NASA Astronomy Picture of the Day

October 8, 2024

Annular Eclipse over Patagonia

Can you find the Sun? OK, but can you explain why there’s a big dark spot in the center? The spot is the Moon, and the impressive alignment shown, where the Moon lines up inside the Sun, is called an annular solar eclipse. Such an eclipse occurred just last week and was visible from a thin swath mostly in Earth's southern hemisphere. The featured image was captured from Patagonia, Chile. When the Moon is significantly closer to the Earth and it aligns with the Sun, a total solar eclipse is then visible from parts of the Earth. Annular eclipses are slightly more common than total eclipses, but as the Moon moves slowly away from the Earth, before a billion more years, the Moon's orbit will no longer bring it close enough for a total solar eclipse to be seen from anywhere on Earth.

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

Perseverance Matters

Oct 07, 2024

In January 2024, the SHERLOC instrument aboard NASA’s Mars 2020 Perseverance rover encountered a significant issue.

A fault in the instrument's motor caused the dust cover and autofocus mechanism to become inoperative, putting the rover’s SHERLOC Raman spectroscopy capability at risk.

Although Mars had posed an unexpected challenge, members of the SHERLOC operations team working together with the rover engineers refused to give up.

Fortunately, a motion of the arm on Sol 1077, almost exactly two months after the original issue occurred, resulted in the dust cover moving to a nearly fully open position.

As a result, the team began to look for ways to focus the optics and operate SHERLOC with the dust cover in this open position.

These efforts involved many trials and errors, several rounds of diagnostic examinations, analyses, and troubleshooting around the clock.

And as they say, “It does not matter how slowly you go so long as you do not stop”.

After much hard work and persistence, the team successfully brought the SHERLOC instrument back online in June 2024 with a successful observation of the rock target Walhalla Glades.

It was just the start of an exciting summer for SHERLOC.

In July 2024, SHERLOC’s Raman capability, whose destiny was uncertain a month ago, performed multiple calibrations, scans, and observations on a rock named “Cheyava Falls” and the team was thrilled to discover the mission’s most compelling evidence for organics in the Jezero crater.

Organic compounds can be formed through biological or non-biological processes and the organics that SHERLOC observed in Cheyava Falls would need to be studied in laboratories here on Earth for their origin to be determined.

Regardless of how they formed, the Cheyava Falls organics could tell us a great deal about the Red Planet’s past and present carbon inventory, a possible early carbon cycle, and the precursor conditions to life as we know it.

It is an important and exciting juncture in Mars exploration and astrobiology.

This year, the SHERLOC instrument beat the odds and made one of the most exciting discoveries of the Mars 2020 mission.

As the mission encounters and overcomes problems like that experienced by SHERLOC, we find that exploring Mars can also lead to discovering the team’s persistence and Perseverance.

https://science.nasa.gov/blog/perseverance-matters/

https://www.space.com/nasa-astronaut-tracy-caldwell-dyson-post-flight-briefing

https://www.youtube.com/watch?v=lA0vYqG0bnk

Scrubbed spacewalks, Starliner stay-overs and more: NASA astronaut Tracy C. Dyson discusses her eventful 6 months in orbit

October 7, 2024

Out of the 184 days that NASA astronaut Tracy Caldwell Dyson logged on her most recent mission on board the International Space Station, there are 31 minutes that stand out to her as being among her finest.

Dyson reflected on her time in space during a post-flight press conference at NASA's Johnson Space Center in Houston on Friday (Oct. 4).

She returned to Earth less than two weeks ago on a Russian Soyuz spacecraft that touched down in Kazakhstan.

"It is in some ways emotionally hard to talk about my spacewalks, because the two attempts that we made didn't result in clearing the objectives that we had going in," she said, replying to a question from Space.com.

"But personal feelings aside, those two attempts were a great moment for us as a team, both on orbit and with the interactions that we had with our team on the ground."

