NASA Astronomy Picture of the Day

October 3, 2024

Eclipse at Sunrise

The second solar eclipse of 2024 began in the Pacific. On October 2nd the Moon's shadow swept from west to east, with an annular eclipse visible along a narrow antumbral shadow path tracking mostly over ocean, crossing land near the southern tip of South America, and ending in the southern Atlantic. The dramatic total annular eclipse phase is known to some as a ring of fire. Still, a partial eclipse of the Sun was experienced over a wide region. Captured at one of its earliest moments, October's eclipsed Sun is seen just above the clouds near sunrise in this snapshot. The partially eclipsed solar disk is close to the maximum eclipse as seen from Mauna Kea Observatory Visitor Center, Island of Hawaii, planet Earth.

https://apod.nasa.gov/apod/astropix.html

NASA’s LRO: Lunar Ice Deposits are Widespread

Oct 03, 2024

Deposits of ice in lunar dust and rock (regolith) are more extensive than previously thought, according to a new analysis of data from NASA’s LRO (Lunar Reconnaissance Orbiter) mission.

Ice would be a valuable resource for future lunar expeditions. Water could be used for radiation protection and supporting human explorers, or broken into its hydrogen and oxygen components to make rocket fuel, energy, and breathable air.

Prior studies found signs of ice in the larger permanently shadowed regions (PSRs) near the lunar South Pole, including areas within Cabeus, Haworth, Shoemaker and Faustini craters.

In the new work, “We find that there is widespread evidence of water ice within PSRs outside the South Pole, towards at least 77 degrees south latitude,” said Dr. Timothy P. McClanahan of NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and lead author of a paper on this research published October 2 in the Planetary Science Journal.

The study further aids lunar mission planners by providing maps and identifying the surface characteristics that show where ice is likely and less likely to be found, with evidence for why that should be.

“Our model and analysis show that greatest ice concentrations are expected to occur near the PSRs’ coldest locations below 75 Kelvin (-198°C or -325°F) and near the base of the PSRs’ poleward-facing slopes,” said McClanahan.

“We can’t accurately determine the volume of the PSRs’ ice deposits or identify if they might be buried under a dry layer of regolith.

However, we expect that for each surface 1.2 square yards (square meter) residing over these deposits there should be at least about five more quarts (five more liters) of ice within the surface top 3.3 feet (meter), as compared to their surrounding areas,” said McClanahan.

The study also mapped where fewer, smaller, or lower-concentration ice deposits would be expected, occurring primarily towards warmer, periodically illuminated areas.

Ice could become implanted in lunar regolith through comet and meteor impacts, released as vapor (gas) from the lunar interior, or be formed by chemical reactions between hydrogen in the solar wind and oxygen in the regolith.

PSRs typically occur in topographic depressions near the lunar poles. Because of the low Sun angle, these areas haven’t seen sunlight for up to billions of years, so are perpetually in extreme cold.

Ice molecules are thought to be repeatedly dislodged from the regolith by meteorites, space radiation, or sunlight and travel across the lunar surface until they land in a PSR where they are entrapped by extreme cold.

The PSR’s continuously cold surfaces can preserve ice molecules near the surface for perhaps billions of years, where they may accumulate into a deposit that is rich enough to mine. Ice is thought to be quickly lost on surfaces that are exposed to direct sunlight, which precludes their accumulations.

The team used LRO’s Lunar Exploration Neutron Detector (LEND) instrument to detect signs of ice deposits by measuring moderate-energy, “epithermal” neutrons.

Specifically, the team used LEND’s Collimated Sensor for Epithermal Neutrons (CSETN) that has a fixed 18.6-mile (30-kilometer) diameter field-of-view.

Neutrons are created by high-energy galactic cosmic rays that come from powerful deep-space events such as exploding stars, that impact the lunar surface, break up regolith atoms, and scatter subatomic particles called neutrons.

The neutrons, which can originate from up to about a 3.3-foot (meter’s) depth, ping-pong their way through the regolith, running into other atoms. Some get directed into space, where they can be detected by LEND.

Since hydrogen is about the same mass as a neutron, a collision with hydrogen causes the neutron to lose relatively more energy than a collision with most common regolith elements.

So, where hydrogen is present in regolith, its concentration creates a corresponding reduction in the observed number of moderate-energy neutrons.

“We hypothesized that if all PSRs have the same hydrogen concentration, then CSETN should proportionally detect their hydrogen concentrations as a function of their areas. So, more hydrogen should be observed towards the larger-area PSRs,” said McClanahan.

