Astronomers have discovered another candidate exoplanet orbiting our neighbor, Proxima Centauri. A paper announcing these results was just published in the journal Science Advances. If confirmed, it will be the second exoplanet orbiting the star.
It was big news in 2016 when astronomers discovered a planet orbiting Proxima Centauri (PC,) the nearest star to our Sun. That planet, named Proxima b, is potentially habitable, and at the time there was speculation that we could send a robotic explorer there in only a few decades. The discovery of a second planet, even though it’s likely too far away from its star for liquid water, is intensifying interest in the PC system.
The discoverers of this new planet, Proxima c, say that follow-up observations are needed to confirm it as a planet. Changes in the stellar activity of Proxima Centauri indicated the presence of another planet. But they also say that the data they have can’t be explained in terms of any stellar activity itself. Due to its proximity, and also its angular separation from the star, it is a prime candidate for follow-up observations—and even imaging—with next generation telescopes.
Proxima c’s mass is about half that of Neptune and its orbit is about 1.5 times that of Earth. Its temperature is about -200 C, if it has no atmosphere. Proxima Centauri has undergone intense astronomical scrutiny in the last few years, and that has ruled out the presence of any Jupiter-sized planets between 0.8 and 5+ astronomical units from the star. But finding Proxima c is still surprising, because its presence challenges our models of how super-Earths form and evolve.
Hugh Jones, a Professor of Astrophysics at Hertfordshire University, was also involved in the study. In an article in “The Conversation,” Jones pointed out how difficult it can be to separate data showing the presence of a planet, from data showing stellar activity at the host star. “Just like our sun, Proxima has spots caused by regions of intense magnetic activity which are moving in and out of view, changing in intensity on a variety of timescales. These features need to be considered when searching for any planetary signals.”
Even though stellar activity doesn’t match the data, the discoverers are being cautious until follow-up observations can either confirm or deny the presence of Proxima c, and definitively rule out stellar activity.
The discovery of this new candidate exoplanet is contained in this new paper, but the history goes back a few years.
Multiple teams of scientists have scoured Proxima Centauri for exoplanets. Much of their work depended on radial velocity data, notably from the ESO’s HARPS (High Accuracy Radial velocity Planet Searcher.) Study by study, astronomers have excluded the presence of certain mass-range planets within certain AU ranges from PC.
A 1999 study excluded the presence of any planets beyond 1700 AUs of PC, because PC itself orbits Alpha Centauri AB. A 2019 study set an upper limit of 0.3 Jupiter masses for any planet within 10 AU of PC. That same study excluded the presence of planets between 10 and 50 AU in the mass range 0.3 to 8 masses of Jupiter. Other studies put on more constraints.
But astronomers also know that red dwarfs host more small planets than other types of stars. So they kept looking.
Can We Really Send A Spacecraft There?
The Breakthrough Starshot Initiative (BSI) thinks they can send a tiny spacecraft to Proxima Centauri.
When the Centauri b exoplanet was discovered in 2016, the BSI got to work. They think they can send a nano-spacecraft with cameras to within one AU of the planet and return images much more detailed than we can hope to achieve with any telescope. They say they should be able to return images showing continents and oceans. On their website, BSI says “To achieve comparable resolution with a space telescope in Earth’s orbit, the telescope would have to be 300km in diameter.”
But even though PC is “close” in astronomical terms, it’s still an immense distance away. At 4.2 light years away, it would still take decades to get there, travelling at 20% the speed of light (about 216,000,000 kilometers per hour.) Currently, the fastest spacecraft is NASA’s Parker Solar Probe, which will reach a top speed of only 692,000 km/h.
But whether we can get a spacecraft there or not is only part of the story. Due to its proximity, the Proxima Centauri system is an observable laboratory for understanding other solar systems. And its presence and proximity might spur further technological development needed to study it and other systems in more detail.
As Hugh Jones said in his article at The Conversation, “Ultimately, the discovery of multiple signals from the very closest star shows that planets are more common than stars. Proxima represents an excellent location for understanding the closest exoplanets and developing new technologies to better understand the universe we live in.”
