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NASA Astronomy Picture of the Day
August 8, 2025
Dawn of the Crab
One of the all-time historic skyscapes occured in July 1054, when the Crab Supernova blazed into the dawn sky. Chinese court astrologers first saw the Guest Star on the morning of 4 July 1054 next to the star Tianguan (now cataloged as Zeta Tauri). The supernova peaked in late July 1054 a bit brighter than Venus, and was visible in the daytime for 23 days. The Guest Star was so bright that every culture around the world inevitably discovered the supernova independently, although only nine reports survive, including those from China, Japan, and Constantinople. This iPhone picture is from Signal Hill near Tucson on the morning of 26 July 2025, faithfully re-creates the year 1054 Dawn of the Crab, showing the sky as seen by Hohokam peoples. The planet Venus, as a stand-in for the supernova, is close to the position of what is now the Crab Nebula supernova remnant. Step outside on a summer dawn with bright Venus, and ask yourself "What would you have thought in ancient times when suddenly seeing the Dawn of the Crab?"
https://apod.nasa.gov/apod/astropix.html
As NASA Missions Study Interstellar Comet, Hubble Makes Size Estimate
Aug 07, 2025
A team of astronomers has taken the sharpest-ever picture of the unexpected interstellar comet 3I/ATLAS using the crisp vision of NASA’s Hubble Space Telescope.
Hubble is one of many missions across NASA’s fleet of space telescopes slated to observe this comet, together providing more information about its size and physical properties.
While the comet poses no threat to Earth, NASA’s space telescopes help support the agency's ongoing mission to find, track, and better understand near-Earth objects.
Hubble’s observations allow astronomers to more accurately estimate the size of the comet’s solid, icy nucleus. The upper limit on the diameter of the nucleus is 3.5 miles (5.6 kilometers), though it could be as small as 1,000 feet (320 meters) across, researchers report.
Though the Hubble images put tighter constraints on the size of the nucleus compared to previous ground-based estimates, the solid heart of the comet presently cannot be directly seen, even by Hubble.
Observations from other NASA missions including the James Webb Space Telescope, TESS (Transiting Exoplanet Survey Satellite), and the Neil Gehrels Swift Observatory, as well as NASA’s partnership with the W.M. Keck Observatory, will help further refine our knowledge about the comet, including its chemical makeup.
Hubble also captured a dust plume ejected from the Sun-warmed side of the comet, and the hint of a dust tail streaming away from the nucleus.
Hubble’s data yields a dust-loss rate consistent with comets that are first detected around 300 million miles from the Sun. This behavior is much like the signature of previously seen Sun-bound comets originating within our solar system.
The big difference is that this interstellar visitor originated in some other solar system elsewhere in our Milky Way galaxy.
3I/ATLAS is traveling through our solar system at a staggering 130,000 miles (209,000 kilometers) per hour, the highest velocity ever recorded for a solar system visitor.
This breathtaking sprint is evidence that the comet has been drifting through interstellar space for many billions of years. The gravitational slingshot effect from innumerable stars and nebulae the comet passed added momentum, ratcheting up its speed.
The longer 3I/ATLAS was out in space, the higher its speed grew.
“No one knows where the comet came from. It’s like glimpsing a rifle bullet for a thousandth of a second.
You can't project that back with any accuracy to figure out where it started on its path,” said David Jewitt of the University of California, Los Angeles, science team leader for the Hubble observations.
New Evidence for Population of Wandering Space Relics
“This latest interstellar tourist is one of a previously undetected population of objects bursting onto the scene that will gradually emerge,” said Jewitt. “This is now possible because we have powerful sky survey capabilities that we didn't have before. We've crossed a threshold."
This comet was discovered by the NASA-funded Asteroid Terrestrial-impact Last Alert System (ATLAS) on July 1, 2025, at a distance of 420 million miles from the Sun. ATLAS is an asteroid impact early warning system developed by the University of Hawai’i.
In the meantime, other NASA missions will provide new insight into this third interstellar interloper, helping refine our understanding of these objects for the benefit of all.
