#exomoon

Using the Atacama Large Millimetre/submillimeter Array (ALMA), in which the European Southern Observatory (ESO) is a partner, astronomers have unambiguously detected the presence of a disc around a planet outside our Solar System for the first time. The observations will shed new light on how moons and planets form in young stellar systems.

The disc in question, called a circumplanetary disc, surrounds the exoplanet PDS 70c, one of two giant, Jupiter-like planets orbiting a star nearly 400 light-years away. Astronomers had found hints of a “moon-forming” disc around this exoplanet before but, since they could not clearly tell the disc apart from its surrounding environment, they could not confirm its detection — until now.

In addition, with the help of ALMA, Benisty and her team found that the disc has about the same diameter as the distance from our Sun to the Earth and enough mass to form up to three satellites the size of the Moon.

But the results are not only key to finding out how moons arise. “These new observations are also extremely important to prove theories of planet formation that could not be tested until now,” says Jaehan Bae, a researcher from the Earth and Planets Laboratory of the Carnegie Institution for Science, USA, and author on the study.

First Proto Exomoon Detected

A team of astronomers have taken the first glimpse at a possible proto moon orbiting a large gas giant planet in another star system over 400 light years from us.

The ring of material surrounding the planet contains enough mass to construct 3 moon sized satellites.

While our own system is awash with moons, this is the first solid evidence of moon formation outside of our star system and in a young system, giving hints to how some moons may be created in the first instance.

It's a fantastic bit of research and hopefully will open up many more findings, as well as improvements in finding smaller rocky type worlds.

Meet the ploonets. These are planets that used to be moons.

There are none of these planets in our solar system. But they might exist in other star systems. There, some moons might escape their parent planets’ gravity and start orbiting their parent stars instead. That’s according to new computer simulations. Scientists have dubbed the liberated worlds “ploonets.” And, the scientists say, current telescopes may be able to find the wayward objects.

The scientists’ thinking starts with these facts. There are planets that orbit other stars out in space. And those planets could have moons. Those moons are called exomoons. Exomoons should be common. But efforts to find them have turned up empty so far.

One person who wants to know more about these moons is Mario Sucerquia. He is an astrophysicist at the University of Antioquia in Medellín, Colombia. He and his colleagues used computer models to simulate what would happen to moons in other star systems. The team was particularly interested in moons that orbited hot Jupiters. These are giant gas planets that lie scorchingly close to their stars. They orbit their stars within days — sometimes just a few days make up their year.

Scientists Say: Exomoon

Many astronomers think that hot Jupiters weren’t born so close to their stars, though. Instead, the planets moved toward their star from a more distant orbit. That movement messes with any moon the planet might have. What happens is the gravity — the tug between the planet and star — adds energy to the moon’s orbit. The moon then is pushed farther and farther from its planet. Eventually, it escapes its planet’s gravity.

Ask Ethan: Can We Find Exoplanets With Exomoons Like Ours?

“But, by far, the best possibility we have today is through direct measurement of a transiting exomoon. If the planet that's orbiting the star can make a viable transiting signal, then all it will take is the same serendipitous alignment to have its moon transit the star, and sufficiently good data to tease that signal out of the noise.

This is not a pipe dream, but something that has already occurred once. Based on data taken by NASA's Kepler mission, the stellar system Kepler-1625 is of particular interest, with a transiting light curve that not only displayed the definitive evidence of a massive planet orbiting it, but of a planet that wasn't transiting with the exact same frequency you'd expect orbit after orbit.”

If you want to find an exoplanet, the most successful methods are to look for the effect it has on the light from it’s parent star. But what about if you wanted to find an exomoon? There are some subtle effects at play, but if we think hard about what they might be, we can come up with a series of methods that could reveal an exomoon’s presence indirectly, and pinpoint exactly where and when we could look to try and detect one directly. Thought to be a great technique for the upcoming James Webb Space Telescope to take advantage of TESS data, we’ve actually succeeded once already, using the Hubble/Kepler combo!