Near-Earth objects and close calls

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Twice a day, at dusk and just before dawn, a faint layer of sodium and other metals begins sinking down through the atmosphere, about 90 miles high above the city of Boulder, Colorado. The movement was captured by one of the world’s most sensitive “lidar” instruments and reported Tuesday in the AGU journal Geophysical Research Letters.

The metals in those layers come originally from meteoroids blasting into Earth’s atmosphere, which bring an unknown amount of material to earth; and the regularly appearing layers promise to help researchers understand better how earth’s atmosphere interacts with space, ultimately supporting life.

“This is an important discovery because we have never seen these dusk/dawn features before, and because these metal layers affect many things.

The metals can fall into the ocean and act as fertilizer for ecosystems, the ionized metals can affect GPS radio signals….” said Xinzhao Chu, CIRES Fellow, CU Boulder professor of Aerospace Engineering Sciences, and lead author of the new assessment.

It is the first time that the metal layers have been seen so regularly at these extreme heights in the atmosphere. Such high-altitude metal layers were discovered by Chu’s group just 10 years ago above McMurdo, Antarctica, but there they occur more sporadically. Above Boulder, they’re consistent, daily, and synched with high-atmospheric “tidal winds” created by the sun’s periodic appearance. To understand those winds, the research team relied on data from NASA’s ICON satellite.

“This work was the very first use of the ICON tidal wind product. The product allowed Xinzhao’s team to calculate the flow of metal ions over Boulder. It’s a great example of how these tides seem to affect everything in space near Earth,” said Thomas Immel, Principal Investigator of the ICON Mission and a physicist at UC Berkeley's Space Sciences Laboratory.

“Consistent daily patterns seen in our Boulder observations tell us that there are unknown processes at play, a golden opportunity for atmospheric scientists to discover new phenomena and mechanisms,” said Jackson Jandreau who worked alongside Chu and Yingfei Chen in this study. Chen and Jandreau are both PhD students in Chu’s group.

The discovery also gives researchers a window into a crucial part of the atmosphere that is challenging to observe. It’s a complicated region where interactions between the sun, earth, our planet’s magnetic field, and other phenomena end up creating environmental conditions in which surface life can thrive, protected from the harsh space environment.

Intriguingly, Chu said, “There are metals in the atmospheres of other planetary bodies, such as Mars, and researchers look for Earth-like features on exoplanets as indicators for hospitable environments. Can these metal layers be one of these features?”

Her team used a powerful atmospheric lidar to detect and measure very small quantities of particles in the high atmosphere. Lidar is similar to radar: a signal is sent out towards a target and the target returns part of that signal which is collected by a receiver. In radar, the signal is radio waves; in lidar, it is photons from a laser. The return signal can be analyzed to learn about the targets hit and the space that the beam traveled through. Chu’s group developed the highly sensitive instrument with funding from the National Science Foundation.
The National Science Foundation funded both the Boulder and McMurdo lidar projects, grants AGS-1452351, AGS-2029162, and OPP-1443726.
Click to expand...
CIRES is a partnership of NOAA and CU Boulder.

Events in 2021 3092-2021​

We received 12 reports about a fireball seen over Bayern, Brandenburg, Hessen, Hlavní město Praha, Mecklenburg-Vorpommern, Nordrhein-Westfalen, Sachsen, Schleswig-Holstein and Thüringen on Sunday, May 30th 2021 around 22:55 UT.
Jun 1, 2021

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https://twitter.com/x/status/1399787962653630469
 
A green fireball was captured flying over Jacksonville, Florida.

Published on Jun 10, 2021 (0:43)

More here.

Bright fireball captured streaking in the sky above Spain.

Published on Jun 9, 2021 (1:31)

A newly-discovered asteroid will fly past Earth on June 13, 2021.

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Asteroid 2021 LO2 to fly past Earth at 0.5 LD

A newly-discovered asteroid designated 2021 LO2 will fly past Earth at a distance of 0.58 LD / 0.00148 AU (221 404 km / 137 574 miles) at 16:16 UTC on June 13, 2021. This the 64th known asteroid to…
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Posted by Teo Blašković on June 9, 2021

theskylive.com

Asteroid (NEO) 2021 LO2 | TheSkyLive.com

Discover all the most important facts and information about Asteroid (NEO) 2021 LO2 updated in real time
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A newly-discovered asteroid made a close approach to Earth on June 12, 2021.

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Asteroid 2021 LG5 flew past Earth at 0.41 LD

A newly-discovered asteroid designated 2021 LG5 flew past Earth at a distance of 0.41 LD / 0.00106 AU (158 573 km / 98 533 miles) at 22:19 UTC on June 12, 2021. This is the 65th known asteroid to fly…
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Posted by Teo Blašković on June 14, 2021

theskylive.com

Asteroid (NEO) 2021 LG5 | TheSkyLive.com

Discover all the most important facts and information about Asteroid (NEO) 2021 LG5 updated in real time
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Extremely eccentric minor planet to visit inner solar system this decade

Editor’s note: New details about this fascinating object have emerged since we wrote this article – here's the latest update.
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Extremely eccentric minor planet to visit inner solar system this decade​

The outskirts of our solar system is teeming with mysterious objects – and now one of them is heading our way. Astronomers have discovered a minor planet that’s about to make its closest pass to the Sun on its 600,000-year orbit.

The object in question is designated 2014 UN271, and it was only recently identified in data from the Dark Energy Survey captured between 2014 and 2018. Size estimates place it anywhere between 100 and 370 km (62 and 230 miles) wide. If it’s a comet, it’s quite a big one, especially for one coming from the outer solar system.

“[That] puts it on a similar scale, if not larger than, Sarabat's huge comet C/1729 P1, and almost undoubtedly the largest Oort Cloud object ever discovered – almost in dwarf planet territory!” says Sam Deen, a citizen astronomer, in a post on the Minor Planet Mailing List (MPML) forum.

But by far the most intriguing thing about 2014 UN271 is its orbit around the Sun. This thing is extremely eccentric, journeying between the inner solar system and the Oort cloud that marks the boundary of interstellar space over a period of 612,190 years.

And it turns out, astronomers are about to witness the closest pass of this incredible round trip. Currently, 2014 UN271 is about 22 Astronomical Units (AU) from the Sun (for reference, Earth is 1 AU from the Sun). That means it’s already closer than Neptune, at 29.7 AU. And it’s not stopping there – it’s already traveled 7 AU in the last seven years, and at its closest in 2031, it’s expected to pass within 10.9 AU of the Sun, almost reaching the orbit of Saturn.

Before then, it’s expected to develop the characteristic coma and tail of a comet, as icy material on its surface vaporizes from the heat of the Sun. This close pass would give astronomers an unprecedented close look at Oort cloud objects.

Unfortunately for us amateurs on the ground, don’t expect to see a show on the scale of Halley’s comet. While it’s too early to tell for sure, Deen calculates that 2014 UN271 would, at best, become about as bright as Pluto in the night sky, but more likely it’ll reach the brightness of Pluto’s moon Charon. Still, we’ll probably get some amazing shots from telescopes and observatories of the time.

After its close pass, 2014 UN271 will then hurtle back out into the inky blackness, on a several-hundred millennia return trip to the Oort cloud, and an incredible peak distance of almost 60,000 AU.
 
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