NASA Astronomy Picture of the Day

June 30, 2025

NGC 4651: The Umbrella Galaxy

What appears to be a giant cosmic umbrella is now known to be a tidal stream of stars stripped from a small satellite galaxy. The main galaxy, spiral galaxy NGC 4651, is about the size of our Milky Way, while its stellar parasol appears to extend some 100 thousand light-years above this galaxy's bright disk. A small galaxy was likely torn apart by repeated encounters as it swept back and forth on eccentric orbits through NGC 4651. The remaining stars will surely fall back and become part of a combined larger galaxy over the next few million years. The featured deep image was captured in long exposures from Saudi Arabia. The Umbrella Galaxy lies about 50 million light-years distant toward the well-groomed northern constellation of Berenice's Hair (Coma Berenices).

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

https://webbtelescope.org/contents/news-releases/2025/news-2025-128

https://iopscience.iop.org/article/10.3847/2041-8213/add2f0

ASA Webb 'Pierces' Bullet Cluster, Refines Its Mass

June 30, 2025 10:00AM

Summary

Webb shows fainter and more distant galaxies, along with light from stars that trace dark matter in these galaxy clusters, helping researchers carefully map everything in the scene.

It’s rare for galaxy clusters to collide and merge at high speeds. An iconic example is the Bullet Cluster, the aftermath of two vast galaxy clusters that collided.

To be able to “replay” what happened, and in which order, researchers need to first fully define all the contents in this scene.

Full Article

NASA’s James Webb Space Telescope has provided some of the best information to date: Highly precise, extremely detailed near-infrared images of a significant portion of the Bullet Cluster.

Its new observations allowed researchers to fine tune their maps of its mass, including an invisible substance known as dark matter that does not emit, reflect, or absorb light.

NASA’s James Webb Space Telescope recently zeroed in on the Bullet Cluster — delivering highly detailed images that show a greater abundance of extremely faint and distant galaxies than ever before.

Using Webb’s crisp near-infrared observations of this region, researchers have more completely mapped the colliding galaxy clusters’ contents.

“With Webb’s observations, we carefully measured the mass of the Bullet Cluster with the largest lensing dataset to date, from the galaxy clusters’ cores all the way out to their outskirts,” said Sangjun Cha, the lead author of the paper published in The Astrophysical Journal Letters and a PhD student at Yonsei University in Seoul, South Korea.

(Previous studies of the Bullet Cluster with other telescopes relied on significantly less lensing data, which netted out with less precise estimates of the system’s mass.)

“Webb’s images dramatically improve what we can measure in this scene — including pinpointing the position of invisible particles known as dark matter,” said Kyle Finner, a co-author and an assistant scientist at IPAC at Caltech in Pasadena, California.

Mapping the Dark Matter

All galaxies are made up of stars, gas, dust, and dark matter, which are bound together by gravity. The Bullet Cluster is made up of two very massive collections of galaxies, known as galaxy clusters, that are themselves bound by gravity.

These galaxy clusters act as gravitational lenses, magnifying the light of background galaxies. “Gravitational lensing allows us to infer the distribution of dark matter,” said James Jee, a co-author, professor at Yonsei University, and research associate at UC Davis in California.

To visualize gravitational lensing and dark matter, think of a pond filled with clear water and pebbles. “You cannot see the water unless there is wind, which causes ripples,” Jee explained.

“Those ripples distort the shapes of the pebbles below, causing the water to act like a lens.” The same thing happens in space, but the water is dark matter and the pebbles are background galaxies.

In all, the team measured thousands of galaxies in Webb’s images to accurately “weigh” both the visible and invisible mass in these galaxy clusters.

They also carefully mapped and measured the collective light emitted by stars that are no longer bound to individual galaxies — known as intracluster stars.

The revised map of the Bullet Cluster is shown in a new image: Layered on top of an image from Webb’s NIRCam (Near-Infrared Camera) is data from NASA’s Chandra X-ray Observatory that shows hot gas in pink, including the bullet shape at right.

Refined measurements of the dark matter, calculated by the team using Webb’s observations, are represented in blue. (See the defined galaxy clusters within the dashed circles.)

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Their findings are persuasive: “We confirmed that the intracluster light can be a reliable tracer of dark matter, even in a highly dynamic environment like the Bullet Cluster,” Cha said.

