How we spotted a potential new planet around the sun's neighbouring star – The Conversation UK
Most exoplanets, bodies orbiting stars other than the sun, are too far away for us to be able to send probes to. So it’s no wonder that the discovery of a possible habitable planet around the sun’s nearest neighbour star, Proxima Centauri, a few years ago generated a lot of excitement. Now we have spotted what we think is a second planet around this star.
Our study, published in Science Advances, suggests this planet could have a mass about half that of the planet Neptune. Dubbed Proxima Centauri c (abbreviated to Proxima c), it has an orbit about 1.5 times greater than the Earth’s orbit around the sun.
The star Proxima Centauri is the smallest star in a triple system in the constellation of Centaurus. Since it is the star in closest proximity to our sun, it is usually referred to as Proxima. It wasn’t discovered until 1915 by the Scottish astronomer Robert Innes because it is too faint to see with the naked eye. Like most stars, Proxima Centauri is a cool, small object known as a “red dwarf” star. It is about eight times less massive than the sun and has about half its temperature.
The previously discovered planet Proxima b is (most likely) a rocky planet orbiting the star within its habitable zone. However, Proxima c orbits relatively far from its cool star and is therefore unlikely to be habitable. If it doesn’t have an atmosphere, it most likely has a temperature below -200°C.
Proxima b was found by analysing the star’s spectra – light broken down by wavelength to provide a “fingerprint” showing what an object is made of. Small shifts in this starlight can be used to work out tiny movements of the star in response to an orbiting planet’s gravitational pull. This is called the radial velocity technique. The first signal was weak. But further observations were made and existing ones reanalysed to verify the planet’s existence.
The history of detecting and understanding exoplanets has been driven forward by a wide variety of techniques. Exoplanets were discovered for the first time in 1992, from radio observations of a pulsar, the collapsed core of giant star.
Efforts significantly grew in 1995 after the announcement of a planet in orbit around the sun-like star 51 Pegasi using the radial velocity technique. This discovery was subsequently awarded part of the 2019 Nobel prize in Physics. There have always been concerns, however, that apparent planetary signals might be caused by stellar activity. It was not until after 2000, and the discovery of the exoplanets with a variety of techniques, that the existence of exoplanets became widely accepted.
Our detection of the new planet, Proxima c, used the same radial velocity technique as that used for the Nobel Prize-winning work, but the signal is 40 times weaker on a 400 times longer timescale. This made it a very challenging discovery. 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.
The sun’s spots, probably created by a build up of plasma, lead to magnetic field flips approximately every 11 years. For the sun this timescale is fairly consistent, but the number of sunspots remain infuriatingly difficult to predict. Unlike the sun, which has been carefully monitored for centuries, we know far less about Proxima Centauri, so it’s plausible that an activity cycle of its star could mimic a planetary signal. Further observations can, however, strengthen the evidence for its existence.
The ideal way to verify its existence would be with a direct image. However, for exoplanets this is exceedingly difficult because they are generally too close to their stars to be seen from Earth with current technology – they drown in the star’s light. But Proxima is a cool, dim star, making the contrast between star and its planets significantly easier. What’s more, the distance and orbit of Proxima c means you should be able to see them both in the sky using large telescopes on Earth.
The signal reported from Proxima c was found with the La Silla Observatory in Chile, an optical telescope with a diameter of 3.6m. The diameter of the Extremely Large Telescope, currently under construction on a nearby mountain, will be 39m and might detect Proxima c with a number of its instruments.
Can we go there?
Proxima c is an ideal planet for follow-up studies compared to other planets discovered around more distant stars. To confirm its existence and characterise its properties will require state-of-the-art technology. That said, Proxima c should provide a benchmark example for how similar or different exoplanets really are from the planets in our solar system.
Since Proxima is the closest star to our sun, one might think it would be easier to just travel there. However, at 4.2 light years, it is still immensely distant for humans. If the distance between the Earth and the sun were 1cm, Proxima is 11km away. That said, an exciting project called Breakthrough Starshot is planning to send a microchip starship to the triple-star system that includes Proxima. Such a microchip starship might be propelled by lasers and reach the system a few decades from now.
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.
A "supervolcano" in Italy last erupted in 1538. Experts warn it's "nearly to the breaking point" again. – CBS News
A long-dormant “supervolcano” in southern Italy is inching closer to a possible eruption — nearly six centuries after it last erupted, according to European researchers.
