Comets


Fireball

Meteor fireball reported over Japan on January 15

Fireball over Japan
© CCO
Reports suggest that what appeared to be a flashy object traveling at breakneck speed over Japanese skies could be a meteorite after residents heard a loud explosion a few minutes after its passage.

Social media chatter among Japanese users is currently focused on the sighting of a luminous "fireball" that dashed across the sky on Monday morning. The celestial spectacle was observed primarily in Japan's eastern and northeastern regions, according to media reports.

Daichi Fujii, the curator of the local history museum in Hiratsuka, Kanagawa, was among the first to provide an account of the event. He posted the footage of the speeding object in the sky on his X social media page. Fujii noted that the clip was recorded on camera at his home in Hiratsuka and another in the neighboring Shizuoka Prefecture.

Microscope 1

New genes found that can arise 'from nothing'

DNA replication 1
© Ari LöytynojaResearchers studied an error mechanism in DNA replication, and noticed that some errors create palindromes that can fold into hairpin structures.
The complexity of living organisms is encoded within their genes, but where do these genes come from? Researchers at the University of Helsinki resolved outstanding questions around the origin of small regulatory genes, and described a mechanism that creates their DNA palindromes. Under suitable circumstances, these palindromes evolve into microRNA genes.

The human genome contains ca. 20,000 genes that are used for the construction of proteins. Actions of these classical genes are coordinated by thousands of regulatory genes, the smallest of which encode microRNA molecules that are 22 base pairs in length. While the number of genes remains relatively constant, occasionally, new genes emerge during evolution. Similar to the genesis of biological life, the origin of new genes has continued to fascinate scientists.

All RNA molecules require palindromic runs of bases that lock the molecule into its functional conformation. Importantly, the chances of random base mutations gradually forming such palindromic runs are extremely small, even for the simple microRNA genes.

Hence, the origin of these palindromic sequences has puzzled researchers. Experts at the Institute of Biotechnology, University of Helsinki, Finland, resolved this mystery, describing a mechanism that can instantaneously generate complete DNA palindromes and thus create new microRNA genes from previously noncoding DNA sequences.

Fireball 3

The Geminids are still a mystery

Above: Geminids over the Czech Republic in 2018.
© Petr HorálekAbove: Geminids over the Czech Republic in 2018.
Every great mystery novel has an unexpected twist. Apparently the same is true of meteor showers.

A paper published in the Planetary Science Journal reports a surprising new twist in the mystery of the Geminids, a strong annual meteor shower that has puzzled astronomers for more than a century.

"Our work has upended years of belief about 3200 Phaethon, the source of the Geminids," says co-author Karl Battams of the Naval Research Lab. "It's not what we thought it was."

The Geminids peak every year in mid-December, scattering hundreds of bright meteors across northern winter skies. Numerically it is the best meteor shower of the year.

As meteor showers go, Geminids are newcomers. They first appeared in the mid-1800s when an unknown stream of debris crossed Earth's orbit. Surprised, 19th century astronomers scoured the sky for the parent comet, but they found nothing. The search would continue for another 100 years.

Enter NASA. In 1983, the space agency's Infrared Astronomical Satellite (IRAS) found an object now called "3200 Phaethon." It was definitely the source of the Geminids. The orbit of 3200 Phaethon was such a close match to that of the Geminid debris stream, no other conclusion was possible. Yet here was a puzzler: 3200 Phaethon appeared to be a rocky asteroid.

Fireball 5

Best of the Web: Comets may have caused Earth's great empires to fall

Triumph Death Pieter Bruegel Elder
'The Triumph of Death', by Pieter Bruegel the Elder
Recent scientific discoveries are shedding new light on why great empires such as Egypt, Babylon and Rome fell apart, giving way to the periodic "dark ages'' that punctuate human history.

At least five times during the last 6,000 years, major environmental calamities undermined civilizations around the world. Some researchers say these disasters appear to be linked to collisions with comets or fragments of comets such as the one that broke apart and smashed spectacularly into Jupiter five years ago.

