The Great Red Spot by Voyager 1

Sorry for the gigantic image, but it was just too cool to pass up (Edit: The image has been resized to fit better. NASA loves to show things at uber-resolution, unfortunately that doesn't work too well when showing it in a blog. The full res image can be found at APOD). Courtesy of today's APOD we have an exquisite picture of Jupiter's Great Red Spot taken by Voyager 1 as it passed by in 1979. To be honest this picture looks more like a painting than an actual image of a real event, but such is the way of many astronomical images.

The Great Red Spot is an incredible storm that has been raging for over 400 years on Jupiter. No one is quite sure how it started or why it is so long lived. It is huge though being so large that two Earths could easily exist inside of it, with winds topping out at about 400 km/h.

While it looks like a giant hurricane, the Great Red Spot is actually anticyclonic. This means the Great Red Spot rotates the wrong way with respect to the expected Coriolis forces. Instead the Great Red Spot is a fantastic example of a classic fluid instability called the Kelvin-Helmholtz instability. In this instability you have two fluids adjacent to each other, each flowing in opposite directions. This forms a shear layer between the two fluids. If one perturbs the boundary between the fluids, one creates and instability which will grow mixing the fluids. This mixing pattern can form into a stable configuration known as a cat's eye, of which the Great Red Spot is an excellent example. Simulations of this instability can be found here.

The probe that took these pictures, Voyager 1, is now long gone from Jupiter. It is now on a trip out of the Solar System and is investigating other interesting astrophyisical fluid dynamics. In this case it is looking at how the wind generated by our Sun interacts with the surrounding Interstellar Medium (ISM). Currently Voyager 1 has entered what is known as the Heliopause. In this region the Solar wind slows down and stops as it interacts with the ISM. This creates a contact discontinuity between the Solar Wind and the ISM. When Voyager 1 leaves this area it will finally enter into interstellar space for the first time. This will be our first chance to directly probe what interstellar space look like rather than relying on telescopes. Voyager 2 is also on the same path and will join its sibling out in interstellar space soon after Voyager 1 gets there.

On a side note, in my previous post I mentioned Endeavour's impending launch. The launch has been delayed due to a heater malfunction. The earliest date for a retry won't be until May 8th. However, that is subject to change as any further problems are found. Once a firm date is set I will try to post a note here.

Endeavour's Final Flight and Asteroid Collisions

Despite some crazy storms rolling through the US south-east, the final flight of the space shuttle Endeavour is slated to go at 3:47pm EDT today. The above picture was taken during the night before the launch. While lightning and rocket fuel don't normally mix, NASA has lightning rods stationed all over the place to absorb the impacts and keep the shuttle safe.

Endeavour is carrying, among other payload, the AMS (Alpha Magnetic Spectrometer). This 7 ton instrument will be attached to the International Space Station and has a primary science mission of 3 years. The goal of the AMS is to detect and identify the types of cosmic rays in space. This is important because ground detectors of cosmic rays have a difficult time identifying the specific types of particle a cosmic ray is. It can generally say whether it was an electron, photon or atomic particle, and generally how massive it is. However it cannot identify which specific element it is, nor can it figure out if it is something more exotic like antimatter.

The AMS is basically a like taking a smaller version of one of the Large Hadron Collider particle detectors and flying it in space. So it has the capability to detect the type and energy of the particles that pass through it. Since it is so big it will also be able to probe high energies, which is extremely useful for cosmic ray physics and particle physics in general. The AMS will also provide a very accurate measure of what the radiation environment in space is like. This will be crucial for planning future manned space flights, especially interplanetary flights as precautions need to be taken to protect the astronauts from the dangerous radiation that permeates space.

You can join the other 750,000 people who will be watching the launch by watching it live on NASA TV. Any launch, particularly a shuttle launch is a sight to behold. Unfortunately I will be judging a science fair at the time so I can't watch.

Another interesting story came of NASA yesterday regarding a collision that happened between two asteroids. While the event itself was observed with a smaller telescope, both Swift and Hubble took a look at it shortly after the collision. The images show dust and debris being flung off of the impacted asteroid called Scheila. From the impact and comparing it to the Deep Impact event we know that the impactor was about 30 meters across and moving at about 11,000 mph. Scheila itself is about 70 km and lives in the Asteroid Belt between Mars and Jupiter. This is the first time this type of event has been observed so soon after the impact, excluding of course man made impacts. These type of impacts tell us a lot about the object that got hit as it excavates material from the asteroid that we would normally not see. Analyzing the debris can tell us about what the asteroid is made of. A link to the press release is below:

http://www.nasa.gov/topics/universe/features/asteroid-collision.html