Merging black holes responsible for mysterious flickering quasar

Columbia researchers predict that a pair of converging supermassive black holes in the Virgo constellation will collide sooner than expected. Above, an artist’s conception of a merger. Illustration credit: P. Marenfeld/NOAO/AURA/NSF.

Earlier this year, astronomers found what seemed to be a pair of supermassive black holes heading towards a collision so strong it would generate a surge of gravitational waves through space-time. Now, in a study in the journal Nature, astronomers at Columbia University provide additional evidence that a pair of closely orbiting black holes is causing rhythmic flashes of light from quasar PG 1302-102. Based on calculations of the pair’s mass — together, and relative to each other — the researchers predict a collision 100,000 years from now, a long time for humans but a blink of an eye for a star or black hole. Spiraling together 3.5 billion light-years away, deep in the Virgo constellation, the pair is separated by a mere light-week. By contrast, the closest previously confirmed black hole pair is separated by 20 light-years.

“This is the closest we’ve come to observing two black holes on their way to a massive collision,” said the study’s senior author, Zoltan Haiman, an astronomer at Columbia. “Watching this process reach its culmination can tell us whether black holes and galaxies grow at the same rate, and ultimately test a fundamental property of space-time: its ability to carry vibrations called gravitational waves, produced in the last, most violent, stage of the merger.”

At the center of most giant galaxies, including our Milky Way, lies a supermassive black hole so dense that not even light can escape. Over time, black holes grow bigger — millions to billions times more massive than the Sun — by consuming stars, galaxies, and even other black holes. A supermassive black hole about to consume another can be detected by the mysterious flickering of a quasar, the beacon of light produced by black holes as they consume gas and dust swirling around them. Normally, quasars brighten and dim randomly, but when two black holes are about to unite, the quasar appears to flicker at regular intervals, like a light bulb on a timer.

Recently, a team led by Matthew Graham, a computational astronomer at the California Institute of Technology, designed an algorithm to identify repeating light signals from 247,000 quasars monitored by telescopes in Arizona and Australia. Of the 20 pairs of black hole candidates discovered, they focused on the most compelling bright quasar — PG 1302-102. In a January study in Nature, they showed that PG 1302-102 seemed to brighten by 14 percent every five years, indicating the pair was less than a tenth of a light-year apart.

Intrigued, Haiman and his colleagues wondered if they could build a theoretical model to explain the repeating signal. If the black holes were as close as predicted, one had to be circling a much larger counterpart at nearly a tenth of the speed of light, they hypothesized. At that speed, the smaller black hole would appear to brighten as it approached Earth’s line of sight under the relativistic Doppler beaming effect. If correct, they predicted they would find a five-year cycle in the quasar’s ultraviolet emissions — only two-and-a-half times more variable in its intensity. Analyzing UV observations collected by NASA’s Hubble and GALEX space telescopes, they found exactly that.

Previous explanations for the repeating signal include a warp in the debris discs orbiting the black holes, a wobble in the axis of one black hole, and a lopsided debris disc formed as one black hole draws material off the other — all creating the impression of a periodic flicker from Earth.

The new study introduces a novel method for studying the convergence of black holes, according to researchers. By determining the combined and relative mass of PG 1302-102's black holes, they have narrowed down the expected collision time for the pair to a range of 20,000 to 350,000 years from now, with the most likely estimate being around 100,000 years. (Previously, Graham's team had predicted a collision time of 10,000 to several million years from now, with a best estimate of 250,000 years). Study co-author David Schiminovich, an astronomer at Columbia, mentioned, "We are now able to quantify the rates at which black holes merge and form larger black holes, and this knowledge helps us in the search for more pairs of black holes." The increasing number of discoveries of binary black hole systems has raised hopes among astronomers that a collision may be observed within the next decade. Graham and his team recently reported 90 additional candidates, while astronomers at Columbia are expecting to announce their own findings soon based on data collected at California's Palomar Observatory. With a growing list of black holes under observation, the likelihood of witnessing a collision and detecting the gravitational waves predicted by Einstein's general theory of relativity, though not yet observed, is increasing. The lead author of the study, Daniel D'Orazio, a graduate student at Columbia, stated, "The detection of gravitational waves allows us to explore the mysteries of gravity and test Einstein's theory in the extreme environment of black holes. Achieving this goal is a major aspiration in our field."

