Unprecedented Star Cluster Study May Offer View of Planet Formation and
Our Solar System's Own Early Beginnings
unprecedented 14-year study by Wesleyan University researchers has revealed
a phenomenon that may indicate the forming of new planets or perhaps even
the existence of young planets orbiting young sun-like stars more than 1,600
light years away.
The observations were presented at the American Astronomical Society (AAS)
meeting in Washington, DC. on January 11 by William Herbst, the John Monroe
Van Vleck Professor of Astronomy and chair the astronomy department
(pictured at right), Gabriel Roxby ‘06, a Wesleyan undergraduate involved in
the study, and Eric Williams, the systems manager of the Van Vleck
The Wesleyan team analyzed 500 stars in the Orion Nebula Cluster (ONC) which
is approximately 500 pc or 1600 light years from earth. The data from the
stars were collected by faculty and graduate and undergraduate students
during a continuous 14-year period. The observations gave the astronomers
the unique opportunity to track the long-term behavior of these stars
concurrently with their subtle changes over short timescales.
The findings presented at the AAS meeting detail the discovery of a large
number of young T Tauri stars with intriguing patterns in brightness
variation over both short and long timescales. One star discovered,
Trapezium 093/JW#669, became of particular interest because it seemed to
grow brighter then fainter in a remarkably steady pattern with a possible
period of about 10 years. This is an extremely long cycle, given that it
rotates every 1.18 days.
One theory suggests the presence of a disk of dust and rock orbiting the
star. Such a circumstellar disk would have to contain a large clump, such as
a planet or proto-planet, in order to obscure the light of the star at
certain times and not others. Another possible explanation for the
brightness fluctuations may be that the star is experiencing magnetic cycles
akin to those seen in our Sun, where its magnetic field becomes stronger and
weaker over time, causing the total area covered by sunspots to grow and
shrink. Another theory is that the phenomenon is being caused by the
presence of a young fully-formed gas-giant planet akin to Jupiter.
Whatever the cause, the observations by the Wesleyan researchers may offer
significant insights into our own solar system’s origins. Trapezium 093/JW#669
bears a strong resemblance to a younger version of the Sun, and it may be
undergoing processes similar to those in the Sun’s early history. Further
investigation may reveal whether these or other explanations can account for
this star’s long and regular period.
This active star-forming region is a promising area for observations because
of its relative nearby distance and its large population of T Tauri stars,
which are typically young (about 1 million years old).
The study also offers a new perspective on the changes that occur in T Tauri
stars over many years. For the first time a large collection of long-term
light curves for a vast sample of young variable stars has been gathered.
The sample can be used to further analyze general trends among these stars,
as well as locate other unique stars that may help to shed light on the
genesis of our own Solar System.
The data were obtained using Wesleyan’s 0.6 meter (24 inch) Perkin
telescope. Researchers used differential photometry to calculate stars’
alterations in brightness from night to night by comparing the variable
stars to a few stars in each field known to have relatively unchanging
brightness. They used these calculations to plot “light curves,” or diagrams
of the change in brightness over time, for each star.
Wesleyan astronomers will continue their study of the star cluster and
generate data for further analysis.
|By Clara Moskowitz ’06 and David
Pesci, director of Media Relations