The model was developed from a theoretical study that demonstrated how similarly hydrogen-enhanced PSRs would be detected by CSETNs fixed-area field-of-view.

The correlation was demonstrated using the neutron emissions from 502 PSRs with areas ranging from 1.5 square miles (4 km2) to 417 square miles (1079 km2) that contrasted against their surrounding less hydrogen-enhanced areas.

The correlation was expectedly weak for the small PSRs but increased towards the larger-area PSRs.

https://science.nasa.gov/solar-system/moon/nasas-lro-lunar-ice-deposits-are-widespread/

Gateway Stands Tall for Stress Test

Oct 03, 2024

Gateway space station’s Habitation and Logistics Outpost has successfully completed static load testing in Turin, Italy.

With this phase of stress testing complete, the module is one step closer to final outfitting ahead of launch to lunar orbit.

Major Gateway hardware recently crossed an important testing milestone on its path to launch to the Moon, where it will support new science and house astronauts in lunar orbit.

Gateway’s HALO (Habitation and Logistics Outpost) successfully completed static load testing, a rigorous stress test of how well the structure responds to the forces encountered in deep space.

Thales Alenia Space, subcontractor to Northrop Grumman, conducted the testing in Turin, Italy.

Static load testing is one of the major environmental stress tests HALO will undergo, and once all phases of testing are complete, the module will be ready to move from Italy to Gilbert, Arizona, where Northrop Grumman will complete final outfitting.

HALO is one of four pressurized Gateway modules where astronauts will live, conduct science, and prepare for missions to the lunar South Pole region.

It will launch with Gateway’s Power and Propulsion Element on a SpaceX Falcon Heavy rocket to lunar orbit.

Gateway is humanity’s first lunar space station supporting a new era of exploration and scientific discovery as part of NASA’s Artemis campaign that will establish a sustained presence on and around the Moon, paving the way for the first crewed mission to Mars.

https://www.nasa.gov/missions/artemis/gateway/gateway-stands-tall-for-stress-test/

NASA Prepares for Lunar Terrain Vehicle Testing

Oct 02, 2024

When astronauts return to the Moon as part of NASA’s Artemis campaign, they will benefit from having a human-rated unpressurized LTV (Lunar Terrain Vehicle) that will allow them to explore more of the lunar surface, enabling diverse scientific discoveries.

As crewed Artemis missions near, engineers at NASA’s Johnson Space Center in Houston are designing an unpressurized rover prototype, known as the Ground Test Unit.

The test unit will employ a flexible architecture to simulate and evaluate different rover concepts for use beginning with Artemis V.

In April 2024, as part of the Lunar Terrain Vehicle Services contract, NASA selected three vendors — Intuitive Machines, Lunar Outpost, and Venturi Astrolab — to supply rover capabilities for use by astronauts on the lunar surface.

While the test unit will never go to the Moon, it will support the development of additional rover prototypes that will enable NASA and the three companies to continue making progress until one of the providers comes online.

Additionally, data provided from GTU testing helps inform both NASA and the commercial companies as they continue evolving their rover designs as it serves as an engineering testbed for the LTV providers to test their technologies on crew compartment design, rover maintenance, and payload science integration, to name a few.

“The Ground Test Unit will help NASA teams on the ground, test and understand all aspects of rover operations on the lunar surface ahead of Artemis missions,” said Jeff Somers, engineering lead for the Ground Test Unit.

“The GTU allows NASA to be a smart buyer, so we are able to test and evaluate rover operations while we work with the LTVS contractors and their hardware.”

The LTVS contractors have requirements that align with the existing GTU capabilities.

As with the test unit, the vendor-developed, LTV should support up to two crewmembers, have the ability to be operated remotely, and can implement multiple control concepts such as drive modes, self-leveling, and supervised autonomy.

Having a NASA prototype of the vehicle we will drive on the Moon, here on Earth, allows many teams to test capabilities while also getting hands-on engineering experience developing rover hardware.

NASA has built some next generation rover concept vehicles following the successes of the agency’s Apollo Lunar Roving Vehicle in the 1970s, including this iteration of the GTU.

Crewed test vehicles here on Earth like the GTU help NASA learn new ways that astronauts can live and work safely and productively on the Moon, and one day on the surface of Mars.

As vendor designs evolve, the contracted LTV as well as the GTU allow for testing before missions head to the Moon.

The vehicles on the ground also allow NASA to reduce some risks when it comes to adapting new technologies or specific rover design features.

Human surface mobility helps increase the exploration footprint on the lunar surface allowing each mission to conduct more research and increase the value to the scientific community.

