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Tue, 18 May 2021
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Chicxulub simulations reveal trajectory of impact

Chicxulub Crater
© Gareth Collins/Imperial College London
Asymmetries of the Chicxulub crater.
The asteroid that most believe wiped out the dinosaurs struck at the deadliest possible angle, according to new analysis combining 3D numerical impact simulations and geophysical data from the site.

The 66-million-year-old Chicxulub crater in Mexico was formed by a steeply inclined impact of between 45 and 60 degrees to the horizontal, the researchers suggest, which maximised the amount of climate-changing gases thrust into the upper atmosphere.

Such a strike likely unleashed billions of tonnes of sulphur, blocking the Sun and triggering the nuclear winter that killed 75% of life on Earth.

The researchers - from Imperial College London (ICL), the University of Freiburg, Germany, and the University of Texas, US - say their models are the first fully 3D simulations to reproduce the whole dramatic event, from the initial impact to the crater formation.

Reproducing the final stage, in which the transient crater collapsed to form the final structure, allowed them to make the first comparison between 3D simulations and the present-day structure of the crater.

"Our simulations provide compelling evidence that the asteroid struck at a steep angle, perhaps 60 degrees above the horizon, and approached its target from the northeast," says ICL's Gareth Collins, lead author of a paper in the journal Nature Communications.

Comet 2

New Comet C/2020 K3 (Leonard)

CBET 4782 & MPEC 2020-K159, issued on 2020, May 25, announce the discovery of a comet (magnitude ~18) by G. J. Leonard on images taken on May 22 UT with the Catalina Sky Survey's 0.68-m Schmidt reflector. The new comet has been designated C/2020 K3 (Leonard).

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

Stacking of 20 unfiltered exposures, 55 seconds each, obtained remotely on 2020, May 23.4 from H06 (iTelescope network) through a 0.50-m f/6.8 reflector + CCD + f/4.5 focal reducer, shows that this object is a comet with a diffuse irregular coma about 15" in diameter

Our confirmation image (click here for a bigger version)
C/2020 K3 Leonard
© Remanzacco Blogspot


Active object in Jupiter's orbit is first of its kind seen by astronomers

asteroid 2019LD2
© JD Armstrong/IfA/LCOGT
Image of asteroid 2019LD2 taken on June 11th, 2019, using the Las Cumbres Observatory Global Telescope (LCOGT) NetworkÊ »s 1.0-meter telescope at Cerro Tololo, Chile.
We often think of asteroids and comets as distinct types of small bodies, but astronomers have discovered an increasing number of "crossovers." These objects initially appear to be asteroids, and later develop activity, such as tails, that are typical of comets.

Now, the University of Hawaiʻi's Asteroid Terrestrial-impact Last Alert System (ATLAS) has discovered the first known Jupiter Trojan asteroid to have sprouted a comet-like tail. ATLAS is a NASA-funded project using wide-field telescopes to rapidly scan the sky for asteroids that might pose an impact threat to Earth. But by searching most of the sky every two nights, ATLAS often finds other kinds of objects - objects that aren't dangerous, but are very interesting.

Early in June 2019, ATLAS reported what seemed to be a faint asteroid near the orbit of Jupiter. The Minor Planet Center designated the new discovery as 2019 LD2. Inspection of ATLAS images taken on June 10 by collaborators Alan Fitzsimmons and David Young at Queen's University Belfast revealed its probable cometary nature. Follow-up observations by the University of Hawaiʻi's J.D. Armstrong and his student Sidney Moss on June 11 and 13 using the Las Cumbres Observatory (LCO) global telescope network confirmed the cometary nature of this body.

Later, in July 2019, new ATLAS images caught 2019 LD2 again - now truly looking like a comet, with a faint tail made of dust or gas. The asteroid passed behind the Sun and was not observable from the Earth in late 2019 and early 2020, but upon its reappearance in the night sky in April of 2020, routine ATLAS observations confirmed that it still looks like a comet. These observations showed that 2019 LD2 has probably been continuously active for almost a year.

Fireball 2

The Tunguska explosion could have been caused by an asteroid that still orbits the Sun says new study

Tunguska Airburst
© Universe Today
On a cool Summer morning in 1908, a fireball appeared over Northern Siberia. Eyewitnesses described a column of blue light that moved across the sky, followed by a tremendous explosion. The explosion leveled trees across more than 2,000 square kilometers. The explosion is consistent with a large meteor strike, but to this day no evidence of a crater has been found. Now known as the Tunguska Event, its cause remains a mystery to this day.

