An extrasolar world covered in water?

An extrasolar world covered in water?

An artistic rendering of the exoplanet TOI-1452 b, an asteroid that may be completely covered by the deep ocean. Credit: Benoit Gougeon, University of Montreal

An international research team led by Dr. Charles Cadieux. Université de Montréal student and member of the Institute for Exoplanet Research (iREx), announce the discovery of TOI-1452 b, an exoplanet orbiting one of two small stars in a binary star system in the constellation Draco at a distance of About 100 light-years away from Earth.

Slightly larger in size and mass than Earth, and at a distance from its star, the exoplanet is neither too hot nor too cold for liquid water to exist on its surface. Astronomers think it may be an “ocean planet,” a planet completely covered by a thick layer of water, similar to some of Jupiter and some of Saturn’s moons.

In an article published today Astronomy MagazineCadieux and his team describe observations that shed light on the properties and characteristics of this unique exoplanet.

An international team of astronomers has discovered an exoplanet that could be completely covered in water. Credit: Benoit Gougeon, University of Montreal

“I am very proud of this discovery because it demonstrates the high level of our researchers and instruments,” said René Doyon, professor at Université de Montréal and director of the iREx and Mont-Mégantic (OMM) Observatory. “Thanks to OMM, a special instrument designed in our laboratory called SPIRou, and an innovative analytical method developed by our research team, we were able to detect this one-of-a-kind exoplanet.”

It was NASA’s space telescope TESS that surveyed the entire sky for planetary systems close to our own that led researchers to the trail of this exoplanet. Based on the TESS signal, which dips slightly in brightness every 11 days, astronomers predict a planet 70 percent larger than Earth.

Charles Cadieux belongs to a group of astronomers who conduct ground-based follow-up observations of TESS-identified candidates to confirm their planetary types and characteristics. He uses PESTO, a camera mounted on an OMM telescope developed by Université de Montréal professor David Lafrenière and his Ph.D. Student François-René Lachapelle.

“The OMM played a crucial role in confirming the nature of this signal and in estimating the planet’s radius,” Cadieu explained. “This was not a routine check. We had to make sure that the signal detected by TESS was indeed caused by an exoplanet orbiting TOI-1452, the largest of the two stars in the binary system.”

The host star, TOI-1452, is much smaller than our sun and is one of two similarly sized stars in a binary system. The two stars orbit each other and are so close together—97 AU, or about two and a half times the distance between the Sun and Pluto—that the TESS telescope sees them as a single point of light. But PESTO’s resolution was high enough to distinguish the two objects, and the images showed that the exoplanet was indeed orbiting TOI-1452, as confirmed by subsequent observations by the Japanese team.

ingenuity at work

To determine the planet’s mass, the researchers then observed the system using SPIRou, an instrument mounted on the Canada-France-Hawaii Telescope in Hawaii. Designed primarily in Canada, SPIRou is ideal for studying low-mass stars like TOI-1452 because it works in the brightest infrared spectrum of these stars. Even so, it took more than 50 hours of observation to estimate the planet’s mass, which is believed to be almost five times that of Earth.

An extrasolar world covered in water?

Artistic representation of the surface of TOI-1452 b, which may be an “ocean planet,” or a planet completely covered by a thick layer of liquid water. Credit: Benoit Gougeon, University of Montreal

Researchers Étienne Artigau and Neil Cook, also working at iREx at the University of Montreal, played a key role in analyzing the data. They developed a powerful analytical method capable of detecting planets in the data collected using SPIrou. “LBL method [for line-by-line] Allows us to clean up the data of many parasite signals obtained with SPIRou and reveal faint signatures of planets, such as those discovered by our team,” explains Artigau.

The team also included Quebec researchers Farbod Jahandar and Thomas Vandal, Ph.D.s. student at the University of Montreal. Jahandar analyzed the composition of the host star, which is useful for constraining a planet’s internal structure, while Vandal was involved in analyzing data collected using SPIRou.

a watery world

Exoplanet TOI-1452 b may be as rocky as Earth, but its radius, mass and density suggest a world very different from our own. Earth is inherently a very dry planet; although we sometimes call it the blue planet because about 70% of its surface is covered by oceans, water actually makes up only a small fraction of its mass – less than 1% .

Water may be much more abundant on some exoplanets. In recent years, astronomers have determined and determined the radii and masses of many exoplanets between the size of Earth and Neptune (roughly 3.8 times that of Earth). The density of some of these planets can only be explained if most of their mass is made up of matter lighter than the stuff that makes up Earth’s inner structure, such as water. These hypothetical worlds are called “ocean planets.”

“TOI-1452 b is one of the best candidates for an oceanic planet we’ve discovered to date,” Cadieux said. “Its radius and mass suggest that it is much less dense than one would expect for a planet that is basically composed of metal and rock, like Earth.”

Mykhaylo Plotnykov and Diana Valencia of the University of Toronto are experts in modeling exoplanet interiors. Their analysis of TOI-1452 b suggests that water may make up 30 percent of its mass, a ratio similar to that of some natural satellites in our solar system, such as Jupiter’s moons Ganymede and Callisto, and Saturn’s moons Titan and Enceladus.

To be continued…

Exoplanets like TOI-1452 b are perfect candidates for further observations using the James Webb Space Telescope, or Webb for short. It is one of the few known temperate planets with features consistent with oceanic planets. It’s close enough to Earth that researchers can hope to study its atmosphere and test this hypothesis. And, luckily, it’s in an area of ​​the sky that the telescope can observe year-round.

“Our observations with the Webb telescope are critical to a better understanding of TOI-1452 b,” said Doyon, who outlined the James Webb Component NIRISS concept. “We will book a time on Webb as soon as possible to observe this strange and wonderful world.”

Article “TOI-1452 b: SPIRou and TESS reveal a super-Earth passing an M4 dwarf star in a temperate orbit” published on August 12, 2022 Astronomy Magazine. In addition to Charles Cadieux, René Doyon, Étienne Artigau, Neil Cook, Farbod Jahandar and Thomas Vandal of Université de Montréal iREx, the research team included Nicolas B. Cowan (iREx, MSI, McGill, Canada); Björn Benneke, Stefan Pelletier and Antoine Darveau – Bernier (iREx, UdeM, Canada); Ryan Cloutier, former member of iREx (Harvard University, USA); and from the University of Toronto, France, Brazil, USA, Japan, Spain, Switzerland, Portugal, Hungary, Germany and Crimea Co-author.

New Rare ‘Hot Sub-Neptune’ Exoplanet Discovered

More information:
Charles Cadieux et al., TOI-1452 b: SPIRou and TESS reveal a super-Earth in a temperate orbit crossing an M4 dwarf, Astronomy Magazine (2022). DOI: 10.3847/1538-3881/ac7cea

Courtesy of the University of Montreal

Citation: An extrasolar world covered in water? (24 Aug 2022) Retrieved 24 Aug 2022 from

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