrophysics & Planetary Science

Villanova University

edward.guinan@villanova.edu

Biruni Observatory 40th Anniversary Workshop12 October, 2017

Talking Points

i. Planet Hunting: Exoplanets

ii. Living with a Red Dwarf Program

iii. Alpha Cen ABC -nearest Star System

iv. Proxima Cen – the red dwarf star

v. Proxima b Nearest Exoplanet

vi. Can it support Life?

vii. Planned Observations / Missions

Planet Hunting:

Finding Exoplanets

A brief summary

For citizen science projects: www.planethunters.org

“There are infinite

worlds both like and

unlike this world of

ours...We must

believe that in all

worlds there are living

creatures and planets

and other things we

see in this world.”

Epicurius

c. 300 B.C

Thousands of years ago, Greek philosophers speculated…

Early Thoughts on Extrasolar Planets and Life

Credit: Charbonneau

First Planet Detected

51 Pegasi – November 1995Mayer & Queloz / Marcy & Butler

Many Exoplanets (400+) have been detected by the

Spectroscopic Doppler Motion Technique (now can

measure motions as low as 1 m/s (3.6 km/h = 2.3 mph))

Exoplanet Transit Eclipses

Rp/Rs ~ [Depth of Eclipse] 1/2

Transit Eclipse Depths for Jupiter, Neptune and Earth for the Sun

1.2% (Jupiter-Sun)

0.15% (Neptune-Sun)0.01% (Earth-Sun)

Kepler Mission

See: kepler.nasa.gov

Has so far discovered

6000+ Confirmed &

Candidate Exoplanets

The Search for Planets

Outside Our Solar

System

Exoplanet Census May 2017

Exoplanet Census (May-2017) Confirmed exoplanets: 3483+ (Doppler / Transit)490+ Multi-planet Systems [April 2017]

Exoplanet Candidates: 7900+ orbiting 2600+ stars (Mostly from the Kepler Mission) [May 2017]Other unconfirmed (mostly from CoRot)Exoplanets ~186+

Potentially Habitable Exoplanets: 51 (April 2017) Estimated Planets in the Galaxy ~ 50 -100 Billion!Most expected to be hosted by red dwarf starsNomad (Free-floating planets) ~ 25 - 50 Billion

Known planets with life: 1 so far.http://phl.upr.edu/projects/habitable-exoplanets-catalog

dK

dM

dG

Outer HZ Edge

Earth-equiv Pos.

Inner HZ Edge

Inner HZ Edge

Earth-equiv Pos.

Outer HZ Edge

Outer HZ Edge

Earth-equiv Pos.

Inner HZ Edge

2AU

1AU

0.8AU

0.3AU

1AU

0.5AU

0.14AU

0.2AU

0.1AU

* Earth not drawn to scale

dK

dM

dG

Outer HZ Edge

Earth-equiv Pos.

Inner HZ Edge

Inner HZ Edge

Earth-equiv Pos.

Outer HZ Edge

Outer HZ Edge

Earth-equiv Pos.

Inner HZ Edge

2AU

1AU

0.8AU

0.3AU

1AU

0.5AU

0.14AU

0.2AU

0.1AU

* Earth not drawn to scale

Liquid Water Habitable Zones for mid-dM, -dK and -dG star Note

that the HZs of dM-stars are located <0.3 AU from the host star.

[1 AU = 150 million km]

Habitable Zones

www.astronomy.villanov

a.edu/livingwithareddwa

rf/opener.htm

Program supported by grants

from NASA (HST & Chandra) &

NSF/RUI.

Living with a Red Dwarf

The original “Living With a Red Dwarf”

Program logo (not NASA approved)

Physical properties of dM0-8 Stars

compared to the Sun.

Living with a Red DwarfDo Red Dwarfs make “Friendly” Host

Stars for Life-Bearing Planets?

Photometry of stars with ages: Rotation,

star spots, cycles: Age-Rotation Relations.

Study effects of X-UV radiation

(photoionization / photo-dissociation) on

hosted planets’ water and atmospheres

(volatiles). X-UV radiation & winds

can erode (eliminate) planet atmospheres.

As part of the Living with a Red Dwarf Program we have

been collecting data on the properties of nearby stars (within

30 Ly; ~245 dM stars) that factor into their suitability as hosts

of Potentially Habitable Planets. These factors include X-ray+

UV emissions, rotation / starspots, flare rates and ages.

