Cold Neptune and two Temperate Super-Earths found orbiting near stars

A "cold Neptune" and two possibly inhabitable worlds are part of a set of five newly found exoplanets and eight exoplanet candidates, who have found themselves orbiting nearby Red Zwilling Stars identified by a team led by Carnegie's Fabo Feng and Paul Butler in the Astrophysical Journal Supplement Series.

The two potentially habitable planets are GJ180 and GJ229A, among the closest stars to the Sun, which makes them primary targets for space and land-based observations by the next generation of telescopes.

Both are super-Earths with at least 7.5 and 7.9 times our planet's mass and orbital periods of 106 and 122 days respectively.

The planet Neptune, which orbits GJ433 on a distance that is supposed to frozen surface water, is potentially the first of its kind to be a realistic candidate to future direct imaging.

"GJ 433 d is the nearest, widest, and coldest Neptune-like planet ever detected," Feng added.

The newly found worlds were found using a radial speed technique for discovering stars, winning not only from the effect of star gravity on the earth but also from a difference in planet gravity. This causes minor wobbles in the orbit of the star which can be observed using advanced tools. Because of their smaller mass, the red dwarfs are the main class of planetary planets around which this strategy can be used.

The red dwarfs, also called the M dwarfs, are more cool and smaller than the Sun and the most common stars in the Galaxy and the only class considered to host earth planets. Red dwarfs can host planets on their surfaces in much closer orbits at the right temperature than those found around other types of stars in this so-called habitat.

Feng further explained: "Many planets that orbit red dwarfs in the habitable zone are tidally locked, meaning that the period at which they spin around their axes is the same as the period at which they orbit their host star. This is similar to how our Moon is tidally locked to Earth, meaning that we only ever see one side of it from here."

"As a result, these exoplanets are a very cold permanent night on one side and very hot permanent day on the other--not good for habitability. GJ180d is the nearest temperate super-Earth to us that is not tidally locked to its star, which probably boosts its likelihood of being able to host and sustain life", it added.

The other potentially habitable planet, GJ229Ac is the nearest temperate super-Earth, located in a system in which the host star has a brown dwarf companion. Brown dwarfs can not support hydrogen fusion, sometimes referred to as failed stars.

The GJ229B was one of the first brown dwarfs to be imagined. It is not known, however, how exoplanets develop and evolve into a dwarf, the star-brown binary system is the best case study for this planetary system.

Feng said: "Our discovery adds to the list of planets that can potentially be directly imaged by the next generation of telescopes. Ultimately, we are working toward the goal of being able to determine if planets orbiting nearby stars host life."

Carnegie co-author Jeff Crane further added, "We eventually want to build a map of all of the planets orbiting the nearest stars to our own Solar System, especially those that are potentially habitable."

Once targets have been found in the UVES archives, researchers have used observations on three instruments for planet-hunting to improve the data accuracy.

"Combining the data from multiple telescopes increases the number of observations and the time baseline, and minimizes instrumental biases," Butler added.