Earth may have a new planetary neighbor, orbiting around the next-nearest star system to our own. This new neighbor, residing just 4.2 light years away, is strangely reminiscent of Earth, with some key differences — it is a little larger and much colder — but otherwise, the resemblance is uncanny given their proximity.
The discovery comes after scientists observed what looks like a second planet orbiting around Proxima Centauri, the closest-known star to our own Solar System.
The findings are detailed in a study published Wednesday in the journal Science Advances. The research draws on 17 years of radial velocity measurements to suggest that a super-Earth — basically a larger, Earth-like planet — may be orbiting around Proxima Centauri. The findings provide astronomers with a potential new exoplanet that can be observed at close proximity. They also challenge established theories of how low-mass planets form.
Exploring our galactic neighborhood
Proxima Centauri is located 4.2 light years away from the Solar System. It is one of the sun of the Alpha Centauri star system, the closest known star system to our own. It consists of two stars interlocked in an orbit around each other, or binary stars, and one other star.
Although Proxima Centauri is the closest star to us, it is too small to see with the naked eye. Proxima Centauri is a low-mass red dwarf star, thought to be about an eighth of the mass of the Sun and 500 times less bright.
In 2016, scientists discovered a planet orbiting around the small star. Proxima Centauri b orbits the star at a distance of roughly 4.7 million miles, with an orbital period of approximately 11.2 days. The planet is about the same size as Earth, and orbits within its star’s habitable zone — the distance at which a planet may hold liquid water. Some believe that it may potentially host life.
A brother for Proxima Centuari b
Proxima Centuari b may not be its host star’s only child.
When a planet orbits its star, it causes the star to slightly shift in a small circular motion as it’s tugged on by the planet’s gravitational pull. In the new study, scientists detected changes in the wavelength of the light coming from the star as it shifted between red and blue. The shift indicates that the star is moving towards and away from the Earth at regular intervals — likely due to the presence of a planetary body.
If confirmed, Proxima Centauri c is likely a super-Earth, a planet with a mass larger than that of Earth’s, but smaller than Uranus and Neptune. The potential planet orbits around its star once every 5.2 years, with a mass six times larger than Earth.
Due to its star’s dimness and long orbital period, it is unlikely that Proxima Centauri c is habitable.
But the planet may provide new insights on how planetary bodies form.
Proxima Centauri c challenges theories of how low-mass planets form around low-mass stars. That’s because it is located beyond the ‘snow line’ of the star system.
The snow line is the point at which it is cold enough for any water on planets to freeze. They are an ideal spot for accretion disks, or a rotating disk of matter from which planets form. Super-Earths like Proxima Centauri c generally form near the snow line, and not beyond it — suggesting astronomers are missing something.
That matters for theories about how our own planet formed. Earth is a low-mass planet, too. So if Proxima Centauri c does indeed exist, it may help rewrite our own origin tale.
Lake Huron sinkhole surprise: The rise of oxygen on early Earth linked to changing planetary rotation rate – Phys.org
The rise of oxygen levels early in Earth’s history paved the way for the spectacular diversity of animal life. But for decades, scientists have struggled to explain the factors that controlled this gradual and stepwise process, which unfolded over nearly 2 billion years.
Now an international research team is proposing that increasing day length on the early Earth—the spinning of the young planet gradually slowed over time, making the days longer—may have boosted the amount of oxygen released by photosynthetic cyanobacteria, thereby shaping the timing of Earth’s oxygenation.
Their conclusion was inspired by a study of present-day microbial communities growing under extreme conditions at the bottom of a submerged Lake Huron sinkhole, 80 feet below the water’s surface. The water in the Middle Island Sinkhole is rich in sulfur and low in oxygen, and the brightly colored bacteria that thrive there are considered good analogs for the single-celled organisms that formed mat-like colonies billions of years ago, carpeting both land and seafloor surfaces.
The researchers show that longer day length increases the amount of oxygen released by photosynthetic microbial mats. That finding, in turn, points to a previously unconsidered link between Earth’s oxygenation history and its rotation rate. While the Earth now spins on its axis once every 24 hours, day length was possibly as brief as 6 hours during the planet’s infancy.
The team’s findings are scheduled for publication Aug. 2 in the journal Nature Geoscience.
Lead authors are Judith Klatt of the Max Planck Institute for Marine Microbiology and Arjun Chennu of the Leibniz Centre for Tropical Marine Research. Klatt is a former postdoctoral researcher in the lab of University of Michigan geomicrobiologist Gregory Dick, who is one of the study’s two corresponding authors. The other co-authors are from U-M and Grand Valley State University.
