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Thu, 06 May 2021
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Strange Skies

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First documented case of rare red sprites in New Zealand

Rare red sprites captured in Kāpiti
© Brendan Gully
Rare red sprites captured in Kāpiti.

A Kāpiti photographer has captured a rare weather event, so rare it's the first time Metservice has documented the case.

Brendan Gully captured red sprites from the Kāpiti Coast last week during a thunderstorm capturing them not once, but three times.

"I was really stoked to have finally captured them in New Zealand and it was a bit of a relief too," Brendan said.

A landscape photographer who specialises in storms and likes to capture natural phenomena and scenes that are fleeting, Brendan has been chasing storms and red sprites for a few years.

"I started photography in 2015 and it was the storm-chasing that led me to get my first camera.

"I've had a decent number of attempts at them in the past, but just not had the right luck on the day."

Red sprites are rare bolts of red lightning that are rarely seen from the ground due to their high altitude.

They form between 50-90km above the Earth and only last a few milliseconds.

Comment: With the surge in sightings of rare or novel atmospheric phenomena in recent years it seems the electrical nature of our weather and changing atmosphere is becoming more apparent:


Black auroras captured over Scotland

Aurora Borealis on April 18, 2021 @ Hopeman, Moray, Scotland
© Alan C Tough
Aurora Borealis on April 18, 2021 @ Hopeman, Moray, Scotland
Red. Green. Purple. These are the colors we usually see during any display of auroras. On April 18th, Alan C. Tough of Hopeman, Moray, Scotland saw something else. "Black," he says. In the photo below, "note the dark vertical strip above the green band, which is devoid of any normal auroral colour."

Black auroras have been seen before. They are dark rings or black blobs that sometimes appear in an otherwise ordinary expanse of auroral light. Some researchers call them "anti-auroras." The black auroras in Tough's photo are circled here.

Ordinary auroras are caused by electrons raining down from space, hitting Earth's upper atmosphere and making the air glow. Black auroras are the opposite. Instead of electrons raining down, electrons are propelled upward, back into space. This diagram shows what happens:


AG Carinae about to go supernova?

AG Carinae
Spectacular image of the luminous blue variable star AG Carinae released by Hubble for it’s 31st launch anniversary.
Astrophotography is one of the most gratifying parts of space exploration, and there's nothing better at it than Hubble. Recently, it celebrated the 31st anniversary of its launch by taking a spectacular image of one of the most impressive stars in the sky - AG Carinae. In the not too distant future, Hubble, or a successor, might be able to capture an even more spectacular display from the star when it goes supernova.

AG Carinae, located appropriately in the constellation Carina, is one of the most luminous stars in the sky, though its apparent brightness on Earth is somewhat diminished give its 20,000 light year distance from Earth. The star is famous for a number of reasons, including that it is one of only 50 known luminous blue variable stars.

Luminous blue variables are extremely short lived and violent, barely balancing between exploding into a supernova and collapsing under its own weight into a black hole. As part of their life cycle, they occasionally emit a spectacular outburst that creates a kind of glowing shell around them, as can be seen in the Hubble image of AG Carinae.

Outbursts like the one in the picture only happen once or twice in a luminous blue variable's lifetime. They occur when radiation pressure from the interior of the star expands it out to such an immense size that it pushes material out of itself, then collapses back into a more stable state for potentially millions of years.


Rare V-shaped sun halo captured over Florida

Sunvex Parry arc taken on April 23, 2021 @ Viera, Florida, USA
© Dan Gore
Sunvex Parry arc taken on April 23, 2021 @ Viera, Florida, USA
You don't see this every day, especially not in Florida. On April 23rd, a pair of glowing V's appeared above the setting sun, both caused by ice crystals in the air. Dan Gore photographed them from Viera, FL.

"They lingered for about 5 minutes, then they were gone," says Gore. "It was a beautiful sight."

These are sun halos, one rare and one common. The lower 'V' is a common upper tangent arc created by sunlight shining through pencil-shaped ice crystals. The upper 'V' is a rare Parry arc created by similar kinds of ice crystals, but... To make the Parry arc, the crystals had to be horizontal, not rotate, and have two faces horizontal, too. It sounds improbable, and it is. That's why the Parry arc is so rare.

