https://phys.org/news/2019-07-nasa-tess-mission-link-planets.html NASA's newest planet-hunting satellite has discovered a type of planet missing from our own solar system. Launched in 2018, the Transiting Exoplanet Survey Satellite, or TESS, has found three new worlds around a neighboring star. Stephen Kane, a UC Riverside associate professor of planetary astrophysics, says the new star system, called TESS Object of Interest, or TOI-270, is exactly what the satellite was designed to find. A paper describing TOI-270 has been published in the journal Nature Astronomy and is now available online. Of the three new exoplanets, meaning they're outside our solar system, one is rocky and slightly larger than Earth, while the two others are gaseous and roughly twice Earth's size. Not only is the smaller planet in the habitable zone—the range of distances from a star that are warm enough to allow liquid-water oceans on a planet—but the TOI-270 star is nearby, making it brighter for viewing. It's also "quiet," meaning it has few flares and allows scientists to observe it and its orbiting planets more easily. "We've found very few planets like this in the habitable zone, and many fewer around a quiet star, so this is rare," said Kane. "We don't have a planet quite like this in our solar system." In our own solar system, there are either small, rocky planets like Earth, Mercury, Venus, and Mars, or much larger planets like Saturn, Jupiter, Uranus, and Neptune that are dominated by gasses rather than land. We don't have planets about half the size of Neptune, though these are common around other stars. more at link...... the paper: https://www.nature.com/articles/s41550-019-0845-5 A super-Earth and two sub-Neptunes transiting the nearby and quiet M dwarf TOI-270: Abstract One of the primary goals of exoplanetary science is to detect small, temperate planets passing (transiting) in front of bright and quiet host stars. This enables the characterization of planetary sizes, orbits, bulk compositions, atmospheres and formation histories. These studies are facilitated by small and cool M dwarf host stars. Here we report the Transiting Exoplanet Survey Satellite (TESS)1 discovery of three small planets transiting one of the nearest and brightest M dwarf hosts observed to date, TOI-270 (TIC 259377017, with K-magnitude 8.3, and 22.5 parsecs away from Earth). The M3V-type star is transited by the super-Earth-sized planet TOI-270 b and the sub-Neptune-sized planets TOI-270 c (2.42 ± 0.13 R⊕) and TOI-270 d (2.13 ± 0.12 R⊕). The planets orbit close to a mean-motion resonant chain, with periods (3.36 days, 5.66 days and 11.38 days, respectively) near ratios of small integers (5:3 and 2:1). TOI-270 is a prime target for future studies because (1) its near-resonance allows the detection of transit timing variations, enabling precise mass measurements and dynamical studies; (2) its brightness enables independent radial-velocity mass measurements; (3) the outer planets are ideal for atmospheric characterization via transmission spectroscopy; and (4) the quietness of the star enables future searches for habitable zone planets. Altogether, very few systems with small, temperate exoplanets are as suitable for such complementary and detailed characterization as TOI-270.
I must be missing something. 'Of the three new exoplanets, meaning they're outside our solar system, one is rocky and slightly larger than Earth, while the two others are gaseous and roughly twice Earth's size. Not only is the smaller planet in the habitable zone—the range of distances from a star that are warm enough to allow liquid-water oceans on a planet—but the TOI-270 star is nearby, making it brighter for viewing. It's also "quiet," meaning it has few flares and allows scientists to observe it and its orbiting planets more easily. "We've found very few planets like this in the habitable zone, and many fewer around a quiet star, so this is rare," said Kane. "We don't have a planet quite like this in our solar system."' As far as I can tell, the planet they're describing as "not quite like any in our solar system" is being described as nothing more than "rocky, and slightly larger than Earth". Since Earth is rocky, that leaves "slightly larger than Earth" as its only unique trait.
I think they are referring to the actual gaseous planets Dave, [highlighted in red] that are around twice Earth size, as against the general norm of Neptune/Jupiter and larger size.
