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Astronomers have observed an accreting white dwarf abruptly lose and gain its brightness for the first time. White dwarfs are stars that have run out of their basic fuel: hydrogen. Usually, researchers have observed white dwarfs losing their brightness over days or months. Astronomers were studying the white dwarf binary system, TW Pictoris, and the white dwarf in it lost its brightness in 30 minutes, which surprised astronomers. Astronomers said it was accreting, or feeding on the energy from an orbiting companion star. To observe the unique phenomenon, astronomers used NASA’s Transiting Exoplanet Survey Satellite (TESS) that helps in planet-hunting processes.

The brightness of a white dwarf is not dependent on its own hydrogen source, as it has already exhausted it. Its brightness depends on the amount of surrounding material that it feeds on. The abrupt switching on and off of the white dwarf may be due to some interference with food supply, said researchers.

The research was led by England’s Durham University. The findings were published on October 18, 2021, in the Nature Astronomy journal.

TW Pictoris comprises a white dwarf and a smaller companion star. The white dwarf feeds from the accretion disc that is fuelled by hydrogen and helium from the companion star. The more energy it feeds on, the brighter it becomes.

Researchers noticed the abrupt rise and fall in the brightness of this white dwarf, the likes of which they had never seen before. They believe this could be caused by reconfiguration of the white dwarf’s surface magnetic field.

At its brightest phase, the white dwarf feeds off the accretion disc. But suddenly the magnetic field starts spinning so rapidly that a centrifugal barrier is created. This stops the fuel from the accretion disc to reach the white dwarf.

The “magnetic gating” regulates the fuel passing from the disc to the white dwarf. Due to the small amount of fuel passing through the “gate” the white dwarf experiences semi-regular small increases in brightness.

Then, the system switches “on” again, allowing the white dwarf to feed normally from the disc. The brightness reaches its peak again.

Lead author Dr. Simone Scaringi said, “This really is a previously unrecognised phenomenon and because we can draw comparisons with similar behaviour in the much smaller neutron stars it could be an important step in helping us to better understand the process of how other accreting objects feed on the material that surrounds them and the important role of magnetic fields in this process.”

This extraordinary observation could lead to further studies of white dwarfs and neutron stars.

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SpaceX’s Starship to Deploy Mock Starlink Satellites in Flight 7 Test

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January 4, 2025

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SpaceX's Starship to Deploy Mock Starlink Satellites in Flight 7 Test

Elon Musk’s SpaceX said on Friday its upcoming Starship test flight would include the rocket’s first attempt to deploy payloads in space by releasing 10 model Starlink satellites, a key demonstration for Starship’s potential in the satellite launch market.

“While in space, Starship will deploy 10 Starlink simulators, similar in size and weight to next-generation Starlink satellites as the first exercise of a satellite deploy mission,” SpaceX said in a blog post on its website.

The Starship flight from SpaceX’s sprawling Boca Chica, Texas facilities, tentatively planned for later this month, will mark the seventh demonstration in a test-to-failure style of rocket development where the company tests new upgrades with each flight.

In October, Starship’s “Super Heavy” first stage booster returned to its launch pad’s giant mechanical arms for the first time, a milestone for its fully reusable design.

The rocket’s sixth test flight in November, attended by U.S. President-elect Donald Trump, achieved similar mission objectives – besides the landing of Super Heavy, which was forced to target a water landing on the Gulf of Mexico because of a launchpad problem.

Starship is the centerpiece of SpaceX’s future satellite launch business – an area it currently dominates with its partially reusable Falcon 9 – as well as Musk’s dreams to colonize Mars.

The rocket’s power, stronger than the Saturn V rocket that sent Apollo astronauts to the moon in the last century, is key for launching huge batches of satellites into low-Earth orbit and is expected to rapidly expand the company’s Starlink satellite internet network.

SpaceX is under contract with NASA to land U.S. astronauts on the moon later this decade using Starship.

