NGTS-14Ab, an alien world slightly larger than Neptune orbiting around an orange dwarf in the binary system NGTS-14, joins a growing number of exoplanets that reside in the so-called Neptunian desert, a sparsely populated region between hot-Jupiter and super-Earth planets.
An artist’s impression of the Neptune-sized planet NGTS-14Ab. Image credit: Sci-News.com.
“The first generation of wide-field transit surveys unveiled the rich diversity of hot Jupiters,” said Dr. Alexis Smith from the Institute of Planetary Research at the German Aerospace Center and colleagues.
“These planets, although intrinsically rare, have been discovered in numbers large enough to enable statistical population analyses such as those investigating inflation.”
“Transiting hot Jupiters also remain the best-studied individual planetary systems, with characterization observations such as atmospheric transmission spectroscopy pioneered on these objects.”
“NASA’s Kepler and K2 missions, and the ongoing TESS mission subsequently revealed a large population of small (less than 2-3 Earth radii), short-period planets,” they said.
“In between these two populations, however, lies a relatively unpopulated region of parameter space, often referred to as the sub-Jovian or Neptunian desert.”
The NGTS-14 binary system resides 1,033 light-years away in the southern constellation of Grus.
Also known as 2MASS J21540423-3822388 and TIC 197643976, it is approximately 5.9 billion years old.
It consists of a K1V-type dwarf star, NGTS-14A, with a long-period companion, NGTS-14B, which is likely to be an M2.5V dwarf.
NGTS deep stacked image centered on NGTS-14A. The Gaia positions of NGTS-14A and NGTS-14B are indicated with a red ‘+’ and a blue ‘x,’ respectively. The pink circle indicates the NGTS photometric aperture. Other Gaia sources are marked with orange triangles. North is up, and East to the left. Image credit: Smith et al., arXiv: 2101.01470.
The newfound planet, NGTS-14Ab, orbits the primary star in the system once every 3.54 days.
It has a radius about 30% larger than that of Neptune (0.44 Jovian radii), and is around 70% more massive (0.09 Jovian masses).
“NGTS-14Ab’s orbital period of just over 3.5 days places it in the Neptunian desert, a thus far sparsely-populated region of parameter space,” the astronomers said.
They detected the transits of NGTS-14Ab using the Next Generation Transit Survey (NGTS) facility at ESO’s Paranal Observatory.
Follow-up observations with several ground-based telescopes, as well as data extracted from TESS full-frame images, confirmed the planetary nature of the transit signals.
“NGTS-14Ab appears to just far enough from its star that it is able to maintain a significant atmosphere, resulting in a density similar to those of Uranus and Neptune,” the researchers said.
Their paper will be published in the journal Astronomy & Astrophysics.
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A.M.S. Smith et al. 2021. NGTS-14Ab: a Neptune-sized transiting planet in the desert. A&A, in press; arXiv: 2101.01470