One of the challenges in studying the Tunguska event is its remoteness. The region is sparsely populated, and the event only had a handful of witnesses. Scientific investigations of the event didn't occur until the 1920s. It was then that the impact region was mapped and early searches for an impact crater were undertaken. By the 1960s it was clear the event was similar to an airburst nuclear explosion, with an energy of about 5 Megatons.
Tunguska Fallen Trees
© Leonid Kulik expedition
Photograph of fallen trees seen by a 1929 expedition to the region.
Given what we know, the most likely cause is an airburst asteroid strike, where the asteroid explodes in the atmosphere, similar to the Chelyabinsk meteor strike in 2013. Given the size of the impact region, it's estimated that the original asteroid was nearly 70 meters across. This would explain why no large impact crater has been found.

But fragments of the Chelyabinsk were found soon after impact, and one would expect Tunguska fragments to have reached Earth. Despite several searches, nothing has been found. This has led some to look to other causes, such as a massive leak of natural gas, or even the explosion of an alien spacecraft. But a new study argues that there are no fragments because the asteroid didn't fragment after all. Instead, it glanced off Earth's atmosphere.

Fireball 5

Asteroid NY65 - Another close call to occur in June

Asteroid heading to Earth
NASA's Center for Near Earth Object Studies (CNEOs) is closely observing all asteroids approaching our planet within a distance of 0.05 astronomical units. In human terms, it may seem like nothing, but large space rocks can have a significant impact on Earth - even from a million-kilometres away.

The Apollo-class asteroid 441987, also dubbed 2010 NY65, will closely approach Earth on 24 June, according to NASA's tracking table.

The space rock is measured at between 140 and 310 metres, based on the way it reflects lights, and is estimated to be a small object in NASA's terms. However, it will approach our planet at a speed of 12.98 kilometre per second, coming as close as 0.02512 astronomical units to Earth.

Comet 2

New Comet P/2019 LM4 (Palomar)

CBET 4775 & MPEC 2020-J68, issued on 2020, May 14, announce that an apparently asteroidal object discovered on images taken at Palomar on 2019 June 4 and 7 with the 1.2-m f/2.4 Schmidt telescope (and given the minor-planet designation 2019 LM_4 when published on MPS 1001527, along with observations made elsewhere on June 8) has been re-discovered showing cometary appearance at two other observatories. The new comet has been designated P/2019 LM4 (Palomar).

According to the CBET 4775: B. Li reported the discovery by G. Zhaori of an extended object on images taken by L. F. Hu with the 1.04-m f/1.8 Schmidt telescope at the XuYi Station of Purple Mountain Observatory on May 11 UT in the course of the "Chinese Near Earth Object Survey" (discovery observations tabulated below). Before the object was posted on the Minor Planet Center's NEOCP webpage, it wasdiscovered independently in images obtained with the Pan-STARRS1 1.8-m Ritchey-Chretien reflector at Haleakala on May 12, with Y. Ramanjooloo (University of Hawaii) reporting that the full-width-at-half-maximum size was 3".6 compared to 1".2 for nearby stars. Observations were subsequently identified at the Minor Planet of yet another apparent independent discovery of the comet from 2020 May 9.5 at mag 16.4-17.0 with a 0.5-m f/2 Schmidt reflector at Haleakala, Hawaii, in the course of the "Asteroid Terrestrial- Impact Last Alert System" (ATLAS) search program, though it appears that the ATLAS team did not report it as a comet.

Comet P/2019 LM4Palomar
© Remanzacco Blogspot


New evidence reveals that giant meteorite impacts formed parts of the Moon's crust

Moon Impact
© Daniel D. Durda/FIAAA
An artist’s impression of how the early Moon was reshaped by an intense period of bombardment. A new study reveals that large impacts could have produced the range of lunar rocks sampled by the Apollo missions over 4.3 billion years ago.
Toronto, Canada - New research published today in the journal Nature Astronomy reveals a type of destructive event most often associated with disaster movies and dinosaur extinction may have also contributed to the formation of the Moon's surface.

