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Wed, 30 Sep 2020
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Comets

Star

A Cloudy Comet and a Wispy Nebula

I love celestial coincidences. There are just so many of them.

Why do some of the closest bright stars to the solar system lie in front of the bright stars of the winter Milky Way? This foreground and background have nothing to do with each other, but they combine to make our winter evening sky especially starry-bright.

Why, from Earth's viewpoint, do planets shine just about as bright as the brightest stars?

Why are the apparent sizes of the Moon and Sun so nearly alike? They're just right to give us the most spectacular-looking (if rather rare) total solar eclipses.

Image
©S&T: Dennis di Cicco & Sean Walker
On the evening of March 5th, big dim Comet Holmes was passing big dim NGC 1499, the California Nebula in Perseus. For this image Dennis di Cicco took 30-minute exposures through blue and green filters and a 50-minute exposure through a red filter, using a 5-inch Tele Vue NP127is refractor and an Apogee U16M CCD camera. Click image for larger view. (Look carefully at the large view and you'll see the faint nucleus of the comet as a tiny red-green-blue streak; it moved between the three exposures.) The field is roughly 3° tall, with north up.

Star

Scientists Say Comet Smashed Into Southern Germany In 200 BC

A comet or asteroid smashed into modern-day Germany some 2,200 years ago, unleashing energy equivalent to thousands of atomic bombs, scientists reported on Friday.

crater Chiemgau
© Chiemgau Impact Research Team
The largest crater in the Chiemgau field in Bavaria is water-filled Tuttensee, located near the village of Marwang. At the water surface, Tüttensee measures 1,200 feet across. but the original crater may have been twice as large. Photo credit: Chiemgau Impact Research Team.

Star

Evidence Confirms Electric Comet Model

It appears that predictions made by Wal Thornhill and the Electric Comet model are being quickly confirmed, whether mainstream astronomers like it or not. In the end, it seems nature will be the arbiter of which model is the most accurate and predictive.

Star

Comets in History: The Journal of Hamel and Korea

At the end of the year [1664] we saw shortly after each other two tail-stars or comets arising in the sky. The first one, in the southeast, was to be seen for almost two months. After that another one appeared in the southeast. The appearance of these celestial bodies, caused a big panic in the country. The war-fleet was standing by, the guards of the ports were reinforced, all fortresses were provided with extra provisions and extra munitions, while cavalry and infantry were exercising daily. Also was it not allowed to light any lamps, especially not in the cities along the coast. This fear was caused by the fact that when the Tartarians invaded the country, there were also similar signs in the firmament, as well as at the beginning of the war with the Japanese.

Star

Today in Cape history: Third comet visible in 12 years



Comet 1664
©Unknown

On this day in 1664, as described in the book "Cape Cod Historical Almanac" by Donald G. Trayser, "the people of Cape Cod and other parts of New England saw the last of a great comet which excited fear and awe. It appeared November 8th last, and continued to this date, the third comet witnessed by early settlers in the space of 12 years.

Telescope

Boston University Astronomers Map Full Extent Of Mercury's Comet-Like Tail

Boston University astronomers released new images of Mercury that capture both the source regions of and, for the first time, the extraordinary length of the planet's comet-like tail. Earlier research had mapped-out Mercury's sodium gas tail to approximately 40,000 kilometers, but planetary scientists from BU's Center for Space Physics (CSP) have found that the tail can extend more than 2.5 million kilometers, or 1.5 million miles, from the planet.

mercury comet like tail
©Center for Space Physics, Boston University
Mercury's tail of sodium gas captured by a wide-angle telescope showing an enormous extent of the atoms escaping from the planet's surface. The insert shows the source regions of the tail gases imaged at a different time using a very narrow field of view telescope. The source regions occur at high latitudes, probably related to solar wind access to Mercury's surface along specific magnetic field lines. The impacts of the solar wind ions and electrons result in sputtering sodium from the surface. Since Mercury is close to the Sun, the sputtered atoms are pushed away by the pressure of light, with this photon radiation pressure leading to the long tail. The brightness of the source regions is about 1 million times greater than the faintest part of the distant tail. The sizes of the source regions span about 1/2 of the planet's radius, while the tail extends to about 1500 times the radius of the planet, about 1.5 million miles.

