Comets

Follow-up on recent NEO objects

Ernesto Guido
Remanzacco Blogspot
Tue, 17 Nov 2020 22:25 UTC

Below you can find a selection of some objects for which we recently made follow-up observations at the "Osservatorio Salvatore di Giacomo, Agerola, ITALY" (MPC code L07; Observers E. Guido, A. Catapano, F. Coccia) while they still were on the NEOCP list. More details about the telescope, the magnitude, number of images & exposition, asteroid speed & PA etc. are on the images. Click on each image for a bigger version. All the processing has been made with TYCHO software by D. Parrott.

2020 VX5 (neocp designation C3WZUQ2) is an Apollo-type asteroid discovered by G96 Mt. Lemmon Survey on November 15, 2020. This asteroid has an estimated size of 55 m - 120 m (H=23.4) and it had a close approach with Earth at about 29 LD (Lunar Distances = ~384,000 kilometers) or 0.074 AU (1 AU = ~150 million kilometers) at 1950 UT on 11 Nov. 2020.

Tunguska explosion in 1908 caused by asteroid grazing Earth says new theory

Astronomy
Fri, 09 Oct 2020 18:44 UTC

A new theory explains the mysterious explosion in Siberia, scientists say, suggesting Earth barely escaped a far greater catastrophe.

In the early morning of June 30, 1908, a massive explosion flattened entire forests in a remote region of Eastern Siberia along the Tunguska River. Curiously, the explosion left no crater, creating a mystery that has puzzled scientists ever since — what could have caused such a huge blast without leaving any remnants of itself?

Now Daniil Khrennikov at the Siberian Federal University in Russia and colleagues have published a new model of the incident that may finally resolve the mystery. Khrennikov and co say the explosion was caused by an asteroid that grazed the Earth, entering the atmosphere at a shallow angle and then passing out again into space.

"We argue that the Tunguska event was caused by an iron asteroid body, which passed through the Earth's atmosphere and continued to the near-solar orbit," they say. If they are correct, the theory suggests Earth escaped an even larger disaster by a hair's breadth.

First some background. Scientists have long speculated on the cause of the Tunguska impact. Perhaps the most widely discussed idea is that the explosion was the result of an icy body, such as a comet, entering the atmosphere. The ice then rapidly heated up and evaporated explosively in mid-air but without ever hitting the ground.

Meteor fireball lights up Mexican skies and rains fire on northern states

RT
Wed, 07 Oct 2020 18:55 UTC

Residents across northeastern Mexico were stunned when a green-hued fireball lit up the night sky on Tuesday. Authorities reported that the fiery debris caused localised bushfires in the vicinity.

Reports came flooding in from across the northern state of Nuevo Leon after the suspected meteorite streaked across the sky at approximately 22:14 local time on Tuesday night.

Eyewitness and doorbell cam videos captured the intensity of the fiery phenomenon as it burned bright through the darkness.

Why are so many asteroids having close calls with Earth in 2020?

Michael Snyder
End of the American Dream
Wed, 23 Sep 2020 00:00 UTC

Have you noticed that it seems like stories about asteroids that are approaching the Earth are constantly in the news this year? It wasn't always this way. In the old days, maybe there would be a story about an asteroid every once in a while, and those stories were never a big deal. But now asteroids are zipping by our planet with frightening regularity, and several more very notable passes will happen over the next few weeks. For example, an asteroid that was just discovered on September 18th will come very, very close to the Earth on Thursday. According to NASA, it will actually come closer to our planet than many of our weather satellites...

An asteroid about the size of an RV or small school bus will zoom past the Earth on Thursday, NASA announced, passing within 13,000 miles of the Earth's surface.

That's much closer than the moon and is actually closer than some of our weather satellites.

This asteroid will speed by at more than 17,000 mph, but the good news is that it is so small that it would not be a serious threat even if it hit us.

But two other very large asteroids are also going to pass the Earth by the end of this month, and both of them are large enough to do an enormous amount of damage...

Comment: No, dear author, it is not just our imagination that the close calls with asteroids and other near-earth objects are increasing in frequency.

