Comets

Asteroid fireball explodes over the Great Lakes

RT
Thu, 23 Jan 2020 16:32 UTC

The shattered remains of an asteroid now lie on the floor of one of North America's Great Lakes after travelling from beyond Mars to rain down on Earth in a blaze of fire.

Numerous eyewitnesses reported seeing the raging fireball streak across the sky on Tuesday night and experts calculate that it travelled nearly half a billion kilometers before coming to rest in its watery grave on the floor of Lake Huron.

Meteor scientist Peter Brown reported that the trajectory of the space rock's flight reveal that it travelled from the asteroid belt beyond Mars before hitting our planet.

The University of Western Ontario astronomer shared observatory footage on Twitter which captured the space visitor lighting up the night sky.

Yarrabubba is Earth's oldest known impact crater

Natalie Parletta
Cosmos Magazine
Tue, 21 Jan 2020 18:19 UTC

Evidence that the 70-kilometre wide Yarrabubba crater in outback Western Australia may be the Earth's oldest known meteorite impact structure has been presented in the journal Nature Communications.

Dated at 2.229 billion years, 200 million years older than the next known asteroid strike at Vredefort Dome in South Africa, the impact coincides with the end of a deep freeze known as early Snowball Earth and could have contributed to the ice thawing.

After this time period there are no rock records of large glacial deposits for 400 million years, says lead author Timmons Erickson from NASA Johnson Space Centre, Houston, US.

"Because of this, we were interested in seeing the role that an impact crater could have had during a time of global glaciations and whether an impact could release enough water vapour, a strong greenhouse gas, to significantly warm the planet."

Calculating the impact of the meteorite on an icy continent, they found that it could have sent half a trillion tonnes of water vapour into the atmosphere, thereby contributing to the global ice melt.

This highlights why the timing of "extraterrestrial bombardment" is important, as the authors write, so its effects on the Earth's environment can be understood.

To date, the historical impact record is fragmented, making it hard to understand how meteorites affect the planet - apart from the Chicxulub asteroid that triggered the last mass extinction and could explain the ocean's acidification.

Hurricanes, earthquakes and now a daytime meteor: Fireball blazes over Puerto Rico in broad daylight

Sputnik News
Sat, 18 Jan 2020 07:14 UTC

The US territory has been jolted by a series of powerful tremors since the beginning of this year. The island has also been recovering from the aftermath of Hurricane Maria that ravaged the territory in 2017.

Citizens of Puerto Rico have taken to social media platforms to share photos and videos of an unusual celestial phenomenon they witnessed on Friday afternoon.

In the media posts, a meteor-like fireball was seen swiftly flashing through a blue cloudless sky before disappearing moments later.

© NOAA
A bright meteor fireball disintegrated in the sky over Puerto Rico on January 17 at 4:30 p.m. EST time Friday. This was the moment it detonated in the atmosphere north of the island

Comment: A "rare" event, eh?...

10 Apr 2019: Bright meteor fireball filmed streaking through Puerto Rico skies
27 Jun 2019: Astronomers spotted a car-size asteroid just hours before it exploded over Puerto Rico
26 Jul 2017: Meteor fireball explodes over Cabo Rojo, Puerto Rico
03 Jun 2016: Bright meteor fireball visible from the entire island of Puerto Rico
03 Apr 2015: Big fireball over Puerto Rico
30 Apr 2014: Meteor fireball blazes over Puerto Rico

New comet discovered by Japanese astronomer

National Astronomical Observatory of Japan
Tue, 14 Jan 2020 00:58 UTC

A Japanese amateur astronomer has discovered a new comet.

Masayuki Iwamoto of Tokushima Prefecture discovered a new celestial object low in the eastern sky in the dawn on January 9, 2020 (JST) and communicated it to the National Astronomical Observatory of Japan's window for reports of new astronomical objects. On January 13 (UTC), this object was independently discovered by Gennady Borisov in Crimea. Through analysis of confirmation observations by other observers, this object was determined to be a comet.

Sun swallows newly discovered comet

Space Weather
Mon, 13 Jan 2020 01:00 UTC

Screenshot

A new comet was discovered yesterday, and it's already history. "The first comet discovery of the decade goes to... SOHO!" reports Karl Battams of the Naval Research Lab in Washington DC. During the early hours of Jan. 13th, coronagraphs onboard SOHO (the Solar and Heliospheric Observatory) spotted the tiny comet plunging into the sun, where it rapidly evaporated:

SOHO is the most prolific comet hunter in history. "It's actually quite unusual that it has taken 13 days for SOHO to find a comet," notes Battams. "This is the furthest we've gone into a new calendar year without a discovery since 2008. We're closing in on 3,900 comets discovered, and should comfortably pass 4,000 sometime this year!"

Comment: See also: Volcanoes, Earthquakes And The 3,600 Year Comet Cycle

Ancient impact crater discovered in Southern Laos

Mindy Weisberger
Live Science
Tue, 07 Jan 2020 15:03 UTC

© Shutterstock
An ancient impact scattered bits of glassy debris from Asia to Antarctica, but the resulting crater has long eluded detection.

About 790,000 years ago, a meteor slammed into Earth with such force that the explosion blanketed about 10% of the planet with shiny black lumps of rocky debris. Known as tektites, these glassy blobs of melted terrestrial rock were strewn from Indochina to eastern Antarctica and from the Indian Ocean to the western Pacific. For more than a century, scientists searched for evidence of the impact that created these pitted blobs.

But the crater's location eluded detection — until now.