Thirtieth anniversary of Voyager 2’s encounter with Uranus

Upon reaching Uranus on 24 January 1986, Voyager 2 encountered a blue sphere with very delicate features. A layer of haze obscured the majority of the planet's cloud characteristics. Uranus boasts a diameter four times that of Earth and completes an orbit around the Sun every 84 years, situated at a distance of 1.8 billion miles (2.9 billion kilometers) — 19 times farther away than our own planet. Image credit: NASA/JPL-Caltech.

Humanity visited Uranus only once, precisely 30 years ago when NASA's Voyager 2 spacecraft conducted a close study of the distant, mysterious, gaseous planet on 24 January 1986. The spacecraft captured and transmitted stunning images of Uranus and its moons during the flyby, allowing for approximately 5½ hours of detailed observation. Voyager 2 approached within 50,600 miles (81,500 kilometres) of Uranus during this encounter. Ed Stone, the project scientist for the Voyager mission at the California Institute of Technology in Pasadena, anticipated surprises due to Uranus's unique sideways orientation. Stone, who has been the project scientist since 1972, continues in that role to this day. Uranus emerged as the coldest planet in our solar system, despite not being the most distant from the Sun, as it lacks an internal heat source. Scientists determined that Uranus's atmosphere consists of 85 percent hydrogen and 15 percent helium, with indications of a boiling ocean approximately 500 miles (800 kilometres) beneath the cloud tops. The magnetic field of Uranus differed significantly from those of Mercury, Earth, Jupiter, and Saturn, with the poles being closer to the equator. Stone noted that Neptune exhibited a similar magnetic field misalignment. The surface magnetic field of Uranus was also stronger than Saturn's. Voyager 2 data revealed that Uranus's magnetic tail forms a helix stretching 6 million miles (10 million kilometres) in the direction opposite the Sun. Understanding the interaction between planetary magnetic fields and the Sun is crucial for NASA's mission to comprehend the nature of space. Exploring the Sun-planet connection not only offers insights valuable for space exploration but also illuminates the origins of planets and their potential to support life.

VVoyager 2 discovered 10 new moons, bringing the total to 27, along with two new rings at the planet. Miranda, an icy moon, unveiled a diverse landscape and signs of past geologic activity. Despite its small size of about 300 miles (500 kilometers) in diameter, Miranda features immense canyons, potentially up to 12 times deeper than the Grand Canyon in Arizona. Additionally, Miranda showcases three distinct structures known as "coronae," consisting of lightly cratered formations of ridges and valleys. Scientists speculate that this moon might have experienced fragmentation and subsequent reformation. Voyager 2's encounter with Uranus was meticulously planned to utilize a gravity assist for its journey towards Neptune. In 1989, Voyager 2 captured the first-ever close-up images of Neptune, expanding its impressive exploration repertoire. Suzanne Dodd, the project manager for Voyager at NASA's Jet Propulsion Laboratory in Pasadena, California, expressed her enthusiasm for the Uranus encounter, marking her first planetary mission to an uncharted celestial body. Voyager 2, launched on 20 August 1977, just 16 days ahead of its counterpart Voyager 1, is anticipated to venture into interstellar space in the coming years, following Voyager 1's historic milestone in August 2012.

Hubble looks to the Final Frontier on 50th anniversary of “Star Trek”

