ExoplanetsTHE SEARCH FOR NEW WORLDS

What are Exoplanets?

Sometimes called extrasolar planets

Planets that orbit stars other than our Sun

Four main classes:

Jupiters: > 0.1 MJupiter; presumably all gas giants

Neptunes: 10 MEarth to 0.1MJupiter; presumable gas giants with rocky

Earth-sized cores

Super Earths: 2-10 MEarth; presumably rocky

Earth: < 2MEarth, presumably rocky

Majority of planets found are near-orbit Jupiters

Probably due to our detection method limitations

How do we find them?

1969 confirmed exoplanets (as of Oct. 5)

Many more awaiting confirmation

Various missions to discover exoplanets

CoRaT

Kepler

Two main methods of planet hunting:

Radial Velocity

Transit Light Curve

Radial Velocity

Gravitational effect of a planet on the star it orbits

causes the star to wobble

If the system is along our LOS, we can measure this wobble using the star’s spectrum

Slight blue- and red-shifting of the absorption lines

indicates the star’s wobble

Analyzed to determine planet’s mass and orbital period

Works best for stars with few and large planets

Courtesy NASA/JPL-Caltech

Transit Light Curve

Star’s light is blocked when planets passes between star

and us

Produces a noticeable decrease in the brightness of a star

We use light curves to measure this

Light curves are star’s brightness mapped as a function of

time

Regular dips in light curve indicate a planet in orbit

Gives information about planet radius and orbital period

Used by Kepler to discover thousands of potential

exoplanets

Courtesy NASA/JPL-Caltech

Why look for exoplanets

Help discover our own planet’s origins (Comparative Planetology)

Many planetary systems we find are young

Gives insight to solar system formation

‘The Hunt for Vulcan’

We assume extra-terrestrial life requires a planet

Many planets have been identifies to have orbits within the ‘Goldilocks

Zone’

Plan B

Earth’s not lookin’ too good

We may need an escape hatch in the future

Interesting Revelations

Solar Systems like ours are rare

Hot Jupiters

Not many systems found with rocky inner

planets and large gaseous outer planets

Some planets can actually be directly

viewed

2M1207 is one of first directly viewed

exoplanets

Planet 2M1207 (bottom right) and its

brown dwarf host

Credit: ESO

Pushing Limits of Exoplanet

Discovery

NASA and Poland jointly made this discovery

Used both the Spitzer Space Telescope and the Optical Gravitational Lensing Experiment from Poland

Used the gravitational microlensing of a transiting star to magnify the image of a distant sun and analyze the light curve

The discovered planet is one of the most distant exoplanets discovered to date JPL-CalTech/NASA

Astronomy: A New Spin on

Exoplanets

Article from the journal Nature

Written by Travis Barman of the Lunar and Planetary Laboratory

Focused on new methods of discerning the spin of an exoplanet

Uses radial velocity and Doppler shift to measure the orbit

Spectroscopy of planet’s atmosphere so we know absorption lines

Spectrum blue shifted on one side bur redshifted on other

Extrasolar Planets: Window on a

Watery World

Another article from Nature

By Elizabeth M. R. Kempton of Grinnel College

Talks about a sample of planets in which no spectral data could be

acquired

Most likely culprit is clouds in atmosphere blocking light from passing

through

Only one planet our of four sampled did not have cloud

interference

Why?