Welcome to Sott.net
Sun, 25 Aug 2019
The World for People who Think

Comets


Meteor

It's called Apophis. It's 390m wide. And it could hit Earth in 31 years time

apophis asteroid
In Egyptian myth, Apophis was the ancient spirit of evil and destruction, a demon that was determined to plunge the world into eternal darkness.

A fitting name, astronomers reasoned, for a menace now hurtling towards Earth from outerspace. Scientists are monitoring the progress of a 390-metre wide asteroid discovered last year that is potentially on a collision course with the planet, and are imploring governments to decide on a strategy for dealing with it.

Nasa has estimated that an impact from Apophis, which has an outside chance of hitting the Earth in 2036, would release more than 100,000 times the energy released in the nuclear blast over Hiroshima. Thousands of square kilometres would be directly affected by the blast but the whole of the Earth would see the effects of the dust released into the atmosphere.

Comment: 15 years later, they're still reporting about Apophis as if it's breaking news.

As we said at the time...

sott.net meteor fireballs



Info

Lascaux Shaft Scene and cometary impacts

The Lascaux shaft scene is perhaps the most iconic of all European Palaeolithic cave artworks (see below). It shows a bison and human, apparently both dying and normally interpreted as a hunting scene. But we now know, beyond any reasonable doubt, the animal symbols represent constellations, and the Shaft Scene in particular very likely represents a date using precession of the equinoxes.
Lascaux Shaft Scene
© Copy of the Lascaux Shaft Scene, courtesy of Alistair Coombs
Using the zodiacal method and our ancient zodiac, the date 'written' in the scene is between 15,300 and 15,000 BC (see Prehistory Decoded). The similarity of this scene to Pillar 43 at Gobekli Tepe suggests it documents another asteroid or comet strike, this time from the direction of Capricornus (represented by the aurochs). It so happens that the Taurid meteor stream would rave radiated from this direction at this time, suggesting this artwork memorialises another strike from the Taurid system. Given the presence of a giant comet in the inner solar system at this time, such frequent impacts are entirely expected.

Very interestingly, this time span also corresponds to a sudden temperature fluctuation in the North Atlantic region (see Prehistory Decoded), documented by a Greenland ice core, and to a major cultural transition: the Magdalenian to Azillian.

Fireball 5

Perseids meteor shower to peak Monday night with stunning FIREBALL displays

Perseids meteor shower
© NASA/Ron Garan (@Astro_Ron)
Perseid meteor shower as seen from the International Space Station
It's that time of year again, when the spectacular Perseid meteor shower rains fire across the night sky. The days-long fireball fiesta is expected to peak this evening with an estimated 80 shooting stars per hour at its height.

Widely seen as one of the most entertaining celestial events of the year, the Perseids meteor shower is caused by meteoroids from the debris trail of the Comet 109P/Swift-Tuttle which orbits the sun once every 133 years.

Those in the Northern Hemisphere will be treated to the best views, provided they can escape the light pollution from towns and cities. The moon will frustrate proceedings somewhat as a full moon is due on Thursday, meaning the sky will likely be washed out for the majority of viewers, but fear not, as the Perseids have an ace up their sleeve.

Instead of shooting stars, stargazers can hunt for bright 'fireballs' which can last up to a second rather than merely fractions of a second like their shooting star brethren.

"...[T]he Perseids are rich in bright meteors and fireballs, so it will still be worth going out in the early morning to catch some of nature's fireworks," NASA says.

Fireball 4

'I thought it was Armageddon' - Perth residents stunned by early morning meteor fireball

Early risers around the Perth metropolitan area were stunned by a bright green light filling the night sky on Wednesday morning, but what looked like Armageddon was most likely a meteor, according to a Perth Observatory staffer.
Meteor Fireball
© Brisbane Times
Just before 6am 6PR News director Lisa Barnes was out for her morning run near Ellenbrook when she saw the phenomenon light up the sky.

"It was so amazing to see, it lit up the whole sky, a quick flash of light and then it drew my eyes to where I was heading (...) and then it was like a ball of light and I watched it fall."

Mrs Barnes said it was much bigger and brighter than a shooting star.

Comet 2

Spectacular Delta Aquariids meteor shower set to light up skies tonight

Meteor shower
© National Park Service
An annual meteor shower is set to peak tonight in a stunning night sky display that could see up to 20 flaming by per hour. Here's everything you need to know to catch the spectacular celestial show.

What?

The Delta Aquariids meteor shower is a spectacular display of what is essentially space dust and bits of debris from a comet (or comets) in our orbital path that flew close to the Sun.

The comet sheds particles that then smash into our atmosphere - around 60 miles above Earth - and zoom across our skies at about 90,000mph (150,000kph), at times vaporizing into shooting stars and leaving a trail of blazing light behind.

Comet 2

Impact hazard from disintegrating comets

Comet 73P
© NASA/JPL-Caltech/W.Reach [SSC/Caltech]
Last month, Bill Napier (co-creator of the coherent catastrophism theory, with Victor Clube) published his latest paper (MNRAS, vol. 488, p 1822-1827) on the impact hazard from disintegrating comets in the inner solar system. His focus is on a large 100 km comet in an Encke-like orbit. It is a sophisticated work that extends his earlier estimates, this time by combining explicit orbital simulations with a calibrated model of comet fragmentation (published by de Sisto et al. in 2009).