In the center of this NASA/ESA Hubble Space Telescope image lies the vast galaxy cluster Abell S1063, situated 4 billion light-years away and encircled by magnified views of galaxies much more distant. The cluster's immense mass distorts and amplifies the light from galaxies positioned far beyond it, a phenomenon known as gravitational lensing. This effect enables Hubble to detect galaxies that would otherwise be too diminutive and faint to observe. Abell S1063 boasts around 100 million-million solar masses, housing 51 confirmed galaxies and potentially over 400 more. Image credit: NASA, ESA, and J. Lotz (STScI). Marking its 50th anniversary this year, the TV series "Star Trek" has captivated the public with its iconic motto, "To boldly go where no one has gone before." While the NASA/ESA Hubble Space Telescope may not physically venture deep into space, it boldly peers farther into the cosmos than ever before, delving into the bending of space and time and revealing some of the most remote objects ever witnessed. When "Star Trek" premiered in 1966, Earth's largest telescopes could only observe about half the universe—beyond that lay uncharted realms. Yet, Hubble's remarkable vision has propelled us into the true "final frontier." This is exemplified in the latest Hubble image unveiled today to coincide with the release of the new film "Star Trek Beyond." The image showcases a universe teeming with galaxies, both nearby and distant, some distorted like a funhouse mirror due to a space-warping effect foreseen by Einstein a century ago. At its core, the vast galaxy cluster Abell S1063, positioned 4 billion light-years away, is surrounded by magnified views of galaxies much farther out. Thanks to Hubble's exceptional clarity, the image reveals the gravitational warping of space. The cluster's colossal mass distorts and amplifies the light from galaxies lying far behind it, courtesy of gravitational lensing. This phenomenon enables Hubble to observe galaxies that would otherwise be too minute and dim to perceive. This "warp field" offers a glimpse into the very first galaxies to exist. Already, an infant galaxy has been spotted in the field, resembling how it appeared 1 billion years post the Big Bang. This frontier image offers a sneak peek into the early universe, providing a preview of what the James Webb Space Telescope will unveil in greater detail upon its launch in 2018. The cluster houses roughly 100 million-million solar masses, with 51 confirmed galaxies and potentially over 400 more. The Frontier Fields program, initiated in 2013 as a daring three-year endeavor, combines Hubble with NASA's other Great Observatories—the Spitzer Space Telescope and the Chandra X-ray Observatory—to explore the early universe by scrutinizing vast galaxy clusters. Identifying the magnified images of background galaxies within these clusters will aid astronomers in refining their models of both ordinary and dark matter distribution within the galaxy cluster, crucial for unraveling the enigmatic nature of dark matter, which constitutes the majority of the universe's mass.

The dark matter conspiracy

Computer simulation of a galaxy, with the dark matter colorized to enhance visibility. Dark matter envelops and pervades the galaxy, playing a crucial role in its cohesion and the formation of stars and planets. Credit: Springel et al., Virgo Consortium, Max-Planck-Institute for Astrophysics. An international team of astronomers, led by Michele Cappellari from the University of Oxford, utilized data from the W. M. Keck Observatory in Hawaii to study the movements of stars in the outer regions of elliptical galaxies. This groundbreaking survey, the first of its kind capturing a large number of these galaxies, revealed unexpected gravitational similarities between spiral and elliptical galaxies, hinting at the presence of hidden forces. The findings of this study are set to be published in The Astrophysical Journal Letters. The research involved mapping and analyzing the velocities of stars in an elliptical galaxy. Blues indicate areas where stars are approaching the Earth observer rapidly, while reds signify regions moving away, forming a coherent rotational pattern. The top panel displays raw data collected using the DEIMOS spectrograph at the W.M. Keck Observatory, while the bottom panel showcases a numerical model that aligns closely with the data, accounting for the combined gravitational effects of luminous and dark matter. Credit: M. Cappellari and the SLUGGS team. Scientists from the USA, Australia, and Europe leveraged the DEIMOS spectrograph on the Keck Observatory's largest optical telescope to conduct a comprehensive survey of nearby galaxies known as SLUGGS, charting the velocities of their stars. They then applied Newton's law of gravity to translate these velocity measurements into the distribution of matter within the galaxies. According to Aaron Romanowsky from San Jose State University, "The DEIMOS spectrograph played a pivotal role in this discovery by capturing data from an entire massive galaxy simultaneously, while accurately sampling the velocities of its stars at a hundred distinct locations." One of the most significant scientific revelations of the 20th century was the realization that spiral galaxies, like our Milky Way, rotate at much higher speeds than anticipated, driven by an additional gravitational force from invisible "dark matter." This enigmatic substance, likely an exotic elementary particle, constitutes roughly 85 percent of the universe's mass, leaving only 15 percent for familiar matter encountered in daily life. Dark matter is fundamental to our comprehension of galaxy formation and evolution, playing a crucial role in the existence of life on Earth, yet its nature remains largely elusive. The velocities of stars on circular orbits have been scrutinized around both spiral and elliptical galaxies. In the absence of dark matter, velocities should decrease with distance from the galaxy, exhibiting varying rates for each galaxy type. However, dark matter seemingly conspires to maintain consistent speeds, a phenomenon depicted in the images. Credit: M. Cappellari and the Sloan Digital Sky Survey. Michele Cappellari remarked, "Our study's surprising revelation was the constancy of circular speeds in elliptical galaxies extending far from their centers, mirroring the behavior already observed in spiral galaxies." This alignment suggests a redistribution of stars and dark matter within these galaxies, with stars prevailing in the inner regions and a gradual transition to dark matter dominance in the outer regions. While this alignment challenges conventional dark matter models and necessitates some fine-tuning to explain the observations, it raises the possibility that deviations in Newton's law of gravity at large distances could offer an alternative explanation. Despite being proposed decades ago, this alternative theory excluding dark matter remains inconclusive. Spiral galaxies represent less than half of the universe's stellar mass, with elliptical and lenticular galaxies dominating and exhibiting denser star configurations devoid of the flat gas disks characteristic of spirals. The technical challenges in measuring the masses and dark matter distribution in these galaxies have been formidable until now. Due to their distinct shapes and formation histories compared to spirals, the newfound alignment in elliptical galaxies poses profound implications, prompting experts in dark matter and galaxy formation to reevaluate the mysteries of the "dark sector" of the universe. Professor Jean Brodie, principal investigator of the SLUGGS survey, highlighted the relevance of this inquiry in the current period, as physicists at CERN gear up to resume operations of the Large Hadron Collider in a bid to directly detect the elusive dark matter particle, which, if proven to exist, underpins the rapid rotation of galaxies.

