Solar Orbiter Continues to Get Closer to the Sun, Revealing More and More With Each Pass
On April 10th, ESA’s Solar Orbiter made its closest flyby of the Sun, coming to within just 29% of the distance from the Earth to the Sun. From this vantage point, the spacecraft is performing close-up studies of our Sun and inner heliosphere. This is basically uncharted territory, as we’ve never had a spacecraft this close to the Sun.
One of the goals of the mission is to figure out why the Sun’s corona — its outer atmosphere — is so hot. The corona can reach temperatures of 2 million degrees C, vastly hotter than its 5,500 C surface. A new paper based on Solar Orbiter data, may offer some clues.
Last year, the spacecraft returned data showing that a known phenomenon called magnetic reconnection is taking place on the Sun’s surface. But in this case, it is taking place on extremely small scales, which previously were not able to be seen.
In the team’s paper, published in the journal Nature, they explain that magnetic reconnection occurs when a magnetic field changes itself into a more stable configuration. It is a fundamental energy release mechanism in superheated gasses known as plasmas. These reconnections have been seen previously occurring over large areas of the Sun’s surface and are known to be a key mechanism involved in causing solar flares and eruptions.
The new research, which combined data from Solar Orbiter along with NASA’s Solar Dynamics Observatory (SDO) and the Interface Region Imaging Spectrograph (IRIS) missions, shows that the magnetic reconnection occurring at smaller scales is a prime candidate for the mysterious heating of the Sun’s corona.
“Taking advantage of extreme-ultraviolet (EUV) imaging data from the High-resolution Coronal Imager (Hi-C), which ideally is able to resolve scales on the order of 150?km, provided evidence for reconnection between braided magnetic threads and corresponding heating,” the team wrote in their paper. They said the observations, which took place on March 2, 2022 took place over the period of one hour.
In an ESA press release, the team said Solar Orbiter’s ultra-high-resolution observations shows persistent small-scale (around 390 km across) reconnections take place in the corona. These are revealed to be a long-lived ‘gentle’ sequence compared to sudden explosive releases of energy that reconnection is usually associated with for events like coronal mass ejections.
The researchers said the temperatures around the point of the magnetic field where the magnetic field intensity drops to zero, known as the null-point, sustained itself at around 10 million °C, and generated an outflow of material that came in the form of discrete ‘blobs’ travelling away from the null point with a speed of around 80 km/s.
Views from various spacecraft showing the observations of the solar magnetic reconnection event. The top shows the Solar Dynamics Observatory’s Atmospheric Imaging Assembly (AIA) full image of the Sun, overlaid with the greyscale image from SDO’s Helioseismic and Magnetic Imager (HMI) for the area observed by Solar Observatory’s Extreme Ultraviolet Imager (EUI.) B displays the fine structure of the observed event, NOAA 12957. C is a zoom-in) showing a fan-like bright structure. D is a zoom-in of the point-like brightening (white box in c) indicating the spatial scale of heated plasma associated with the null reconnection. Credit: X. Cheng et al.
In addition to this continuous outflow, an explosive episode also took place around this null point, and lasted for four minutes.
The team said that Solar Orbiter’s results suggest that magnetic reconnection, at scales that were previously too small to be resolved, proceeds continually in both gentle and explosive ways. This is importantly because it means that reconnection can therefore persistently transfer mass and energy to the overlying corona, contributing to heating it.
As the Solar Orbiter mission continues, the researchers said they now hope perform observations at even higher spatio-temporal resolution in future close approaches by the spacecraft to estimate what fraction of the corona’s heat may be transferred in this way.
The spacecraft is in a 180 day-long orbit around the Sun, where it reaches closest approach to the Sun every six months, at around 42 million km (26 million miles) from the Sun.
Further reading:
Paper published in
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Starship gave us quite a show during the first flight test of a fully integrated Starship (S24) and Super Heavy rocket (B7) from Starbase in Texas.
On April 20, 2023 at 8:33 a.m. CT, Starship successfully lifted off from the orbital launch pad for the first time. The vehicle cleared the pad and beach as Starship climbed to an apogee of ~39 km over the Gulf of Mexico – the highest of any Starship to-date.
With a test like this, success comes from what we learn, and we learned a tremendous amount about the vehicle and ground systems today that will help us improve on future flights of Starship.
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This is the vehicle trajectory and mission control audio without any additional commentary. There may be very long periods of silence. For our full hosted webcast, visit
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When two black holes collide, they don’t smash into each other the way two stars might. A black hole is an intensely curved region of space that can be described by only its mass, rotation, and electric charge, so two black holes release violent gravitational ripples as merge into a single black hole. The new black hole continues to emit gravitational waves until it settles down into a simple rotating black hole. That settling down period is known as the ring down, and its pattern holds clues to some of the deepest mysteries of gravitational physics.
Gravitational wave observatories such as the Laser Interferometry Gravitational-Wave Observatory (LIGO) have mostly focused on the inspiral period of black hole mergers. This is the period where the two black holes orbit ever closer to each other, creating a rhythmic stream of strong gravitational waves. From this astronomers can determine the mass and rotation of the original black holes, as well as the mass and rotation of the merged black hole. The pattern of gravitational waves we observe is governed by Einstein’s general relativity equations, and by matching observation to theory we learn about black holes.
General relativity describes gravity extremely well. Of all the gravitational tests we’ve done, they all agree with general relativity. But Einstein’s theory doesn’t play well with the other extremely accurate physical theory, quantum mechanics. Because of this, physicists have proposed modifications to general relativity that are more compatible with quantum theory. Under these modified theories, there are subtle differences in the way merged black holes ring down, but observing those differences hasn’t been possible. But a couple of new studies show how we might be able to observe them in the next LIGO run.
The modified Teukolsky equation. Credit: Li, Dongjun, et al
In the first work, the team focused on what is known as the Teukolsky Equation. First proposed by Saul Teukolsky, the equations are an efficient way of analyzing gravitational waves. The equations only apply to classical general relativity, so the team developed a way to modify the equations for modified general relativity models. Since the solutions to both the Teukolsky and modified Teukolsky equations don’t require a massive supercomputer to solve, the team can compare black hole ring downs in various gravitational models.
The second work looks at how this would be done with LIGO data. Rather than focusing on general differences, this work focuses on what is known as the no-hair theorem. General relativity predicts that no matter how two black holes merge, the final merged black hole must be described by only mass, rotation, and charge. It can’t have any “hair”, or remnant features of the collision. In some modified versions of general relativity, black holes can have certain features, which would violate the no-hair theorem. In this second work, the authors show how this could be used to test general relativity against certain modified theories.
LIGO has just begun its latest observation run, so it will be a while before there is enough data to test. But we may soon have a new observational test of Einstein’s old theory, and we might just prove it isn’t the final theory of gravity after all.
Reference: Li, Dongjun, et al. “Perturbations of spinning black holes beyond General Relativity: Modified Teukolsky equation.” Physical Review X 13.2 (2022): 021029.
Reference: Ma, Sizheng, Ling Sun, and Yanbei Chen. “Black hole spectroscopy by mode cleaning.” Physical Review Letters 130.2 (2023): 141401.
The post When Black Holes Merge, They’ll Ring Like a Bell appeared first on Universe Today.
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