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If dark matter exists, then where are the particles?

This single question threatens to topple the standard cosmological model, known as the LCDM model. The CDM stands for cold dark matter, and according to the model makes up nearly 85% of matter in the universe. It should be everywhere, and all around us, and yet every single search for dark matter particles has come up empty. If dark matter particles are real, we know what they are not. We don’t know what they are.

There are lots of ideas, from WIMPs to axions to sterile neutrinos, and none of them have shown up in our detectors. But one of the problems could be that while dark matter particles are everywhere, their particle mass is much higher than we can detect in our particle accelerators and neutrino observatories. If that’s the case, we may never observe them directly. But we might be able to detect the force that allows them to interact.

In particle physics, each fundamental force has one or more carrier bosons. Electromagnetism has the photon, the strong force has the gluons, the weak force has W & Z bosons, the gravitational force the graviton. Dark matter interacts gravitationally, but it also may interact via a dark force, which should have a carrier boson known as the dark photon.

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A hypothetical dark photon interaction. Credit: APS/Alan Stonebraker

Dark photons turn up in a generalization of the standard model of particle physics. According to theory, they would interact with dark matter similar to the way photons interact with charged particles. But just as the weak force and electromagnetism are connected as the electroweak force, this dark force and electromagnetism would be connected as a kind of electrodark force. What this means is that regular photons and dark photons could mix slightly, allowing dark matter to interact with regular matter very slightly. Although photons have no mass, dark photons would have mass. This means they would only interact over very short distances, and could quickly decay into other particles. Like the gluons of the strong force, we can’t observe them directly, but we can observe how they cause particles to interact. This is where a new study on dark photons comes in.

The authors analyze the dark photon model in two ways. The first is to use experimental data to constrain the physical parameters of dark photons, such as their mass and how strongly they mix with regular photons. The second is to compare a particle physics model with and without dark photons to key experimental results. In general, the study finds that the dark photon model is a better fit than the standard model, but it’s a particularly good fit for an experiment known as the anomalous magnetic moment of the gluon, or g-2.

The muon is a heavier sibling of the electron, and like the electron, it has an electric charge and a magnetic moment, or g-factor. The value of the muon g-factor is almost, but not exactly, equal to 2. The “not exactly” part, g – 2, is one of the most precisely measured values in particle physics. It is also one of the most precisely calculated values in particle theory. And they don’t agree.

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Experiment vs theory for g – 2. Credit: Ryan Postel, Fermilab/Muon g-2 collaboration

Experimentally, g-2 = 0.00233184121. Theoretical calculations put g-2 = 0.00233183620. This is known as the g-2 anomaly and is beyond irksome. If you include dark photon interactions, the theoretical result becomes g-2 = 0.00233183939, which is significantly better. Overall, the dark photon model is preferred over the standard model at 6.5 sigma, which is a very strong result.

All of this is very interesting, but we should add a few caveats. The first is

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Starship | Second Flight Test

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On November 18, 2023, Starship successfully lifted off at 7:02 a.m. CT from Starbase on its second integrated flight test.

While it didn’t happen in a lab or on a test stand, it was absolutely a test. What we did with this second flight will provide invaluable data to continue rapidly developing Starship.

The test achieved a number of major milestones, helping us improve Starship’s reliability as SpaceX seeks to make life multiplanetary. The team at Starbase is already working final preparations on the vehicles slated for use in Starship’s third flight test.

Congratulations to the entire SpaceX team on an exciting second flight test of Starship!

Follow us on for continued updates on Starship’s progress

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For its Final Trick, Chandrayaan-3 Brings its Propulsion Module to Earth Orbit

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On August 23, ISRO’s Vikram lander detached from its propulsion module and made a soft landing near the Moon’s south pole region. The lander then deployed its Pragyan rover, and for two weeks the endearing little solar-powered rover performed marvelously, detecting water ice and characterizing the makeup of the lunar regolith before succumbing to the darkness and cold of the lunar night.

But since the rover mission ended, the propulsion module that brought it to the Moon has made a detour, performing a series of complex maneuvers that took it from a tight lunar orbit back to Earth orbit. This was possible because the module still had more than 100 kg of fuel, allowing scientists to conduct additional maneuvers and experiments.

Right now, the propulsion module (PM) is orbiting Earth at an altitude of 115,000 km (71,500 miles), well above geostationary orbit. ISRO said the mission team decided to use the available fuel in the propulsion module to derive additional information for future lunar missions. More specifically, this demonstration gave them the chance to test mission operation strategies for a future sample return mission.

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A graphic of the Chandrayaan-3 lander separating from the propulsion module. Credit: ISRO.

