Secrets of a Hot Saturn and its Spotted Star Unlocked by McGill, Université de Montréal Astronomers | Canada News Media
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Secrets of a Hot Saturn and its Spotted Star Unlocked by McGill, Université de Montréal Astronomers

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Exoplanets, planets located beyond our Solar System, captivate both scientists and the public, holding the promise of unveiling diverse planetary systems and potentially habitable worlds. Despite being very much not like our Earth, large gas giant planets found very close to their stars have proven to be ideal test targets for telescopes like the James Webb Space Telescope (JWST) to refine astronomers’ methods of understanding exoplanets. One such planet is HAT-P-18 b, a “hot Saturn” type planet located over 500 light-years away with a mass similar to Saturn’s but a size closer to that of the larger Jupiter. This gives the exoplanet a puffed-up atmosphere that is especially ideal for analysis.

Led by researchers from the Trottier Institute for Research on Exoplanets at McGill University and the Université de Montréal (UdeM), a team of astronomers harnessed the power of the revolutionary Webb Telescope to study HAT-P-18 b. Their findings, detailed in the journal Monthly Notices of the Royal Astronomical Society (MNRAS), provide a comprehensive portrait of the hot Saturn’s atmosphere while delving into the complexities of distinguishing atmospheric signals from stellar activity.

“The James Webb Space Telescope provides exoplanet observations so precise that we are limited by our understanding of their host stars. Fortunately, those same data- especially with the made-in-Canada NIRISS instrument- allow us to measure what the star is doing during our observations and correct for it, so we can figure out exactly what is in these planets’ atmospheres,” said Nicolas Cowan, Professor in McGill University’s Department of Earth and Planetary Sciences.

Passing over a spotted star

Observations from the Webb Telescope were taken while the exoplanet HAT-P-18 b was passing in front of its Sun-like star. This moment is called a transit and is crucial to detect and further characterise an exoplanet from hundreds of light-years away with surprising precision. Astronomers are not observing light that is being emitted directly by the distant planet. Rather, they are studying how the central star’s light is being blocked and affected by the planet orbiting it.

The light curve shows the luminosity or brightness of the star over time. When the exoplanet passes over the star, known as a transit, part of the star’s light is blocked by the exoplanet. As a result, the star’s luminosity decreases. When a star spot is occulted on the star’s surface, or when the exoplanet passes over the dark spot, astronomers can see a signal in the light curve in the form of a small bump in the bottom of the transit light curve. See the full animation of this infographic here. (Credit: B. Gougeon/Université de Montréal)

Exoplanet hunters must thus grapple with the challenge of disentangling signals caused by the presence of the planet and those caused by the star’s own properties. Just like our Sun, stars do not have uniform surfaces. They can have dark star spots and bright regions, which can create signals that mimic a planet’s atmospheric attributes. A recent study of the exoplanet TRAPPIST-1 b and its star TRAPPIST-1 led by UdeM Ph.D. student Olivia Lim witnessed an eruption, or flare, on the surface of the star, which affected their observations.

In the case of planet HAT-P-18 b, Webb caught the exoplanet right as it was passing over a dark spot on its star, HAT-P-18. This is called a spot-crossing event, and its effect was evident in the data collected for the study. The team also reported the presence of numerous other star spots on HAT-P-18’s surface which were not blocked out by the exoplanet. To accurately determine the exoplanet’s atmospheric composition, the researchers determined it was necessary to simultaneously model the planetary atmosphere as well as the star’s peculiarities. They state that such consideration will be crucial in treating future exoplanet observations from the JWST to fully harness their potential.

H2O, CO2, and clouds in a scorching atmosphere

Following their careful modelling of both the exoplanet and the star in the HAT-P-18 system, the team of astronomers then performed a meticulous dissection of HAT-P-18 b’s atmospheric composition. By inspecting the light that filters through the exoplanet’s atmosphere as it transits its host star, the researchers discerned the presence of water vapour (H2O) and carbon dioxide (CO2). The researchers also detected the possible presence of sodium. Adding intrigue to the findings, the team observed strong signs of a cloud deck in HAT-P-18 b’s atmosphere, which appears to be muting the signals of many of the molecules found within it. They also concluded that the star’s surface was covered by many dark spots that can significantly influence the interpretation of the data.

