We started finding a lot of 'hot Jupiters' in the early days of planet hunting simply because, although their existence was not widely predicted, they were the most likely planetary types to trigger our radial velocity detection methods. These star-hugging worlds produced a Doppler signal that readily showed the effects of planet on star, while smaller worlds, and planets farther out in their orbits, remained undetected. David Kipping (Columbia University) uses hot Jupiters as an analogy when describing his own indefatigable work hunting exomoons. We already have one of these - Kepler-1625 b-i - but it remains problematic and unconfirmed. If this turned out to be the first in a string of exomoons, we might well expect all the early finds to be large moons simply because using transit methods, these would be the easiest to detect. Kepler-1625 b-i is problematic because the data could be showing the effects of other planets in its system. If real, it would be a moon far larger than any...

Using machine learning to provide an algorithmic approach to the abundant data generated by the Transiting Exoplanet Survey Satellite (TESS) has proven unusually productive. I'm looking at an odd object called TIC 400799224, as described in a new paper in The Astronomical Journal from Brian Powell (NASA GSFC) and team, a source that displays a sudden drop in brightness - 25% in a matter of four hours - followed by a series of brightness variations. What's going on here? We're looking at something that will have to be added to a small catalog of orbiting objects that emit dust; seven of these are presented in the paper, including this latest one. The first to turn up was KIC 12557548, whose discovery paper in 2012 argued that the object was a disintegrating planet emitting a dust cloud, a model that was improved in subsequent analyses. K2-22b, discovered in 2015, showed similar features, with varying transit depths and shapes, although no signs of gas absorption.. In fact, the objects...

As we begin the New Year, I want to be sure to catch up with the recent announcement of a discovery regarding 'rogue' planets, those interesting worlds that orbit no central star but wander through interstellar space alone (or, conceivably, with moons). Conceivably ejected from their host stars through gravitational interactions (more on this in a moment), such planets become interstellar targets in their own right, as given the numbers now being suggested, there may be rogue planets near the Solar System. Image: Rogue planets are elusive cosmic objects that have masses comparable to those of the planets in our Solar System but do not orbit a star, instead roaming freely on their own. Not many were known until now, but a team of astronomers, using data from several European Southern Observatory (ESO) telescopes and other facilities, have just discovered at least 70 new rogue planets in our galaxy. This is the largest group of rogue planets ever discovered, an important step towards...