Physical Address
304 North Cardinal St.
Dorchester Center, MA 02124
Humans discovered the first exoplanet in 1992, and since then they have found nearly 6,000 other planets outside our solar system. However, these researchers have never once found a moon orbiting any of those planets. That may have changed with the recent discovery of the first moon-like object in another solar system.
The results were published in Recent study. This potential moon, known as CD-35 2722 B, orbits a brown dwarf rather than a traditional planet, says Kevin Hoy, lead author of the study and a doctoral student at the Institute for Astronomical Studies. It is also about 90% the size of Jupiter and larger than Saturn. This moon-like body takes 170 days to completely orbit its host.
Howie and other researchers used a rather old trick to discover this moon: radial velocity analysis, which is used to detect wobbles in stars that are an indicator of the presence of a nearby exoplanet. Planets become fainter as they move away from their host star, and exoplanets are found by displaying changes in spectral shift.
This is the same method that scientists used for detection The first planet outside the solar systemIt was used to detect this exoplanet, which is the name given to objects that have not yet been identified as an exoplanet or exomoon.
“This is the first time, to our knowledge, that this technique has produced evidence of satellites around a companion brown dwarf,” Hui said in the study.
Most people understand that the moon is an object orbiting another body that is not a star, such as Earth’s moon or various other moons in the solar system.
NASA
Schrödinger’s moon?
The study results are not without controversy. Arguably the biggest question is whether this is actually a moon. Brown dwarfs, often referred to as failed stars, are much larger than standard planets but do not have the chemical reactions at their core necessary to become a star. The outer satellite orbits this brown dwarf It is also larger It is larger than all but one planet in our solar system, and larger than most exoplanets that researchers have discovered so far.
Complicating matters is the fact that this is the case Nobody actually knows What is the moon? There is no unified definition from the International Astronomical Union, which is the body that usually comes up with such definitions. Most people understand that the Moon is a physical object that orbits a larger body, just as our Moon orbits the Earth.
There are some rules for this. The host body cannot be a star, because the body it orbits would be a planet. It also cannot be made by humans, or considered a satellite. The definition has expanded as astronomers find more and more unique ones Types of satellites. One example is Zoozve, a quasi-moon that may look like the Moon from the surface of Venus but is actually an asteroid orbiting the Sun that is close enough to look like the Moon.
As for the CD-35 2722 B, Howie told me there was one problem The special nature of brown dwarfs. Brown dwarfs are considered substellar objects because they are too large and dense to be considered a planet but lack the hydrogen fusion needed to be a star. They’re somewhere in between the two, so it’s unclear whether an object orbiting a brown dwarf could be considered a planet or a moon.
This is not the only obstacle. “The object itself is at least as massive as Jupiter, and is much larger than the rocky and icy moons in the solar system,” Hoy said. “It’s not clear that anything this large should be considered a moon.”
Currently accepted IAU definitions group brown dwarfs with stars, such that an object orbiting a brown dwarf of sufficient size is considered a planet, Hoy says. However, this brown dwarf orbits its host star like a planet, and CD-35 2722 B orbits the brown dwarf like a moon; Thus, it achieves the behavior of the moon and the definition of the planet.
“Maybe when a definition for exomoons is written, such objects will fit the definitions of planet and moon, but we have to see,” Hui said. “These terms are mutually exclusive in the solar system, so I wouldn’t be surprised if they wrote the definition in a way that preserves that.”
Until that day comes, no one is quite sure what to make of CD-35 2722 B, and until the International Astronomical Union opens the metaphorical box and comes up with an official definition of what a moon means, CD-35 2722 B can realistically be considered both a moon and a planet.
