Transcript Planetary Science. - Nmsu - New Mexico State University

Some
PLANETARY SCIENCE
Topics
Jim Murphy
Department of Astronomy
New Mexico State University
Las Cruces, NM
July 17, 2007
NMSU Campus
A ‘soon to launch’
Mars Spacecraft Mission
The Mars Phoenix Lander
(1st launch opportunity: Aug 3rd)
(Mars arrival & landing: May 25th, 2008)
July 17, 2007
NMSU Campus
The scientific motivation for the
Phoenix Lander
is
to investigate the probable presence
of near-surface water ice at high
northen martian latitudes
July 17, 2007
North Pole
South Pole
(to 60 degrees N)
(to 60 degrees S)
NMSU Campus
The Mars Phoenix Lander
is a STATIC lander (not a rover)
July 17, 2007
NMSU Campus
The Mars Phoenix Lander will ‘excavate’ the
near-surface ‘soil’ and analyze its contents for
ice and other materials….
July 17, 2007
NMSU Campus
Let’s Make a Planet…
The Fun New Game Show
Sweeping the Solar System
July 17, 2007
NMSU Campus
WHAT IS OUR SOLAR SYSTEM?
The collection of:
- our star (the Sun)
- the nine 8 planets that orbit this star (some big, some small)
- asteroids and comets (that also orbit around the star)
- moons that themselves orbit around the planets (and
asteroids!)
- ring particles (orbiting the planets)
- dust (which can become meteors)
- 'Kuiper Belt' objects (Pluto ??? … and beyond)
HOW DID ALL OF THESE OBJECTS COME
TO BE ASSOCIATED AS THEY ARE?
July 17, 2007
NMSU Campus
Our Solar System as we know it
The Sun
Rocky, metal planets
and moons
Asteroids
Comets
(in the Asteroid Belt)
Gas Giant Planets
Almost all of these objects orbit the Sun in the same direction
within the same flat plane (like a spinning DVD)
July 17, 2007
NMSU Campus
Let’s try to determine how planets were formed….
Let’s Make a Planet
You, the contestant, can choose from amongst…
Door #1
‘Capture by the Sun’
Door #2
‘The Spitting Sun’
July 17, 2007
NMSU Campus
Door #3
‘Dust Clumping’
DOOR #1: ‘Capture’
Let’s imagine that some magical process is responsible
for forming stars and planets, and asteroids and comets,
each independently (each forms on its own very far apart
from one another) throughout the Galaxy
Door #1
‘Capture by the Sun’
WHAT WOULD BE THE RESULTANT
STRUCTURE OF THE SOLAR SYSTEM?
Solar System CAPTURE THEORY of formation
IDEA: The Sun has “captured” (via gravity) all of
the objects now orbiting around it
What is wrong with this idea?
July 17, 2007
NMSU Campus
A ‘CAPTURED’ Solar System
The Sun
Rocky, metal planets
and moons
Asteroids
Comets
(in the Asteroid Belt)
Gas Giant Planets
If the objects in the Solar System were “CAPTURED” by the
Sun, they would be moving in random directions around the Sun
July 17, 2007
NMSU Campus
So,
A CAPTURE scenario
would produce a Solar System
that
DOES NOT look
like our Solar System
..and we still would not have any idea how planets actually form..
and why some are GAS GIANT and some are TERRESTRIAL
July 17, 2007
NMSU Campus
DOOR #2: ‘The Spitting Sun’
Let’s imagine that the Sun ‘spits out’ some of its own
material, and that this ‘spat out’ material collects together
to form a planet orbiting the Sun
WHAT WOULD BE THE RESULTANT
STRUCTURE OF THE SOLAR SYSTEM ?
Door #2
‘The Spitting Sun’
Solar System FISSION THEORY of formation
IDEA: The Sun ‘burps’ out material to form planets
What is wrong with this idea?
July 17, 2007
NMSU Campus
The “Burping” Sun
These ‘spat out’ planets would have compositions
identical to the Sun’s composition, which is dominated
by the gases hydrogen and helium…..Earth is composed
of rock and metal,..the gas Giants do have hydrogen and
helium, but not as much (relatively) as the Sun
July 17, 2007
NMSU Campus
So,
A SPITTING SUN scenario
would produce a Solar System
that
DOES NOT look
like our Solar System
..and we do not know of a physical mechanism by which the
Sun can ‘burp out’ so much mass at one time……
July 17, 2007
NMSU Campus
DOOR #3: ‘Dust Clumping’
Let’s imagine that a really, really big (and massive)
cloud of gas (and some dust) within the Galaxy
collapses under its own gravitational pull upon itself
Door #3
‘Dust Clumping
WHAT WOULD BE THE RESULTANT
STRUCTURE OF THE SOLAR SYSTEM ?
