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🔗 Environment 🔗 Meteorology 🔗 Astronomy 🔗 Middle Ages 🔗 Middle Ages/History 🔗 Geology 🔗 Glaciers 🔗 Solar System

The 774–775 carbon-14 spike is an observed increase of 1.2% in the concentration of carbon-14 isotope in tree rings dated to 774 or 775, which is about 20 times as high as the normal background rate of variation. It was discovered during a study of Japanese cedar trees, with the year of occurrence determined through dendrochronology. A surge in beryllium isotope ¹⁰
Be, detected in Antarctic ice cores, has also been associated with the 774–775 event. It is known as the Miyake event or the Charlemagne event and it produced the largest and most rapid rise in carbon-14 ever recorded.

The event appears to have been global, with the same carbon-14 signal found in tree rings from Germany, Russia, the United States, Finland and New Zealand.

The signal exhibits a sharp increase of around 1.2% followed by a slow decline (see Figure 1), which is typical for an instant production of carbon-14 in the atmosphere, indicating that the event was short in duration. The globally averaged production of carbon-14 for this event is calculated as Q = 1.3×10⁸ ± 0.2×10⁸ atoms/cm².

🔗 United States 🔗 Biography 🔗 Biography/science and academia 🔗 Astronomy 🔗 United States/Arizona 🔗 Astronomy/Solar System

Robert Burnham Jr. (June 16, 1931 – March 20, 1993) was an American astronomer, best known for writing the classic three-volume Burnham's Celestial Handbook. He is the discoverer of numerous asteroids including the Mars crossing asteroid 3397 Leyla, as well as six comets.

Burnham's late years were tragic; he died destitute and alone. However, he is remembered by a generation of deep sky observers for his unique contribution to astronomy, the Celestial Handbook. The main-belt asteroid 3467 Bernheim was named in his honor.

🔗 Physics 🔗 Astronomy 🔗 Time 🔗 Holidays 🔗 Festivals

A solstice is an event occurring when the Sun appears to reach its most northerly or southerly excursion relative to the celestial equator on the celestial sphere. Two solstices occur annually, around June 21 and December 21. In many countries, the seasons of the year are determined by reference to the solstices and the equinoxes.

The term solstice can also be used in a broader sense, as the day when this occurs. The day of a solstice in either hemisphere has either the most sunlight of the year (summer solstice) or the least sunlight of the year (winter solstice) for any place other than the Equator. Alternative terms, with no ambiguity as to which hemisphere is the context, are "June solstice" and "December solstice", referring to the months in which they take place every year.

The word solstice is derived from the Latin sol ("sun") and sistere ("to stand still"), because at the solstices, the Sun's declination appears to "stand still"; that is, the seasonal movement of the Sun's daily path (as seen from Earth) pauses at a northern or southern limit before reversing direction.

🔗 Physics 🔗 Astronomy

The berserker hypothesis, also known as the deadly probes scenario, is the idea that humans have not yet detected intelligent alien life in the universe because it has been systematically destroyed by a series of lethal Von Neumann probes. The hypothesis is named after the Berserker series of novels (1963-2005) written by Fred Saberhagen.

The hypothesis has no single known proposer, and instead is thought to have emerged over time in response to the Hart–Tipler conjecture, or the idea that an absence of detectable Von Neumann probes is contrapositive evidence that no intelligent life exists outside of the Sun's Solar System. According to the berserker hypothesis, an absence of such probes is not evidence of life's absence, since interstellar probes could "go berserk" and destroy other civilizations, before self-destructing.

In his 1983 paper "The Great Silence", astronomer David Brin summarized the frightening implications of the berserker hypothesis: it is entirely compatible with all the facts and logic of the Fermi paradox, but would mean that there exists no intelligent life left to be discovered. In the worst-case scenario, humanity has already alerted others to its existence, and is next in line to be destroyed.

There is no need to struggle to suppress the elements of the Drake equation in order to explain the Great Silence, nor need we suggest that no [intelligent aliens] anywhere would bear the cost of interstellar travel. It need only happen once for the results of this scenario to become the equilibrium conditions in the Galaxy. We would not have detected extra-terrestrial radio traffic – nor would any [intelligent aliens] have ever settled on Earth – because all were killed shortly after discovering radio.

🔗 Astronomy 🔗 Moon 🔗 Solar System

A transient lunar phenomenon (TLP) or lunar transient phenomenon (LTP) is a short-lived light, color, or change in appearance on the surface of the Moon. The term was created by Patrick Moore in his co-authorship of NASA Technical Report R-277 Chronological Catalog of Reported Lunar Events, published in 1968.

Claims of short-lived lunar phenomena go back at least 1,000 years, with some having been observed independently by multiple witnesses or reputable scientists. Nevertheless, the majority of transient lunar phenomenon reports are irreproducible and do not possess adequate control experiments that could be used to distinguish among alternative hypotheses to explain their origins.

Most lunar scientists will acknowledge transient events such as outgassing and impact cratering do occur over geologic time. The controversy lies in the frequency of such events.

🔗 Astronomy 🔗 Astronomy/Solar System

The Galilean moons (), or Galilean satellites, are the four largest moons of Jupiter: Io, Europa, Ganymede, and Callisto. They are the most readily visible Solar System objects after Saturn, the dimmest of the classical planets; though their closeness to bright Jupiter makes naked-eye observation very difficult, they are readily seen with common binoculars, even under night sky conditions of high light pollution. The invention of the telescope enabled the discovery of the moons in 1610. Through this, they became the first Solar System objects discovered since humans have started tracking the classical planets, and the first objects to be found to orbit any planet beyond Earth.

They are planetary-mass moons and among the largest objects in the Solar System. All four, along with Titan, Triton, and Earth's Moon, are larger than any of the Solar System's dwarf planets. The largest, Ganymede, is the largest moon in the Solar System and surpasses the planet Mercury in size (though not mass). Callisto is only slightly smaller than Mercury in size; the smaller ones, Io and Europa, are about the size of the Moon. The three inner moons — Io, Europa, and Ganymede — are in a 4:2:1 orbital resonance with each other. While the Galilean moons are spherical, all of Jupiter's remaining moons have irregular forms because they are too small for their self-gravitation to pull them into spheres.

The Galilean moons are named after Galileo Galilei, who observed them in either December 1609 or January 1610, and recognized them as satellites of Jupiter in March 1610; they remained the only known moons of Jupiter until the discovery of the fifth largest moon of Jupiter Amalthea in 1892. Galileo initially named his discovery the Cosmica Sidera ("Cosimo's stars") or Medicean Stars, but the names that eventually prevailed were chosen by Simon Marius. Marius discovered the moons independently at nearly the same time as Galileo, 8 January 1610, and gave them their present individual names, after mythological characters that Zeus seduced or abducted, which were suggested by Johannes Kepler in his Mundus Jovialis, published in 1614. Their discovery showed the importance of the telescope as a tool for astronomers by proving that there were objects in space that cannot be seen by the naked eye. The discovery of celestial bodies orbiting something other than Earth dealt a serious blow to the then-accepted (among educated Europeans) Ptolemaic world system, a geocentric theory in which everything orbits around Earth.

🔗 Spaceflight 🔗 Astronomy 🔗 Astronomy/Solar System 🔗 Astronomy/Moon

On April 11, 2019, the Israeli spacecraft Beresheet crashed into the Moon during a failed landing attempt. Its payload included a few thousand tardigrades. Initial reports suggested they could have survived the crash landing. If any of them did survive, they would be the second animal species to reach the Moon, after humans.

We believe the chances of survival for the tardigrades... are extremely high.

🔗 Physics 🔗 Astronomy

Rømer's determination of the speed of light was the demonstration in 1676 that light has a finite speed and so does not travel instantaneously. The discovery is usually attributed to Danish astronomer Ole Rømer, who was working at the Royal Observatory in Paris at the time.

By timing the eclipses of the Jovian moon Io, Rømer estimated that light would take about 22 minutes to travel a distance equal to the diameter of Earth's orbit around the Sun. This would give light a velocity of about 220,000 kilometres per second, about 26% lower than the true value of 299,792 km/s.

Rømer's theory was controversial at the time that he announced it and he never convinced the director of the Paris Observatory, Giovanni Domenico Cassini, to fully accept it. However, it quickly gained support among other natural philosophers of the period such as Christiaan Huygens and Isaac Newton. It was finally confirmed nearly two decades after Rømer's death, with the explanation in 1729 of stellar aberration by the English astronomer James Bradley.

🔗 Physics 🔗 Astronomy 🔗 Chemistry 🔗 Water 🔗 Astronomy/Solar System

Superionic water, also called superionic ice or ice XVIII, is a phase of water that exists at extremely high temperatures and pressures. In superionic water, water molecules break apart and the oxygen ions crystallize into an evenly spaced lattice while the hydrogen ions float around freely within the oxygen lattice. The freely mobile hydrogen ions make superionic water almost as conductive as typical metals, making it a superionic conductor. It is one of the 19 known crystalline phases of ice. Superionic water is distinct from ionic water, which is a hypothetical liquid state characterized by a disordered soup of hydrogen and oxygen ions.

While theorized for decades, it was not until the 1990s that the first experimental evidence emerged for superionic water. Initial evidence came from optical measurements of laser-heated water in a diamond anvil cell, and from optical measurements of water shocked by extremely powerful lasers. The first definitive evidence for the crystal structure of the oxygen lattice in superionic water came from x-ray measurements on laser-shocked water which were reported in 2019.

If it were present on the surface of the Earth, superionic ice would rapidly decompress. In May 2019, scientists at the Lawrence Livermore National Laboratory (LLNL) were able to synthesize superionic ice, confirming it to be almost four times as dense as normal ice and black in color.

Superionic water is theorized to be present in the mantles of giant planets such as Uranus and Neptune.

🔗 Astronomy 🔗 Astronomy/Astronomical objects

2024 YR₄ is an asteroid between 40 and 90 metres (130 and 300 ft) in diameter, classified as an Apollo-type (Earth-crossing) near-Earth object. It was discovered by the Chilean station of the Asteroid Terrestrial-impact Last Alert System (ATLAS) on 27 December 2024. As of 5 February 2025, 2024 YR₄ was rated 3 on the Torino scale with a 1 in 53 (1.9%) chance of impacting Earth on 22 December 2032. NASA gives a Palermo Technical Impact Hazard Scale rating of −0.40 for 2024 YR₄, which corresponds to an impact hazard of 39.8% of the background hazard level. The discovery has triggered the first step in planetary defense responses, in which all available telescopes are asked to gather data about the object and United Nations-endorsed space agencies are prompted to begin planning for asteroid threat mitigation.

Preliminary analysis of spectra and photometric timeseries of this asteroid suggests it is a stony S-type or L-type asteroid with a rotation period near 19.5 minutes. The asteroid previously made a close approach of 828,800 kilometres (515,000 miles; 2.156 lunar distances) to Earth on 25 December 2024 (two days before its discovery), and is now moving away from Earth. It will make its next close approach around 17 December 2028. By early April 2025 and until June 2028, 2024 YR₄ will have moved too far away from Earth to be observed by ground-based telescopes. Space-based infrared telescopes such as the James Webb Space Telescope may be able to observe 2024 YR₄ when it is far from Earth.