Musk, SpaceX’s founder and CEO, has become a close ally of Trump who has made getting to Mars a more prominent goal for the incoming administration.

© Thomson Reuters 2024

(This story has not been edited by NDTV staff and is auto-generated from a syndicated feed.)

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Are There Binary Black Holes at the Heart of Galaxies

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January 3, 2025

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Are There Binary Black Holes at the Heart of Galaxies

Supermassive black holes are believed to exist at the centre of most galaxies, including our Milky Way. However, in certain cases, two such black holes are thought to orbit one another, forming binary systems. These gravitationally bound pairs could provide significant insights into the dynamics of galaxy formation and the behaviour of space-time. Detecting them, however, presents challenges due to their nature, as they cannot be observed directly using traditional telescopes.

Gravitational Waves and Galactic Collisions

According to research, as reported by The Conversation, binary black holes can form when galaxies merge. During such collisions, the black holes from the merging galaxies are brought closer by gravitational forces. Eventually, they may create a binary system before combining into one larger black hole over millions of years.

These systems emit gravitational waves, ripples in space-time predicted by Albert Einstein’s theory of general relativity. Observatories like the Laser Interferometer Gravitational-Wave Observatory (LIGO) detect these waves, though pinpointing individual binaries remains elusive.

Evidence from Active Galactic Nuclei

Researchers have identified a potential binary black hole system in an active galaxy, PG 1553+153, as reported by The Conversation. Observations have revealed periodic light variations approximately every 2.2 years, which could indicate the presence of two orbiting black holes.

Active galactic nuclei, which emit immense energy due to gas accretion, often display such cyclical patterns. These patterns, however, might also result from other phenomena like jet wobbles, requiring further investigation.

Historical Data and Findings

As reported by The Conversation, they used archival data spanning over a century, a secondary 20-year light variation pattern was identified in PG 1553+153. This additional evidence supports the binary black hole hypothesis, suggesting the system includes two black holes with masses in a 2.5:1 ratio. Final confirmation, however, may depend on advancements in pulsar timing arrays to detect specific gravitational waves.

The study highlights how historical data and modern simulations contribute to understanding complex cosmic events. The findings advance knowledge of galactic evolution and black hole behaviour, with future technological improvements expected to refine these discoveries.

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Battle Site Between Alexander the Great and Ancient Persians Discovered

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January 3, 2025

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Battle Site Between Alexander the Great and Ancient Persians Discovered

The site of Alexander the Great’s decisive Battle of the Granicus against the Persian Empire appears to have been uncovered in northwest Turkey. Archaeologists have pinpointed the location roughly 10 kilometres north of Biga, where the famed confrontation occurred in 334 B.C. This victory allowed Alexander to establish a critical foothold in Persian territory, marking a pivotal moment in his campaign and reshaping the trajectory of ancient history. Evidence unearthed at the site includes remains of the ancient city of Hermaion, believed to have been Alexander’s final encampment before the battle.

Findings Based on Historical and Scientific Evidence

According to a report by Live Science, the team led by Reyhan Körpe, an archaeology professor at Çanakkale Onsekiz Mart University, carried out extensive research to validate the battlefield’s location. Historical records describing the terrain were compared with modern geomorphological studies. These studies revealed that the Granicus River’s path has remained largely unchanged since ancient times, while nearby marshy areas were ruled out as potential sites for the battle.

Further supporting the discovery were findings from Hermaion, including graves unearthed by local farmers in 2024. Among these, human bones discovered on a hillside believed to have housed Persian Greek mercenaries were examined. While the absence of grave markers suggests an informal burial, tests are ongoing to determine the age and cause of death of the remains.

Next Steps in Excavation

Plans for geophysical surveys and detailed digs have been announced to explore the site’s deeper layers and provide more insights into this historic confrontation. The team’s work offers a glimpse into Alexander’s military strategy and the broader impact of his campaigns on ancient civilisations.

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