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Sat, 19 Aug 2017
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Comets


Comet 2

Large comets more common than previously thought

© NASA
An artist’s rendering of the NASA’s WISE mission, renamed NEOWISE in 2013, observing comets and other deep space objects.
Data from NASA's Wide-field Infrared Survey Explorer (WISE) mission has shown that large, distant comets are more common than previously thought. This is according to research published in the Astronomical Journal. These "long-period comets" originate from the distant Oort Cloud, and the information provided by the NASA's spacecraft is contributing to a better understanding of how common these icy worldlets might be.

While most people are likely familiar with icy objects such famous comets as Halley and Shoemaker-Levy 9, the latter of which broke up and impacted the gas giant Jupiter in July 1994. These, along with nearly all of those most of us have heard about (or seen) are from the family of "short-period comets". Short-period refers to the length and distance of the period, or the time it takes to make one full orbit, of the object.

Short-period comets take less than 200 years to make a full orbit around the Sun. These are generally separated into two families: Jupiter-family comets and highly inclined long-period comets. Jupiter-family comets, of which Shoemaker-Levy 9 was one, have orbital periods of less than 20 years. Long-period comets, like Halley's Comet, have orbital periods between 20 and 200 years in length.

Fireball

Asteroid Florence to sweep past Earth on September 1st

Named for Florence Nightingale, asteroid 3122 Florence is the biggest near-Earth object to pass this close since this category of objects was discovered over a century ago! It might be visible in binoculars.
© Stellarium
Asteroid 3122 Florence – named for the founder of modern nursing – on August 27 at 11:50 pm CDT as seen from central U.S. Illustration by Eddie Irizarry using Stellarium.
The next attraction coming up in our skies after the spectacular total solar eclipse of August 21 might be an asteroid big enough to be seen in small telescopes, and maybe even in binoculars, as a small, very slow-moving "star." Asteroid 1981 ET3 - also known as 3122 Florence - is a huge space rock at least 2.7 miles (4.35 km) in diameter. According to Paul Chodas at the Center for Near Earth Object Studies:
Florence is the largest asteroid to pass this close to our planet since the first near-Earth asteroid was discovered over a century ago.
Asteroid 3122 Florence will safely pass by our planet on September 1, 2017 at over 18 times the Earth-moon distance. The asteroid will not be visible to the unaided eye. It will, however, become visible in small amateur telescopes by late August, in the course of what will become the closest encounter to Earth by this asteroid since 1890.

Book 2

Of Flash Frozen Mammoths and Cosmic Catastrophes

For years I've been fascinated by what could be considered as one of the greatest mysteries of our planet: the demise of the woolly mammoths. Try to imagine the barely imaginable: millions of giant mammoths inexplicably flash-frozen overnight.

This is a fascinating event for several reasons. First, flash-freezing is a very peculiar process that does not really occur on our planet. Also, given the death circumstances, the magnitude and power involved to virtually wipe out the whole mammoth genus is truly astounding.


Mammoth painting in Rouffignac cave
But maybe the most fascinating aspect of this event is that it occurred just 13,000 years ago when the human race was already widely established on planet Earth. For comparison, the upper paleolithic cave paintings found in Southern France (Lascaux, Chauvet, Rouffignac,...) were made 17,000 to 13,000 years ago.

This event challenges our uniformitarian vision of history where the progress of life on our planet is a linear process, increasing day after day, undisturbed by any major external setback. Therefore such an event casts a different light on our human condition and the pervasive delusion that human beings are some kind of all-mighty creatures that are above natural laws, including those that govern major catastrophes.

It is a fascinating and puzzling topic because the numerous theories that have been proposed over the last two centuries to explain the demise of the woolly mammoths - such as them being caught in frozen rivers, victims of over-hunting, covered by hail storms, buried in mudslides, fallen in ice crevasses, caught by the ice age - are not sufficient to fully explain this mass extinction.

So, in the following article, I will try to provide explanations about how and why millions of woolly mammoths ended up flash-frozen overnight.

Cassiopaea

Signs of the times - New comet, Nova in Scutum constellation and Supernova in Pisces!

© Rolando Ligustri
New Comet ASASSN1 (C/2017 O1) already glows aqua from carbon-laced gases. The comet is currently visible in the pre-dawn sky through modest-sized telescopes.
It feels like the FedEx guy just pulled up and dropped off a truckload of astronomical goodies. News arrived in my e-mail Monday about a new comet discovered by the All-Sky Automated Survey for Supernovae (ASAS-SN).Founding member Benjamin Shappee and team have 498 bright supernovae and numerous other transient sources to their credit, but this is the group's first comet discovery, ASASSN1 (C/2017 O1).

The 15th-magnitude object was caught before dawn on July 19th in the constellation Cetus using data from the quadruple 14-cm "Cassius" telescope on Cerro Tololo, Chile. Don't be put off by that magnitude. The comet has brightened quickly in the past few days; visual observers are now reporting it at around magnitude +10 with a large (7′), weakly condensed coma. Chris Wyatt of Australia relates that a Swan band filter does a great job enhancing the apparent brightness and contrast of the coma, a sign this is a "gassy" comet.
© Stellarium
This wide-view map shows Comet ASASSN1's location at the Cetus–Eridanus border south of Alpha (α) Ceti (Menkar) on July 26th.
Assuming the orbit remains close to the current calculation, Comet ASASSN1 will move northeast across Cetus and Taurus this summer and fall, slowly brightening as it approaches perihelion on October 14th in Perseus. It comes closest to the Earth four nights later, missing the planet by a cool 67 million miles. In a fun twist, ASASSN1 will slow down and spend the entire month of December and much of January within a few degrees of the North Star!