And here is why we think they are - from Sott.net in 2007:

War, rumors of war, corrupt governments run by psychopaths, phony terrorism, burgeoning police states...but is that all we have to worry about? What if there was something to put it all in context? Or rather, what if there is something else we are missing, something that is beyond the control of even the political and corporate elite; something that is driving them to attempt to herd the global population to an ever finer order of control...

A new sott.net video production:

The Younger Dryas impact research debate update

Dr. Martin Sweatman
Ancient Origins
Mon, 28 Sep 2020 18:15 UTC

© Jonathan Chen / CC BY-SA 4.0
Ice Age Diorama. From left to right: Equus hemionus, Mammuthus primigenius, Coelodonta antiquitatis, Bison exiguous skeletal mounts at the Tianjin Natural History Museum.

The Younger Dryas impact hypothesis has received considerable attention since its publication in 2007 in the prestigious peer-reviewed journal PNAS (Proceedings of the National Academy of Sciences). It suggests the Younger Dryas geological period and mini Ice-Age, from around 10,850 to 9600 BC, along with associated megafaunal extinctions and human societal changes, was triggered by a catastrophic cosmic impact, probably with a fragmented comet from the Taurid meteor stream.

As of now, this paper by Richard Firestone, Allen West and Simon Warwick-Smith and colleagues has amassed over 550 citations in Google Scholar - which is a lot! It is on its way to becoming a classic. But it has also received more than its fair share of criticism, mostly sustained from just a handful of vehement opponents. But has any of their criticism stuck? And what is the status of Firestone et al.'s paper today? Has the dust settled on an outcome? Are we there yet?

© Evolution of temperature in the Post-Glacial period according to Greenland ice cores/CC BY-SA 4.0
Evolution of temperatures in the post glacial period, after the Last Glacial Maximum (LGM), showing very low temperatures for the most part of the Younger Dryas, rapidly rising afterwards to reach the level of the warm Holocene, based on Greenland ice cores.

100 million-year-old meteorite crater discovered Down Under

Laura Geggel
Live Science
Wed, 23 Sep 2020 22:30 UTC

© Resource Potentials
A color-coded gravity image of the Ora Banda Impact Crater site. The crater (deep blue) is in the middle of the image.

Gold miners in the Australian Outback recently discovered a gigantic meteorite crater dating to about 100 million years ago, back when dinosaurs roamed the Earth.

Found near the Western Australian town of Ora Banda, the newly dubbed Ora Banda Impact Crater is about 3 miles (5 kilometers) across. This huge hole was likely created by a meteorite up to 660 feet (200 meters) wide, or longer than the length of two American football fields, according to Resourc.ly, a Western Australia news outlet.

When geologists at Evolution Mining, an Australian gold mining company, came across some unusual rock cores at Ora Banda, they called Jayson Meyers, the principal geophysicist, director and founder of Resource Potentials, a geophysics consulting and contracting company in Perth. Meyers examined the geologists' drill core samples, as well as rock samples from the site, and he immediately noticed the shatter cones — telltale signs of a meteorite crash.

Shatter cones form when high-pressure, high-velocity shock waves from a large impacting object — such as a meteorite or a gigantic explosion (such as would occur at a nuclear testing site) — rattle an area, according to the Planetary Science Institute (PSI), a nonprofit group based in Tucson, Arizona, which was not involved with the new find. These shock waves shatter rock into the unique shatter cone shape, just like a mark that a hard object can leave on a car's windshield.

Because "we know they didn't do any nuclear testing at Ora Banda," the evidence suggests that an ancient impact crater hit the site, Meyers told Resourc.ly.

Strange, glowing ultraviolet aurora detected around a comet

Michelle Starr
Science Alert
Mon, 21 Sep 2020 05:20 UTC

Aurora - the dancing glow of ionised particles in Earth's upper atmosphere - is not unique to our planet.

The phenomenon has been spotted shining in the atmospheres of every other planet except Mercury. Even Jupiter's moons Ganymede and Europa have auroras.

Never, until now, had an aurora been detected on a comet.

But, in a new analysis of data collected by the Rosetta spacecraft, the space around Comet 67P Churyumov-Gerasimenko (67P/C-G) has been observed glowing with far-ultraviolet auroral radiation.

"I've been studying the Earth's auroras for five decades," said physicist Jim Burch of the Southwest Research Institute.