Through Artemis, NASA will send astronauts – including the first woman, first person of color, and its first international partner astronaut – to explore the Moon for scientific discovery, technology evolution, economic benefits, and to build the foundation for future crewed missions to Mars.

https://www.nasa.gov/humans-in-space/nasa-prepares-for-lunar-terrain-vehicle-testing/

https://www.nasa.gov/extravehicular-activity-and-human-surface-mobility/https://www.nasa.gov/extravehicular-activity-and-human-surface-mobility/

Via NASA Plane, Scientists Find New Gamma-ray Emission in Storm Clouds

Oct 02, 2024

There’s more to thunderclouds than rain and lightning. Along with visible light emissions, thunderclouds can produce intense bursts of gamma rays, the most energetic form of light, that last for millionths of a second.

The clouds can also glow steadily with gamma rays for seconds to minutes at a time.

Researchers using NASA airborne platforms have now found a new kind of gamma-ray emission that’s shorter in duration than the steady glows and longer than the microsecond bursts.

They’re calling it a flickering gamma-ray flash. The discovery fills in a missing link in scientists’ understanding of thundercloud radiation and provides new insights into the mechanisms that produce lightning.

The insights, in turn, could lead to more accurate lightning risk estimates for people, aircraft, and spacecraft.

Researchers from the University of Bergen in Norway led the study in collaboration with scientists from NASA’s Marshall Space Flight Center in Huntsville, Alabama, and NASA's Goddard Space Flight Center in Greenbelt, Maryland, the U.S. Naval Research Laboratory, and multiple universities in the U.S., Mexico, Colombia, and Europe.

The findings were described in a pair of papers in Nature, published Oct. 2.

The international research team made their discovery while flying a battery of detectors aboard a NASA ER-2 research aircraft. In July 2023, the ER-2 set out on a series of 10 flights from MacDill Air Force Base in Tampa, Florida.

The plane flew figure-eight flight patterns a few miles above tropical thunderclouds in the Caribbean and Central America, providing unprecedented views of cloud activity.

The scientific payload was developed for the Airborne Lightning Observatory for Fly’s Eye Geostationary Lightning Mapper Simulator and Terrestrial Gamma-ray Flashes (ALOFT) campaign.

Instrumentation in the payload included weather radars along with multiple sensors for measuring gamma rays, lightning flashes, and microwave emissions from clouds.

The researchers had hoped ALOFT instruments would observe fast radiation bursts known as terrestrial gamma-ray flashes (TGFs).

The flashes, first discovered in 1992 by NASA’s Compton Gamma Ray Observatory spacecraft, accompany some lightning strikes and last only millionths of a second.

Despite their high intensity and their association with visible lightning, few TGFs have been spotted during previous aircraft-based studies.

“I went to a meeting just before the ALOFT campaign,” said principal investigator Nikolai Østgaard, a space physicist with the University of Bergen.

“And they asked me: ‘How many TGFs are you going to see?’ I said: ‘Either we’ll see zero, or we’ll see a lot.’ And then we happened to see 130.”

However, the flickering gamma-ray flashes were a complete surprise.

“They’re almost impossible to detect from space,” said co-principal investigator Martino Marisaldi, who is also a University of Bergen space physicist.

“But when you are flying at 20 kilometers [12.5 miles] high, you're so close that you will see them.”

The research team found more than 25 of these new flashes, each lasting between 50 to 200 milliseconds.

The abundance of fast bursts and the discovery of intermediate-duration flashes could be among the most important thundercloud discoveries in a decade or more, said University of New Hampshire physicist Joseph Dwyer, who was not involved in the research.

“They’re telling us something about how thunderstorms work, which is really important because thunderstorms produce lightning that hurts and kills a lot of people.”

More broadly, Dwyer said he is excited about the prospects of advancing the field of meteorology.

“I think everyone assumes that we figured out lightning a long time ago, but it’s an overlooked area … we don’t understand what’s going on inside those clouds right over our heads.”

The discovery of flickering gamma-ray flashes may provide crucial clues scientists need to understand thundercloud dynamics, he said.

Turning to aircraft-based instrumentation rather than satellites ensured a lot of bang for research bucks, said the study’s project scientist, Timothy Lang of NASA’s Marshall Space Flight Center in Huntsville, Alabama.

“If we had gotten one flash, we would have been ecstatic — and we got well over 100,” he said. This research could lead to a significant advance in our understanding of thunderstorms and radiation from thunderstorms.

