ERIK MARTIN WILLÈN: August 2022

Wednesday, August 31, 2022

DART Team Confirms Orbit of Targeted Asteroid - UNIVERSE

On the night of July 7, 2022, the Lowell Discovery Telescope near Flagstaff, Arizona captured this sequence in which the asteroid Didymos, located near the center of the screen, moves across the night sky. The sequence is sped up by about 900 times. Scientists used this and other observations from the July campaign to confirm Dimorphos’ orbit and anticipated location at the time of DART’s impact. Credits: Lowell Observatory/N. Moskovitz

See animation

Using some of the world’s most powerful telescopes, the DART investigation team last month completed a six-night observation campaign to confirm earlier calculations of the orbit of Dimorphos—DART’s asteroid target—around its larger parent asteroid, Didymos, confirming where the asteroid is expected to be located at the time of impact. DART, which is the world’s first attempt to change the speed and path of an asteroid’s motion in space, tests a method of asteroid deflection that could prove useful if such a need arises in the future for planetary defense.

“The measurements the team made in early 2021 were critical for making sure that DART arrived at the right place and the right time for its kinetic impact into Dimorphos,” said Andy Rivkin, the DART investigation team co-lead at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Maryland. “Confirming those measurements with new observations shows us that we don’t need any course changes and we’re already right on target.”

However, understanding the dynamics of Dimorphos’ orbit is important for reasons beyond ensuring DART’s impact. If DART succeeds in altering Dimorphos’ path, the moonlet will move closer toward Didymos, shortening the time it takes to orbit it. Measuring that change is straightforward, but scientists need to confirm that nothing other than the impact is affecting the orbit. This includes subtle forces such as radiation recoil from the asteroid’s Sun-warmed surface, which can gently push on the asteroid and cause its orbit to change.

“The before-and-after nature of this experiment requires exquisite knowledge of the asteroid system before we do anything to it,” said Nick Moskovitz, an astronomer with Lowell Observatory in Flagstaff, Arizona, and co-lead of the July observation campaign. “We don’t want to, at the last minute, say, ‘Oh, here’s something we hadn’t thought about or phenomena we hadn’t considered.’ We want to be sure that any change we see is entirely due to what DART did.”

In late September to early October, around the time of DART’s impact, Didymos and Dimorphos will make their closest approach to Earth in recent years at approximately 6.7 million miles (10.8 million kilometers) away. Since March 2021 the Didymos system had been out of range of most ground-based telescopes because of its distance from Earth, but early this July the DART Investigation Team employed powerful telescopes in Arizona and Chile — the Lowell Discovery Telescope at Lowell Observatory, the Magellan Telescope at Las Campanas Observatory and the Southern Astrophysical Research (SOAR) Telescope — to observe the asteroid system and look for changes in its brightness. These changes, called “mutual events,” occur when one of the asteroids passes in front of the other because of Dimorphos’ orbit, blocking some of the light they emit.

“It was a tricky time of year to get these observations,” said Moskovitz. In the Northern Hemisphere, the nights are short, and it is monsoon season in Arizona. In the Southern Hemisphere, the threat of winter storms loomed. In fact, just after the observation campaign, a snowstorm hit Chile, prompting evacuations from the mountain where SOAR is located. The telescope was then shut down for close to ten days. “We asked for six half-nights of observation with some expectation that about half of those would be lost to weather, but we only lost one night. We got really lucky.”

In all, the team was able to extract from the data the timing of 11 new mutual events. Studying those changes in brightness enabled scientists to determine precisely how long it takes Dimorphos to orbit the larger asteroid and thereby predict where Dimorphos will be located at specific moments in time, including when DART makes impact. The results were consistent with previous calculations.

“We really have high confidence now that the asteroid system is well understood and we are set up to understand what happens after impact,” Moskovitz said.

Not only did this observation campaign enable the team to confirm Dimorphos’ orbital period and expected location at time of impact, but it also allowed team members to refine the process they will use to determine whether DART successfully changed Dimorphos’s orbit post-impact, and by how much.

In October, the team will again use ground-based telescopes around the world to look for mutual events and calculate Dimorphos’ new orbit, expecting that the time it takes the smaller asteroid to orbit Didymos will have shifted by several minutes. These observations will also help constrain theories that scientists around the world have put forward about Dimorphos’ orbit dynamics and the rotation of both asteroids.