An earlier analysis of the same JWST data led by a team at Johns Hopkins University had also revealed a clear detection of water and CO2, but also reported the detection of small particles at high-altitudes called hazes and found hints of methane (CH4). The work from the Université de Montréal astronomers, which was the first time the characteristics of the star’s surface were taken into consideration with the planet’s atmosphere, revealed a different picture. The CH4 detection was not confirmed, and the water abundance they determined was ten times lower than previously found. They also found that the previous study’s detection of hazes could instead be caused by star spots on the star’s surface, highlighting the importance of considering the star in the analysis.

While molecules like water, carbon dioxide, and methane can be interpreted as biosignatures, or signs of life, in certain ratios or in combination with other molecules, HAT-P-18 b’s scorching temperatures of close to 600 degrees Celsius do not bode well for the planet’s habitability.

The data used from the JWST in this study were collected by the Canadian-made NIRISS (Near-Infrared Imager and Slitless Spectrograph) instrument, which has provided astronomers with the unparalleled ability to differentiate many of HAT-P-18 b’s atmospheric characteristics from one another. The results show that observations taken on the far-visible to near-infrared within the NIRISS instrument’s wavelength range are essential to disentangle the signals from the planetary atmosphere and the star. Future observations from another JWST instrument, the Near Infrared Spectrograph (NIRSpec), would help refine the team’s results, such as the CO2 detection, and shed even more light on the intricacies of this hot Saturn exoplanet.

About this study

The paper “Near-Infrared Transmission Spectroscopy of HAT-P-18 b with NIRISS: Disentangling Planetary and Stellar Features in the Era of JWST” was published in Monthly Notices of the Royal Astronomical Society. The lead authors are Marylou Fournier Tondreau, previously an M.Sc. student at the Trottier Institute for Research on Exoplanets at the Université de Montréal (UdeM) and now a Ph.D. student at the University of Oxford, Ryan J. MacDonald, Fellow at the University of Michigan, and Michael Radica, Ph.D. student at UdeM. Other iREx researchers that contributed to this paper are David Lafrenière (UdeM), Caroline Piaulet (UdeM), Louis-Philippe Coulombe (UdeM), Romain Allart (UdeM), Kim Morel (UdeM), Étienne Artigau (UdeM), Loïc Albert (UdeM), Olivia Lim (UdeM), René Doyon (UdeM), Björn Benneke (UdeM), Jason Rowe (Bishop’s U), Antoine Darveau-Bernier (UdeM), Nicolas Cowan (McGill), Neil Cook (UdeM), Frédéric Genest (UdeM), Stefan Pelletier (UdeM), Lisa Dang (UdeM), and Jake Taylor (UdeM and the University of Oxford). Additional contributors are based out of the Arizona State University, Cornell University, the University of Victoria, and the National Research Council of Canada’s Herzberg Astronomy and Astrophysics Research Centre.

 

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Here’s how Helene and other storms dumped a whopping 40 trillion gallons of rain on the South

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More than 40 trillion gallons of rain drenched the Southeast United States in the last week from Hurricane Helene and a run-of-the-mill rainstorm that sloshed in ahead of it — an unheard of amount of water that has stunned experts.

That’s enough to fill the Dallas Cowboys’ stadium 51,000 times, or Lake Tahoe just once. If it was concentrated just on the state of North Carolina that much water would be 3.5 feet deep (more than 1 meter). It’s enough to fill more than 60 million Olympic-size swimming pools.

“That’s an astronomical amount of precipitation,” said Ed Clark, head of the National Oceanic and Atmospheric Administration’s National Water Center in Tuscaloosa, Alabama. “I have not seen something in my 25 years of working at the weather service that is this geographically large of an extent and the sheer volume of water that fell from the sky.”

The flood damage from the rain is apocalyptic, meteorologists said. More than 100 people are dead, according to officials.