“It shows that if you have the right problem and you're willing to take a little bit of risk, you can have a huge payoff.”

https://science.nasa.gov/earth/via-nasa-plane-scientists-find-new-gamma-ray-emission-in-storm-clouds/

https://www.nasa.gov/missions/tess/nasas-tess-spots-record-breaking-stellar-triplets/

https://iopscience.iop.org/article/10.3847/1538-4357/ad7368

NASA’s TESS Spots Record-Breaking Stellar Triplets

Oct 02, 2024

Professional and amateur astronomers teamed up with artificial intelligence to find an unmatched stellar trio called TIC 290061484, thanks to cosmic “strobe lights” captured by NASA’s TESS (Transiting Exoplanet Survey Satellite).

The system contains a set of twin stars orbiting each other every 1.8 days, and a third star that circles the pair in just 25 days.

The discovery smashes the record for shortest outer orbital period for this type of system, set in 1956, which had a third star orbiting an inner pair in 33 days.

“Thanks to the compact, edge-on configuration of the system, we can measure the orbits, masses, sizes, and temperatures of its stars,” said Veselin Kostov, a research scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and the SETI Institute in Mountain View, California.

“And we can study how the system formed and predict how it may evolve.”

A paper, led by Kostov, describing the results was published in The Astrophysical Journal Oct. 2.

Flickers in starlight helped reveal the tight trio, which is located in the constellation Cygnus. The system happens to be almost flat from our perspective.

This means the stars each cross right in front of, or eclipse, each other as they orbit. When that happens, the nearer star blocks some of the farther star’s light.

Using machine learning, scientists filtered through enormous sets of starlight data from TESS to identify patterns of dimming that reveal eclipses.

Then, a small team of citizen scientists filtered further, relying on years of experience and informal training to find particularly interesting cases.

These amateur astronomers, who are co-authors on the new study, met as participants in an online citizen science project called Planet Hunters, which was active from 2010 to 2013.

The volunteers later teamed up with professional astronomers to create a new collaboration called the Visual Survey Group, which has been active for over a decade.

“We’re mainly looking for signatures of compact multi-star systems, unusual pulsating stars in binary systems, and weird objects,” said Saul Rappaport, an emeritus professor of physics at MIT in Cambridge.

Rappaport co-authored the paper and has helped lead the Visual Survey Group for more than a decade. “It’s exciting to identify a system like this because they’re rarely found, but they may be more common than current tallies suggest.”

Many more likely speckle our galaxy, waiting to be discovered.

Partly because the stars in the newfound system orbit in nearly the same plane, scientists say it’s likely very stable despite their tight configuration (the trio’s orbits fit within a smaller area than Mercury’s orbit around the Sun).

Each star’s gravity doesn’t perturb the others too much, like they could if their orbits were tilted in different directions.

But while their orbits will likely remain stable for millions of years, “no one lives here,” Rappaport said.

“We think the stars formed together from the same growth process, which would have disrupted planets from forming very closely around any of the stars.”

The exception could be a distant planet orbiting the three stars as if they were one.

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As the inner stars age, they will expand and ultimately merge, triggering a supernova explosion in around 20 to 40 million years.

In the meantime, astronomers are hunting for triple stars with even shorter orbits. That’s hard to do with current technology, but a new tool is on the way.

Images from NASA’s upcoming Nancy Grace Roman Space Telescope will be much more detailed than TESS’s.

The same area of the sky covered by a single TESS pixel will fit more than 36,000 Roman pixels.

And while TESS took a wide, shallow look at the entire sky, Roman will pierce deep into the heart of our galaxy where stars crowd together, providing a core sample rather than skimming the whole surface.

“We don’t know much about a lot of the stars in the center of the galaxy except for the brightest ones,” said Brian Powell, a co-author and data scientist at Goddard.

“Roman’s high-resolution view will help us measure light from stars that usually blur together, providing the best look yet at the nature of star systems in our galaxy.”

And since Roman will monitor light from hundreds of millions of stars as part of one of its main surveys, it will help astronomers find more triple star systems in which all the stars eclipse each other.

“We’re curious why we haven’t found star systems like these with even shorter outer orbital periods,” said Powell. “Roman should help us find them and bring us closer to figuring out what their limits might be.”

Roman could also find eclipsing stars bound together in even larger groups — half a dozen, or perhaps even more all orbiting each other like bees buzzing around a hive.

“Before scientists discovered triply eclipsing triple star systems, we didn’t expect them to be out there,” said co-author Tamás Borkovits, a senior research fellow at the Baja Observatory of The University of Szeged in Hungary.

“But once we found them, we thought, well why not? Roman, too, may reveal never-before-seen categories of systems and objects that will surprise astronomers.”

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