This article was originally published on The Conversation, an independent and nonprofit source of news, analysis and commentary from academic experts. Disclosure information is available on the original site.
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Author: Samantha Lawler, Assistant professor, Astronomy, University of Regina
Curious Kids is a series for children of all ages. Have a question you’d like an expert to answer? Send it to CuriousKidsCanadaâ†*theconversation.com.
Why does it matter if Pluto is a planet or a dwarf planet? Because for me it just makes it more confusing in our solar system. I know that some things in space are planets and some are stars and some are other names like moons or comets. Dwarf planet is a more different name and I think it just makes it more confusing. —
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Timmy, 11, Kitchener, Ont.
“Comet,” “star” and “planet” are category names that immediately tell you something important about what they describe.
Our solar system consists of the sun, planets (which orbit around the sun) and small bodies (which either orbit around the sun or planets). The “small bodies” category is divided up into even smaller categories, mostly depending on the shape and size of orbits.
In 1801, astronomers discovered Ceres, which was initially categorized as a “planet.” Astronomers measured that it was much smaller than the other known planets. Soon, a lot of smaller objects were discovered on orbits very close to Ceres. These small bodies were categorized as “asteroids” and we have since discovered hundreds of thousands of these in the asteroid belt.
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New discoveries
A similar process of discovery and re-categorization happened for small bodies further out in the solar system.
Pluto was discovered in 1930 and was called the ninth planet in our solar system for many decades. But astronomers soon learned that Pluto was pretty different from the other eight planets: it’s on a tilted orbit and it’s way, way smaller than the other planets.
Over the years, astronomers discovered more and more small, planet-like objects that crossed Pluto’s orbit. These are now categorized as “Kuiper Belt objects.” It was looking more and more like Pluto might fit in better with the category of Kuiper Belt objects than with planets.
In 2005, a new object was discovered in the outer solar system, Eris, that is even heavier than Pluto. This led astronomers to consider if both Eris and Pluto are planets or not. Astronomers thought this was an important enough decision that the International Astronomical Union voted on it in 2006. Astronomers decided that rather than demoting Pluto to a plain old Kuiper Belt object, they would make a new category of small body called a “dwarf planet.” Pluto and Eris would both be part of this new category.
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How planets form
Solar systems like ours form from big clouds of dust and gas that collapse into disks around young stars, but astronomers are still learning exactly how that process works. We use telescopes to look carefully at forming solar systems far away, but they are so far that it’s really hard to see the planets forming directly.
A planetesimal — a baby planet — first forms from clumps of dust in a disc orbiting a young star. Planetesimals then grab nearby pebbles, dust and sometimes even smaller planetesimals with their gravity, which gets stronger as they get bigger. When they get to be a few hundred kilometres across, they have enough gravity to pull themselves into a round shape, which is the definition of a dwarf planet.
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Measuring small bodies in our solar system, including dwarf planets, and comparing them with computer simulations is another way to see how our solar system formed. Our current theory is that there must have been a lot of dwarf planets that formed in our solar system.
Ceres, in the asteroid belt, and Pluto, Eris and about a dozen other Kuiper Belt objects are big enough to be in the dwarf planet category. This means that while they are planetesimals that grew big enough to be round, they did not develop a gravity strong enough to grab all the other planetesimals near their orbit.
Other solar systems
Astronomers have now measured more than 5,000 exoplanets, planets in other solar systems. We won’t be able to measure dwarf planets there for a very long time, but the ones we’ve found in our own solar system can teach us about how planets form everywhere.
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Hello, curious kids! Do you have a question you’d like an expert to answer? Ask an adult to send your question to CuriousKidsCanadaâ†*theconversation.com. Please tell us your name, age and the city where you live.
And since curiosity has no age limit — adults, let us know what you’re wondering, too. We won’t be able to answer every question, but we will do our best.
Samantha Lawler receives funding from the Natural Sciences and Engineering Research Council of Canada.
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This article is republished from The Conversation under a Creative Commons license. Disclosure information is available on the original site. Read the original article: https://theconversation.com/curious-kids-why-does-it-matter-if-pluto https://theconversation.com/curious-k
A University of Victoria micropaleontologist found that marine plankton may act as an early alert system before a mass extinction occurs.
With help from collaborators at the University of Bristol and Harvard, Andy Fraass’ newest paper in the Nature journal shows that after an analysis of fossil records showed that plankton community structures change before a mass extinction event.