Private meteorologist Ryan Maue, a former NOAA chief scientist, calculated the amount of rain, using precipitation measurements made in 2.5-mile-by-2.5 mile grids as measured by satellites and ground observations. He came up with 40 trillion gallons through Sunday for the eastern United States, with 20 trillion gallons of that hitting just Georgia, Tennessee, the Carolinas and Florida from Hurricane Helene.

Clark did the calculations independently and said the 40 trillion gallon figure (151 trillion liters) is about right and, if anything, conservative. Maue said maybe 1 to 2 trillion more gallons of rain had fallen, much if it in Virginia, since his calculations.

Clark, who spends much of his work on issues of shrinking western water supplies, said to put the amount of rain in perspective, it’s more than twice the combined amount of water stored by two key Colorado River basin reservoirs: Lake Powell and Lake Mead.

Several meteorologists said this was a combination of two, maybe three storm systems. Before Helene struck, rain had fallen heavily for days because a low pressure system had “cut off” from the jet stream — which moves weather systems along west to east — and stalled over the Southeast. That funneled plenty of warm water from the Gulf of Mexico. And a storm that fell just short of named status parked along North Carolina’s Atlantic coast, dumping as much as 20 inches of rain, said North Carolina state climatologist Kathie Dello.

Then add Helene, one of the largest storms in the last couple decades and one that held plenty of rain because it was young and moved fast before it hit the Appalachians, said University of Albany hurricane expert Kristen Corbosiero.

“It was not just a perfect storm, but it was a combination of multiple storms that that led to the enormous amount of rain,” Maue said. “That collected at high elevation, we’re talking 3,000 to 6000 feet. And when you drop trillions of gallons on a mountain, that has to go down.”

The fact that these storms hit the mountains made everything worse, and not just because of runoff. The interaction between the mountains and the storm systems wrings more moisture out of the air, Clark, Maue and Corbosiero said.

North Carolina weather officials said their top measurement total was 31.33 inches in the tiny town of Busick. Mount Mitchell also got more than 2 feet of rainfall.

Before 2017’s Hurricane Harvey, “I said to our colleagues, you know, I never thought in my career that we would measure rainfall in feet,” Clark said. “And after Harvey, Florence, the more isolated events in eastern Kentucky, portions of South Dakota. We’re seeing events year in and year out where we are measuring rainfall in feet.”

Storms are getting wetter as the climate change s, said Corbosiero and Dello. A basic law of physics says the air holds nearly 4% more moisture for every degree Fahrenheit warmer (7% for every degree Celsius) and the world has warmed more than 2 degrees (1.2 degrees Celsius) since pre-industrial times.

Corbosiero said meteorologists are vigorously debating how much of Helene is due to worsening climate change and how much is random.

For Dello, the “fingerprints of climate change” were clear.

“We’ve seen tropical storm impacts in western North Carolina. But these storms are wetter and these storms are warmer. And there would have been a time when a tropical storm would have been heading toward North Carolina and would have caused some rain and some damage, but not apocalyptic destruction. ”

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Follow AP’s climate coverage at https://apnews.com/hub/climate

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Follow Seth Borenstein on Twitter at @borenbears

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Associated Press climate and environmental coverage receives support from several private foundations. See more about AP’s climate initiative here. The AP is solely responsible for all content.

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‘Big Sam’: Paleontologists unearth giant skull of Pachyrhinosaurus in Alberta

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It’s a dinosaur that roamed Alberta’s badlands more than 70 million years ago, sporting a big, bumpy, bony head the size of a baby elephant.

On Wednesday, paleontologists near Grande Prairie pulled its 272-kilogram skull from the ground.

They call it “Big Sam.”

The adult Pachyrhinosaurus is the second plant-eating dinosaur to be unearthed from a dense bonebed belonging to a herd that died together on the edge of a valley that now sits 450 kilometres northwest of Edmonton.

It didn’t die alone.

“We have hundreds of juvenile bones in the bonebed, so we know that there are many babies and some adults among all of the big adults,” Emily Bamforth, a paleontologist with the nearby Philip J. Currie Dinosaur Museum, said in an interview on the way to the dig site.