3I/ATLAS should remain visible to ground-based telescopes through September, after which it will pass too close to the Sun to observe, and is expected to reappear on the other side of the Sun by early December.
https://science.nasa.gov/missions/hubble/as-nasa-missions-study-interstellar-comet-hubble-makes-size-estimate/
https://science.nasa.gov/asset/hubble/comet-3i-atlas/
https://arxiv.org/abs/2508.02934
https://avi-loeb.medium.com/
https://www.youtube.com/watch?v=pc4A8va8NRU
US-French SWOT Satellite Measures Tsunami After Massive Quake
Aug 07, 2025
Data provided by the water satellite, a joint effort between NASA and the French space agency, is helping to improve tsunami forecast models, benefitting coastal communities.
The SWOT (Surface Water and Ocean Topography) satellite captured the tsunami spawned by an 8.8 magnitude earthquake off the coast of Russia’s Kamchatka Peninsula on July 30, 11:25 a.m. local time.
The satellite, a joint effort between NASA and the French space agency CNES (Centre National d’Études Spatiales), recorded the tsunami about 70 minutes after the earthquake struck.
Disturbances like an earthquake or underwater landslide trigger a tsunami when the event is large enough to displace the entire column of seawater from the ocean floor to the surface.
This results in waves that ripple out from the disturbance much like dropping a pebble into a pond generates a series of waves.
“The power of SWOT’s broad, paintbrush-like strokes over the ocean is in providing crucial real-world validation, unlocking new physics, and marking a leap towards more accurate early warnings and safer futures,” said Nadya Vinogradova Shiffer, NASA Earth lead and SWOT program scientist at NASA Headquarters in Washington.
Data from SWOT provided a multidimensional look at the leading edge of the tsunami wave triggered by the Kamchatka earthquake.
The measurements included a wave height exceeding 1.5 feet (45 centimeters), shown in red in the highlighted track, as well as a look at the shape and direction of travel of the leading edge of the tsunami.
The SWOT data, shown in the highlighted swath running from the southwest to the northeast in the visual, is plotted against a forecast model of the tsunami produced by the U.S. National Oceanic and Atmospheric Administration (NOAA) Center for Tsunami Research.
Comparing the observations from SWOT to the model helps forecasters validate their model, ensuring its accuracy.
“A 1.5-foot-tall wave might not seem like much, but tsunamis are waves that extend from the seafloor to the ocean’s surface,” said Ben Hamlington, an oceanographer at NASA’s Jet Propulsion Laboratory in Southern California.
“What might only be a foot or two in the open ocean can become a 30-foot wave in shallower water at the coast.”
The tsunami measurements SWOT collected are helping scientists at NOAA’s Center for Tsunami Research improve their tsunami forecast model.
Based on outputs from that model, NOAA sends out alerts to coastal communities potentially in the path of a tsunami.
The model uses a set of earthquake-tsunami scenarios based on past observations as well as real-time observations from sensors in the ocean.
The SWOT data on the height, shape, and direction of the tsunami wave is key to improving these types of forecast models.
“The satellite observations help researchers to better reverse engineer the cause of a tsunami, and in this case, they also showed us that NOAA’s tsunami forecast was right on the money,” said Josh Willis, a JPL oceanographer.
The NOAA Center for Tsunami Research tested their model with SWOT’s tsunami data, and the results were exciting, said Vasily Titov, the center’s chief scientist in Seattle.
“It suggests SWOT data could significantly enhance operational tsunami forecasts — a capability sought since the 2004 Sumatra event.”
The tsunami generated by that devastating quake killed thousands of people and caused widespread damage in Indonesia.
https://www.nasa.gov/missions/swot/us-french-swot-satellite-measures-tsunami-after-massive-quake/
https://swot.jpl.nasa.gov/
Linking Local Lithologies to a Larger Landscape
Aug 07, 2025
NASA’s Mars 2020 rover is continuing to explore a boundary visible from orbit dividing bright, fractured outcrop from darker, smoother regolith (also known as a contact).
The team has called this region “Westport,” (a fitting title, as the rover is exploring the western-most rim of Jezero), which hosts a contact between the smoother, clay-bearing “Krokodillen” unit and an outcrop of olivine-bearing boulders that converge to form a ridge on the outer Jezero crater rim.
