Download Two obvious differences between the exoplanets and the giant

PH709
Extrasolar Planets - 6
Professor Michael Smith
1
Two obvious differences between the exoplanets and the giant
planets in the Solar System:
A) Existence of planets at small orbital radii, where our
previous theory suggested formation was very difficult.
B) Substantial eccentricity of many of the orbits. No clear
answers to either of these surprises, but lots of ideas...
The Problem: It is very difficult to form planets close to the
stars in a standard theory of planet formation using minimum
mass solar nebula, because
•
•
it's too hot there for grain condensation and
there's too little solid material in the vicinity to build
protoplanet's core of 10 ME (applies to r~1 AU as well).
•
problematic to build it quickly enough (< 3 Myr)
•
there's too little gas to build a massive envelope
PH709
Extrasolar Planets - 6
Professor Michael Smith
12
PH709
Extrasolar Planets - 6
Professor Michael Smith
13
7 Summary of (Future) Missions
CoRoT is a space project:
Convection, Rotation and Transits
The COROT instrument makes it possible, with a method called
stellar seismology, to probe the inner structure of the stars, as well
as to detect many extrasolar planets, by observing the periodic
micro-eclipses occurring when these bodies transit in front of their
parent star.
Its objective is double:
- study stellar interiors
- detect planets analogous to the Earth orbiting around other stars
than the Sun.
A Russian Soyuz 2-1B rocket lifted the satellite into a circular polar orbit with an
altitude of 827 km on 27 December 2006. It will carry a telescope able to
observe continuously many stars during very long periods and to measure very
accurately the variations of their brightness.
http://corot.oamp.fr/
PH709
Extrasolar Planets - 6
Professor Michael Smith
14
….down to earth-like planets.
Kepler: 2009 - Transit method, occurrence of earth-sized planets.
http://www.kepler.arc.nasa.gov/
PH709
Extrasolar Planets - 6
Professor Michael Smith
15
Concept Study
Mar 2001 to July 2001
Discovery selection Dec. 21, 2001
Phase B
Feb 2002 to Oct 2004
Phase C/D
Nov 2004 to Oct 2008
Launch
February 2009
Commissioning Launch + 30 days
Phase E
Flight operations For 3.5 years from end of commissioning
Data analysis
For 5 years from end of commissioning
The Kepler instrument 0.95-meter diameter telescope.
It has a very large field of view for an astronomical telescope —105 square
degrees— or about the area of both your hands held at arm's length, in order to
observe the necessary large number of stars.
It stares at the same star field for the entire mission and continuously and
simultaneously monitors the brightnesses of more than 100,000 stars for the
life of the mission—3.5 years.
The diameter of the telescope needs to be large enough to reduce the noise from
photon counting statistics, so that it can measure the small change in brightness
of an Earth-like transit. The design of the entire system is such that the combine
differential photometric precision over a 6.5 hour integration is less than 20
ppm (one-sigma) for a 12th magnitude solar-like star including an assumed
stellar variability of 10 ppm. (This is a conservative, worse-case assumption of a
grazing transit.
A central transit of the Earth crossing the Sun lasts 13 hours. And about
75% of the stars older than 1 Gyr are less variable than the Sun on the time scale
of a transit. )
The photometer must be space-based to obtain the photometric precision
needed to reliably see an Earth-like transit and to avoid interruptions caused by
day-night cycles, seasonal cycles and atmospheric perturbations, such as,
extinction associated with ground-based observing.
Space Interferometry Mission SIM and Gaia: astrometry
The Space Interferometry Mission (SIM) will detect planets with masses as
low as 3 M Earth orbiting within 2 AU of stars within 10 pc, and it will
measure masses, orbits, and multiplicity. The candidate rocky planets will
be amenable to follow-up spectroscopy by the “Terrestrial Planet Finder”
and Darwin.
PH709
Extrasolar Planets - 6
Professor Michael Smith
16
TPF: Direct imaging detection and spectroscopic characterization of
nearby Earthlike planets will be undertaken by the Terrestrial
Planet Finder missions.
The TPF Coronagraph (TPF-C), planned for launch in 2014, will
operate at visible wavelengths. It will suppress the light of the central
star to unprecedented levels, allowing it to search for terrestrial
planets in ~150 nearby planetary systems. TPF-C will be followed
about five years later by the TPF Interferometer (TPF-I). TPF-I will
operate in the mid-IR and will survey a larger volume of our solar
neighborhood, searching for terrestrial planets around as many as
500 nearby stars.