What's an exo-planet?

• Planets must orbit the Sun
• Planets must be large enough that their gravity forces their shape to be spherical
• Planets must clear their orbits of other material, so they are the largest body near their orbit

What's a planet?

• Planets must orbit the Sun
• Planets must be large enough that their gravity forces their shape to be spherical
• Planets must clear their orbits of other material, so they are the largest body near their orbit

Finding exoplanets

All we have to measure is light from a distant star.....so how can we find a planet that we can't see?

flux

spectra

position

wavefront

What can we measure from light?

Characteristics

• Intensity ("flux")
  • photometry
    • magnitudes
    • transits
• Wavelength ("color")
  • spectrum
    • radial velocity
    • composition
  • incandescence
  • emission
  • absorption
• Interference
• Polarization
• Timing

Transits

Transits rely on chance alignments

https://exoplanets.nasa.gov/alien-worlds/ways-to-find-a-planet/

Radial Velocity

Radial velocity favors cooler stars.

Current visible-light RV instrument operate at the ≈ 10cm/s precision thanks to extreme wavelength stability and calibration.

Astrometry

Astrometry favors hotter stars and nearby stars.

Astrometric detection of exoplanets requires sub-μarcsecond position measurement. Equivalent to seeing 1mm on the moon.

Gravitational microlensing

Microlensing relies on chance alignments

Direct Imaging

The star to planet contrast varies from 1e7 (10 μm thermal IR) to 1e10 (visible light),

https://www.osapublishing.org/oe/fulltext.cfm?uri=oe-25-23-28825&id=376674

    "The multiple observation techniques are scientifically complementary, and several approaches are required for characterization of exoplanets.

For example, direct imaging is key to measure the exoplanet’s atmospheric composition (spectroscopy), but does not measure exoplanet radius (measured by transit) or mass (measured by radial velocity or astrometry)."

https://exoplanets.nasa.gov/

TESS camera apertures

Kepler primary mirror

~ 100,000 stars over several years

https://archive.nytimes.com/www.nytimes.com/interactive/science/space/keplers-tally-of-planets.html

TESS

Most stars aren' t single

~50% of the stars you see are binaries

~25% are triples

-on avg there's an exoplanet per star

~10% of Sun-like stars likely host rocky exoplanets, more for lower-mass stars

but atmospheric turbulence limit resolution to 

The problem of the atmosphere

details = color ÷ telescope size

details = color ÷ atmosphere turbulence (~10cm)

Classifying

exoplanets

https://exoplanets.nasa.gov/alien-worlds/exoplanet-travel-bureau/

https://exoplanets.nasa.gov/alien-worlds/galaxy-of-horrors/

https://exoplanetarchive.ipac.caltech.edu/

• Hot Jupiters
• lava planets
• rogue planets

https://www.nasa.gov/feature/jpl/20-intriguing-exoplanets

• lethal rain
• devoured planets
• evaporating planets
• eccentric orbits
• ocean planets
• zombie planets

Tidally locked planets

Eyeball planets

Multiple-habitable worlds in a single system?

Circumbinary planets

Kepler-16

Super-Earth or mini-Neptune?

Garnet planets

Plate tectonics & magnetic fields - these are important for life

We know the compositions of the stars.....the same elements likely go into the planets that form

https://www.nasa.gov/feature/jpl/20-intriguing-exoplanets

Atmospheres

&

Biosignatures? 

Oxygen

• get transmission spectrum of the atmosphere
• measure different radii at different wavelegnths to give clues to composition

Light

Solar system

http://joshworth.com/dev/pixelspace/pixelspace_solarsystem.html

http://www.omgspace.net/

• Why does Saturn have rings? What are the rings?

Moons that are other worlds:

Stars

Stellar Evolution

<0.08

0.08-0.4

0.4-8

>8

>20

>3

1.4-3

>1.4

Solar Masses

Scales and galaxies

Oumuamua

Random

• How does climate change affect NASA? (if the world is going to end, if climate change is such a big problem, wont that affect our study of other planets)

  • https://www.bloomberg.com/graphics/2015-whats-warming-the-world/

Why is the government underfunding NASA? Are there other ways for NASA to get money?

https://www.thebalance.com/nasa-budget-current-funding-and-history-3306321

https://www.nasa.gov/topics/benefits/index.html

https://www.youtube.com/watch?time_continue=19&v=84wJYwsEx0s&feature=emb_logo 

Was the moon landing fake?

https://www.youtube.com/watch?v=_loUDS4c3Cs&t=3s

https://www.forbes.com/sites/startswithabang/2018/12/12/heres-your-proof-that-we-landed-on-the-moon-steph-curry/#1229c00249d9

• photos from LRO
• photos from the missions:
  • https://www.flickr.com/photos/projectapolloarchive/albums
• equipment on the moon
  • seismometers
  • laser retroreflectors
• lunar samples
• broadcast tracking -inc Soviets

https://apolloinrealtime.org/11/