An international team of scientists, including the Portuguese Alexandre Correia, from the University of Coimbra (UC), discovered “a particularly interesting planetary system around the star WASP-148”, with two exoplanets with strong interaction, was announced today .
“The discovered system has two planets with masses similar to Saturn, and with orbital periods of only nine and 35 days”, says the UC, in a note sent today to the agency Lusa.
This configuration, he adds, gives rise to variations – “observed for the first time from the Earth’s surface” – in “orbital periods due to gravitational interactions between the two planets”.
Explanation Of What The Discovery Means
Since the discovery, in 1995, of the first exoplanet (planet around a star other than the Sun), that “the number of new known planets does not stop increasing”, underlines the UC, referring that “the search for systems with several planets around the same star is particularly interesting, since they interact with each other and allow to determine more properties about the system “.
When there is a single planet around the star, it has a well-defined orbital period, which does not vary over time.
Whenever the planet passes in front of the star, “we can detect a small decrease in the star’s light, a phenomenon called ‘planetary transit’. Transits occur at regular time intervals, allowing the planet’s orbital period to be measured quite accurately” , explain, cited by UC, the authors of the study, led by the Paris Astrophysics Institute (France).
“If the star hosts a second planet, gravitational interactions between the two planets cause small changes in their orbits” and, as a consequence, “planetary transits occur a little ahead or behind between two passages in front of the star, a phenomenon called ‘variations in transit time’ [TTV], “they add.
Although planned from a theoretical point of view, TTVs remained unobserved for a long time, despite numerous researches with terrestrial telescopes.
In most cases, “gravitational interactions take TTV only a few seconds or less, which are very difficult to detect” – the Kepler space telescope was “the first to be able to measure TTV on a planetary system, in 2010”. Other measurements followed, but always through space telescopes like that.
The observation of TTV requires very precise instruments and simultaneously large mass planets that are in relatively close orbits.
In this discovery, Alexandre Correia, a researcher at the Physics Center of the Faculty of Sciences and Technology of the University of Coimbra, was involved in the analysis of the interactions between the planets.
“We verified with numerical simulations that the system is stable up to inclines of 35 degrees, and that the observed TTVs are in line with what would be expected for this type of system”, reports the scientist.
The WASP-148 planetary system now found “was discovered using only terrestrial telescopes”, the team of researchers points out.
“The first planet, with a Saturn-like mass and an orbital period of only about nine days, was first observed by the SuperWASP instrument, installed at the Roque de los Muchachos Observatory in La Palma, in the Canary Islands, Spain.”
As of 2014, the star was also observed with the high-resolution spectrograph SOPHIE, installed at the Haute-Provence Observatory, in France, which measures variations in the star’s speed.
The combination of these observations led to the conclusion that the star WASP-148 hosts a second planet, also with a mass similar to Saturn and an orbital period of about 35 days.
Unlike the first planet at nine days, the second planet at 35 days does not pass in front of the star.
“This is due to the fact that the two orbital planes are different. It is not yet possible to know exactly what the inclination is between the two orbits, but computer simulations on the WASP-148 system show that for the system to remain stable, the inclination may be maximum 35 degrees “, explains Alexandre Correia.
The ratio between the two orbital periods is close to four, so, says the UC, “the gravitational interactions between the planets are amplified by a phenomenon known as resonance. Since the masses of the planets are high, this system is the ideal candidate for observe TTVs from Earth “.
Using small telescopes located in the Canary Islands and France, transits were found to occur a quarter of an hour late or in advance.
The scientists point out that the result of this investigation constitutes “the first detection of TTV from the Earth’s surface, obtained through more than ten years of observations”.
In the coming months and years, “the WASP-148 system will be the subject of numerous theoretical studies and additional observations, which will make it possible to improve measurements of its properties and better understand its structure and evolution”, in particular, “the system will be observed in soon by NASA’s TESS (Transiting Exoplanet Survey Satellite) space telescope. ”
What Was The Conculsion
These observations, conclude the researchers, “with much more precision than those made on Earth, will measure nine consecutive transits of the planet in nine days, which will allow to determine the inclination between the two orbits”.
The study will soon be published in the journal Astronomy & Astrophysics