Tyler O'Neal, Staff Editor EARTH SCIENCES

Université de Montréal student discovers an ocean planet about 100 light-years from Earth

An international team of researchers led by Charles Cadieux, a Ph.D. student at the Université de Montréal and member of the Institute for Research on Exoplanets (iREx), has announced the discovery of TOI-1452 b, an exoplanet orbiting one of two small stars in a binary system located in the Draco constellation about 100 light-years from Earth. Artistic representation of the surface of TOI-1452 b, which could be an "ocean planet", i.e. a planet entirely covered by a thick layer of liquid water. CREDIT Benoit Gougeon, Université de Montréal

The exoplanet is slightly greater in size and mass than Earth and is located at a distance from its star where its temperature would be neither too hot nor too cold for liquid water to exist on its surface. The astronomers believe it could be an “ocean planet,” a planet completely covered by a thick layer of water, similar to some of Jupiter’s and Saturn’s moons.

In an article published today in The Astronomical Journal, Cadieux and his team describe the observations that elucidated the nature and characteristics of this unique exoplanet.

“I’m extremely proud of this discovery because it shows the high calibre of our researchers and instrumentation,” said René Doyon, Université de Montréal Professor and Director of iREx and of the Observatoire du Mont-Mégantic (OMM). “It is thanks to the OMM, a special instrument designed in our labs called SPIRou, and an innovative analytic method developed by our research team that we were able to detect this one-of-a-kind exoplanet.”

It was NASA’s space telescope TESS, which surveys the entire sky in search of planetary systems close to our own, that put the researchers on the trail of this exoplanet. Based on the TESS signal, which showed a slight decrease in brightness every 11 days, astronomers predicted a planet about 70% larger than Earth.

Charles Cadieux belongs to a group of astronomers that does ground follow-up observations of candidates identified by TESS to confirm their planet type and characteristics. He uses PESTO, a camera installed on the OMM’s telescope that was 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 estimating the planet’s radius,” explained Cadieux. “This was no routine check. We had to make sure the signal detected by TESS was really caused by an exoplanet circling TOI-1452, the largest of the two stars in that binary system.”

The host star TOI-1452 is much smaller than our Sun and is one of two stars of similar size in the binary system. The two stars orbit each other and are separated by such a small distance — 97 astronomical units, or about two and a half times the distance between the Sun and Pluto — that the TESS telescope sees them as a single point light. But PESTO’s resolution is high enough to distinguish the two objects, and the images showed that the exoplanet does orbit TOI-1452, which was confirmed through subsequent observations by a Japanese team.

Ingenuity at work

To determine the planet’s mass, the researchers then observed the system with SPIRou, an instrument installed on the Canada-France-Hawaii Telescope in Hawai’i. Designed in large part in Canada, SPIRou is ideal for studying low-mass stars such as TOI-1452 because it operates in the infrared spectrum, where these stars are brightest. Even then, it took more than 50 hours of observation to estimate the planet’s mass, which is believed to be nearly five times that of Earth.

Researchers Étienne Artigau and Neil Cook, also with iREx at the Université de Montréal, played a key role in analyzing the data. They developed a powerful analytic method capable of detecting the planet in the data collected with SPIRou. “The LBL method [for line-by-line] allows us to clean the data obtained with SPIRou of many parasite signals and to reveal the weak signature of planets such as the one discovered by our team,” explained Artigau.

The team also includes Quebec researchers Farbod Jahandar and Thomas Vandal, two Ph.D. students at the Université de Montréal. Jahandar analyzed the host star’s composition, which is useful for constraining the planet’s internal structure, while Vandal was involved in analyzing the data collected with SPIRou.

A watery world

The exoplanet TOI-1452 b is probably rocky like Earth, but its radius, mass, and density suggest a world very different from our own. Earth is essentially a very dry planet; even though we sometimes call it the Blue Planet because about 70% of its surface is covered by ocean, water only makes up a negligible fraction of its mass — less than 1%.

Water may be much more abundant on some exoplanets. In recent years, astronomers have identified and determined the radius and mass of many exoplanets with a size between that of Earth and Neptune (about 3.8 times larger than Earth). Some of these planets have a density that can only be explained if a large fraction of their mass is made up of lighter materials than those that make up the internal structure of the Earth such as water. These hypothetical worlds have been dubbed “ocean planets.”

