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Worlds around
Distant Suns
Mini University
June 16, 2003
Among the most significant discoveries of the 20th Century
our own Solar System
Let’s beginwith…
How Big Are OUR Planets?
How Big Is OUR Solar System?
And Where Is Pluto?
What about the Nearest Stars?
try HAWAII!
Alpha, Beta, and ProximaCentauri
Rainbows from
Starlight
Finding Planets around Other Stars
Discovering Planets with SpectraDiscovering Planets with Spectra
o Absorption lines shift left or right if stars Absorption lines shift left or right if stars move toward or away from usmove toward or away from us
o Planetary orbits cause stars to move Planetary orbits cause stars to move
Doppler Shift IDoppler Shift II
Velocity of 51 Peg
-80
-60
-40
-20
0
20
40
60
80
0 10 20 30 40
Time (days)
Vel
oci
ty (
met
ers
per
sec
on
d)
About 7 orbits in 30 days…The planet’s year is only 4.2 days long
Physics co
mes
in handy!
The Mass of the Planet
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
0 10 20 30 40 50
Period (days)
Pla
net
ary
Mas
s (M
Jup
)
A period of 4.2 days means the planet’s mass is about half the mass of Jupiter
How Big is the Orbit?
ONLY 0.05 AU• The Earth is 1 AU from the Sun• Jupiter is 5 AU from the Sun• Mercury is about 0.4 AU from the Sun
51 Peg’s planet is HOT HOT HOT!
A Planet around Eridani
A planet orbits the star Eridani at a radius of 3.2 A.U.
Eridani is similar to our Sun Eridani is only 10.5 light years away The planet is similar to Jupiter The planet orbits Eridani in 7 years
Orion
And has at least 3 planets
terrestrialplanets
Properties of KNOWN Properties of KNOWN Extra-Solar PlanetsExtra-Solar Planets
• All are gas giants like Jupiter and Saturn• Most are larger than Jupiter• Many orbit close to their parent stars• Some are in systems with multiple planets
02468
101214161820
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14Minimum Mass (J upiters)
Num
ber
of P
lane
ts
So far, only large gas giants like Jupiter and Saturn have been found
Known Planets Are Close to Stars
Planets form as part of the process of star formation
Different Kinds of Planets
Gas Giants
Ice Giants
Terrestrial Planets
Hot Jupiters
These hot Jupiters form further out, and migrate inward as they eject smaller bodies from their planetary systems
• normal star like our Sun• 150 light-years from us • "year" of only 3.5 days• less than 7 million km from its own star • gas giant like Jupiter• hot, very extended hydrogen atmosphere• planet is evaporating – with a “comet” tail
Planets so close to their parent stars may not survive
An Evaporating
Planet
If the Earth lies in the same plane as the orbit of a planet we see a transit
•The planet passes across the face of the star
•Some of the starlight is blocked by planet and the star appears dimmer
Planetary Transits
Pictures of Planets?
Angular Resolution
Infrared sensitivity
Soon! We can now detect young planets the size of Jupiter as close as 6 A.U. from their parent stars!
Questions about Planets
What size planets usually form?
How far are planets from their parent stars?
How many planets do stars have?
What kinds of stars have planets?
What kinds of weather and clouds do planets have?
Finding Life on Distant Worlds
NASA is planning missions to find and study Earth-like planets around as many as 150 stars within 50 light-years.
•The Terrestrial Planet Finder will look for terrestrial-size planets in the "habitable zone“ •TPF will search for atmospheric signatures, habitability, or life itself
Can we travel to new worlds?
•Within the lifetime of today’s children we will be able to send robotic spacecraft to visit our nearest neighbors
•At 10% of the speed of light (30,000 km/sec) travel time will be about 100 years
•Then wait another 10-20 years for the data to return
What will we find?
The challenge of the next generation!
Kirkwood Observatory Open
• Every Wednesday evening• Weather permitting• When it’s dark…
Where to find Kirkwood
Websites of Interest Indiana Astronomical Society
www.iasindy.org National Optical Astronomy Observatory Image
Gallery www.noao.edu/image_gallery
Space Telescope Science Institute www.stsci.edu
Amazing Space amazing-space.stsci.edu
NASA’s Astronomy Picture of the Day antwrp.gsfc.nasa.gov/apod/astropix.html
Astronomical Society of the Pacific www.astrosociety.org
The Stonebelt Stargazers www.mainbyte.com/stargazers/