Proxima c’s existence is problematic, or at least significant, for our planet formation models. Among super-Earth planets around low-mass stars detected by radial velocity, Proxima c would have both the longest period and the lowest mass. It would also be the furthest distance from its parent star than the frost line in the original protoplanetary disk. The frost line was probably at 0.15 AU.
The authors say that it’s unlikely that Proxima c was kicked out from its initial position closer to the star due to some instability, “because its orbit is consistent with a circular one and because of the absence of more massive planets on shorter orbital distance.”
In their paper, they say, “The formation of a super-Earth well beyond the snowline challenges formation models according to which the snowline is a sweet spot for the accretion of super-Earths, due to the accumulation of icy solids at that location.”
Proxima Centauri is a red dwarf star, or M dwarf. It’s about 4.2 light years away from the Sun, making it our closest neighbour. It’s the third star in a trinary system, with the Alpha Centauri AB binary star. Proxima Centauri is about 13,000 AU from Alpha Centauri AB, and was discovered in 1915.
A new report suggests a warm “blob” of water could be behind the mass starvation of a North Pacific seabird.
According to a report published in the science journal PLOS ONE, about 62,000 dead or dying common murres washed ashore between California and Alaska between summer 2015 and spring 2016. Carcass recovery brings the death estimate up to around one million in total.
On Jan. 1 and 2, 2016, 6,540 common murre carcasses were found washed ashore near Whitter, Alaska, translating into about 8,000 bodies per mile of shoreline – one of the highest beaching rates recorded during the mass mortality event. (Photo by David B. Irons)
The report says there’s nothing to suggest the emaciated birds died from anything other than starvation.
Additionally, no murre chicks were born at breeding colonies between 2015 and 2017.
Researchers linked the deaths to a “large mass of unusually warm seawater” known as the “Blob” and the strong El Niño that followed, creating a “severe marine heatwave” stretching from California to Alaska between 2014 and 2016.
In a statement, authors said the mass deaths “raise a red-flag warning about the state of marine ecosystems on the continental shelf of western North America.”
The study links to previous research suggesting that warmer marine temperatures reduce both the quantity and quality of phytoplankton – reducing the health and numbers of fish who eat them and increasing the metabolic needs of larger fish that compete with murres for food.
Researchers hypothesize that the warm water ultimately led to the birds’ mass starvation and lack of reproduction.
The murre die-off revealed a major disruption in marine food webs, with alarming declines not only in murres, but in other seabirds, commercial fish and great whales between 2016 and 2019.
Researchers say they are only beginning to understand “the mechanisms and full magnitude of effects of the 2014-16 heatwave, and what it portends if such heatwaves become stronger and more frequent, as predicted.”
They were once abundant, in our hairsprays, bug sprays, and refrigerators. And then scientists figured out these substances ripped a hole in the ozone layer, leading to a 1987 plan to phase them out that over time would be agreed to by every country in the world.
More than three decades later, researchers have made a new discovery.
Ozone-depleting substances do more than just gnaw at Earth’s protective layer. They’re also greenhouse gases, so they contribute to the planet’s overall warming by trapping heat, too. And now we may know just how much these substances have contributed to Arctic warming, thanks to a study published in the science journal Nature on Monday.
Between 1955 and 2005, ozone-depleting gases caused half of Arctic climate change (and a third of overall global warming), the study finds. This is primarily due to their heat-trapping qualities, not their ozone munching. The Arctic has seen rapidly melting sea ice for years and is warming faster than the rest of the world. When the sea ice melts in the Earth’s northernmost region, sea levels rise across the globe leading to potential flooding.
Between 1955 and 2005, ozone-depleting gases caused half of Arctic climate change.
These ozone-depleting gases include chlorofluorocarbons (CFCs), which we’ve been cracking down on since the global agreement known as the Montreal Protocol was finalized 33 years ago. CFCs, which include propellants and refrigerants, have been around since the 1920s and 1930s. Their popularity peaked in the late 20th century and have been on the decline since the Montreal Protocol.