"Finding auroras around 67P, which lacks a magnetic field, is surprising and fascinating."

Auroras are generated by the excitation of charged particles in an atmosphere.

Here on Earth, for instance, the solar wind blows into the magnetosphere and interacts with charged particles there.

These particles rain down into the upper atmosphere and are funneled up the magnetic field lines to the poles, where they manifest as rippling curtains of light.

It works differently on different bodies, though. The auroras of Ganymede and Europa are generated by interactions with Jupiter's magnetic field.

Venus doesn't have a magnetic field of its own that we know of, but interactions with the solar wind creates one strong enough to trigger auroras.

Mars' atmosphere is extremely thin, but its weak magnetic field can support auroras.

New Comet C/2020 S3 (Erasmus)

Ernesto Guido
Remanzacco Blogspot
Mon, 21 Sep 2020 18:12 UTC

CBET 4885 & MPEC 2020-S119, issued on 2020, September 20, announce the discovery of a comet (magnitude ~18.5) by Nicolas Erasmus (South African Astronomical Observatory), in four 30-s CCD images taken in 5" seeing on Sept. 17.6 UT with a 0.5-m f/2 Schmidt reflector at Mauna Loa, Hawaii, in the course of the "Asteroid Terrestrial-Impact Last Alert System" (ATLAS) search program. The new comet has been designated C/2020 S3 (Erasmus).

We performed follow-up measurements of this object while it was still on the PCCP webpage.

Stacking of 151 unfiltered exposures, 30 seconds each, obtained remotely on 2020, September 19.1 from L07 (Osservatorio Salvatore di Giacomo, Agerola) through a 0.5 m f/8 Ritchey Chretien + CCD FLI PL4240, shows that this object is a comet with a diffuse coma about 20" in diameter.

Our confirmation image (click on it for a bigger version)

Amateur astronomer discovers kilometer-size asteroid

David Dickinson
Sky & Telescope
Fri, 11 Sep 2020 21:58 UTC

We have not yet found all the large, potentially hazardous near-Earth objects, as highlighted by the recent discovery of a kilometer-size asteroid.

Amateur astronomer Leonardo Amaral was scanning the skies on the night of August 27th, imaging a region in the constellation Indus, when he picked up a cosmic interloper: the asteroid 2020 QU₆.

Amaral used the 0.3-meter reflector at the Campo dos Amarais observatory near Sau Paulo, Brazil. The observatory had received a recent upgrade thanks to a Planetary Society grant.

Turns out, 2020 QU₆ is about a kilometer across — a surprising find given that most such large objects have been found and cataloged. The asteroid orbits the Sun once every 3.26 years on an orbit inclined 23.5° relative to the ecliptic plane. It poses no current threat to Earth, having passed within 40 million kilometers (24 million miles, more than 100 times the Earth-Moon distance) on September 10th. That's the closest the asteroid will come to Earth in the 21st century.

The long history of comet phobia

Jess Romeo
JSTOR Daily
Thu, 03 Sep 2020 18:20 UTC

Nowadays, the appearance of a comet, like the recently soaring NEOWISE, is likely to inspire wonder and excitement. But for much of human history, a comet was more likely to inspire blood-curdling fear.

"Almost always in classical times comets were regarded as portents, generally as warnings of dire events," writes historian Duane Koenig. (They were also sometimes "harbingers of happy things," like the birth of heroes, prophets, or kings.)

Ancient records show that thousands of years ago, "Persians and Koreans viewed comets as of evil nature and often [announced] war with the country in whose direction the tail pointed," writes Koenig. Over in Rome, comets were an object of fear and worship. Historian Geraldine Herbert-Brown finds that Pliny the Elder paid "particular attention to comets, and the terror they had caused humans in the course of history." According to Pliny, a comet would appear at "crucial intervals" starting in 49 BCE, "glaring terribly when Nero succeeded Claudius, and then continuously throughout Nero's principáte."

Comets — also called "bearded stars" — were consistently seen as bad news for rulers. Around 70 CE, the Roman emperor Vespasian was cautioned about a comet. "He contended the bearded star did not concern him because he was bald. It threatened his neighbor, the king of the Parthians, who was hairy," writes Koenig.