First detection of element lithium from an exploding star

Alpha and Beta Centauri, two of the brightest stars in the southern sky, had a new companion in late 2013 — the naked eye Nova Centauri 2013. The iconic Southern Cross lies at top centre. This photo was taken by ESO Photo Ambassador Yuri Beletsky at ESO’s La Silla Observatory in the Chilean Atacama Desert in the morning hours of Monday, 9 December 2013. Image credit: Y. Beletsky (LCO)/ESO.

Alpha and Beta Centauri, two of the brightest stars in the southern sky, gained a new companion in late 2013 — the naked eye Nova Centauri 2013. The iconic Southern Cross lies at the top center. This photo was captured by ESO Photo Ambassador Yuri Beletsky at ESO’s La Silla Observatory in the Chilean Atacama Desert during the morning of Monday, December 9, 2013. Image credit: Y. Beletsky (LCO)/ESO. The chemical element lithium was discovered for the first time in material ejected by a nova. Observations of Nova Centauri 2013 using telescopes at ESO’s La Silla Observatory and near Santiago in Chile have helped to unravel the mystery behind why many young stars appear to possess more of this chemical element than anticipated. This new discovery fills a long-standing gap in the puzzle that represents our galaxy’s chemical evolution, marking a significant advancement for astronomers striving to comprehend the quantities of different chemical elements in Milky Way stars. Lithium, a light chemical element, is among the few elements predicted to have originated from the Big Bang approximately 13.8 billion years ago. However, understanding the observed amounts of lithium in stars within our Universe today has posed challenges for astronomers. Older stars exhibit less lithium than expected, while some younger ones show up to ten times more. Since the 1970s, astronomers have theorized that a substantial portion of the additional lithium present in young stars may have been sourced from novae — stellar explosions that release material into the interstellar space, contributing to the material that forms the subsequent generation of stars. Nonetheless, thorough examination of several novae has not yielded a definitive outcome thus far. A team led by Luca Izzo (Sapienza University of Rome and ICRANet, Pescara, Italy) utilized the FEROS instrument on the MPG/ESO 2.2-meter telescope at the La Silla Observatory, as well as the PUCHEROS spectrograph on the ESO 0.5-meter telescope at the Observatory of the Pontificia Universidad Catolica de Chile in Santa Martina near Santiago, to investigate the nova Nova Centauri 2013 (V1369 Centauri). This star underwent an explosion in the southern skies near the bright star Beta Centauri in December 2013 and stood out as the brightest nova in the 21st century — easily visible to the naked eye. This image from the New Technology Telescope at ESO’s La Silla Observatory depicts Nova Centauri 2013 in July 2015 as the brightest star at the center of the frame, more than eighteen months after the initial explosive event. This nova marked the first instance where evidence of lithium was identified. Nova Centauri 2013 is situated 11,000 light-years away. Image credit: ESO. The newly acquired detailed data unveiled a distinct signature of lithium being expelled at a speed of two million kilometers per hour from the nova. This marks the first detection of the element being ejected from a nova system to date. Co-author Massimo Della Valle (INAF–Osservatorio Astronomico di Capodimonte, Naples, and ICRANet, Pescara, Italy) elucidates the significance of this finding: “This is a crucial step forward. If we envision the Milky Way's chemical evolution history as a large puzzle, then lithium from novae was one of the most important and perplexing missing pieces. Furthermore, any model of the Big Bang can be called into question until the lithium enigma is unraveled.” The mass of ejected lithium in Nova Centauri 2013 is estimated to be minuscule (less than a billionth of the Sun's mass), yet given the numerous novae that have occurred throughout the Milky Way's history, this quantity suffices to account for the observed and surprisingly substantial amounts of lithium in our galaxy. Authors Luca Pasquini (ESO, Garching, Germany) and Massimo Della Valle have dedicated over a quarter of a century to searching for evidence of lithium in novae. This discovery is a gratifying conclusion to their prolonged quest. For the younger lead scientist, there is a different kind of excitement: “It is truly thrilling,” remarks Luca Izzo, “to uncover something that was predicted before my birth and then witnessed on my birthday in 2013!”