Johns Hopkins APL manages the DART mission for NASA's Planetary Defense Coordination Office as a project of the agency’s Planetary Missions Program Office. DART is the world's first planetary defense test mission, intentionally executing a kinetic impact into Dimorphos to slightly change its motion in space. While neither asteroid poses a threat to Earth, the DART mission will demonstrate that a spacecraft can autonomously navigate to a kinetic impact on a relatively small target asteroid and that this is a viable technique to deflect an asteroid on a collision course with Earth if one is ever discovered. DART will reach its target on Sept. 26, 2022.

For more information about the DART mission, visit: https://www.nasa.gov/dartmission

Source: DART Team Confirms Orbit of Targeted Asteroid | NASA

Brains cells born together wire and fire together for life

Brain cells with the same “birthdate” are more likely to wire together into cooperative signaling circuits that carry out many functions, including the storage of memories, a new study finds.

Led by researchers from NYU Grossman School of Medicine, the new study on the brains of mice developing in the womb found that brain cells (neurons) with the same birthdate showed distinct connectivity and activity throughout the animals’ adult lives, whether they were asleep or awake.

Published online August 22 in Nature Neuroscience, the findings suggest that evolution took advantage of the orderly birth of neurons — by gestational day — to form localized microcircuits in the hippocampus, the brain region that forms memories. Rather than attempting to create each new memory from scratch, the researchers suggest, the brain may exploit the stepwise formation of neuronal layers to establish neural templates, like “Lego pieces,” that match each new experience to an existing template as it is remembered.

These rules of circuit assembly would suggest that cells born together are more likely to encode memories together, and to fail together, potentially implicating neuronal birthdate in diseases like autism and Alzheimer’s, say the authors. With changes to the number of cells born at different days, the developing brain may be more vulnerable on some gestational days to viral infections, toxins, or alcohol.

“Our study’s results suggest that which day a hippocampal neuron is born strongly influences both how that single cell performs, and how populations of such cells signal together throughout life,” says senior study author György Buzsáki, MD, PhD, the Biggs Professor in the Department of Neuroscience and Physiology at NYU Langone Health. “This work may reshape how we study neurodevelopmental disorders, which have traditionally been looked at through a molecular or genetic, rather than a developmental, lens,” says Buzsáki, also a faculty member in the Neuroscience Institute at NYU Langone.”

New Understanding

The current study’s innovation rests on tracking the activity of neurons of a given birthdate into adulthood. To accomplish this, the researchers relied on a technique that allowed them to transfer DNA into cells that were undergoing division into neurons in the womb. The DNA expressed markers that tagged brain cells that were born on same day, akin to a barcode. This labeling method then enabled the researchers to study these neurons in the adult animal.

Using a combination of techniques, the new study found that neurons of the same birthdate tend to “co-fire” together, characterized by synchronized swings in their positive and negative charges, allowing them to transmit electrical signals collectively. A likely reason for the co-firing, say the authors, is that neurons with the same birthdate are connected via shared neurons.

Past work had shown that activity in the hippocampus can be described in terms patterns of collective neuronal activity during waking and sleep. During sleep, for instance, when each day’s memories are consolidated for long-term memory storage, hippocampal neurons engage in a cyclical burst of activity called the “sharp wave-ripple,” named for the shape it takes when captured graphically by EEG, a technology that records brain activity with electrodes.

“Our results show that neurons born on the same day become part of the same cooperating assemblies, and participate in the same sharp wave-ripples and represent the same memories,” says first author Roman Huszár, a graduate student in Buzsáki’s lab. “These relationships, and the pre-set templates they encode, have a key implication for hippocampal function: the storage of a memory about a place or event.”

Moving forward, the team plans additional experiments to identify the genes active in the same birthdate neurons in different brain regions, and to test their role in memory formation and behavior.

Source: https://nyulangone.org/news/brain-cells-born-together-wire-fire-together-life

Journal article: https://www.nature.com/articles/s41593-022-01138-x

Source: Brains cells born together wire and fire together for life – Scents of Science (myfusimotors.com)

HOUSE OF THE DRAGON Cast Breaks Down The Pilot Episode 1 | Full Spoiler Aftershow With Matt Smith - STREAM WARS

Funny and Weird Clips (2745)

Tuesday, August 30, 2022

NASA’s Lucy Team Discovers Moon Around Asteroid Polymele - UNIVERSE

Even before its launch, NASA’s Lucy mission was already on track to break records by visiting more asteroids than any previous mission. Now, after a surprise result from a long-running observation campaign, the mission can add one more asteroid to the list.

