Probing the birth of stars—observing the chaotic, dynamic light of pre–main sequence stars (YSOs) to understand stellar formation and early evolution.
To begin with, it is known that many stars listed in the GCVS of type I are seriously underobserved. One aim of the section will be to remedy that situation! Those stars listed as “IS” are an especially heterogeneous group of stars, some of which may well turn out to be non-YSO’s—perhaps Algol or RR Lyrae stars. However, nobody is going to know until the type of variability can be confirmed, so there is clearly a fruitful field here for original observation.
What We Do
Young Stellar Objects (YSOs), also known as pre–main sequence stars (PMS), represent stars in their formative stages. These objects, including T Tauri stars, UXors, and other variable young stars, are key to understanding the processes of star and planet formation. In the YSO Section, we aim to increase coverage of under-observed YSOs—many young stars catalogued in variable-star databases have poorly understood variability types, and amateur observers can make critical contributions. Our network of observers collaborates with professional astronomers and participates in multi-wavelength and multi-technique campaigns. Because YSOs often reside in crowded star fields, we provide specially tailored comparison-star charts (using AAVSO’s VSP and Aladin) to make observations accessible even in dense Milky Way regions.
YSOs exhibit a wide variety of variability: some stars (e.g., RR or CQ Tauri types) show large, unpredictable brightness changes; others vary due to rotational modulation from star spots or accretion processes. Multi-wavelength photometry is particularly powerful in YSO work, because these young stars often show quite different behavior in different filters. Though many YSOs are faint, quite a few are within reach of small telescopes, and some brighter ones can even be observed with binoculars.
How We Do It
Observers in the YSO Section use visual estimates, CCD photometry, and other techniques depending on the target. For large-amplitude, unpredictable YSOs, visual observing can be very effective. For smaller-amplitude or more subtle variations, CCD (or CMOS) photometry through standard filters is often used. We encourage multi-filter observations (multi-wavelength) because YSOs often show significantly different behavior in different spectral bands. Targets of interest are often highlighted in the YSO newsletter, but observers can select their own targets via the AAVSO Target Tool, which allows filtering by brightness, variability type, and constellation. Once observations are collected, they are submitted to the AAVSO International Database, contributing to long-term monitoring and scientific research. We also foster collaboration via the AAVSO YSO Forum, where observers, researchers, and professionals coordinate observing campaigns, share light curves, and discuss the physical interpretation of variability.
Is It Right for Me?
Level: Moderate. YSO observing can be well-suited for visual observers for large-variation stars, but for more subtle changes, CCD photometry is preferred.
Equipment: A variety of setups work: small telescopes (even binoculars) can detect many YSOs; for precision work, a CCD/CMOS camera and photometric filters are very helpful.
Observing Requirements: Because YSOs can vary on multiple timescales and in unpredictable ways, regular monitoring is valuable. A cadence that covers days, weeks, or months may be needed depending on the star and its behavior.
Additional Considerations: Accurate comparison-star selection (especially in crowded fields) is essential. Observers should be prepared to handle multi-band photometry. Long-term commitment is especially valuable for building scientifically useful time series. Participation in campaigns (professional–amateur cooperation) is common, and observers are encouraged to contribute to the YSO Bulletin and community discussions.