Astronomers discover possible exomoon in the star system CD-35 2722 at 73 light-years using the VLT in Chile

A team of astronomers has unveiled intriguing findings while observing the stellar system CD-35 2722, using the Very Large Telescope (VLT) in the Chilean desert. They have identified an object that challenges traditional notions of a moon, sparking debate in the scientific community about what constitutes a ‘moon’ in the cosmos.

This enigmatic object does not orbit a planet, as is typical in our Solar System, raising questions about its true classification. If confirmed as a moon, it would mark the first discovery of a natural satellite outside our solar neighborhood, at a distance of 73 light-years from Earth.

What is this new ‘exomoon‘?

Published in the prestigious journal Nature, the discovery details a system where the largest component is the star CD-35 2722. This stellar body, being half as massive as our Sun, has a brown dwarf around it. This brown dwarf, too large to be a planet but too small to be a star, is the object around which the new discovery orbits.

Defining this object has proven complicated. Some experts from the European Southern Observatory (ESO) have opted to call it an ‘exosatellite,’ a term indicating that this body is at least as massive as Jupiter. The brown dwarf it orbits has more than 30 times the mass of Jupiter, highlighting how peculiar this system is.

The distinction between planets, moons, and stars is clear in our Solar System, but in the CD-35 2722 system, categorization is complicated due to the blurring of mass and size boundaries. Alice Zurlo, a researcher on the team, emphasizes that the giant gaseous object challenges our traditional definitions of moons.

In astronomy, the category of satellite is defined by the object it orbits, not just by its mass. The discovered ‘exosatellite’ is comparable in mass to a planet, but its location in the system leads it to be considered a moon in this context.

Despite the discovery of more than 6000 exoplanets, exosatellites have been elusive. Although some candidates have been identified, the evidence has been insufficient to confirm them. This new finding represents a significant advancement in the search for satellites outside our solar system.

Previous research, such as those led by Quentin Kral, has found hints of satellites in systems like HD 206893, but without definitive conclusions. This discovery, however, could be the first credible detection of an exosatellite, according to expert Zurlo.

The definition of satellites encompasses objects that orbit other bodies and can be natural or artificial. Exosatellites, therefore, are satellites identified outside our solar system, although they lack a universally accepted definition.