“One of the major findings of the paper was how communities respond to climate events in the past depends on the previous climate,” Fraass said in a news release. “That means that we need to spend a lot more effort understanding recent communities, prior to industrialization. We need to work out what community structure looked like before human-caused climate change, and what has happened since, to do a better job at predicting what will happen in the future.”
According to the release, the fossil record is the most complete and extensive archive of biological changes available to science and by applying advanced computational analyses to the archive, researchers were able to detail the global community structure of the oceans dating back millions of years.
A key finding of the study was that during the “early eocene climatic optimum,” a geological era with sustained high global temperatures equivalent to today’s worst case global warming scenarios, marine plankton communities moved to higher latitudes and only the most specialized plankton remained near the equator, suggesting that the tropical temperatures prevented higher amounts of biodiversity.
“Considering that three billion people live in the tropics, the lack of biodiversity at higher temperatures is not great news,” paper co-leader Adam Woodhouse said in the release.
Next, the team plans to apply similar research methods to other marine plankton groups.
Blue whales have been considered the largest creatures to ever live on Earth. With a maximum length of nearly 30 meters and weighing nearly 200 tons, they are the all-time undisputed heavyweight champions of the animal kingdom.
Now, digging on a beach in Somerset, UK, a team of British paleontologists found the remains of an ichthyosaur, a marine reptile that could give the whales some competition. “It is quite remarkable to think that gigantic, blue-whale-sized ichthyosaurs were swimming in the oceans around what was the UK during the Triassic Period,” said Dean Lomax, a paleontologist at the University of Manchester who led the study.
Giant jawbones
Ichthyosaurs were found in the seas through much of the Mesozoic era, appearing as early as 250 million years ago. They had four limbs that looked like paddles, vertical tail fins that extended downward in most species, and generally looked like large, reptilian dolphins with elongated narrow jaws lined with teeth. And some of them were really huge. The largest ichthyosaur skeleton so far was found in British Columbia, Canada, measured 21 meters, and belonged to a particularly massive ichthyosaur called Shonisaurus sikanniensis. But it seems they could get even larger than that.
What Lomax’s team found in Somerset was a surangular, a long, curved bone that all reptiles have at the top of the lower jaw, behind the teeth. The bone measured 2.3 meters—compared to the surangular found in the Shonisaurus sikanniensis skeleton, it was 25 percent larger. Using simple scaling and assuming the same body proportions, Lomax’s team estimated the size of this newly found ichthyosaur at somewhere between 22 and 26 meters, which would make it the largest marine reptile ever. But there was one more thing.
Examining the surangular, the team did not find signs of the external fundamental system (EFS), which is a band of tissue present in the outermost cortex of the bone. Its formation marks a slowdown in bone growth, indicating skeletal maturity. In other words, the giant ichthyosaur was most likely young and still growing when it died.
Correcting the past
In 1846, five large bones were found at the Aust Cliff near Bristol in southwestern England. Dug out from the upper Triassic rock formation, they were dubbed “dinosaurian limb bone shafts” and were exhibited in the Bristol Museum, where one of them was destroyed by bombing during World War II.
But in 2005, Peter M. Galton, a British paleontologist then working at the University of Bridgeport, noticed something strange in one of the remaining Aust Cliff bones. He described it as an “unusual foramen” and suggested it was a nutrient passage. Later studies generally kept attributing those bones to dinosaurs but pointed out things like an unusual microstructure that was difficult to explain.
According to Lomax, all this confusion was because the Aust Cliff bones did not belong to dinosaurs and were not parts of limbs. He pointed out that the nutrient foramen morphology, shape, and microstructure matched with the ichthyosaur’s bone found in Somerset. The difference was that the EFS—the mark of mature bones—was present on the Aust Cliff bones. If Lomax is correct and they really were parts of ichthyosaurs’ surangular, they belonged to a grown individual.
And using the same scaling technique applied to the Somerset surangular, Lomax estimated this grown individual to be over 30 meters long—slightly larger than the biggest confirmed blue whale.
Looming extinction
“Late Triassic ichthyosaurs likely reached the known biological limits of vertebrates in terms of size. So much about these giants is still shrouded by mystery, but one fossil at a time, we will be able to unravel their secrets,” said Marcello Perillo, a member of the Lomax team responsible for examining the internal structure of the bones.
This mystery beast didn’t last long, though. The surangular bone found in Somerset was buried just beneath a layer full of seismite and tsunamite rocks that indicate the onset of the end-Triassic mass extinction event, one of the five mass extinctions in Earth’s history. The Ichthyotian severnensis, as Lomax and his team named the species, probably managed to reach an unbelievable size but was wiped out soon after.
