Tag Archives: merger

Hubble Discovers Remnants of a White Dwarf Merger 130 Light Years Away

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The White Dwarf represents the compact core that forms when stars exhaust their fuel and collapse. These remnants are the ashes of Earth-sized stars, typically about half the mass of the Sun, composed of carbon-oxygen cores surrounded by layers of helium and hydrogen. Utilizing far-ultraviolet data from the NASA/ESA Hubble Space Telescope, astronomers have identified carbon in the atmosphere of the famously large white dwarf WD 0525+526. They also determined that the overall mass of hydrogen and helium in the star’s atmosphere was significantly lower than anticipated based on single-star evolution.

An illustration of a merger with a white dwarf sub-huge star (size without scale) that would have occurred in the past. Image credit: Snehalata Sahu/Warwick University.

WD 0525+526 is located approximately 130 light years away in the constellation Auriga.

With a mass exceeding that of our Sun by 20%, this white dwarf is classified as a super-genocide, and its formation process remains poorly understood.

Typically, such white dwarfs form from the collapse of massive stars. However, Hubble’s UV data indicates that WD 0525+526 has a hydrogen-rich atmosphere originating from its core.

“In optical light, WD 0525+526 appears to be a massive yet typical white dwarf,” remarked Sneharata Saff, an astronomer at the University of Warwick.

“However, the ultraviolet observations from Hubble allowed us to detect faint carbon signatures that optical telescopes could not observe.”

“The presence of a small amount of carbon in the atmosphere suggests that this massive white dwarf is likely the product of a merger between two stars.”

“We also believe that many similar merged remnants may pose as white dwarfs in a predominantly hydrogen atmosphere.”

“Only ultraviolet observations can reveal them to us.”

Typically, hydrogen and helium create dense, barrier-like layers around the white dwarf core, concealing carbon-rich elements.

In a stellar merger, the hydrogen and helium enveloping layers can burn away almost entirely as the stars combine.

The resulting single star possesses a very thin envelope that does not prevent carbon from surfacing, which is precisely what is observed in WD 0525+526.

“We found that the hydrogen and helium layers are around one billion times thinner than those typical of a white dwarf,” noted Antoine Bedard, an astronomer at Warwick University.

“We believe these layers were stripped away during the merger, allowing carbon to manifest on the surface.”

“However, this phenomenon is also unusual, as the carbon present is about 100,000 times less than that found on the surfaces of other merged remnants.”

“Coupled with the star’s elevated temperatures—nearly four times hotter than the Sun—the diminished carbon levels suggest that WD 0525+526 evolves at a much faster pace than previously observed.”

This discovery will aid in understanding the destiny of binary star systems, which are crucial for related phenomena such as supernova explosions.

Alongside the enigma, this significantly hotter star’s carbon migrates to the surface.

Other merged remnants later cool enough for convection to bring carbon to the surface; however, WD 0525+526 remains too hot for this process.

Instead, the author identified a subtle mixing process known as semiconvection, uniquely observed in this White Dwarf.

This mechanism permits small amounts of carbon to gradually ascend into the star’s hydrogen-rich atmosphere.

“Finding conclusive proof of individual white dwarf mergers is rare,” remarked Professor Boris Gensick from Warwick University.

“Yet, ultraviolet spectroscopy enables us to detect these signals early, while carbon remains invisible at optical wavelengths.”

“Because the Earth’s atmosphere filters out UV rays, such observations must be conducted from space—currently, only Hubble is capable of this.”

“As WD 0525+526 continues to evolve and cool, we anticipate more carbon will emerge at the surface over time.”

“For now, this ultraviolet illumination offers rare insights into the early aftermath of stellar mergers.

Survey results are published today in the journal Nature Astronomy.

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S. Saff et al. The remnants of Hot White Dwarfs revealed by ultraviolet detection of carbon. Nature Astronomy Published online on August 6th, 2025. doi:10.1038/s41550-025-02590-y

Source: www.sci.news

ARP 105: Hubble Captures Ongoing Merger of Two Massive Galaxies

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The ARP 105 features star and gas tide tails that exceed 362,000 light years.

