For a little over a month now, the Earth has been joined by a new ‘mini-moon.’ The object is an asteroid that has been temporarily accompanying Earth on its journey around the Sun. By 25th November it will have departed but before then, astronomers across the world have been turning their telescopes to study it. A new paper of 2024 PT5 reveals its basaltic nature – similar to volcanic rocks on Earth – with a composition that makes it similar to lunar material. There have been many close encounters to Earth allowing many of its secrets to be unveiled.
The Moon is perhaps one of the most well known astronomical objects. It’s Earth’s only permanent natural satellite and has been in orbit since early in the planet’s history. It lies approximately 384,400 kilometres away and has played a crucial part in stabilising are axial tilt and regulating the climate and seasons. In addition to the Moon we are occasionally joined by asteroids that briefly orbit around the Earth before continuing their journey through the Solar System.
The partial lunar eclipse from October 2023 as seen from Oxfordshire UK. Credit: Mary McIntyre FRAS.2024 PT5 is a small asteroid that has served as a temporary “mini-moon” for Earth, orbiting near the planet for about six weeks. Analysis has revealed that the asteroid spins rapidly, completing one full rotation in under an hour and measures no more than 15 metres across. While it will leave Earth’s vicinity in just a few days, its brief presence has offered valuable insight and data on the properties of near-Earth objects.
Space agencies like NASA and ESA are both exploring commercial space operations to support the growing global space economy. Exploring and mining asteroids is an activity that is well suited to this endeavour. Asteroids like 2024 PT5 which is in close proximity to Earth is well suited to this. The paper that has been published in Astronomy & Astrophysics and was authored by R. de la Fuente Marcos and a team of Spanish astronomers.
The asteroid Dimorphos was captured by NASA’s DART mission just two seconds before the spacecraft struck its surface on Sept. 26, 2022. Observations of the asteroid before and after impact suggest it is a loosely packed “rubble pile” object. Credit: NASA/JHUAPLThe study focussed attention on changes to the short-term orbital properties and used N-body simulations (a technique to simulate a dynamic system under other physical forces such as the force of gravity.) They also explored the spectral class of the asteroid from reflectance spectra analysis obtained with the OSIRIS spectrograph and assessed its rotational properties.
The team confirmed that 2024 PT5 is a natural object (thankfully) that has a spectra which is consisted with the so called Sv-type asteroid, similar to breccia found in the Lunar mare. Assessment of its rotational properties revealed it is completing one rotation in less than an hour. They could not rule out whether the asteroid was tumbling in an erratic fashion, further analysis is needed. Finally through astrometric observations the team concluded that the orbits of 2024 PT5 and 2022 NX1 (another near Earth asteroid which is just 10 metres across) are very similar.
Both ESA and NASA now consider a cost-effective strategy for NEO missions essential with a focus on small body science and planetary defence. The approach includes reusing and active missions and identifying accessible objects like 2022 NX1 and 2024 PT5 using ground-based observatories.
The post Here’s What We Know About Earth’s Temporary Mini-Moon appeared first on Universe Today.
Despite decades of study, black holes are still one of the most puzzling objects in the Universe. As we know from Einstein’s Theory of General Relativity, the gravitational force of these stellar remnants alters the curvature of spacetime around them. This causes gas, dust, and even photons (light) in their vicinity to fall inwards and form disks that slowly accrete onto their faces, never to be seen again. However, astronomers have also noted that they can produce powerful jets that accelerate charged particles to close to the speed of light (aka. relativistic jets).
These jets lead to powerful gamma-ray bursts (GRBs), which have been observed with black holes that have powerful magnetic fields. However, where these magnetic fields come from has remained a mystery to astrophysicists for some time. According to new research led by scientists from the Flatiron Institute, the source of these fields may have finally been revealed. Based on a series of simulations they conducted that modeled the life cycle of stars from birth to collapse, they found that black holes inherit their magnetic fields from the parent stars themselves.
The research was led by Ore Gottlieb, a Research Fellow from the Theoretical High Energy Astrophysics (THEA) group at the Flatiron Institute’s Center for Computational Astrophysics (CCA) and Columbia University’s Astrophysics Laboratory. He was joined by colleagues from the CCA and CAL and researchers from the University of Arizona, the Steward Observatory, and Princeton University. The paper that details their findings was published on November 18th in the Astrophysical Journal Letters.
