NASA Astronomy Picture of the Day
September 29, 2025
Two Camera Comets in One Sky
It may look like these comets are racing, but they are not. Comets C/2025 K1 ATLAS (left) and C/2025 R2 SWAN (right) appeared near each other by chance last week in the featured image taken from France's Reunion Island in the southern Indian Ocean. Fainter Comet ATLAS is approaching our Sun and will reach its closest approach in early October when it is also expected to be its brightest – although still only likely visible with long exposures on a camera. The brighter comet, nicknamed SWAN25B, is now headed away from our Sun, although its closest approach to Earth is expected in mid-October, when optimistic estimates have it becoming bright enough to see with the unaided eye. Each comet has a greenish coma of expelled gas and an ion tail pointing away from the Sun.
https://apod.nasa.gov/apod/astropix.html
Was the “Wow! Signal” Emitted from 3I/ATLAS?
September 28, 2025
The “Wow! Signal” was detected on August 15, 1977 as a strong narrowband radio signal by Ohio State University’s Big Ear radio telescope. Its origin was inferred to be extraterrestrial.
The latest natural explanation (accessible here) hypothesized that the “Wow! Signal” was caused by a sudden brightening of the hydrogen line emitted from an interstellar cloud, triggered by a strong transient radio source, such as a flare from a highly magnetized neutron star (magnetar).
The “Wow! Signal” originated from the sky coordinates of Right Ascension (RA)=19h25m=291 degrees and Declination (Dec)=-27 degrees.
On August 12, 1977, the interstellar object 3I/ATLAS was at a distance of about 600 times the Earth-Sun separation (AU) — corresponding to a light-travel time of about 3 days.
It had the sky coordinates of RA=19h40m=295 degrees and Dec=-19 degrees. These parameters can be inferred accurately given the lack of non-gravitational acceleration for 3I/ATLAS, as inferred in my latest paper (accessible here).
Hence, the “Wow! Signal” was separated by approximately 4 degrees in RA and 8 degrees in Dec from the direction of 3I/ATLAS.
The chance of two random directions in the sky being aligned to that level is about 0.6 percent. If the “Wow! Signal” originated from 3I/ATLAS, how powerful was the transmitter?
The detected intensity of the “Wow! Signal” was in the range of 54–212 Jansky with a bandwidth of about 10 kilohertz. At the distance of 600 AU, this corresponds to a source power of 0.5–2 gigawatts, the output of a typical nuclear reactor on Earth.
The “Wow! Signal” was observed at a frequency of 1420.4556±0.005 megahertz, blue-shifted by about 10 kilometers per second towards Earth relative to the central frequency of the hydrogen line.
This blueshift is of the same order of magnitude but smaller than expected from the approach velocity of 3I/ATLAS towards the Sun, 60 kilometers per second.
So far, no radio telescope reported data on 3I/ATLAS. Here’s hoping that the coincidence in the arrival direction of 3I/ATLAS and the “Wow! Signal” would motivate radio observers to check whether 3I/ATLAS shows any radio transmission around the hyperfine line of hydrogen.
This raises a broader question: in case we detect an artificial signal from an interstellar object, how should we engage with it?
The details would depend on the properties of the object. To measure these properties, we should attempt to use all telescopes on Earth and in space.
Between October 1–7, 2025 NASA’s Mars Reconnaissance Orbiter and ESA’s Mars orbiters Mars Express and ExoMars will observe 3I/ATLAS as it passes within 29 million kilometers from Mars.
Subsequently, between November 2–25, 2025, ESA’s Jupiter Icy Moons Explorer (Juice) will observe 3I/ATLAS with various instruments.
The urgency of a response would depend on the rank of the object on the Loeb Scale (see the quantitative discussions here and here).
Rank 10 would suggest an imminent threat akin to a visitor to our backyard who is capable of approaching the front door, requiring an immediate response.
But even a low rank would necessitate a contingency plan because of the major implications to humanity if the threat is realized.
We must consider the possibility of a black swan event from interstellar objects resembling a comet at large distances, but potentially carrying devastating consequences to our future like a Trojan Horse.
Our engagement could either be messaged electromagnetically through a radio or laser communication signal, or involve interceptors which cross the path of the interstellar object, land on it or take a close-up photograph.
Our interpretation of the data would be biased by our limited knowledge. In analogy with artificial intelligence (AI) systems, human reasoning is as good as its training data set.
Whereas our knowledge is restricted to experiences on Earth, our dating partner might exhibit alien designs which go well beyond our current perception of reality.
In that case, communication might be as difficult as it is for ants looking from the vantage point of a crack in a pavement at a biker passing by.
https://avi-loeb.medium.com/was-the-wow-signal-emitted-from-3i-atlas-d18d4f0d1f1e
ESA’s Mars and Jupiter missions observe comet 3I/ATLAS
26/09/2025
Comet 3I/ATLAS was first spotted on 1 July 2025 by an Asteroid Terrestrial-impact Last Alert System (ATLAS) telescope in Río Hurtado, Chile.