“An enduring question in the Earth sciences has been how did Earth’s atmosphere get its oxygen, and what factors controlled when this oxygenation took place,” Dick said from the deck of the R/V Storm, a 50-foot NOAA research vessel that carried a team of scientists and scuba divers on a sample-collection trip from the town of Alpena, Michigan, to the Middle Island Sinkhole, several miles offshore.
“Our research suggests that the rate at which the Earth is spinning—in other words, its day length—may have had an important effect on the pattern and timing of Earth’s oxygenation,” said Dick, a professor in the U-M Department of Earth and Environmental Sciences.
The researchers simulated the gradual slowing of Earth’s rotation rate and showed that longer days would have boosted the amount of oxygen released by early cyanobacterial mats in a manner that helps explain the planet’s two great oxygenation events.
The project began when co-author Brian Arbic, a physical oceanographer in the U-M Department of Earth and Environmental Sciences, heard a public lecture about Klatt’s work and noted that day length changes could play a role, over geological time, in the photosynthesis story that Dick’s lab was developing.
Cyanobacteria get a bad rap these days because they are the main culprits behind the unsightly and toxic algal blooms that plague Lake Erie and other water bodies around the world.
But these microbes, formerly known as blue-green algae, have been around for billions of years and were the first organisms to figure out how to capture energy from sunlight and use it to produce organic compounds through photosynthesis—releasing oxygen as a byproduct.
Masses of these simple organisms living in primeval seas are credited with releasing oxygen that later allowed for the emergence of multicellular animals. The planet was slowly transformed from one with vanishingly small amounts of oxygen to present-day atmospheric levels of around 21%.
At the Middle Island Sinkhole in Lake Huron, purple oxygen-producing cyanobacteria compete with white sulfur-oxidizing bacteria that use sulfur, not sunlight, as their main energy source.
In a microbial dance repeated daily at the bottom of the Middle Island Sinkhole, filmy sheets of purple and white microbes jockey for position as the day progresses and as environmental conditions slowly shift. The white sulfur-eating bacteria physically cover the purple cyanobacteria in the morning and evening, blocking their access to sunlight and preventing them from carrying out oxygen-producing photosynthesis.
But when sunlight levels increase to a critical threshold, the sulfur-oxidizing bacteria migrate back down below the photosynthetic cyanobacteria, enabling them to start producing oxygen.
The vertical migration of sulfur-oxidizing bacteria has been observed before. What’s new is that the authors of the Nature Geoscience study are the first to link these microbial movements, and the resultant rates of oxygen production, to changing day length throughout Earth’s history.
“Two groups of microbes in the Middle Island Sinkhole mats compete for the uppermost position, with sulfur-oxidizing bacteria sometimes shading the photosynthetically active cyanobacteria,” Klatt said while processing a core sample from Middle Island Sinkhole microbial mats in an Alpena laboratory. “It’s possible that a similar type of competition between microbes contributed to the delay in oxygen production on the early Earth.”
A key to understanding the proposed link between changing day length and Earth’s oxygenation is that longer days extend the afternoon high-light period, allowing photosynthetic cyanobacteria to crank out more oxygen.
“The idea is that with a shorter day length and shorter window for high-light conditions in the afternoon, those white sulfur-eating bacteria would be on top of the photosynthetic bacteria for larger portions of the day, limiting oxygen production,” Dick said as the boat rocked on choppy waters, moored a couple hundred yards from Middle Island.
The present-day Lake Huron microbes are believed to be good analogs for ancient organisms in part because the extreme environment at the bottom of the Middle Island Sinkhole likely resembles the harsh conditions that prevailed in the shallow seas of early Earth.
Lake Huron is underlain by 400-million-year-old limestone, dolomite and gypsum bedrock that formed from the saltwater seas that once covered the continent. Over time, the movement of groundwater dissolved some of that bedrock, forming caves and cracks that later collapsed to create both on-land and submerged sinkholes near Alpena.
Cold, oxygen-poor, sulfur-rich groundwater seeps into the bottom of the 300-foot-diameter Middle Island Sinkhole today, driving away most plants and animals but creating an ideal home for certain specialized microbes.
