Extrasolar Planets = 403

Transcription

1 Extrasolar Planets = 403 Planets orbiting stars other than the Sun Smaller than 13 Jupiter masses First planet around ordinary star is 51 Peg 1995 Most found using Iodine cell technique pioneered at DAO, UBC, UVic

2 Zeroth Method: Pulsar Timing First planets discovered By Wolszczan in 1989 Would have been inside supernova explosion 2 systems/ 4&1 planets

3 First Method: Direct Imaging of Extrasolar Planets (11) Planets are billions times fainter than sun/star Planets usually not resolved from star Use adaptive optics or HST HR8799 & Fomalhaut announced Oct08

4 Second: Astrometric Detection of Extrasolar Planets Stellar motions not resolved =too small to be measured First & only detection announced 2002 Gl 876 had previously been known to have a planet from radial velocity studies

5 Third: Gravitational Lensing Method (9) Foreground star lenses background star and planet(?) One 5.5 Earth masses At distance of Asteroid belt from M dwarf Frequency of planets larger than 13% - likely 90% for M dwarfs

6 Fourth: Radial Velocity (376) Star pulled back and forth by gravity of planet Doppler shift measures velocity of star Bigger, closer planet: larger velocity Lots of Hot Jupiters discovered The first planet discovered in the solar neighborhood in 1995

7 Fifth: Transiting Planets 62 transiting planets Smaller star - deeper eclipse Bigger planet - deeper eclipse Observations by Deeg and Garrido at the 0.9m Sierra Nevada Telescope of IAA Granada).

8 Characterization of Planets Planets only a million times fainter in Infrared Using the Spitzer IR telescope the planet s eclipse can be seen Gives planet temp=770k Drawn in Visible and IR

9 Upper Atmosphere of HD209458B Can see the planet s atmosphere in absorption during transit Hydrogen, Na, H 2 O gas in atmosphere blown away by stellar wind

10 Atmosphere of HD209458b A dozen eclipsing extrasolar planets If you subtract an eclipse spectrum from an out of eclipse spectrum you get the planet s spectrum No bio-markers (CH 4 +O 2 ) and surprisingly no water

11 Map of Extrasolar Planet 3 Planet orbits HD showing phases, assuming locked in rotation Winds transport heat to night side? Map has temperatures of C

12 Extrasolar Planets 403 Planets Orbiting stars Binaries,Triples Giants White Dwarfs 45 multiple planet systems Most are Jupiter mass planets & close to star = short period Observed orbits more eccentric than Jupiter & Saturn Most stars with planets have extra iron, silicon, carbon etc.

13 COROT Hunting Planets Blasted off 27Dec08 Observes 12,000 stars at a time Convection, rotation and planetary eclipses/transits Planetary eclipses are short lines and spots go in/out of phase

14 Discovered by CoRoT 2009 Transit is deep so diameter ~2Earths Radial Velocity => ~8Earth Masses Orbital Period ~20hours Smallest Exoplanet

15 Kepler Satellite Launched 06Mar09 Into Earth trailing orbit Will survey 100,000 stars Looking for transits by: 1,000 hot Jupiters? 100 hot Earths? 10 Earths in Habitable zone?? Marcy will use Keck for Radial Velocity follow-up

16 HAT-P-7 b First Kepler data Shows Eclipse, Occultation, Phases No Earth type planets; yet

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18 Passing Star Hypothesis Buffon in 1745 Catastrophic process Low probability of encounter Hot gasses would dissipate before they could condense Predicts few stars with planets

19 Nebular Hypothesis Descartes 1644 envisioned vortices Laplace 1796 added Newton s gravity Evolutionary process Angular momentum problem: Sun has 99.9% of mass and 0.3% of angular momentum Jupiter has 60% of angular momentum and 0.1% of mass

20 All the stars form from dust clouds Because cloud is spinning dust falls in faster along poles forms disk Lumps in disk become planets Sun and planets clean out inner disk ending planet building Predicts many stars with planets Solar Nebula Theory

21 Stars Form Within Disks 2 Million year old star in GMC 2MASS shows 2 stars; Adaptive Optics Gemini; Long exposure with AO and Gemini and close up of thin disk 5 Disks in Orion Nebula

22 Solar System Looks Like a Disk As the planet s distance from the sun increases; its period of revolution about the sun increases & velocity decreases The planets revolve in orbits that are tilted less than 7 Planets orbit in same direction

23 Obliquity of Rotation Axes Most planets rotate counter-clockwise Most planets rotation axis is perpendicular to ecliptic plane Sun s rotation axis tilted by 7 But why are Uranus and Pluto tilted ~90 Why does Venus rotate retrograde=clockwise

24 Sun and Jovian Planets Located in the outer solar system, less dense, more massive, many satellites, ring systems, thick atmosphere composed with same chemical composition as sun

25 Terrestrial Planets and Large Moons Earth, Venus, Mars, Ganymede, Titan, Mercury, Callisto, Io, Moon, Europa, Triton, Pluto Located close to sun, more dense, smaller mass, less volatiles, rocky cratered surface, little or no atmosphere, few moons, no rings

26 Rocky Surfaces Saturated with Craters Planets formed from many meteorite impacts Heavy Bombardment Late Heavy Bombardment second surge in impacts

27 Asteroid Characteristics Vesta, Ceres and Earth s Moon Movie of Eros small rocky bodies Ceres > 1000km diameter; 2>500km; 15>250km Probably a million > 1km Named by discoverer Not enough gravity to pull them into spherical shape

28 Asteroid = Minor Planet Orbits Some planetesimals left over after planets formed Asteroids, Near Earth Objects, Comets Generally orbit between Mars and Jupiter with gaps Over 444,080 with good orbits 1 named after UVic and 14 others named after UVic people