This image from the New Technology Telescope at ESO’s La Silla Observatory shows Nova Centauri 2013 in July 2015 as the brightest star in the centre of the picture. This was more than eighteen months after the initial explosive outburst. This nova was the first in which evidence of lithium has been found. Nova Centauri 2013 lies 11,000 light-years away. Image credit: ESO.

Q Continuum computer simulation models birth of universe

This series shows the evolution of the universe as simulated by a run called the Q Continuum, performed on the Titan supercomputer and led by Argonne physicist Katrin Heitmann. These images give an impression of the detail in the matter distribution in the simulation. At first the matter is very uniform, but over time gravity acts on the dark matter, which begins to clump more and more, and in the clumps, galaxies form. Image credit: Heitmann et. al.

Researchers are sifting through an avalanche of data produced by one of the largest cosmological simulations ever performed, led by scientists at the U.S. Department of Energy’s (DOE’s) Argonne National Laboratory.

The simulation, run on the Titan supercomputer at DOE’s Oak Ridge National Laboratory, modelled the evolution of the universe from just 50 million years after the Big Bang to the present day — from its earliest infancy to its current adulthood. Over the course of 13.8 billion years, the matter in the universe clumped together to form galaxies, stars, and planets; but we’re not sure precisely how.

This series illustrates the universe's evolution as simulated by the Q Continuum run on the Titan supercomputer, overseen by Argonne physicist Katrin Heitmann. These visuals depict the intricate matter distribution within the simulation. Initially, the matter exhibits uniformity, but as time progresses, gravity influences the dark matter, causing it to aggregate, leading to the formation of galaxies within these clusters. Image credit: Heitmann et. al. Researchers are analyzing vast amounts of data generated by one of the most extensive cosmological simulations ever conducted, led by experts at the U.S. Department of Energy’s (DOE’s) Argonne National Laboratory. Executed on the Titan supercomputer at DOE’s Oak Ridge National Laboratory, the simulation portrays the universe's development from a mere 50 million years post-Big Bang to the present day — from its nascent stages to its current state. Throughout 13.8 billion years, cosmic matter coalesced to give rise to galaxies, stars, and planets; however, the exact mechanisms remain uncertain. These simulations aid scientists in comprehending dark energy, a force influencing the universe's expansion rate, encompassing the distribution of galaxies comprising ordinary matter and enigmatic dark matter, which has eluded direct observation thus far. Extensive sky surveys conducted using advanced telescopes such as the Sloan Digital Sky Survey and the more detailed Dark Energy Survey pinpoint the locations of galaxies and stars at the time of their initial light emission. Additionally, investigations into the Cosmic Microwave Background, residual light from the universe's infancy at 300,000 years old, unveil the universe's initial state — described by Katrin Heitmann, the leading physicist at Argonne, as "initially uniform, with matter clustering over time." The simulation bridges the temporal gap, illustrating the universe's potential evolution: "Gravity influences dark matter, prompting increased aggregation and the eventual formation of galaxies," as stated by Heitmann.