The PM has had a busy and productive mission. While in lunar orbit for about a month, it wasn’t just taking it easy.  After the separation of the lander, the PM operated an on-board experiment, the Spectro-polarimetry of HAbitable Planet Earth (SHAPE) payload, designed to observe the Earth. Specifically, this instrument also provided scientists and engineers experience for future missions and research as its purpose was to study habitable planet-like features of Earth. These observations will be used by ISRO for future studies of exoplanets. Additionally, there was a special operation of the SHAPE payload on October 28, 2023 during the solar eclipse.

But because the spacecraft had such a precise orbit injection and optimal burn maneuvers, the amount of leftover fuel meant the engineers could do even more with the PM than originally expected. The PM was commanded to execute an orbit-raising maneuver at the Moon and then perform a Trans-Earth injection burn, which placed the PM in an Earth-bound orbit.

ISRO said the first orbit raising maneuver at the Moon was performed on October 9, 2023 to raise apolune altitude to 5,112 km from 150 km.  The Trans-Earth injection (TEI) maneuver was performed on October 13, 2023, and as its orbit was slowly raised, the PM made four Moon flybys before departing Moon on November 10.

Currently, propulsion module is orbiting Earth with an orbital period of nearly 13 days, at 27 degrees inclination. Because of this high orbit, ISRO said there is no threat of close approach with any operational Earth orbiting satellites.

ISRO said these extra operations allowed them to plan and execute trajectory maneuvers to return from Moon to Earth, as well as develop software to plan and validate the maneuvers. They also planned and executed a gravity assisted flyby between two celestial bodies and, most notably they avoided an uncontrolled crash into the Moon’s surface at the end of the life of PM, which met the requirements of creating no debris on the Moon.

Will its current high geostationary orbit be the Chandrayaan-3 PM’s final trick? Who knows? The resourceful engineers might figure out another way to make use of this multi-purpose spacecraft.

The post For its Final Trick, Chandrayaan-3 Brings its Propulsion Module to Earth Orbit appeared first on Universe Today.

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In 1872, a Solar Storm Hit the Earth Generating Auroras from the Tropics to the Poles

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Imagine a solar storm generating auroral displays across the entire sky. No, we haven’t quite seen them that strong in the current solar cycle. But, back in February 1872, people around the world reported seeing brilliant northern and southern lights. The culprit? A medium-sized sunspot group that unleased a torrent of charged particles in a coronal mass ejection directed toward Earth.

As with strong space weather storms today, the long-ago event not only sent aurorae dancing across most of Earth’s skies, but it disrupted technology. It affected telegraph communications on the submarine cable in the Indian Ocean between Bombay (Mumbai) and Aden for hours. Similar disturbances were reported on the landline between Cairo and Khartoum. That presaged the damage that such storms can do to today’s power grids and satellite communications.

Nowadays scientists know quite a bit more about the solar activity that causes these storms. Back in those days, however, solar science was still in its infancy. We didn’t have globe-girdling, interconnected communications systems. And, then as now, extremely strong solar storms were relatively rare, but they could still do damage. Today, we are well aware of the threat to modern technologies. Strong solar storms can shut down power stations, stop communications, threaten the world’s financial and trade systems, and harm life. “The longer the power supply could be cut off, the more society, especially those living in urban areas, will struggle to cope,” said Hisashi Hayakawa, the lead author of a group studying ancient solar storms. “Could we maintain our life without such infrastructure? Well, let us just say that it would be extremely challenging.”

Studying an Ancient Solar Storm

The 1872 solar event was named the Chapman-Silverman storm. Recently, an international team of 22 scientists, led by Hayakawa at Nagoya University in Japan, Edward Cliver at the US National Solar Observatory, and Frédéric Clette of the Royal Observatory of Belgium studied it in great detail. Their tools were historical records coupled with modern techniques to assess the Chapman-Silverman storm from its origins on the Sun to its impact on our planet.

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Sketches by Italian astronomer Angelo Secchi (Pontifical Gregorian University). The top shows the disk of the Sun, and the lower images show the 1872 sunspot group in more detail. Courtesy Osservatorio Astronomico di Roma.

How do you go about finding records for a storm that far back? First, you look at sunspot records. People have long sketched sunspot groups and records go back quite far. The team scoured Belgian and Italian records of sunspots during the period. For terrestrial impacts, they used geomagnetic field measurements recorded in places as diverse as Bombay (Mumbai), Tiflis (Tbilisi), and Greenwich. Those gave them insight into the temporal evolution and intensity of the storm. Finally, they examined hundreds of accounts of visual aurorae caused by the storm, written in different languages.

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A Japanese drawing of the aurorae triggered by the 1872 solar event. Courtesy Shounji Temple.

“Our findings confirm the Chapman-Silverman storm in February 1872 as one of the most extreme geomagnetic storms in recent history. Its size rivaled those of the Carrington storm in September 1859 and the NY Railroad storm in May 1921,” Hayakawa said. “This means that we now know that the world has seen at least three geomagnetic superstorms in the last two centuries.
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