Spanish scientists have discovered the least dense planet in the Universe

While searching through a table of material densities that best matched the density of the planet found, astrophysicist Francisco J. Pozuelos of the Institute of Astrophysics of Andalusia (IAA-CSIC) came across cotton candy: 0.05 grams per cubic centimeter. And that’s exactly the answer he gave to an MIT journalist who asked him to give a clear example of what he meant by “ultralight.”

It was about WASP-193b, a planet that Spanish scientists found. “accidentally”“Four years ago, Khalid Barkaoui, then a graduate student and now a postdoc at MIT, discovered something unusual in the data he was studying,” he says. Public Pozuelos, co-principal investigator of the study.

By analyzing signals collected by the WASP (Wide Angle Search for Planets) project, an international collaboration involving astronomical observatories in both hemispheres, researchers confirmed that the Sun-like star located 1,200 light-years from Earth, WASP 193, looked like reduce its brightness occasionally.

The reason was a huge planet passes by every 6.25 days, blocking part of the field of view from the ground observatory. So they named it WASP 193b.

Error in calculations?

They then began studying its mass using the radial velocity method, which analyzes the fluctuations in the star’s motion caused by to pull that the planet in question acts around itself. The greater its mass, the more it will attract the star and the greater the shift in the wavelength of its spectrum.

And they stayed stunned by the results. The star hardly wavered. “It took us four years to publish this paper because we couldn’t believe that our calculations were correct, and we repeated them over and over again, using different codes,” recalls Pozuelos.

But his measurements were correct. What didn’t live up to their expectations was that the huge planet would end up in the featherweight division. Specific, the lightest found to date. “Of the planets that we have characterized well, given their measured mass, there are still only eight or nine with densities less than 0.1 grams per cubic centimeter,” Pozuelos tells us.

Does not fit current models of planet formation.

The discovery, published this week in Nature Astronomyis key because it reveals current patterns of planet formation that They don’t explain how this could happen with such little mass and such low density. According to these models, the atmosphere will be lost as it expands, and therefore the planet will become smaller.

“Our hypothesis is that WASP 193b has very great atmosphere and rarefied, consisting of very light elements such as hydrogen and helium,” says Pozuelos. And this is exactly what they intend to test in future observations.

“On the one hand, we want to compare the share volatile elements and heavy elements in its atmosphere. On the other hand, we wonder if atmospheric loss is still happening,” he adds.

Why WASP193b is important

How might this contribute to our knowledge of the universe? “Understanding the origin of these ultra-light planets will allow us reformulate models formation of planets that have not yet been completed, in order to find a more reliable one, where those like WASP193b are also suitable,” says the astrophysicist.

However, reformulating the model does not happen overnight. “We must build it step by step, step by step, in order to ultimately come to an understanding mechanisms that gave rise to the solar system and to Earth,” says the astrophysicist.