Comet

Comets from oort cloud more common threat to Earth than previously thought

© NASA/JPL-Caltech
"Comets travel much faster than asteroids, and some of them are very big," said Amy Mainzer, co-author based at NASA's Jet Propulsion Laboratory, Pasadena, California, and principal investigator of the NEOWISE mission. "Studies like this will help us define what kind of hazard long-period comets may pose."

"The number of comets speaks to the amount of material left over from the solar system's formation," said James Bauer, lead author of the study and now a research professor at the University of Maryland, College Park. "We now know that there are more relatively large chunks of ancient material coming from the Oort Cloud than we thought."

Comets that take more than 200 years to make one revolution around the Sun are notoriously difficult to study. Because they spend most of their time far from our area of the solar system, many "long-period comets" will never approach the Sun in a person's lifetime. In fact, those that travel inward from the Oort Cloud -- a group of icy bodies beginning roughly 186 billion miles (300 billion kilometers) away from the Sun -- can have periods of thousands or even millions of years.

This illustration shows how scientists used data from NASA's WISE spacecraft to determine the nucleus sizes of comets. They subtracted a model of how dust and gas behave in comets in order to obtain the core size.

Comet 2

New Comet: C/2017 O1

CBET nr. 4414, issued on 2017, July 24, announces the discovery of a comet (magnitude ~15.3) in the course of the "All-Sky Automated Survey for Supernovae" (ASASSN) program, from images taken with the 14-cm "Cassius" survey telescope at Cerro Tololo on July 19.32 UT. The new comet has been designated C/2017 O1.

I performed follow-up measurements of this object, while it was still on the neocp. Stacking of 10 unfiltered exposures, 60 seconds each, obtained remotely on 2017, July 23.7 from Q62 (iTelescope network) through 0.50-m f/6.8 astrograph + CCD + f/4.5 focal reducer, shows that this object is a comet with a sharp central condensation surrounded by diffuse coma about 3 arcmins in diameter.

My confirmation image (click on it for a bigger version)
© Remanzacco Blogspot
Below you can see the discovery image by ASASSN survey

Fireball

Loud boom over North Carolina caused by meteor fireball

© American Meteor Society
The American Meteor Society received about 50 reports about a fireball seen over the Southeast late Thursday night. This map shows places that reported seeing the fireball.
The American Meteor Society received about 50 reports about a fireball seen over the Southeast late Thursday night.

AMS said the fireball was seen shortly after 10 p.m. in North Carolina, South Carolina, Alabama, Tennessee, Georgia, Virginia and Kentucky and Tennessee.

Because there was nothing other than the fireball reported in the area at the time of the boom, speculation is that the boom was likely a meteor breaking up in the atmosphere.

Click here to see the AMS report.

Comet 2

Bizarro comet challenging researchers

© Florida Space Institute at UCF
llustration of Echeclus.
Scientists pursue research through observation, experimentation and modeling. They strive for all of these pieces to fit together, but sometimes finding the unexpected is even more exciting. That's what happened to University of Central Florida's astrophysicist Gal Sarid, who studies comets, asteroids and planetary formation and earlier this year was part of a team that published a study focused on the comet 174P/Echeclus. It didn't behave the way the team was expecting.

"This is another clue that Echeclus is a bizarre solar system object," said University of South Florida physics research Professor Maria Womack, who leads the team.

Comets streak across the sky and as they get closer to the sun look like bright fuzz balls with extended luminous trails in their wake. However, comets are actually bulky spheres of mixed ice and rock, many of them also rich in other frozen volatile compounds, such as carbon monoxide, carbon dioxide, hydrogen cyanide and methanol.

Comets heat up as they get closer to the sun, losing their icy layers by sublimation and producing emission jets of water vapor, other gases and dust expelled from the comet nucleus, Sarid said. Once they move away from the sun, they cool off again. But some comets start showing emission activity while still very far from the sun, where heating is low.

Fireball 4

Possible fast moving meteor fireball sighted over South Australia

© Herald Sun, Australia
Meteor Shower Adorns Southern Lights Over Tasmania.
A bright "fast-moving" light with a green trail across the sky Friday night has captured the imaginations of at least a few locals who are this morning trying to get to the bottom of what it is they saw - or think they saw.

Advertiser.com.au has received and read a smattering of reports about the strange light, which one expert says could have been a meteor or space junk re-entering the earth's atmosphere.

A Reddit user reported seeing "what I can only guess was a meteor" pass over Henley Beach.

"Saw it from the city, fast moving bright light, green trail, bright flash."

Another Reddit user responded that the same phenomenon was witnessed by "a lot of people" on the Eyre Peninsula.

Salisbury East man Bradley Cousins said he was driving home from work in Tanunda around midnight when he looked up at the moon because it "looked strange".

Archaeology

Tree rings pinpoint eruption of Iceland's Katla volcano to half a century before human settlement

An international group of researchers has dated a large volcanic eruption in Iceland to within a few months. The eruption, which is the oldest volcanic eruption to be precisely dated at high northern latitudes, occurred shortly before the first permanent human settlements were established, when parts of the now mostly treeless island were still covered with forest.

The team, which included volcanologists, climatologists, geographers and historians among others, used a combination of scientific and historical evidence to pinpoint the eruption date of the Katla volcano between late 822 CE and early 823 CE, decades before the earliest settlers arrived. Their results are reported in the journal Geology.

In a similar way to how fossils can be used to understand the development and evolution of life on Earth, different types of environmental evidence can be used to understand what the Earth's climate was like in the past and why. The 'fingerprints' contained in tree rings and ice cores help scientists to estimate past climatic conditions and extend our understanding of the interaction between humans and the environment hundreds and thousands of years back in time.