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

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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

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1

1.2

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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/