Galaxies have halos surrounding them, which may be composed of both dark and regular matter. This image shows a substructure within a halo in the Q Continuum simulation, with “subhaloes” marked in different colours. Image credit: Heitmann et al.

The Q Continuum simulation involved half a trillion particles, dividing the universe into cubes with sides 100,000 kilometers long. This marks one of the largest cosmology simulations at such high resolution, utilizing over 90 percent of the supercomputer. Typically, less than one percent of jobs on the Mira supercomputer at Argonne use 90 percent of its capacity, as noted by officials at the Argonne Leadership Computing Facility. Staff from Argonne and Oak Ridge computing facilities collaborated to adapt the code for running on Titan. "This simulation is very comprehensive," stated Heitmann. "We can analyze why galaxies cluster in this manner, along with the fundamental physics of structure formation." Analysis has commenced on the two and a half petabytes of generated data, a process expected to continue for several years. Researchers can extract data on various astrophysical phenomena like strong lensing, weak lensing shear, cluster lensing, and galaxy-galaxy lensing. The simulation code, Hardware/Hybrid Accelerated Cosmology Code (HACC), was initially developed in 2008, coinciding with the era when scientific supercomputers surpassed the petaflop barrier. HACC's design flexibility allows it to operate on supercomputers with diverse architectures. The study detailing this work, titled "The Q Continuum Simulation: Harnessing the Power of GPU Accelerated Supercomputers," was published in August in the Astrophysical Journal Supplement Series by the American Astronomical Society. Additional scientists from Argonne involved in the study were Nicholas Frontiere, Salman Habib, Adrian Pope, Hal Finkel, Silvio Rizzi, Joe Insley, and Suman Bhattacharya, alongside Chris Sewell from DOE's Los Alamos National Laboratory.

Dark energy explained by relativistic time dilation?

Timeline of the universe. Image credit: NASA/WMAP Science Team

In the recent Hollywood film "Interstellar," a group of scientists journey through a wormhole in space to explore planets with conditions conducive to supporting life on Earth. One of the challenges they face is time dilation: every hour spent gathering data on a particular planet equates to seven years passing on Earth. Einstein's general theory of relativity suggests that time dilation due to gravity is one-way, meaning an object in high gravity experiences time at a slower rate than one in low gravity. Conversely, Einstein's special theory of relativity discusses mutual time dilation between two moving objects, where the times of both objects seem to slow down in relation to each other. This recent study argues that instead of being mutual, time dilation caused by motion is unidirectional, affecting only the moving object. The research, titled "Implication of an Absolute Simultaneity Theory for Cosmology and Universe Acceleration," was released on 23rd December 2014 in the journal PLOS ONE.

Molecular geneticist Professor Edward Kipreos, whose lab focuses on cell cycle regulation, developed an interest in cosmology and the theory of special relativity some years back. Image credit: University of Georgia

A molecular geneticist studying cell cycle regulation, Professor Edward Kipreos developed an interest in cosmology and the theory of special relativity some years back. He explains this phenomenon using Global Positioning System satellites as an example.

Kipreos notes that since the satellites move in free-fall reference frames at high speeds relative to Earth, adjustments must be made for the time dilation effects of their velocity. Without these corrections, the GPS measurements from the satellites would be inaccurate by about two kilometers per day.

This straightforward instance, involving GPS satellites transmitting time signals back to Earth for distance measurement, is rooted in the principles of special relativity and the Lorentz Transformation—a mathematical framework that elucidates the relationship between space and time measurements made by two observers.

“Special relativity is supposed to be reciprocal, where both parties will experience the same time dilation, but all the examples that we have right now can be interpreted as directional time dilation,” Kipreos said. “If you look at the GPS satellites, the satellite time is slowing down, but according to the GPS satellites, our time is not slowing down — which would occur if it were reciprocal. Instead, our time is going faster relative to the satellites, and we know that because of constant communication with the satellites.”

