In the southern sky, about 4300 light-years from Earth, lies RCW 120, a huge luminous cloud of gas and dust. An international team led mainly by researchers from the University of Cologne and West Virginia University (USA) has now narrowed down the age of RCW 120 to less than 150,000 years, which is very young for such a nebula. The research revealed that stellar feedback – a process in which stars release energy back into their surroundings – positively influences star formation in the vicinity. These findings may shed light on the high rate of star formation in the early universe. The results have been published in the April issue of Science Advances (Luisi et al. 2021).
The research team studied the nebula onboard the SOFIA flying observatory – a converted Boeing 747 – to analyse the effects of stellar feedback. RCW 120 is a so-called emission nebula that emits light at different wavelengths. About seven light-years from the centre of RCW 120 lies the edge of the cloud, where an abundance of stars is forming. Delving deep into the nebula’s origins helps to understand the formation of all these stars. RCW 120 has a young, massive star at its centre that produces strong stellar winds. These winds are similar to those of our own Sun: they eject material from its surface into space. Stellar wind shocks and compresses the surrounding gas clouds. The energy added to the nebula triggers the formation of new stars in the clouds. Thus, the presence of the massive central star has a positive effect on future star formation.
These observations to study the interactions of massive stars with their environment are carried out as part of the SOFIA program FEEDBACK, an international project led by Dr Nicola Schneider of the University of Cologne and Professor Alexander Tielens of the University of Maryland, which uses the Max Planck Institute for Radio Astronomy’s upGREAT receiver installed on SOFIA in 2015.

SOFIA is a ‘flying observatory’ consisting of a 2.7-metre telescope carried onboard a modified Boeing 747SP aircraft. It is a collaboration between DLR (German Aerospace Center) and NASA and is coordinated by DSI (German SOFIA Institute) and USRA (Universities Space Research Association).

SOFIA observes in the infrared region of the electromagnetic spectrum, just beyond what humans can see. SOFIA’s flight altitude is above 13 kilometres. This allows the Boeing to fly above most of the water vapour in the Earth’s atmosphere, which blocks infrared light. Hence, the scientists can observe a wavelength range that is not accessible from Earth. At night, the in-flight observatory has its eye on celestial magnetic fields, star-forming regions such as RCW 120 as well as comets and nebulae.
‘We found out that RCW 120 is expanding at 15 km/s, which is incredibly fast for a nebula. From this expansion speed, we were able to derive an age limit for the cloud and found that RCW 120 is much younger than previously thought,’ said Dr Nicola Schneider. With this age estimate, the scientists were in turn able to infer the time it took for star formation at the edge of the nebula to gain momentum after the formation of the central star. These results suggest that positive feedback processes occur on very short timescales, and that these mechanisms may be responsible for the high rates of star formation that occurred in the early phase of the universe.

In the future, the team hopes to transfer this type of analysis to other star-forming regions. ‘The other regions we are studying with FEEDBACK are at different stages of evolution and have different morphologies. Some have many massive stars at their centre as opposed to RCW 120,’ Schneider said. ‘With this information, we can determine what processes mainly drive the triggered star formation and how these processes differ between the different star-forming regions.’

Media Contact:
Dr. Nicola Schneider
Institut für Astrophysik
+49 221 470-8353
nschneidph1.uni-koeln.de

Press and Communications Team:
Jan Voelkel
+49 221 470-2356
j.voelkelverw.uni-koeln.de

Publication:
https://advances.sciencemag.org/content/7/15/eabe9511

More information:
https://astro.uni-koeln.de/index.php?id=18130
https://feedback.astro.umd.edu/
https://www.mpifr-bonn.mpg.de/4480452/upgreat
https://www.nasa.gov/mission_pages/SOFIA
https://www.dlr.de/content/en/articles/missions-projects/sofia/sofia-infrared-observatory.html
https://www.dsi.uni-stuttgart.de/