Comets

Comets cause meteor showers on Earth

SETI Institute
Thu, 20 May 2021 19:32 UTC

Comets that circle the Sun in very elongated orbits spread their debris so thin along their orbit or eject it out of the solar system altogether that their meteor showers are hard to detect. From a new meteor shower survey published in the journal Icarus, researchers now report that they can detect showers from the debris in the path of comets that pass close to Earth orbit and are known to return as infrequent as once every 4,000 years.

"This creates a situational awareness for potentially hazardous comets that were last near-Earth orbit as far back as 2,000 BC," said meteor astronomer and lead author Peter Jenniskens of the SETI Institute.

Jenniskens is the lead of the Cameras for Allsky Meteor Surveillance (CAMS) project, which observes and triangulates the visible meteors in the night sky using low- light video security cameras to measure their trajectory and orbit. There are CAMS networks now in nine countries, led by co-authors on the paper.

In recent years, new networks in Australia, Chile and Namibia significantly increased the number of triangulated meteors. The addition of these networks resulted in a better and more complete picture of the meteor showers in the night sky.

"Until recently, we only knew five long-period comets to be parent bodies to one of our meteor showers," said Jenniskens, "but now we identified nine more, and perhaps as many as 15."

Overview of the Younger Dryas impact hypothesis debate

George Howard
Cosmic Tusk
Fri, 14 May 2021 19:16 UTC

© Earth-Science journal, Earth-Science ReviewsLocation map showing 53 YD boundary (black mat) sites (reproduced from Pino et al. (2019) under the terms of the CCA 4.0 International License). Orange dots represent 28 sites with peaks in both platinum and other impact proxies such as high-temperature iron-rich microspherules. Red dots represent 24 sites with impact proxies but lacking platinum measurements. The yellow dot indicates the Pilauco site, Chile, described in detail in Pino et al. (2019). A new site in South Africa, Wonderkrater, has been identified since this map was first published (Thackeray et al., 2019).

Indefatigable genius and digital friend of the Tusk, Dr. Martin Sweatman, authored a surprise blockbuster this week. Below is a peer-reviewed and fully accepted pre-online synthesis overview of the Younger Dryas Impact controversy since the very first paper in 2007. 'The Younger Dryas impact hypothesis: review of the impact evidence' concludes — in perhaps the world's most appropriate and respected scientific journal — that based on the published evidence, our modern world is indeed birthed of a horrendous global catastrophe ~12,881 years ago. It is a lengthy, detailed, fair and lucid tour-de-force in support of The Event based on Martin's reading of the entire debate.

Martin is an example to the Tusk of how many, many people there are on earth. You have to have 8+ billion humans in order to have enough brain matter and determination on the end of the bell curve to find a just one single, well-qualified, unbiased, poly-curious scientist, so determined to find the truth that they will to read every last word — and then write every last word — well.

Geologists identify rare meteorite impact site in Dakota County

Cathy Wurzer
Minnesota Public Radio News
Thu, 13 May 2021 23:54 UTC

An area around Inver Grove Heights, Minn., is the site of an ancient meteorite crash, according to recent analysis by the Minnesota Geological Survey.

The discovery came as scientists were updating geologic maps of Dakota County. They identified anomalies in the rock record — certain layers appeared out of order or irregularly sized. This led to further examination and the identification of small grains of shocked quartz, which is known to be produced only by the extreme shock and compression of a meteorite impact or nuclear explosion.

"It's really exciting and new," geologist Julia Steenberg told MPR News host Cathy Wurzer. Steenberg and her colleagues are hoping to do more research to better understand the age of the impact and the size of the meteorite involved.

Globally, known meteorite impact sites are exceptionally rare. This is the first identified in Minnesota and one of fewer than 200 in the world.

