Northeastern Illinois University

Other Solar Systems

Greg Anderson Department of Physics & Astronomy Northeastern Illinois University

Winter-Spring 2020

c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 1 / 53 Northeastern Illinois Outline University

Other Solar Systems Detection Exoplanets Earth Like Planets Nebular Theory Revisited Review

c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 2 / 53 Northeastern Illinois University

Outline Other Solar Systems Exoplanets are Common Exoplanets Discovery Zone

Detection

Exoplanets Earth Like Other Solar Systems Planets Nebular Theory Revisited

Review

c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 3 / 53 Northeastern Illinois Exoplanets are Common University

Exoplanet: a planet that orbits a star outside the solar system.

• Gravitational microlensing studies suggest Milky Way stars host, on average, one or more planets in a distance range of 0.5 – 10 AU. • One in five stars similiar to our Sun have an Earth sized planet in the habital zone.

c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 4 / 53 Northeastern Illinois Exoplanets University

NASA’s Exoplanet Archive, as of February 2019: • 4,770 candidates • 3,917 confirmed exoplanets • 657 multi-planet systems • 361 confirmed & in habitable zone

Exoplanet Graphics: For recent results see: • Mass vs. Distance • NASA’s Exoplanet Archive • Planetary Temperatures • Exoplanets.org • Number vs. Size • Exoplanet.eu

c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 5 / 53

Northeastern Illinois University

Outline Other Solar Systems

Detection Finding Exoplanets NASA Kepler Spacecraft TESS Five Discovery Methods Detection vs. t Detection Discovery Techniques Transit Photometry Transit Light Curves Doppler Shift Direct Imaging Disks Microlensing Exoplanet Microlensing Astrometry

Exoplanets Earth Like Planets Nebular Theory Revisited c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 7 / 53 Northeastern Illinois Finding Exoplanets University

“Looking for an Earth-like planet around a nearby star is like standing on the East Coast of the United States and looking for a pinhead on the West Coast - with a VERY bright grapefruit nearby.” • Kepler Space Telescope (2009-2013)

c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 8 / 53

Northeastern Illinois TESS University

Transiting Exoplanet Survey Satellite (TESS) • Launched April 18, 2018. • Two-year survey of over 200,000 stars. • Expected to to discover thousands of exoplanets.

c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 10 / 53 Northeastern Illinois Five Discovery Methods University

Transit: Searching for shadows – a star’s brightness drops when a planet crosses in front. Radial velocity: Watching for wobble – aka Doppler Spectroscopy. Detect Doppler shift in stars as in orbits center of mass. We can detect ∆v ∼> 1 m/s. Direct imaging: Taking pictures – Currently IR, large planets, far from star. Gravitational microlensing: The gravitational field of a star or planet acts as a lens to magnify the light of more distant objects. Astrometry: Precise measurements of the positions and movements of stars.

c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 11 / 53

Northeastern Illinois Discovery Techniques University

Method Number of Planets Transits 3144 Radial Velocity 793 Imaging 49 Microlensing 86 Astrometric 1 Total 4126

For updated counts please consult the NASA Exoplanet Archive.

c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 13 / 53 Northeastern Illinois Transit Photometry University

Transit: when one celestial body appears to move across the face of another.

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planet Brightness

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c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 14 / 53 llustration from Bill Borucki’s Jan 2010 AAS Presentation b

b b b b b b b b b b b b b b Doppler Shift due to Stellar Wobble b b b b b b b

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b b b Mt. Palomar’s Hale Telescope: Star HR8799, and three planets. 120 ly distant. Northeastern Illinois Disks Around β Pictoris University

c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 18 / 53

Northeastern Illinois University

Outline Other Solar Systems

Detection

Exoplanets XKCD Kepler Planet Candidates Eccentricity vs. Period Mass vs. Period Exoplanets Radius vs. Period Irradiation vs. Period Earth Like Planets Nebular Theory Revisited

Review

c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 22 / 53 http://xkcd.com/1071/

Northeastern Illinois University

Outline Other Solar Systems

Detection

Exoplanets Earth Like Planets Habitable Zone Kepler-186f ESI Earth Like Planets Habitable Zone Planets HEC Poster Nearest Confirmed Exoplanets Nebular Theory Revisited

Review

c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 29 / 53

Northeastern Illinois Kepler-186f University

The first known Earth-size exoplanet to lie within a habitable zone. Red dwarf star Kepler-186. d = 490 ly. c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 31 / 53 Northeastern Illinois Earth Similarity Index (0 ≤ ESI ≤ 1) University

Not Earth Like Venus Mars Earth Mercury Kepler-438b

0 0.2 0.4 0.6 0.8 1.0 KOI-433.02 m

n x − x wi/n ESI = 1 − i io =1  xi + xio  Yi

Property Referencevalue xio weight wi Radius r⊕ 0.57 Density ρ⊕ 1.07 Escape velocity v⊕ 0.70 Surface Temp 288 K 5.58

There is not a scientific concensus advocating use of the ESI.

c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 32 / 53

Northeastern Illinois Nearest Confirmed Exoplanets University

5 data source 4

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c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 35 / 53 Northeastern Illinois University

