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Solar Systems
How To Make a Solar System
Maybe..
How Many Planets (This Week?)
OK. So, what is a planet, anyway?
1) A "planet" is a celestial body that:
(a) is in orbit around the Sun,
(b) has sufficient mass for its self-gravity to overcome rigid body forces
so that it assumes a hydrostatic equilibrium (nearly round) shape, and
(c) has cleared the neighborhood around its orbit.
2) A "dwarf planet" is a celestial body that:
(a) is in orbit around the Sun,
(b) has sufficient mass for its self-gravity to overcome rigid body
forces so that it assumes a hydrostatic equilibrium (nearly round) shape,
(c) has not cleared the neighborhood around its orbit, and
(d) is not a satellite.
(3) All other objects except satellites orbiting the Sun shall be referred to
collectively as "Small Solar System Bodies".
My Very Excellent Magic Carpet Just Sailed Under Nine Palace Elephants, Man. HA!
The Rocky Planets
Russian Venera 13 image
2
Olympus Mons – largest volcano in our solar system
A
River Beds
Mars
The “Gas Giants”
Io
Europa
Ganymede
+58 others
Callisto
+42 others
And so did medieval
scholars.
The year 1584
"There are countless suns
and countless earths all
rotating around their suns in
exactly the same way as the
seven planets of our system
. . . The countless worlds in
the universe are no worse
and no less inhabited than
our Earth”
Giordano Bruno
in De L'infinito
Universo E Mondi
4
Just how far are these new planets?
IF YOU WANTED TO RADIO HOME
from the Moon…
from Mars…
from the nearest
extrasolar planet…
it would take
one second
it would take
ten minutes
it would take
over ten years!
FOR YOUR WORDS TO REACH EARTH
But not far on a cosmic scale.
Imagine, if you shrunk our solar system
to a little larger than a quarter:
Our whole Solar
System
Our Milky Way Galaxy
would be this big
would be the size of
the United States.
And the neighborhood
where we’ve found
new planets would
only be the size of
Manhattan.
The Milky Way
250 Light Years From Home
Scientists use the Doppler shift to measure the tug
of planets on stars. Here is how it works:
If an unseen
planet tugs the
star back and
forth…
…the light from
the star shifts
slightly to the
red as the star
moves away
from you.
…and slightly to
the blue as it
moves toward
you.
Astronomers can
detect these shifts
by very carefully
observing the
spectra (or colors)
of the stars.
Star
51 Peg
Jup. Mass
0.6
Semi-Major
Axis (Au)
0.05
(4.6 mm)
Period
4.2293
Ecc.
0.0
Most of new discoveries are gas giants like
Jupiter or Saturn and in the wrong location.
The right location in our solar system.
17
Many of the new planets get too
hot or too cold to support life.
Too hot!
Just right!
Too cold!
Most of them have highly elliptical orbits,
or are too close to their parent stars.
The planets discovered so far are closer
in mass to Jupiter.
This is what
we’ve found
This is what we
are looking for
Jupiter’s diameter is eleven times greater than the Earth’s, and it
has over 300 times the mass.
Stars are a billion
times brighter…
…than the planet
…hidden
in the glare.
Like this firefly.
And how will we know a planet supports life?
Look for evidence
of oxygen
Analyze the
reflected light from
the planet to see if
the planet has an
atmosphere
Look for liquid
water
Look for signs of
biological activity
(methane)
and rule out other explanations.
17
This is from the ground
This is from space
Extrasolar Planet Hunters…
Keck Interferometer
Large Binocular Telescope Interferometer
Kepler
Spitzer Space Telescop
…on the
ground
and in
space.
SIM PlanetQuest
Terrestrial Planet Finders
19
For example, we will look for the star’s light to
dim slightly when a planet passes in front.
This is called the transit method
NASA’s Kepler Mission will hunt for planets
using a specialized one-meter diameter
telescope called a photometer to measure
the small changes in brightness caused by
these passing planets (or transits).
We will measure the tiny wobble of stars
against other stars in the background.
This is called astrometry
SIM PlanetQuest will determine the
positions of stars several hundred times
more accurately than anything previously
possible, helping to pin-point Earth-sized
planets.
We will block out the bright light from the star.
Telescopes that block the
light from the central star
can take images of planets
that might be in orbit around
them.
Keck Interferometer
The Keck Interferometer
The two Terrestrial Planet
combines the light of two 10Finder observatories will
meter telescopes to take
search from space for planets
images of hot Jupiter-size
as small as Earth and for
planets that shine bright in
signs about whether they can
infrared light.
support life.
The Terrestrial Planet Finder
Coronagraph (left) and Interferometer
And we will explore regions where planets
formed to get clues about the universe
In an early stage, before planets
are formed, some stars are
shrouded in dense disks of gas
and dust.
Launched in 2003, the Spitzer Space
Telescope is using its infrared camera to
study the beginnings of planetary systems.
Spitzer Space Telescope
Final Talk in Series
February 10
Earth as a Habitable Planet