New Comet C/2021 E3 (ZTF)

Ernesto Guido
Remanzacco Blogspot
Thu, 06 May 2021 17:28 UTC

CBET xxxx & MPEC 2021-J71 , issued on 2021, May 06, announce the discovery of an apparently asteroidal object (magnitude ~19.5) on CCD images taken on March 09.5 UT with the 1.2-m Schmidt telescope at Palomar in the course of the "Zwicky Transient Facility" (ZTF) search program. This object has been found to show cometary appearance by CCD astrometrists elsewhere. The new comet has been designated C/2021 E3 (ZTF).

Stacking of 14 unfiltered exposures, 120 seconds each, obtained remotely on 2021, March 19.2 from Z08 (Telescope Live, Oria) through a 0.7 m f/8 Ritchey Chretien + CCD, shows that this object is a comet with a compact coma about 7" in diameter (Observers E. Guido, M. Rocchetto, E. Bryssinck, M. Fulle, G. Milani, C. Nassef, G. Savini, A. Valvasori).

Our confirmation image (click on it for a bigger version; made with TYCHO software by D. Parrott)

Ancient impactor that created the Moon may still be inside Earth

Anna Funk
Astronomy
Wed, 14 Apr 2021 19:02 UTC

Researchers are fairly certain that we gained our favorite satellite, the Moon, after a planet, Theia, collided with the proto-Earth 4.5 billion years ago. What's not certain are the details surrounding Theia's fate. Was it a hit-and-run, or did the mantles of the two planets merge?

Qian Yuan, Earth scientist at Arizona State University, and his colleagues recently suggested a new line of evidence to support the latter hypothesis, suggesting that Theia not only merged with Earth, but we might know right where the remnants of its mantle reside in Earth.

Giant impact hypothesis

"Compared to the Moon, there is much less [known] about Theia," says Yuan. "The Moon is there. You have samples. People have been there ... few people care too much about the impactor."

A lot of the work around the giant impact hypothesis involves comparing isotopes found on the Moon with those found on Earth. Their similarities in composition suggest that the Moon is made of a hunk of ancient Earth, meaning something like a giant impact knocked it off our Pale Blue Dot.

Original models estimated that the impactor, Theia, was about the size of Mars (half the size of Earth today). Though, some recent studies suggest it might've been more like four times the size of Mars, or roughly the size of the proto-Earth. Either way, most researchers agree that the core — the densest part — of Theia merged with the core of Earth incredibly quickly after the impact, in a matter of hours.

New Comet C/2019 U5 (PANSTARRS)

Ernesto Guido
Remanzacco Blogspot
Wed, 07 Apr 2021 23:09 UTC

CBET 4953 & MPEC 2021-G80, issued on 2021, April 07, announce that an apparently asteroidal object (magnitude ~21.0) discovered on CCD images obtained with the F51 Pan-STARRS 1 survey's 1.8m Ritchey-Chretien on 2019, October 22.22 and designated A/2019 U5 (cf. MPEC 2019-V10) has been found to show cometary appearance by other CCD observers over the past half year. The new comet has been designated C/2019 U5 (PANSTARRS).

Stacking of 20 unfiltered exposures, 120 seconds each, obtained remotely on 2021, April 02.1 from Z08 (Telescope Live, Oria) through a 0.7 m f/8 Ritchey Chretien + CCD, shows that this object is a comet with a compact coma about 15" arcsec in diameter (Observers E. Guido, M. Rocchetto, E. Bryssinck, M. Fulle, G. Milani, C. Nassef, G. Savini, A. Valvasori).

Our confirmation image (click on it for a bigger version; made with TYCHO software by D. Parrott)

New Comet C/2020 F7 (Lemmon)

Ernesto Guido
Remanzacco Blogspot
Fri, 26 Mar 2021 18:16 UTC

CBET 4949 & MPEC 2021-F110, issued on 2021, March 25, announce that an apparently asteroidal object (magnitude ~21.0) discovered on CCD images obtained with the Mt. Lemmon Survey's 1.5-m reflector on 2020 Mar. 22 and designated A/2020 F7 (cf. MPEC 2020-G78) has been found to show cometary appearance by numerous other CCD observers over the past half year. The new comet has been designated C/2020 F7 (Lemmon).

