It was revealed by the Cheops space telescope of ESA, a lot of Italy in this new observation
New mysteries revealed space extreme. The European Space Agency has announced that the Cheops space telescope has discovered an unexpected ring around the dwarf planet Quaoar, one similar to the famous rings of Saturn. The discovery – which also took place thanks to Italian space technologies created by Leonardo – also surprised scientists because the dwarf planet Quaoar is part of a collection of small distant worlds known as trans-Neptunian objects (Tnos) and of which about 3000 are known to date. Tnos are found in the outer part of the Solar System, beyond the orbit of the planet Neptune, and the largest are Pluto and Eris. With an estimated radius of 555 kilometers, Quaoar ranks around number seven on the size list and is orbited by a small moon called Weywot, about 80 kilometers in radius.
The European Space Agency points out that studying these dwarf planets is difficult due to their small size and extreme distances, and that Quaoar orbits the Sun at almost 44 times the Sun-Earth distance. Hence also the importance of the observation announced today. The unexpected ring observed around the dwarf planet Quaoar was discovered through a series of observations that took place between 2018 and 2021. Using a collection of ground-based telescopes and the Cheops space telescope, astronomers watched Quaoar traverse a succession of distant stars, briefly blocking out their light as he passed. This event, ESA continues, is known as an occultation.
, planets outside our solar system, ESA’s Cheops discovery also speaks Italian. In fact, Cheops scans the space also thanks to sophisticated ‘eyes’ designed and built by Leonardo. The Cheops space telescope, commissioned by the Italian Space Agency (ASI), was in fact designed and built in the establishment of the Italian aerospace giant Leonardo in Campi Bisenzio (Florence), where engineers, physicists and specialized technicians created the instrument according to the requirements defined by the Inaf researchers of Padua and Catania (Oapd and Oact), in collaboration with the University of Bern. In particular, Leonardo – together with the contribution of small and medium-sized enterprises – oversaw the creation of the telescope’s optical system, based on aspherical mirrors, and of the collimation optics on the focal plane (mirror and lenses).
ESA scientists point out that observing how the light from the occulting star falls provides information about the size and shape of the occulting object and can reveal whether or not the intermediate object has an atmosphere. In this case, smaller drops before and after the main occultation betrayed the presence of material orbiting Quaoar. And occultations are especially valuable tools for scholars because until recently it was difficult to predict exactly when and where they would take place. For an occultation to occur, the alignment between the occulting object (here the Tno), the star and the observing telescope must be extremely precise, explain the ESA scientists, recalling that in the past, it was almost impossible to meet the stringent requirements of accuracy to make sure you see an event. For this reason, to pursue this goal, the Lucky Star project of the European Research Council was created, coordinated by Bruno Sicardy, Sorbonne University and Paris Observatory – Psl (Lesia), to predict the imminent occultations by Tno-objects trans-Neptunians and to coordinate the observation of these events by professional and amateur observers around the world.
Recently, the number of observed stellar occultations has increased and this is largely due to the contribution of data from ESA’s star-mapping Gaia mission. The spacecraft provided such astounding accuracy in its stellar positions that the predictions made by the Lucky Star team became much more certain. One of the people involved in the Lucky Star project is the Italian Isabella Pagano of the INAF Astrophysical Observatory in Catania, and a board member of Cheops. Isabella was contacted by Kate Isaak, ESA’s Project Scientist for the Cheops mission, who was curious as to whether the space telescope would also be able to capture an occultation. “I was a little skeptical about the possibility of doing it with Cheops – admits Isabella Pagano – but we evaluated the feasibility”.
The main problem was that the satellite’s trajectory can be slightly changed due to drag in the upper reaches of the earth’s atmosphere. This is due to the unpredictable solar activity that can affect our planet and inflate its atmosphere. Indeed, the first time the team attempted to observe an occultation with Cheops, involving Pluto, the prediction was not accurate enough and no occultations could be observed. The alignment was more favorable on the second attempt, however, when they observed Quaoar. In doing so, they made the first-ever detection of a stellar occultation by a trans-Neptunian object from space.
“The data from Cheops are extraordinary in terms of signal-to-noise ratio,” says Isabella Pagano. The signal-to-noise ratio is a measure of how strong the detected signal is compared to the random noise in the system. Cheops gives a great deal of noise because the telescope doesn’t look through the distorting effects of Earth’s lower atmosphere. This clarity was crucial in recognizing Quaoar’s ring system because it allowed the researchers to rule out the possibility that the light dips were caused by a spurious effect in Earth’s atmosphere. By combining several secondary detections, made with telescopes on Earth, it was possible to be certain that they were caused by a system of rings surrounding Quaoar.
Bruno Morgado of the Universidade Federal do Rio de Janeiro, Brazil, led the analysis, which combined Cheops’ data with data from large professional observers around the world and amateur citizen scientists who had observed Quaoar occulting various stars. in the last few years. “When we put it all together – reports the Brazilian scientist – we saw dips in brightness that were not caused by Quaoar but which indicated the presence of material in a circular orbit around it. The moment we saw it, we said : ‘Okay, we’re seeing a ring around Quaoar'”.
When it comes to ring systems the giant planet Saturn holds the crown. Known as the ringed planet, Saturn boasts a collection of dust and small moons surrounding the planet’s equator. Despite being an impressive observational sight, the mass of the ring system is quite small. If collected, it would make between one-third and one-half the mass of Saturn’s moon Mimas, or about half the mass of Earth’s Antarctic Ice Shelf. Quaoar’s ring, continues ESA, is much smaller than Saturn’s but no less intriguing. It’s not the only ring system known to exist around a dwarf or minor planet. Two more – around Chariklo and Haumea – were detected through ground-based observations. What makes Quaoar’s ring unique, however, is where it is in relation to Quaoar itself.
Any celestial object with an appreciable gravitational field will have a limit within which an approaching celestial object will be torn apart. This is known as the Roche limit. Dense ring systems are predicted to exist within the Roche limit, as is the case on Saturn, Chariklo, and Haumea. “So what is so intriguing about this discovery around Quaoar is that the ring of material is much further than the Roche limit,” notes Giovanni Bruno of the INAF Astrophysical Observatory in Catania, Italy. This is a mystery because according to conventional thinking, the rings beyond the Roche limit will coalesce into a small moon within a few decades. “As a result of our observations, the classical notion that dense rings survive only within the Roche limit of a planetary body needs to be completely revised,” says Giovanni.
Early findings suggest that the freezing temperatures at Quaoar may play a role in preventing the ice particles from sticking, but more investigations are needed. “The Cheops observations played a key role in establishing the presence of a ring around Quaoar, in an application of high-precision, high-rate photometry that goes beyond more typical mission exoplanet science,” says Kate Isaak . As theorists get to work on how Quaoar rings can survive, the Lucky Star project will continue to watch Quaoar and other Tnos as well as they occult distant stars to measure their physical characteristics and see how many others also have ring systems. And Cheops will return to its original mission to study nearby exoplanets.