Free Astronomy Magazine November-December 2025

45 ASTRO PUBLISHING ancient debris disk of uneven brightness. The disk is closer to the star in the south, where the disk is wider and fainter, and further from the star in the north, where the disk is narrower and brighter. The dotted ring shows the possible orbit of a planet implied by Lovell et al. As- tronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) have made the highest res- olution image to date, revealing new insights into the unusual and c e n - t r i c—i t s eccentricity changes with distance from the star. Unlike previous models assuming a uniform or “fixed” eccentricity, their new data-driven model shows that the disk’s shape grows less stretched (or less eccentric) the farther a seg- ment is from Fomalhaut. This mor- phology is known as a negative eccentricity gradient. You can imag- ine the offsets between the star and the ring’s center, much like Saturn’s rings, if Saturn wasn’t sitting neatly in the middle. “Our observations show, for the first time, that the disk’s eccentricity isn’t constant,” said lead author of one of the papers, Joshua Bennett Lovell, a Submillimeter Array Fel- low with the Harvard-Smithsonian Center for Astrophysics. “It steadily drops off with distance, a finding that has never before been conclu- sively demonstrated in any debris disk.” Lovell is also an ALMA Ambas- sador with the U.S. National Science Foundation National Radio Astron- omy Observatory’s North American ALMA Science Center. Using high- NOVEMBER-DECEMBER 2025 mys- t e r i o u s architecture of the debris disk encircling Fomalhaut, one of the brightest and most well-studied stars in our cosmic neighborhood. Debris disks are vast belts of dust and rocky bodies, simi- lar to our Solar System’s asteroid belt—but much larger. The lopsidedness (or eccentricity) of Fomalhaut’s disk has fascinated as- tronomers for nearly two decades. An international research team, led by astronomers at the Center for As- trophysics | Harvard & Smithsonian and Johns Hopkins University, pub- lished two papers analyzing these new observations in The Astrophysi- cal Journal/The Astrophysical Jour- nal Letters . They have now found that Fomalhaut’s disk is not just ec-