To learn more about the nature of this contact, see this blog post by Dr. Melissa Rice. Piecing together geologic events like the formation of this olivine-bearing material on Jezero’s crater rim may allow us to better understand Mars’ most ancient history.
The rover has encountered several olivine-bearing rocks while traversing the rim, but it is unclear if, and how these rocks are all connected.
Jezero crater is in a region of Mars known as Northeast Syrtis, which hosts the largest contiguous exposure (more than 113,000 square kilometers, or more than 43,600 square miles) of olivine-rich material identified from orbit on Mars (about the same square mileage as the state of Ohio!).
The olivine-rich materials are typically found draping over older rocks, often infilling depressions, which may provide clues to their origins. Possible origins for the olivine-rich materials in Northeast Syrtis may include (but are not limited to): (1) intrusive igneous rocks (rocks that cool from magma underground), (2) melt formed and deposited during an impact event, or (3) pyroclastic ash fall or flow from a volcanic eruption.
The Perseverance rover’s investigation of the olivine-bearing materials on the rim of Jezero crater may allow us to better constrain the history of the broader volcanic units present in the Northeast Syrtis region.
Olivine-rich material in Northeast Syrtis is consistently sandwiched between older, clay-rich rock and younger, more olivine-poor material (commonly referred to as the “mafic capping” unit), and may act as an important marker for recording early alteration by water, which could help us understand early habitable environments on Mars.
We see potential evidence of all of these units on Jezero crater’s rim based on orbital mapping. If the olivine-bearing rocks the Perseverance rover is encountering on the rim are related to these materials, we may be able to better constrain the age of this widespread geologic unit on Mars.
https://science.nasa.gov/blog/linking-local-lithologies-to-a-larger-landscape/
https://science.nasa.gov/mission/mars-2020-perseverance/science-updates/
Hubble Captures a Tarantula
Aug 08, 2025
This NASA/ESA Hubble Space Telescope image captures incredible details in the dusty clouds of a star-forming factory called the Tarantula Nebula.
Most of the nebulae Hubble images are in our galaxy, but this nebula is in the Large Magellanic Cloud, a dwarf galaxy located about 160,000 light-years away in the constellations Dorado and Mensa.
The Large Magellanic Cloud is the largest of the dozens of small satellite galaxies that orbit the Milky Way.
The Tarantula Nebula is the largest and brightest star-forming region, not just in the Large Magellanic Cloud, but in the entire group of nearby galaxies to which the Milky Way belongs.
The Tarantula Nebula is home to the most massive stars known, some roughly 200 times as massive as our Sun. This image is very close to a rare type of star called a Wolf–Rayet star.
Wolf–Rayet stars are massive stars that have lost their outer shell of hydrogen and are extremely hot and luminous, powering dense and furious stellar winds.
This nebula is a frequent target for Hubble, whose multiwavelength capabilities are critical for capturing sculptural details in the nebula’s dusty clouds.
The data used to create this image come from an observing program called Scylla, named for a multi-headed sea monster from Greek mythology.
The Scylla program was designed to complement another Hubble observing program called ULLYSES (Ultraviolet Legacy Library of Young Stars as Essential Standards).
ULLYSES targets massive young stars in the Small and Large Magellanic Clouds, while Scylla investigates the structures of gas and dust that surround these stars.
https://science.nasa.gov/missions/hubble/hubble-captures-a-tarantula/
Getting A NASA Grant Just Became Overtly Political
August 7, 2025
This White House Executive Order “Improving Oversight of Federal Grantmaking“ dropped today. Highlights:
“Discretionary awards must, where applicable, demonstrably advance the President’s policy priorities.”
“Applicants should commit to complying with administration policies, procedures, and guidance respecting Gold Standard Science”.
“Each agency head shall promptly designate a senior appointee who shall be responsible for creating a process to review new funding opportunity announcements and to review discretionary grants to ensure that they are consistent with agency priorities and the national interest.”
“The term “senior appointee” means an individual appointed by the President, a non-career member of the Senior Executive Service, or an employee encumbering a Senior Level, Scientific and Professional, or Grade 15 position in Schedule C of the excepted service.”
“Until such time as the process specified in subsection (a) of this section is in place, agencies shall not issue any new funding opportunity announcements without prior approval from the senior appointee designated under subsection (a) of this section, except as required by law.”
