When the DART (Double Asteroid Redirection Test) spacecraft intentionally slammed into asteroid moonlet Dimorphos on September 26, 2022, telescopes around the world and those in space watched as it happened, and continued to monitor the aftermath.
Of course, the Hubble Space Telescope was focused on the event. In looking at Hubble’s images and data from post-impact, astronomers discovered 37 boulders that were ejected due to the impact. These boulders range in size from 1 meter (3 feet) to 6.7 meters (22 feet).
However, these boulders were not debris created by the spacecraft’s impact. Instead, they were boulders that were already on the surface of Dimorphos, and the impact event “shook” the boulders loose. A team of astronomers, led by David Jewitt and Yoonyoung Kim say in their paper detailing the findings that these boulders are some of the faintest objects ever imaged in the Solar System, only visible because of Hubble’s keen sensitivity. The images here showing the boulders surrounding Dimorphos were taken on December 19, 2022.
The last complete image of asteroid moonlet Dimorphos, taken by the DRACO imager on NASA’s DART mission from ~7 miles (12 kilometers) from the asteroid and 2 seconds before impact. The image shows a patch of the asteroid that is 100 feet (31 meters) across. Dimorphos’ north is toward the top of the image. Credits: NASA/Johns Hopkins APL
Two seconds before impact, DART’s DRACO imager took and sent back an image of Dimorphos, showing a surface covered with boulders of various shapes and sizes – basically a rubble pile. The astronomers are not certain yet how the boulders were “lifted” off the asteroid’s surface. They could be part of the large ejecta plume that was observed by Hubble and several other observatories. Or another explanation is that a seismic wave from the impact could have shaken the asteroid — similar to hitting a bell with a hammer — which may have shook loose the surface rubble.
The bright white object at lower left is the asteroid Dimorphos. It has a blue dust tail extending diagonally to the upper right. A cluster of blue dots surrounds the asteroid. These are boulders that were knocked off the asteroid when, on 26 September 2022, NASA deliberately slammed the half-tonne DART impactor spacecraft into the asteroid as a test of what it would take to deflect some future asteroid from hitting Earth. Hubble photographed the slow-moving boulders in December 2022. Credit:NASA, ESA, D. Jewitt (UCLA)
“The numbers, sizes, and shapes of the boulders imaged using HST are consistent with an origin as preexisting objects dislodged from about 2% of the surface of Didymos by the DART impact, corresponding to a circular patch 50 meters in diameter or larger,” the team wrote in their paper.
DART weighed 610 kg (1,340 lb) and it crashed into Dimorphos at approximately 22,530 km/h (14,000 mph). The impact lowered Dimorphos’ orbital speed and reduced its orbital radius. DART excavated a crater on the Dimorphos’ surface that ejected more than 900,000 kg (990 US tons) of debris into space. DART’s impact into Dimorphos also changed the trajectory of the moonlet’s parent asteroid, Didymos.
With this new data from Hubble, along with other observatories data from the impact, astronomers are fairly certain that Dimorphos is a rubble pile asteroid. These are asteroids that consist of reassembled fragments
Review: Patagonia R1 Air Full-Zip Hoody
Hooded Fleece Jacket
Patagonia R1 Air Full-Zip Hoody
$179, 12.5 oz./354g (men’s medium)
Sizes: men’s XS-XXL, women’s XXS-XL, kids XS-XXL
As I’ve repeatedly written at this blog, virtually no piece of outdoor apparel offers more versatility than a highly breathable, midweight insulation layer; arguably, the only “layer” you will wear more is your skin. Find a highly breathable midweight jacket that’s soft and fits like it was custom made for your torso and you have a winner. Patagonia’s R1 Air Full-Zip Hoody could play that role for almost any outdoor user, from hard-core backpackers, climbers, and backcountry skiers to the average dayhiker and fitness walker, as I found wearing it on backpacking trips in Glacier National Park and the Canadian Rockies, not to mention countless days around town and at home.
At 12.5 ounces/354 grams (men’s medium), this midweight fleece is designed for wearing as an outer or middle layer in a huge range of cool to cold temperatures, including activities and seasons as diverse as hiking or climbing in virtually any mountains in any month of the year, southern climes from fall through spring, or for any winter activity—skiing, hiking, running, walking, you pick.
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The Patagonia R1 Air Full-Zip Hoody.
” data-image-caption=”The Patagonia R1 Air Full-Zip Hoody.
