With the website redesign complete, let's kick off the Digital Universe blog with some tips on manipulating data in Partiview. I am the first to admit that Partiview's user interface, while extremely powerful, is not the simplest UI to use. However, if you invest a little time, you can learn some sophisticated moves that will impress your friends.

I will focus today's post on the recently added 2MASS Galaxy Catalog. The catalog is wonderful for showing the enormous number of galaxies around the Milky Way. There are 1.14 million in this catalog (still, just the tip of the iceberg), but we do not show them all when you start up the Extragalactic Atlas. In fact, we only display 15% of the galaxies by default; your screen would be nothing more than a plethora of points if the full set was displayed.

Oh, you want to see that? Well, fire up the Extragalactic Atlas and turn on the 2MASS Galaxies.

Before we dive in, check out the data and preset selections available to you. In the 2MASS Galaxy Catalog section in the DU Guide, look over the tables that describe the data available, extra data associated with each galaxy, and the selection expressions that allow you to cull portions of these data.

We can use these expressions to selectively see different parts of these data if we learn how to use the command line (the gray box beside the "Cmd"). Using the Partiview command see, type see all to reveal all 1.1 million galaxies. Pretty crowded, huh?

Luckily, I have added some selection expressions to make it easy to manipulate these data. To return to the default state with 85% of the galaxies removed, type see lss. By removing the more isolated field galaxies in blue, the large-scale structure (hence, lss) is easier to see.

If you want to have a sense of the galaxy clusters that surround us, type see clusters at the command line and orbit Home. Our nearest neighbors are the Fornax Cluster, in the direction of Fornax in the sky, and the Virgo Cluster, the large, galaxy-rich cluster in the constellation of Virgo. Each of these clusters is a goldmine for astrophysicists, providing invaluable knowledge toward our understanding of galaxy clusters and superclusters.

Try some of the other 2MASS selection expressions to learn more about the galaxies that surround us. Next time, I'll discuss the various catalogs that make up the 2MASS Galaxies.

The speed of star formation from diffuse hydrogen gas has been a subject of strong controversy in the last decade. On one side, it is argued that magnetic fields act to support ionized interstellar gas against gravitational collapse. Then, almost every ion in the gas would need to find an electron to neutralize it before the gas could decouple from the magnetic field and collapse. This would suggest that it takes more than 10 million years to form a star. On the other side, it is argued that gas can slide along the magnetic field lines, allowing gas to accumulate and reach densities high enough for gravity to take hold and cause collapse, dragging the field lines with it. This suggests that a cloud will collapse into a star in only a few million years.

Young stars are deeply embedded within the collapsing clouds of gas and dust from which they form. While dust absorbs the visible light from those young stars, it emits strongly at mid-infrared wavelengths. By studying infrared images of galaxies, the star-forming regions are easily located within a galaxy's spiral arms.

In this study, the rotation of spiral arms through a galaxy is used to directly measure the time scale for star formation. The spiral arms rotate through the galaxy with a measurable speed. Therefore, a measurement of the distance between the peak of the gas emission (green contours) and the peak of the star formation emission (orange), will yield the time it took for the spiral arm to rotate through, and thus the time it took for the stars to form from the gas. The gas emission is observed using the hydrogen 21 centimeter radio emission.

Young stars are deeply embedded within the collapsing clouds of gas and dust from which they form. While dust absorbs the visible light from those young stars, it emits strongly at mid-infrared wavelengths. By studying infrared images of galaxies, the star-forming regions are easily located within a galaxy's spiral arms.

Measuring the relative positions of the star-forming emission versus the hydrogen gas emission in 14 galaxies resulted in time scales ranging from 1 to 4 million years, supporting the argument for fast collapse during star formation.

Welcome to the new Digital Universe blog. In this blog we will address a wide range of topics such as new data acquisitions, the science of the atlas, Partiview tips, and Digital Universe visualizations. We also hope to occasionally highlight your experience as a user. If you have experiences you'd like to share with the community, please submit them via e-mail (choose the Digital Universe category).

Stay tuned to this blog category for the latest on the Digital Universe.