A Jupiter-mass object orbiting a brown dwarf could become the first confirmed moon beyond our Solar System. A massive object appears to be circling a brown dwarf in the CD-35 2722 system, but calling it a moon is not straightforward. Unlike moons in our Solar System, it does not orbit a planet. Instead, it travels [...]A giant planet spent more than a decade concealed inside one of astronomy’s most closely watched star systems. Astronomers have discovered a planet named Beta Pictoris d orbiting a young star just 63 light-years from Earth. The gas giant is about 100 times fainter than Beta Pictoris b, the first planet found in the system, [...]
Scientists working at the European Southern Observatory’s Very Large Telescope (ESO’s VLT) in Chile have detected evidence for an unusual, ‘moon-like object’ in the CD-35 2722 system that doesn’t appear to orbit a planet.
The research team behind the discovery said the unusual object, which orbits a brown dwarf that orbits a large, Sun-like star, doesn’t fit normal astronomical categories, leaving them unsure what to name it.
If confirmed, the unusual space object would be the first moon without a host planet ever discovered. Such a confirmation would also make the newly termed “exosatellite” the first exomoon of any type discovered outside our Solar System.
According to a statement announcing the moon-like object, ESO student Kevin Hoy had been monitoring the CD-35 2722 star system for months. The measurements that spotted the new, moon-like object were taken with the observatory’s CRIRES+ instrument using the radial velocity method that spotted the first planet around a Sun-like star.
During that time, the researcher and lead author of a study detailing the find said he noticed the system was “super weird” compared to our local Solar System. While the star at the center of the system, with a mass of about half of our Sun, was not unusual, they also determined that it is orbited by a brown dwarf. Brown dwarfs are astronomical objects too small to be a star, but too massive to be a planet, making the pairing unusual. Still, it was not unheard of.
However, according to Hoy, when the team spotted a third, smaller object in the system, they were left confused. Measurements indicated it is at least as massive as Jupiter, suggesting it may be a moon orbiting the Brown Dwarf, only without a host planet.
“The satellite we report is a giant gaseous body orbiting a highly massive companion, itself several times the mass of Jupiter,” explained Alice Zurlo, Director of the Millennium Nucleus of Young Exoplanets and their Moons (YEMS) in Chile project and collaborator on the study.
The team has temporarily named the moon-like object an “exosatellite.” However, Hoy said the object’s status as a ‘third wheel’ in the system makes them want to classify it as a moon, “even if it is nothing like the small, rocky moons we have in our system.”
“This system is somewhat hard to define using Solar-System-based words like ‘planet’ and ‘moon’,” the researcher explained. “The exosatellite is clearly massive enough to be a planet, but it does not orbit a star, though it orbits an object that orbits a star.”
Director Zurlo said the differences between the observed system and our own Solar System have added to the difficulty in labeling the moon-like object.
“We have a clear delineation between the planets and the Sun in the Solar System, so defining things like moons is simple,” Zurlo explained. “In the CD-35 2722 system, where we are blurring the lines between stars, planets, and moons, the whole thing becomes more complicated to describe.”
When discussing the significance of the moon-like object, Director Zurlo said detecting satellites in other systems will help researchers better understand the diversity in formation and evolution of planets, moons, and other moon-like objects. The director also noted the historical nature of the detection.
“As exotic as it is, this system is truly unique and represents a breakthrough: the first plausible detection of an exosatellite,” the researcher explained.
Moving forward, the team said the increased sensitivity of the 39-meter mirror on the ESO’s in-development Extremely Large Telescope (ELT) will allow for the detection of even smaller moons, including potentially spotting moons the size of Earth’s largest satellite. The researchers said such detections will likely force the astronomical community to reconsider how planetary objects are labeled, especially those in systems so radically different from our own.
The study “Planetary-mass exosatellite detected around the substellar companion of a star” was published in the journal Nature.
Christopher Plain is a Science Fiction and Fantasy novelist and has spent the last six years as Associate News Editor and Head Science Writer at The Debrief. Follow and connect with him on X, learn about his books at plainfiction.com, or email him at christopher@thedebrief.org.