The impacts, yielding many megatons of explosive energy, produced vast clouds of smoke and dust that circled the globe for years, dimming the sun, driving down temperatures and sowing hunger, disease and death.

The last such global crisis occurred between A.D. 530 and 540 - at the beginning of the Dark Ages in Europe - when Earth was pummeled by a swarm of cosmic debris.

Info

Recently discovered nova investigated by astronomers

AT 2023prq
© Research Notes of the AAS (2023). DOI: 10.3847/2515-5172/ad0a99DSS image of the Andromeda Galaxy and its surroundings. AT 2023prq is shown (star) with the two tidal stream classical novae (AT 2016dah and AT 2017fyp).
Astronomers from the Liverpool John Moores University have performed photometric and spectroscopic observations of a recently discovered nova, known as AT 2023prq. Results of the observational campaign, published in the November issue of the Research Notes of the American Astronomical Society (AAS), shed more light on the nature of this nova.

A nova is a star experiencing a sudden increase in brightness and slowly returning to its original state, a process that could last many months. Such an outburst, which releases an immense amount of energy, is the result of the accretion process in a close binary system containing a white dwarf and its companion. Studying novae is crucial in advancing our knowledge about fundamental astrophysical processes, including stellar evolution.

AT 2023prq (other designation ZTF23aaxzvrr) was detected by the Zwicky Transient Facility (ZTF) on August 15, 2023, in the halo of the Andromeda galaxy (or Messier 31, M31). It had an r′-band magnitude of 17.13 and shortly after its detection, follow-up observations of this nova commenced in order to get more insights into its properties.

Astronomers Michael Healy-Kalesh and Daniel Perley from the Liverpool John Moores University in Liverpool, UK, were among the first to observe AT 2023prq after it was identified. They used the Liverpool Telescope (LT) and various other ground-based facilities to monitor the nova until the end of August 2023.

Comet 2

Volcanic 'devil comet' racing toward Earth resprouts its horns after erupting again

The massive volcanic comet 12P/Pons-Brooks, which grows giant horns when it erupts, has exploded for a third time in five months as it continues to race toward the sun.
12P/Pons-Brooks
© Comet Chasers/Richard MilesThe "devil" comet's distinctive horns were first spotted after a major eruption on July 20.
A volcanic "devil comet" that is racing toward Earth erupted again on Halloween, causing it to regrow its distinctive "horns." The latest outburst, which was the second within a month and the third since July, is a reminder that the comet is becoming more volcanically active as it continues its journey toward the heart of the solar system.

The comet, named 12P/Pons-Brooks (12P), is a cryovolcanic, or cold volcano, comet. Like other comets, 12P has a solid nucleus — a hard, icy shell filled with ice, gas and dust — that is surrounded by a fuzzy cloud, or coma made of materials that leak out of the comet's insides.

But unlike non-volcanic comets, radiation from the sun can superheat 12P's interior, causing pressure to build up until it becomes so intense it cracks the nucleus' shell from the inside and sprays its icy guts into space. These eruptions cause the comet's coma to expand and brighten as it reflects more sunlight toward Earth.

When the comet erupts, its coma forms iconic devil "horns." These occur because 12P's large nucleus, which spans around 10.5 miles (17 kilometers) across, has an unusual "notch" on its surface, which blocks the outflow of cryomagma into space and causes its expanded coma to grow with an irregular shape.

Crusader

SOTT Focus: Witches, Comets and Planetary Cataclysms

witch1
© Dot Connector Magazine
When you think of Halloween, what is the first image that comes to mind? I took a little informal poll among my friends, family and associates. Guess what image came in first? Jack-o-lanterns! Bet you thought I was going to say "witches". Well, I sure thought it would be witches, but they only came in a close second!..