An alternative theory, the Absolute Lorentz Transformation, explains directional time dilation. Kipreos discovered that this theory aligns with existing evidence when the "preferred reference frame" is tied to centers of gravitational mass. For Earth, this frame would be the "Earth-centered non-rotating inertial reference frame," currently used for GPS satellite time dilation calculations.

Kipreos highlighted that applying the Absolute Lorentz Transformation strictly to cosmological data carries significant implications for the universe and dark energy. As the universe expands, cosmological entities like galaxies move away faster due to Hubble expansion. The theory suggests that higher velocities lead to directional time dilation. Consequently, this theory implies that the present universe experiences time dilation compared to the past, where time moves faster.

Supernovae of equal intensity serve as "standard candles" for measuring cosmological distances based on brightness. However, observations in 1998 and 1999 revealed that distant supernovae appeared dimmer than expected, indicating recent acceleration in the universe's expansion.

Kipreos noted, "The universe's accelerated expansion is often attributed to dark energy, yet its nature and recent emergence remain unclear."

The projected effects of faster time in the past would result in a linear supernova plot at all distances, suggesting no acceleration in the universe's expansion. In this scenario, the presence of dark energy would be unnecessary.

Razor-sharp test images show Euclid’s instruments performing as expected

An early test image from Euclid’s visible light camera, VIS, displays the full field of view on the left, while a close-up view of one segment's four quadrants is shown on the right. The close-up view represents approximately one quarter of the width and height of the full Moon. Image: ESA

The Euclid space telescope from the European Space Agency, launched on 1 July via a SpaceX Falcon 9 rocket, has arrived at its operational position at Lagrange Point 2, a stable gravitational area 1.5 million kilometers (1 million miles) away from Earth.

Initial test images reveal that the spacecraft's VISual imager (VIS) and Near-infrared Imaging Spectrometer and Photometer (NISP) are functioning well, capturing clear, wide-angle views of numerous stars and galaxies. Though raw images display cosmic ray streaks, these artifacts will be eliminated during the processing of scientific images.

Giuseppe Racca, the project manager, expressed, “After over 11 years of Euclid's design and development, it is both thrilling and deeply emotional to witness these initial images. It's truly remarkable to see just a few galaxies here, captured with minimal system adjustments. Once fully calibrated, Euclid will survey billions of galaxies to construct the most extensive 3D map of the sky ever created.”

Euclid’s Near-Infrared Spectrometer and Photometer (NISP) is crafted to gauge the light emission from galaxies across various IR wavelengths. The left image displays NISP's complete field of view, while the right image provides a closer view. Image: ESA

Yannick Mellier, the head of the multi-agency Euclid research consortium, stated, “The remarkable initial images captured by Euclid's visible and near-infrared instruments herald a new era in observational cosmology and statistical astronomy. They signify the commencement of the exploration into the true essence of dark energy, a pursuit led by the Euclid Consortium.”

The $1.5 billion Euclid project represents a pioneering effort to elucidate the characteristics of dark matter, the enigmatic substance permeating the universe, and dark energy, the inexplicable repulsive force propelling the universe's expansion.

Through the analysis of subtle luminosity variations in galaxies spanning the last 10 billion years, Euclid's cameras will aid researchers in determining whether dark energy aligns with a static "cosmological constant" as foreseen by Einstein's theory of general relativity, or if the current understanding of gravity necessitates revision.

Euclid will also delve into the nature of dark matter by scrutinizing the configurations of approximately 1.5 billion galaxies to ascertain how they have been distorted by concealed clouds of dark matter scattered across the expanse between Euclid and its targets.

ESA Director General Josef Aschbacher remarked, “It is truly impressive to witness the rapid success of the latest addition to ESA's scientific missions. I am fully confident that the mission's team will utilize Euclid effectively to unveil substantial insights about the 95 percent of the Universe that remains largely unknown to us.”

New comet predicted to brighten rapidly as it sprints Sunwards

 

Comet C/2023 P1 (Nishimura) imaged on 15 August from June Lake, California, USA, using a Celestron C14 HyperStar and a ZWO ASI2600MC pro camera to shoot and stack twenty 15-second exposures. Image: Dan Bartlett.