Solar System CLOUD COLLAPSE of formation
IDEA: A cloud of gas (and some dust) collapses,
forms a rotating disk of gas and dust, has a star
“turn on” at its center, and dust within the disk
material clumps and gravitationally sticks together
to form objects which might grow to be planets
July 17, 2007
NMSU Campus
Collapsing Gas Cloud
..as seen from the side
At the center of the cloud, the collection of gas becomes very
dense, and nuclear fusion sets in…A STAR IS BORN !
Dust within the disk, which is rotating around the new star, begins
to lump together forming large objects (some destined to become
Planets)… far from the Sun, these ‘clumps’ can also grab cold gas
July 17, 2007
NMSU Campus
Collapsing Rotating Gas Cloud
..as seen from above
Gas Giant Planets
Rock-metal Planets
At the center of the cloud, the collection of gas becomes very
dense, and nuclear fusion sets in…A STAR IS BORN !
Dust within the disk, which is rotating around the new star, begins
to lump together forming large objects (some destined to become
Planets)… far from the Sun, these ‘clumps’ can also grab cold gas
July 17, 2007
NMSU Campus
So,
A CLUMPING scenario
can produce a Solar System
that
DOES look
like our Solar System
..and accounts for rock-metal planets near to the Sun and
Gas Giants far from the Sun based upon temperature……
July 17, 2007
NMSU Campus
Near to the young Sun, within the disk, gas molecules were
fast because the gas there was HOT….. The gravitational
pull of these growing planets was not strong enough to grab
and hold these fast-moving gas (hydrogen and helium)
molecules and atoms
significant gas DOES NOT accumulate around the planet……
July 17, 2007
NMSU Campus
Far from the young Sun, within the disk, gas molecules were
slow because the gas there was COLD….. The gravitational
pull of these growing planets WAS strong enough to grab
and hold these slow-moving gas (hydrogen and helium)
molecules and atoms
so significant gas DOES accumulate around the planet……
July 17, 2007
NMSU Campus
So,
A CLUMPING scenario
can produce a Solar System
that
DOES look
like our Solar System
..and accounts for rock-metal planets near to the Sun and
Gas Giants far from the Sun based upon temperature……
July 17, 2007
NMSU Campus
Are there any observations
which support this idea of
CLUMPING……?
the so-called
SOLAR NEBULA
Hypothesis
..why yes, indeed, such observations do exist !!
July 17, 2007
NMSU Campus
HUBBLE SPACE
Telescope
images do show the presence
of gas and dust clouds
surrounding young stars
July 17, 2007
NMSU Campus
STAR (at the center)
DISK (seen edge-on)
July 17, 2007
NMSU Campus
Star’s light is ‘blocked out’
STAR (at the center)
DISK (seen edge-on)
July 17, 2007
Planet forming within the dust disk?
NMSU Campus
A Hubble Space Telescope image of the
Orion Nebula, a region in our Galaxy in
which many stars are being ‘born’
July 17, 2007
NMSU Campus
A ‘protoplanetary’ disk seen ‘flat on’; this
star and its associated disk are located
within the Orion Nebula
July 17, 2007
NMSU Campus
So, current thought is:
Planets form from material
within a collapsing gas cloud.
The rotating disk results in all
of the planets orbiting within
the same direction
and in same plane.
Observations support this idea.
July 17, 2007
NMSU Campus
DOOR #3
#3
DOOR
“CLUMPING”
“CLUMPING”
is the winner !!!
Thanks for playing..
Let’s Make a Planet…
..one final item
July 17, 2007
NMSU Campus
..one final item
Just as New Mexico experiences
dust devils…….
So too does Mars !
A dust devil
July 17, 2007
NMSU Campus
Dust devils ‘dancing’ across Mars’ surface
as observed by the Mars SPIRIT Rover
Gusev Crater, Mars
July 17, 2007
NMSU Campus
Let’s build some planets !!
Jim Murphy
Department of Astronomy
New Mexico State University
Las Cruces, NM
July 17, 2007
NMSU Campus
ASTR 508
Astronomy for Educators
Fall 2007: online offering
Dr. Bernie McNamara
NMSU’s masters of Art
in Teaching Degree Program
July 17, 2007
NMSU Campus