Download Linking Asteroids and Meteorites through Reflectance Spectroscopy

Astronomy 101
The Solar System
Tuesday, Thursday
2:30-3:45 pm
Hasbrouck 20
Tom Burbine
[email protected]
Course
• Course Website:
– http://blogs.umass.edu/astron101-tburbine/
• Textbook:
– Pathways to Astronomy (2nd Edition) by Stephen Schneider
and Thomas Arny.
• You also will need a calculator.
Office Hours
• Mine
• Tuesday, Thursday - 1:15-2:15pm
• Lederle Graduate Research Tower C 632
• Neil
• Tuesday, Thursday - 11 am-noon
• Lederle Graduate Research Tower B 619-O
Homework
• We will use Spark
• https://spark.oit.umass.edu/webct/logonDisplay.d
owebct
• Homework will be due approximately twice a
week
Astronomy Information
• Astronomy Help Desk
• Mon-Thurs 7-9pm
• Hasbrouck 205
•
The Observatory should be open on clear Thursdays
• Students should check the observatory website at:
http://www.astro.umass.edu/~orchardhill for updated
information
• There's a map to the observatory on the website.
Final
• Monday - 12/14
• 4:00 pm
• Hasbrouck 20
HW #10
• Due today
HW #11
• Next Tuesday
If you want to find life
outside our solar system
• You need to find planets
• http://exoplanet.eu
Extrasolar Planets
• Today, there are over 400 known extrasolar
planets
Star Names
• A few hundred have names from ancient times
• Betelgeuse, Algol, etc.
• Another system:
• A star gets name depending on what constellation
it is in
• With a Greek letter at the beginning
– Alpha Andromeda, Beta Andromeda, etc.
• Only works for 24 brightest star
Star Names now
• Stars are usually named after the catalog they were
first listed in
• HD209458 is listed in the Henry Draper (HD) Catalog
and is number 209458
• HD209458a is the star
• HD209458b is the first objects discovered orbiting the
star
Our Solar System has basically two types
of planets
• Small terrestrial planets – Made of Oxygen, Silicon, etc.
• Large gaseous giants – Made primarily of hydrogen and a
little helium
–
–
–
–
Jupiter - 90% Hydrogen, 10% Helium
Saturn – 96% Hydrogen, 3% Helium
Uranus – 83% Hydrogen, 15% Helium
Neptune – 80% Hydrogen, 20% Helium
Things to Remember
• The Milky Way has at least 200 billion other
stars and maybe as many as 400 billion stars
• Jupiter’s mass is 318 times than the mass of the
Earth
Question:
• How many of these stars have planets?
What is the problem when
looking for planets?
What is the problem when
looking for planets?
• The stars they orbit are much, much brighter than
the planets
• Infrared image of the star GQ Lupi (A) orbited by a
planet (b) at a distance of approximately 20 times the
distance between Jupiter and our Sun.
• GQ Lupi is 400 light years from our Solar System and
the star itself has approximately 70% of our Sun's mass.
• Planet is estimated to be between 1 and 42 times the mass
of Jupiter.
•
http://en.wikipedia.org/wiki/Image:GQ_Lupi.jpg
So what characteristics of the planets may
allow you to “see” the planet
So what characteristics of the planets may
allow you to “see” the planet
• Planets have mass
• Planets have a diameter
• Planets orbit the star
http://upload.wikimedia.org/wikipedia/commons/d/de/Extrasolar_Planets_2004-08-31.png
• Jupiter
–
–
–
–
H, He
5.2 AU from Sun
Cloud top temperatures of ~130 K
Density of 1.33 g/cm3
• Hot Jupiters
–
–
–
–
–
–
H, He
As close as 0.03 AU to a star
Cloud top temperatures of ~1,300 K
Radius up to 1.3 Jupiter radii
Mass from 0.2 to 2 Jupiter masses
Average density as low as 0.3 g/cm3
10
100
1,000
(lightyears)
Some Possible Ways to detect Planets
•
•
•
•
Pulsar Timing
Radial Velocity (Doppler Method)
Transit Method
Direct Observation
Pulsars
• Rotating Neutron Stars
• Have densities of
8×1013 to 2×1015 g/cm³
•
http://www-learning.berkeley.edu/astrobiology/powerpointhtml/sld035.htm
• http://en.wikipedia.org/wiki/Image:Ssc2006-10c.jpg
Would you want to live on a
pulsar planet?
