Transcript radial velocity

Answers to all homework questions will be
posted on the class website
First exam: Monday, October 3.
If the wavelength of an electromagnetic wave
increases, its velocity
(red) Decreases
(yellow) Increases
(blue) Remains the same
(green) Not enough information
If the wavelength of an electromagnetic wave
increases, its velocity
(red) Decreases
(yellow) Increases
(blue) Remains the same
(green) Not enough information
If the wavelength of an electromagnetic wave
increases, its frequency
(red) Decreases
(yellow) Increases
(blue) Remains the same
(green) Not enough information
If the wavelength of an electromagnetic wave
increases, its frequency
(red) Decreases
(yellow) Increases
(blue) Remains the same
(green) Not enough information
If the wavelength of an electromagnetic wave
increases, its energy
(red) Decreases
(yellow) Increases
(blue) Remains the same
(green) Not enough information
If the wavelength of an electromagnetic wave
increases, its energy
(red) Decreases
(yellow) Increases
(blue) Remains the same
(green) Not enough information
You are an astronaut taking a spacewalk to fix your
spacecraft with a hammer. Your lifeline breaks and
the jets on your back pack are out of fuel. To return
safely to your spacecraft (without the help of
someone else), you should
a) throw the hammer at the space ship to get
someone's attention.
b) throw the hammer away from the space ship.
c) use a swimming motion with your arms.
d) kiss your ship good bye.
You are an astronaut taking a spacewalk to fix your
spacecraft with a hammer. Your lifeline breaks and
the jets on your back pack are out of fuel. To return
safely to your spacecraft (without the help of
someone else), you should
a) throw the hammer at the space ship to get
someone's attention.
b) throw the hammer away from the space ship.
c) use a swimming motion with your arms.
d) kiss your ship good bye.
The Doppler Shift:
 = v

c
A shift in wavelength due to a
wave emitter moving towards
(shorter wavelength) or away
(longer wavelength) from an
observer.
The Doppler Effect
1. Light emitted from an object moving towards
you will have its wavelength shortened.
BLUESHIFT
2. Light emitted from an object moving away from
you will have its wavelength lengthened.
REDSHIFT
3. Light emitted from an object moving
perpendicular to your line-of-sight will not
change its wavelength.
Measuring Radial Velocity
●
●
We can measure the Doppler
shift of emission or absorption
lines in the spectrum of an
astronomical object.
We can then calculate the
velocity of the object in the
direction either towards or
away from Earth. (radial
velocity)
 = v

c
Measuring Rotational Velocity
In conducting a search for
life, we must understand how
planets are formed and what
determines their habitability.
What does any theory of the
formation and evolution of the solar
System have to account for,
i.e., what are the “observed facts”?
The Sun:
A central star
Predominately H
and He
Most of the mass in
the solar system.
Rotates in same
sense that planets
orbit.
Terrestrial
Jovian
Two “flavors” of planets
Terrestrial Planets









Size:
Location:
distant
Composition:
Temperature:
Rings:
Rotation rate:
Surface:
Atmosphere:
Moons:
Jovian Planets
small
closer to Sun
rocky/metallic
hotter
none
slow
solid
minimal
few to none
large
more
gaseous/icy
colder
ubiquitous
rapid
not solid
substantial
many
Planetary orbits:
1) Prograde
2) approximately coplanar
3) approximately circular
Rotation:
1) Mostly Prograde
2) Includes sun
3) Includes large moons
There are large numbers of smaller
objects in the Solar System
 moons: both rocky & icy
 asteroids: rocky
 comets: icy
Craters are ubiquitous
on solid objects
Asteroids
small
Rocky
Odd-shapes
nearly circular orbits
orbit planes are near Ecliptic Plane
orbits in inner part of solar system
The
“asteroid belt”
Comets
small nucleus
“dirty snow ball”
very large tails
highly eccentric orbits
all orbit inclinations
Comets are found mainly in two regions of
the solar system
Largest Known Kuiper Belt Objects