What's all this ice doing in Florida air? The crystals were located in cirrus clouds 5 to 10 km above the ground where the air is always freezing--even in Florida. Parry arcs prefer cold climates, but they can appear in the Sunshine State, too.

Comment: It is likely that atmospheric dust loading from increased comet and volcanic activity is contributing to the 'strange skies' we are witnessing, the cooling effect of which causes ice crystals to form. See also:

Arrow Up

Largest flare from sun's nearest neighbor breaks records

Proxima Centauri
© NRAO/S. Dagnello
Artist's conception of a violent flare erupting from the star Proxima Centauri.
Scientists have spotted the largest flare ever recorded from the sun's nearest neighbor, the star Proxima Centauri.

The research, which appears today in The Astrophysical Journal Letters, was led by CU Boulder and could help to shape the hunt for life beyond Earth's solar system.

CU Boulder astrophysicist Meredith MacGregor explained that Proxima Centauri is a small but mighty star. It sits just four light-years or more than 20 trillion miles from our own sun and hosts at least two planets, one of which may look something like Earth. It's also a "red dwarf," the name for a class of stars that are unusually petite and dim.

Proxima Centauri has roughly one-eighth the mass of our own sun. But don't let that fool you.

In their new study, MacGregor and her colleagues observed Proxima Centauri for 40 hours using nine telescopes on the ground and in space. In the process, they got a surprise: Proxima Centauri ejected a flare, or a burst of radiation that begins near the surface of a star, that ranks as one of the most violent seen anywhere in the galaxy.

"The star went from normal to 14,000 times brighter when seen in ultraviolet wavelengths over the span of a few seconds," said MacGregor, an assistant professor at the Center for Astrophysics and Space Astronomy (CASA) and Department of Astrophysical and Planetary Sciences (APS) at CU Boulder.

The team's findings hint at new physics that could change the way scientists think about stellar flares. They also don't bode well for any squishy organism brave enough to live near the volatile star.

"If there was life on the planet nearest to Proxima Centauri, it would have to look very different than anything on Earth," MacGregor said. "A human being on this planet would have a bad time."


Spectacular cloud formation observed over Mansalay, Philippines

Spectacular cloud formation observed over Mindoro, Philippines
The mysterious cloud formation spotted in Oriental Mindoro garnered various speculations from the online community.

The Facebook page "Youth for Mindoro" has shared the amazing photos of a strange cloud formation in Mansalay, Oriental Mindoro. The phenomenon happened last Wednesday afternoon (April 14, 2021).

According to the witnesses, the mysterious light has been formed above the clouds. The weird light looks like a crown roaring above the cloudy, which garnered various reactions from the social media users.

Comment: It is likely that atmospheric dust loading from increased comet and volcanic activity is contributing to the 'strange skies' we are witnessing, the cooling effect of which causes ice crystals to form. See also:


New Nova in Scorpius

With the recent discovery of Nova Scorpii 2021, three bright stellar explosions are now visible in small telescopes from dusk till dawn.

V1710 Scorpii
© Rob Kaufman
The new bright nova, V1710 Scorpii, glows conspicuously red in this photo taken on April 14, 2021. It's the third nova discovered in recent weeks that has reached 9th magnitude or brighter.
Wait a minute. Am I going to have to set the alarm and get up at 4 a.m.? Absolutely. And I'll do it without complaint. Not only are the recent novae in Cassiopeia and Sagittarius still bright at magnitudes at 8.1 and 9.9, respectively, but a brand new nova in Scorpius has just joined the scene. Add in Comet ATLAS (C/2020 R4), now at magnitude 9.5, and you know in your heart a dawn observing session is in your future.

Amateur astronomer Paul Camilleri of Northern Territory, Australia and the All-Sky Automated Survey for Supernovae (ASAS-SN) independently discovered the new object early on April 12th at visual magnitude 9.5. Formally named V1710 Scorpii, it brightened quickly to 8.5 before fading slightly, now simmering around 9.5 as of early April 15th. Oscillations like these are common, so the nova might continue to fade or re-brighten just as suddenly.