The Campi Flegrei volcano, which is located near the city of Naples, has become weaker over time and as a result is more prone to rupturing, according to a peer-reviewed study conducted by researchers from England’s University College London and Italy’s National Research Institute for Geophysics and Volcanology.
The study used a model of volcano fracturing to interpret the patterns of earthquakes and ground uplift. There have been tens of thousands of earthquakes around the volcano, and the town of Pozzuoli, which rests on top of Campi Flegrei, has been lifted by about 13 feet as a result of them. The quakes and rising earth have stretched parts of the volcano “nearly to the breaking point,” according to a news release about the study, and the ground seems to be breaking, rather than bending.
The earthquakes are caused by the movement of fluids beneath the surface, the news release said. It’s not clear what those fluids are, but researchers said they may be molten rock, magma or natural volcanic gas.
The earthquakes have taken place during the volcano’s active periods. While it last erupted in 1538, it has been “restless” for decades, with spikes of unrest occurring in the 1950s, 1970s and 1980s. There has been “a slower phase of unrest” in the past 10 years, researchers said, but 600 earthquakes were recorded in April, setting a new monthly record.
According to LiveScience, Campi Flegrei is often referred to as a “supervolcano,” which can produce eruptions reaching a category 8 — the highest level on the Volcano Explosivity Index. However, Campi Flegrei’s biggest-ever eruption technically ranked as a category 7, which is still considered a very large and disastrous eruption, LiveScience reported.
While Campi Flegrei — which means “burning fields” — may be closer to rupture, there is no guarantee that this will actually result in an eruption, the study concluded.
“The rupture may open a crack through the crust, but the magma still needs to be pushing up at the right location for an eruption to occur,” said Professor Christopher Kilburn, who studies earth sciences at University College London and was the lead author of the study.
Kilburn said that this is the first time the model has been applied to a volcano in real-time. Since first using the model in 2017, the volcano has behaved as predicted, Kilburn said, so researchers plan to expand the use of the model to look at other volcanoes that reawakened after long periods of dormancy. The goal is to establish more reliable criteria to decide if an eruption is likely and establish a model that can be applied to multiple volcanoes.
“The study is the first of its kind to forecast rupture at an active volcano. It marks a step change in our goal to improve forecasts of eruptions worldwide,” Kilburn said.
Mountains 3 To 4 Times Higher Than Mount Everest Found Deep Inside Earth: Scientists – NDTV
The deep Earth contains mountains with peaks three to four times higher than Mount Everest, scientists have found. According to the BBC, a team of experts from Arizona State University used seismology centres in Antarctica and found these astonishingly huge mountains in the boundary between the core and mantle, around 2,900 kilometres deep inside our planet.
“The mountain-like structures they revealed are utterly mysterious,” the BBC report read. Scientists explained that these underground mountain ranges – dubbed ultra-low velocity zones or ULVZs – had managed to escape the experts’ gaze all these years until earthquakes and atomic explosions generated enough seismic data to be spotted by them.
Scientists believe that these huge mountain ranges are over 24 miles (38 kilometres) in height, while Mount Everest is around 5.5 miles (8.8 kilometres) from the surface. “Analysing 1000’s of seismic recordings from Antarctica, our high-definition imaging method found thin anomalous zones of material at the CMB [core-mantle boundary] everywhere we probed,” Arizona State University geophysicist Edward Garnero said in a statement.
“The material’s thickness varies from a few kilometres to 10’s of kilometres. This suggests we are seeing mountains on the core, in some places up to 5 times taller than Mt. Everest,” he added.
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Further, as per the report, experts explained the possible reason behind the formation of these mysterious mountain peaks. They believe that these ancient formations were created when oceanic crusts were formed into Earth’s interior. They also argue that it might have begun with tectonic plates slipping down into our planet’s mantle and sinking to the core-mantle boundary. These then slowly spread out to form an assortment of structures, leaving a trail of both mountains and blobs. This would, therefore, mean that these mysterious mountains are made of ancient oceanic crust, which is a combination of basalt rock and sediments from the ocean floor.
Now, with this recent discovery, scientists are seeking to argue that these underground mountains may play a critical role in how heat escapes the Earth’s core. “Seismic investigations, such as ours, provide the highest resolution imaging of the interior structure of our planet, and we are finding that this structure is vastly more complicated than once thought,” study co-author and University of Alabama geoscientist Samantha Hansen said in a statement.
“Our research provides important connections between shallow and deep Earth structure and the overall processes driving our planet,” she added.