If these stars are not bound to galaxies, but to the cluster’s dark matter, it might become easier to pin down more specifics about the invisible matter.

Viewed as a whole, the researchers’ new measurements significantly refine what we know about how mass is spread throughout the Bullet Cluster.

The galaxy cluster on the left has an asymmetric, elongated area of mass along the left edge of the blue region, which is a clue pointing to previous mergers in that cluster.

Dark matter does not emit, reflect, or absorb light, and the team’s findings indicate that dark matter shows no signs of significant self-interaction.

If dark matter did self-interact in Webb’s observations, the team would see an offset between the galaxies and their respective dark matter.

“As the galaxy clusters collided, their gas was dragged out and left behind, which the X-rays confirm,” Finner said. Webb’s observations show that dark matter still lines up with the galaxies — and was not dragged away.

Although earlier measurements with other telescopes also identified invisible mass in addition to the mass in the galaxies, it was still possible that the dark matter could interact with itself to some degree.

These new observations place stronger limits on the behavior of dark matter particles.

'Replaying' the Collision

The strange new clumps and elongated line of mass the team identified may mean that the Bullet Cluster was produced by more than one collision of galaxy clusters billions of years ago.

The larger cluster, which now sits on the left, might have suffered a minor collision before it rammed through the galaxy cluster now at right.

The same larger cluster may also have experienced a violent interaction afterward, causing an additional shake up of its contents. “A more complicated scenario would lead to a huge asymmetric elongation like we see on the left,” Jee said.

The Head of a 'Giant'

The Bullet Cluster is huge, even in the vast expanse of space. Webb’s NIRCam covered a significant portion of the hulking debris with its images, but not all of it. “It’s like looking at the head of a giant,” said Jee.

“Webb’s initial images allow us to extrapolate how heavy the whole 'giant' is, but we’ll need future observations of the giant’s whole 'body' for precise measurements.”

In the near future, researchers will also have expansive near-infrared images from NASA’s Nancy Grace Roman Space Telescope, which is set to launch by May 2027.

“With Roman, we will have complete mass estimates of the entire Bullet Cluster, which would allow us to recreate the actual collision on computers,” Finner said.

The Bullet Cluster is found in the Carina constellation 3.8 billion light-years from Earth.

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Update: DMSP Data Discontinuation Date Changed

June 30, 2025

As of late last Friday, June 27th, the Defense Meteorological Satellite Program (DMSP) will now cease processing of all of their data products including, the Special Sensor Microwave Imager/Sounder (SSMIS) and Special Sensor Microwave/Imager (SSM/I) data, by July 31, 2025.

We will follow up with a complete list of data products affected and potential solutions for continuing research.

This announcement was originally posted on June 25, 2025, by the National Oceanic and Atmospheric Administration and updated on June 27, 2025.

Please reach out to Earthdata Support if you have any questions or need assistance with the transition.

https://www.earthdata.nasa.gov/news/update-dmsp-data-discontinuation-date-changed

https://www.ospo.noaa.gov/data/messages/2025/06/MSG_20250625_1735.html

Streaming 4K from the Moon: NASA tests high-speed laser communication

06-30-2025 at 10:22

NASA and the Australian National University are testing the technology high-speed laser communication between the Earth and the Moon.

It is noted that if the new technology successfully proves itself within the Artemis II mission, this will confirm that laser communication systems for deep space are ready for use.

Laser communications allow for 4K video transmission from the Moon to Earth and record-breaking data rates.

Currently, most spacecraft still use radio communications to transmit data to Earth, but laser systems are capable of transmitting data 10-100 times faster.

Using infrared light, these systems can transmit high-quality video, clear voice, and other data to Earth over distances of hundreds of thousands of kilometers in just a few seconds.

Artemis II will be the first time astronauts will try laser communication from deep space.

The key element of the system is the RealTOR real-time optical receiver. It was assembled from common off-the-shelf parts, reducing the cost.

After successful tests in Cleveland, a similar device is currently being assembled by specialists from the Australian National University for further use in the Artemis II mission, which involves astronauts flying around the Moon.

During the Artemis II mission, scheduled for early 2026, the optical laser communication system will be launched aboard the Orion spacecraft.

About NASA will try to transmit recorded 4K ultra-high-definition video, flight process, photos, scientific data, and voice messages from the Moon to Earth.