The elliptical galaxy NGC 3561B (top left) and the Spiral Galaxy NGC 3561A (bottom right) form the ongoing merger-sparking guitar shapes known comprehensively as ARP.

ARP 105 It is located approximately 400 million light years from Earth, in the constellation of Ursa major.

Also known as NGC 3561, it was discovered by British astronomer John Herschel on March 30, 1827.

It consists of two huge galaxies, the elliptical galaxy NGC 3561B and the Spiral Galaxy NGC 3561A.

“The ARP 105 is one of the brightest objects in the busy Galaxy Cluster Abell 1185,” Hubble Astronomers said in a statement.

“Abell 1185 is a chaotic cluster of at least 82 galaxies, many of which are not only interacting, but many wandering spherical clusters that are not gravity attached to a particular galaxy.”

The gravity dance between the NGC 3561B and NGC 3561A creates the features of an attractive collision galaxy.

“The giant tail is drawn from two galaxies by gravity interaction, embedding a cluster of stars and a galaxy of d star,” the astronomer said.

“The uniquely shaped arrangement of the galaxy and tail gives the grouping the nickname: guitar.”

“The long lanes of dark dust emerging from the NGC 3561b oval galaxy may be ingesting the bright blue region of star-forming at the bottom of the guitar known as Ambartsumian's Knot.”

“Ambartsumian's Knot is a tidal star galaxy. It is a type of star-forming system that develops from fragments of the tidal arms of interacting galaxies.”

“The two bright blue regions of star formation are evident in Hubble images at the edge of a distorted helical galaxy.”

“The region on the left of the spiral galaxy may be very similar to the knot of Ambartumian, the knot of intense star-forming knot caused by the merger.”

“The area on the right is still under investigation. It may be part of the collision, but its velocity and spectral data are different from the rest of the system, so it could be a galaxy in the foreground.”

“The thin, faint gas tips are barely visible that stretch between two galaxies.”

“These tendrils are of particular interest to astronomers as they may help define the timescale of this collision evolution.”

Source: www.sci.news

The Milky Way’s most recent major merger occurred billions of years later than previously believed

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The discovery was made possible by ESA’s Gaia spacecraft, which is mapping more than a billion stars across the Milky Way galaxy and beyond, tracking their motions, brightness, temperature, and composition.

This image visualizes the Milky Way and its surrounding halo of stars. New Gaia data reveals that the wrinkles seen in the Milky Way are likely the result of a dwarf galaxy colliding with the Milky Way about 2.7 billion years ago. Our galaxy’s two major satellite galaxies, the Large and Small Magellanic Clouds, are visible at the bottom right. Image credit: ESA / Gaia / DPAC / Donlon other./ Stephen Payne Waldenaar.

The Milky Way galaxy has grown over time as other galaxies have approached, collided, been torn apart, and been swallowed up.

Each collision still sends ripples through different groups of stars, influencing their movements and behavior in space.

One of Gaia’s goals is to study these wrinkles to unravel the history of our Milky Way galaxy. It does this by pinpointing the positions and motions of more than 100,000 stars close to Earth, a tiny fraction of the roughly 2 billion objects it observes.

“As we age, we tend to get more wrinkles, but our research shows that the opposite is true in the Milky Way – it’s like a cosmic Benjamin Button, and it gets less wrinkled over time,” said Dr. Thomas Donlon, an astronomer at Rensselaer Polytechnic Institute and the University of Alabama.

“By looking at how these wrinkles fade over time, we can trace when the Milky Way last experienced a major collision — and it turns out this happened billions of years later than we thought.”

The Milky Way’s halo contains many stars with unusual orbits, many of which are thought to have been incorporated into the galaxy in an event that astronomers call the last great merger.

As the name suggests, this is the last time the Milky Way has experienced a significant collision with another galaxy, which is proposed to have been a giant dwarf galaxy that smothered the Milky Way with stars passing very close to the center of the Milky Way.

Astronomers estimate that the merger occurred between 8 and 11 billion years ago, when the Milky Way was still in its infancy, and is known as Gaia-Sausage-Enceladus.

