They normally require dips of 1 per cent in star brightness to find a planet but managed to find NGTS-4b using the NGTS telescope after the planet dimmed the star it orbits by only 0.2 per cent.
Researchers at the University of Warwick remain uncertain why the planet defies logic and exists in its current location.
"This planet must be tough-it is right in the zone where we expected Neptune-sized planets could not survive", lead author Dr. Richard West of the University of Warwick said in a statement. However NGTS-4b still has its atmosphere of gas.
"Nature appears to be quite inventive with how it can form planets, and we have to be equally inventive in order to catch them".
A Neptunian planet has been found in what should be a "Neptunian Desert" by telescopes run by the University of Warwick in an worldwide collaboration of astronomers. The area, highly irradiated, is indeed hostile to giant planets who cannot keep their gaseous atmosphere. It's also hotter than Mercury with a temperature of 1,832 degrees Fahrenheit.
When you get close to a blazing star, you can discern a region where medium-sized planets like our own icy Neptune are scarce.
"So, this is the first time from the ground we've been able to discover such a tiny signal and that's why we were able to discover a planet that's much, much smaller than Jupiter".
Astronomers made the discovery using the Next-Generation Transit Survey (NGTS), an array of 12 20-centimetre telescopes at the European Southern Observatory's (ESO) Paranal Observatory in Chile's Atacama Desert.
"This planet doesn't have enough mass to hold onto its atmosphere, given the fierce heat from being so close to its star", Coel Hellier, an astronomer at Keele University who wasn't involved in the study, tells Gizmodo. We are now looking at our data to see if we can find more planets in these Neptunian deserts.
"It is truly remarkable that we found a transiting planet via a star dimming by less than 0.2 per cent".
A planet orbiting in a star's habitable zone is regarded as having the best chance of having life.
It's likely, the researchers say, that the planet only recently traveled into its incredibly close orbit with its star, and that big changes are likely to happen within the next million years or so as its atmosphere is blasted away by its star.