A key component of the Orion Nebula had escaped detection by astronomers until now, according to a new study in Astronomy & Astrophysics.
An international team led by Juan Diego Soler at the University of Vienna used two of the world’s most advanced radio telescopes to map neutral atomic hydrogen gas across the nebula’s outer shell at unprecedented resolution. The new maps provide a clearer view of the celestial feature, and reveal a previously uncatalogued second bubble—a shell with much less mass than earlier estimates—and a four-light-year filament of gas extending from the structure.
Neutral hydrogen emits a faint radio signal at a wavelength of 21 centimeters, making it possible to trace otherwise invisible gas between the stars. Soler’s team solved this by combining data from the Karl G. Jansky Very Large Array in New Mexico and the FAST telescope in China. The VLA provided high resolution, while FAST picked up faint, widespread signals. Together, they produced the first detailed hydrogen map of the extended Orion Nebula, at the same scale as earlier ionized carbon maps.
Earlier calculations based on ionized carbon estimated that the front half of the shell was about 1,100 times the mass of our Sun. The hydrogen observations paint a different picture, suggesting the shell actually weighs in at closer to 100 solar masses. “Measuring mass is fundamental,” Soler said, “because it tells us about the efficiency of these newly formed stars shaping their environment with wind and radiation.”
A shell with only a tenth of the previously assumed mass significantly alters calculations of how efficiently newly formed stars shape their environment. The researchers note that molecular hydrogen, which is not detected in either the hydrogen or carbon data, may account for some of the missing mass.
The hydrogen maps also revealed an uneven distribution of gas, indicating a second, smaller cavity within the main shell. The team searched catalogs of known stars and young stellar objects in the region but found no candidate at the bubble’s center. The source responsible for creating the cavity may not be the type of object included in current catalogs.
Daniel Seifried at the University of Cologne, a co-author on the study, pointed to what that means for the models astronomers build to explain regions like this one. “These stunning observations serve as a reference for many modern astrophysical simulations investigating the evolution of gas and stars in the Milky Way. These are the kind of images that challenge the theoretical models and numerical simulations that we use to understand how massive stars affect their immediate surroundings.”
Previous models generally treated Orion’s shell as the product of a single expanding bubble. The discovery of a second cavity, with no obvious source at its center, instead suggests the nebula was shaped by multiple episodes of stellar feedback.
The new maps also uncovered a filament of hydrogen extending about four light-years from the shell’s western edge. Previous carbon-based observations saw only the base of this structure. The filament contains about 80 solar masses of hydrogen and does not appear to be associated with any known group of young stars. Its origin is unclear; it could be gas leaking through a weak spot in the shell or a leftover from the original cloud that existed before the bubble formed.
Claire Murray of the Space Telescope Science Institute, another co-author, framed the discovery within the broader push behind the observations. “This study is an exciting demonstration of the power of the latest-generation radio telescopes to uncover new pieces to the star formation puzzle.” Despite being one of the galaxy’s most extensively studied star-forming regions, the Orion Nebula continues to reveal discoveries.
This survey is the first scientific result from the NeAtHood project, which aims to map atomic hydrogen across nearby star-forming regions accessible to the VLA and FAST telescopes. Soler and his colleagues now plan to apply the same approach to additional targets. “Orion is only the beginning. Our newly developed methods show how future interferometers will reveal the hidden structure and dynamics of the interstellar medium—even in regions that astronomers already believed they understood well,” Soler explained.
If one of the sky’s best-studied star-forming regions still contains hidden structures, other nearby nebulae may prove equally surprising as the NeAtHood survey expands.
Austin Burgess is a writer and researcher with a background in sales, marketing, and data analytics. He holds an MBA, a Bachelor of Science in Business Administration, and a data analytics certification. His work focuses on breaking scientific developments, with an emphasis on emerging biology, cognitive neuroscience, and archaeological discoveries.
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