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Our Solar System’s Formation Was A Lot Messier Than You Think

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planets superimposed on each other

The early solar system was a violent place: it wasn’t just asteroids, but whole planets that veered on strange courses. (Photo credit: NASA)

When most of us learn about the solar system, it seems like a pretty well-ordered place. Our sun formed first, about five billion years ago, and the planets appeared a little later. As a very general trend, these planets grew larger and less dense the farther from the sun they formed.  

But this story leaves out the chaotic dynamics and frenetic reshuffling that occurred when our solar system was young. Nature may like order eventually, but that order evolves out of pure chance. Our solar system may be settled down now, but in its youth, it was a wild place.

Creating Order Out of Chaos

cloud of gas with planets

The planets formed out of an initial disk of gas and dust. (Credit: NASA)

The basic story does sound ordered. Any star system begins as a vast disk of gas with a baby star forming in the center. The star absorbs the vast majority of the material in this disk, but there’s some left over. Those remnants coalesces into dust grains, which become pebbles, which become boulders and eventually planets. Meanwhile, the young star is turning on and starting to shine, creating a solar wind that starts to blow out the leftover gas. Only heavy materials are left near the star, leading to small, dense planets close by. Physics also tells us these closer planets have smaller orbits, limiting the amount of material they can encounter and nab with their growing gravitational bulk. Farther out, gas giants can form, sucking in large amounts of hydrogen and helium gas. And beyond that, you find the snow line, where ices can exist without being melted or baked away by the sun’s heat. These get incorporated into the ice giants.

That sounds very tidy and quaint, a cosmic “just-so story”, if you will. But the solar system is more messy and more complex than that. There’s the Kuiper Belt and Oort Cloud for example, swaths of detritus that aren’t collected into any one object. Mars is suspiciously tiny, and why is there an asteroid belt in the middle of the solar system anyway?

We also know that Earth was struck by some monstrous object in its early history, though where it came from is still a mystery. In any case, that planet-sized impactor gave us a moon — which turns out to be helpful in all kinds of ways. But it certainly wasn’t destined to be that way.

Planets Don’t Stay in One Place

solar system, with clouds of asteroids leading and trailing Jupiter

Jupiter still has a lot of sway in the solar system, with entire families of asteroids called Greeks and Trojans under its gravitational influence. (Credit: Roen Kelly)

Remember that Nature starts most chains of events pretty randomly. So sometimes planets will form on orbits that aren’t stable over the countless millennia of the planets’ lifetimes. Occasionally that instability means planets crash into each other. More often, it means they veer cosmically close — not colliding, but close enough for gravity and momentum to send them careening off on strange orbits. We use this “slingshot effect” all the time with spacecraft to great benefit, but random encounters result in random slingshotting. Sometimes planets may fling themselves out of the solar system entirely — like the Mars-sized object that collided with Earth to form our moon, and now is nowhere to be found. Scientists have found a few of these rogue planets, unattached to any identifiable star, drifting in the cosmos.

And our moon’s birth isn’t the only example of planets roving. Back when the solar system was young, our sun hadn’t yet blown away all the extra gas. Instead, it remained scattered throughout the planets, denser in some areas than others. Jupiter, cruising around the sun, interacted with these waves of gas and began to lose angular momentum and spiral in. As it migrated in toward the sun, it also nudged in closer to its inner neighbor, Mars, and sucked in material that by rights should have belonged to the Red Planet. This could explain why Mars somehow ended up with less material than Earth, despite having a bigger orbital path that therefore should have fed it richly enough to grow much larger. To get back where we see it in the modern era, Jupiter would then have had to reverse course, in a move researchers call a “grand tack” (as in a sailboat tacking to change direction). But why should a planet suddenly change directions?

Jupiter and Saturn still have a lot of sway in today’s solar system, thanks to their large bulks. Researchers think it’s possible that eons ago, as Jupiter spiraled in toward the sun, Saturn came chasing after. The two became locked in a resonance that spiraled them back out and cast an even stronger pull on the objects around them. Such a gravitational shove might have pushed Neptune farther out, which in turn scattered icy Kuiper Belt objects inwards. Jupiter then flung these objects all over, forming the Oort Cloud that still surrounds us.

Looking Farther From Home

planet trailing gas around a star

WASP-12b is another planet so hot it’s losing its atmosphere to its star. (Credit: ESA/Hubble)

It might help to look at these events from a more distant perspective. Since astronomers discovered the first planets outside our solar system a few decades ago, it’s been clear that other solar systems don’t look much like ours. Some of that is observational bias — it’s actually quite difficult to see planets as small as Earth orbiting as far from their star as we do from the sun.

But even the larger planets we do see look different. Astronomers have found numerous hot Jupiters, gas giants traveling on sizzling orbits close to their stars. They’ve discovered scores of super-Earths, sub-Neptune sized objects that appear to be the most common type of planet — and one that doesn’t exist in our home system. And with more systems to look at, they’ve noticed what there was evidence for in our own system the whole time: that planets often go roving.

Hot Jupiters have been confusing since astronomers first found them. It doesn’t make physical sense for a giant ball of gas to form next to a brilliantly hot star. The star will strip away that gas faster than the nascent planet’s gravity can pull it close. In fact, we can see this happening around some of the hottest exoplanets, like HD209458b. Astronomers can actually observe its atmosphere streaming away behind it, being boiled off.

Perhaps even more telling is WASP-17b, another hot Jupiter. This one orbits retrograde (backwards) to its host star, a sure sign that something wonky happened in its past, as planets can’t start out rotating the wrong way.

Astronomers also know that both of these planets are loners, like other hot Jupiters. This might have been our solar system’s fate, if Saturn hadn’t pulled Jupiter out of its downward spiral. Without that rescue mission, Jupiter might have herded the rest of the solar system into deep space. We don’t know if systems with hot Jupiters had more planets in their pasts, but we do know it would be unlikely for those hypothetical planets to survive a Jupiter-like planet’s sunward plunge.

Since we don’t have dashcam footage of the long-ago joyrides from our own solar system, it’s difficult for researchers to “prove” any of these scenarios. But the more we look at the universe around us, the more evidence we see for disrupted systems and roving planets, and the more we learn about how unique our own solar system’s history seems to be.

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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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