1. Consider two stars with apparent magnitudes 0 and 3. Which is brighter to our eyes, and by how much?
2. When we say that distant galaxies are "red shifted", what is happening and why?
3. Draw a rough picture of the H-R diagram and identify: the axes, Main sequence, locations of other star types. Also, what is the general significance of the H-R diagram?
4. Why do we care about other types of (non-visible) electromagnetic radiation emitted from stars, galaxies, etc?
5. Define and distinguish between a light-year and a parsec.
6. Consider an asteroid orbiting the Sun with a semi-major axis of 3 AU. Assume that the orbit is pretty elliptical.
a. Draw a labeled picture to represent this.
b. Where is it traveling fastest and slowest?
c. How long does it take to orbit the Sun once?
Monday, April 4, 2016
Thursday, March 31, 2016
Project topics
Black holes
White dwarfs
Giants/Supergiants
Pulsars
Neutron stars
Halley's armada
Webb Space telescope
Hubble Space telescope
Mission to Mars
Extrasolar planets
Space race
Strategic defense initiative
Big Bang
Radio astronomy
Big Crunch?
Data from meteorites (shooting stars)
The Drake equation
Determining the ages of space objects
Moons of other planets - modern data
Asteroid expeditions
Time travel ???
General relativity
Special relativity (time dilation, length contraction)
String theory
Quantum Mechanics
Variable stars
Voyager
Mariner
Apollo
Mercury
Pioneer
Speed of light - how to measure
Space elevator?
White dwarfs
Giants/Supergiants
Pulsars
Neutron stars
Halley's armada
Webb Space telescope
Hubble Space telescope
Mission to Mars
Extrasolar planets
Space race
Strategic defense initiative
Big Bang
Radio astronomy
Big Crunch?
Data from meteorites (shooting stars)
The Drake equation
Determining the ages of space objects
Moons of other planets - modern data
Asteroid expeditions
Time travel ???
General relativity
Special relativity (time dilation, length contraction)
String theory
Quantum Mechanics
Variable stars
Voyager
Mariner
Apollo
Mercury
Pioneer
Speed of light - how to measure
Space elevator?
Spring Observing Lab
Lab 5 - Observing II: The Spring Sky
Despite the rain, the late winter
and early spring skies present some good opportunities for viewing. Heat haze is low, though precipitation can be
a problem for telescopes. In this lab,
you will locate several gems of the spring sky, drawing and identifying what
you see. So get out there and dig the
night sky!
Note: On sky maps, relative brightnesses are
indicated by the size of the dots. Also,
you may find it useful to use the reverse side of the chart to answer some of
the other questions. Also, skymaps.com
is a good resource to use.
1. If you look directly
overhead (to the zenith), what do you see?
2. What constellation(s) lie
directly overhead?
3. What asterism(s) are
visible?
4. What are the brightest objects
visible tonight? Name and locate them.
5. What are the stars of the
Summer Triangle? Can you see any of them
yet?
6. Find the Big Dipper. Can you see the double star in the handle? Can you see any other stars of Ursa Major?
7. Follow the arc of the handle
toward the next bright star. What star
is this?
8. Follow the pointer stars of
the Dipper to the next bright star (Polaris).
Draw the Dipper and Polaris as you see it. Can you see any other stars of Ursa Minor?
9. Is Polaris especially
bright? That is, is it one of the 5
brightest stars visible tonight?
10. Continuing on, following the
pointer stars past this star and curving a bit, find Cassiopeia. Draw what you see.
11. What is the lowest object
you can see on your horizon?
12. What planet(s) is/are
visible at this time?
13. Can you detect any color in
stars or planets? Comment.
14. What Messier (M) objects
should be visible (through a telescope) this evening?
15. List other interesting
events worth viewing this month.
16. How have the skies changed
since you first observed back in the winter?
17. Comment on the general
viewing conditions in your region.
Questions
1. What are the easiest ways to tell the
difference between a star and a planet?
2. When is the next full Moon?
Star Stuff 4 - Star Types
There are 4 fundamental forces of nature:
Strong nuclear - this keeps protons close together
Weak nuclear a responsible for radioactive decay
Electromagnetism - light, electricity, magnetism, etc
Gravity - weakest of all, but furthest reaching
A star (Latin root stella-) is essentially a ball of gas powered by nuclear reactions, held together by gravity.
Stars may appear white, but their color is a combination of many colors (and non visible e-m waves like UV).
Spectral types are listed in order of decreasing temperature:
O B A F G K M
with a temperature range from 60,000 K down to under 3500 K.
There are further subdivisions (C and S stars under M).
You can learn a lot about a star from where it lies on the Hertzsprung-Russel diagram.
The H-R diagram plots magnitude (brightness, from dim to bright) vs. temperature (high to low, usually as spectral type).
Hottest stars are on the left if the graph - they are normally brighter than cooler stars.
Most stars fall on along a diagonal band from upper left to lower right on the H-R diagram. We call this the Main Sequence, and the stars there are main sequence stars or dwarfs (which is a misleading term).
Stars above and to the right of the MS are giants (including supergiants).
Faint hit objects (white dwarfs) are below and to the left of the MS.
Our own Sun is a G2 star, somewhere close to 4.6 billion years old.
>
Strong nuclear - this keeps protons close together
Weak nuclear a responsible for radioactive decay
Electromagnetism - light, electricity, magnetism, etc
Gravity - weakest of all, but furthest reaching
A star (Latin root stella-) is essentially a ball of gas powered by nuclear reactions, held together by gravity.