Rotation-Age-Log (Lx) Relations (Ages from

Clusters, MGs, Wide Binaries, Space Motions)

Proxima Cen: Prot = 83.4 +/-1.2 d (from 11-yrs of time-series

Photometry. Age: 5.4+/-0.4 Gyr (age from alpha Cen A)

Alpha Centauri Star System 4.3 LY (~25.4 trillion km)

1.0 LY = 5.9x1012 miles (=5.9 trillion miles)= 9,625 billion km

The alpha Centauri star system – compared to

the Sun (depicted to scale)

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 …

alpha Cen Bb ex-Exoplanet

Earth-size planet reported in 2012P = 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 (~1500 – 1900C)

Dunusque et al. Nature 2012

Too Hot for LIFE even

If it existed. (recent studies do not

Support the existence of this planet)

Proxima Centauri-The Nearest

Star: --- Red Dwarf Distance= 4.25 LY;

Mass = 0.123 Mo, R = 0.14 Ro; T = 3050 K; L = 0.0015 Lsun, HZ = 0.03 - 0.08 AU Anglada-Escude’ et al. (2016) report the an

Earth-size HZ planet.

11.1 mag

Proxima Centauri

Red Dwarf Program Star

since 2005M5.5 V star) Compared to the Sun

and Jupiter

From our study Proxima

is ~5.4+/-0.5 Gyr old and has a

rotational period of 83-d & ~15%

spot covered, high levels of

magnetic activity:

~1 major flare/30 hrs.

Nature Letter doi:10.1038/nature19106

A terrestrial planet candidate in a

temperate orbit

around Proxima CentauriGuillem Anglada-Escude’ et al. 2016

Proxima Centauri bAnnounced Aug. 25, 2016

Period Analysis of spectroscopic radial velocity observations

of Proxima from Anglada-Escude’ et al. 2016. A definite

period of 11.186 days is found arising from reflex motion of

1.4 m/s (~5 kph = ~3 mph) from the planet Proxima b

Keplerian fit Proxima bPeriod (d) 11.186

Doppler amplitude: 1.38 m/s [5 km/hr / 3 mph]

Derived quantitiesOrbital semi-major axis, a: 0.049 AU

Minimum mass, mpsini (M⊕) 1.27 (1.10–1.46)

Equilibrium temperature: 234K (-39 C)

With a Greenhouse effect of 50 C: T = +11 C

(similar to Earths mean temperature of 15 C)

Irradiance compared with Earth 65%

Geometric probability of transit about 1.5%

Transit depth (Earth-like density) about 0.5%

[From Anglada-Escude’ et al. 2016]

Proxima b

HZ~ 0.04-0.09 AU

http: //phl.upr.edu/projects/habitable-exoplanets-catalog

Sept. 2016

Comparison of the Spectral X-Near-IR

Irradiance of Proxima b and Earth

(from Ribas et al. 2016)

X-ray EUV FUV NUV UV- VIS - NIR

Ly-alpha

1216 A

Loss of water from X-

UV Stellar radiation

X-UV Radiation

Dissociates water:

H2O -> 2 H + O

FUV radiation ionize

H -> H+ + e-

Stellar winds drag H+

ions away (if no protective

geomagnetic field) via ion

pick-up mechanisms.

If atmosphere is lost,

later outgassing can lead

to a CO2 rich atmosphere

High-energy spectral irradiance received by Prox b and the Earth. The integrated values are calculated per unit

wavelength. From Ribas et al. (2016)

X-ray EUV~250 x 50-30 X

FUV15-30 X

Proxima b

Earth

High-energy spectral irradiance received by Proxb and the Earth. The values are calculated per unit wavelength. From

Ribas et al. (2016)

From Griessmeier, Guinan et al. 2004, AA, 425, 753.

Effect of the intense solar wind of a young, active solar-type

star on the Magnetosphere of a nearby tidally locked planet

(X-UV/ Wind Flux data from Sun in Time program)

Strong Wind from young starWeaker Winds from an older Sun

To star->

Griessmeier et al. 2004

From Lammer et al. 2008 , Space Sci. Rev –Atmospheric

Escape and Evolution of Terrestrial Planets and Satellites

during

Proxima b: Climate for Synchronous Rotation

Possible Outcomes for Proxima bStar’s properties are well known but initial conditions of planet -such water inventories and geomagnetic fields are not constrained. As shown by Ribas et al. (2016), Prox b has endured very high radiation levels especially when the star was young. This makes outcomes uncertain.

Proxima Cen b: Possible Outcomes1. Low initial water inventories / weak geomagnetic fields: atmosphere /water

Outcome: like Mercury (dry barren planet) or Mars (cold, dry /ice planet) if Water not resupplied.

