Free Astronomy Magazine July-August 2026

14 JULY-AUGUST 2026 ASTRO PUBLISHING signs of light being absorbed by carbon dioxide (CO 2 ) and carbon monoxide (CO), which allowed them to determine the amount of those heavier chemical elements, which as- tronomers collectively call metals. They found strong evidence that 29 Cygni b is enriched in metals relative to its host star, which is similar to our Sun in its composition. Given the planet’s mass, the amount of heavy elements it contains is equivalent to about 150 Earths. This suggests that it accreted large amounts of metal- enriched solids from a protoplane- tary disk. The team also used a ground-based optical telescope array called CHARA (Center for High Angular Resolution Astronomy) to determine if the planet’s orbit is aligned with the spin of the star. They confirmed that alignment, which would be ex- pected for an object that formed from a protoplanetary disk. “We were able to update the planet’s orbit, and also observed the host star to determine its orienta- tion with respect to that orbit,” said Ash Messier, co-author and a gradu- ate student at Johns Hopkins Univer- sity. “We showed that the incli- nation of the planet is well-aligned with the spin axis of the star, which is similar to what we see for the planets of our solar system.” “Put together, this evidence strong- ly suggests that 29 Cygni b formed within a protoplanetary disk through rapid accretion of metal- rich material, rather than through gas fragmentation,” said Balmer. “In other words, it formed like a planet and not like a star.” As the team gathers data on the other three targets within their pro- gram, they plan to look for evidence of compositional differences be- tween the lower-mass and higher- mass planets. This should provide additional insights into their forma- tion mechanisms. A stronomers used NASA’s James Webb Space Telescope to directly image 29 Cygni b, which weighs 15 times Jupiter. They found evidence for heavy chemical elements like carbon and oxygen, which strongly suggests it formed like a planet by accretion within a protoplanetary disk, and not like a star through fragmentation. Webb’s NIRCam (Near-Infrared Camera) was used in its coronagraphic mode, in which a wedge (indicated by the blue box) is used to block the light of the host star (labeled A and marked with a star symbol) to re- veal the planet. This image combines light from three filters between 4 and 5 microns. The planet is brightest in the blue filter, then green, then red, so it ap- pears as an off-white dot in the color composite. If carbon dioxide weren’t pres- ent, the planet would appear noticeably redder. In this image, the color blue is assigned to 4.1 micron light, green to 4.3 micron light, and red to 4.6 micron light. [NASA, ESA, CSA, William Balmer (JHU, STScI), Laurent Pueyo (STScI); Image Processing: Alyssa Pagan (STScI)] away to much higher masses than 29 Cygni b. This is the lowest mass you could plausibly get. But at the same time, it’s about the highest mass you could get from accretion,” said lead author William Balmer of the Johns Hopkins University and the Space Telescope Science Institute, both in Baltimore. Balmer’s observing program used Webb’s NIRCam (Near-Infrared Cam- era) in its coronagraphic mode to di- rectly image 29 Cygni b. This planet was the first of four objects target- ed by the program, all of which are known to weigh between 1 and 15 times as much as Jupiter. The team also required their targets to orbit within about 9 billion miles (15 bil- lion kilometers) of their stars. The planets were all young and still hot from their formation, ranging in temperature from about 1,000 to 1,900 degrees Fahrenheit (530 to 1,000 degrees Celsius). This would ensure their atmospheric chemistry was similar to the planets of HR 8799, whose system Balmer studied previously. By choosing appropriate filters, the team was able to look for !