Massive Star Formation
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.
- Near and Mid Infrared Observations of Ultracompact HII Regions, Crowther (2005)
- On the central ionizing star of G23.96+0.15 and near-IR spectral classification of O stars Crowther & Furness 2008
- Mid-Infrared diagnostics of metal-rich HII regions from VLT and Spitzer Spectroscopy of Young Massive Stars in W31 Furness et al. 2010