Agenda

Planet formation The search for life in the universe

What is this picture?

A. A distant star

B. Neptune

C. Earth

D. A galaxy

The “pale blue dot”:Earth viewed from the edge of our solar system (taken by Voyager 1).How hard would it be to learn about Earth from a long way away?

Aside:Disks in astronomy

Accretion disks around black holes

Planetary rings Spiral galaxies

astronomy.com

HST Cassini

When a star is born…

There is a disk of material left over. Rotates in the same direction as the

protostar.

Notice the scale!

Planet formation

Dust and gas is left over from star formation (1-100 AU in diameter)

Gravitational attraction brings particles together – creates a disk of material

Happens quickly - 3 to 30 million years

Similar to Shepherd moons

Disks around protostars

The hunt for new planets

Seeing them directly is nearly impossible.

Star wobbles because of the tug from its planet.

The wobble causes a Doppler shift that we can observe!

(motion of the star is greatly exaggerated!)

The most easily found exo-planets are ____.

A. Light and far from their star

B. Light and close to their star

C. Massive and far from their star

D. Massive and close to their star

2

star planetgravity

Gm mF

r=

To date…

Way over 200 extra-solar planets have been found 276 as of March, 2008

Most are: Massive Close to their star

Kepler mission

NASA's first mission capable of finding Earth-size and smaller planets around other stars.

Works by transit method. Launch scheduled for

February, 2009.

Can life exist anywhere?

What is required for life to exist?

What is required for life?

Water Oxygen? Energy input (usually sunlight) Carbon?

Location matters!

Sun from Mercury

Location matters!

Sun from Saturn

On the other hand…

Extremophiles live in very harsh conditions

Bacteria in Yellowstone Bacteria under ice in the Arctic

Star type matters

Remember OBAFGKM? Sun is G2. Is type B hotter or cooler than the

Sun?A. HotterB. CoolerC. Same temperatureD. Cannot tell

UV Radiation

Which has more UV in its spectrum: Sun or a B-type star?

A. Sun

B. B star

C. Same

D. Can’t tell B is hotter, so it has more UV.

UV breaks down organic chemicals Not conducive to life.

How should we go about looking for life elsewhere?

A. Go there!

B. Send out signals

C. Look for others sending signals

D. Look for chemical signatures of life

E. We should not look for life

Go there?

Example: NASA New Horizons mission Going to pluto and outer solar system Travels 47,000 mph

To get to the nearest star (4 ly away) 57,000 years OR, 2855 generations of people!

What would be required to make this work? (discuss)

Send out a signal?

Radio technology on Earth is about 100 years old.

Only stars within 50 ly could have gotten a signal and responded so far

(About 1400 stellar systems) No return signal yet!

Marconi company, England, 1906(wikipedia)

Listen? — SETI

Project Phoenix Observing since February, 1995 Looking at nearby, Sun-like stars only

Nothing yet!

SETI Institute

Would we know life if we saw it?

How do we know these are alive?

lichen

coral

Look for chemical signature

Water vapor CO2 (carbon dioxide) Methane Oxygen

Clicker registration!

If you don’t see your number, it means that your clicker is already registered.

Summary

Planets form quickly! Looking for life:

Location matters Look for byproducts of life

Exam 2 is Thursday at 6 pm!