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One way to explain why time only moves forward is the quantum arrow of time, and it has major implications for both the universe's early period and its eventual demise

One way to explain why time only moves forward is the quantum arrow of time, and it has major implications for both the universe's early period and its eventual demise

High school students in Russellville, Alabama win the American Rocketry Challenge after months of designing and building a victorious rocket.

A new official clip has just been released by Disney+ for "Star Wars: The Acolyte" showing off the martial arts fight choreography featured in the upcoming miniseries.

"Adoption of this alloy will lead to more sustainable aviation and space exploration."

SpaceX is set to launch yet another batch of its Starlink internet satellites from Florida on Tuesday morning (May 28).

Smoke from wildfires burning in Canada and Mexico is already worsening air quality in the US, but some signs suggest clearer skies than last year

Smoke from wildfires burning in Canada and Mexico is already worsening air quality in the US, but some signs suggest clearer skies than last year

Can a gas cloud eat a galaxy?

With La Nina conditions evolving in the Pacific and near-record warm waters in the Atlantic, scientists expect the 2024 hurricane season to be a busy one.

Experiments with optical illusions have revealed surprising similarities between human and AI perception

An innovative telescope design has proven successful for daytime skywatching, opening new doors for uninterrupted observation of the cosmos.

How can sunlight reflecting off SpaceX’s Starlink satellites interfere with ground-based operations? This is what a recently submitted study hopes to address as a pair of researchers investigate how Starlink satellites appear brighter—which the researchers also refer to as flaring—to observers on Earth when the Sun is at certain angles, along with discussing past incidents of how this brightness has influenced aerial operations on Earth, as well. This study holds the potential to help spacecraft manufacturers design and develop specific methods to prevent increased brightness levels, which would help alleviate confusion for observers on Earth regarding the source of the brightness and the objects in question.

Here, Universe Today discusses this research with Anthony Mallama of the IAU – Centre for the Protection of Dark and Quiet Skies from Satellite Constellation Interference regarding the motivation behind the study, significant results, potential follow-up studies, importance of studying Starlink satellite brightness, and implications for managing satellite constellations in the future. So, what was the motivation behind this study?

“I study the brightness of Starlink satellites under all circumstances,” Mallama tells Universe Today. “That includes their operational phase at 550 km [342 mi] altitude, when they are rising from the initial orbit around 300 km [186 mi] to operation height, ordinary flares which occur frequently but have small amplitudes and these extreme flares.”

For the study, the researchers conducted a geometrical analysis of the brightness of Starlink satellites based on the Sun’s location and angle in the sky. This comes despite SpaceX taking steps to mitigate reflectivity off Starlink satellites, which only decreases reflectivity when the satellites are directly overhead. The study also discussed how reflectivity from Starlink satellites has affected aerial operations, specifically with commercial airline pilots. Therefore, what were the most significant results from this study?

Mallama tells Universe Today, “This study demonstrated that Starlinks can be exceedingly bright under certain conditions. In one instance they were reported as Unidentified Aerial Phenomenon (UAP) by pilots on two commercial aircraft.”

Regarding potential follow-up studies, Mallama tells Universe Today, “I am characterizing the brightness of other satellite constellations including Amazon’s Kuiper, AST SpaceMobile’s BlueWalker/BlueBirds and Planet’s Pelicans.”

The study mentions how the UAP incidents occurred in 2022 and was recently discussed in Buettner et al (2024) with the pilots’ reporting brightness magnitudes (also called stellar magnitude or apparent magnitude) of -4 to -5. For context, a stellar magnitude of -5 is equivalent to the planet Venus at its brightest, which is known for being observed before sunrise or after sunset periodically throughout the year. The apparent magnitude scale ranges from -30 to 30 with higher numbers corresponding to decreasing brightness.

Buettner et al (2024) was recently presented at the 4th IAA Conference on Space Situational Awareness (ICSSA). That paper discussed how the incident occurred on August 10, 2022, and was observed by five pilots aboard two separate commercial airline flights over the Pacific Ocean, which resulted in two photographs obtained by the pilot’s cell phones. After analyzing a series of simulations and additional data, the researchers determined these UAPs were Starlink satellites launched earlier that day, which was designated as Starlink Group 4-26. Given this incident, what is the importance of studying Starlink brightness/flaring?

Mallama tells Universe Today, “The importance of studying Starlink brightness is that the satellites interfere with astronomical research if they are brighter than magnitude 7. Furthermore, casual sky watchers, such as amateur astronomers and naturalists, are distracted by those brighter than magnitude 6 because they are visible to the unaided eye.”

