Astronomy

Observations made by the Magellan spacecraft in the 1990s include signs of recent lava flows, highlighting possible exploration targets for probes heading to Venus in the 2030s

A new theory of quantum gravity, which attempts to unite quantum physics with Einstein's relativity, could help solve the puzzle of the universe's expansion, a theoretical paper suggests.

The evidence is in: Venus is volcanically active.

The post Venus’s Volcanoes Live appeared first on Sky & Telescope.

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.

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.