Infographic explaining how black holes inherit their magnetism. Credit: Lucy Reading-Ikkanda / Simons FoundationBlack holes form from the collapse of proto-neutron stars, which are essentially what remains after massive stars have blown off their outer layers in a supernova explosion. While there have been a few theories about where black holes get their magnetism, none could account for the power of black hole jets or GRBs. Through their simulations, the team initially planned to study outflows from black holes, including the jets that produce GRBs. However, as Gottlieb’s explained in a Simons Foundation press release, the team ran into a problem with the models:
“We were not sure how to model the behavior of these magnetic fields during the collapse of the neutron star to the black hole. So, this was a question that I started to think about for the first time. What had been thought to be the case is that the magnetic fields of collapsing stars are collapsing into the black hole. During this collapse, these magnetic field lines are made stronger as they are compressed, so the density of the magnetic fields become higher.”
The only problem with this theory is that the strong magnetic fields of neutron stars cause them to lose angular momentum (their rotation). Without this, the gas, plasma, and dust surrounding newly formed black holes will not form an accretion disk around them. This, in turn, would prevent black holes from producing the jets and gamma-ray bursts that astronomers have observed. This suggests that previous simulations of collapsing neutron stars didn’t provide a complete picture. Said Gottlieb:
“It appears to be mutually exclusive. You need two things for jets to form: a strong magnetic field and an accretion disk. But a magnetic field acquired by such compression won’t form an accretion disk, and if you reduce the magnetism to the point where the disk can form, then it’s not strong enough to produce the jets. Past simulations have only considered isolated neutron stars and isolated black holes, where all magnetism is lost during the collapse. However, we found that these neutron stars have accretion disks of their own, just like black holes. And so, the idea is that maybe an accretion disk can save the magnetic field of the neutron star. This way, a black hole will form with the same magnetic field lines that threaded the neutron star.”
3D rendering of a rapidly spinning black hole’s accretion disk and a resulting black hole-powered jet. Credit: Ore Gottlieb et al. (2024)The team ran calculations for neutron stars collapsing to form black holes and found that, in most cases, the timescale for black hole disk formation is often shorter than that of the black hole losing its magnetism. In short, before a newly formed black hole swallows a proto-neutron star’s magnetic field, its magnetic field lines become anchored in the neutron star’s surrounding disk passes to the black hole. As Gottlieb characterized it:
“So the disk enables the black hole to inherit a magnetic field from its mother, the neutron star. What we are seeing is that as this black hole forms, the proto-neutron star’s surrounding disk will essentially pin its magnetic lines to the black hole. It’s very exciting to finally understand this fundamental property of black holes and how they power gamma ray bursts — the most luminous explosions in the universe.”
This discovery resolves the long-standing mystery of where black holes get their magnetic fields. It also presents astronomers with new opportunities to study relativistic jets and gamma-ray bursts, one of the most powerful phenomena in the Universe. If confirmed, these results suggest that forming an early accretion disk is the only thing needed for powerful jets to emerge. Gottlieb and his team are excited to test this theory with future observations.
Further Reading: Simons Foundation, Astrophysical Journal Letters
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74 million kilometres is a huge distance from which to observe something. But 74 million km isn’t such a big deal when the object is the Sun.
That’s how far away from the Sun the ESA/NASA Solar Orbiter was when it captured these new images.
The Solar Orbiter was launched in 2020 to investigate the Sun. It’s studying the mechanism behind the Sun’s solar wind, the complex dynamics of its magnetic field, and eruptions like solar flares and coronal mass ejections. That’s just a sampling of its science goals.
One item on the mission’s long list of objectives is high-resolution images of the Sun’s surface. For that, the spacecraft carries different imagers that operate in different wavelengths. This allows the spacecraft to almost peel back the Sun’s layers and uncover relationships between them.