The end-Triassic mass extinction was not the end of all ichthyosaurs, though. They survived but never reached similar sizes again. They faced competition from plesiosaurs and sharks that were more agile and swam much faster, and they likely competed for the same habitats and food sources. The last known ichthyosaurs went extinct roughly 90 million years ago.
Jeremy Hansen grew up on a farm near the community of Ailsa Craig, Ontario, where he attended elementary school. His family moved to Ingersoll,
Ontario, where he attended Ingersoll District Collegiate Institute. At age 12 he joined the 614 Royal Canadian Air Cadet Squadron in London, Ontario. At 16 he earned his Air Cadet
glider pilot wings and at 17 he earned his private pilot licence and wings. After graduating from high school and Air Cadets, Hansen was accepted for officer training in the Canadian Armed Forces (CAF). He was trained at Chilliwack, British Columbia, and the Royal Military College at Saint-Jean-sur-Richelieu, Quebec. Hansen then enrolled in the Royal Military College of Canada in Kingston,
Ontario. In 1999, he completed a Bachelor of Science in space science with First Class Honours and was a Top Air Force Graduate from the Royal Military College. In 2000, he completed his Master of Science in physics with a focus on wide field of view satellite tracking.
CAF Pilot
In 2003, Jeremy Hansen completed training as a CF-18 fighter pilot with the 410 Tactical Fighter Operational Training Squadron at Cold Lake, Alberta.
From 2004 to 2009, he served by flying CF-18s with the 441 Tactical Fighter Squadron and the 409 Tactical Fighter Squadron. He also flew as Combat Operations Officer at 4 Wing Cold Lake. Hansen’s responsibilities included NORAD operations effectiveness,
Arctic flying operations and deployed exercises. He was promoted to the rank of colonel in 2017. (See also Royal Canadian Air Force.)
Career as an Astronaut
In May 2009, Jeremy Hansen and David Saint-Jacques were chosen out of 5,351 applicants in the Canadian Space Agency’s
(CSA) third Canadian Astronaut Recruitment Campaign. He graduated from Astronaut Candidate Training in 2011 and began working at the Mission Control Center in Houston, Texas, as capsule communicator (capcom, the person in Mission Control who speaks directly
to the astronauts in space.
As a CSA astronaut, Hansen continues to develop his skills. In 2013, he underwent training in the High Arctic and learned how to conduct geological fieldwork (see Arctic Archipelago; Geology). That same year, he participated in the European Space Agency’s CAVES program in Sardinia, Italy. In that human performance experiment Hansen lived underground for six days.
In 2014, Hansen was a member of the crew of NASA Extreme Environment Mission Operations (NEEMO) 19. He spent seven days off Key Largo, Florida, living in the Aquarius habitat on the ocean floor, which is used to simulate conditions of the International
Space Station and different gravity fields. In 2017, Hansen became the first Canadian to lead a NASA astronaut class, in which he trained astronaut candidates from Canada and the United States.
Did you know?
Hansen has been instrumental in encouraging young people to become part of the STEM (Science, Technology, Engineering, Mathematics) workforce with the aim of encouraging future generations of space explorers.
His inspirational work in Canada includes flying a historical “Hawk One” F-86 Sabre jet.
Artemis II
In April 2023, Hansen was chosen along with Americans Christina Koch, Victor Glover and Reid Wiseman to crew NASA’s Artemis II mission to the moon. The mission, scheduled for no earlier
than September 2025 after a delay due to technical problems, marks NASA’s first manned moon voyage since Apollo 17 in 1972. The Artemis II astronauts will not land on the lunar
surface, but will orbit the moon in an Orion spacecraft. They will conduct tests in preparation for future manned moon landings, the establishment of an orbiting space station called Lunar Gateway, or Gateway, and a base on the moon’s surface where astronauts
can live and work for extended periods. The path taken by Orion will carry the astronauts farther from Earth than any humans have previously travelled. Hansen’s participation in Artemis II is a direct result of Canada’s contribution of Canadarm3
to Lunar Gateway. (See alsoCanadarm; Canadian Space Agency.)
“Being part of the Artemis II crew is both exciting and humbling. I’m excited to leverage my experience, training and knowledge to take on this challenging mission on behalf of Canada. I’m humbled by the incredible contributions and hard work of so many
Canadians that have made this opportunity a reality. I am proud and honoured to represent my country on this historic mission.” – Jeremy Hansen (Canadian Space Agency, 2023)
Did you know?
On his Artemis II trip, Hansen will wear an Indigenous-designed mission patch created for him by Anishinaabe artist Henry Guimond.