Outline Other Solar Systems

Detection

Exoplanets Earth Like Planets Nebular Theory Revisited Nebular Theory Nebular Theory Frost Line Hot Jupiter Revisited Hot Jupiter Hot Jupiters Challenges Planetary Migration Migrations Late Heavy Bombardment Further Study

Review

c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 36 / 53 Northeastern Illinois Nebular Theory University

Nebular Theory: Kant 1755, Laplace 1795 Our solar system formed from a giant cloud (nebula) of interstellar gas and dust. Denser regions of the solar nebula experienced stronger gravity and begin gravitational contraction. Heating, Spinning, Flattening • The Rotational speed of cloud increased as it contracted due to conservation of angular momentum: • Collisions between particles in the collapsing nebula flattened it into a flat disk with circular orbits. • The nebula temperature increased as it collapsed due to conservation of energy As the protoplanetary disk cooled, metal, rock and ice condense, coagulate and accrete into planetesimals and then planets.

c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 37 / 53 TFrost ≈ 150 K T >TF T = TF T

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b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b bb b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b bb b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b bb b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b bb b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b Rockyb Planetesimalsb b b b b b

Icy Planetesimals ⇒ Gas Giants

Image Credit: NASA/JPL

Northeastern Illinois Challenges for the Nebular Theory University

Surprises: • Some massive planets orbit very close to their stars: “hot Jupiters.” • Some extrasolar planets have highly elliptical orbits. Revisiting the Nebular Theory • Nebular theory: Jovian planets should not form inside the frost line (. 5 AU). • The discovery of “hot Jupiters” has forced a reexamination of nebular theory. Modification of the Nebular Theory Planetary migration or gravitational encounters may explain “hot Jupiters”.

c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 42 / 53 Northeastern Illinois Planetary Migration University

The Nice Model developed in Nice, France (2005): Jovian planets migrated to their present locations from an initial compact configuration (5.5-17 AU). The planetary migration may explain: • Late Heavy Bombardment • Formation of the Oort Coud • Neptune and Jupiter Trojans • Numerous resonant trans-Neptunian objects

c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 43 / 53

Northeastern Illinois Further Study University

For recent exoplanet results see: • NASA’s Exoplanet Archive • Exoplanets.org • Exoplanet.eu • TESS

• Exoplanets in Pictures (Phil Plait) • NASA Science Cast: Hot Jupiters

c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 46 / 53 Northeastern Illinois University

Outline Other Solar Systems

Detection

Exoplanets Earth Like Planets Nebular Theory Revisited Review Review Asteroid Facts asteroid orbits Meteors and Meteorites Meteoroid Summary Comet Summary Trans-Neptunian Objects (TNOs)

c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 47 / 53 Northeastern Illinois Asteroid Facts University

Relatively small, rocky objects orbit- ing the Sun. • Leftover rocky planetesimals • Majority between Mars and Jupiter

• Total mass ≪ MMoon • Largest Ceres, d ≈ 950 km • 1.1 − 1.9 million with d> 1 km. • > 400, 000 cataloged

Vesta

c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 48 / 53 Northeastern Illinois Asteroid Orbital Classification University

• Asteroid Belt, 75% (2.2 AU Asteroids (NEAs) > 8000 Amor a> 1 AU, 32% Apollo* a> 1AU, 62% Aten* a< 1 AU, 6%

c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 49 / 53 Northeastern Illinois Meteors and Meteorites University

Meteoroid: Small rocky debris from asteroid fragments or comet disintegration. Meteor: The flash of light produced when a meteoroid enters Earth’s atmosphere. Meteorites: Meteoroids that survive passage through the Earth’s atmosphere and impact on the ground. Most meteorites from the asteroid belt, some lunar and martian meteorites

c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 50 / 53 Northeastern Illinois Meteoroid Summary University

• Most meteorites are pieces of asteroids. • Most meteor showers have their origins with comets. • Primitive meteorites are remnants from solar nebula. • Processed meteorites are fragments of larger bodies that underwent differentiation. • 106–107 kg of meteorites fall on Earth each year.

c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 51 / 53 Northeastern Illinois Comet Summary University

• Icy left over planetesimals: Formed beyond the frost line, comets are icy counterparts to asteroids. • The nucleus of a comet is like a “dirty snowball.” • Most comets remain perpetually frozen in the outer solar system. • Most comets do not have tails, Only comets that enter the inner solar system grow tails. • Comets in plane of solar system come from the Kuiper Belt. • Comets on random orbits come from Oort Cloud.

c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 52 / 53 Northeastern Illinois Trans-Neptunian Objects (TNOs) University

Trans-Neptunian objects, any object with a>a[. Classes: • Kuiper Belt objects (KBOs) – Classical KBOs: Torus of objects with nearly circular orbits, small inclination, 30-50 AU. – Resonant KBOs: e.g. plutinos are in 3:2 resonance with Neptune. – Scattered KBOs: Source of short-period comets. Former KBOs scattering by gas giants to eccentric and inclined orbits, 30-100 AU.

• Oort Cloud Objects (OCOs) Spherical cloud of icy planitesials at 100,000 AU - 2 ly. Source of long-period comets. There are 1547 known TNO’s

c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 53 / 53