Years of searching for exoplanets have paid off. The latest findings have 350 new planets outside our Solar System, bringing the total exoplanet discoveries to 5,000.
Quoted from Science Alert, this finding is the result of developing an algorithm to identify a decrease in the brightness of a star that indicates the existence of an orbiting exoplanet.
"Discovering hundreds of new exoplanets is a significant achievement, but what sets this work apart is how it will explain the features of the exoplanet population as a whole," said astronomer Erik Petigura of the University of California, Los Angeles (UCLA), United States.
The Kepler space telescope spent nearly a decade in orbit following the Earth around the Sun, gazing for long periods of time at parts of the sky and recording the stars.
The goal is to capture the faint drop in brightness that occurs in starlight, when an exoplanet passes between us and the star. These observations allow astronomers to find out how closely the exoplanet is orbiting the star.
This process may sound easy. But identifying planetary signals in the midst of noise is a long and tedious job that is usually done visually. Humans, traditionally, have performed much better at signal detection than software.
But software is getting more and more sophisticated, and an algorithm developed by UCLA astronomer Jon Zink helps overcome this weakness. The research team entered 500 terabytes of data from Kepler's second mission, which included more than 800 million images, into the software. The result is 381 previously identified exoplanets, and 366 completely new potential exoplanets.
Among the findings is an interesting system containing two Saturn-like gas giants orbiting very close to their parent star and to each other. Planetary scientists look for unusual cases like these, because they allow us to understand the parameters for planetary systems.
"The discovery of each new world provides a unique view of the physics that played a role in planet formation," Zink explains.
Zink and his team aren't the only scientists working on the Kepler data. Another effort led by Hamed Valizadegan of the Universities Space Research Association (USRA) has added more than 300 exoplanets to the confirmed list.
When a signal is identified as a potential exoplanet, it is initially put forward as a candidate. That is, it could be an exoplanet, but additional work is needed to confirm it. Astronomers need to rule out all other possibilities. The exoplanets discovered by Zink and his team fall into this category.
How many are Earth-like?
There are thousands of potential exoplanets. On November 18, the number of confirmed exoplanets was much lower, at 4,575.
Valizadegan and colleagues have developed a deep neural network called ExoMiner that runs on NASA's Pleiades supercomputer. This system can distinguish between real and "fake" exoplanets.
"When ExoMiner says something is a planet, it's pretty sure it's a planet. ExoMiner is very accurate and in some ways more reliable than existing machine classifiers and human experts it's meant to emulate because of the bias that comes with human labeling," says Valizadegan.
He and his team used ExoMiner to analyze candidate exoplanet data from the Kepler Archives. To be clear, these are exoplanets that have been identified, but are awaiting confirmation. ExoMiner managed to confirm 301 of them.
None of the newly confirmed exoplanets are Earth-like, or in the potentially habitable zones of their Solar System. However, the findings of these planets are still important for understanding the statistics of planetary systems in the Milky Way galaxy.