” data-medium-file=”https://i0.wp.com/thebigoutside.com/wp-content/uploads/2023/09/Patagonia-R1-Air-Full-Zip-Hoody.jpg?fit=300%2C200&ssl=1″ data-large-file=”https://i0.wp.com/thebigoutside.com/wp-content/uploads/2023/09/Patagonia-R1-Air-Full-Zip-Hoody.jpg?fit=900%2C600&ssl=1″ src=”https://i0.wp.com/thebigoutside.com/wp-content/uploads/2023/09/Patagonia-R1-Air-Full-Zip-Hoody.jpg?resize=900%2C600&ssl=1″ alt=”The Patagonia R1 Air Full-Zip Hoody.” class=”wp-image-60252″ srcset=”https://i0.wp.com/thebigoutside.com/wp-content/uploads/2023/09/Patagonia-R1-Air-Full-Zip-Hoody.jpg?resize=1024%2C683&ssl=1 1024w, https://i0.wp.com/thebigoutside.com/wp-content/uploads/2023/09/Patagonia-R1-Air-Full-Zip-Hoody.jpg?resize=300%2C200&ssl=1 300w, https://i0.wp.com/thebigoutside.com/wp-content/uploads/2023/09/Patagonia-R1-Air-Full-Zip-Hoody.jpg?resize=768%2C512&ssl=1 768w, https://i0.wp.com/thebigoutside.com/wp-content/uploads/2023/09/Patagonia-R1-Air-Full-Zip-Hoody.jpg?resize=150%2C100&ssl=1 150w, https://i0.wp.com/thebigoutside.com/wp-content/uploads/2023/09/Patagonia-R1-Air-Full-Zip-Hoody.jpg?w=1200&ssl=1 1200w” sizes=”(max-width: 900px) 100vw, 900px” data-recalc-dims=”1″ />The Patagonia R1 Air Full-Zip Hoody.
It kept me warm without overheating—rarely even breaking a sweat—wearing it over one base layer while hiking with a full pack, uphill and downhill, on cool, generally calm mornings and some windy afternoons during a weeklong, nearly 70-mile September backpacking trip in Glacier National Park, and hiking in chilly, very strong wind on three-day hikes on both the Skyline Trail in Jasper National Park and the Nigel, Cataract, and Cline Passes Route in the White Goat Wilderness of the Canadian Rockies in the first week of August.
On those backpacking trips, I also wore it in camp both as an outer layer and, when temps dropped, under a down jacket—meaning the R1 Air Hoody doubled as an on-trail layer and a camp layer that allowed me to bring a lighter puffy and forego a midweight, long-sleeve shirt. To frame it another way: The R1 Air Hoody cut my layering system weight by replacing or reducing two other layers. Few pieces of apparel offer more versatility while reducing your pack weight.
I also wore it on breezy, cool evenings in the 50s between waves of thunderstorms
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Gaia is Now Finding Planets. Could it Find Another Earth?
The ESA launched Gaia in 2013 with one overarching goal: to map more than one billion stars in the Milky Way. Its vast collection of data is frequently used in published research. Gaia is an ambitious mission, though it seldom makes headlines on its own.
But that could change.
Gaia relies on astrometry for much of its work, and astrometry is the measurement of the position, distance, and motions of stars. It’s so sensitive that it can sometimes detect the slight wobble a planet imparts to its much more massive star. Gaia detected its first two transiting exoplanets in 2021, and it’s expected to find thousands of Jupiter-size exoplanets beyond our Solar System.
But new research takes it even further. It shows that Gaia should be able to detect Earth-like planets up to 30 light-years away.
The new paper is “The Possibility of Detecting our Solar System Through Astrometry,” and is available on the pre-press site arxiv.org. It has a single author: Dong-Hong Wu from the Department of Physics, Anhui Normal University, Wuhu, Anhui, China.
Astronomers find most exoplanets with the transit method. A spacecraft like TESS monitors a section of the sky and looks at many stars at once. When a planet passes between us and one of the stars, it’s called a transit. It creates a dip in starlight that TESS’s sensitive instruments can detect. When TESS detects multiple, predictable dips, it signifies a planet.
But that’s not the only way to detect them. Astrometry can do it too, and that’s Gaia’s way.
Astrometry has an advantage over other methods. Gaia can more accurately determine an exoplanet’s orbital parameters. This doesn’t mean the other methods aren’t valuable. They obviously are. But as the paper’s author explains, “Neither the transit nor radial velocity method provides complete physical parameters of one planet, and both methods prefer to detect planets close to the central star. On the contrary, the astrometry method can provide a three-dimensional characterization of the orbit of one planet and has the advantage of detecting planets far away from the host star.” Astrometry’s advantages are clear.