Bizarro Earth

ABC: Man may need to live in space to survive cometary impacts, global disasters

Will humans need to live as space nomads to survive? Possibly, says Neil deGrasse Tyson of the American Museum of Natural History.

"It may be," says Tyson, "that our only insurance policy against extinction is to become a multi-planet, space faring species."

Worries of climate change and unexpected catastrophe on Earth, compounded with humankind's natural curiosity about what lies beyond, compel private industry and NASA alike not only to wonder "what if," but to prepare for the "when."

Telescope

Kamikaze comet ripples Saturn's ring

A smack from a small comet in the 1980s may be responsible for ripples in one of Saturn's rings, images from NASA's Cassini spacecraft suggest. The finding is another indication that the rings are not static and can change on human timescales.

Cassini observations have revealed bright and dark bands in Saturn's innermost ring, called the D ring. The bands are getting more closely spaced as time goes on - Hubble Space Telescope images reveal they were 60 kilometres apart in 1995 and Cassini shows they have been shrinking over the last few years and are just 30 km apart now.

©NASA/JPL/Space Science Institute
The edge of the D ring is seen at the centre of this image, showing a banded structure that has gradually became more finely spaced since it was first detected by Hubble in 1995

Ambulance

The Comet and the Chicago Fire

For nearly one and a half centuries, the cause of the most notorious fire in U.S. history has been a source of "heated" controversy. Some researchers suggest that a disintegrating comet ignited the blaze. But the electrical theorists say that evidence most often ignored offers the best clues.

"With the heat increased the wind, which came howling across the prairie, until at last there arose a perfect hurricane. Mighty flakes of fire, hot cinders, black, stifling smoke, were driven fiercely at the people, and amid the terrible excitement hundreds of them had their very clothes burned off their backs, as they stood there watching with tearful eyes the going down of so many houses". -- James Goodsell's History of the Great Chicago Fire, October 8, 9, and 10, Published 1871 by J.H. and C.M. Goodsell.

Better Earth

Comet Biela and Mrs. O'Leary's Cow



Image
©Unknown
Cometary fire ruins, as seen from the corner of Dearborn and Monroe Streets, Chicago, 1871.


Last night we watched Super Comet - After the Impact, a Discovery Channel special that basically takes the comet that wiped out the dinosaurs and put into modern times. They added some cheesy drama, following the struggles of several individuals or groups, before, during, and after the impact, to show how people would react to such a global cataclysm. They used the same type of cometary body assumed to have caused the extinction of the dinosaurs, the same size, same impact location, and utilized all the computer modeling they have done on this past event to try to show what might happen (and to show what they think happened then). Not terribly creative and suggests that they really don't know all the effects of such an impact and are just putting things together from what little they have been able to figure out about that one impact, some (or much) of which may be just speculation, though I'm sure that there is some good science going on there.

This show highlights what we have already noted in this series of articles: the difference between the American School of Asteroid impacts that happen only at millions of years intervals and the British School which posits that showers of much smaller objects occur with great frequency in between those millions of years events.

The cheesiest part of this "docu-drama" was, of course, the depicted foibles of the humans experiencing the event. But, in a way, even those depictions were useful. The one guy who simply couldn't grasp the nature of the event, kept traveling "home" (which happened to be the site of the impact) even when it was clear that there was no home left. His emotions basically drove him to his own death.

Other people continued to act as if the world was still the same place and suffered thereby, though they learned to cope. What was clearly evident was that it was lack of knowledge about such events that was the chief problem for all of them.

During the course of the show, one of the experts made the remark "WHEN it happens," as though he - and the rest of them - knew for a fact that this was on the agenda for our near future. The very fact that so many scientists are working on these problems, including a large number of them studying the possible human reactions and behaviors and how to deal with masses of people, should warn us that there IS something they aren't telling the masses in the headlines of our daily newspapers, though certainly they are "testing" public reactions with shows such as Super Comet - After the Impact.

On my desk, before me, I have a book out of the more than 30 volumes and scores of papers on the topic of comet and asteroid impacts that I have collected in the course of this study. The title of this book is Hazards due to Comets and Asteroids edited by Tom Gehrels, with 120 contributing authors, published by the University of Arizona Press in 1994.

There is something in this book that I want to bring to your attention before we get on to our main catastrophe of the day: Mrs. O'Leary's Cometary Cow.

Comment: Continue to Part Seven: Tunguska, the Horns of the Moon and Evolution