But data from Gaia’s Data Release 3 suggests that another merger could have resulted in the unusually behaving star.

“For the stellar wrinkles to be as clear as we see in the Gaia data, the stars would have had to have appeared on Earth less than 3 billion years ago — at least 5 billion years later than previously thought,” said Dr. Heidi Jo Neuberg, also of Rensselaer Polytechnic Institute.

“Every time a star passes back and forth through the center of the Milky Way, a new stellar wrinkle forms.”

“If they had merged with us 8 billion years ago, there would have been so many wrinkles next to each other that we wouldn’t be able to see them as separate features.”

This discovery suggests that these stars did not result from the ancient Gaia-Sausage-Enceladus merger, but must have arisen from a more recent event called the Virgo radial merger, which occurred less than 3 billion years ago.

“The history of the Milky Way is currently being constantly rewritten, thanks in large part to new data from Gaia,” Dr. Donlon said.

“Our image of the Milky Way’s past has changed dramatically since even 10 years ago, and I think our understanding of these mergers will continue to change rapidly.”

“This finding that most of the Milky Way galaxy joined Earth within the last few billion years is quite different from what astronomers previously thought.”

“Many prevailing models and ideas about the growth of the Milky Way predict that a recent head-on collision with a dwarf galaxy of this mass would be extremely rare.”

“The Virgo radial merger likely pulled in a group of other small dwarf galaxies and star clusters, all of which joined the Milky Way at about the same time.”

“Future exploration will reveal which of these small objects previously thought to be related to the ancient Gaia sausage Enceladus are in fact related to the recent Virgo radial merger.”

of Investigation result Appears in Monthly Bulletin of the Royal Astronomical Society.

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Thomas Donlon otherThe year is 2024. The remains of the “last great merger” are dynamically young. MNRAS 531(1):1422-1439; doi:10.1093/mnras/stae1264

Source: www.sci.news

The merger of quantum biology and AI fueled genome editing advancements

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Scientists at Oak Ridge National Laboratory have utilized quantum biology and explainable artificial intelligence to advance CRISPR Cas9 technology for genome editing in microorganisms. This breakthrough has enabled more precise genetic modification of microorganisms, opening up possibilities for the production of renewable fuels and chemicals. The research at Oak Ridge National Laboratory has significantly improved the efficiency of CRISPR Cas9 genome editing in microorganisms and contributed to renewable energy development.

CRISPR is a powerful tool for bioengineering, used to modify the genetic code to improve the performance of organisms or correct mutations. ORNL scientists developed a method to improve the accuracy of the CRISPR Cas9 gene editing tool used to modify microorganisms for the production of renewable fuels and chemicals. They have leveraged their expertise in quantum biology, artificial intelligence, and synthetic biology to achieve this.

To improve the modeling and design of guide RNAs, ORNL scientists sought to better understand what is happening at the most fundamental level in the cell nucleus, where genetic material is stored. They turned to quantum biology to study how electronic structure affects the chemical properties and interactions of nucleotides, such as DNA and RNA.

Furthermore, scientists at ORNL have built an explainable artificial intelligence model called iterated random forest, which has been used to train the model on a dataset of about 50,000 guide RNAs targeting the genome of Escherichia coli. This model has provided important features regarding the nucleotides that allow for better selection of guide RNAs.

Improving the CRISPR Cas9 model provides scientists with a high-throughput pipeline for linking genotype to phenotype in functional genomics. This research will impact efforts at the ORNL-led Center for Bioenergy Innovation (CBI), such as improving bioenergy feedstock plants and bacterial fermentation of biomass.

The results of this research significantly improve the prediction of guide RNAs. This represents an exciting advance toward understanding how avoid ‘mistakes’ and improving the ability to use CRISPR tools to predictively modify the DNA of more organisms. The study was funded by SEED SFA and CBI, part of the DOE Office of Science’s Biological and Environmental Research Program, ORNL’s Laboratory-Directed Research and Development Program, and OLCF and Compute’s High Performance Computing Resources and Data Environment for Science, both supported by the Office of Science.

Source: scitechdaily.com