The ground station will be a test site for the new receiver design and will not be one of the main ground stations of the mission.

While NASA continues to explore the possibility of using commercial parts to design ground stations, the researchers will continue to provide important support in preparation for the demonstration in Australia.

The RealTOR project is one of the phases of optical communications testing under NASA’s SCaN program, which includes demonstrations and experimental platforms in space to test the effectiveness of infrared light for sending data into space and to Earth.

These include the LCOT (Low-Cost Optical Terminal) project, a demonstration of laser communications relay, and more.

https://itc.ua/en/news/streaming-4k-from-the-moon-nasa-tests-high-speed-laser-communication/

NASA Headquarters Budget Protest On Monday

June 29, 2025

As noted last week there will be a protest outside of NASA Headquarters in Washington, DC from 7:00-11:00 am EDT on Monday, 30 June 2025. Information about the event can be found here.

This event has obtained a formal permit from Metro DC Police. The event is endorsed by the Goddard Engineers, Scientists, and Technicians Association (GESTA). But NASA HQ management is not happy about this.

This event is not endorsed by and does not represent the views of NASA or any employer doing business with NASA. But you would be wise to be aware of your surroundings and who may be watching you.

The employee union is spreading in accurate information by mentioning the word “strike” – which this is not – and no one has ever said it was.

Here is what the organizers, NASA employees union, NASA management, and the NASA HQ union says: (More below)

According to the Protest Organizers: “About: This is NOT a picket line. We will not attempt to prevent or dissuade anyone from entering the building.

The intent of this protest is to raise public awareness and provide information about present and near-future cuts at NASA, and to DEMAND that the Trump administration, including OMB and DOGE, cease all pressure on NASA to make cuts until Congress has had an opportunity to pass the next budget.

We just want to give Congress time. Who can share, and who can attend: Anyone can share this event. Be VERY careful not to do so on government time or using government resources, and to make sure you can’t be construed as representing the government.

Anyone can attend this event. NASA personnel attending this event should be off-duty, such as using leave, and should take care that they cannot be construed as representing the government. For more information: https://sites.google.com/view/nasa-needs-help“

On 27 June 2025 The senior management of NASA inside the Administrator’s suite sent out an email to all NASA HQ employees: “NASA Headquarters Team, A demonstration is scheduled to take place outside NASA Headquarters from 7 to 11 a.m. EDT on Monday, June 30.

The demonstration is permitted by the Metro DC Police. Traffic in the area may be affected during this time. NASA Headquarters will remain open, and employees are expected to report onsite.

Please plan accordingly and allow extra time for travel. As always, please exercise caution and stay aware of your surroundings. As a reminder, only authorized personnel are permitted to speak on behalf of the agency.

If you have any media reach out to you directly, please have them contact the NASA Headquarters newsroom at 202-358-1600, or by emailing: hq-media@mail.nasa.gov.

Our team remains in close coordination with local authorities and will monitor any developments related to the event. Please stay tuned to the NASA SAFE app for latest building updates. Thank you.”

On 28 June 2025 and email to members from Ann Cuyler, President, NASA Headquarters Professional Association (NHPA), Local 9 International Federation of Professional and Technical Engineers (IFPTE) was sent ot its members:

“Reminder from NASA Headquarters Professional Association (NHPA) Bargaining Unit Employees (BUEs): Below is a scheduled protest by contractors from Goddard Space Flight Center (GSFC); not NASA Union Local 29, GESTA in front of NASA-HQ.

I am notifying you are not allowed to strike. I understand the frustration but I don’t want any NASA employees to get caught up in something you may regret later with agitators and disruptors who may not have the same intention which is indicated in the information below.

THANX in advance to your service to NASA!! This was followed with a link and text hosted at the organizers website.”

https://nasawatch.com/activism/nasa-headquarters-budget-protest-on-monday/

https://sites.google.com/view/nasa-needs-help

https://www.thetravel.com/nasa-satellite-images-of-iliamna-volcano-alaska-avalanche/

https://twitter.com/konstructivizm/status/1937444588169625705

NASA Just Confirmed Satellite Image Of U.S. Volcano "Ready To Rumble"

June 30, 2025

From the very beginnings of human civilization, people have had to defend themselves from neighboring tribes and crusaders who sought to plunder other communities of their people and resources.

