The exoplanet orbits – along with two other planets – around a roughly 10 billion year old star.
Scientists have found some ancient planets around an orange dwarf star. These are three planets, one of which is a hot, rocky super-Earth that has been given the name TOI-561b. “TOI-561b is one of the oldest rocky planets ever discovered,” said researcher Lauren Weiss.
The researchers estimate that the entire TOI-561 system is about 10 billion years old. This makes the system one of the oldest known systems. The discovery of the ancient, rocky super earth is therefore very special. Because it means that rocky planets – like our Earth – have a long life. Moreover, the first rocky planets also saw the light of day long ago. “The existence of this exoplanet shows that the universe has produced rocky planets almost since birth,” concludes Weiss.
A super-Earth is a rocky planet with a mass greater than that of Earth but smaller than that of the planets Uranus or Neptune. They also have a solid surface. The first super Earth was discovered in 2005. Meanwhile, five super-Earths have been found – including the most promising ones K2-18b – which could possibly be livable. They are located near their parent star in the so-called habitable zone.
In the study the researchers also managed to reveal some interesting properties of TOI-561b. It turns out that the planet is about 50 percent larger than our earth. In addition, TOI-561b takes less than half a day to complete a circle around its parent star. And that is extremely short. “For every day you are on Earth, this planet revolves around its star twice,” explains researcher Stephen Kane.
So TOI-561b orbits its star in a very close orbit. And that means that the temperatures on the planet can get quite high. The estimated average surface temperature is even more than 1700 degrees Celsius.
Although TOI-561b has a mass almost three times that of our Earth, the team calculated that its density is equal to that of our planet. And that is quite remarkable. “This is surprising, because you would expect (in view of the greater mass, ed.) That the density would be higher,” says Kane. “That is consistent with the idea that the planet is very old.” Because the older a planet is, the lower its density should be. “That’s because there weren’t that many heavy elements available a long time ago that subsequently produced planets,” explains Kane. Heavy elements are formed by fusions in stars as they age. Eventually, stars explode, hurling these elements around the universe. New stars and planets are then born from this dust.
Unfortunately, the researchers suspect that TOI-561b is not viable. It would be far too hot to accommodate life as we know it. However, that does not mean that the planet has always been uninhabitable. Perhaps it was a possibility in the distant past. Astronomers are therefore constantly trying to understand the relationship between the mass and radius of planets they find. This information provides more insight into the internal structure of planets that are too far away to visit with current technology. “Information about the interior of a planet gives us an idea of whether the surface is habitable for life,” explains Kane. “While TOI-561b is unlikely to be inhabited today, it can be seen as a precursor. There may still be many rocky worlds around the oldest stars in the universe waiting to be discovered. ”
The ancient planet was discovered with the help of a planet hunter Transiting Exoplanet Survey Satellite (TESS). Launched in April 2018, TESS opened the hunt for nearby planets in July of the same year. Since then, the telescope has discovered many exoplanets. Last April, the planet hunter discovered her first earthy planet and already tracked her first exokometen on. And many more discoveries will undoubtedly follow. In a few years, TESS will study at least 500,000 nearby stars and detect Earths and super-Earths around many of them. TESS is also expected to observe hundreds of thousands of binary stars, leaving many more planets orbiting such binary systems waiting to be discovered.
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