Extrasolar planets

Emre Işık (MPS, Lindau)

S3 lecture

Origin of solar systems

14 February 2006

Outline

• Planet detection methods– Methodology– Some recent results

• Statistical properties of exoplanets• Future prospects

Struve, O. 1952 Obs., 870, 199

Detection techniques IPrecise stellar radial velocities to observer

N. S

trob

el

N. S

trob

el

to observer

N. S

trob

el

Detection techniques IITransit photometry

a = (PorbR) / t

f / f = (Rp / R)2

Detection techniques IITransit photometry

Advantages

• Easy (if automated!), small telescopes with good sites/detectors

• Possibility to detect low-mass planets, especially from space (Kepler mission, 2008)

Disadvantages

• Transit probability low; simultaneous observations of many stars

• Confusion with starspots, multiple stars

Planets around binary stars

Deeg (1998)

Reflection effect

HST light curve of HD 209458 b

Brown et al. (2001) • Stellar radius and limb-darkening profile • Planet's mass and radius • No rings around the planet • No moons with M > 3 ME (repeated obs.)

Detection techniques IIIMicrolensing

Detection techniques IIIMicrolensing eventsOGLE 2003-BLG-235/MOA 2003-BLG-53

Discovered planet: 1.5 MJ @ 3 AU

Bond et al. 2004, Astroph. J. Letters , 606 , L155

Detection techniques IIIMicrolensing events

Discovery of a Cool Planet of 5.5 Earth Masses. OGLE-2005-BLG-390

Beaulieu et al., 2006, Nature, 439, 437

Discovered planet: 5.5 ME @ 2.6 AU

Detection techniques IVAstrometry

“Celestial” motion of the Sun due mainly to Jupiter & Saturn, as seen from 33 light years

away…

Astrometry

A Jupiter analog orbiting 5 AU from a solar-type star produces an astrometric amplitude of 0.5 milliarcsec (mas).

A star with planet close to (about 1 arcmin) to a star without planet is needed.

Direct, short CCD exposure at Palomar 5m and Keck telescopes may yield 0.1 mas.

Palomar test-bed interferometer yields 60-70 μas, VLTI should allow 20 μas.

Space missions may do better as interference from terrestrial atmosphere is eliminated.

As of 1998, no object has been found.

Technique is in its infancy. Big telescope resources are needed.

Detection techniques VDirect imaging !

Detection techniques VDirect imaging !

Visible light

Infrared light

• Name: 2M1207 b

• Msini: 5 ± 1 MJ

• Radius:1.5 RJ

• Temperature1240 ± 60 K

• Semi-major axis: (projected dist.) ~ 55 AU

• Orbital period: > 2450 yr

• Mass (star/M_sun): 0.025 NACO/VLT image, Chauvin et al. 2005

Detection techniques VDirect imaging !

Substellar companion to GQ Lupi

• IR image (NACO/VLT) GQ Lupi (A) orbited by a planet (b) at a distance of ~20xJupiter-Sun.

• GQ Lupi: 400 ly, 0.7 M

• Mass: 1-42 MJ

Detection techniques VI [reflection/absorption]

spectroscopy

Detection techniques VI [reflection/absorption]

spectroscopy

Detection techniques VI [reflection/absorption]

spectroscopy

Caution: “planet occurrence” is biased by RV sensitivity!

Properties of the detected planets

Lineweaver & Grether 2003

Properties of the detected planets

Lineweaver & Grether 2003

Extrapolations

Lineweaver & Grether 2003

Lineweaver & Grether 2003

Evolutionary models

• Different assumptions on the inhibition of cooling by irradiation from the parent star, and the planet's internal structure (Burrows et al. [2000], Bodenheimer et al. [2001] and Guillot and Showman [2002])

Fig.: Collier Cameron (2002)

The future:Future of future:

2015 - 2025

CO2

O3