I accidentally discovered a unique exoplanet

While investigating two exoplanets already known to us, researchers suddenly saw a third appearance unknown to us. And now it turns out to be a very special example.

Using ESAs External satellite characterization (ChipsThe researchers focused on the bright star Nu2 Lupi. They wanted to get a closer look at two of the previously discovered exoplanets around this star (Nu2 Lupi b and c). They quietly waited for the two planets to pass in front of the parent star. The two planets appeared precisely, but when Nu2 Lupi c appeared, the researchers suddenly saw a third planet appear in front of the star: Nu 2 Lupi d, orbiting the parent star at a much greater distance.

Accidentally
It is easy to explain why researchers previously overlooked this third planet. The existence of Nu2 Lupi b and c was confirmed by observations from NASA’ Transiting an exoplanet survey satellite (he-goat). This satellite stares at the stars for a long time, hoping to see the brightness of those stars decrease on a regular basis. This dip in brightness could indicate a planet orbiting the star and now and then – when it’s between the telescope and the star – blocking part of the star’s light. This approach lends itself well to the discovery of exoplanets close to their stars, which have a short orbital period, and therefore also pass in front of the star regularly. In this way, the chance of spotting a planet at a much greater distance, which has a much longer orbital period, and therefore also passes in front of the star a lot, is much smaller. So it’s quite a coincidence that CHEOPS has spotted such an exoplanet far from the star.

Size, mass, and orbital period
Especially when you consider that CHEOPS was not actually built to discover planets; The satellite was developed to further study the exoplanets already known to us. Once CHEOPS has discovered Nu2 Lupi d, it can immediately get a closer look at the planet. This shows that the radius of the planet is 2.5 times larger than the radius of the Earth. The mass of the planet is said to be 8.8 times the mass of the Earth. Furthermore, Nu2 Lupi d takes just over 107 days to complete one orbit around the parent star.

value discovery
The discovery of Nu2 Lupi d is not only special, but also very valuable. Most of the exoplanets known to us have long orbits around stars that are not bright enough for detailed follow-up observations (see box). For this reason, little is known about exoplanets far from their parent star. Nu2 Lupi d can change that. The planet orbits a very bright star. “It makes Planet D very exciting,” said researcher Mahmoud Reda Ashagh. “It is an extraordinary planet, unlike any other, and it will certainly be very important for future research.”

When researchers discovered an exoplanet, they naturally wanted to know more about it and, for example, determine its size, weight and what materials the planet was made of. They would also like to consider whether an exoplanet has an atmosphere, and if so, what materials are in that atmosphere. To answer these follow-up questions, researchers need to watch the planet pass in front of the star again. For example, the size of a planet can be inferred from the amount of starlight that is blocked during such a planetary transition. And by studying starlight after it seeps through the planet’s atmosphere during such a transition, one can learn more about the elements in such an atmosphere. But for all of these follow-up studies, a lot of starlight is needed and therefore a bright main star is needed.

the system
Based on data collected by CHEOPS and other observatories that have previously looked at Nu2 Lupi b and c, researchers can already learn more about this particular system. For example, Planet B appears to be mostly rocky, while C and D are composed mostly of water and are surrounded by hydrogen and helium gas. “Although none of these planets are habitable, the system is very interesting because of the diversity of planets,” says researcher Enrique Bali. Hopefully, the follow-up observations will provide more insights into how the different planets form and change over time.

Rings and moons
But it doesn’t stop there. Because Ballet sees a lot of possibilities. “We can also search for rings or moons in the Nu2 Lupi system, as CHEOPS’ superior resolution and stability should allow us to observe celestial bodies that are comparable in size to Mars.”

It is therefore expected that a lot of attention will be paid to Nu2 Lupi in the coming years. This will not only use CHEOPS, but also the Hubble Space Telescope – Assuming NASA is up and running again. And of course James Webb Space Telescope Which will be launched later this year and is very suitable, among other things, for exploration in the skies.