The star and newly discovered exoplanet more closely resemble our sun and earth than any other star and planet we know to date.

Space telescopes such as Kepler and TESS have enabled scientists to expose as many as 4,000 exoplanets over the past fourteen years. The lion’s share of these planets are about the size of our solar system’s ice giant Neptune and are in relatively close orbits around their parent star. It is much more difficult to reveal smaller planets the size of the Earth. Yet astronomers have now succeeded. And not just any.

KOI-456.04
The newly discovered exoplanet called KOI-456.04 is more than a potentially habitable world. First, the planet is less than twice the size of Earth and can therefore measure in size with our home planet. In addition, the planet is in the so-called habitable zone. In addition, a year on KOI-456.04 is almost as long as here and consists of 378 days. Yet this is not even the most striking. One of the most important properties is that the exoplanet orbits around a star that shows remarkable similarities to our sun. As a result, the planet may receive the same amount of light as we do on Earth.

Similarities
The finding means that researchers have tracked down an exoplanet that is very reminiscent of our planet. The star and newly discovered exoplanet are even more like our sun and earth than any other star and planet we know to date. And that is very special. To date, researchers have discovered some exoplanets that are the size of the Earth and may have a rocky composition. A handful of these small planets are also at the correct distance from its parent star. “To find out whether a planet is actually habitable, we also have to look at the parent star,” explains research leader René Heller. Most Earth-known exoplanets known to date are orbiting a red dwarf star. However, these stars mainly emit infrared radiation instead of visible light. And so the pressing question arises whether life on the orbiting planets is possible (see box).

More on red dwarf stars

Red dwarf stars (M stars) are the most abundant and longest living stars in the universe. It means that potential life around these stars may have had twice as much time as life on Earth to form and evolve. In addition, they are a bit smaller and cooler than our own sun. In the search for viable planets, researchers had long aimed their arrows at red dwarf stars. That’s because they often harbor rocky planets. And some of these Earth-like worlds also rotate in the habitable zone. All these ingredients together make red dwarfs very interesting in the search for extraterrestrial life. Recently, however, there has been a shift towards orange dwarf stars (K stars). That’s because planets orbiting red dwarfs are often bombarded with dangerous ones X-ray and ultraviolet (UV) radiation, which can be up to hundreds of thousands of times more intense than what the earth receives from the sun. Orbiting exoplanets are therefore unsure of their lives and can be robbed of their atmosphere at any time. It means that these planets are possible be bone dry.–
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The newly discovered exoplanet orbits a star called Kepler-160, located just over 3,000 light-years away. The star has a surface temperature of 5200 degrees Celsius, which is only 300 degrees Celsius cooler than our sun. In addition, this star emits light reminiscent of the sunlight we receive from our sun. And that makes this star very interesting. Scientists have been watching this striking star closely for some time. Astronomers previously discovered that two planets orbit the star, called Kepler-160b and Kepler-160c. However, these planets are less interesting than KOI-456.04. That’s because both planets are significantly larger than Earth and are close to their parent star. It means it is blazing hot on these planets and life as we know it is unlikely to thrive here. Small variations in the orbital period of Kepler-160c, however, revealed that there may still be a third planet in the system. So researchers decided to check Kepler’s data again.

Discovery
In the hunt for exoplanets, scientists usually study the brightness of a star in hopes of seeing it decrease periodically. Such a regular decrease in brightness may indicate that a planet orbits around that star that occasionally stands between Kepler and the star and blocks some of the starlight. The astronomers out the current study decided, however, to take a different approach. They used a detailed physical model of the stellar variation in brightness. The new algorithm was critical to the discovery of KOI-456.04. “Our improvement is especially important in our search for small, Earth-like planets,” explains Heller. “The planetary signal is so weak that it is almost completely hidden in the noise of the data. Our new search method is slightly better at detecting a signal from an exoplanet. ” In this way, the researchers uncovered KOI-456.04. In the end, the researchers even discovered a fourth planet around Kepler-160.

Promising
All in all, KOI-456.04 proves to be a promising planet where life might be an option. “KOI-456.01 is relatively large compared to many other planets considered potentially habitable,” says Heller. “But the size of the planet in combination with the sun-like star that orbits it makes it very special. As a result, surface conditions on KOI-456.04 may be similar to those on Earth depending on its atmosphere. The amount of light the planet receives from its parent star is about 93 percent of the sunlight we receive from our sun. The surface temperature may be around 5 degrees Celsius, which is only ten degrees lower than the average global temperature on our home planet. ”

These are exciting findings. The researchers nevertheless keep a close eye. That’s because it cannot be completely ruled out that KOI-456.04 is a measurement error rather than a real planet. The team dares to say with about 85 percent certainty that this is a real exoplanet. However, in order to attain formal planetary status, scientists must be 99 percent certain. While some of the most powerful telescopes may be able to validate the promising planet candidate, the future planet hunter PLATO can only really confirm or disprove the existence of the exoplanet. The European planet hunter is expected to launch in 2026 and scan the universe for rocky planets that are in the habitable zone and orbit around sun-like stars. The hope is that scientists will come up with irrefutable evidence for a twin brother of the Earth.