A group of international scientists led by the Royal Ontario Museum has discovered that the formation of ancient rocks on the Moon may be directly linked to large-scale meteorite impacts.

The scientists conducted new research of a unique rock collected by NASA astronauts during the 1972 Apollo 17 mission to the Moon. They found it contains mineralogical evidence that it formed at incredibly high temperatures (in excess of 2300 °C/ 4300 °F) that can only be achieved by the melting of the outer layer of a planet in a large impact event. In the rock, the researchers discovered the former presence of cubic zirconia, a mineral phase often used as a substitute for diamond in jewellery.

The phase would only form in rocks heated to above 2300 °C, and though it has since reverted to a more stable phase (the mineral known as baddeleyite), the crystal retains distinctive evidence of a high-temperature structure. An interactive image of the complex crystal used in the study can be seen here using the .

Comet 2

New Comet C/2020 J1 (SONEAR)

CBET 4769 & MPEC 2020-J37, issued on 2020, May 04, announce the discovery of a comet (magnitude ~17) on images taken with a 0.28-m f/2.2 astrograph of the "Southern Observatory for Near Earth Research" (SONEAR) at Oliveira, Brazil, on May 1 . The new comet has been designated C/2020 J1 (SONEAR).

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

Stacking of 8 unfiltered exposures, 90 seconds each, obtained remotely on 2020, May 04.3 from X02 (Telescope Live, Chile) through a 0.6-m f/6.5 astrograph + CCD, shows that this object is a comet with a compact coma about 5" in diameter.

Our confirmation image (click here for a bigger version)
Comet C/2020 J1 SONEAR
© Remanzacco Blogspot

Comet 2

New Comet C/2020 H6 (ATLAS)

CBET 4768 & MPEC 2020-J23, issued on 2020, May 03, announce the discovery of a comet (magnitude ~18.5) on individual images from taken on Apr. 22 UT with a 0.5-m f/2 Schmidt reflector at Haleakala, Hawaii, in the course of the "Asteroid Terrestrial-Impact Last Alert System" (ATLAS) search program. The new comet has been designated C/2020 H6 (ATLAS).

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

Stacking of 10 unfiltered exposures, 120 seconds each, obtained remotely on 2020, April 28.4 from Q62 (iTelescope network) through a 0.50-m f/6.8 astrograph + CCD + focal reducer, shows that this object is a comet with a compact coma about 10" in diameter slightly elongated toward PA 330.

Our confirmation image (click on it for a bigger version)
C/2020 H6 ATLAS
© Remanzacco Blogspot


Infectious disease modeling study casts doubt on the Justinianic Plague's impact

Justinianic Plague’s Impact
Annapolis, MD — Many have claimed the Justinianic Plague (c. 541-750 CE) killed half of the population of Roman Empire. Now, historical research and mathematical modeling challenge the death rate and severity of this first plague pandemic.

Researchers Lauren White, PhD and Lee Mordechai, PhD, of the University of Maryland's National Socio-Environmental Synthesis Center, examined the impacts of the Justinianic Plague with mathematical modeling. Using modern plague research as their basis, the two developed novel mathematical models to re-examine primary sources from the time of the Justinianic Plague outbreak. From the modeling, they found that it was unlikely that any transmission route of the plague would have had both the mortality rate and duration described in the primary sources. Their findings appear in a paper titled "Modeling the Justinianic Plague: Comparing hypothesized transmission routes" in PLOS ONE.

"This is the first time, to our knowledge, that a robust mathematical modeling approach has been used to investigate the Justinianic Plague," said lead author Lauren White, PhD, a quantitative disease ecologist and postdoctoral fellow at SESYNC. "Given that there is very little quantitative information in the primary sources for the Justinianic Plague, this was an exciting opportunity to think creatively about how we could combine present-day knowledge of plague's etiology with descriptions from the historical texts."

White and Mordechai focused their efforts on the city of Constantinople, capital of the Roman Empire, which had a comparatively well-described outbreak in 542 CE. Some primary sources claim plague killed up to 300,000 people in the city, which had a population of some 500,000 people at the time. Other sources suggest the plague killed half the empire's population. Until recently, many scholars accepted this image of mass death. By comparing bubonic, pneumonic, and combined transmission routes, the authors showed that no single transmission route precisely mimicked the outbreak dynamics described in these primary sources.