“Discretionary awards shall not be used to fund, promote, encourage, subsidize, or facilitate: racial preferences or other forms of racial discrimination by the grant recipient, including activities where race or intentional proxies for race will be used as a selection criterion for employment or program participation; denial by the grant recipient of the sex binary in humans or the notion that sex is a chosen or mutable characteristic; illegal immigration; or any other initiatives that compromise public safety or promote anti-American values.”
https://nasawatch.com/trumpspace/getting-a-nasa-grant-just-became-overtly-political/
https://www.whitehouse.gov/presidential-actions/2025/08/improving-oversight-of-federal-grantmaking/
What makes ‘Oumuamua different from any other space rock we’ve seen
Updated: Aug 08, 2025, 17:16 IST
When ‘Oumuamua passed through our solar system in 2017, it didn’t just surprise astronomers, it puzzled them.
Unlike any asteroid or comet we’ve ever observed, it had strange features and behaviours that sparked intense debate.
It Came From Outside the Solar System
Most space rocks we track were born here. ‘Oumuamua’s speed and path proved it came from another star system, the first confirmed interstellar visitor ever seen.
Unusual Shape
Estimates suggest it was either cigar-shaped or flat like a pancake, with an aspect ratio far beyond that of typical asteroids. Nothing in our solar system has quite the same proportions.
No Visible Tail But Still Moving Like a Comet
Comets usually show a tail when they heat up near the Sun. ‘Oumuamua didn’t, yet its acceleration hinted at some kind of gas release or force at work.
Mysterious Acceleration
After passing the Sun, it sped up slightly instead of just slowing down under gravity. This unexplained boost doesn’t match what’s expected from a purely rocky body.
Strange Colour and Surface
It reflected light in a way that suggested a reddish, metallic or organic-rich surface, possibly altered by cosmic rays over millions of years in deep space.
Brief Visit
Unlike objects in our solar system that orbit the Sun, ‘Oumuamua’s hyperbolic path means it will never return. We had only weeks to observe it before it became too faint.
A Name With Meaning
Its name, Hawaiian for “a messenger from afar arriving first,” reflects its status as a possible herald of other interstellar visitors still to come.
Oumuamua remains one of astronomy’s greatest mysteries. Whether it was a strange natural object or something more, it’s unlike anything we’ve seen before.
https://www.wionews.com/photos/what-makes-oumuamua-different-from-any-other-space-rock-we-ve-seen-1754653322448/1754653322455
https://avi-loeb.medium.com/a-tale-of-three-accelerations-for-oumuamua-405f433eb36b
The mysterious 'dark comets' prowling our Solar System
August 8, 2025
These strange objects could explain how water arrived on Earth, but may also be a previously unrecognised threat to our planet. Now, a spacecraft is headed towards one to investigate.
They are some of the strangest rocks in our Solar System. They aren't quite asteroids and not quite comets, but a bizarre mixture of the two. These are "dark comets" – and no-one knows quite what to make of them.
Yet, these mysterious, recently discovered space rocks might be an entirely new class of object in the Solar System that could help to answer questions about how water originated on Earth, according to the scientists trying to study them.
They may also pose a previously unrecognised threat to our planet.
And now we have a chance of finding out more about these strange objects thanks to a Japanese spacecraft racing towards one – by complete coincidence – right at this moment.
When it gets there in 2031, we might find out for certain what exactly these objects are and how they behave.
The first hint of dark comets emerged in 2016, when astronomers found what they thought was an asteroid that behaved like a comet.
While asteroids are rocky, inactive objects commonly found in a wide belt between the planets Mars and Jupiter, comets are rock and ice that have huge tails stretching for millions of miles and tend to originate from the outer solar system.
The object spotted in 2016 was particularly odd. It appeared to move like a comet, but had none of the typical characteristics of one.
When researchers studied its orbit around the Sun, the object appeared to receive an occasional, sudden push from something other than gravity that changed its motion ever so slightly.
While the movements were small, just fractions of a metre per second, it was enough to be noticeable when looking through telescopes on Earth.
This sort of "non-gravitational acceleration" is normal for comets, where ice heats up rapidly as they near the Sun, triggering a release of gas and dust, which acts a little like a thruster.