This study comes as SpaceX’s Starlink constellation continues to grow on a regular basis, with the number of current Starlink satellites in orbit have reached more than 5,600 with almost 6,000 having been launched by SpaceX as of this writing. As noted by both the study and Mallama, sunlight reflectivity off Starlink satellites causes issues with both aerial operations on Earth and astronomical observing, with Mallama also conducting research on satellite constellation brightness for Amazon, AST SpaceMobile, and Planet Labs. Therefore, with the number of satellites in orbit rapidly increasing due to constellations, what implications could this study have on managing satellite constellations in the future?

Mallama tells Universe Today, “One approach to reducing satellite brightness is to reflect sunlight into space rather than allowing it to scatter diffusively toward observers on the ground. That works very well most of the time. However, there are certain Sun-satellite-observer geometries where it fails and observers see a mirror-like reflection of the Sun.” Mallam published a 2023 article with Sky & Telescope discussing how SpaceX’s second-generation of Starlink satellites are fainter than their predecessors.

This diagram and artist illustration demonstrates how sunlight reflects off a Starlink version 1.5 satellite, and was discussed in a 2023 article authored by Anthony Mallama and published in Sky & Telescope. (Credit: SpaceX)

Mallama credits his co-author, Richard Cole, as playing a “crucial role” in this study, noting how Cole “predicted the extreme flares based on his numerical model of Starlink satellite brightness.”

How will sunlight reflectivity off Starlink satellites influence ground operations in the coming years and decades, and what steps can be taken to mitigate this activity? Only time will tell, and this is why we science!

As always, keep doing science & keep looking up!

The post Starlinks Can Produce Surprisingly Bright Flares to Pilots appeared first on Universe Today.

It’s been a momentous May for skywatchers around the world. First the big auroral event of May 10-11, next a flaming space rock entering over Spain and Portugal. The inbound object was captured by ground-based cameras and the MeteoSat Third Generation Imager in geostationary orbit.

The incoming meteor dazzled viewers across both countries as it sped across the skies at 160,000 km/hour. Of course, social media came alive with speculation about what was burning up in the atmosphere. Most people thought it was a piece of space rock from an asteroid. European Space Agency members of the Planetary Defence Office immediately began analyzing images and data to figure out the composition of the impactor. Now it seems more likely the chunk of space debris came from a comet. They used other data about the energy released as the fragment flew through the atmosphere to determine the size of the object. It was likely about 1 meter across with a mass of between 500 to 1,000 kg.

On 18 May, the meteor burned up in the night sky over Spain and Portugal – as seen by the fireball camera in Cáceres, Spain, operated by ESA’s Planetary Defence Office

This is pretty small, which makes it hard to spot on the way in. Also, the object approached from the direction of the sky crowded with stars, making it doubly difficult to see as it spun into our planet’s atmosphere. It explains why planetary defense telescopes or observers didn’t detect the meteor.

The Meteor’s Appearance

To most observers, the meteor over Portugal and Spain looked blue-green and very bright. Those colors are created as various elements in the meteor get heated up by friction with our atmosphere. That vaporizes them and we see the “fiery” aspect light up the sky. If it was a piece of a comet, then the colors also indicate the materials it contained. Most comets contain water, carbon dioxide, ammonia, and methane ice. Other comet “stuff” consists of silica dust, carbon, various metals, and organic molecules. The metals, in particular, could show spectacular colors as they heat up and vaporize.

It’s not known which comet supplied the chunk that broke up and vaporized that night. Earth’s orbit crosses the orbit of several different comets. As they travel through space, particularly as they get close to the Sun, comets shed pieces of themselves. That cometary debris stays in the original orbit around the Sun. Occasionally, Earth’s orbit intersects that cometary path. Its particles particles eventually end up in our atmosphere. The best-known path creates the Orionid Meteor Shower and we can thank Comet Halley for that show from late September to mid-November.

Surveys to Detect an Incoming Space Rock

As planetary scientists learn more about the near-Earth environment and its population of asteroids and other space debris, they’ve formed observation groups within NASA and ESA. There’s a network of ground-based observers and facilities that watch the sky each night, looking for incoming impactors. Most of the time, their search is limited to objects larger than the Portugal/Spain object. In addition, satellites such as MeteoSat can pick up these intruders. MeteoSat was launched by ESA to monitor weather conditions and detect lightning strikes. The instrument has four cameras covering Europe, Africa, the Middle East, and parts of South America. Each can capture up to a thousand images per second, allowing the satellite to monitor lightning continuously from space.

