ALMA Uncover Surprising New Methods Planets May Form 

17 January, 2025 / Read time: 4 minutes

Tucked away in a star-forming region in the Taurus constellation, a pair of circling stars display some unexpected differences in the circumstellar disks of dust and gas surrounding them. A new study led by researchers at Lowell Observatory, combining data from the Atacama Large Millimeter/submillimeter Array (ALMA) and Keck Observatory, has unveiled intriguing findings about planet formation in this binary star system, known as DF Tau, along with other systems in this region.  

DF Tau consists of two young stars with nearly equal masses, orbiting each other every 48 years. Since both stars likely formed together, with the same composition in the same environment, astronomers would expect them to share different things in common, like having similar circumstellar disks. But this is not the case—while the brighter primary star has an active inner disk, the secondary star's inner disk appears to have almost completely disappeared. These unexpected differences challenge current theories of disk evolution and planet formation. 

Like a potter's wheel shapes clay into various forms, a circumstellar disk provides the materials and environment for planets to form. Over time, the dust and gas in the disk will clump together, eventually forming planets, moons, and other celestial bodies. The disks won't last forever — as a star matures and planets form, the disk gradually disappears. So, what caused the unusual dissipation observed in the circumstellar disk of the secondary star? 

High-resolution ALMA imaging, combined with optical and infrared data from other telescopes, allowed researchers to study, analyze, and compare the stars' properties and disks. This binary has a relatively small, tight orbit, which means gravity truncates the outer parts of the disk, but it is unlikely that the current binary orbit could alter the inner disk. Instead, other processes may be at work.  

"The dispersal of circumstellar disks is a complicated process with many unknowns. By looking at systems that form together, we can control one major variable: time. DF Tau and other systems in our survey tell us that disk evolution isn't strictly a function of time; other processes are at play," shares Taylor Kutra of Lowell Observatory, lead author of this research.  

Binary systems like DF Tau and other sources in this ALMA survey offer a natural laboratory to study how circumstellar disks evolve. Understanding these processes is essential for refining models of planet formation because disk evolution sets the timescale on which planet formation occurs. This research highlights the diversity of disk behaviors and underscores the need for further studies to unravel the factors influencing their lifespans and structures. These findings deepen our understanding of binary star systems and shed light on the broader mechanisms shaping planetary systems across the galaxy.

Additional Information

The results of the observation are published in the following scientific article:

Kutra et.al "Sites of Planet Formation in Binary Systems. II. Double the Disks in DF Tau".

The original press release was published by the National Radio Astronomical Observatory (NRAO) of the United States, an ALMA partner on behalf of North America.

The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of the European Organization for Astronomical Research in the Southern Hemisphere (ESO), the U.S. National Science Foundation (NSF) and the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Republic of Chile. ALMA is funded by ESO on behalf of its Member States, by NSF in cooperation with the National Research Council of Canada (NRC) and the National Science and Technology Council (NSTC) in Taiwan, and by NINS in cooperation with the Academia Sinica (AS) in Taiwan and the Korea Astronomy and Space Science Institute (KASI).  

ALMA construction and operations are led by ESO on behalf of its Member States; by the National Radio Astronomy Observatory (NRAO), managed by Associated Universities, Inc. (AUI), on behalf of North America; and by the National Astronomical Observatory of Japan (NAOJ) on behalf of East Asia. The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning, and operation of ALMA. 

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