29 Kuiper Belt Objects Small icy worlds beyond Pluto = Dwarf Planets Tenth planet?, Eris=UB313

30 Comet Lulin Dirty Snowball or Icy Mudball Nucleus ~10km Tail ~1 million km Very eccentric orbit 3572 comets 2000 short period

31 Comet Tails: Hale-Bopp 1997 Radiation pressure and the solar wind blow the comet s tail So that it always points away from the sun Blue ion/gas tail points away from sun; yellow dust in orbit

32 Meteorites Peekskill meteorite or fireball 1992 New York Bright as full moon Lasted for 40 seconds Meteorite on ground, meteor in air and meteoroid in space Pinhead sized rocks burn up ~80km high in atmosphere Earth receives 40,000 tons of meteorites per year Some leftover from formation of Solar System

33 Characteristics of Two Kinds of Planets Jovian planets are larger, lower density, farther from sun, thick atmosphere, more satellites, rings Terrestrial planets are smaller, denser, closer to sun, rocky cratered surface, few satellites, no rings

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35 Characteristic Properties- Solar System Disk shape of solar system- orbit inclination; prograde motion; nearly same tilt of rotation axes Jovian and terrestrial planet types- low/high density Planetary ring & satellite systems for gas giants Space Debris icy comets, rocky asteroids, meteors Common ages of Earth, moon, Mars, meteorites, sun

36 Density of Planets Terrestrial Planets more dense than Jovian gas giants Uncompressed densities show Mercury is most dense and Mars is least dense Problem is moon is not dense enough (3.36)???

37 Hot Disk and Frost Line (Ice Line) Gas from solar nebula falls on to disk and heats it Beyond the frost line in middle of asteroid belt (~3.5AU) planetesimals form from water ice

38 Condensation Sequence Generally the closer a planet is to the sun the more metals The farther from the sun the more volatile compounds

39 Condensation Shuttle experiment done in no gravity found dust formed grains very quickly If moon formed at same distance: should have the same density but it does not

40 Accretion Snowballs form aided by static electricity Dust falls to form very thin disk and gas forms thick disk Solar wind blows dust around but not pebbles so dust sticks to pebbles Up to kilometer sized

41 Planetesimals Eventually some massive enough to grow by gravitygreater than ~a km Pandora and Hyperion; Low density moons of Saturn

42 Protoplanets The more massive - the faster they grow At more than 15 earth masses gravitational collapse starts Capturing Hydrogen and Helium directly from nebula

43 Comet Impacts on Jupiter Painting shows Jul94 impacts of Comet Shoemaker-Levy 9 HST photo from 20Jul09 Comets deposit ice Heating planet

44 Differentiation of Planets Young planet is very hot due to radioactive decay and Impact heating (=heat of formation) Iron, Nickel, Iridium settle to the core Silicates rise above iron Ices/water next

45 Outgassing Water, carbon dioxide, sulfur dioxide, nitrogen released by volcanoes Forms atmosphere

46 Overview of Planet Formation Common orbital and rotation direction & plane => nebular disk Jovian / Terrestrial => range of temperatures in disk Common ages => simultaneous formation in disk Problems: Speed of Jupiter s formation, angular momentum, clearing disk, discrepancies, moon!

47 Jovian Problem / Disk Instability Disk blown away by sun and other stars in a few million years Jupiter needs to form in millions of years So Jupiter needs to migrate to sweep up more gas & dust Movie by Phil Armitage 2005 shows density waves excited by planet

48 Planet Migration Planetesimals could gain or loose energy in encounters with planets but Detailed calculations show Jupiter would move in and Neptune would move out Debris would be ejected: to Oort cloud?

49 Angular Momentum Problem The protosun rotates rapidly and has huge convection cells so it generates a strong magnetic field The magnetic field tries to accelerate the disk and solar wind, slowing rotation by magnetic braking Observations of stars with known ages in Hyades etc. show that the older stars rotate more slowly

50 4 Processes that Cleared the Inner Solar System Radiation pressure sun&stars Solar Wind blows away rings Planetesimals incorporated into planets Planetesimals ejected

51 Debris Disk After the dense disks that form planets Cold disks of dust are left Made from asteroid collisions & comet s tails

52 Heavy Bombardment Phase Heavy bombardment phase at 4 billion years clears nebula Craters formed on top of craters Still have problem of tilted rotation axes: Pluto & Uranus Retrograde rotation of Venus Eccentric and retrograde satellite orbits Moon

53 Large Impacts In final stages of formation solar system would have had many collisions of bodies the size of planets Such impacts could tilt the rotation axis of Uranus, Pluto + rotation of Venus All planets would have been hit by something one tenth its size

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55 Out Beyond the Kuiper Belt at 2000AU to 1 light year Lies the hypothetical Oort cloud of a trillion Comets

56 MOST: Jaymie Matthews UBC Observed HD for months and Saw no eclipses from Earth sized planets Timed transits showing no Earth sized planets-so far No opposition effect so low 50% albedo

57 Coronographic Image of Debris Disk Star is masked by black spot in original and untilted image Notice cleared inner disk(30au) and spiral wave features ~320 light years distance, 300AU diameter, 5 Million years old

58 Comet NEAT 29Jan & 2Feb03 Dirty snowball or maybe icy mud ball is better Nucleus ~ 10km Tail ~1,000,000km to 1 astronomical unit Very eccentric elliptical orbit

59 Fifth: Transit Method (62) Planets of 12 Jupiter masses, Jupiter, Neptune, M dwarf are all about same size/transit depth Works best for big planet close to star

60 NGC 3603 Carina Nebula Bright young blue stars Red HII region Black Dust Two proplyds dissolving in UV from hot stars in about 100,000 years