Center of Mass
• Distance from center of first body = distance between the bodies*[m2/(m1+m2)]
• http://en.wikipedia.org/wiki/Doppler_spectroscopy
Radial Velocity (Doppler Method)
http://www.psi.edu/~esquerdo/asp/shifts.jpg
• http://astronautica.com/detect.htm
Wavelength
http://www.psi.edu/~esquerdo/asp/method.html
www.physics.brandeis.edu/powerpoint/Charbonneau.ppt
Bias
• Why will the Doppler method will preferentially
discover large planets close to the Star?
Bias
• Why will the Doppler method will preferentially
discover large planets close to the Star?
• The gravitational force will be higher
• Larger Doppler Shift
Transit Method
• When one celestial body appears to move across
the face of another celestial body
• When the planet crosses the star's disk, the visual
brightness of the star drops a small amount
• The amount the star dims depends on its size and
the size of the planet.
• For example, in the case of HD 209458, the star
dims 1.7%.
•
http://en.wikipedia.org/wiki/Extrasolar_planets#Transit_method
One major problem
• Orbit has to be edge on
Eclipse
• Planet passes in back of a star
• http://www.news.cornell.edu/stories/March05/Planet-eclipse-Plot.mov
• Because the star is so much brighter than a
planet, the dip in brightness is smaller during an
eclipse than a transit
• Usually to maximize the effects of an eclipse,
astronomers observe these eclipses at infrared
wavelengths
Direct Observation
• Infrared Image
Visible
•
•
Infrared
http://www.news.cornell.edu/stories/March05/extrasolar.ws.html
http://nai.nasa.gov/library/images/news_articles/319_1.jpg
http://en.wikipedia.org/wiki/Image:Extrasolar_planet_NASA2.jpg
How did these Hot Jupiters get orbits so
close to their stars?
How did these Hot Jupiters get orbits so
close to their stars?
• Formed there – but most scientists feel that Jovian
planets formed far from farther out
• Migrated there - planet interacts with a disk of
gas or planetesimals, gravitational forces cause
the planet to spiral inward
• Flung there – gravitational interactions between
large planets
Kepler Mission
• Kepler Mission is a NASA space telescope
designed to discover Earth-like planets orbiting
other stars.
• Using a space photometer, it will observe the
brightness of over 100,000 stars over 3.5 years to
detect periodic transits of a star by its planets (the
transit method of detecting planets) as it orbits our
Sun.
• Launched March 6, 2009
Kepler Mission
http://en.wikipedia.org/wiki/File:Keplerpacecraft.019e.jpg
Kepler Mission
• The Kepler Mission has a much higher probability
of detecting Earth-like planets than the Hubble
Space Telescope, since it has a much larger field
of view (approximately 10 degrees square), and
will be dedicated for detecting planetary transits.
• There will a slight reduction in the star's apparent
magnitude, on the order of 0.01% for an Earthsized planet.
www.physics.brandeis.edu/powerpoint/Charbonneau.ppt
KEY D
22255311322343524233524343125151
35254313
What Planet do we know the most
about?
• Earth
http://college.cengage.com/geology/resources/protected/physicallab/thelab/interior/index.htm
Earth’s Interior
Earth’s crust
•
•
•
•
•
•
•
•
46.6% O
27.7% Si
8.1% Al
5.0% Fe
3.6% Ca
2.8% Na
2.6% K
2.1% Mg
Earth is made of minerals
Mineral
• A naturally occurring, homogeneous inorganic
solid substance having a definite chemical
composition and characteristic crystal structure
Olivine
• (Mg, Fe)2SiO4
• Fayalite (Fa) - Fe2SiO4
• Forsterite (Fo) - Mg2SiO4
Pyroxenes
• XY(Si, Al)2O6
• X can be Ca, Na, Fe+2, Mg, Zn, Mn, and Li
• Y can be Cr, Al, Fe+3, Mg, Mn, Sc, Ti, V, and Fe+2
Augite
Ferrosilite
How do we know what’s
in the interior of the Earth?
How do we know what’s
in the interior of the Earth?
