Giant Alien Planet

Astronomers have detected a hidden planet by examining the orbits of the known worlds in the star system known as Kepler-139. The newfound alien planet, Kepler-139f, is a gigantic world roughly twice the mass of Neptune and 35 times the mass of Earth. It takes 355 days to orbit its star. Despite its giant size, Kepler-139f had evaded detection until now.

NASA’s Kepler space telescope discovered nearly 3,000 planets in the nine years it operated. But it relied on worlds transiting, that is, passing between their star and Earth. When they do that, the resulting dimming of the star allowed astronomers to identify planets and calculate their size. But Kepler couldn’t see planets traveling above or below the wedge of space between it and the star, so any outliers remained unseen.

But when the hidden world is part of a multiplanet system, astronomers could maybe find it despite its inclined orbit. And Kepler-139 has three rocky transiting super-Earths; later a fourth gas giant was discovered. Gaps between their orbits suggested that other worlds might be present. Precise measurements of the orbits allowed the astronomers to infer the existence of at least one more planet. It seems the problem is not exactly in finding non-transiting planets, but in finding situations where they can deduce where the non-transiting planet is located.

After Kepler initially identified a world, observations from the ground often followed. By using a planet’s radial velocity, astronomers could measure the amount the planet tugged on its star, which allowed them to determine the planet’s mass. Radial velocity measurements could also reveal new worlds, which is what happened with the outermost gas giant, Kepler-139e.

Each planet is pulled not only by its star but also by other planets in the system, even if that planet cannot be seen from Earth. These pulls can affect how swiftly a planet transits, which creates ‘transit timing variations’. Such variations can reveal worlds that don’t cross the star.

Scientists looked for gaps in known systems. Then they used both radial velocity and transit timing variation measurements to hunt for a missing planet. While the radial velocity observations did not conclusively point toward another planet, when combined with the transit timing variations they revealed a fifth planet in the system, Kepler-139f, which was between the outermost super-Earth and the gas giant.

The discovery of Kepler-139f helped answer a question about Kepler-139c, the outermost super-Earth. Originally, the reports for 139c showed an unusually large density for a sub-Neptune-sized planet. Because the scientists didn’t yet know about 139f, they had attributed some of its pull on its star to 139c. But the new data suggests a more typical density for 139c while leaving the densities for 139d and 139b unchanged. These revisions provide indirect evidence for 139f.

It is possible that there may be other hidden worlds around Kepler-139. For instance, there is a prominent gap between 139b and 139c.

Both Kepler and NASA’s more recent exoplanet hunting mission (the Transiting Exoplanet Survey Satellite) were sensitive to planets orbiting close to their star. Inner worlds made more transits, which allowed scientists to confirm the planet’s existence. But transiting planets with wider orbits made fewer passes in front of their sun, so they were harder to observe and confirm.

In addition, the radial velocity method tends to find larger planets, because massive worlds tug stronger on their stars. Also, the closer a planet is to its sun, the stronger its tug. That’s why so many of the discovered exoplanets were Jupiter-sized worlds whose orbit only took a few days.

All of these factors mean it’s harder to discover smaller planets that are farther away, especially if they don’t transit their star. But by combining various methods, astronomers can find smaller worlds orbiting farther from their star.

And soon it will be harder for those planets to hide. In 2026, the European Space Agency will launch the Planetary Transits and Oscillations of Stars (PLATO) mission. It will conduct its own survey of transiting planets, as well as revisit Kepler’s field. By providing additional transit times for planets detected by Kepler more than a decade earlier, PLATO will enable the discovery of more misaligned worlds.

 

https://www.msn.com/en-us/news/technology/astronomers-discover-giant-alien-planet-35-times-more-massive-than-earth-hiding-in-a-known-star-system/ar-AA1IE595?ocid=hpmsn&cvid=feaec06498da45f787cb55fd4cd8125e&ei=15