A member of the NASA astronaut corps since 1998, Dyson's previous long-duration stay on the space station was 14 years ago.

In interviews she gave prior to her launch in March, she said she was looking forward to going out on a few EVAs (extravehicular activities, or spacewalks), and three outings were indeed planned.

But, as she also said at the time, "things just have a way of changing when you get up there."

"On our first attempt … my partner, Matt Dominick, had some suit issues that were too important to take care of before going out into the vacuum," Dyson said on Friday, referring to a "spacesuit discomfort issue" that occurred on June 13.

NASA replaced Dominick with Michael Barratt for the next try, citing that Barratt already had a suit sized to him.

Dyson and Barratt were to go out and achieve the same tasks — bringing in an antenna and doing some microorganism swabbing ("a Covid test for the International Space Station," quipped Dyson), but they never got beyond opening the hatch.

"On the second attempt, it was … the station's umbilical that provides cooling and data and oxygen that had a leak. It wasn't discovered until removing the umbilical once we were at vacuum in the crew-lock," Dyson told Space.com.

"All of the events that happened in that period of time were very character-building for me, but also I felt during those moments were some of the finest in terms of communication, and that is what I think human interactions are all about — is communication."

"Nothing was more important to me during that period of time than being able to communicate — not just with the ground, but with my crewmate Mike Barratt who was in the crew-lock with me, as well as the rest of our crew," she said.

Communications were key, Dyson explained, because she was the only person who could see what was happening.

Barratt's and her helmet cameras were not yet turned on, and the exterior-mounted video cameras did not have a good angle into the crew-lock.

"Basically, it was a firehose of water and slush coming out my umbilical and it covered my visor with ice, so I could not see what was going on. It took a few microseconds to figure out what needed to be done," said Dyson.

"Suffice it to say, it was great teamwork that brought us in in 31 minutes, and I am going to hang on to those 31 minutes as some of the most character-building moments of my life in space."

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Beyond that half hour, Dyson recounted some of the highlights of her time on serving on station's Expedition 70 and Expedition 71 crews.

Saying that the work, alone, was worth the time she spent off the planet, Dyson spoke about using the station's bio fabrication facility to 3D-print cardiac and meniscus tissue samples; overseeing the departure of a Northrop Grumman supply ship named for a late class member of hers; and adjusting to the extended amount of time that Boeing's Starliner crew spent aboard the station rather than return to Earth after as little as a week to close out the troubled test flight.

"For me — and I know for Suni [Williams], too, because we'e close friends — it was somewhat bittersweet. I wanted her to stay, and she wanted to stay," said Dyson.

"I think that the way we handled it is the way we handle any unexpected event, which we as astronauts, as a space program, are always prepared to handle, and that is, we went with the flow."

Dyson also waxed a bit about witnessing the 2024 North American total solar eclipse from orbit and shared what became one of her favorite meals.

"I used to make a tortilla with beef brisket and braised red cabbage, if you can believe that," she said with a laugh.

According to a schedule released by Roscosmos, Russia's federal space corporation, Dyson may be one of the last Americans to fly on the Soyuz.

After a planned flight by NASA astronaut Jonny Kim next year, the Soyuz human flights announced through 2026 have all-Russian crews.

"In my personal opinion, I think [the crew exchanges] strengthen our partnership with them, and it translates to the work that we do on orbit as a crewmate as well," Dyson said.

"All that we go through in training, not just sitting in a simulator, but through all the water and land survival and all the hard things that we do, from the day to day to seeing each other … really translates well into the relationships and working environment that we have on board station," she added.

"So, from that perspective alone, I would hope that we would be able to continue flying doing this trade of Soyuz and U.S. commercial crewmembers."

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https://www.space.com/james-webb-space-telescope-dusty-pancakes-baby-stars

https://www.mpia.de/news/science/2024-13-jwst-disk-wind

James Webb Space Telescope studies dusty 'pancakes' feeding baby stars and birthing planets

October 7, 2024

Using the James Webb Space Telescope (JWST), astronomers have gained a more detailed picture of the turbulent "pancakes" of gas and dust surrounding young stars, feeding them and facilitating their growth before birthing planets.

