 |
| Illustration of a moon outside our solar system /photo/javardh/Unsplash. |
A team of scientists using the European Southern Observatory’s Very Large Telescope (ESO’s VLT) in Chile have discovered astronomy’s first known exosatellite, or exomoon, orbiting an unusual body in the solar system known as CD-35 2772, just 71 light years away—next door by astronomical standards. The moon is huge—at least as massive as Jupiter, which is itself the largest planet in our solar system with a diameter 11 times that of Earth. And the planet that exosatellite orbits isn’t a planet at all.
Rather it’s a brown dwarf, a gassy object far too big to be a conventional planet—in this case 33 times the mass of Jupiter—but too small to ignite its nuclear furnace and become a star.
Exoplanets typically aren’t spotted visually, since the pinpoint light of the distant world is swamped by the glare of the nearby star—a little like a moth fluttering invisibly next to a street light. Rather they are discovered in one of two indirect ways. The first is known as the transit method. When an orbiting planet passes in front of its parent star, it blocks a bit of the star’s light. The dimming is exceedingly tiny—the equivalent of removing one light bulb from a board containing 10,000 of them—but it’s enough for a sensitive telescope to detect.
The greater the dimming the greater the diameter of the planet. The second means of detecting an exoplanet is known as the radial velocity method: looking for the tiny wobble the moving planet’s gravity causes in the star. The greater the wobble, the greater the planet’s mass. The recent discovery is about a unique celestial object in the CD-352722 star system that could be the first moon found outside our solar system. What makes it super-weird is its inability to orbit a planet. Instead it circles a brown dwarf that orbits a star, While massive enough to be considered a planet, its specific orbital path makes researchers inclined toward calling it a moon, despite not resembling the small, rocky moons in our solar system.
The team has decided to call it an “exosatellite” because it blurs the lines between planets, stars and moons.
The discovery is reported in a new paper titled Planetary-Mass Exosatellite Detected Around a Star’s Substellar Companion, published in the journal Nature.
“We have a clear delineation between the planets and the Sun in the Solar System, so defining things like moons is simple,” said Alice Zurlo, the lead author of a new study
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.”
For years, astronomers have been making efforts to find exomoons, but it has remained in vain. Although they discovered more than 6,000 exoplanets, none of them has been fully confirmed to exist.The discovery helps scientists understand the commonality of such objects, their formation, origin, and nature. Also the discovery is essentially for understanding more dwarf planets that may help our lives and innovation beyond our solar system.