Geochemical analysis and local gravity readings told researchers that the crater lay in southern Laos on the Bolaven Plateau; the ancient impact was concealed under a field of cooled volcanic lava spanning nearly 2,000 square miles (5,000 square kilometers), the scientists reported in a new study.

When a meteor hits Earth, terrestrial rocks at the impact site can liquefy from the intense heat and then cool into glassy tektites, according to the Jackson School Museum of Earth History at The University of Texas. Scientists can look at the abundance and locations of tektites to help locate an impact, even if the original crater is eroded or concealed, the study authors wrote.

In this case, there were plenty of tektites — so where was the crater?

Jupiter not a shield but is flinging comets toward Earth says new research

George Dvorsky
Gizmodo Australia
Tue, 07 Jan 2020 18:10 UTC

Some astronomers believe that Jupiter, instead of protecting Earth from dangerous comets and asteroids, is actively flinging objects into the inner solar system. New research now demonstrates this complex process in action.

A popular theory suggests Jupiter, with its tremendous mass, acts like a gigantic shield in space, sucking in or deflecting dangerous debris left over from the formation of the solar system. That makes sense, but the Jupiter Shield theory, as it's known, has been falling out of favour over the past two decades.

A leading critic of this theory, Kevin Grazier, formerly of the West Point U.S. Military Academy and NASA, has sought to debunk this idea for years. He has published several studies on the subject, including a 2008 paper titled, "Jupiter as a Sniper Rather Than a Shield." Indeed, with each successive paper, Grazier has increasingly demonstrated the ways in which Jupiter, instead of being our protector, is actually — though indirectly — a pernicious threat.

Grazier's latest foray into the subject involves a pair of companion papers, one published in the Astronomical Journal in 2018 and the other in the Monthly Notices of the Royal Astronomical Journal in 2019. The first paper takes a look at the complex ways in which objects in the outer solar system are affected by the Jovian planets, namely Jupiter, Saturn, Neptune, and Uranus, while the second paper looks at a specific family of icy bodies and how they're transformed by Jupiter into potentially deadly comets. Looking at the findings of the two papers, it seems the Jupiter Shield theory is in serious jeopardy.

"Actually, I wouldn't say that it's in jeopardy — I would say that it has been laid to rest." Grazier told Gizmodo in an email. "Our simulations show that Jupiter is just as likely to send comets at Earth as deflect them away, and we've seen that in the real solar system."

To be clear, this was a very good thing when the Earth was young, as comets and asteroids delivered the essential ingredients required for life. Today, however, these impacts are most certainly not good, as they could trigger mass extinctions similar to the one that extinguished non-avian dinosaurs some 66 million years ago.

New Comet C/2019 Y1 (ATLAS)

Ernesto Guido
Remanzacco Blogspot
Mon, 06 Jan 2020 16:54 UTC

CBET 4708 & MPEC 2020-A72, issued on 2020, January 05, announce the discovery of a comet (magnitude ~18) in the course of the "Asteroid Terrestrial-Impact Last Alert System" (ATLAS) search program, in images taken on 2019, Dec 16 with a 0.5-m reflector + CCD. The new comet has been designated C/2019 Y1 (ATLAS).

I performed follow-up measurements of this object while it was still on the PCCP webpage. Stacking of 28 unfiltered exposures, 30 seconds each, obtained remotely on 2019, December 20.15 from X02 Telescope Live network (El Sauce, Chile) through a 0.6-m f/6.5 reflector + CCD, shows that this object is a comet with a sharp central condensation and a diffuse irregular coma about 15 arcsec in diameter elongated in PA 90.

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

Asteroid to fly past Earth on Friday the 13th

Sputnik News
Thu, 12 Dec 2019 08:06 UTC

NASA has been monitoring an asteroid which maintains an orbit around various bodies in the solar system and consistently passes through Earth's orbit with the sun. 13 near-Earth objects in total are expected to fly past Earth in December of this year.

Earth is set to have a close encounter with an enormous asteroid which is set to fly nearby Earth on Friday at a speed of almost 18,000 miles an hour (more than 28,000 km/h), according to NASA.

The upcoming pass-by is estimated to happen on 8:25 am on 13 December, the unlucky Friday the 13th. The asteroid's orbit diagram indicates that the near-Earth approach will follow the rock's intersection with Earth's orbit.

According to the space agency's Center for Near-Earth Object Studies (CNEOS), the asteroid has an Earth-crossing orbit with the sun and will not approach from a diagonal or perpendicular direction and instead will flyby perpendicular to earth.

Near-Earth asteroid numbers grow

Barry Kelly
Cosmos Magazine
Tue, 10 Dec 2019 16:26 UTC

People using telescopes to stare at the night sky on December 20 or 26 might see a distant light traversing the heavens, but proclaiming it as a harbinger of a New Testament rerun would be unwise.

The European Space Agency's Near-Earth Object Coordination Centre advises that on neither night will the Star of Bethlehem be visible, but an asteroid very likely will be.

On December 20 a 300-metre-wide rock known as (216258) 2006 WH1 will whizz by. Six days later, (310442) 2000 CH59 - a bit bigger, at 400 metres - will do the same.

There is, however, no cause for alarm, given that both will remain at least 15 times the distance from the Earth to the Moon away. (Any relationship between either and newborn messiahs will thus be coincidental rather than causal.)

This is a rather more comforting route than those taken recently by five 10-metre-wide objects, and a single two-metre object, all of which, the ESA reports, came within half a lunar distance of Earth in the first 10 days of November.