In an email, Camilleri shared a happy coincidence: "Interestingly, this discovery is my 10th nova, and it was found 30 years to the day of my first discovery in April 1991 and a few days short of my last discovery (April 14, 1993) some 28 years ago."
Nova Scorpii 2021
© Paul Camillari
This is Paul Camilleri's discovery image taken on April 12.7625 UT with a Nikon D3200 DSLR and 85mm f/2 lens. The exposure was five seconds at ISO 6400. Since it was made on a tripod without a tracking mount, the stars are slightly trailed.
He noted that the nova had an orange color on his photos, likely caused by emission from ionized hydrogen in the thin, expanding shell of gases ejected during the explosion. Spectra indicate that the object is a classical nova, meaning this is its first recorded eruption, and it belongs to the Fe II class, where prominent emission lines of ionized iron stand out in its spectrum.

Comet 2

New Comet C/2019 U5 (PANSTARRS)

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)

Comet C/2019 U5 (PANSTARRS)
© Remanzacco Blogspot


Possible nova detected in Sagittarius

Following the posting on the Central Bureau's Transient Object Confirmation Page about a possible Nova in Sgr (TOCP Designation: PNV J17581670-2914490) we performed some follow-up of this object through a TEL 0.6-m f/6.5 astrograph + CCD located in the El Sauce Observatory in Chile and operated by Telescope Live network (MPC Code X02).

This transient has been discovered by Andrew Pearce at 8.4 mag (unfiltered) on 2021-04-04.825 UT using a Canon 1100D DSLR camera with a 100mm f/2.8 lens. Total exposure time was 20 seconds (2 x 10s images stacked). Rob McNaught reported non-detection on 2021-04-02.776 UT (unfiltered limiting mag 11.0).

On images taken on April 06.40, 2021 we can confirm the presence of an optical counterpart with B-filtered CCD magnitude +8.955 (R-filtered & V-filtered images were saturated in 5-second exposures) at coordinates:

R.A. = 17 58 16.08, Decl.= -29 14 56.4

(equinox 2000.0; Gaia DR2 catalogue reference stars for the astrometry).

Our confirmation image (click on it for a bigger version):
© Remanzacco Blogspot


High-energy particle accelerators within our galaxy discovered

Move over, CERN. Unknown sources in the Milky Way dubbed "PeVatrons" accelerate protons to energies of a few peta-electronvolts - dozens of times higher than the yield of the Large Hadron Collider. Now, new data from a high-altitude experiment in Tibet confirm that such very-high-energy cosmic rays are indeed produced in our own galaxy.
Ultra high-energy rays
© APS; Background (atomic hydrogen distribution): HEASARC / LAMBDA / NASA / GFSC
Ultra high-energy diffuse gamma rays (yellow points) are distributed along the Milky Way Galaxy. The gray shaded area indicates the area outside the detectors' field of view.
"The results paint a much fuller picture of the PeVatron population in the Milky Way," says Pat Harding (Los Alamos National Laboratory), who was not involved in the study.

The distribution of cosmic rays by energy suggests these particles come in two varieties. The most extreme ultra-high-energy cosmic rays (UHECRs) are believed to come from remote galaxies (see the May 2021 issue of Sky & Telescope to learn more about these harbingers). But the majority of cosmic rays, with energies below 4 PeV, are thought to originate in the Milky Way. However, the true nature of the PeVatron particle accelerators has remained unknown, largely because the paths of cosmic rays are bent by galactic magnetic fields, so they do not "point back" to their origin.

A large team of Chinese and Japanese scientists known as the Tibet ASγ Collaboration has now detected a few dozen very-high-energy (VHE) gamma rays from the Milky Way that aren't associated with known sources. These gamma rays, collected between 2014 and 2017, are thought to be produced when cosmic rays slam into atomic nuclei in the interstellar medium. Theory says they carry about 10% of the original cosmic-ray energy. The most energetic one detected by the Tibet ASγ team packs a punch of 0.957 PeV - an all-time record.