Exoplanets of the same size as Earth can be some of the hardest to detect, but their number is growing, and now researchers from Max Planck's Department of Solar System Research, Georg August University of Göttingen and the Observatory in Sonneberg have added 18 eclanets to it. ever-growing list (from May 1, 2019, there were 4,058 confirmed planets in 3,033 systems, with 658 systems with more than one planet). All 18 new exoplanets were found during a redefining of data from the highly efficient Kepler Space Telescope planet-hunting mission with a new, more sensitive search algorithm called Transit Least-Squares .
The first fruits of the new algorithm can be found in peer-reviewed results published in the journal Astronomy & Astrophysics in two new papers, here and here. The first paper that focused on the exoplanet K2-32e was published a few weeks ago and the second paper on the 17 other exoplanets was published on May 21, 2019.
These newly discovered worlds are some of the smallest discovered far . They range in size from only 69 percent of the Earth's diameter (EPIC 201497682.03, 831 light-years away) to just over twice the size of Earth. Everyone hid in the Kepler data and was not found in previous searches because the search algorithms were not sensitive enough. Like many other exoplanet hunters, Kepler used the transit method, where a planet passes in front of its star, seen from our vantage point here on Earth. As the planet passes in front of the star, it blocks a small amount of light from the star, which can then be measured by astronomers. As René Heller of the Max Planck Institute, first author of both papers, explained:
Standard search algorithms attempt to identify sudden drops in brightness. In fact, a star disc appears slightly darker at the edge than in the middle. Therefore, when a planet moves in front of a star, it blocks less starlight for the first time than in the mid-term of transit. The maximum attenuation of the star occurs in the middle of the transit just before the star gradually becomes brighter.
As might be expected, it is easier to discover larger planets as they block more light from their stars during a transit. The amount of light blocked by smaller planets can easily be missed, as it can be difficult to distinguish from the star's luminescent fluctuations and background noise that are part of these observations.
The new Transit Least Quadratic algorithm improves the sensitivity of the transit method, making it easier to find smaller planets like Earth, as Michael Hippke from Sonneberg Observatory said:
Our new algorithm helps draw a more realistic picture of the exoplanet population in space. This method represents an important advance, especially in the search for earth-like planets.
All the new planets were found in data from the K2 part of the K2 part. The K2 phase was started after the primary mission ended in 2013, following technical errors in the telescope's reaction wheels, which helped keep Kepler stable for its observations of stars (K2 ended in 2018). These researchers analyzed the 517 stars from K2 that were known to have at least one planet each.
So what are these new planets like?
Unfortunately, most of them are not good candidates for life and circling their stars closer than before, with temperatures ranging from 212 degrees Fahrenheit (100 degrees Celsius) to 1,832 degrees Fahrenheit (1,000 degrees Celsius). One of them, however, EPIC 201238110.02, revolves within its star's habitable zone, the region around a star where there may be liquid water. EPIC 201238110.02 is 1.87 times the Earth's diameter and 522 light-years away.
The first planet, K2-32e, orbits the star EPIC 205071984 and is the fourth known planet in that system. The other three planets are all Neptune size.
It is now expected that astronomers will be able to use at least 100 terrestrial planets in primary Kepler mission phase data – using Transit Least Squares. This is good for discovering many more such worlds with other telescopes, such as. NASA's groundbreaking TESS satellite, the newest member of the planet hunting family, has picked up where Kepler relaxed.
The European Space Agency PLATO is another mission that will benefit from these results with the new algorithm, according to Laurent Gizon, CEO of Max Planck Institute for Solar System Research:
This new method is also particularly useful for to prepare for the forthcoming PLATO mission to be launched in 1926 by the European Space Agency
Future telescopes, both space and land-based, are expected to find thousands of more exoplanets in the coming years, including those that are earth-sized, as well as these 18 new ones. Some telescopes, such as NASA's upcoming James Webb Space Telescope will also be able to analyze the atmospheres of some of these distant worlds and look for trace gases that may be a sign of life.
Bottom Line: With Another 18 Earth- Medium-sized exoplanets stored in Kepler data, astronomers continue to confirm that this kind of rocky world is found not only elsewhere, but also that they are quite common. How many of them can turn out to be habitable for some kind of life is still unknown, but these discoveries bring us closer to finding the first evidence of life outside our solar system.
Source: Minimum Square Survey – I. Discovery and Validation of a Earth Size Planet in the Four-lane System K2-32 near the 1: 2: 5: 7 resonance
Source: Minimum Square Survey – II. Discovery and validation of 17 new sub- to super-earth planets in K2 multi-plane systems
Via the Max Planck Institute for Solar System Research