2. Weak geomagnetic fields; low – moderate initial water inventory. Young M5 V star’s strong X-UV radiation & wind – produce photolysis's H2O–> 2H + O. Two outcomes: a thick (>100 Bar) O2 rich atmosphere or if all H & O lost; later

outgassing of CO2 –> all (or most?) water lost -a Venus-like planet.

3. Abundant initial water (or water resupplied by comets) with a strong protective geomagnetic field: Water remains or is resupplied by comets – could result in a

Water World (like Earth) or Ice world (depending on outgassing).

4. Planet forms further from the host star and migrates inward. This could avoid / diminish the higher luminosity and strong X-UV effects of the young host star.

Water - Ice planet if it has sufficient water / strong geomagnetic fields

Possible Evolutionary Outcomes for Proxima b

Venus -Type Planet

Thick CO2 Atmosphere

Dense Iron Planet

Beyond Proxima Cen b:Investigating the next nearest PotentiallyHabitable Exoplanets: Kapteyn b (13 Ly) &Wolf 1061 c (14 Ly) – Assessing their Suitability for Life

Edward GuinanScott Engle Villanova University

Ignasi RibasI.C.E. Barcelona, Spain

Nearest Potentially Habitable Planets

Property Earth-Sun Proxima b Kapteyn b Wolf 1061 c [1.0 AU] [0.049 AU] [0.17 AU] [0.083 AU]

Mass (ME) 1.00 >1.27 >4.80 >4.25Radius (RE) 1.00 1.1 ~1.7 ~1.6

S/SE 1.00 0.65 0.40 0.60

Teq(K) 255 [288] 227 [277] 213 [263] 223 [273]

<fx> 0.67 c.g.s 163 5.4 ~30 [243 x Earth] [8.1 x Earth] [45 x Earth]

<f Ly-alph> 7.0 130 12 ~50 (FUV) [18.6 x Earth] [1.7 x Earth] [7.1 x Earth]

S/SE = instellation relative to Earth-Sun at 1.0 AU<f> mean irradiances [flux units: c.g.s = ergs/s/cm2]X-ray and Ly-alpha Irradiances on Earth: 0.67 and 7.1 ergs/s/cm2

TRAPPIST-1 Planetary System39 Light years away contains 2 Earth size planetsIn the liquid water habitable zone.

James Webb Space Telescope (JWST)

Expected Launch: Spring 2018

Searching for Evidence of

Atmospheres and Biosignatures

At orbital quadratures Prox b reaches

an angular separation of ~39 mas

from its host star.

Even though the Proxima b is small

and thus faint relative to Prox Cen, in

the near future (<10 yrs.), it may be

possible image the planet and / or

directly determine the chemical

composition of habitable planets.

Water, Oxygen, CH4 that could

indicate possible life.

Green dot Project – Search for

Exo-Aurorae Emission lines of OI 5577A

(See Luger et al. 2016) to study planet

E-ELT 39-m TelescopeWith AO has a chance to secure

spectra of Prox b free from the light

Of its host star

Under construction / first light 2025/26.

Giant Magellan

Telescope (GMT)(Under construction)

New Worlds Mission (NWM):

Hunting for alien lifeExobiology mission

https://exoplanets.nasa.gov/resources/1015

NWM can resolve Prox b from its host

star (~ 0.039” = 39 mas at quadratures)

permitting imaging and spectroscopy.

Star shade Concept: Occult Star: permit

hosted exoplanets to be imaged (being

considered by NASA with WFIRST Mission

~2025)

http://newworlds.colorado.edu/starshade/

China’s New 500-m FAST (Filled Aperture

Radio Telescope) will participate in searching

SETI radio signals (but Proxima is too far

South to observe)

Maybe in several years radio Signals will be detected with the SKA indicating IntelligentLife from a Nearby Exoplanet.

SETI Program (Allen Array)has been searching for over a decade. (no contact yet)

Going to Proxima b:

Interstellar Missions

and TravelMuch more difficult!(Nearest Star- the alpha Centauri

System is 4.3 LY (~40 trillion km away)

[1 LY = 5.85 x 1012 miles]

Starshot Mission to alpha Centauri

Nuclear Fusion Interstellar spaceshipFrom Icarus Interstellar

Fusion Enginesusing 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

Mae Jemison ,MD

http://100YSS.org

Captured Asteroid Concept

To boldly Go ?

(some fine day)

Welcome to Proxima b

Thank you!