The Hierarchical World of Star Formation
Star clusters may form in a similar way to the hierarchical formation of galaxies, let’s find out how it works!
Making stars the right size
Stars form in environments that are characterized by vastly different densities, pressures and metal content. Yet the sizes of the stars formed don’t vary substantially (as measured by the median mass). Why don’t the properties of the clouds out of which stars fragment have a stronger influence on the result? Why is there a characteristic stellar mass? Why is this mass scale similar to that for nuclear burning (the process that fuels stars)?
(photo: NASA via LANL, https://www.llnl.gov/news/newsreleases/2005/NR-05-11-10.html)
Review Article: Protoplanetary Disks and Their Evolution
In a new review article, Jonathan Williams and Lucas Cieza at the Institute for Astronomy (IfA) describe the life-story of protoplanetary disks from formation from collapsing molecular clouds to the end-state of a planetary system. Infrared telescopes like Spitzer and sub-millimeter radio telescopes like the the James Clerk Maxwell Telescope, the Submillimeter Array (SMA), and the Combined Array for Research in Millimeter Astronomy (CARMA) have greatly revolutionized the study of protoplanetary disks because they can probe the emission at the longer wavelengths where the disk emission is strongest.
Planet Formation at Wide Orbits through Gravitational Instability
Gravity can induce global instabilities in disks around stars, which then collapse to form planets at different radii.
Using Clumpy Streams to Detect Missing Satellites
Many simulations of our universe result in a similar discrepancy with current observations. The simulations predict an abundance of subhalos around galaxies the size of our Milky Way which are an order of magnitude higher than observations suggest. This paper tackles the issue of detecting these presumably faint subhalos by analyzing the effects they might have on streams from globular clusters and other satellite galaxies we know to exist.
Why are most molecular clouds not gravitationally bound?
In this paper, Dobbs, Burkert & Pringle suggest that most molecular clouds are not gravitationally bound, as is often assumed. They present simulations in which stellar feedback and collisions between clouds play a prominent role.