Annual Report 2011 Max Planck Institute for Astronomy

8 I. General
lows us to understand this process under physical conditions
which can be very different from those in the Milky
Way. Our studies of star formation in the Magellanic
Clouds allow an investigation of the effect of metallicity
on the star formation process, which is certainly
an important factor in understanding star formation in
the early Universe. Stars are born in the dense and cold
cores of molecular clouds, which become gravitationally
unstable and, in general, fragment to form binaries
and multiple stellar systems. The role of magnetic fields
or turbulence in controlling the onset of star formation
remains one of the open key questions. This question is
immediately related to the shape of the initial (sub-) stellar
mass function in different environments. Dynamical
interactions in multiple systems may be a crucial factor
for the formation of Brown Dwarfs. Massive star formation
takes place in clusters, leading to complex starforming
regions. The rapid evolution of massive protostars
and the associated energetic phenomena provide an
enormous challenge in identifying the formation path of
massive stars.
Looking behind the curtain…
The earliest phases of star formation are obscured
by enormous amounts of dust and gas and can only be
detected by sensitive far-infrared and (sub-) millimeter
observations. At later evolutionary stages, the objects
“glow” at near- and mid-infrared wavelengths, and finally
become visible at optical wavelengths. Our observ-
like structure. It is composed of tidal star streams, the remnants
of a smaller satellite galaxy.
Credit: R. Jay Gabany, D. Martínez-Delgado Fig. I.1.2: The galaxy GC 4651 with its remarkable umbrella-
ing programs cover a wide range of wavelengths with a
special emphasis on infrared and (sub-) millimeter observations.
The formation of planets and planetary systems is a
natural by-product of low-mass star formation. Because
of angular momentum conservation, accretion of matter
onto the central protostar happens predominantly through
a circumstellar disk. Disks around T Tauri stars are the
natural birthplaces of planetary systems, resembling the
solar nebula 4.5 Gyr ago. During the active accretion
phase, bipolar molecular outflows and ionized jets are
produced, which in turn play an important role in the evolution
of star-disk systems. We are presently starting to
use protoplanetary disks as laboratories for understanding
the formation of our own solar system and the diversity of
other planetary systems detected so far.
The research of the Planet and Star Formation department
is focused on the understanding of the earliest
phases of stars, in both the low and high stellar mass
regime. Observations with space observatories such as
Spitzer, HST and herSchel, as well as ground-based infrared
and (sub-) millimeter telescopes, allow the detection
and characterization of massive protostars and their
subsequent evolution. The vigorous use of submillimeter
facilities is preparing the department for the Atacama
Large Millimeter Array (alMa), which will soon commence
operation.
The investigation of Brown Dwarfs, which were first
detected in 1995, is another important research topic.
How do Brown Dwarfs form? Are young substellar objects
also surrounded by disks? What is the binarity fraction
and the exact mass of these objects? What is the
composition of their atmospheres? These are among the
burning questions which are attacked by MPIA scientists.