Astronomers David Kipping, from Columbia University in NY and Alex Teachey are reporting and publishing the results Science Advances journal observing all the hypothesis and anomalies, comparing the data they have other planets in the system or stellar activity but they still can not explain the new discovery. Estimated to have a mass several times of Jupiter, the planet is nearly certainly gaseous and not likely to support life as we know it. Such gargantuan moons do not exist in our own solar system, where almost 200 natural satellites have been catalogued.
However, this moon is unusual because of its large size, which is more comparable to the diameter of Neptune.
The exomoon and its planet orbit Kepler-1625, a star similar in temperature to our sun but about 70 percent larger. This mass-ratio is similar to the one between Earth and the Moon.
After it ended the telescope detected a second and much smaller decrease in the star's brightness three-and-a-half hours later.
However, exomoons are harder to detect than exoplanets because they are smaller than their companion planet, and so their transit signal is weaker when plotted on a light curve that measures the duration of the planet crossing and the amount of momentary dimming. Kipping and his colleague Alex Tichy made their discovery based on the more than 300 distant planets, which were discovered using the space telescope Kepler.
Detections of exoplanets come thick and fast nowadays as a multitude of telescopes both on the ground or in orbit, are programmed to constantly scan the skies for the myriad of exoworlds we are now accustomed to finding.
Hubble was also able to measure that the planet began its transit earlier than expected, consistent with the "wobble" that occurs when a planet and moon orbit the same center of gravity.
The exomoon is exponentially larger than our solar system's biggest moon. Such gargantuan moons are unknown in our own Solar System.
"We saw little deviations and wobbles in the light curve that caught our attention", Kipping said in a news release. However, the researchers' alloted observation time ended before the planet could complete its transit.
"You do sometimes form moons that big through the coalescing of disk material", Kipping said. In addition, because they orbit the planet, their own orbit is also constantly shifting. "Both bodies, however, are considered to be gaseous and therefore unsuitable for life as we know it", Kipping added. Now, two scientists from Columbia University in New York (USA) have used the incomparable capabilities of the NASA/ESA Hubble Space Telescope to study the star Kepler-1625, 8,000 light-years away, and its planet in more detail.
"Furthermore, the size we've calculated for this moon, about the size of Neptune, has hardly been anticipated and so that, too, is reason to be careful here".
Scientists called it "absolunet" by analogy with the name of earth-like planets orbiting other stars. "But moving forward, I think we open the door to search for such worlds", said Teachey.