Transcript Extrasolar planets

First direct image of extrasolar planets
10.7 billion miles
Fomalhaut A is 16 times brighter
than the Sun and is 200 million
years old.
The planet has a mass of 3
Jupiter’s masses and orbital
period 872 years.
It is too bright for its size and is
probably still contracting, or has
a ring.
We know there should be planets around other stars.
How to find them???
Star-Birth Clouds in M16 (Eagle Nebula). J. Hester and P.
Scowon (Arizona St. Univ.), November 2, 1995. Taken with
NASA Hubble Space Telescope, WFPC2
M > 2000 M
JUPITER
SHINES WEAKER THAN THE SUN:
1 000 000 000 TIMES
50 000 TIMES
5 000 TIMES
(visible light)
(infrared)
(mm and sub-mm)
JUPITER
OBSERVED FROM THE NEAREST STAR
0.1” DISTANT FROM THE SUN
„DROWNED” IN SUNSHINE !!
POPULAR
VIEW
REALITY
X = CENTER
OF MASS
SYSTEM VIEWED
POLE-ON (RARE)
Center of Mass
(SLIDESHOW MODE ONLY)
THE PLANET CANNOT BE SEEN
...BUT
MOTIONS
OF THE STAR
BETRAY
ITS PRESENCE !
450 km
9 cm/s
150 000 000 km
30 km/s
X
EARTH
750 000 km
13 m/s
JUPITER
X
780 000 000 km
13 km/s
MOTIONS
OF THE SUN
VIEWED FROM
A STAR 30
LIGHT YEARS
AWAY
2020
1995
2010
1990
0.002’’ IS THE
ANGULAR
SIZE OF A
MAN ON THE
MOON OR A
STANDARD
NEWSPAPER
FONT 300 KM
AWAY
2015
2000
0.002”
Unobservable!
2005
STELLAR
WOBBLE
RECEDING:
REDDER
APPROACHING:
BLUER
The Doppler Effect
The light of a
moving source is
blue/red shifted by
Dl/l0 = vr/c
l0 = actual
wavelength
emitted by the
source
Blue Shift (to higher
frequencies)
vr
Red Shift (to lower
frequencies)
Dl = Wavelength
change due to
Doppler effect
vr = radial
velocity
1 Angstrom = 10-8 cm
PLANET DETECTION DUE TO STELLAR WOBBLE
100
m/s
P
normal to
the orbit
i
to the observer
50
K
0
V
-50
-100
0
1
2 days 3
K = Vsin i
Only the function of masses and inclination angle
can be measured
ANOTHER
EFFECT:
TRANSIT
PLANET
IN FRONT
OF THE STAR
TRANSIT
BRIGHTNESS
LIGHT
CURVE
1%
TIME
Measure the radius of the planet, know the mass -> find the mean density!!
First direct detection of radiation from
extrasolar planet!
Spitzer Infrared Telescope
First detection of any carbon-bearing molecule on a planet outside
the Solar System! Swain et al., Nature, March 2008
Also confirmed previous discovery of water on this planet
326 extrasolar planets are found so far
http://planetquest.jpl.nasa.gov/
Planetary system of u And
0.85 AU
242 days
2 MJ
0.06 AU
4.5 days
0.75 MJ
0.39 AU
89 days
0.73 AU
228 days
1 AU
1 year
2.5 AU
3.5 years
4 MJ
1.54 AU
1.9 years
Solar system
Source: Harvard-Smithsonian CfA
Are we alone in the Universe??
Are there any Earth-like planets in habitable zones around stars?
Habitable zones
April 25, 2007: Discovery of the first Earth-like
planet in the habitable zone!!
Red dwarf
What would be the signs of life on other planets??
Signs of life in the spectrum: