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In the early hours of July 2, 2025, astronomers around the world were startled by an astonishing signal: a burst of extremely energetic gamma-rays originating from a distant galaxy approximately 8 billion light-years away in the constellation Scutum. This event, designated GRB 250702B, is not just another gamma-ray burst (GRB) — it turned out to be the longest and most unusual gamma-ray explosion ever observed, challenging decades of understanding about how these cosmic events work. Rather than fading within seconds or minutes like typical GRBs, GRB 250702B continued to flash in gamma-rays and X-rays for hours, possibly extending nearly a full day in total activity, punctuated by multiple bursts separated by regular intervals — behavior never before seen in the cosmic fireworks of the universe.

Gamma-ray bursts themselves are among the most powerful explosions known. They release more energy in a blink of an eye than the Sun will emit over its entire 10-billion-year lifetime. Astronomers classify GRBs into two broad categories: short bursts lasting less than about two seconds, typically associated with the merger of compact objects like neutron stars or black holes; and long bursts, usually tied to the catastrophic collapse of a massive star’s core into a black hole or neutron star at the end of its life. In both cases, collapsing matter drives ultrarelativistic jets — beams of particles moving at nearly the speed of light — that produce gamma rays when they interact with surrounding material. These jets, narrowly focused and extremely bright, can be detected across vast cosmic distances, briefly outshining entire galaxies.

What set GRB 250702B apart was not only its **extraordinary duration — around seven hours in gamma-rays with associated X-ray activity detected even earlier — but also the fact that the burst appeared to repeat multiple times over that period. Traditional GRB models involve a one-time, catastrophic event that destroys the progenitor star, meaning the central engine powering the burst should cease after a singular explosion. In contrast, GRB 250702B produced distinct pulses spaced quasi-periodically over hours, an anomaly that pushed researchers to consider more exotic origins. Telescopes including NASA’s Fermi Gamma-ray Space Telescope and the Chinese Einstein Probe first recorded the unusual emission, later confirmed by follow-up observations from space and ground-based facilities that tracked the afterglow across the electromagnetic spectrum.

One of the leading interpretations emerging from this unprecedented data is that GRB 250702B may not fit neatly into the classic “collapsar” model for long GRBs — the collapse of a single massive star. Instead, astronomers have explored scenarios involving tidal interactions between a black hole and a companion star. In one compelling model consistent with both the timing and periodicity of the pulses, a stellar-mass black hole — perhaps just a few times the mass of the Sun — was in a tight orbit with a companion star. Over time, this black hole spiraled into the star’s outer layers and then its dense core, slowly shredding and consuming the stellar material from within. As it tore through the star, enormous amounts of gas would have accreted onto the black hole, fueling sustained jets of gamma-ray-emitting plasma over many hours, rather than the brief flash typical of ordinary GRBs. While this “black hole eating a star from within” picture remains theoretical, it provides a framework for the extended engine activity and repeating pulses seen in GRB 250702B, and could represent a new class of gamma-ray transient.

Alternative explanations have also been proposed. Some researchers have suggested that the long emission could be produced by a tidal disruption event (TDE), where a black hole — potentially larger than a stellar-mass black hole — comes close enough to a star to rip it apart through extreme gravitational forces. The debris from the disrupted star could feed the black hole over extended periods, powering a prolonged gamma-ray and X-ray signal. Others have proposed models involving magnetic jets with precession — a wobbling motion caused by misalignment between the black hole’s spin and the accretion disk — that could produce repeated pulses spaced at regular intervals as the jet sweeps across our line of sight. New work from theoretical astrophysicists suggests that the structure and timing of the emissions from GRB 250702B can be explained by such a precessing magnetic jet engine, offering a coherent explanation for the “heartbeat-like” nature of the burst.

Beyond the theoretical intrigue, GRB 250702B is significant because it highlights how cosmic explosions can transcend familiar categories, revealing physics and astrophysical environments more complex than previously understood. This event not only broke records for duration, but also offered the first case where a gamma-ray source exhibited multiple, spaced bursts over hours, suggesting a central engine that remained active far longer than classic models predict. Continued analysis of the afterglow — the fading light across X-ray, optical, and radio wavelengths — and characterization of the host galaxy will help astronomers distinguish between rival models and refine our understanding of these powerful cosmic beacons. With each new observation, events like GRB 250702B deepen our grasp of how matter and energy behave under the most extreme conditions and remind us that the universe still holds phenomena that challenge existing theories.

Video credit: NASA/LSU/Brian Monroe, Animator: Brian Monroe, Producer: Scott Wiessinger (eMITS), Science Writer: Francis Reddy (University of Maryland College Park), Scientist: Eric Burns (LSU)

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The Moon’s phases are among the most familiar and enduring rhythms in the natural world, quietly unfolding overhead as the Moon appears to change shape night after night. Although these changes may seem mysterious at first glance, they are the result of straightforward celestial geometry governed by the motions of the Earth, Moon, and Sun. Understanding the phases of the Moon not only reveals fundamental principles of physics and astronomy, but also explains why this cycle has played such a significant role in human culture, natural ecosystems, and life on Earth for thousands of years.

At its core, a lunar phase describes how much of the Moon’s sunlit surface is visible from Earth at a given time. The Moon does not produce its own light; it reflects sunlight. As the Moon orbits Earth roughly once every 27.3 days, the angle between the Sun, Earth, and Moon continuously changes. This changing geometry determines which portion of the Moon’s illuminated hemisphere faces our planet. When the Moon lies between Earth and the Sun, its illuminated side is turned away from us, producing a new moon. As the Moon moves along its orbit, more of its sunlit surface becomes visible, leading to the waxing crescent, first quarter, waxing gibbous, and eventually the full moon, when Earth sits between the Moon and the Sun and the entire near side of the Moon is illuminated. The cycle then reverses through waning gibbous, last quarter, and waning crescent, completing a full sequence known as the synodic month, which lasts about 29.5 days.

The physics behind the Moon’s phases is a clear demonstration of orbital mechanics and light reflection. The Moon’s orbit is slightly tilted relative to Earth’s orbit around the Sun, which is why we do not experience eclipses every month. Instead, the phase cycle proceeds smoothly as a function of orbital position rather than alignment. Importantly, the phases are not caused by Earth’s shadow falling on the Moon, a common misconception. Earth’s shadow only plays a role during a lunar eclipse, a relatively rare event. The regular waxing and waning we observe is simply a matter of perspective: we are watching different fractions of the Moon’s illuminated half come into view as it travels through space. This predictable pattern has allowed astronomers to model lunar motion with great precision and has historically served as one of humanity’s earliest tools for tracking time.

Beyond their physical explanation, lunar phases have long held practical and symbolic significance. Before mechanical clocks and modern calendars, many civilizations relied on the Moon as a natural timekeeper. Lunar calendars guided agricultural cycles, religious observances, and social organization across cultures ranging from ancient Mesopotamia and China to Indigenous societies around the world. The regularity of the lunar cycle made it a reliable framework for structuring human activity long before scientific explanations were available.

The Moon’s influence on Earth extends beyond cultural symbolism into the realm of physical interaction, most notably through tides. While the phases themselves do not cause tides, they are closely linked to tidal strength. During new and full moons, the Sun, Earth, and Moon align in a configuration producing stronger spring tides due to the combined gravitational pull of the Moon and Sun. During first and last quarter phases, when the gravitational forces act at right angles, tidal ranges are reduced, creating neap tides. These tidal cycles play a critical role in shaping coastlines, mixing ocean waters, and supporting marine ecosystems that depend on predictable changes in sea level for feeding, breeding, and migration.

Life on Earth has also adapted to the Moon’s changing illumination. Many species exhibit behaviors synchronized with lunar phases, a phenomenon known as lunar rhythm. Corals, for example, time mass spawning events to specific phases of the Moon, ensuring reproductive success across vast reef systems. Nocturnal animals adjust hunting, foraging, and movement patterns based on moonlight levels, while some predators and prey alter their behavior to exploit or avoid increased visibility during brighter nights. Even humans, though largely insulated from natural light cycles by modern technology, continue to mark lunar events, reflecting a deep-seated psychological and cultural connection to the Moon’s steady cadence.

In a broader sense, the Moon’s phases remind us of Earth’s place in a dynamic cosmic system. They illustrate how motion, gravity, and light interact on a planetary scale, turning abstract physical laws into visible, recurring phenomena. The same principles that govern the Moon’s changing face also shape the behavior of planets, moons, and stars throughout the universe. By observing the Moon’s phases, we are witnessing orbital mechanics in action, played out on a scale that is both accessible and profound.

Ultimately, the phases of the Moon are more than a visual curiosity. They are a bridge between physics and lived experience, linking celestial motion to tides, ecosystems, calendars, and human history. Night after night, as the Moon waxes and wanes, it offers a quiet demonstration of the forces that govern our solar system and a reminder that life on Earth is deeply connected to the rhythms of the cosmos.

Video credit: NASA’s Goddard Space Flight Center, Data visualization by: Ernie Wright (USRA), Planetary scientist: Noah Petro (NASA/GSFC), Producer & Editor: James Tralie

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SS 433 is one of the most extraordinary and enigmatic objects in the Milky Way, a system whose extreme physics has made it a cornerstone of high-energy astrophysics for more than four decades. Located about 5,500 light-years away in the direction of the constellation Aquila, SS 433 is the first known microquasar—a stellar binary with powerful relativistic jets resembling those of supermassive black holes, but scaled to the mass of a single star. At the heart of the system is a compact object whose nature continues to generate debate: although a neutron star cannot be definitively ruled out, mounting evidence points toward SS 433 harboring a stellar-mass black hole, one that is actively feeding on material from its companion star and launching jets at speeds approaching one-quarter the speed of light. The extreme conditions in this system make SS 433 a natural laboratory for studying accretion physics, jet formation, and the limits of matter under relativistic stresses.

One of the defining features of SS 433 is its precessing jet system, a dynamic structure that distinguishes it from nearly all other known X-ray binaries. As the compact object accretes material from its massive donor star—likely an A-type supergiant—the inflowing gas forms a dense, hot accretion disk. From the inner regions of this disk, two opposing jets are launched at roughly 0.26c, a velocity that directly reveals the presence of an intense gravitational well. The jets do not simply stream outward in a straight line; instead, the axis of the disk—and therefore the jets—precesses like a spinning top, tracing a conical pattern every 162 days. As the jets sweep across the sky, their emission undergoes extreme Doppler shifting, which astronomers detect as visibly changing redshifts and blueshifts in the spectral lines of hydrogen and heavier elements. This unique behavior is what enabled SS 433 to become the first system in which relativistic jet speeds were measured outside of an active galactic nucleus.

The environment surrounding SS 433 adds yet another layer of complexity. The system lies at the center of the radio nebula W50, a distorted supernova remnant whose elongated, “manatee-shaped” structure appears to have been sculpted over tens of thousands of years by the persistent, high-energy jets emerging from SS 433. The interaction between these jets and the expanding supernova remnant creates shock waves, particle acceleration sites, and X-ray bright knots that provide insight into how jets deposit energy into their surroundings. Observations from XMM-Newton, Chandra, and radio observatories have revealed that the jets remain collimated over astonishing distances—on the order of dozens of light-years—before finally dispersing into the ambient medium. This durability indicates a stable launching mechanism and considerable energy output, both of which bolster the argument for a black hole rather than a neutron star as the jet-driving engine.

The debate over the compact object’s identity centers on mass estimates derived from orbital dynamics, emission modeling, and binary evolution theory. Early measurements suggested a mass around 10 M☉, comfortably within black hole territory, though later studies have proposed somewhat lower values consistent with heavy neutron stars. Yet the prevailing interpretation emphasizes the system’s extraordinary luminosity, steady high-rate accretion, and jet power—properties more naturally explained by a black hole feeding at or above its Eddington limit. SS 433 is one of the very few objects in the Galaxy that appears to host a supercritical accretion disk, a configuration in which the infalling matter produces thick disk winds and intense radiation pressure, conditions difficult for neutron stars to sustain. Simulations indicate that such a disk geometry can produce the observed precession and collimated outflows, providing a cohesive theoretical framework that aligns with decades of observation.

In the broader astrophysical context, SS 433 continues to serve as a bridge between stellar-mass black holes in our galaxy and the majestic quasars found in distant galaxies. Although microscopic by comparison, its disk–jet dynamics follow the same physical rules that govern the supermassive black holes in active galactic nuclei. Because SS 433 is nearby, bright, and persistently active, it offers a uniquely accessible view of the relativistic processes that shape cosmic evolution on every scale. As modern observatories—from high-resolution X-ray satellites to sensitive radio telescopes—continue to study the system, SS 433 provides ongoing opportunities to refine our understanding of how black holes feed, how jets form, and how extreme gravitational environments sculpt the universe around them. In many respects, SS 433 remains not just an astrophysical curiosity but a cornerstone for testing the laws of physics under conditions that cannot be reproduced anywhere on Earth.

Video credit: X-ray: (IXPE): NASA/MSFC/IXPE; (Chandra): NASA/CXC/SAO; (XMM): ESA/XMM-Newton; IR: NASA/JPL/Caltech/WISE; Radio: NRAO/AUI/NSF/VLA/B. Saxton. (IR/Radio image created with data from M. Goss, et al.); Image Processing/compositing: NASA/CXC/SAO/N. Wolk & K. Arcand; Sonification: NASA/CXC/SAO/K.Arcand, SYSTEM Sounds (M. Russo, A. Santaguida)

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The Neutron Star Interior Composition Explorer (NICER) is a NASA mission launched in June 2017 and mounted on the International Space Station (ISS). Its primary objective is to study neutron stars—ultra-dense remnants of massive stars that have undergone supernova explosions. By observing X-ray emissions from these celestial objects, NICER aims to provide insights into their internal structures and the fundamental physics governing matter under extreme conditions.

NICER’s core component is the X-ray Timing Instrument (XTI), designed for high-precision timing and spectroscopy of soft X-rays in the 0.2–12 keV energy range. The XTI comprises 56 co-aligned X-ray concentrator optics, each paired with a silicon drift detector. These concentrators utilize grazing-incidence optics with 24 nested mirrors to focus incoming X-rays onto their respective detectors, enhancing sensitivity and resolution.

NICER is mounted on the ISS’s ExPRESS Logistics Carrier-2. It features a two-axis pointing system that allows the instrument to track celestial targets across the sky. An integrated star tracker ensures precise alignment, enabling NICER to observe multiple targets during each 92-minute orbit of the ISS.

To achieve its scientific goals, NICER incorporates a GPS-based timing system capable of tagging photon arrival times with sub-microsecond accuracy. This high temporal resolution is crucial for studying the rapid rotational periods of pulsars and other time-sensitive phenomena.

NICER has significantly advanced our understanding of neutron star interiors by providing precise measurements of their masses and radii. These observations have helped constrain the equation of state for ultra-dense matter, shedding light on the behavior of matter at densities exceeding those found in atomic nuclei.

An extension of NICER’s mission, known as SEXTANT (Station Explorer for X-ray Timing and Navigation Technology), successfully demonstrated the use of X-ray pulsars for autonomous spacecraft navigation. By measuring the timing of X-ray pulses from known pulsars, SEXTANT was able to determine the ISS’s position in space, paving the way for future deep-space navigation systems.

In 2018, NICER discovered an X-ray pulsar in the fastest known stellar orbit, with a companion star completing an orbit every 38 minutes. This finding provides valuable data on the dynamics of compact binary systems and the extreme gravitational environments in which they exist.

NICER observed the brightest X-ray burst ever recorded from the neutron star SAX J1808.4−3658. This event offered insights into thermonuclear processes on neutron star surfaces and the mechanisms driving such energetic emissions.

Although primarily focused on neutron stars, NICER has also contributed to black hole research. It mapped “light echoes” from the stellar-mass black hole MAXI J1820+070, revealing changes in the size and shape of the surrounding accretion disk and corona. These observations enhance our understanding of black hole accretion processes and their immediate environments.

In May 2023, NICER’s thermal shields developed a leak, allowing stray light to interfere with its X-ray detectors. To address this issue, NASA designed specialized patches delivered to the ISS via the Cygnus NG-21 resupply mission in August 2024. Astronauts successfully applied these patches during a spacewalk on January 16, 2025, restoring NICER’s full observational capabilities.

As of early 2025, NICER has contributed to over 300 scientific publications, underscoring its significant role in advancing astrophysical research. Its high-precision measurements continue to provide valuable data for the scientific community, enhancing our understanding of neutron stars and other cosmic phenomena.

Video credit: NASA Goddard

Asteroid (52246) Donaldjohanson is a small but significant body located in the main asteroid belt between Mars and Jupiter. Though it may not have the fame of larger or more compositionally unique asteroids, Donaldjohanson stepped into the scientific spotlight thanks to its pivotal role in NASA’s ambitious Lucy mission — a 12-year journey to explore the Trojan asteroids that share Jupiter’s orbit. Before Lucy reaches its primary Trojan targets, it first encountered Donaldjohanson, making it a key object of study in humanity’s effort to understand the solar system’s early history.

Discovery

Asteroid Donaldjohanson was discovered on March 2, 1981, by astronomer Schelte “Bobby” Bus at the Siding Spring Observatory in Australia. Initially designated 1981 EQ5, the asteroid was later named in honor of Dr. Donald Johanson, the paleoanthropologist best known for co-discovering the fossilized remains of Australopithecus afarensis, famously known as Lucy, in Ethiopia in 1974.

This naming decision was particularly meaningful to NASA, as their Lucy spacecraft, launched in 2021, carries a similar goal: to uncover the fossils of the solar system—namely, the Trojan asteroids, which are thought to be leftover building blocks from planetary formation. Naming the asteroid after Johanson creates a poetic link between the exploration of human origins and the origins of our solar system.

Location and Characteristics

Donaldjohanson resides in the inner region of the main asteroid belt, at a semi-major axis of approximately 2.39 astronomical units (AU) from the Sun. Its orbit is relatively circular and stable, with a low eccentricity and inclination, placing it within the Erigone asteroid family, a large group of stony asteroids in the inner main belt.

Though smaller and less well-studied than some of its larger neighbors, Donaldjohanson’s value lies in its convenience and timing—it is perfectly positioned to serve as a flyby target for the Lucy spacecraft en route to the outer solar system.

The Lucy Mission Flyby

NASA’s Lucy spacecraft has successfully completed a flyby of asteroid Donaldjohanson, providing unprecedented insights into this intriguing celestial body. Lucy performed a close flyby at a distance of approximately 600 miles (960 kilometers), capturing detailed images and data.

The flyby is particularly exciting because very few main belt asteroids have been visited by spacecraft, and each one offers a new data point in understanding the diversity and history of these primitive bodies. By studying Donaldjohanson, Lucy will help bridge the scientific gap between the inner and outer asteroid populations.

During the flyby, Lucy used its three onboard science instruments — L’LORRI (a long-range imager), L’Ralph (a visible and infrared spectrometer), and L’TES (a thermal emission spectrometer) — to examine Donaldjohanson’s surface geology, composition, and thermal properties. In addition to gathering scientific data, the flyby allowed engineers to practice operating the spacecraft’s pointing, tracking, and data-gathering systems ahead of the more complex Trojan encounters.

The flyby revealed that Donaldjohanson is a contact binary asteroid, characterized by two lobes connected by a narrow neck, resembling a peanut or a barbell. This structure suggests a history of two separate bodies gently colliding and merging. The asteroid measures about 8 kilometers in length and 3.5 kilometers at its widest point, larger than previously estimated.

Donaldjohanson’s surface exhibits a complex geology with varying crater densities between its lobes, indicating a diverse collisional history. These observations provide valuable data on the processes that shaped such bodies and, by extension, the early solar system. The successful flyby serves as a critical rehearsal for Lucy’s upcoming encounters with Trojan asteroids near Jupiter, scheduled between 2027 and 2033.

Looking Ahead

While Donaldjohanson is not the primary target of Lucy’s mission, the asteroid plays an essential role in validating the mission’s capabilities and providing early science returns. Its proximity and well-known orbit make it an ideal testbed. Moreover, the data collected during the flyby will contribute to our broader understanding of asteroid families, space weathering, and solar system evolution.

After the 2025 encounter, Lucy will go on to visit eight Trojan asteroids, including Eurybates, Polymele, Leucus, Orus, and the binary pair Patroclus and Menoetius. These objects are expected to reveal new insights into the formation of the gas giants and the migration of planets during the early stages of solar system development.

In this grand journey, asteroid Donaldjohanson acts as the first stepping stone—a humble but crucial waypoint on the path to uncovering our solar system’s ancient past. As such, it not only honors the legacy of scientific discovery associated with its namesake but also propels forward the exploration of space’s most enduring mysteries.

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The night sky on Mars shares some familiar features with what we see from Earth, but also presents a few dramatic differences. Since Mars is farther from the Sun than Earth, its sky becomes darker more quickly after sunset, revealing a clearer and more brilliant canopy of stars. With a thinner atmosphere and less light pollution, the stars on Mars appear sharp and more numerous to the naked eye. The Milky Way stretches across the sky much like it does on Earth, but with a bit more clarity due to the reduced atmospheric scattering.

One of the most striking differences in the Martian night sky is the presence of its two small moons, Phobos and Deimos. These irregularly shaped satellites are far smaller than Earth’s Moon, so they don’t dominate the sky in the same way. Phobos, the closer and faster-moving moon, rises in the west and sets in the east in just over 4 hours, appearing several times in a single Martian night. It looks like a bright star or a small disk moving rapidly across the sky. Deimos is smaller and more distant, moving slowly and appearing like a faint star that drifts lazily overhead.

Because of Mars’ distance from Earth, familiar constellations still appear in similar patterns, though slightly shifted. From the Martian perspective, Earth is just a bright bluish “star” in the sky, never appearing larger than a dot without a telescope. Depending on the season and viewing direction, other planets like Jupiter, Saturn, and Venus are also visible, and occasionally even brighter than they are from Earth. Meteor showers can still be seen on Mars, though they originate from different sources due to the planet’s unique orbit.

Another beautiful phenomenon visible on Mars is the aurora, which unlike Earth’s polar-focused light displays, can occur all over the planet due to Mars’ lack of a global magnetic field. These auroras are typically ultraviolet and would require special instruments to see, but they add to the mysterious charm of Martian nights. Overall, the Martian sky offers a uniquely serene and otherworldly view of the cosmos, blending the familiar with the alien in a way that’s both humbling and awe-inspiring.

Video credit: NASA/JPL-Caltech/MSSS/ESO/Bill Dunford