ESA’s Planetary Defence Office is in charge of monitoring the positions and approaches of near-Earth objects that could pose a threat to any portion of our planet. It does regular observing campaigns to search for bits of asteroids and comets. NASA operates the Center for Near Earth Object Studies (CNEOS) to do similar searches for possibly dangerous rocks. The Near-Earth objects it’s most concerned about are asteroids and comets with orbits that bring them to within 195 million kilometers of the Sun. Their orbits can move through our planet’s neighborhood. Most of these small bodies are asteroids as small as a few meters wide to nearly 40 kilometers across.

Artist’s concept of the path that a space rock can take that might bring it near Earth. Planetary defense facilities around the planet try to track these objects and warn of their close approach whenever possible. Courtesy: ESA – P.Carril.

The office uses data from observatories around the world—both professional and amateur. Much of this data comes from larger facilities, including Pan-STARRS, the Catalina Sky Survey, and NASA’s NEOWISE mission. In addition, there’s a significant program of planetary radar measurements that contribute data to the NEO observations effort. All of these skywatching campaigns contribute to increased awareness and predictions of near-Earth objects that could pose a threat to our planet.

For More Information

Fireball Witnessed by Weather Satellite

Asteroid Watch

ESA Planetary Defence Office

The post A Weather Satellite Watched a Space Rock Burn Up Above Spain and Portugal appeared first on Universe Today.

One of the main objectives of the James Webb Space Telescope (JWST) is to study the early Universe by using its powerful infrared optics to spot the first galaxies while they were still forming. Using Webb data, a team led by the Cosmic Dawn Center in Denmark pinpointed three galaxies that appear to have been actively forming just 400 to 600 million years after the Big Bang. This places them within the Era of Reionization, when the Universe was permeated by opaque clouds of neutral hydrogen that were slowly heated and ionized by the first stars and galaxies.

This process caused the Universe to become transparent roughly 1 billion years after the Big Bang and (therefore) visible to astronomers today. When the team consulted the data obtained by Webb, they observed that these galaxies were surrounded by an unusual amount of dense gas composed almost entirely of hydrogen and helium, which likely became fuel for further galactic growth. These findings already reveal valuable information about the formation of early galaxies and show how Webb is exceeding its mission objectives.

The research was led by Kasper E. Heintz, a NASA Hubble Fellow and an assistant professor of astrophysics, and his colleagues at the Cosmic Dawn Center (DAWN) at the Niels Bohr Institute. They were joined by researchers from ETH Zurich, the MIT Kavli Institute for Astrophysics and Space Research, the Space Telescope Science Institute (STScI), the Association of Universities for Research in Astronomy (AURA), the European Space Agency (ESA), the NSF’s National Optical-Infrared Astronomy Research Laboratory (NOIRLab), and multiple universities.

Illustration showing the process of Cosmic Reionization, divided into four periods. Credit: NASA

According to models of galaxy formation, the first galaxies are believed to have resulted from the infall of neutral, pristine gas onto the first protogalactic halos. However, the abundance of neutral atomic hydrogen in galaxies has remained unknown due to the difficulty of observing the earliest cosmological periods. “These galaxies are like sparkling islands in a sea of otherwise neutral, opaque gas,” Heintz explained in a NASA press release. “Without Webb, we would not be able to observe these very early galaxies, let alone learn so much about their formation.”

Since the galaxies appeared as little more than red blobs in the Webb images, the team also relied on data obtained by Webb‘s Near Infrared Camera (NIRCam) through the Cosmic Evolution Early Release Science (CEERS) Survey and shared through the Early Release Science (ERS) program. The spectra revealed that light from these galaxies is absorbed by large amounts of neutral hydrogen gas. They then matched the Webb data to models of star formation, which revealed that these galaxies are primarily populated by young stars. Said co-author Darach Watson, a professor at DAWN:

“The gas must be very widespread and cover a very large fraction of the galaxy. This suggests that we are seeing the assembly of neutral hydrogen gas into galaxies. That gas will go on to cool, clump, and form new stars. The fact that we are seeing large gas reservoirs also suggests that the galaxies have not had enough time to form most of their stars yet.”

“We’re moving away from a picture of galaxies as isolated ecosystems,” added Simone Nielsen, a co-author and PhD student at DAWN. “At this stage in the history of the universe, galaxies are all intimately connected to the intergalactic medium with its filaments and structures of pristine gas.”