When I think of Halloween, I think of grade-school art projects where we cut out silhouettes of witches to paste onto large yellow moons made of construction paper. The witch was always on a broom with her black dress flying in the wind, accompanied by a black cat sitting on the back of the broom. I wondered even then how the cat managed to stay on and why anybody would think that straddling a broomstick as a seat would be even remotely comfortable.

Info

Shock fractures in quartz and the Younger Dryas impact at Abu Hureyra (near Gobekli Tepe)

Impact Event
© Prehistory Decoded
Researchers associated with the comet research group have just published four new papers on micro-fractures in quartz, and how they can be used to diagnose cosmic impacts. The first paper is a detailed study linking shocked quartz to airbursts. The next three below apply this new understanding to the Younger Dryas impact specifically at Abu Hureyra, which is about 100 miles south of Gobekli Tepe.

The journal is also new - "Airbursts and cratering impacts". It was set up so that papers rejected by the "impact mafia" can still be fairly reviewed and published. The impact mafia is a determined group of researchers who are expert in the more well-established science of large ground impacts where the existence of a large crater makes the diagnosis of an impact obvious. By requiring the same kind of evidence for the diagnosis of all cosmic impacts, they are effectively preventing the diagnosis of lower-energy impact events, for example small ground impacts or large airbursts that significantly affect the ground, i.e. precisely the kind of impacts central to the Younger Dryas impact hypothesis. Inevitably, this leads to under-reporting of these smaller impact events. Parallels with the "Clovis first mafia" are apt.

Arrow Up

NASA predicts large asteroid impact could be in Earth's future

Asteroid Bennu
© NASA/Goddard/University of Arizona/CSA/York/MDA via APThis undated image made available by NASA shows the asteroid Bennu from the OSIRIS-REx spacecraft. On Wednesday, Aug. 11, 2021, scientists said they have a better handle on asteroid Bennu’s whereabouts for the next 200 years. The bad news is that the space rock has a slightly greater chance of clobbering Earth than previously thought. But don’t be alarmed: Scientists reported that the odds are still quite low that Bennu will hit us in the next century.
NASA scientists are predicting a chance that asteroid Bennu will strike Earth in the future, potentially affecting an area the size of Texas.

Bennu is a Near-Earth Object (NEO) that passes by the planet roughly every six years, and experts have been watching it since it was discovered in September 1999.

According to scientists, Bennu has a chance to pass through what they call a "gravity keyhole," which would send it on a collision course with Earth in the year 2182.

A new paper from the OSIRIS-REx science team predicts Bennu has a 0.037% chance (1 in 2,700) of hitting Earth; this will largely depend on another flyby. In 2135, Bennu will zoom past Earth just close enough that our planet's gravitational pull could affect it in just the right way to put it on a path to hit us on Sept. 24, 2182 — almost 159 years to the day from this writing.

Fireball 5

'Lightning' on Venus is actually meteors burning up in planet's atmosphere, study says

But future missions, scientists say, are safe from both rare lightning strikes and meteors known to burn up high above the planet's clouds.
Venus
© FutureVenus as clicked by the Akatsuki orbiter in March 2018.
The thick, acid-rich clouds of Venus continue to shroud the planet next door in mystery.

Scientists have long-debated whether intriguing light flashes recorded by previous Venus missions are evidence of lightning strikes on the planet. If those flashes really represent lightning, future missions to the windy planet need to be designed such that they are strong enough to survive the bolts, which are known to damage electronics here on Earth.

Moreover, lightning on Venus means Earth's cosmic neighbor would join the rare planetary club whose current members — Earth, Jupiter and Saturn — host lightning bolts in their clouds. Such flickers of light would also be unique on the world in that they'd exist despite Venus' clouds lacking water, a substance considered key in creating electrical charges.

So, scientists are excited by the possibility of lightning on Venus — but the evidence so far has been circumstantial at best.

And now, a new study suggests lightning might be extremely rare on the planet. Instead, it offers the possibility that meteors burning up high in Venus' atmosphere are very likely responsible for the detected light flashes.