“TOI-1452 b is one of the best candidates for an ocean planet that we have found to date,” said Cadieux. “Its radius and mass suggest a much lower density than what one would expect for a planet that is basically made up of metal and rock, like Earth.”

The University of Toronto’s Mykhaylo Plotnykov and Diana Valencia are specialists in exoplanet interior modeling. Their analysis of TOI-1452 b shows that water may make up as much as 30% of its mass, a proportion 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…

An exoplanet such as TOI-1452 b is a perfect candidate for further observation with the James Webb Space Telescope, or Webb for short. It is one of the few known temperate planets that exhibit characteristics consistent with an ocean planet. It is close enough to Earth that researchers can hope to study its atmosphere and test this hypothesis. And, in a stroke of good fortune, it is located in a region of the sky that the telescope can observe year-round.

“Our observations with the Webb Telescope will be essential to better understanding TOI-1452 b,” said Doyon who overviewed the conception of James Webb's component NIRISS. “As soon as we can, we will book time on Webb to observe this strange and wonderful world.”

China’s CMA Earth System Modeling, Prediction Center shows how mountain events could improve safety with higher resolution weather models

Tyler O'Neal, Staff Editor EARTH SCIENCES

High-resolution modeling of a “blizzard-like” storm that killed 21 ultramarathoners in 2021 shows where coarser models underestimated the storm — and highlights the need for ultra-high-resolution forecasts for events held in mountainous terrain.

In late May of 2021, 172 runners set out to tackle a 100-kilometer (62-mile) ultramarathon in northwestern China. By midday, as the runners made their way through a rugged, high-elevation part of the course, temperatures plunged, strong winds whipped around the hillslopes and freezing rain and hail pummeled the runners. By the next day, the death toll from the sudden storm had risen to 21. Ultra-high-resolution weather models should be used for forecasts for athletic events held in mountainous terrain, as highlighted by a new study in JGR Atmospheres that uses the 2021 Gansu ultramarathon as a case study. Credit: David Marcu/Unsplash

A new study revisits the deadly event to test how hyper-local modeling can improve forecast accuracy for mountain events. The runners ran into trouble because hourly weather forecasts for the race underestimated the storm. The steep mountain slopes had highly localized effects on the wind, precipitation, and temperature at too small a scale for the weather forecasts for the event, according to the new study, which is published in the AGU journal JGR Atmospheres.

Hourly forecasts for the 2021 race were based on relatively large-scale atmospheric processes, with models running at a resolution of three kilometers—sufficient for most regional predictions, but too coarse to capture the “hyper-local” weather like the storm that struck the course, says Haile Xue, a climate scientist at China’s CMA Earth System Modeling and Prediction Centre and lead author of the new study. Even though wind and cold temperature advisory had been issued the night before, it lacked the resolution required to pinpoint the danger zones on the course.

“An apparent temperature forecast based on a high-resolution simulation may be helpful” in addition to general regional forecasts, Xue says. Conditions like the 2021 storm are common in mountains with extremely high elevations, such as Mount Everest and Denali, the paper states. While less frequent at lower elevations, when such storms do occur, they can strike suddenly and lead to injuries and loss of life.

The new study uses topographic data from the course, at tens of meters of resolution rather than kilometers, to model the hyper-local weather conditions created by the mountains. With a resolution two orders of magnitude finer than the original forecasts for that weekend, as well as detailed considerations of mountainous topography, the model accurately recreated the storm conditions from the race and even offered greater insight into what may have happened that day.

The original forecast included a large-scale cold front, which would have led to temperature drops and stronger — but not extreme — winds, with only a low-level wind advisory issued. The new study found the apparent temperature could have dropped as low as -10 degrees Celsius (14 degrees Fahrenheit), about 3 degrees Celsius cooler than what the original models predicted.

The model also generated an “impact forecast,” including apparent temperature, which could have dropped even lower as it considers humidity and would ideally include the effect of wet clothes or skin on body temperature. Including these in forecasts, Xue says, could help mitigate the risk of hypothermia.