Dick’s team, in collaboration with co-author Bopaiah Biddanda of the Annis Water Resources Institute at Grand Valley State University, has been studying the microbial mats on the floor of Middle Island Sinkhole for several years, using a variety of techniques. With the help of scuba divers from NOAA’s Thunder Bay National Marine Sanctuary—which is best known for its shipwrecks but is also home to the Middle Island Sinkhole and several others like it—the researchers deployed instruments to the lake floor to study the chemistry and biology there.
They also brought mat samples to the lab to conduct experiments under controlled conditions.
Klatt hypothesized that the link between day length and oxygen release can be generalized to any given mat ecosystem, based on the physics of oxygen transport. She teamed up with Chennu to conduct detailed modeling studies to relate microbial mat processes to Earth-scale patterns over geological timescales.
The modeling studies revealed that day length does, in fact, shape oxygen release from the mats.
“Simply speaking, there is just less time for the oxygen to leave the mat in shorter days,” Klatt said.
This led the researchers to posit a possible link between longer day lengths and increasing atmospheric oxygen levels. The models show that this proposed mechanism might help explain the distinctive stepwise pattern of Earth’s oxygenation, as well as the persistence of low-oxygen periods through most of the planet’s history.
Throughout most of Earth’s history, atmospheric oxygen was only sparsely available and is believed to have increased in two broad steps. The Great Oxidation Event occurred about 2.4 billion years ago and has generally been credited to the earliest photosynthesizing cyanobacteria. Nearly 2 billion years later a second surge in oxygen, known as the Neoproterozoic Oxygenation Event, occurred.
Earth’s rotation rate has been slowly decreasing since the planet formed about 4.6 billion years ago due to the relentless tug of the moon’s gravity, which creates tidal friction.
Possible link between Earth’s rotation rate and oxygenation, Nature Geoscience (2021). DOI: 10.1038/s41561-021-00784-3 , www.nature.com/articles/s41561-021-00784-3
University of Michigan
Lake Huron sinkhole surprise: The rise of oxygen on early Earth linked to changing planetary rotation rate (2021, August 2)
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Astronomers spot light behind a black hole for the first time, reaffirming Einstein's theory of general relativity – TechSpot
Something to look forward to: An international team of astronomers have observed light from behind a black hole for the first time. Future observatories, like the Advanced Telescope for High Energy Astrophysics (Athena) should provider even higher resolution images with much shorter observation times.1
Led by Stanford University’s Dan Wilkins, the team focused on a black hole that is 10 million times as massive as our sun and located 1,800 million light years away in a galaxy called I Zwicky.
Armed with the European Space Agency’s XMM-Newton and NASA’s NuSTAR space telescopes, the astronomers observed bright flares of X-ray light coming from around the black hole. The X-ray flares echoed off of gas that was falling into the black hole, and as the flares were subsiding, the telescopes were remarkably able to pick up smaller flashes of X-rays that were different “colors.” These were the echoes bouncing off the gas behind the black hole.
“Any light that goes into that black hole doesn’t come out, so we shouldn’t be able to see anything that’s behind the black hole,” Wilkins said. “The reason we can see that is because that black hole is warping space, bending light and twisting magnetic fields around itself,” he added.
The black hole’s gravitational pull is responsible for the warping of space.
This is the first time that astronomers have directly observed light from behind a black hole, and it also matches Einstein’s theory of general relativity, yet again confirming his predictions.
The team’s findings were recently published in the scientific journal Nature.
Image credit Dan Wilkins
Russian cosmonauts give video tour of module that jolted space station – Euronews
MOSCOW – Russian cosmonauts have given a video tour of the interior of a research module which briefly threw the International Space Station out of control on Thursday a few hours after docking.
Russian space officials said a software glitch and possible lapse in human attention were to blame for the mishap that caused the entire space station to pitch out of its normal flight position 250 miles above the Earth with seven crew members aboard.
Footage published late on Saturday showed cosmonauts Oleg Novitsky and Pyotr Dubrov opening the hatches and giving a short tour inside the Nauka module, the Russian space agency Roscosmos said.
According to NASA‘s account of Thursday’s incident, the mission flight director immediately declared a spaceflight emergency as engineers on the ground struggled to restore stability to the sprawling research satellite.
NASA and Roscosmos each said that the seven crew members – two Russian cosmonauts, three U.S. astronauts and two others from Japan and France – were never in any immediate danger.
Roscosmos, which this week spoke of plans to launch another Russian module to the station in November, has suffered a series of mishaps and corruption scandals, including during the construction of the Vostochny Cosmodrome in the country’s far east where contractors were accused of embezzling state funds.
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