In the case of the object spotted in 2016, however, there was no visible dust or ice trail and the object appeared relatively inert.
A year later, astronomers spotted another object behaving similarly – a cigar-shaped lump of rock, metal and ice between 115-400m (377-1,312ft) long that has been named 'Oumuamua. I
t was later found to be one of the first known interstellar objects – an interloper from another star system – to visit our Solar System. The rock sling-shotted around our Sun before heading back out into interstellar space.
Then in 2023, a team of astronomers led by astronomer Darryl Seligman at Michigan State University in the US announced they had found six similar objects orbiting our Sun in asteroid-like orbits that lacked comet-like tails, but were undergoing unusual bursts of speed.
These dark comets, all between 4m (13ft) and 32m (104ft) wide, underwent bursts of acceleration of up one nanometre per second, a tiny amount – but enough to move off their orbits by hundreds of kilometres every few years.
At almost the same time, Seligman and his colleagues published research that showed a 300m (984ft) wide near-earth asteroid called 2003 RM also behaved like a dark comet.
New type of object
Astronomers believe most asteroids and comets are remnants from the early period of planet formation that occurred within the Solar System 4.6 billion years ago.
Some asteroids are fragments of material that never coalesced into planets, while comets are the result of ice and dust further away from the Sun that clumped together.
Experts typically divide these objects into two groups, with inactive asteroids on one hand and the turbulent comets whose ice sublimates, or turns from a solid into a gas, ejecting material into space to create their dramatic tails, on the other.
The existence of dark comets suggests there might not always be a strong dividing line between these two kinds of object.
"This is part of the emerging picture of asteroids and comets as a continuum," says Michele Bannister, an astronomer at the University of Canterbury in New Zealand.
"A historical viewpoint is a comet is something that has a very prominent tail, and an asteroid is something that's very rocky and dry. That picture has completely gone."
https://www.bbc.com/future/article/20250807-a-japanese-spacecraft-is-racing-toward-a-mysterious-dark-comet-to-discover-the-secrets-it-holds
https://www.pnas.org/doi/10.1073/pnas.2406424121
https://www.space.com/astronomy/black-holes/the-biggest-black-hole-ever-seen-scientists-find-one-with-mass-of-36-billion-suns
https://academic.oup.com/mnras/article/541/4/2853/8213862
https://ras.ac.uk/news-and-press/research-highlights/most-massive-black-hole-ever-discovered-detected
The biggest black hole ever seen? Scientists find one with mass of 36 billion suns
August 8, 2025
About 5 billion light-years away from where you're sitting, in one of the most massive galaxies on record, there exists an astonishing black hole.
It was only just measured by scientists who managed to peer through the fabric of warped space-time — and it appears to hold a mass equivalent to that of 36 billion suns.
Yes, billion. "This is amongst the top 10 most massive black holes ever discovered, and quite possibly the most massive," Thomas Collett, study author and a professor at the University of Portsmouth in England, said in a statement.
More specifically, the black hole is found in one of two galaxies that make up the Cosmic Horseshoe system and is what's known as a "dormant" black hole.
This means it's a relatively quiet black hole; it isn't actively chomping on matter in its surroundings, as opposed to an active black hole that is accreting matter from a disk that circles it, known as an accretion disk.
The black hole at the center of our Milky Way galaxy, Sagittarius A*, is also a dormant black hole — but, for context, it only holds the mass of about 4.15 million suns.
The fact that the Cosmic Horseshoe black hole is found in such a massive galaxy and that Sagittarius A* is found in our more modestly sized Milky Way is probably not a coincidence.
In fact, the team behind the new measurement is hoping to learn more about the apparent size connection between supermassive black holes and their parent galaxies.
"We think the size of both is intimately linked," Collett said, "because when galaxies grow they can funnel matter down onto the central black hole.
Some of this matter grows the black hole, but lots of it shines away in an incredibly bright source called a quasar.
These quasars dump huge amounts of energy into their host galaxies, which stops gas clouds condensing into new stars."
This brings us to another key aspect of the team's findings: the way this black hole was measured to begin with.