Campi Flegrei volcano edges closer to possible eruption
The Campi Flegrei volcano in southern Italy has become weaker and more prone to rupturing, making an eruption more likely, according to a new study by researchers at UCL (University College London) and Italy’s National Research Institute for Geophysics and Volcanology (INGV).
The volcano, which last erupted in 1538, has been restless for more than 70 years, with two-year spikes of unrest in the 1950s, 1970s and 1980s, and a slower phase of unrest over the last decade. Tens of thousands of small earthquakes have occurred during these periods and the coastal town of Pozzuoli has been lifted by nearly 4 m (13 ft), roughly the height of a double-decker bus.
The new study, published in the journal Communications Earth & Environment, used a model of volcano fracturing, developed at UCL, to interpret the patterns of earthquakes and ground uplift, and concluded that parts of the volcano had been stretched nearly to breaking point.
Lead author Professor Christopher Kilburn (UCL Earth Sciences) said, “Our new study confirms that Campi Flegrei is moving closer to rupture. However, this does not mean an eruption is guaranteed. The rupture may open a crack through the crust, but the magma still needs to be pushing up at the right location for an eruption to occur.”
“This is the first time we have applied our model, which is based on the physics of how rocks break, in real-time to any volcano.”
“Our first use of the model was in 2017 and since then Campi Flegrei has behaved as we predicted, with an increasing number of small earthquakes indicating pressure from below.”
“We will now have to adjust our procedures for estimating the chances of new routes being opened for magma or gas to reach the surface.”
“The study is the first of its kind to forecast rupture at an active volcano. It marks a step change in our goal to improve forecasts of eruptions worldwide.”
Dr. Nicola Alessandro Pino from the Vesuvius Observatory, which represents the INGV in Naples, said, “Our results show that parts of the volcano are becoming weaker. This means that it might break even though the stresses pulling it apart are smaller than they were during the last crisis 40 years ago.”
Campi Flegrei is the closest active volcano to London. It is not an obvious volcano because, instead of growing into a traditional mountain, it has the shape of a gentle depression 12-14 km (7.5-8.5 miles) across (and thus is known as a caldera). This explains why 360,000 people now live on its roof.
For the past decade, the ground below Pozzuoli has been creeping upwards at about 10 cm (4 in) a year. Persistent small earthquakes have also been registered for the first time since the mid-1980s. More than 600 were recorded in April, the largest monthly number so far.
The disturbance has been caused by the movement of fluids about 3 km (2 miles) beneath the surface. Some of the fluids may be molten rock, or magma, and some may be natural volcanic gas. The latest phase of unrest appears likely to be caused by magmatic gas that is seeping into gaps in the rock, filling the 3 km-thick crust like a sponge.
The earthquakes occur when faults (cracks) slip due to the stretching of the crust. The pattern of earthquakes from 2020 suggests the rock is responding in an inelastic way, by breaking rather than bending.
Dr. Stefania Danesi from INGV Bologna said, “We cannot see what is happening underground. Instead we have to decipher the clues the volcano gives us, such as earthquakes and uplift of the ground.”
In their paper, the team explained that the effect of the unrest since the 1950s is cumulative, meaning an eventual eruption could be preceded by relatively weak signals such as a smaller rate of ground uplift and fewer earthquakes. This was the case for the eruption of the Rabaul caldera in Papua New Guinea in 1994, which was preceded by small earthquakes occurring at a tenth of the rate than had occurred during a crisis a decade earlier.
Campi Flegrei’s current tensile strength (the maximum stress a material can bear before breaking when it is stretched) is likely to be about a third of what it was in 1984, the researchers said.
The team emphasized that an eruption was not inevitable. Dr. Stefano Carlino from the Vesuvius Observatory explained, “It’s the same for all volcanoes that have been quiet for generations. Campi Flegrei may settle into a new routine of gently rising and subsiding, as seen at similar volcanoes around the world, or simply return to rest. We can’t yet say for sure what will happen. The important point is to be prepared for all outcomes.”
Professor Kilburn and colleagues will now apply the UCL model of volcano fracturing to other volcanoes that have reawakened after a long period of time, seeking to establish more reliable criteria for deciding if an eruption is likely. Currently, eruptions are forecast using statistical data unique to each volcano, rather than drawing on fundamental principles that can be applied to multiple volcanoes.
Potential for rupture before eruption at Campi Flegrei caldera, Southern Italy, Communications Earth & Environment (2023). DOI: 10.1038/s43247-023-00842-1
University College London
Campi Flegrei volcano edges closer to possible eruption (2023, June 9)
retrieved 9 June 2023
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