Lecture 34:
Exoplanet Characterization
●
Homework 7 Due Now!
●
Next Week: Chpt 12&13
News….
●
●
●
The fireball seen/heard in California was likely
close to the size of a large car upon entry
Explosion ~5 Megaton (1/3 of Hiroshima
bomb)
They have found some pieces on the ground
–
●
Looks like CM Chondrite (very primitive and
volatile-rich – same as Murchison)
They are seeking footage of the fireball in the
sky to try to reconstruct its orbit
http://cosmicdiary.org/fmarchis/2012/04/25/daylight_meteor_incalifornia/
Orgueil
Meteorite
●
●
●
Fell in 1864
One of only 5 CI
chondrites – the
most primitive
known
Orbit of entry
reconstructed in
2006 – looks to
come from a
cometary orbit
Daily show on space miners (Weds)
Exoplanets...
we can find them, but can they
support life?
What do we know about the exoplanets from the
different detection techniques?
●
Pulsar Timing Variations
●
Radial Velocity
●
Transit
●
Microlensing
●
Direct Imaging
Characterizing Exoplanets
●
(0) Detect the planet
–
●
(1) Determine Radius and Mass = Density
–
●
●
Most methods: Distance from star
Guess at Bulk Composition
(2) Basic Atmosphere Characteristics
–
Temperature
–
Composition
(3) ???
Searching for Life on Exoplanets
What we can actually see now:
Directly Detected Cold Jupiters
●
●
Approximate
temperature
Not enough light for
a real spectrum...
but photometry ok!
Gemini Planet Imager
The state of the art
–
–
–
Uses a corograph to
block the light from the
star
Cover a wide wavelength
to get some spectral
information of an imaged
planet
Can image a planet 10
million times fainter at
0.2-1 arcsec away
●
5-40 AU from a star.
What we can actually see now:
Transiting Hot Juputers
Secondary Transits
Temperature!
HD 189733 b
Sub-solar point
●
●
Temperatur
e as a
function sun
angle
We can see
there must
be high
winds!
What we can actually see now
If the planet absorbs more light at a
certain wavelength → composition!
Very uncertain detection of water
(remember this is a Hot Jupiter!)
We found Venus’ atmosphere via transit
Super Earths!
What are they made of?
“Super Earth” Compositions
Are Super Earth's a Good Place
for Life?
●
Could they have a liquid solvent (water)?
●
Could they have a source of Energy?
●
Could they have the building blocks (CHON)?
Probably a large range of planets would have these things...
but if life on an exoplanet is like potential life on
Mars/Europa/Titan/Enceledus etc, we won't be able to detect it
until we go there... in the VERY distant future
Are super-Earth's
a good place for complex life?
●
Ability to hold on to atmospheres?
●
Ability to have a magnetosphere?
●
Ability to regulate climate over long periods?
(Carbon cycle)
State of the Art Today
●
●
●
●
We can find gas giants on very long orbits if they are young
and nearby (direct detection)
We can find planets down towards super-earth/earth
sizes/masses on short period orbits (R-V and transit)
We can get statistics about planets in an intermediate range
(microlensing) but not much follow up
We can characterize the atmosphere of some nearby
transiting Hot Jupiters and some direct detected planets
What would we need to determine
the atmospheric composition of an
exo-Earth
●
●
Collect enough light from the
planet to be able to spread it
out (photometry or spectra) =
big telescope
Separate the light of the
planet from the light of the star
(high angular resolution)
= interferometry / coronograph
Thirty Meter Telescopes
Terrestrial Planet Finder:
To Directly Detect and Earth
Either many telescopes flying in formation
or
A big mirror with a large corograph
Coronograph
●
Coronograph (blocks
starlight)
50 m across
●
●
Designed by Web
Cash (here at CU)
Flown 1000s km away
from telescope
Next Week
●
●
Is there intelligent life out there and, if so,
where is it?
Read Chpt 12 & 13