January 8, 2013 — Jeffrey Bryant, Scientific Information Group
The physics involved in simulating galaxy collisions can be extremely complex. The most accurate simulations take into account not just points representing stars, but also magnetic fields and invisible dark matter, as well as n-body interactions allowing the individual stars to interact with each other. These complex simulations are usually carried out on large-scale supercomputers over long periods of time. One of the more interesting aspects of galaxy collisions is that they can create density variations resulting in all kinds of emergent structure. Density waves can develop that lead to star formation from compressed gas clouds.
A couple of years ago, I wrote a Demonstration that provides a simplified solution to galaxy collisions. This Demonstration is designed to run in real time inside a Manipulate, so the problem has been simplified by removing n-body interactions, dark matter, magnetic fields, and so on. Basically, it treats the two galaxies as large point masses with lots of massless test particles orbiting them. The test particles respond only to the two galaxy “centers.” In a real galaxy collision, the chances of two stars getting close enough to each other to interact directly is very remote, so it’s not too far of a stretch to ignore this effect for a first-order approximation. The more stars that are included in the simulation (by minimizing the star separation parameter), the more intricate the results (and the more computationally intense). In fact, as more stars are added, it becomes easier to see density variations where many test masses cluster together, but it still looks very discrete. Real galaxies, like the Milky Way, can have hundreds of billions of stars. Trying to carry out a point simulation with that many stars becomes a bit taxing on most home systems, and definitely exceeds the time constraints of a real-time dynamic tool like Manipulate. So how can we better visualize these density variations? I decided to try to modify my Demonstration to use one of the new features in Mathematica 9, namely volumetric rendering. This way, we can simulate the galaxy collisions with fewer numbers of points, but render the results as if there were billions of stars, resulting in a more realistic and informative visualization.
December 27, 2010 — Tom Sherlock, User Interface Group
Here is a shot I took of M27, the famous Dumbbell Nebula, with my home-brew 90mm astrograph and inexpensive equatorial mount.
Actually, it isn’t a single shot, but a combination of about 30 fairly short exposures, added together. Adding together short subframes rather than taking a single longer exposure makes it possible to create astrophotos without additional equipment for “guiding” the telescope. Guiding means applying small corrections, either manually or automatically, during the exposure to compensate for imperfections in either the mount’s alignment away from the polar axis or the mount’s drive mechanism. Combining the subframes has the additional benefit of reducing noise and increasing the signal to produce a result similar to a much longer exposure.
September 13, 2010 — Jeffrey Bryant, Scientific Information Group
Almost everyone has heard of the asteroid belt. This is the place between the orbit of Mars and Jupiter that is home to a very large percentage of the known minor planets in the solar system. Movies love to have space battles in asteroid belts to add to dramatic dogfight scenes. Even the Star Wars universe pays homage to asteroids: in The Empire Strikes Back, C3PO makes a popular statement about the possibility of successfully navigating an asteroid field.
Popular fiction, especially in Hollywood, loves to twist reality for cinematic effect. Often it shows an asteroid belt as an intricate maze of chaotically tumbling boulders that are moving at high speeds relative to each other, requiring advanced evasion techniques to avoid hitting one of them. They are also often shown to collide with each other at high speed, resulting in large explosions.
In reality, at least for our asteroid belt, things are not quite so dramatic. If you were actually in our asteroid belt, the chances that you would see an asteroid are fairly small. Most of them are quite small relative to the Earth and the space between them is relatively large. NASA has sent numerous probes through the belt, and not one has had an accidental encounter with an asteroid, although there have been a couple of intentional encounters. We know very little about the physical characteristics of asteroids compared to planets. Very few have been visited. However, their orbital dynamics are well studied and show some pretty amazing features. Let’s take a look at a view of all of the asteroids used in Mathematica‘s AstronomicalData out to the orbit of Jupiter.
October 6, 2009 — Jeffrey Bryant, Scientific Information Group
The Sloan Digital Sky Survey (SDSS) is an ongoing endeavor to map the sky in great detail, with many different goals. One of the larger objectives is to map the structure of the cosmos by determining the positions of galaxies and their relativistic redshift (basically their distance). Using this data and Mathematica, you can plot the information and reveal the structure of the cosmos.
In my spare time, I queried the SDSS website, which is database driven, and in eight separate queries I was able to get all galaxies in the survey out to a redshift of 0.5. According to Wolfram|Alpha, this corresponds to looking back in time 5.02 billion years ago, or a distance of 6.14 billion light years, when the light we’re now seeing from the most distant galaxies started its journey here. That’s a billion years before our solar system formed. It’s taken this long for the light to reach us.
March 3, 2009 — Jeffrey Bryant, Scientific Information Group
In this day and age, it’s quite common to have to do some housecleaning on your computer to make room for more clutter. While moving stuff around on my home computer and trying to figure out what data I had and where it could be moved to free up space on my hard drive, I ran across an old FITS data file from my college days. The cryptic filename only told me that it was taken in May and that it was likely the 132nd image in a sequence. I was curious and decided I would investigate it to see what I had uncovered. Perhaps it was a dull star-field image from my data-collecting days in the study of dwarf novae; I wasn’t sure. Mathematica was the most convenient tool I had handy for viewing FITS data, so I decided to take it for a spin.
June 11, 2008 — Jeffrey Bryant, Scientific Information Group
As an astronomy enthusiast, I try to keep up on all the various goings-on in astronomy news. Astronomy, being a primarily visual science, often lends itself quite well to computer visualization. Recently, NASA landed on Mars again, this time near one of the Martian poles in an attempt to study the ice and landscape of this frigid region. Is there water ice there, or just dry ice made of frozen carbon dioxide? How much of each? That’s what the Phoenix Mars Lander was sent to try to unravel.
As an editor for The Wolfram Demonstrations Project, I often get quite interested in new astronomy-related Demonstrations. One particular set, written by Sándor Kabai, focuses on the mechanics of not only the Phoenix Mars Lander, but probes from the past as well.
Landers, as opposed to other spacecraft, must overcome unique design challenges. Unlike orbiters, which typically have only sensors and cameras, landers usually have mechanical components to directly manipulate the surrounding environment like an astronaut could. These components come in many forms, such as wheels, scoops, drilling instruments, and so on, which make landers much more interesting to visualize interactively. Although these are not strictly astronomy, more engineering, few would argue that they are space-related and therefore pretty cool!
February 20, 2008 — Jeffrey Bryant, Scientific Information Group
Every so often, more often than you might think, a lunar eclipse happens somewhere in the world. Tonight, there will be a total lunar eclipse visible from the United States and numerous other regions. This can only happen when there is a full moon, but not every full moon results in a lunar eclipse. If the moon is directly along a line drawn from the Sun to the Earth, then the Earth’s shadow falls across the face of the moon, typically giving it a reddish hue. If you aren’t afraid of a little bit of cold weather and weather permits, you might try to see the eclipse yourself.
You can study eclipse phenomena, both solar and lunar, in real-time using this Demonstration.