Along with the weather, planning for the race and gear requirements for the runners were discussed following the event. Many endurance events require ample layers for warmth and rain protection; these were suggested but not required, which could have contributed to the loss of life. Both accurate weather forecasts and gear requirements are essential for an event to be safe.

Some exoplanets found thus far may be too old to support temperate, Earth-like climates

Tyler O'Neal, Staff Editor EARTH SCIENCES

As the scientific community searches for worlds orbiting nearby stars that could potentially harbor life, new Southwest Research Institute-led research suggests that younger rocky exoplanets are more likely to support temperate, Earth-like climates. Courtesy of NASA/JPL-Caltech An SwRI-led study suggests that host-star age and radionuclide abundance will help determine both an exoplanet’s history and its current likelihood of being temperate today. For example, the red dwarf star TRAPPIST-1 is home to the largest group of roughly Earth-sized planets ever found in a single stellar system with seven rocky siblings including four in the habitable zone. But at around 8 billion years old, these worlds are roughly 2 billion years older than the most optimistic degassing lifetime predicted by this study and unlikely to support a temperate climate today.

In the past, scientists have focused on planets situated within a star’s habitable zone, where it is neither too hot nor too cold for liquid surface water to exist. However, even within this so-called “Goldilocks zone,” planets can still develop climates inhospitable to life. Sustaining temperate climates also requires a planet have sufficient heat to power a planetary-scale carbon cycle. A key source of this energy is the decay of the radioactive isotopes of uranium, thorium, and potassium. This critical heat source can power a rocky exoplanet’s mantle convection, a slow creeping motion of the region between a planet’s core and a crust that eventually melts at the surface. Surface volcanic degassing is a primary source of CO2 to the atmosphere, which helps keep a planet warm. Without mantle degassing, planets are unlikely to support temperate, habitable climates like the Earth’s.

“We know these radioactive elements are necessary to regulate climate, but we don’t know how long these elements can do this, because they decay over time,” said Dr. Cayman Unterborn, lead author of an Astrophysical Journal Letters paper about the research. “Also, radioactive elements aren’t distributed evenly throughout the Galaxy, and as planets age, they can run out of heat, and degassing will cease. Because planets can have more or less of these elements than the Earth, we wanted to understand how this variation might affect just how long rocky exoplanets can support temperate, Earth-like climates.”

Studying exoplanets is challenging. Today’s technology cannot measure the composition of an exoplanet’s surface, much less that of its interior. Scientists can, however, measure the abundance of elements in a star spectroscopically by studying how light interacts with the elements in a star’s upper layers. Using these data, scientists can infer what a star’s orbiting planets are made of using the stellar composition as a rough proxy for its planets.

“Using host stars to estimate the amount of these elements that would go into planets throughout the history of the Milky Way, we calculated how long we can expect planets to have enough volcanism to support a temperate climate before running out of power,” Unterborn said. “Under the most pessimistic conditions, we estimate that this critical age is only around 2 billion years old for an Earth-mass planet and reaching 5–6 billion years for higher-mass planets under more optimistic conditions. For the few planets we do have ages for, we found only a few were young enough for us to confidently say they can have surface degassing of carbon today when we’d observe it with, say, the James Webb Space Telescope.”

This research combined direct and indirect observational data with dynamical models to understand which parameters most affect an exoplanet’s ability to support a temperate climate. More laboratory experiments and computational modeling will quantify the reasonable range of these parameters, particularly in the era of the James Webb Space Telescope, which will provide a more in-depth characterization of individual targets. With the Webb telescope, it will be possible to measure the three-dimensional variation of exoplanet atmospheres. These measurements will deepen the knowledge of atmospheric processes and their interactions with the planet’s surface and interior, which will allow scientists to better estimate whether a rocky exoplanet in habitable zones is too old to be Earth-like.

“Exoplanets without active degassing are more likely to be cold, snowball planets,” Unterborn said. “While we can’t say the other planets aren’t degassing today, we can say that they would require special conditions to do so, such as having tidal heating or undergoing plate tectonics. This includes the high-profile rocky exoplanets discovered in the TRAPPIST-1 star system. Regardless, younger planets with temperate climates may be the simplest places to look for other Earths.”