She described the horned Pachyrhinosaurus as “the smaller, older cousin of the triceratops.”

“This species of dinosaur is endemic to the Grand Prairie area, so it’s found here and nowhere else in the world. They are … kind of about the size of an Indian elephant and a rhino,” she added.

The head alone, she said, is about the size of a baby elephant.

The discovery was a long time coming.

The bonebed was first discovered by a high school teacher out for a walk about 50 years ago. It took the teacher a decade to get anyone from southern Alberta to come to take a look.

“At the time, sort of in the ’70s and ’80s, paleontology in northern Alberta was virtually unknown,” said Bamforth.

When paleontogists eventually got to the site, Bamforth said, they learned “it’s actually one of the densest dinosaur bonebeds in North America.”

“It contains about 100 to 300 bones per square metre,” she said.

Paleontologists have been at the site sporadically ever since, combing through bones belonging to turtles, dinosaurs and lizards. Sixteen years ago, they discovered a large skull of an approximately 30-year-old Pachyrhinosaurus, which is now at the museum.

About a year ago, they found the second adult: Big Sam.

Bamforth said both dinosaurs are believed to have been the elders in the herd.

“Their distinguishing feature is that, instead of having a horn on their nose like a triceratops, they had this big, bony bump called a boss. And they have big, bony bumps over their eyes as well,” she said.

“It makes them look a little strange. It’s the one dinosaur that if you find it, it’s the only possible thing it can be.”

The genders of the two adults are unknown.

Bamforth said the extraction was difficult because Big Sam was intertwined in a cluster of about 300 other bones.

The skull was found upside down, “as if the animal was lying on its back,” but was well preserved, she said.

She said the excavation process involved putting plaster on the skull and wooden planks around if for stability. From there, it was lifted out — very carefully — with a crane, and was to be shipped on a trolley to the museum for study.

“I have extracted skulls in the past. This is probably the biggest one I’ve ever done though,” said Bamforth.

“It’s pretty exciting.”

This report by The Canadian Press was first published Sept. 25, 2024.

The Canadian Press. All rights reserved.

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The ancient jar smashed by a 4-year-old is back on display at an Israeli museum after repair

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TEL AVIV, Israel (AP) — A rare Bronze-Era jar accidentally smashed by a 4-year-old visiting a museum was back on display Wednesday after restoration experts were able to carefully piece the artifact back together.

Last month, a family from northern Israel was visiting the museum when their youngest son tipped over the jar, which smashed into pieces.

Alex Geller, the boy’s father, said his son — the youngest of three — is exceptionally curious, and that the moment he heard the crash, “please let that not be my child” was the first thought that raced through his head.

The jar has been on display at the Hecht Museum in Haifa for 35 years. It was one of the only containers of its size and from that period still complete when it was discovered.

The Bronze Age jar is one of many artifacts exhibited out in the open, part of the Hecht Museum’s vision of letting visitors explore history without glass barriers, said Inbal Rivlin, the director of the museum, which is associated with Haifa University in northern Israel.

It was likely used to hold wine or oil, and dates back to between 2200 and 1500 B.C.

Rivlin and the museum decided to turn the moment, which captured international attention, into a teaching moment, inviting the Geller family back for a special visit and hands-on activity to illustrate the restoration process.

Rivlin added that the incident provided a welcome distraction from the ongoing war in Gaza. “Well, he’s just a kid. So I think that somehow it touches the heart of the people in Israel and around the world,“ said Rivlin.

Roee Shafir, a restoration expert at the museum, said the repairs would be fairly simple, as the pieces were from a single, complete jar. Archaeologists often face the more daunting task of sifting through piles of shards from multiple objects and trying to piece them together.

Experts used 3D technology, hi-resolution videos, and special glue to painstakingly reconstruct the large jar.

Less than two weeks after it broke, the jar went back on display at the museum. The gluing process left small hairline cracks, and a few pieces are missing, but the jar’s impressive size remains.

The only noticeable difference in the exhibit was a new sign reading “please don’t touch.”

The Canadian Press. All rights reserved.

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