Indian astronomers have compiled one of the largest catalogues ofyoung stellar objects (YSOs)using data fromNASA’s WISEandNEOWISE missions. A young stellar object (YSO) is aforming starsurrounded by rotating disks of gas and dust. It becomes a mature star once it reaches the main sequence and beginsstable hydrogen fusion.
Key Findings:
- Heat Source:Protostarsgenerate heat throughgravitational collapse(contraction due to own gravity) andmass accretion, unlikemature starsthat emit energy vianuclear fusion.
- Episodic Accretion:The protostar’sbrightness fluctuatesas disk material intermittently falls onto the star, with intense bursts followed by quieter lulls.
- Six Types:The study classified YSO brightness variability intosix behavioural categories.
- Patterns:Linear (steady change), Curved (nonlinear), Periodic (repeating cycles), Burst (sudden brightening), Drop (abrupt dimming), and Irregular (chaotic).
- Variability Share:About 26% of observed YSOs showed detectable brightness fluctuations, with ‘irregular’variability(violent and unpredictable) being themost common.
- Age Link:The study found a clear correlation betweenstellar ageandstability, with 36% of Class I YSOs (the earliest stage) showing variability compared to 22% Class III YSOs.
Colour Variability:Whilemost YSOsbecame ‘redder’ as they brightened, some of theyoungest starsappeared ‘bluer’ because ofincreased accretionepisodes
IAS-2026 - OPTIONAL / GEOGRAPHY / PUBLIC ADMINISTRATION / SOCIOLOGY / ANTHROPOLOGY / ORIENTATION ON 03 & 04-10-2025 