Since then, Earth has been moving away from 3I/ATLAS as it approaches the Sun. The comet is now on the other side of the Sun, making it impossible to observe from Earth.
ESA is making the most of its interplanetary missions to observe the comet from much better vantage points.
Between 1 and 7 October, our Mars orbiters Mars Express and ExoMars Trace Gas Orbiter will observe the comet as it passes close to Mars, with the closest distance between the spacecraft and the comet being 30 million km on 3 October.
Then between 2 and 25 November ESA’s Jupiter Icy Moons Explorer (Juice) will observe the comet with various instruments.
As Juice looks towards 3I/ATLAS so soon after its closest approach to the Sun, it is likely to have the best view of the comet in a very active state, with a bright halo around its nucleus and a long tail stretching out behind it.
Read our comet 3I/ATLAS frequently asked questions for more details on how our Mars and Jupiter missions will observe the comet.
https://www.esa.int/ESA_Multimedia/Images/2025/09/ESA_s_Mars_and_Jupiter_missions_observe_comet_3I_ATLAS
https://www.esa.int/Science_Exploration/Space_Science/Comet_3I_ATLAS_frequently_asked_questions
https://www.esa.int/Science_Exploration/Space_Science/ESA_observations_of_interstellar_comet_3I_ATLAS
Solar Alert - Rapid Sunspot Growth, Several Solar Flares | S0 News
Sep.29.2025
https://www.youtube.com/watch?v=ZNycmsQ3yoI
https://spaceweathernews.com/
Batman Comic Art Coin and Medals Available on September 25
September 18, 2025
The United States Mint (Mint), in collaboration with Warner Bros. Discovery Global Consumer Products (WBDGCP), will begin accepting pre-orders for the second release in the Comic Art Coin and Medal program depicting Batman™ on Thursday, September 25 at noon EDT. Products will be shipped during winter 2025.
Product options, pricing, and order limits are below. To set up “Remind Me” alerts for each individual product, visit the product page.
Pricing for the gold product options is based on the Mint’s Pricing of Numismatic Gold, Commemorative Gold, Platinum, and Palladium Products Pricing Grid.
From the shadows, DC’s Dark Knight™ emerges as the second release in our groundbreaking Comic Art Coin and Medal Program, which celebrates comic book art as a uniquely American art form.
Batman is newly etched in a proof finished 24-karat gold coin, fine silver medals, and later in a clad medal that depict the iconic Super Hero ready to fight crime in Gotham City™.
These stunning products display Batman’s steadfast courage and his never-ending crusade for justice.
The obverse (heads) design depicts Batman leaping into action to protect those in need. A decorative eagle, carved in stone, perches atop a Gotham City building behind him.
The inscriptions are “LIBERTY,” “IN GOD WE TRUST,” and “2025” (24-karat gold coin); “LIBERTY” and “2025” (2.5-ounce silver medal); and “LIBERTY” (one-ounce silver medal). Mint Chief Engraver Joseph Menna designed and sculpted the obverse.
The reverse (tails) design features Batman against the background of Gotham City while the Bat-Signal shines brightly above.
The inscriptions are “UNITED STATES OF AMERICA,” “E PLURIBUS UNUM,” “$50,” “1/2 OZ,” and “.9999 FINE GOLD” (24-karat gold coin); “BATMAN” and “JUSTICE AND COURAGE” (2.5-ounce silver medal); and “BATMAN” and “JUSTICE AND COURAGE” (one-ounce silver medal).
Mint Medallic Artist John P. McGraw designed the reverse, which was sculpted by Mint Chief Engraver Menna.
To complement these stunning designs, each 24-karat gold coin and silver medal is encapsulated and packaged in a presentation case and is accompanied by a Certificate of Authenticity (COA).
The 24-karat gold coin and the 2.5-ounce silver medal will each have a numbered COA.
A Product Subscription Program is available for the one-ounce silver medal. Subscriptions are limited to five medals per household (household limits subject to change).
Sign up once and you will receive the next product released in the series after the date of your registration, then continue to receive products until you end your subscription or until the series ends. For additional details about subscriptions, visit here.
The Mint has extended the subscription cutoff date for the Comic Art One Ounce Silver Medal depicting Superman™ through September 25, 2025, allowing the subscription window for this medal to remain open until the product is ready to ship.
Customers who subscribe to the Comic Art One Ounce Silver Medal before September 25, 2025, will receive the Superman One Ounce Silver Medal when it ships, and still be in line for the Batman One Ounce Silver Medal.