The research team was able to utilize a unique approach that doesn't rely on the black hole being an actively accreting one. Without active feeding, black holes can kind of hide behind the veil of the cosmos.
It is the accretion itself that usually gives these objects away. Such commotion produces lots of emissions, like X-rays, that scientists here on Earth can detect.
Naturally, it's also far easier to measure the precise masses of black holes via such emissions.
However, there is one characteristic of black holes that even dormant ones can't suppress: their immense gravitational pull.
And the greater the gravitational pull, the greater the warp in space-time, as predicted by Albert Einstein's general relativity theory.
Where Einstein comes in
In a nutshell, Albert Einstein's famous theory of general relativity explains the true nature of gravity. It suggests that gravity isn't quite an intrinsic, elusive property of an object that pulls things down.
In other words, Earth itself isn't really pulling us down to the ground. Rather, general relativity states that objects with mass (all objects, including you and me) warp the four-dimensional fabric of space-time — and these warps influence the motion of other objects caught up in the folds.
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For instance, imagine a trampoline on which you place a ball. That ball would warp the trampoline inward. Now, imagine placing a smaller ball on the trampoline.
That smaller ball would fall inward as well, along the warped trampoline's fabric and sit right next to the original ball. The trampoline in this case is space-time, the original ball is Earth and the smaller ball is you.
The big caveat in this analogy, however, is that this trampoline exists in three dimensions. We'd need to scale this up to the four-dimensional universe for it to start representing reality more accurately, but our brains have a hard time comprehending that dimension visually.
Importantly for the team's new measurements, something that arises from warped space-time (in the fourth dimension, remember) is that physical matter isn't the only thing affected by the warps.
Light gets affected, too — and that includes light emanating from galaxies, such as the other galaxy in the Cosmic Horseshoe.
This is the effect the study team managed to take advantage of when spotting the newly confirmed black hole.
Light from the Cosmic Horseshoe system's background galaxy was warped as it traveled past the foreground galaxy that contains black hole.
The Cosmic Horseshoe system is actually an iconic example of this effect, which is called gravitational lensing.
Not only does this system have a strong version of this effect, but each galaxy involved happens to be perfectly aligned such that the light-warped background galaxy appears as almost a perfect ring around the foreground galaxy.
When this happens, it's called an "Einstein Ring." So, we're seeing an "almost" Einstein ring in this case. It's more like … an Einstein horseshoe?
After combining those gravitational lensing measurements with measurements of stars in the vicinity that appeared to be zipping around at high speeds, the researchers knew they were onto something.
Though scientists have previously suggested a monster black hole lurks in the Cosmic Horseshoe system, concrete evidence of the object and of its precise size wasn't available until now.
"We detected the effect of the black hole in two ways — it is altering the path that light takes as it travels past the black hole and it is causing the stars in the inner regions of its host galaxy to move extremely quickly (almost 400 km/s)," Collet said.
"By combining these two measurements, we can be completely confident that the black hole is real."
"Its detection relied purely on its immense gravitational pull and the effect it has on its surroundings," Carlos Melo, study lead author and a Ph.D. candidate at the Universidade Federal do Rio Grande do Sul in Brazil, said in the statement.
"What is particularly exciting is that this method allows us to detect and measure the mass of these hidden ultramassive black holes across the universe, even when they are completely silent."
What's next?
There are quite a few ways to move forward on this work, one of which is, as mentioned, to reveal the link between galaxy size and supermassive black hole size — but another could be to zero in on the Cosmic Horseshoe black hole alone and learn how it became so utterly gigantic.
The Cosmic Horseshoe is what's known as a "fossil group," which refers to the end stage of the "most massive gravitationally bound structures in the universe, arising when they have collapsed down to a single extremely massive galaxy, with no bright companions," according to the statement.
The Milky Way and Andromeda galaxies will likely become a fossil group someday, seeing as they're likely on a path to colliding somewhere in the far future.
That crash has recently been brought into question, but it's still a possibility. Nonetheless, the Cosmic Horseshoe could very well be a peek into our realm's final era.
"It is likely that all of the supermassive black holes that were originally in the companion galaxies have also now merged to form the ultramassive black hole that we have detected," said Collett.
"So we're seeing the end state of galaxy formation and the end state of black hole formation."
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