On March 27, Lucy’s science team discovered that the smallest of the mission’s Trojan asteroid targets, Polymele, has a satellite of its own. On that day, Polymele was expected to pass in front of a star, allowing the team to observe the star blink out as the asteroid briefly blocked, or occulted, it. By spreading 26 teams of professional and amateur astronomers across the path where the occultation would be visible, the Lucy team planned to measure the location, size, and shape of Polymele with unprecedented precision while it was outlined by the star behind it. These occultation campaigns have been enormously successful in the past, providing valuable information to the mission on its asteroid targets, but this day would hold a special bonus.

A graphic showing the observed separation of asteroid Polymele from its discovered satellite. Credits: NASA's Goddard Space Flight Center

We were thrilled that 14 teams reported observing the star blink out as it passed behind the asteroid, but as we analyzed the data, we saw that two of the observations were not like the others,” said Marc Buie, Lucy occultation science lead at the Southwest Research Institute, which is headquartered in San Antonio. “Those two observers detected an object around 200 km (about 124 miles) away from Polymele. It had to be a satellite.”

Using the occultation data, the team assessed that this satellite is roughly 3 miles (5 km) in diameter, orbiting Polymele, which is itself around 17 miles (27 km) along its widest axis. The observed distance between the two bodies was about 125 miles (200 km). Following planetary naming conventions, the satellite will not be given an official name until the team can determine its orbit. As the satellite is too close to Polymele to be clearly seen by Earth-based or Earth-orbiting telescopes – without the help of a fortuitously positioned star – that determination will have to wait until either the team gets lucky with future occultation attempts or until Lucy approaches the asteroid in 2027. At the time of the observation Polymele was 480 million miles (770 million km) from Earth. Those distances are roughly equivalent to finding a quarter on a sidewalk in Los Angeles – while trying to spot it from a skyscraper in Manhattan.

Asteroids hold vital clues to deciphering the history of the solar system – perhaps even the origins of life – and solving these mysteries is a high priority for NASA. The Lucy team originally planned to visit one main belt asteroid and six Trojan asteroids, a previously unexplored population of asteroids that lead and follow Jupiter in its orbit around the Sun. In January of 2021, the team used the Hubble Space Telescope to discover that one of the Trojan asteroids, Eurybates, has a small satellite. Now with this new satellite, Lucy is on track to visit nine asteroids on this incredible 12-year voyage.

“Lucy’s tagline started out: 12 years, seven asteroids, one spacecraft,” said Lucy program scientist Tom Statler at NASA Headquarters in Washington. “We keep having to change the tagline for this mission, but that’s a good problem to have.”

Lucy’s principal investigator is based out of the Boulder, Colorado, branch of Southwest Research Institute, headquartered in San Antonio, Texas. NASA’s Goddard Space Flight Center in Greenbelt, Maryland, provides overall mission management, systems engineering, and safety and mission assurance. Lockheed Martin Space in Littleton, Colorado, built the spacecraft. Lucy is the 13th mission in NASA’s Discovery Program. NASA’s Marshall Space Flight Center in Huntsville, Alabama, manages the Discovery Program for the agency’s Science Mission Directorate in Washington.

For more information about NASA's Lucy mission, visit: https://www.nasa.govl/lucy

Banner Image: The asteroid Polymele, illustrated here, was recently discovered to have a small satellite of its own by NASA's Lucy team. Illustration Credit: NASA's Goddard Space Flight Center

By Katherine Kretke Southwest Research Institute

Source: NASA’s Lucy Team Discovers Moon Around Asteroid Polymele | NASA

NASA Engineer Develops Tiny, High-Powered Laser to Find Water on the Moon - Science Instruments

Berhanu Bulcha shows off his terahertz laser technology in his lab at NASA’s GoddardSpace Flight Center in Greenbelt, Md. Credits: NASA/Michael Giunto

Finding water on the Moon could be easier with a Goddard technology that uses an effect called quantum tunneling to generate a high-powered terahertz laser, filling a gap in existing laser technology.