The timeline from the Big Bang on the right towards the present on the left. In the middle is the Reionization Period where the initial bubbles caused the Cosmic Dawn. Credit: NASA SVS

These results illustrate what is now possible for astronomers, thanks to next-generation telescopes like Webb. Of course, many unanswered questions remain, not the least of which has to do with the distribution of the cold gas in these early galaxies. For instance, how much is located near the center of galaxies versus their outskirts? Also, astronomers are still unsure if this gas is pristine or already populated by heavier elements. As Heintz indicated, “The next step is to build large statistical samples of galaxies and quantify the prevalence and prominence of their features in detail.”

Further Reading: NASA, Science

The post Galaxies in the Early Universe Preferred their Food Cold appeared first on Universe Today.

A set of Australian fossils offers a rare glimpse of the ancient relatives of platypuses and echidnas that lived alongside the dinosaurs 100 million years ago

A set of Australian fossils offers a rare glimpse of the ancient relatives of platypuses and echidnas that lived alongside the dinosaurs 100 million years ago

An exclusive interview with director Brad Peyton on Netflix's new sci-fi film "Atlas."

Here's what it was like to experience the Starmus Festival in Bratislava, where top scientists and musicians united to celebrate Earth with an overarching theme "The future of our home planet".

Sometimes, astronomers get lucky and catch an event they can watch to see how the properties of some of the most massive objects in the universe evolve. That happened in February 2020, when a team of international astronomers led by Dheeraj (DJ) Pasham at MIT found one particular kind of exciting event that helped them track the speed at which a supermassive black hole was spinning for the first time.

Dr. Pasham found AT2020ocn, a bright flash captured by the Zwicky Transient Facility at Palomar Observatory. He thought it might signify a tidal disruption event (TDE). In these extreme events, a black hole rips apart a star. Part of the star’s remnants are flung from the black hole, but part falls into the accretion disk. And how they fall could hold the key to understanding how a black hole is spinning.

How that disk accretes is attributable to a cosmological theory called Lense-Thirring precession, which shows how space-time is warped by powerful gravitational fields—like those around black holes. Lense-Thirring theory predicts that an accretion disk formed after a TDE would “wobble” soon after the event before settling down into a more standard pattern of matter orbiting a black hole. The key would be to catch a TDE event very early after it happened and then watch the resulting “wobbling” over as long of a time span as possible.

Fraser discusses measuring the spin of a black hole.

So catching AT2020ocn was just the first step—then the authors had to monitor it—preferably for months. To do so, they recruited the Neutron Star Interior Composition ExploreR (NICER), an X-ray telescope attached to the ISS. NICER watched the galaxy containing AT2020ocn for 200 days immediately following the bright flash caught by Zwicky. 

They began to notice a pattern. Every 15 days, the amount of X-rays emitted around the black hole peaked sharply, indicating the potential “wobble” they were looking for. Plugging that frequency into equations for the Lense-Thirring theory, along with estimates of the star’s mass and the black hole’s mass, they determined the black hole was spinning at 25% of the speed of light—which is actually relatively slow for a black hole.

A black hole’s rotational speed can increase or decrease depending on its local environment. As it absorbs more material, typically in the form of matter from its accretion disk falling into it, its rotational speed increases. On the other hand, if it collides with another black hole, the overall rotational speed could decrease, as the two black holes’ spins could be opposite. That appears to be what has happened with the black hole that caused the AT2020ocn TDE, given its relatively slow speed compared to other black holes.

Black holes typically spin exceptionally fast, as Fraser discusses in this video.

The findings of this work were recently published in a paper in Nature. They also potentially lay the groundwork for calculating the spin of other supermassive black holes in the galaxy. Dr Pasham believes astronomers could calculate the spins of hundreds of black holes, opening up insights into their formation and life cycle.

But to do that, they will still need a lot of luck. TDEs are relatively rare events, and even when they do happen, there are obvious resource constraints on telescope time. The Vera Rubin Observatory might help, as it will monitor large chunks of the sky, but it’s not scheduled to come online until mid-next year. Until then, those interested in tracking black hole spins might have to rely on serendipity to find a rare event and have the telescope time to monitor it.

Learn More:
MIT – Using wobbling stellar material, astronomers measure the spin of a supermassive black hole for the first time
Pasham et al. – Lense–Thirring precession after a supermassive black hole disrupts a star
UT – Black Holes are Firing Beams of Particles, Changing Targets Over Time
UT – The Milky Way’s Black Hole is Spinning as Fast as it Can

Lead Image:
Artist’s depiction of how the accretion disk around a black hole could wobble in frequency with its spin, and how that wobble might be captured by a sensor near Earth.
Credits: Michal Zajacek & Dheeraj Pasham

The post A New Way to Measure the Rotation of Black Holes appeared first on Universe Today.