Title: Star Formation: Jets, explosions, N-body interactions

Speaker: John Bally (University of Colorado Boulder)

Special Time: 10:00, Thursday, 22 October 2026

Tencent Meeting: 478-641-728

Location: Lecture Hall, 3rd floor

Invited by: Xing Lu

Abstract：

Stars form from the gravitational collapse and fragmentations of turbulent clouds which mostly lead to the birth of dense but short-lived, transient clusters. Collapse is opposed by the "Feedback Ladder" of ever more powerful feedback mechanisms as stars gain mass.   Most forming stars drive jets and bipolar outflows while they accrete. Massive stars ionize their environments, drive stellar winds, and eventually explode as supernovae.  These processes disrupt the natal clouds. The nearest massive star forming region, Orion, was the site of a ~10^48 erg protostellar explosion about 550 years ago (that is when the signal reached Earth).  Debris is still expanding through the gas immediately behind the Orion Nebula.  The explosion was associated with the ejection of three runaway stars, one of which is likely a merger remnant.  This event was triggered by the N-body interaction of at least 4 stars.  Among massive stars, protostellar explosions occur at least once a century in the Milky Way, comparable to the Galactic supernova rate. Dynamical ejections also occur in low-mass star forming regions; N-body interactions, combined with feedback, may determine final stellar masses.   I will discuss the implications of these results for the formation of massive stars and the IMF.  The talk will be illustrated with lots of observations.

CV：

John Bally is a professor of astrophysics at the University of Colorado Boulder, where he has served since 1991. Born in Hungary, he emigrated to the United States at age nine. He studied at the University of California, Berkeley, and earned his PhD in millimeter-wave radio astronomy from the University of Massachusetts Amherst in 1980.

Before joining Colorado, he spent 11 years at AT&T Bell Laboratories, studying molecular clouds, protostellar jets and outflows, and millimeter-wave instrumentation. He also participated in expeditions to establish the first permanent astronomical observatory at the South Pole.

His research focuses on star and planet formation, the interstellar medium, and stellar feedback. Using major facilities including Hubble, JWST, and ALMA, he investigates star-forming molecular clouds, the Milky Way's Central Molecular Zone, and jets and shocks driven by young stars. More recently, he has focused on massive star formation and explosive outflows associated with stellar interactions in dense clusters, including the well-known explosive event in Orion. His broader scientific interests also extend to cosmology and dark matter.