To quantify the climate impact of ozone-depleting gasses, scientists from Columbia University, the Institute for Atmospheric and Climate Sciences in Switzerland, and University of Toronto used climate models to run a variety of simulations. In one, they tested what would happen if stratospheric ozone and the pesky gases that hurt it stayed at 1955 levels. Research on CFCs’ climate impacts beyond ozone depletion is scant, even though they can trap more heat than climate change poster child carbon dioxide, the study notes.
The study’s findings not only give an extra gold star to the much-acclaimed Montreal Protocol, but also provide a bit of hope when so much climate change research focuses on doom and gloom.
“Our findings also have implications for the future because the phase-out of [ozone-depleting substances], which is well under way, will substantially mitigate Arctic warming and sea-ice melting in the coming decades,” the study explains.
Indeed, Cecilia Bitz, a climate scientist at the University of Washington in Seattle who was not involved in the study, told Nature, “It’s a very important paper because it has a little shred of optimism.”
Don’t get too excited just yet, though. More studies that replicate these findings need to be done to corroborate the evidence, Bitz, the study authors, and other scientists say.
Then there’s also the problem of CFCs still being used despite global crackdowns. For example, China is struggling to tamp down on illegal CFC production. In addition, we’ve just begun to tackle hydrofluorocarbons (HFCs), which air conditioner and refrigerator manufacturers turned to when they were blocked from CFCs, on a global scale. HFCs are less harmful for the ozone than CFCs, but like their loathed counterpart, they’re more powerful than carbon dioxide when it comes to trapping heat.
And to be clear, weakening the ozone is still a very bad trait to have. Scientists expect it’ll take another 50 years before the ozone hole over Antarctica is back to its 1980 level.
Researchers named the dinosaur Wulong bohaiensis, which translates to “a dancing dragon.”
The dinosaur was about the size of a raven but double its length with a long, bony tail. Its entire body was covered with feathers, complete with two plumes at the tail’s end.
Despite its small size, it had a fierce, narrow face and a mouth full of sharp teeth. Like a bird, it had small, light bones and wing-like forelimbs. And there were also a number of feathers on its legs.
The fossil was initially discovered in the fossil-filled Jehol Province a decade ago by a farmer and was placed in China’s Dalian Natural History Museum.
Researchers, including Ashley Poust, a postdoctoral researcher at the San Diego Natural History Museum, later analyzed the fossil (at the time, Poust was still a student at Montana State University).
“The new dinosaur fits in with an incredible [range] of feathered, winged animals that are closely related to the origin of birds,” Poust, the study’s author, said. “Studying specimens like this not only shows us the sometimes surprising paths that ancient life has taken, but also allows us to test ideas about how important bird characteristics, including flight, arose in the distant past.”
This dinosaur was a juvenile when it died, according to its bones, but its feathers resembled that of a mature adult. This suggests that the feathers grew quickly, unlike modern birds, which take time to grow their mature feathers.
“Either the young dinosaurs needed these tail feathers for some function we don’t know about, or they were growing their feathers really differently from most living birds,” Poust said.
The dinosaur was an early relative of Velociraptors, which lived 75 million years ago. Its contemporaries would have been Microraptors, small feathered dinosaurs that resembled birds.
The researchers actually sliced into several bones from the fossil and studied them with microscopes to understand the different regions of the skeleton. They also compared it to a close relative that also appeared more mature, known as the Sinornithosaurus.
Surprisingly, that dinosaur was also still growing when it died. The researchers said that histology, or cutting up the bones, was the only way for them to truly know the life stage of the dinosaurs when they died.
“We’re talking about animals that lived twice as long ago as T. rex, so it’s pretty amazing how well-preserved they are,” Poust said. “It’s really very exciting to see inside these animals for the first time.”
Fossils from the Jehol Province have painted a portrait of the diverse life that once flourished there. It’s an area in northeastern China full of exceptionally preserved fossil discoveries that has been studied for the past 90 years.
Researchers learned that birds, pterosaurs and bird-like dinosaurs all lived in the environment at the same time. This is also when flowering plants initially began to flourish.
“There was a lot of flying, gliding and flapping around these ancient lakes,” Poust said. “As we continue to discover more about the diversity of these small animals, it becomes interesting how they all might have fit into the ecosystem. It was an alien world, but with some of the earliest feathers and earliest flowers, it would have been a pretty one.”
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