Chapter 1: The PDS 70 Star System

Astronomers have made a remarkable discovery within the PDS 70 star system, confirming the existence of at least one moon orbiting an exoplanet—marking the first time an exomoon has been definitively identified in another solar system.

Utilizing the Atacama Large Millimeter/submillimeter Array (ALMA), researchers reported the detection of disks composed of dust and gas around an exoplanet for the first time. This breakthrough offers compelling evidence of moon formation around a planet within an alien star system.

Located nearly 400 light years from Earth, the PDS 70 system hosts at least two massive Jupiter-like planets. Initial studies of one of these exoplanets, known as PDS 70c, indicated the presence of a moon-forming disk. However, distinguishing this disk from surrounding material had previously hindered definitive confirmation—until now.

“Our research reveals a clear detection of a disk where satellites may be forming. The resolution of our ALMA observations was so refined that we could definitively associate the disk with the planet and accurately constrain its size for the first time,” states Myriam Benisty, a researcher affiliated with both the University of Grenoble in France and the University of Chile.

Join us on Astronomy News with The Cosmic Companion on August 10, when we will speak with Dr. Richard Teague from Harvard University about this historic finding.

The first video, titled "PDS 70: the key to understanding our origins?" explores the implications of this discovery for our understanding of planetary formation.

Chapter 2: The Formation of Exomoons

So far, astronomers have identified over 4,400 planets orbiting stars beyond our solar system. However, this is the first recorded instance of an exomoon orbiting a planet in a foreign star system.

In developing solar systems, planets gradually accumulate material from a surrounding disk of dust, gas, and debris. As these young exoplanets grow within their circumstellar disks, they can consume this material, forming a ring with minimal matter. Moons can subsequently emerge from the accumulated rocks and dust, establishing a circumplanetary disk around the forming worlds.

“Despite having found over 4000 exoplanets to date, all were discovered in mature systems. PDS 70b and PDS 70c, which resemble the Jupiter-Saturn pair, are the only two exoplanets detected so far that are still in their formative stages,” explains Miriam Keppler, a researcher at the Max Planck Institute for Astronomy in Germany.

The disk surrounding PDS 70b is approximately 500 times larger than the rings of Saturn. Researchers noted, “These two planets create a substantial cavity within the disk, as evidenced by a noticeable gap in dust and a depletion of (12)CO gas emissions along PDS 70b’s orbit.”

While a moon is forming around PDS 70c, no similar structure has been observed around PDS 70b, suggesting that PDS 70b may have been deprived of dusty materials by its planetary neighbor.

Nevertheless, astronomers remain uncertain about the specifics of exomoon formation. The European Southern Observatory’s Extremely Large Telescope (ELT), currently under construction in Chile, could potentially help unravel the mysteries surrounding this young exomoon and others throughout the galaxy.

The second video, "Artist's animation of the PDS70 system," offers a visual representation of the dynamics within this unique star system.

James Maynard, the founder and publisher of The Cosmic Companion, resides in Tucson with his wife, Nicole, and their cat, Max.

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