New Study Reveals Turbulent, Unpredictable Early Lives of Young Stars

Lead author Neha Sharma emphasized the study’s significance, noting that “by studying their flickers, we can uncover how stars grow, feed, and shed their dusty wombs.”

A groundbreaking decade-long astronomical survey has unveiled the extraordinary turbulence that marks the birth and early evolution of stars. The comprehensive study, using data from NASA’s Wide-field Infrared Survey Explorer (WISE) and its extended mission NEOWISE, has produced one of the most detailed and expansive catalogs of mid-infrared variability in Young Stellar Objects (YSOs) ever compiled.

The research, published in The Astrophysical Journal Supplement Series, was led by Neha Sharma and Saurabh Sharma from the Aryabhatta Research Institute of Observational Sciences (ARIES)—an autonomous institute under the Department of Science & Technology (DST), Government of India. Their catalog spans the light curves of over 22,000 YSOs spread across major star-forming regions of the Milky Way.

This remarkable dataset provides unprecedented insight into how stars form, evolve, and undergo violent fluctuations long before they reach the stable, hydrogen-burning phase known as the main sequence.

---

The Turbulent Birth of Stars: From Collapsing Clouds to Protostars

Young Stellar Objects represent the earliest observable phases in a star’s lifecycle. Long before stars like our Sun shine steadily by fusing hydrogen, they exist as dense pockets of gas and dust embedded deep within giant molecular clouds—cold, massive structures that serve as stellar nurseries across the galaxy.

These clouds can collapse due to numerous triggers:

• Shockwaves from supernova explosions

• Intense radiation from nearby massive stars

• Turbulence within the interstellar medium

• Dense clumps collapsing under their own gravity

As collapse begins, material at the center forms a protostar, surrounded by a rotating disk of gas and dust. Unlike mature stars, protostars shine not due to nuclear fusion but due to the heat generated from gravitational contraction and accretion.

Accretion—the process by which material from the disk falls onto the forming star—is wildly unstable. Sudden surges in material or temporary declines can dramatically change a protostar’s brightness. When the developing star emits enough radiation pressure, it eventually blows away the remaining cloud material, ending the accretion phase and leaving behind a young, pre-main-sequence star.

These energetic and rapidly shifting stages are what make YSOs prime candidates for long-term infrared monitoring.

---

Infrared Observations Reveal Hidden Stellar Drama

The advantage of infrared astronomy lies in its ability to penetrate thick dust clouds that obscure optical observations. WISE and NEOWISE, observing at 3.4 and 4.6 microns, were ideally suited for monitoring YSOs shrouded in heavy dust.

Over ten years, the ARIES researchers meticulously analyzed the brightness variations of thousands of YSOs, categorizing their behaviors into six major variability types:

• Linear – consistent brightening or fading

• Curved – nonlinear rising or falling trends

• Periodic – repeating patterns tied to rotation or disk movement

• Burst – sudden, dramatic brightening events

• Drop – abrupt declines in brightness

• Irregular – chaotic, unpredictable fluctuations

Approximately 26% of all YSOs in the sample exhibited measurable variability. The most common behavior was irregular variability, reflecting the chaotic, unstable nature of early stellar development.

---

Younger Stars Are More Unstable—And More Revealing

The study found that Class I YSOs, among the youngest and still heavily embedded in thick dust, were particularly variable: 36% showed intensity changes, compared to 22% in more evolved Class III YSOs, which have mostly lost their disks.

Color changes offered further clues into the physical processes at play:

• Most stars reddened when they brightened, suggesting heating of surrounding dust or increased extinction.

• A notable minority became bluer as they brightened, a signature linked to rapid accretion events or clearing of inner disk material.

This blueing trend was significantly more common in the youngest objects—highlighting that the earliest phases of stellar development are marked by extreme, sporadic energy bursts.

---

A Treasure Trove for Future Astronomers

The publicly accessible catalog includes over 5,800 variable YSOs, providing an invaluable observational foundation for studying:

• Accretion physics

• Disk evolution

• Episodic outbursts

• Early stellar structure

• Protostellar environment dynamics

Lead author Neha Sharma emphasized the study’s significance, noting that “by studying their flickers, we can uncover how stars grow, feed, and shed their dusty wombs.”

The research also arrives at an opportune time. With advanced facilities like the James Webb Space Telescope (JWST) and India’s 3.6m Devasthal Optical Telescope (DOT) gearing up for deeper explorations, astronomers expect to probe these processes with greater detail than ever before. JWST, with its unparalleled infrared sensitivity, is poised to reveal the fine structure of accretion mechanisms, dust heating, and disk instabilities.

---

Illuminating the Origins of Sun-like Stars

By piecing together these intricate, long-term brightness patterns, scientists inch closer to understanding how stars like our Sun emerged billions of years ago from dark, chaotic clouds.

This sweeping survey not only advances our knowledge of early stellar evolution but also charts a path for future discoveries—ensuring that the mysteries of stellar birth will be unraveled with increasing clarity in the years to come.