It’s time to hold onto your observing hats once more as a new comet, C/2023 P1 (Nishimura), discovered on 11 August, promises a significant brightening as it hurtles towards the Sun. However, in typical cometary fashion, its behavior is difficult to predict on its first and only visit to the Sun’s harsh environs. There’s a possibility it may disintegrate and fade away.

Currently, Comet C/2023 P1 (Nishimura) can be found in the pre-dawn sky moving northeastward among the stars of Gemini. Observing reports are limited in the initial week or so, but it is shining at approximately magnitude +9.5. Upon discovery, it was reported with a coma of 5 arcminutes in angular size and a tail eight arcminutes long. Nishimura will be closest to Earth, at a distance of around 127.1 million kilometers (0.85 AU), on 13 September, and will reach perihelion on 18 September, when it will be 32.9 million kilometers (0.22 AU) from the Sun.

Comet C/2023 P1 (Nishimura) lies low in the pre-dawn sky as it tracks through Gemini, Cancer and Leo on its way to perihelion on 18 September. All AN graphics by Greg Smye-Rumsby.

When to observe the comet

The comet remains visible in the pre-dawn sky until 13 September. A small telescope should easily spot it, provided your observing site has a good horizon to the east-southeast and is not heavily affected by light pollution. The Moon will not interfere until early September.

On 20 August at 4.25am, approximately 90 minutes before sunrise and at the start of nautical twilight from London (with the Sun 12° below the horizon), Comet C/2023 P1 (Nishimura) is positioned about 13° above, around 3° southeast of the magnitude +3.5 star Wasat (delta Geminorum). The comet should be more visible on the pre-dawn of 26 August, aligning nicely with Gemini’s bright stars Castor and Pollux, situated 6.7° below Pollux, the southern twin. It is now a bit higher in the sky, around 4° higher, with the Minor Planet Center anticipating a one-magnitude brightening.

By the end of August, Comet C/2023 P1 (Nishimura) is in Cancer, maintaining its altitude and positioned approximately 4° north-northwest of the Beehive cluster (Messier 44), the prominent open cluster. If it continues to brighten as predicted, the comet will shine at about magnitude +7.5.

Comet C/2023 P1 (Nishimura) lines up with Castor and Pollux in the pre-dawn sky of 26 August.

Into September: losing altitude but brightening faster

In early September, Comet C/2023 P1 (Nishimura) begins to descend in altitude as it approaches the Sun, but compensates with an accelerated rate of brightening. It should still be observable through binoculars at this point.

On the morning of 7 September, the comet can be seen in Leo, passing north of magnitude +3 epsilon Leonis while positioned around 13° high in London at 5.05am. A few mornings later, Comet C/2023 P1 (Nishimura) drops below 10° altitude as it starts moving southward, now traversing the sky more than four times faster than during its discovery.

Into the early evening sky

Following its closest approach to Earth on 13 September, Comet C/2023 P1 (Nishimura) transitions to the early-evening sky, with an elongation from the Sun ranging between 12 to 15 degrees. There's a slight opportunity to catch a glimpse of it in strong twilight approximately 40 minutes after sunset from the 13th to the 18th, positioned just about 6° high in the west-northwest. Some estimates place Comet C/2023 P1 (Nishimura) at magnitude +2.8 during this time; even if accurate, it will be challenging to observe.

If it survives its perihelion passage, Comet C/2023 P1 (Nishimura) continues its southward descent for the remainder of the year. Observers in the Southern Hemisphere can witness it under twilit conditions. From Sydney, Australia, the comet appears low in the pre-dawn northeastern sky until around 25 August. After that, it becomes unobservable until late October, when it is low in the pre-dawn sky amidst the stars of Hydra, not far from the globular cluster M68. However, at this point, it shines fainter than magnitude +10.

Comet C/2023 P1 (Nishimura) moves into the early evening sky starting on 13 June. It will be quite challenging to observe from UK skies, appearing low in the strong twilight, even though it may brighten to around magnitude +2 at perihelion. This scenario depicts the western-northwestern view from the south of England at 7.50pm BST, approximately 30 minutes after sunset.