Massive Star Formation

UCHII 
regions viewed in the mid-IR
GHII
RCW49 seen with Spitzer GLIMPSE survey

The birth of massive stars remains a major puzzle for theorists and observers alike. What we do know is that they are formed within Giant Molecular Clouds (such as Orion). Once the hot star starts to `shine', it illuminates its dense surrounding region - which is called an UltraCompact HII region - the surrounding material prevents direct observation of the star until the natal gas has been blown away, but one can study the birth environment of massive stars at radio and mid-infrared wavelengths - as shown here for two Galactic UCHII regions, based on observations with the Midcourse Space Experiment. Near-IR spectroscopy from VLT/ISAAC has provided robust classification of the ionizing star of the G23.96+0.15 UCHII region, only the second such case due to high interstellar and circumstellar dut extinction. New observations are also being made with the Spitzer mid-IR telescope, primarily throught the GLIMPSE survey, shown on the right for RCW49, plus our own IRAC and IRS study of the W31 star forming region.