Anonymous ID: 87b9d8 Dec. 20, 2023, 6:03 a.m. No.20104212   🗄️.is 🔗kun   >>4220

NASA Astronomy Picture of the Day

Dec 20, 2023

 

Ice Halos over Bavaria

 

What's causing those unusual sky arcs? Ice crystals. While crossing a field of fresh snow near Füssen, Bavaria, Germany, earlier this month, the photographer noticed that he had entered an ice fog. For suspended water to freeze into an ice fog requires quite cold temperatures, and indeed the air temperature on this day was measured at well below zero. The ice fog reflected light from the Sun setting behind St. Coleman Church. The result was one of the greatest spectacles the photographer has ever seen. First, the spots in the featured picture are not background stars but suspended ice and snow. Next, two prominent ice halos are visible: the 22-degree halo and the 46-degree halo. Multiple arcs are also visible, including, from top to bottom, antisolar (subsun), circumzenithal, Parry, tangent, and parhelic (horizontal). Finally, the balloon shaped curve connecting the top arc to the Sun is the rarest of all: it is the heliac arc, created by reflection from the sides of hexagonally shaped ice crystals suspended in a horizontal orientation.

 

https://apod.nasa.gov/apod/astropix.html?

Anonymous ID: 87b9d8 Dec. 20, 2023, 6:09 a.m. No.20104229   🗄️.is 🔗kun   >>4242 >>4346 >>4351

Senate confirms senior military leaders, including two four-star Space Force generals

December 20, 2023

 

The U.S. Senate on Dec. 19 voted to confirm eleven senior officers to become four-star generals and admirals, including two Space Force leaders, Gen. Michael Guetlein and Gen. Stephen Whiting.

 

The Senate vote came as the chamber delayed the holiday recess to work on a number of issues. The confirmations of Guetlein and Whiting, along with the promotions of hundreds of other officers, faced an unforeseen delay of nearly six months as a result of Sen. Tommy Tuberville (R-Ala.) blocking military promotions in protest of the Pentagon’s policy of reimbursing travel costs for troops seeking abortions.

 

The Senate on Dec. 5 confirmed 421 senior military promotions. However, that release did not cover 11 top generals and flag officers who had been nominated to receive a fourth star.

 

The hold created a period of uncertainty and operational constraints, the Pentagon said. After his Senate colleagues persistently pressured Tuberville to drop the protest, the blockade was lifted Dec. 19.

 

Both Guetlein and Whiting were nominated for their new posts in July.

 

Guetlein is poised to succeed now-retired Gen. David “DT” Thompson as vice chief of space operations of the U.S. Space Force.

 

Guetlein since 2019 served as commander of the Space Force’s acquisition arm, the Space Systems Command, based in Los Angeles. The new leader of Space Systems Command is Lt. Gen. Philip Garrant.

 

“Each of these leaders is highly qualified. They have dedicated their lives and careers to serving and defending our nation. They deserve our respect and gratitude, and I am pleased the Senate worked together to get them confirmed.”

 

Sen. Jack Reed (D-R.I.), chairman of the Senate Armed Services Committee

Gen. Stephen Whiting will assume the top post at U.S. Space Command, a Defense Department combatant command that oversees military operations in the space domain. Whiting since October 2020 served as commander of the Space Operations Command, a Space Force organization at Peterson Space Force Base, Colorado, that oversees the organization and equipping of Space Force units.

 

Whiting replaces U.S. Army Gen. James Dickinson as head of Space Command. He takes over amid a political fight over the permanent location of the command’s headquarters. The battle started when then-President Trump in his final days in office selected Huntsville, Alabama, as the headquarters’ location. The Biden administration ultimately reversed course and opted to keep Space Command in Colorado. This decision drew criticism from Alabama lawmakers who continue to challenge the decision.

 

https://spacenews.com/senate-confirms-senior-military-leaders-including-two-four-star-space-force-generals/

Anonymous ID: 87b9d8 Dec. 20, 2023, 6:33 a.m. No.20104320   🗄️.is 🔗kun   >>4332 >>4346

Bizarre Fast Radio Burst Exhibits a Unique Signal Never Seen Before

19 December 2023

 

A mystery signal from the depths of the cosmos has just been caught doing something we've never seen before.

 

In the midst of the emission of a repeating fast radio burst, scientists have detected a drop in the center frequency of the signals over time – a drop that sounds, they say, like a cosmic slide-whistle when slowed down and played on a xylophone.

 

It's unclear exactly what this unique drop in frequency means, yet – aside from the fact that fast radio bursts continue to be weird, and to defy easy explanation.

 

"This work is exciting because it provides both confirmation of known FRB properties and the discovery of some new ones," says radio astronomer Sofia Sheikh of the SETI Institute.

 

"We're narrowing down the source of FRBs, for example, to extreme objects such as magnetars, but no existing model can explain all of the properties that have been observed so far."

 

Fast radio bursts, or FRBs, are very strange, but very nifty. As the name suggests, they're bursts of radio emission that are very fast: each burst lasts just a few microseconds to seconds.

 

They're really powerful, discharging in that short space of time as much energy as 500 million Suns. And they're a bit tricky to catch: most FRBs have only been caught flaring once, a strange, unpredictable spike in radio survey data.

 

That unpredictability and failure to repeat has made them difficult to study (although not impossible – great strides have been made in tracing and analyzing the one-off signals).

 

But a handful of FRB sources do something a bit different: they flare again and again, a strange staccato spatter of signals that sometimes follows a pattern, and sometimes doesn't.

 

These repeat sources are an opportunity to trace the source of an FRB with high precision, but also to plan for, and study in detail, signals from a single source.

 

This is what Sheikh and her colleagues have done, homing in on a source known as FRB 20220912A, coming from another galaxy around a billion light-years away.

 

They analyzed 541 hours of observation data from the Allen Telescope Array, and extracted a total of 35 bursts, with an average duration of 1.2 milliseconds.

 

They then stretched out these signals, and studied how the emission from the source changes over time. There were some characteristics that the FRB 20220912A bursts shared in common with other FRBs, such as a downward frequency drift, a link between the signal bandwidth and center frequency, and changes in burst duration over time.

 

The researchers looked for patterns in the propagation of the bursts, and found none. FRB 20220912A appears to be one of the repeaters that does so at random. But the signals it spits out are pretty interesting.

 

Over the two months the bursts were scattered, the researchers also noticed a drop in the center frequency of the bursts. Here's what that sounds like, when the data is translated into musical notes on a xylophone.

 

What we don't know is why this drop occurs, but it could be information that helps scientists figure out where FRBs are coming from.

 

Evidence suggests that at least some FRBs are emitted by magnetars, but we don't yet know if that's the case for all FRBs, or if there's a different magnetar behavior behind different types of FRBs. Although we're getting closer to answers, we're far from a comprehensive description of how these signals are created.

 

Finding strange behaviors brings us closer, even when we can't quite explain them yet. None of the behavior noted in FRB 20220912A favor or rule out any models of FRB creation and propagation, but it does provide a benchmark against which future observations can be compared, the researchers say.

 

The discovery also highlights the importance of instruments such as the Allen Telescope Array, which has the ability to record a wide range of bandwidths as it studies the sky. This reveals behaviors that might not be picked up by instruments that have a narrower focus.

 

"More observations of the source," the researchers write, "especially at higher frequencies with instruments like the ATA, will help to differentiate between the various classes of FRB progenitor models."

 

https://www.sciencealert.com/bizarre-fast-radio-burst-exhibits-a-unique-signal-never-seen-before