Asteroid Belt

Asteroid Belt

Beyond Mars, which marks end of inner solar system, lies a particularly huge space.  On the other side is massive planet Jupiter.  It is in this huge space that Asteroid Belt exists.  Thousands of large and small tumbling rocks is what Asteroid Belt is made up of.  There are four types of asteroids that current Asteroid Belt consists of, carbonaceous asteroids, silicaceous asteroids, metallic asteroids and rare basaltic asteroids.

Carbonaceous asteroids are most common type and make up large percentage of Asteroid Belt and its outer regions.  They are carbon rich and consist of organic compounds.  An interesting article can be found at http://www.psrd.hawaii.edu/April11/amino_acids.html

Silicaceous asteroids are second most common type and make up majority of inner region” of Asteroid Belt.  These types asteroids are mainly composed of iron and magnesium silicates and a very few even show hint of organic compounds.  This tells us that their “materials have been significantly modified from their primordial composition, most likely through melting and reformation”.

Metallic asteroids are third most common type of asteroids.  Their compositions are not fully known, but many consist of nickel, iron and a little stone.  This class of asteroids is not fully understood and it appears there may be several different types.

Basaltic asteroids are considered rare and are mystery in Astrophysics.  They are composed of extrusive volcanic rock and mineral olivine, which is magnesium iron silicate.  If you are interested, you can read more about these mysterious types of asteroids here.

There are main-belt comets that orbit within Asteroid Belt which tend to stay in outer part of belt.  There are also spaces, known as Kirkwood Gaps, cleared where orbital resonances with Jupiter occur.  Orbital Resonance occurs when two orbiting bodies exert a regular, periodic gravitational influence on one another.”  The largest gap is at orbital distance which would correspond to period of one third that of Jupiter.

The most massive of all the asteroids is Ceres , comprising over one third of total mass of all of asteroids.  It is considered a dwarf planet, smallest one in our solar system, and only dwarf planet to exist in Asteroid Belt. 

Asteroid Belt is highly unlikely to be remains of a small planet because no sizeable body could ever have formed so close to Jupiter.

Sources:

http://en.wikipedia.org/wiki/Asteroid_belt

http://www.psrd.hawaii.edu/April11/amino_acids.html

Magnetic Field of a Neutron Stars

A neutron star is stellar remnant that results from the gravitational collapse of a massive star (between 8 to 20 solar masses). Even though neutron stars are composed of almost entirely neutrons, they have very strong magnetic fields.

To understand why a neutron star has a huge magnetic field, let's look at its structure.

The structure

This model hasn't been proven, but it gives very good understanding of neutron stars and reveals many known properties of neutron stars. The surface of a neutron star is composed of ordinary nuclei with a sea of free electrons flowing around them. Most of the nuclei are left over hydrogen, helium and iron. The atmospheres of these stars, according to recent hypothesis, could be at most several micrometers. This is because of the intense gravity on the surface. A calculation of gravity is here. This is approximately 10^12 times stronger than earth's gravity.

A little deeper into the star, the gravity gets strong enough so that neutrons leak out of nuclei and become free neutrons. As we dig dipper and dipper, the nuclei becomes smaller and smaller until the core is reached where nuclei disappear. The composition of the super dense core remains uncertain.

Angular velocity

To get a rough estimate of angular velocity, we can assume that angular velocity is conserved.
Here is a sample calculation. We can get something like several rotations per second!!!

Magnetic Field

Here is a rough calculations of neutron stars' magnetic field assuming charge density is uniform in spherical shell shape. This shell can have a lot of surface charge density since there is a sea of electrons. If we estimate the magnetic field of rotating charged sphere, then the below picture shows that neutron stars can have magnetic fields like 50,000 Tesla. Compare that to earth's magnetic field (0.0001 Tesla) or maximum magnetic field produced on earth (100 Tesla).

Here is a link to the interactive CDF file to explore magnetic field of neutron star with different parameters.
Click here to download

Sources
Wikipedia Neutron Star
Magnetic Field of a rotating Sphere Estimates

Last minute studying

(I have added more stuff)

Dear Classmates,

Here are all the notes that I have been writing throughout the class. Some of them include helpful simulations and diagrams.
Hopefully this will help.

You should be able to open PDF versions in the browser (just click on it). Other formats files will need to be downloaded.

CDF file will open with wolfram CDF player. It is free. Here is a link
.nb file will open with mathematica.


Evolution of post-main sequence star. (This is not perfect. I might have mistakes. Check it out if you are completely lost, like i was a day ago.)
Star Evolution
Death Of Stars

Important! How to calculate flux and luminosity form blackbody equation (plank's equation). PLUS Some equations that are not in the equation sheet, and other short notes about calculating mass in binary and radial velocities.
Notes

Classification of Stars and formation of spectral lines
http://dl.dropbox.com/u/58867372/Astrophysics/Classification%20of%20Stars%2C%20Formation%20of%20Spectral%20Lines.cdf
http://dl.dropbox.com/u/58867372/Astrophysics/Classification%20of%20Stars%2C%20Formation%20of%20Spectral%20Lines.nb
http://dl.dropbox.com/u/58867372/Astrophysics/Classification%20of%20Stars%2C%20Formation%20of%20Spectral%20Lines.pdf