No matter how mighty and robust the fortifications of these civilizations were, humans have always had to battle against the mightiest and most unpredictable foe of all: Mother Nature.

Given that planet Earth is a uniquely alive planet, earthquakes, volcanoes, and weather-related natural disasters have plagued humanity from the beginning, toppling even the tallest and thickest stone walls and burying entire cities under layers of ash.

The ancient city of Pompeii, which sits in the shadows of Mt. Vesuvius and still reveals incredible archaeological finds in the modern day, serves as a prime example of the might of nature and the apocalyptic damage that a volcanic eruption can have on a city.

However, volcanic eruptions continue to plague modern civilizations today; in fact, just recently, new NASA satellite photos have revealed intimate snapshots of a massive volcano in the United States, which has been at the center of some recent and intriguing seismic activity.

NASA Photo Reveals Causes Of Seismic Activity At The Iliamna Volcano

Scientists at the National Aeronautics and Space Administration (NASA) have spotted some eyebrow-raising activity at a massive volcano that sits roughly 100 miles from Alaska's largest city.

These discoveries come just after NASA scientists confirmed that the largest tsunami in history is still visible from space after six decades, which is also located in Alaska.

According to NASA, the Iliamna Volcano has continued to show signs of seismic and other geological activity, to the extent that some scientists claim it is "ready to rumble."

The Iliamna volcano sits only 100 miles away from Anchorage, Alaska, home to nearly 300,000 people and one of the world's busiest airports, with massive amounts of cargo passing through Anchorage daily.

Researchers, including those with NASA, have recently recorded several tremors and other geological activity at this massive volcano, which could serve as an early indicator for further geological activity and perhaps even an eruption.

However, scientists at the Alaska Volcano Observatory are not convinced that these tremors are indicative of an upcoming eruption, ensuring Alaskans that avalanches caused this series of earthquakes.

More specifically, the Alaska Volcano Observatory released a statement on the matter, explaining that "An increase in seismicity, marked by frequent small earthquakes, has been observed at Iliamna Volcano beginning at about 4:30 am AKDT (12:30 UTC), June 15, 2025.

This activity is likely not caused by volcanic unrest."

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Although it appears that avalanches are to blame for the concerning activity surrounding the Iliamna volcano, scientists will continue to monitor any activity in this highly geologically active part of Alaska, ensuring that the thousands of people who live near this volcano have as much time as possible to prepare in case of an eruption.

The Pacific coast of Alaska sits along a massive horseshoe-shaped fault line that runs from South America, up the coast of North America, curving around the Northern Pacific, and running down the coast of Japan.

This massive geological feature is known as the Ring of Fire, which has shaped the landscape of the Pacific Ocean and the continents that run along it for millions of years.

Earthquakes and volcanic activity have long defined the lives of Alaskans, well before the first Europeans explored the area.

The Iliamna Volcano itself is ranked as the 20th deadliest volcano in the United States, with scientists fearing that an eruption could happen at any moment.

Nonetheless, people from across the world come to Alaska to see the Iliamna Volcano, which sits within the Lake Clark National Park and Reserve.

The name Iliamna originates from the Russian explorers who explored the area in the 18th century, who were among the first Europeans to explore and ultimately establish colonies in Alaska.

These colonies remained occupied until Russia sold Alaska for a meager $7.2 million (roughly $130 million in today's dollars) to the United States in 1867.

Alaska ultimately became the 49th state in 1959 and currently serves as a vitally important source of fish, oil, and valuable minerals, including gold.

Tourism also accounts for a massive chunk of Alaska's economy, with millions of people visiting the state every year. This massive flood of tourism has even started to overwhelm some Alaskan communities, which have taken action to scale back tourism.

Few natural disasters have the potential to devastate humanity as volcanoes do, evidenced by the horrific remains of the ancient city of Pompeii in Italy. Although many of Alaska's volcanoes sit far away from any large population centers, the Iliamna Volcano sits only about 100 miles from Alaska's largest city, Anchorage.

Anchorage serves as a major hub for trade and commerce, serving as a vital link between Asia and North America, and a volcanic eruption near this large city would severely impact the lives of millions of people across the world.

But as the Alaska Volcano Observatory notes, the recent tremors at the Iliamna volcano likely do not indicate any upcoming eruptions. However, volcanoes are known for being unpredictable, and the Iliamna Volcano could blow at any given moment.

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