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Shrinking Planets May Explain Why Hot Super-earths Exist

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vanishing gas giant

This artist’s concept shows giant clouds of hydrogen (blue) evaporating from the Neptune-sized exoplanet GJ 3470b as energetic charged particles from its host star beat down on the planet. The hydrogen is escaping the planet about 100 times faster than seen for any other similar alien world. (Credit: NASA/ESA/D. Player (STScI))

Astronomers have discovered a bizarre, Neptune-sized exoplanet located less than 100 light-years from Earth that’s shedding its atmosphere so quickly it may help researchers finally answer the long-standing question: Where did all the hot Neptunes go?

According to the new research, published December 13 in the journal Astronomy and Astrophysics, the shrinking world, named GJ 3470b, is rapidly losing its atmosphere as it’s bombarded by a steady stream of energetic charged particles from its red dwarf host.

The discovery — made with the help of NASA’s indefatigable Hubble Space Telescope — suggests that although Neptune-sized exoplanets can exist temporarily very near their host stars, they may not last very long. Instead, these planets could lose a significant fraction of their mass through evaporation driven by intense stellar winds. In the case of GJ 3470b, the researchers think strong winds from its active host star have stripped the planet of up to about 35 percent of its original mass over the course of its life.

“This is the first time a planet has been observed to lose its atmosphere so quickly that it can impact its evolution,” said lead author Vincent Bourrier, an astronomer from the University of Geneva (UNIGE), in a press release.

An Oasis in the Desert

Based on our own solar system, astronomers typically break down planets into three broad categories: rocky terrestrial planets (like Earth and Mars), massive gas giants (like Jupiter and Saturn), and freezing ice giants (like Uranus and Neptune). But over the years, researchers have discovered a multitude of exoplanets around other stars that seem to break these familiar molds.

In particular, since the first confirmed exoplanet was discovered just a few decades ago, researchers have uncovered a surprising number of giant planets, dubbed hot Jupiters, located extremely close to their host stars. On the other end of the spectrum, astronomers have discovered a plethora of hot super-Earths, which are a few times the mass of the Earth, that sit very near their stars. However, astronomers very rarely find medium-sized planets (or hot Neptunes) in similar close-in orbits.

But why does this void of hot, mid-sized planets — the so-called “hot Neptune desert” — exist?

hot neptune desert

This graphic plots known exoplanets based on both their size and their distance from their host stars. Hot Jupiters are in the upper left, while super-Earths are in the lower left. As shown, very few mid-size planets, or hot Neptunes, have been found orbiting very near their host stars. (For reference, the solar system’s innermost planet, Mercury, orbits the sun at an average distance of about 36 million miles.) (Credit: NASA/ESA/A. Feild (STScI))

“Until now, we were not sure of the role played by the evaporation of atmospheres in the formation of the desert,” said Bourrier. But based on this new finding, hot Neptunes may have withered away into mini-Neptunes (an alternative term for hefty super-Earths), or even eroded straight down to their rocky cores. “This could explain the abundance of hot super-Earths that have been discovered,” said co-author David Ehrenreich, an astronomer at UNIGE.

By showing that an active star can strip loads of mass from a mid-sized planet near the edge of the hot Neptune desert, the researchers think they’ve finally figured out why so few hot Neptunes have been discovered, while heaps of smaller planets, called super-Earths, have been found in the same boiling neighborhood.

“This is the smoking gun that planets can lose a significant fraction of their entire mass,” said co-author David Sing, a professor at Johns Hopkins University, in a statement. “GJ 3470b is losing more of its mass than any other planet we [have] seen so far; in only a few billion years from now, half of the planet may be gone.” And if GJ 3470b loses half its mass (it’s currently about 14 Earth masses), it will make the transition from hot Neptune to super-Earth.

Exploring the Desert

GJ 3470b, which sits about 10 times closer to its host star than Mercury is to the sun, is not the first evaporating Neptune-sized planet ever found. In fact, just a few years ago, astronomers found a similar planet named GJ 436b that is losing its atmosphere just like GJ3470b, albeit at a much slower rate (about 100 times slower). To analyze the mass loss of both these planets, the researchers tracked the hydrogen that was escaping from their atmospheres.

However, astronomers cannot easily detect hydrogen from more than about 150 light-years away. This is because the hydrogen signals they are looking for fall in a wavelength range that is blocked by interstellar gas, which permeates the space between stars. But fortunately, the researchers have a plan to seek out more distant shrinking hot Neptunes in the future.

“Helium will expand the range of our surveys,” said Bourrier, “the high sensitivity of the James Webb Space Telescope should allow us to detect helium escaping small planets, such as mini-Neptunes, and complete our observations of the edge of the desert.”

So, for now, we’ll have to be satisfied with just a few known examples of shrinking hot Neptunes. But keep in mind, many more may lurk just beyond the horizon.

 

[This article originally appeared on Astronomy.com]

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Ecology

Globe Climate: Canada’s resource reckoning is coming

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Good afternoon, and welcome to Globe Climate, a newsletter about climate change, environment and resources in Canada.