Customers who subscribe after September 25, 2025, will start with the Batman One Ounce Silver Medal.
https://www.usmint.gov/news/press-releases/batman-comic-art-coin-and-medals-available-on-september-25
https://www.usmint.gov/comic-art-coins/
https://www.youtube.com/watch?v=ZbAszxClqC8
NASA’s Webb Telescope Studies Moon-Forming Disk Around Massive Planet
Sep 29, 2025
NASA’s James Webb Space Telescope has provided the first direct measurements of the chemical and physical properties of a potential moon-forming disk encircling a large exoplanet.
The carbon-rich disk surrounding the world called CT Cha b, which is located 625 light-years away from Earth, is a possible construction yard for moons, although no moons are detected in the Webb data.
The results published today in The Astrophysical Journal Letters.
The young star the planet orbits is only 2 million years old and still accreting circumstellar material. However, the circumplanetary disk discovered by Webb is not part of the larger accretion disk around the central star. The two objects are 46 billion miles apart.
Observing planet and moon formation is fundamental to understanding the evolution of planetary systems across our galaxy. Moons likely outnumber planets, and some might be habitats for life as we know it. But we are only now entering an era where we can witness their formation.
This discovery fosters a better understanding of planet and moon formation, say researchers. Webb’s data is invaluable for making comparisons to our solar system's birth over 4 billion years ago.
“We can see evidence of the disk around the companion, and we can study the chemistry for the first time.
We're not just witnessing moon formation — we're also witnessing this planet’s formation,” said co-lead author Sierra Grant of the Carnegie Institution for Science in Washington.
“We are seeing what material is accreting to build the planet and moons,” added main lead author Gabriele Cugno of the University of Zürich and member of the National Center of Competence in Research PlanetS.
Image A: Circumplanetary Disk (Artist's Concept)
Dissecting starlight
Infrared observations of CT Cha b were made with Webb’s MIRI (Mid-Infrared Instrument) using its medium resolution spectrograph.
An initial look into Webb’s archival data revealed signs of molecules within the circumplanetary disk, which motivated a deeper dive into the data.
Because the planet’s faint signal is buried in the glare of the host star, the researchers had to disentangle the light of the star from the planet using high-contrast methods.
“We saw molecules at the location of the planet, and so we knew that there was stuff in there worth digging for and spending a year trying to tease out of the data. It really took a lot of perseverance,” said Grant.
Ultimately, the team discovered seven carbon-bearing molecules within the planet’s disk, including acetylene (C2H2) and benzene (C6H6).
This carbon-rich chemistry is in stark contrast to the chemistry seen in the disk around the host star, where the researchers found water but no carbon.
The difference between the two disks offers evidence for their rapid chemical evolution over only than 2 million years.
Genesis of moons
A circumplanetary disk has long been hypothesized as the birthplace of Jupiter’s four major moons. These Galilean satellites must have condensed out of such a flattened disk billions of years ago, as evident in their co-planar orbits about Jupiter.
The two outermost Galilean moons, Ganymede and Callisto, are 50% water ice. But they presumably have rocky cores, perhaps either of carbon or silicon.
“We want to learn more about how our solar system formed moons. This means that we need to look at other systems that are still under construction. We’re trying to understand how it all works,” said Cugno.
“How do these moons come to be? What are their ingredients? What physical processes are at play, and over what timescales? Webb allows us to witness the drama of moon formation and investigate these questions observationally for the first time.”
In the coming year, the team will use Webb to perform a comprehensive survey of similar objects, to better understand the diversity of physical and chemical properties in the disks around young planets.
https://science.nasa.gov/science-research/nasas-webb-telescope-studies-moon-forming-disk-around-massive-planet/
https://iopscience.iop.org/article/10.3847/2041-8213/ae0290
NASA Shutdown Watch
September 29, 2025
snapshots of where things lie. It is dynamic and will change three times before lunch time today.
“Trump’s shutdown plans: Mass layoffs, deregulation, military deployments“, Washington Post:
“If Congress fails to fund the government next week, the White House is preparing for a shutdown that would reflect the purest version of President Donald Trump’s vision for the federal government, guided by White House budget director Russell Vought, an architect of the controversial Project 2025 playbook for Trump’s second term.”
https://www.washingtonpost.com/business/2025/09/27/trump-government-shutdown-plan/
“Federal workers brace for potential government shutdown, mass layoff“, CNN:
“This employee said that as of Thursday afternoon, they had not received any information from agency leadership acknowledging the possible shutdown.
Another source said there similarly hasn’t been any agency-wide guidance circulated within the National Oceanic and Atmospheric Administration, or NOAA, which saw mass DOGE firings followed by hundreds of re-hirings.
“We are hearing very little from leadership,” the NOAA source said. And regarding potential layoffs, “we are keeping an anxious ear to the ground.”
https://www.cnn.com/2025/09/27/politics/government-shutdown-federal-workers-layoffs-fear
https://nasawatch.com/congress/nasa-shutdown-watch/