Transcript Alien Earths Floorplan (3,000 sq. ft) Major Exhibit Areas

The
Traveling Exhibit
Science Background
Part B: Star & Planet Formation
prepared by Dr. Cherilynn Morrow for the Space Science Institute
Boulder, CO
B. Star and Planet Formation
KEY QUESTIONS:
Where do stars & planets we observe in the galaxy come from?
Around which kinds of stars should we look for signs of life?
We are “Star Stuff”
The Astronomical Spectroscopy of Sir William Huggins
Huggins’ private observatory
Tulse Hill, London
“One important object of this original
spectroscopic investigation* of the light
of the stars and other celestial bodies,
namely to discover whether the same
chemical elements as those of our earth
are present throughout the universe, was
most satisfactorily settled in the
affirmative; a common chemistry, it was
shown, exists throughout the universe.”
- Sir William Huggins
*In 1859, Huggins began observing the stars
using Bunsen's and Kirchhoff's discoveries
that spectral emission and absorption lines
could reveal the composition of the source.
Star and Planet Formation
Where do stars and planets come from?
 Planets sometimes form
along with a central star out
of the same swirling disk of
gas and dust.
 Our search for life beyond
our solar system requires
knowing where and how this
process occurs.
 The best chance to find an
“Alien Earth” might be to look
around stars like our Sun.
 The “birth” of star systems
Artist Concept:
Early star-planet system in formation
“proto-planetary disk”
where life evolves depends on
the “death” of massive stars
that spew out elements like
carbon & oxygen.
Searching Around Sun-Like Stars
Why search for planets and life around Sun-like stars ?
 We know that in our case, a planet
(Earth) with life has evolved around
such a star.
 High-mass stars (> 10 times the
mass of the Sun) burn brightly with
ultraviolet radiation that tends to
destroy proto-planetary disks. Massive
stars also have relatively short
“lifetimes” (1 to 10 million years as
compared to 10 billion years for the
Sun). This is not time enough for
planets with life to evolve.
 Low-mass stars (< 0.6 times the
mass of the Sun) are relatively dim
and have very long lifetimes: there is
time enough for life to evolve around
them. Their dimmer light sometimes
makes observations more challenging.
When Sun-Like Stars “Die”
Butterfly Nebula
Eskimo Nebula
Cat Eye Nebula
Stars have “life cycles”. They are “born”
and they “die” but are not alive like us.
Stars like the Sun “die” by “puffing” off
their outer layers of gas and dust. This
process creates a beautiful variety of
NEBULAE in the Milky Way GALAXY.
When Massive Stars “Die”
• Blue giant stars that are
much more massive than the
Sun form elements heavier
than hydrogen & helium (e.g.
carbon, nitrogen, oxygen) via
nuclear fusion in their cores.
• Such massive stars “die” in
incredibly powerful explosions
called supernovas.
• Supernovas spew heavier
elements needed for life out
into the galaxy.
Stars Have “Life” Cycles
Crab Nebula:
Supernova Remnant
• The explosions themselves
can stimulate new star birth by
sending shock waves into
nearby clouds of gas & dust.
Another beautiful supernova remnant, just for fun!
Supernova Remnant
The Right Stuff
Supernovas help ensure that heavier elements and complex
molecules are found throughout interstellar space.
• Since the “building
blocks” of life are so
utterly common,
perhaps it might not
be so strange to find
life everywhere!
• And yet, the living
cell is so amazingly
complex that we
must wonder if it
commonly emerges
and survives, even
on other Earth-like
worlds.
Forming Worlds Where Life Can Exist
Artist’s concept of the formation of OUR SOLAR SYSTEM
1. Something (perhaps a supernova) triggers the gravitational collapse of a nearby
interstellar cloud. The cloud naturally heats up and spins faster as it
collapses. Collisions between particles flatten the cloud into a disk.
2. The Sun and planets start to form in this spinning, flattened disk (protoplanetary disk), with the Sun at the hottest central part.
3. In our Solar System, Earth formed in the inner region of the disk where rocky &
metallic material could condense in the greater heat. Ices & hydrocarbons
settled in the outer regions where gas giants like Jupiter form.
4. Computer models tell us that Jupiter’s gravity played a strong role in causing
comet & asteroid impacts to supply water & organic materials to Earth from
the outer solar system, thus contributing to its habitability.
Star Forming Regions
These large clouds of gas and dust in our Milky Way galaxy are the types
of regions where many stars are forming: Orion and Eagle NEBULAS.
Orion
Eagle
Our entire solar system would fit in this small nub
HST Images of Proto-planetary Disks
Proto-planetary disks around young stars in the Orion Nebula.
The disks range in size from 2 to 8 times the diameter of our Solar System.
Spitzer “Sees” through the Dust
Where do stars and planets come from?
 Spitzer is the largest
infrared telescope ever
launched into space.
 Many areas of space
are filled with vast, dense
clouds of gas and dust
which block our view.
 Infrared (IR) light, can
Artist Concept:
NASA’s Spitzer Spacecraft
penetrate these clouds,
allowing us to peer into
regions of star formation
and into newly forming
planetary systems.
Now You See Stars, Now You Don't
• The image composite
compares an infrared
image taken by NASA's
Spitzer Space
Telescope to a visiblelight picture of the
same region (inset).
• The added detail in
the Spitzer image
reveals a dynamic
region in the process
of evolving and
creating new stellar
“life”.
• Spitzer is both
seeing, and seeing
through, the dust.
A striking comparison, just for fun!
Overhead Infrared Camera
looking down at nebula
Our hands look red on the
screen. We emit IR light!
Yes! I wonder what’ll happen
if we put our eyeglasses
under the IR camera?
Alien Earths:
Infrared (IR) Camera
Interactive
The monitor displays what
the IR camera is “seeing”
Heat source
beneath the
nebula on the
round table
Cone Nebula
star forming region
There are round heat sources beneath the nebula on the table which cannot
be seen with the human eye, but which are being “seen” by the infrared
camera and recorded on the monitor. The IR light “shines” right through the
table! In a similar way, the Spitzer Telescope can detect infrared radiation
shining through dusty interstellar clouds revealing young stars in formation.
Design a Solar System
Alien Earths:
Design a Solar System
Touch Screen
Interactive
“Hey, I can drag a bunch of planets in
orbit around a star and then let them
zoom around to see if they will fly out
of the system, or crash into each
other, or be gobbled up by the star!”
• Computer models show that not every
configuration of planets is a stable one.
• The gravitational effect of a Jupitersized planet in a close elliptical orbit
can be to kick terrestrial planets out of
the system.
Based on real, multi-body model simulations
of the stability of planetary orbits.
• Jupiter-sized worlds in more distant
circular orbits are much more helpful to
the formation and evolution of Earthlike planets in a habitable zone.
B. Star and Planet Formation
SUMMARY
Elements heavier than Hydrogen & Helium form inside stars
and then are released back into the galaxy when stars “die”.
Thus materials that are the “building blocks” for life &
Earth-like planets are found throughout interstellar space.
Planets sometimes form along with a central star out of a
common swirling disk of gas and dust.
Our search for life beyond our Solar System requires
knowing where and how this process occurs.
Perhaps the best chance to find an “Alien Earth” is to look
around stars that are most like our Sun.