This afternoon, the Alberta government announced that it is restoring a coal mining policy it revoked last spring. At the time, the move provoked a widespread public backlash detailed by The Globe. The original decision, which opened up more than 1.4 million hectares to exploration, was made without public consultation. Premier Jason Kenney previously defended the changes.

Lots more on coal and Canada’s resources industry in this week’s newsletter edition.

Now, let’s catch you up on other news.

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Ecology

‘Incredibly destructive’: Canada’s Prairies to see devastating impact of climate change

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As the climate continues to warm at an alarming rate, experts warn if dramatic steps to mitigate global warming are not taken, the effects in Canada’s Prairie region will be devastating to the country’s agriculture sector.

According to Environment and Climate Change Canada, the country is warming, on average, about double the global rate.

Scientists with the National Oceanic and Atmospheric Administration in the U.S. recently found 2020 was earth’s second-hottest year on record, with the average land and ocean surface temperature across the globe at 0.98 of a degree C above the 20th-century average.

However, the agency found the northern hemisphere saw its hottest year on record, at 1.28 degrees C above the average.

“(In Canada) we are looking at about 6.4C degrees of warming this century, which isn’t much less than one degree per decade, which is just a terrifying rate of warming,” Darrin Qualman, the director of climate crisis policy and action at the National Farmer’s Union said.

Qualman said there is “massive change coming” to Canada’s Prairies, which will be “incredibly destructive.”

“It’s not going too far to say that if we made that happen, parts of the Prairies wouldn’t be farmable anymore,” he said.

According to the federal government, in 2018 Canada’s agriculture and agri-food system generated $143 billion, accounting for 7.4 per cent of the country’s GDP.

The sector employed 2.3 million people in 2018. The majority of the 64.2 million hectares of farmland in Canada is concentrated in the Prairies and in southern Ontario.

The effects of climate change are already being felt on the ground in the Prairies, Qualman said, adding that the NFU has already heard from farmers complaining of “challenging weather.”

“People are sharing pictures of flattened crops and buildings, et cetera, that have been damaged,” he said. “And we’re still at the beginning of this.”

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Ecology

Insect-based dog food aims to cut your pet’s carbon pawprint

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Meat has an enormous carbon footprint, with livestock liable for about 15 per cent of worldwide emissions, as we have beforehand mentioned on this e-newsletter. That is prompted specialists to suggest consuming much less meat for sustainability (and well being) causes.

However what about your pet? One research discovered that the methane and nitrous oxide emissions generated by canine and cat meals within the U.S. alone had been equal to about 64 million tonnes of CO2, or roughly the quantity produced by 13.6 million automobiles. And it might be getting worse, with a development towards feeding pets “human-grade” meat.

That is prompted some pet meals makers to look to lower-carbon protein sources — together with bugs.

Research present that producing insect-based meals requires far much less feed, land and water and generates far fewer greenhouse fuel emissions per kilogram than meats comparable to beef, pork or rooster.

That is one of many causes increasingly more pet meals containing insect protein are hitting the market. Purina, a model owned by multinational Nestlé, launched a line of canine and cat meals containing black soldier fly larvae in Switzerland in November.

In Canada, Montreal-based Wilder Harrier began promoting canine treats made with cricket protein in 2015 and pet food made with black soldier fly larvae in 2019. It plans to broaden to launch a line of insect-based cat treats later this yr and cat meals in 2022 due to “a ton of demand,” mentioned firm co-founder Philippe Poirier.

Wilder Harrier initially labored with animal nutritionists on insect-based merchandise to unravel a unique downside — specifically, the founders’ canines had allergy symptoms to frequent meats utilized in canine meals. Poirier mentioned now about half its prospects hunt down the product due to their pets’ allergy symptoms and about half for environmental causes.

Dr. Cailin Heinze, a U.S.-based veterinary nutritionist licensed by the American School of Veterinary Vitamin, has written concerning the environmental influence of pet meals. She mentioned we’re typically “not as involved as we probably ought to [be]” concerning the environmental footprint of pets.

Alternatively, she famous that the longer-term influence of newer diets, comparable to vegan meals and people containing bugs, hasn’t been nicely examined in comparison with conventional pet meals.

Maria Cattai de Godoy, an assistant professor of animal sciences on the College of Illinois who research novel proteins for pet meals (together with bugs, yeast and plant-based substances), mentioned such substances are rigorously examined to find out their security and diet earlier than being added to pet meals. 

“This can be a very extremely regulated trade,” she mentioned, however admitted it is also evolving.

Relating to bugs, she mentioned constructive information “reveals promise in direction of utilizing them increasingly more in pet meals.” Insect-based proteins have additionally earned the endorsement of the British Veterinary Affiliation, which says some insect-based meals could also be higher for pets than prime steak.

However Godoy famous that there isn’t any one-size-fits-all resolution, and pet homeowners ought to take into consideration the wants of their very own particular person pet and analysis whether or not a specific weight loss plan can be appropriate.

She mentioned that other than the kind of protein, issues like packaging and manufacturing strategies may also make a distinction. For instance, utilizing meat byproducts that may in any other case turn into waste would not drive elevated meat manufacturing the identical approach as utilizing human-grade meat.

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