The ESA has released four new images of the Sun, each one giving us a different look at our star: visible light, magnetic, plasma, and UV. These images were captured with the Polarimetric and Helioseismic Imager (PHI-German contribution) and Extreme Ultraviolet Imager (EUI-Belgian contribution) instruments in March 2023. Each image is a composite of 25 images, all captured on the same day. They’re the highest resolution images of the Sun ever taken.
The images are remarkable for their detail. This image shows sunspots, regions that are darker and cooler than their surroundings. They appear where magnetic field lines are concentrated. The magnetic flux inhibits convection. Image Credit: ESAAccording to Daniel Müller, Solar Orbiter’s Project Scientist, the Sun’s magnetic field is key to understanding the star.
“The Sun’s magnetic field is key to understanding the dynamic nature of our home star from the smallest to the largest scales. These new high-resolution maps from Solar Orbiter’s PHI instrument show the beauty of the Sun’s surface magnetic field and flows in great detail. At the same time, they are crucial for inferring the magnetic field in the Sun’s hot corona, which our EUI instrument is imaging,” Müller said.
This magnetic map of the Sun from the Solar Orbiter shows how magnetic field lines and sunspots are correlated. Image Credit: ESA.The Solar Orbiter’s PHI instrument also gives us a map of how plasma is moving around on the Sun’s surface. Blue regions are moving toward the Orbiter, while red regions are moving away.
The map of plasma movement clearly reflects the rotation of the Sun, with blue regions moving toward the orbiter and red regions moving away. However, it also shows how material is disoriented around the sunspots. Image Credit: ESAThe ultraviolet image of the Sun from the Solar Orbiter’s EUI instrument is probably the most visually stunning. It shows what’s happening above the photosphere, where glowing plasma extends out from sunspots. The plasma is superheated and follows the same magnetic lines that encourage the sunspots.
The Sun’s superheated plasma follow magnetic field lines and extends beyond the photosphere in the same regions the sunspots occur. Image Credit: ESAThe Solar Orbiter’s images are truly extraordinary. It’s easy to lose yourself in them, and to wonder about Life, the Universe, Nature, Evolution, How Everything Came to Be, and your own mortality in the face of it all.
Go ahead and lose yourself in these images for a while. The economy won’t grind to halt if you take a few moments. Image Credit: ESANow, back to your cubicle.
The post Gaze at New Pictures of the Sun from Solar Orbiter appeared first on Universe Today.
I was working on a post in a desultory manner but decided to wait until tomorrow. Plus it’s snowing fairly heavily in Chicago so everything is a big mess of sloppy ice water.
BUT: this is excellent news if you have any neurons (click to read):
The NYT:
Matt Gaetz, President-elect Donald J. Trump’s contentious choice for attorney general who had faced a torrent of scrutiny, said on Thursday that he was withdrawing from consideration for the role.
“It is clear that my confirmation was unfairly becoming a distraction to the critical work of the Trump/Vance Transition,” Mr. Gaetz wrote on X. “There is no time to waste on a needlessly protracted Washington scuffle.”
Mr. Gaetz, who visited with Republican senators on Wednesday to help make a case for his selection, said in the post that the meetings were “excellent,” and that “momentum was strong.” But he added that “Trump’s DOJ must be in place and ready on Day 1,” referring to the Justice Department.
He added, “I remain fully committed to see that Donald J. Trump is the most successful President in history. I will forever be honored that President Trump nominated me to lead the Department of Justice and I’m certain he will Save America.”
Mr. Gaetz was under investigation by the House Ethics Committee for sexual misconduct until he resigned from the House on Nov. 13, after Mr. Trump announced his intention to nominate him.
Mr. Trump, in a social media post, said he appreciated Mr. Gaetz’s attempts to win over senators and be confirmed as attorney general, adding that he thought Mr. Gaetz “was doing very well but, at the same time, did not want to be a distraction for the administration.”
House Republicans voted yesterday to block the Ethics Committee report on Gaetz, but the momentum for withdrawal was strong. I am glad because I always thought that Gaetz had the greatest potential to harm America among all the cabinet members, followed by Pete Hegseth (Trump’s choice for Secretary of Defense), and Robert F. Kennedy, Jr. (proposed Secretary of Health and human services.
One down, two to go.