Transcript brightness

The Search for Exoplanets
An exoplanet is a planet orbiting a star outside
of our solar system
The first proven exoplanet was 51 Pegasi,
announced in 1995. To date, 2011 planets
have been identified.
Ways of Discovering Exoplanets
Stars are so much bigger and brighter (+1,000,000x)
than planets, it is nearly impossible to just point a
telescope at a star and see its planets
Radial Velocity
As a planet goes around its star, they both orbit
the same center of gravity. The gravity of the
planet cause the star to wobble.
This back forth wobble is detectable as a back
and forth redshift and blueshift of the star
Radial Velocity only works on very large
planets, bigger than Jupiter. It also appears to
be most effective if the planet is very close to
the star.
51 Pegasi, the first exoplanet, is 3 times closer
to its star than Mercury.
As of December 2015, 622 exoplanets have
been discovered using Radial Velocity
Imaging
Recently, telescopes have made huge technological
advances. Telescopes and interferometers (a bunch
of small telescopes mimicking a giant one) have
become advanced enough to take actual pictures of
exoplanets. 63 planets have been discovered by imaging.
Gravitational Microlensing
Gravity from a star or planet causes light to bend.
If a star has a planet going around it, this “lensing”
will cause it to periodically become brighter and
dimmer.
This technique is only being done by the University
of Warsaw in Poland. They have discovered 42
exoplanets
Pulsar Timing
When very massive stars run out of nuclear fuel,
they explode, leaving a small dense core, called a
neutron star.
These remnants usually spin, sending out “blips”
of radiation, this is called a “pulsar”.
A planet can form out of the debris of the dead star,
which can gravitationally alter the spin of the pulsar,
which can be measured.
23 exoplanets, with a pulsar as the central star, have
been discovered.
Transit Photometry
The total light from a star can be measured. If you
continuously watch a star, and note that it gets
dimmer periodically, that is caused by a planet
blocking the light. 1255 planets have been discovered.
The Kepler space telescope (launched 2009), is
looking at a tiny patch of sky with powerful enough
optics to detect these miniscule differences in light
1020 planets have been confirmed.
Kepler is looking at 150,000 medium to small
stars for changes in the light curve of the star.
BRIGHTNESS
If you were watching a star, and a planet passed
in front….what would happen to the light curve?
0
0
TIME