Interiors of stars
http://dl.dropbox.com/u/58867372/Astrophysics/Interior%20of%20Stars.cdf
http://dl.dropbox.com/u/58867372/Astrophysics/Interior%20of%20Stars.nb
http://dl.dropbox.com/u/58867372/Astrophysics/Interior%20of%20Stars.pdf

Star Formation
http://dl.dropbox.com/u/58867372/Astrophysics/Star%20Formation.cdf
http://dl.dropbox.com/u/58867372/Astrophysics/Star%20Formation.nb
http://dl.dropbox.com/u/58867372/Astrophysics/Star%20Formation.pdf

Steller Atmospheres
http://dl.dropbox.com/u/58867372/Astrophysics/Steller%20Atmosphere.cdf
http://dl.dropbox.com/u/58867372/Astrophysics/Steller%20Atmosphere.nb
http://dl.dropbox.com/u/58867372/Astrophysics/Steller%20Atmosphere.pdf

Binary System (This one is not so great. I haven't finished making it.)

http://dl.dropbox.com/u/58867372/Astrophysics/Binary%20Systems.cdf

http://dl.dropbox.com/u/58867372/Astrophysics/Binary%20Systems.nb

http://dl.dropbox.com/u/58867372/Astrophysics/Binary%20Systems.pdf

Spectral Lines and Classification of Stars

Do you know how to interpret Hertzsprung-Russell Diagrams?
Do you know why do spectral lines have widths?
Do you know why we see strong hydrogen absorption in certain stars and not other?

All of these questions are answered in Chapter 8 (30 pages) of our book. I have written detailed, interactive, notes about this chapter that I would like to share. I have included interactive plots and diagrams to help us understand and explore these questions. It also includes small applications to solve for saha, boltzmann, and other equations.

Hopefully this information helps you.

Here are links to the files. I highly recommend you use Wolfram CDF (Its free, click here). PDF version is dull and boring. CDF player will let you interact with plots.

PDF version
Wolfram CDF version
Wolfram Mathematica version

Declination and Right Ascension

Here is the link to the Word document I created
Here is the link to the Google Docs page. 
I could not insert all the equations and formatted text into blogger.

Upgrading Hubble to Hubble 2.0

Hubble Space Telescope

HST Diagram

Hubble space telescope observes the universe 24 X 7. It collects tons of raw data, basically numbers in columns. Transferring these data to the earth and converting numbers to images requires extraordinary technologies and considerable amount of men power.

Monitoring and maintenance  of Hubble telescope is done by hundreds of scientists, engineers, and technicians at both NASA's Goddard Space Flight Center and the Space Telescope Science Institute (STScI). They monitor its health, safety, and performance.

Ground Control Team at Goddard
Space Flight Center

Hubble's Ground Control :-
The Flight Operation Team at Goddard Space Flight Center monitors telescope's health and daily movements. The controllers direct Hubble's movements by sending commands via satellite to the telescope's on-board computer. The majority of Hubble's operations are programmed in advance, but controllers can also interact in real time with the spacecraft, telling it what to do and when to do it.

Upgrading Hubble :-
Hubble service missions (SM) are also very important in Hubble's better health and upgrades. There have been four of these service missions since its launch.


Restoring Hubble's Vision (SM1):-
Main objective was to install two devices to fix Hubble's vision. Two new instruments were also installed during this mission to improve Hubble's vision too. This successful mission not only improved Hubble's vision - which led to a string of remarkable discoveries in a very short time - but it also validated the effectiveness of on-orbit servicing.





Expanding Hubble's Universe (SM2) :-

Making Use of the Shuttle's Remote
Manipulator System (RMS)

This mission gave Hubble new infrared cameras to detect red-shifted radiation (this happened after the realization that the universes is expanding in a accelerating fashion). Another detector was also placed to detect black holes during this 10 day service mission.









Long Distance House Call (SM3A and SM3B) :-
Watch Pictures and Videos

This mission was dedicated to upgrading and fixing small things. They replaced small things like gyroscopes (plays very important role in pointing in right direction). In addition, an advanced central computer was also installed to efficiently store and transfer data. Hubble was given better power system, better infrared vision, and new steering equipments.






Making Hubble 21st century device (SM4) :-
Watch The Video of SM4 coverage



This is the last mission planned by NASA to upgrade Hubble. Hubble was equipped with even better instruments like Wide Field Camera 3, Wide Field and Planetary Camera 2, and Cosmic Origin Spectrograph. Since SM4 is expected to be the last astronaut mission to Hubble, one of the goal was to reinforce and reinvigorate the telescope's basic spaceflight systems. The team changed all of the batteries, gyroscopes and fine guidance system. This mission prepared Hubble to explore the universe for another 20 years.



Sources :-
http://hubblesite.org/the_telescope/team_hubble/
http://hubblesite.org/the_telescope/team_hubble/servicing_missions.php
http://hubblesite.org/the_telescope/team_hubble/access_hubble/
http://sm3a.gsfc.nasa.gov/gallery.html

Could we be living inside a Black Hole?

Just a thought.

It makes sense!