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A scorching-hot exoplanet scrutinized by UdeM astronomers

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image: The ultra-hot giant exoplanet WASP-76 b, depicted here, is an extremely hot world orbiting very close to its giant star.
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Credit: International Gemini Observatory/NOIRLab/NSF/AURA/J. da Silva/Spaceengine/M. Zamani

An international team led by Stefan Pelletier, a Ph.D. student at Université de Montréal’s Trottier Institute for Research on Exoplanets announced today having made a detailed study of the extremely hot giant exoplanet WASP-76 b.

Using the MAROON-X instrument on the Gemini-North Telescope, the team was able to identify and measure the abundance of 11 chemical elements in the atmosphere of the planet.

Those include rock-forming elements whose abundances are not even known for giant planets in the Solar System such as Jupiter or Saturn. The team’s study is published in the journal Nature.

“Truly rare are the times when an exoplanet hundreds of light years away can teach us something that would otherwise likely be impossible to know about our own Solar System,” said Pelletier. “This is the case with this study.”

A big, hot, strange world

WASP-76 b is a strange world. It reaches extreme temperatures because it is very close to its parent star, a massive star 634 light-years away in the constellation of Pisces: approximately 12 times closer than Mercury is to the Sun. With a mass similar to that of Jupiter, but almost six times bigger by volume, it is quite “puffy”.

Since its discovery by the Wide Angle Search for Planets (WASP) program in 2013, many teams have studied it and identified various elements in its atmosphere. Notably, in a study also published in Nature in March 2020, a team found an iron signature and hypothesised that there could be iron rain on the planet.

Aware of these studies, Pelletier became motivated to obtain new, independent observations of WASP-76 b using the MAROON-X high-resolution optical spectrograph on the Gemini-North 8-metre Telescope in Hawai’i, part of the International Gemini Observatory, operated by NSF’s NOIRLab.

“We recognized that the powerful new MAROON-X spectrograph would enable us to study the chemical composition of WASP-76 b with a level of detail unprecedented for any giant planet,” says UdeM astronomy professor Björn Benneke, co-author of the study and Stefan Pelletier’s PhD research supervisor.

A composition similar to the Sun’s

Within the Sun, the abundances of almost all elements in the periodic table are known with great accuracy. In the giant planets in our Solar System, however, that’s true for only a handful of elements, whose compositions remain poorly constrained. And this has hampered understanding of the mechanisms governing the formation of these planets.

As it is so close to its star, WASP-76 b has a temperature well above 2000°C. At these degrees, many elements that would normally form rocks here on Earth (like magnesium and iron) are vaporised and present in gaseous form in the upper atmosphere. Studying this peculiar planet enables unprecedented insight into the presence and abundance of rock-forming elements in giant planets, since in colder giant planets like Jupiter these elements are lower in the atmosphere and impossible to detect.

The abundance of many elements measured by Pelletier and his team in the exoplanet’s atmosphere – such as manganese, chromium, magnesium, vanadium, barium and calcium – matches those of its host star as well as of our own Sun very closely.

These abundances are not random: they are the direct product of the Big Bang, followed by billions of years of stellar nucleosynthesis, so scientists measure roughly the same composition in all stars. It is, however, different from the composition of rocky planets like Earth, which are formed in a more complex manner.

The results of this new study indicate that giant planets could maintain an overall composition that reflects that of the protoplanetary disc from which they formed.

Depletion of other elements very interesting

However, other elements were depleted in the planet compared to the star – a result Pelletier found particularly interesting.

“These elements that appear to be missing in WASP-76 b’s atmosphere are precisely those that require higher temperatures to vaporise, like titanium and aluminium, ” he said. “Meanwhile, the ones that matched our predictions, like manganese, vanadium, or calcium, all vaporise at slightly lower temperatures.”

The discovery team’s interpretation is that the observed composition of the upper atmospheres of giant planets can be extremely sensitive to temperature. Depending on an element’s temperature of condensation, it will be in gas form and present in the upper part of the atmosphere, or condense into liquid form where it will sink to deeper layers. When in gas form, it plays an important role in absorbing light and can be seen in astronomers’ observations. When condensed, it cannot be detected by astronomers and becomes completely absent from their observations.

“If confirmed, this finding would mean that two giant exoplanets that have slightly different temperatures from one another could have very different atmospheres, “ said Pelletier. “Kind of like two pots of water, one at -1°C that is frozen, and one that is at +1°C that is liquid. For example, calcium is observed on WASP-76 b, but it may not be on a slightly colder planet.”

First detection of vanadium oxide

Another interesting finding by Pelletier’s team is the detection of a molecule called  vanadium oxide. This is the first time it has been unambiguously detected on an exoplanet, and is of great interest to astronomers because they know it can have a big impact on hot giant planets.

“This molecule plays a similar role to ozone in Earth’s atmosphere: it is extremely efficient at heating up the upper atmosphere,” explained Pelletier. “This causes the temperatures to increase as a function of altitude, instead of decreasing as is typically seen on colder planets.”

One element, nickel, is clearly more abundant in the exoplanet’s atmosphere than what the astronomers were expecting. Many hypotheses could explain that; one is  that WASP-76 b could have accreted material from a planet similar to Mercury. In our Solar System, the small rocky planet is enriched with metals like nickel because of how it was formed.

Pelletier’s team also found that the asymmetry in iron absorption between the east and west hemispheres of WASP-76 b reported in previous studies is similarly present for many other elements. This means the underlying phenomenon causing this is thus probably a global process such as a difference in temperature or clouds being present on one side of the planet but not the other, rather than being the result of condensation into liquid form as was previously suggested.

Confirming and leveraging lessons learned

Pelletier and his team are very keen to learn more about this exoplanet and other ultra-hot giant planets, in part to confirm their hypothesis about the vastly different atmospheres that could prevail on planets differing slightly in temperature.

They also hope other researchers will leverage what they learned from this giant exoplanet and apply it to better our understanding of our own Solar System planets and how they came to be.

“Generations of researchers have used Jupiter, Saturn, Uranus, and Neptune’s measured abundances for hydrogen and helium to benchmark formation theories of gaseous planets,” said Benneke. “Likewise, the measurements of heavier elements such as calcium or magnesium on WASP-76 b will help further understanding the formation of gaseous planets.

About this study

“Vanadium oxide and a sharp onset of cold-trapping on a giant exoplanet,” by Stefan Pelletier et al., was published June 14, 2023 in Nature. In addition to Pelletier and Björn Benneke,  the team also includes: Luc Bazinet and Olivia Lim, two graduate students at Université de Montréal’s Trottier Institute for Research on Exoplanets (iREx); Mohamad Ali-Dib, a former Trottier postdoctoral fellow at iREx, now at NYU Abu Dhabi; and 13 other co-authors from Canada, the United Arab Emirates, Sweden, France, the United Kingdom, the United States, Italy, the Netherlands and Germany.


 

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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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