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Astronomers have assembled the largest-ever compilation of high-precision galaxy distances, called Cosmicflows-4. Galaxies, such as the Milky Way, are the building blocks of the universe, each comprised of up to several hundred billion stars. Galaxies beyond our immediate neighborhood are rushing away, faster if they are more distant, which is a consequence of the expansion of the universe that began at the moment of the Big Bang. Measurements of the distances of galaxies, coupled with information about their velocities away from us, determine the scale of the universe and the time that has elapsed since its birth.

“Since galaxies were identified as separate from the Milky Way a hundred years ago, astronomers have been trying to measure their distances,” said Brent Tully, astronomer at the University of Hawaii at Manoa. “Now by combining our more accurate and abundant tools, we are able to measure distances of galaxies, and the related expansion rate of the universe and the time since the universe was born with a precision of a few per cent.”

From the newly published measurements, the researchers derived the expansion rate of the universe, called the Hubble Constant, or H0. The team’s study gives a value of H0=75 kilometers per second per megaparsec or Mpc (1 megaparsec = 3.26 million light years), with very small statistical uncertainty of about 1.5 percent.

There are a number of ways to measure galaxy distances. Generally, individual researchers focus on an individual method. The Cosmicflows program spearheaded by Tully and Kourkchiincludes their own original material from two methods, and additionally incorporates information from many previous studies. Because Cosmicflows-4 includes distances derived from a variety of independent, distinct distance estimators, intercomparisons should mitigate against a large systematic error.

Astronomers have assembled a framework that shows the universe’s age to be a little more than 13 billion years old, however, a dilemma of great significance has arisen in the details.

Physics of the evolution of the universe based on the standard model of cosmology predicts H0=67.5 km/s/Mpc, with an uncertainty of 1 km/s/Mpc. The difference between the measured and predicted values for the Hubble Constant is 7.5 km/s/Mpc – much more than can be expected given the statistical uncertainties. Either there is a fundamental problem with our understanding of the physics of the cosmos, or there is a hidden systematic error in the measurements of galaxy distances.

Cosmicflows-4 is also being used to study how galaxies move individually, in addition to flowing with the overall expansion of the universe. Deviations from this smooth expansion arise due to the gravitational influences of clumps of matter, on scales ranging from our Earth and Sun up to congregations of galaxies on scales of a half billion light years. The mysterious dark matter is the dominant component on larger scales. With knowledge of the motions of galaxies in response to the mass around them, we can recreate the orbits that galaxies have followed since they were formed, giving us a better understanding of how the universe’s vast, dark-matter-dominated structures have formed over the eons of time.

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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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