Stars may appear white, but their color is a combination of many colors (and non visible e-m waves like UV).
Spectral types are listed in order of decreasing temperature:
O B A F G K M
with a temperature range from 60,000 K down to under 3500 K.
There are further subdivisions (C and S stars under M).
You can learn a lot about a star from where it lies on the Hertzsprung-Russel diagram.
The H-R diagram plots magnitude (brightness, from dim to bright) vs. temperature (high to low, usually as spectral type).
Hottest stars are on the left if the graph - they are normally brighter than cooler stars.
Most stars fall on along a diagonal band from upper left to lower right on the H-R diagram. We call this the Main Sequence, and the stars there are main sequence stars or dwarfs (which is a misleading term).
Stars above and to the right of the MS are giants (including supergiants).
Faint hit objects (white dwarfs) are below and to the left of the MS.
Our own Sun is a G2 star, somewhere close to 4.6 billion years old.
>
Friday, March 18, 2016
Good video
Brian Cox is a British astrophysicist who has produced some great BBC documentaries over the past few years. Here is episode 1 of his "Wonders of the Universe" series. Some of us watched part of it on Friday.
http://www.dailymotion.com/video/xyr1ly_wonders-of-the-universe-destiny_shortfilms
He also has a "Wonders of the Solar System" series and a "Wonders of Life" series. All good stuff.
http://www.dailymotion.com/video/xyr1ly_wonders-of-the-universe-destiny_shortfilms
He also has a "Wonders of the Solar System" series and a "Wonders of Life" series. All good stuff.
Star Stuff 3 - The Doppler Effect
You have no doubt heard about the Doppler Effect - what is it exactly? The key in the Doppler effect is that motion makes the "detected" or "perceived" frequencies higher or lower. We will consider this first for sound and then generalize to light.
Let's play around with this:
Let's play around with this:
http://www.lon-capa.org/~mmp/applist/doppler/d.htm
How how the number of waves you receive per second will be the same regardless of where you stand, UNLESS the source is moving. And then:
How how the number of waves you receive per second will be the same regardless of where you stand, UNLESS the source is moving. And then:
If the source is moving toward you, you detect/measure a higher frequency - this is called a BLUE SHIFT.
If the source is moving away from you, you detect/measure a lower frequency - this is called a RED SHIFT.
If the source is moving away from you, you detect/measure a lower frequency - this is called a RED SHIFT.
It's worth noting that the effect also works in reverse. If you (the detector) move toward a sound-emitter, you'll detect a higher frequency. If you (the detector) move away from a sound-emitter, you'll detect a lower frequency.
Mind you, these Doppler effects only happen WHILE there is relative motion between source and detector (you).
And they also work for light. In fact, the terms red shift and blue shift refer mainly to light (or other electromagnetic) phenomena.
If your computer runs Java:
If your computer runs Java:
http://falstad.com/mathphysics.html
Run the Ripple tank applet -
http://falstad.com/ripple/
Distant galaxies in the universe are moving away from us, as determined by their red shifts. This indicates that the universe is indeed expanding (first shown by E. Hubble). The 2011 Nobel Prize in Physics went to local physicist Adam Riess (and 2 others) for the discovery of the accelerating expansion of the universe. Awesome stuff!
http://www.nobelprize.org/nobel_prizes/physics/laureates/2011/
Star Stuff - 2, Electromagnetic Waves
Recall that waves can be categorized into two major divisions:
Mechanical waves, which require a medium. These include sound, water and waves on a (guitar, etc.) string
Electromagnetic waves, which travel best where there is NO medium (vacuum), though they can typically travel through a medium as well. All electromagnetic waves can be represented on a chart, usually going from low frequency (radio waves) to high frequency (gamma rays). This translates to: long wavelength to short wavelength.
All of these EM waves travel at the same speed in a vacuum: the speed of light (c). Thus, the standard wave velocity equation becomes:
where c is the speed of light (3 x 10^8 m/s), f is frequency (in Hz) and the Greek letter, lambda is wavelength (in m).
Mechanical waves, which require a medium. These include sound, water and waves on a (guitar, etc.) string
Electromagnetic waves, which travel best where there is NO medium (vacuum), though they can typically travel through a medium as well. All electromagnetic waves can be represented on a chart, usually going from low frequency (radio waves) to high frequency (gamma rays). This translates to: long wavelength to short wavelength.
All of these EM waves travel at the same speed in a vacuum: the speed of light (c). Thus, the standard wave velocity equation becomes:
where c is the speed of light (3 x 10^8 m/s), f is frequency (in Hz) and the Greek letter, lambda is wavelength (in m).
General breakdown of e/m waves from low frequency (and long wavelength) to high frequency (and short wavelength):
Radio
Microwave
IR (infrared)
Visible (ROYGBV)
UV (ultraviolet)
X-rays
Gamma rays
In detail, particularly the last image:
http://www.unihedron.com/projects/spectrum/downloads/full_spectrum.jpg
Don't forget - electromagnetic waves should be distinguished from mechanical waves (sound, water, earthquakes, strings on a guitar/piano/etc.).
Don't forget - electromagnetic waves should be distinguished from mechanical waves (sound, water, earthquakes, strings on a guitar/piano/etc.).
ALL E/M waves (in a vacuum) travel at the SPEED OF LIGHT (c).
Subscribe to:
Posts (Atom)