If other technological planetary civs exist—and that’s a big if—then it’s not outrageous to think they have technology similar to Gaia’s. While Gaia is impressive, there are improvements on the horizon that will make astrometry even more precise. The author asks a question in his paper: If ETIs (ExtraTerrestrial Intelligences) are using advanced astrometry equal to or even surpassing Gaia’s, “…which of them could discover the planets in the solar system, even the Earth?”
Astrometrical precision is calculated in microarcseconds, and precision decreases with distance. The ESA says that Gaia can measure a star’s position within 24 microarcseconds for objects 4000 times fainter than the naked eye. That’s like measuring the thickness of a human hair from 1000 km away. But that’s not precise enough for Wu’s scenario. His work is based on even more advanced astrometry, the type we’ll likely have in the near future. “If the astrometry precision is equal to or better than ten microarcseconds, all 8,707 stars located within 30 pcs of our solar system possess the potential to detect the four giant planets within 100 years.”
This is the heart of Wu’s paper. The 30-parsec (approx. 100 light-years) region contains almost 9,000 stars, and if an ETI from one of those stars has powerful enough astrometry, then it could detect Jupiter, Saturn, Uranus, and Neptune. The only drawback is they’d have to observe our Solar System for nearly a century to make sure the signal was clear.
1,” the author writes. Image Credit: Wu 2023.” class=”wp-image-163369″ srcset=”https://www.universetoday.com/wp-content/uploads/2023/09/Giant-Planet-Detection.png 492w, https://www.universetoday.com/wp-content/uploads/2023/09/Giant-Planet-Detection-374×580.png 374w, https://www.universetoday.com/wp-content/uploads/2023/09/Giant-Planet-Detection-161×250.png 161w” sizes=”(max-width: 492px) 100vw, 492px” />
This figure from the research shows how long it would take for an ETI with advanced astrometry to detect our Solar System’s four giant planets. “We find that all the four giants in our solar system could be detected and well-characterized as long as they are observed for at least 90 years with SNR > 1,” the author writes. Image Credit: Wu 2023.
There are 8707 stars within 100
Finally! Astronomers are Starting to See the First Galaxies Coming Together With JWST
One of the James Webb Space Telescope’s principal science goals is to observe the epoch where we think that the first galaxies were created, to understand the details of their formation, evolution, and composition. With each deep look back in time, the telescope seems to break its own record for the most distant galaxy ever seen. Science papers are now are starting to trickle in, as astronomers are finally starting to collect enough data from JWST to build a deeper understanding of the early Universe.
In a new study published in Nature Astronomy, a team of researchers in Denmark believe they have observed some of the very first, earliest galaxies with JWST. These galaxies are so old, they are likely still in the process of being formed.
One known standard is that the ratio between galaxies and their heavy elements has held constant in the local Universe through the last 12 billion years of history, or about 5/6 of the age of the Universe. But with JWST, astronomers are now seeing that the youngest galaxies look different. They don’t have that same ratio of stars to heavier elements because they haven’t gone through the cycles of star formation and star death yet, enriching gas clouds with metals, i.e., elements heavier than hydrogen and helium.
This plot shows the observed galaxies in an “element-stellar mass diagram”: The farther to the right a galaxy is, the more massive it is, and the farther up, the more heavy elements it contains. The gray icons represent galaxies in the present-day Universe, while the red show the new observations of early galaxies. These ones clearly have much less heavy elements than later galaxies, but agree roughly with theoretical predictions, indicated by the blue band. Credit: Kasper Elm Heintz, Peter Laursen.
For this study, the astronomers looked at 16 galaxies, some of the earliest galaxies ever observed. Their observations revealed that the chemical abundances in these galaxies are one-fourth of that seen in galaxies that were formed later. In their paper, the astronomers wrote that “these findings suggest that galaxies at this time are still intimately connected with the intergalactic medium and subject to continuous infall of pristine gas, which effectively dilutes their metal abundances.”
As gravity gathered together the first clumps of gas,the first stars and galaxies were formed.
“When we analyzed the light from 16 of these first galaxies, we saw that they had significantly less heavy elements, compared to what you’d expect from their stellar masses and the amount of new stars they produced,” said Kasper Elm Heintz, leader of the study and assistant professor at the Cosmic Dawn Center at the Niels Bohr Institute and DTU Space in Copenhagen, Denmark, in a press release.
These results, the astronomers say, are in stark contrast to the current model where galaxies evolve in a form of equilibrium throughout most of the history of the Universe, where there is a relationship between how many stars have formed and how many heavy elements have formed.
Illustration of galaxy formation: Diffuse gas from intergalactic space plummets toward the center, sparking star formation and becoming part of the galaxy’s rotating disk. When stars die, they return their gas to the galaxy (and the intergalactic space), now enriched with heavy elements. Credit: Tumlinson et al. (2017)
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