• Seismic Waves – vibrations created by
earthquakes
Seismic Waves
• P waves – primary waves
– (pushing) – travel faster
– can travel through
anything
• S waves – secondary –
(side to side) – travel
slower – only through
solids
• http://alomax.free.fr/alss/examples/hodo/hodo_ex
ample.html
Surface Waves
• Travel on the surface of the Earth
• Love Wave – side by side
• http://www.geo.mtu.edu/UPSeis/images/Love_ani
mation.gif
• Rayleigh Wave – rolling movement
• http://www.geo.mtu.edu/UPSeis/images/Rayleigh
_animation.gif
• Most of the shaking felt from an earthquake is due
to the Rayleigh waves
P (primary) waves
S (secondary) waves
Surface waves: Rayleigh and Love waves
Richter Scale
• Measures the magnitude of an earthquake
• Single number to quantify the amount of seismic energy released
by an earthquake. Amplitude of largest displacement
• Under 6.0 - At most slight damage to well-designed buildings.
Can cause major damage to poorly constructed buildings.
• 6.1-6.9 - Can be destructive in areas up to about 100 kilometers
across where people live.
• 7.0-7.9 - Major earthquake. Can cause serious damage over
larger areas.
• 8 or greater - Great earthquake. Can cause serious damage in
areas several hundred kilometers across.
How do we get information?
• The precise speed and direction of the waves
depends on the composition, density, pressure,
temperature, and phase (solid or liquid)
Which of these bodies have they used
seismic waves to study?
• Earth
• Moon – Apollo missions brought seismometers to
Moon to study moonquakes
How can you study
the interior of a planet
from space?
Density
• Density = mass/volume
• If the density is higher than the surface rock, there
must be denser material in the interior
Gravity
• If you can measure gravity (force) with a
spacecraft as it rotates around a body, you can
determine how mass is distributed on the body
Magnetic Field
• Tells if a planet has a molten metal interior
http://www.gcsescience.com/pme1.htm
Earth’s magnetic field is believed to be
caused by the convection of molten iron,
within the outer liquid core along with the
rotation of the planet
Electrons flow
http://geomag.usgs.gov/images/faq/Q6.jpg
http://www.scifun.ed.ac.uk/card/images/left/earth-magfield.jpg
• Magnetic pole moves
http://science.nasa.gov/headlines/y2003/29dec_magneticfield.htm
http://science.nasa.gov/headlines/y2003/29dec_magneticfield.htm
North Magnetic Pole
• However, the "north pole" of a magnet is defined
as the one attracted to the Earth's North Magnetic
Pole
• By this definition, the Earth's North Magnetic
Pole is physically a magnetic south pole
Glatzmeier and Roberts simulations:
Geomagnetic Reversals
• Based upon the study of lava flows of basalt
throughout the world, it has been proposed that
the Earth's magnetic field reverses at intervals,
ranging from tens of thousands to many millions
of years
• The average interval is ~250,000 years.
• The last such event, called the BrunhesMatuyama reversal is theorized to have occurred
some 780,000 years ago.
• The present strong deterioration corresponds to a 10–
15% decline over the last 150 years and has accelerated
in the past several years
• Geomagnetic intensity has declined almost continuously
from a maximum 35% above the modern value, which
was achieved approximately 2000 years ago.
• At this rate, the dipole field will temporarily collapse by
3000–4000 AD
What may happen during the reversal?
• There may be a slight rise in the per capita cancer
rate due to a weaker magnetic field.
• We may also be able to see the northern lights at
lower latitudes
• If you own a compass, it will have difficulty
finding north until the magnetosphere settles.
Van Allen Belts
• The Van Allen radiation belts are rings of
energetic charged particles around Earth, held in
place by Earth's magnetic field
• Outer belt – primarily electrons
• Inner belt – primarily protons
http://www.nytimes.com/2006/08/10/science/space/10vanallen.html
Van Allen Belts
http://en.wikipedia.org/wiki/Image:Van_Allen_radiation_belt.svg
http://csep10.phys.utk.edu/astr161/lect/earth/magnetic.html
James Van Allen
• Sent a Geiger Counter on the first US satellite
Explorer 1
• The Geiger counter began clicking madly as soon
as it reached orbit
Auroras
• Auroras – natural light displays
• Collision of charged particles from Earth's
magnetosphere with atoms and molecules of
Earth's upper atmosphere
• The collisions in the atmosphere electronically
excite atoms and molecules in the upper
atmosphere. The excitation energy can be lost by
light emission or collisions.
• http://www.youtube.com/watch?v=pLi4T4JCALk
Any Questions?