Stacking of 19 unfiltered exposures, 120 seconds each, obtained remotely on 2021, March 23.9 from Z08 (Telescope Live, Oria) through a 0.7 m f/8 Ritchey Chretien + CCD, shows that this object is a comet with a compact coma about 15" in diameter elongated toward PA 50. (Observers E. Guido, M. Rocchetto, E. Bryssinck, M. Fulle, G. Milani, C. Nassef, G. Savini).

Our confirmation image (click on it for a bigger version; made with TYCHO software by D. Parrott)

New Comet C/2021 D2 (ZTF)

Ernesto Guido
Remanzacco Blogspot
Tue, 23 Mar 2021 18:12 UTC

CBET 4948 & MPEC 2021-F67, issued on 2021, March 22, announce the discovery of an apparently asteroidal object (magnitude ~19.5) on CCD images taken on Feb. 19.5 UT & Mar. 09-5 with the 1.2-m Schmidt telescope at Palomar in the course of the "Zwicky Transient Facility" (ZTF) search program (the object was reported twice by the ZTF survey team as two different objects) . This object has been found to show cometary appearance by CCD astrometrists elsewhere. The new comet has been designated C/2021 D2 (ZTF).

Stacking of 20 unfiltered exposures, 60 seconds each, obtained remotely on 2021, March 15.2 from I89 (iTelescope, Nerpio, Spain) through a 0.32-m f/8.0 reflector + CCD, shows that this object is a comet with a diffuse coma about 8" arcsec in diameter (Observers A. Valvasori, E. Guido).

Stacking of 12 unfiltered exposures, 90 seconds each, obtained remotely on 2021, March 18.2 from Z08 (Telescope Live, Oria) through a 0.7 m f/8 Ritchey Chretien + CCD, shows that this object is a comet with a diffuse coma about 10" in diameter (possibly elongated toward PA 140). (Observers E. Guido, M. Rocchetto, E. Bryssinck, M. Fulle, G. Milani, C. Nassef, G. Savini).

Our confirmation image (click on it for a bigger version; made with TYCHO software by D. Parrott)

Karma family of asteroids potential source of near-Earth asteroids

Theo Nicitopoulos
Sky & Telescope
Tue, 16 Mar 2021 16:27 UTC

New simulations have identified the Karma family of asteroids in the main belt as a potential source of near-Earth asteroids.

When asteroids in the main belt of the solar system collide, the fragments come back together to form smaller rubble-pile bodies that orbit the Sun as a "family." Under the right conditions, some of those family members can end up in near-Earth space.

In a study published in Monthly Notices of the Royal Astronomical Society, researchers simulated the orbital evolution of asteroids in the Karma family, starting with the initial family-creating impact. The results suggest that over the family's lifetime, 350 members have transferred close to Earth's orbit — and around 10 might currently be in near-Earth space right now.

New Comet C/2021 C4 (ATLAS)

Ernesto Guido
Remanzacco Blogspot
Mon, 01 Mar 2021 17:38 UTC

CBET 4937 & MPEC 2021-D113, issued on 2021, February 26, announce the discovery of an apparently asteroidal object (magnitude ~19) on CCD images taken on Feb. 12.6 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. This object has been found to show cometary appearance by CCD astrometrists elsewhere after the object was posted on the Minor Planet Center's PCCP webpage due to its orbit. The new comet has been designated C/2021 C4 (ATLAS).

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

Stacking of 5 unfiltered exposures, 90 seconds each, obtained remotely on 2021, February 22.2 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 8" arcsecond in diameter. (Observers E. Guido, M. Rocchetto, E. Bryssinck, M. Fulle, G. Milani, C. Nassef, G. Savini, A. Valvasori).

Our confirmation image (click on it for a bigger version; made with TYCHO software by D. Parrott):