His aim, like mine in Prehistory Decoded, is to estimate the hazard to Earth from the kind of comet thought to have become trapped in our inner system a few tens of thousands of years ago. We know, pretty much, that this happened because of the massive zodiacal dust cloud and correlated fragments that remain in orbit.

He concludes that we can expect one or two impact collisions over the last 20,000 years, or so, with energy over 6000 Mt, and that this energy will likely be unevenly distributed across a hemispherical region. This is roughly 600 times the energy of the Tunguska impact, which itself was large enough to demolish one of our biggest modern-day cities (like Greater London).

This broadly supports my own estimates in Prehistory Decoded, based on simple fragmentation pathways and Opik's collision formula, where I find that we can expect one or two collisions with an energy of at least 10,000 Mt, and perhaps another ten with energy over 1,000 Mt, from the same sized comet over the same timescale. Great!

Fireball 5

Suspected meteorite crashes into rice field in India

Suspected Meteorite
© STR/AFP/Getty Images
The object was spotted ‘coming down from the sky’ and then excavated from a 150cm-deep hole by residents of Mahadeva village.
Madhubani/Patna: Farmers working in a paddy field at a village in Madhubani district were left shaken when a meteorite-like object weighing around 15kg fell from the sky, leaving a crater at the spot where it crashed.

Madhubani DM Shirsat Kapil Ashok told TOI that the incident took place around 2.30pm on Monday. "Agriculture labourers working the paddy field where the meteorite struck claimed that they saw a fireball-like object coming down from the sky and made a deep crater where it hit the ground. The farmers also saw smoke coming out from the spot in the water-filled agriculture field," Shirsat said.

Displaying the 'meteorite' wrapped in a red cloth on Tuesday morning, the Madhubani DM said the stone-like object has magnetic properties. He added that the mysterious object was kept secure in the treasury office at the Madhubani collectorate.

"I have written a letter to the principal secretary of the science and technology department along with a copy to the principal secretary of state art, culture and youth affairs department," Shirsat said, adding the sample was sent to Patna on Tuesday evening.

"The science and technology department will take a decision regarding further action. The object might be sent to space research organisations like ISRO or any museum," Shirsat said.

Fireball

Meteor fireball streaks across Australian skies

Fireball over Australia
© Screenshot YouTube
A screenshot from a YouTube video that is reportedly of the meteor that flew across the South East sky on the night of July 5.
Social media is buzzing with reports of a meteor spotted over the South Coast on Friday night.

On the Facebook group Australian Meteor Reports, administrator David Finlay said the meteor was spotted about 9pm on July 5 and believed it had come to ground somewhere in Victoria.

"I have reports of sonics from Forest Hill (Melbourne) to Mallacoota Vic. That's a distance of 400km. I've never heard of sonics being reported so far apart," he said in a Facebook post to the group.

He said sightings had been reported from as far north as Sydney and Orange.

"From these reports, and as long as this object was over land and not the ocean, I'm already predicting there are now meteorites on the ground somewhere in Victoria from this fall," he said.

Fireball 5

Nuke sensors detect asteroid explosion in the atmosphere over the Caribbean

Asteroid Explosion
© William Straka III/University of Wisconsin
On June 22nd at 21:25 UT, a small asteroid entered Earth's atmosphere and exploded in broad daylight south of Puerto Rico. Airwaves recorded by the Comprehensive Nuclear Test Ban Treaty Organization's infrasound station in Bermuda pegged the blast energy between 3 and 5 kilotons of TNT-a fraction of a WW II atomic bomb. The explosion was clearly visible in images from NOAA's GOES-16 weather satellite:


Meteor expert Peter Brown of the University of Western Ontario says the infrasound signal is consistent with a "small multi-meter sized near-Earth asteroid." According to data compiled by NASA's Center for Near Earth Object Studies, asteroids of this size and energy hit Earth's atmosphere about once a year. That means it's rare-but not exceptionally so.

Comet 2

ESA puts comet mission on fast track

Montezuma observing a comet.
© DEA / G. DAGLI ORTI/Getty Images
A sixteenth century illustration showing Montezuma observing a comet. The European Space Agency has a different plan.
Scientists at the European Space Agency (ESA) are working on a new "fast" mission to make the first flyby of a pristine comet - meaning one that has never before passed close to the sun.

Since the first comet mission, all the way back in 1978, numerous space agencies have made more than a dozen comet flybys, including one rendezvous and landing.

But never before has a mission attempted to visit a comet on its first plunge toward the sun, when its never-before-heated surface is almost unchanged from when it formed at the dawn of the solar system, some 4.5 billion years ago.

The recently approved mission, called Comet Interceptor, will also be unique in what it does as it nears its target.

Rather than simply flying by, it will split into four parts, each of which will whizz past the comet on a slightly different trajectory.

Three of these will be tiny instrument packages, which will view the comet from different angles. This will allow scientists back on Earth to create detailed 3D models not only of its surface, but of the gas, dust, and plasma surrounding it.

The fourth will be the mother ship, which will collect data from the smaller probes and relay it back to Earth.

"It's a novel concept," says Fabio Favata, head of the Strategy, Planning, and Coordination Office in ESA's Directorate of Science.

Details of the mission have yet to be determined, but the use of the word "fast" in its description doesn't mean it will be traveling at warp speed.