JWST gathered new details about the "winds of change" flows of gas that blow through these protoplanetary disks, carving out their shapes.

In the process of doing this, the powerful space telescope saw evidence for a long-hypothesized mechanism that allows a young star to gather the material from the disk that it needs to grow.

A team led by astronomers from the University of Arizona gathered observations of four protoplanetary disk systems, all of which appear edge-on when viewed from Earth.

Constituting the most comprehensive look at the forces that shape protoplanetary disks, they offer a snapshot of what our solar system and infant sun looked like around 4.6 billion years ago, before the formation of Earth and the other planets.

"Our observations strongly suggest that we have obtained the first detailed images of the winds that can remove angular momentum and solve the longstanding problem of how stars and planetary systems form," team leader Ilaria Pascucci, of the University of Arizona's Lunar and Planetary Laboratory, said in a statement.

"How a star accretes mass has a big influence on how the surrounding disk evolves over time, including the way planets form later on," Pascucci said.

"The specific ways in which this happens have not been understood, but we think that winds driven by magnetic fields across most of the disk surface could play a very important role."

It is estimated that within the portion of the cosmos that humanity is capable of seeing, a staggering 3,000 stars are born every second.

In their infancy, those stellar bodies are referred to as "protostars," and they are surrounded by a prenatal cocoon of gas and dust, from which they formed.

Over time, this cloud flattens as it swirls around the protostar, which feeds from it to gather enough mass to kick-start the fusion of hydrogen to helium at its core. This process defines what is a main sequence or "grown-up" star.

However, in order for the protostar to feed and grow, the gas swirling around it must lose angular momentum. If it didn't, it would simply continue to spin around the protostar in perpetuity, suspended and never falling to its surface.

Yet, despite how ubiquitous this process must be in the cosmos, scientists have struggled to understand the mechanism behind the loss of inertia.

One suggestion that has gained support recently is that winds driven by magnetism raging through the protoplanetary disk could funnel gas from its surface, carrying away angular momentum.

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Team member Tracy Beck, a researcher at NASA’s Space Telescope Science Institute, pointed out that because other mechanisms are at work generating winds in protoplanetary disks, it was key for the team to distinguish between these processes.

For instance, a protostar’s magnetic field creates an "X-wind" that pushes out material at the inner edge of the protoplanetary disk.

In the meantime, intense radiation from the baby star blasts material in the outer parts of the disk, causing it to erode and create "thermal winds."

These latter winds blow at slower speeds than X-winds, which can travel dozens of miles per second.

In addition to being faster, X-winds arise farther from the central protostar than thermal winds.

They are also capable of stretching out farther above the disk than thermal winds, reaching distances equal to hundreds of times the distance between Earth and the sun.

Fortunately, the incredible sensitivity and high resolution of JWST's infrared vision are ideally suited to distinguish between magnetic field-driven winds, thermal winds and X-winds blowing around protostars.

The $10 billion space telescope was aided in the investigation by the team's selection of protostar systems that are edge-on when seen from Earth.

That orientation means that the dust and gas in the protoplanetary disk acted as a natural shield, blocking starlight from the protostars, preventing JWST from being dazzled, and allowing it to distinguish between the winds.

Without this hindrance, the team was able to use JWST’s Near Infrared Spectrograph (NIRSpec) to trace distinct atoms and molecules as they traveled across these protoplanetary disks.

Using NIRSpec's Integral Field Unit (IFU) then allowed them to build an intricate 3D picture of the structure of a central jet within a cone-shaped envelope of disk winds.

This envelope was structured like an onion, made of layers originating at progressively greater radii in the disk.

The team discovered pronounced central holes in these cones formed by winds in each of the four protoplanetary disks.

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