Locating water and other resources is a NASA priority crucial to exploring Earth’s natural satellite and other objects in the solar system and beyond. Previous experiments inferred, then confirmed the existence of small amounts of water across the Moon. However, most technologies do not distinguish among water, free hydrogen ions, and hydroxyl, as the broadband detectors used cannot distinguish between the different volatiles.

Goddard engineer Dr. Berhanu Bulcha said a type of instrument called a heterodyne spectrometer could zoom in on particular frequencies to definitively identify and locate water sources on the Moon. It would need a stable, high-powered, terahertz laser, which was prototyped in collaboration with Longwave Photonics through NASA’s Small Business Innovation Research (SBIR) program.

“This laser allows us to open a new window to study this frequency spectrum,” he said. “Other missions found hydration on the Moon, but that could indicate hydroxyl or water. If it’s water, where did it come from? Is it indigenous to the formation of the Moon, or did it arrive later by comet impacts? How much water is there? We need to answer these questions because water is critical for survival and can be used to make fuel for further exploration.”

As the name implies, spectrometers detect spectra or wavelengths of light in order to reveal the chemical properties of matter that light has touched. Most spectrometers tend to operate across broad sections of the spectrum. Heterodyne instruments dial in to very specific light frequencies such as infrared or terahertz. Hydrogen-containing compounds like water emit photons in the terahertz frequency range — 2 trillion to 10 trillion cycles per second — between microwave and infrared.

Like a microscope for subtle differences within a bandwidth like terahertz, heterodyne spectrometers combine a local laser source with incoming light. Measuring the difference between the laser source and the combined wavelength provides accurate readings between sub-bandwidths of the spectrum.

Traditional lasers generate light by exciting an electron within an atom’s outer shell, which then emits a single photon as it transitions, or returns to its resting energy level. Different atoms produce different frequencies of light based on the fixed amount of energy it takes to excite one electron. However, lasers fall short in a particular portion of the spectrum between infrared and microwave known as the terahertz gap.

“The problem with existing laser technology,” Dr. Bulcha said, “is that no materials have the right properties to produce a terahertz wave.”

Electromagnetic oscillators like those that generate radio or microwave frequencies produce low-powered terahertz pulses by using a series of amplifiers and frequency multipliers to extend the signal into the terahertz range. However, this process consumes a lot of voltage, and the materials used to amplify and multiply the pulse have limited efficiency. This means they lose power as they approach the terahertz frequencies.

From the other side of the terahertz gap, optical lasers pump energy into a gas to generate photons. However, high-powered, terahertz-band lasers are large, power hungry, and not suitable for space exploration purposes where mass and power are limited, particularly hand-held or Small Satellite applications. The power of the pulse also drops as optical lasers push towards the terahertz bandwidths.

This tiny laser capitalizes on quantum-scale effects of materials just tens of atoms across to generate a high-powered beam in a portion of the spectrum where traditional lasers fade in strength. Credits: NASA/Michael Giunto

To fill that gap, Dr. Bulcha’s team is developing quantum cascade lasers that produce photons from each electron transition event by taking advantage of some unique, quantum-scale physics of materials layered just a few atoms thick.

In these materials, a laser emits photons in a specific frequency determined by the thickness of alternating layers of semiconductors rather than the elements in the material. In quantum physics, the thin layers increase the chance that a photon can then tunnel through to the next layer instead of bouncing off the barrier. Once there, it excites additional photons. Using a generator material with 80 to 100 layers, totaling less than 10 to 15 microns thick, the team’s source creates a cascade of terahertz-energy photons.

This cascade consumes less voltage to generate a stable, high-powered light. One drawback of this technology is its beam spreads out in a large angle, dissipating quickly over short distances. Using innovative technology supported by Goddard’s Internal Research and Development (IRAD) funding, Dr. Bulcha and his team integrated the laser on a waveguide with a thin optical antenna to tighten the beam. The integrated laser and waveguide unit reduces this dissipation by 50% in a package smaller than a quarter.

He hopes to continue the work to make a flight-ready laser for NASA’s Artemis program.

The laser’s low size and power consumption allow it to fit in a 1U CubeSat, about the size of a teapot, along with the spectrometer hardware, processor, and power supply. It could also power a handheld device for use by future explorers on the Moon, Mars, and beyond.

By Karl B. Hille NASA’s Goddard Space Flight Center in Greenbelt, Md.

Source: Tiny, High-Powered Laser to Find Water on the Moon | NASA