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Reposted by Nereide

Nereide @drnereide.bsky.social · 1d

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A nice circumhorizontal arc (informally known as a fire rainbow, which is a misnomer) over West Virginia captured by Christa Harbig!

It is an optical phenomenon belonging to the family of ice halos, so it is neither fire nor a rainbow.

➡️ apod.nasa.gov/apod/ap21083...

🔭 🧪 #science

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$The image shows a circumhorizon arc (or circumhorizontal arc), an optical phenomenon resembling a fiery rainbow. It forms in a clear sky with cirrus clouds made of flat, hexagonal ice crystals aligned horizontally. These crystals refract sunlight, creating a colorful arc parallel to the horizon. Vibrant colors shine brightly against the blue sky, captured near North Fork Mountain, West Virginia.$

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Nereide @drnereide.bsky.social · 19h

A circumhorizontal arc, formed by refraction in ice crystals, is possible due to its position below the Sun, but its spectral band is more structured. The urban view might obscure the structure.
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Nereide @drnereide.bsky.social · 19h

Thanks for the details! Your direct observation of a phenomenon below the Sun, with an “oil on water” look and lack of structure, strongly suggests cloud iridescence, caused by diffraction of sunlight in ice crystals (not droplets) in thin clouds, likely cirrus.
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Nereide @drnereide.bsky.social · 1d

Stunning view!
Given the photo’s visual limitations, it’s likely a circumhorizontal arc. The vivid colors seem natural, due to refraction, not added. Can you confirm if the arc is below or above the Sun?

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Nereide @drnereide.bsky.social · 1d

The specific alignment of ice crystals creates the particular, horizon-parallel display, unlike the curved arc of a rainbow.
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Nereide @drnereide.bsky.social · 1d

producing a wide, vivid arc parallel to the horizon. While ice and water have slightly different refractive indices, the fundamental distinction lies in the crystal geometry & orientation, not the refractive index.
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Nereide @drnereide.bsky.social · 1d

a circular arc with a radius of 42° centered on the antisolar point. In contrast, a circumhorizontal arc requires plate-shaped, hexagonal ice crystals in cirrus clouds, aligned horizontally to refract sunlight. This happens only when the Sun is 58° high or greater above the horizon,
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Nereide @drnereide.bsky.social · 1d

You’re correct that a circumhorizontal arc forms through refraction, but calling it “essentially a rainbow” is misleading. It’s an ice halo, distinct from a rainbow. Rainbows result from sunlight undergoing refraction, internal reflection, and dispersion in spherical water droplets, forming...
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Nereide @drnereide.bsky.social · 1d

sunlight refracting through the ice crystals, as captured in this shot.

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Nereide @drnereide.bsky.social · 1d

The optical phenomenon in the photo is visible to the naked eye under the right conditions: high Sun and cirrus clouds with aligned ice crystals. A polarizing filter isn’t needed to see it, though it might slightly enhance contrast or colors. The vivid, flame-like arc appears naturally due to

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Nereide @drnereide.bsky.social · 1d

Yes, it is!

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Nereide @drnereide.bsky.social · 1d

A circumhorizontal arc (or circumhorizon arc) is a rare phenomenon because the Sun has to be 58° high or greater, there must be high altitude cirrus clouds with flat ice crystals, lastly sunlight has to enter the ice crystals at a specific angle.

Learn more➡️ www.atoptics.co.uk/blog/circumh...

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Circumhorizon Arc

This article explores the characteristics, visibility, and geographic distribution of the circumhorizon arc, a stunning optical phenomenon often mistaken for a fire rainbow. It discusses how to distin...

www.atoptics.co.uk

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Nereide @drnereide.bsky.social · 1d

The ice halo is formed by sunlight entering horizontally-oriented hexagonal, plate-shaped ice crystals in cirrus clouds, in this case cirrus fibratus clouds.

The halo is so wide that the arc appears parallel to the horizon, thus the name.

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Nereide @drnereide.bsky.social · 1d

🧵
A nice circumhorizontal arc (informally known as a fire rainbow, which is a misnomer) over West Virginia captured by Christa Harbig!

It is an optical phenomenon belonging to the family of ice halos, so it is neither fire nor a rainbow.

➡️ apod.nasa.gov/apod/ap21083...

🔭 🧪 #science

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$The image shows a circumhorizon arc (or circumhorizontal arc), an optical phenomenon resembling a fiery rainbow. It forms in a clear sky with cirrus clouds made of flat, hexagonal ice crystals aligned horizontally. These crystals refract sunlight, creating a colorful arc parallel to the horizon. Vibrant colors shine brightly against the blue sky, captured near North Fork Mountain, West Virginia.$

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Reposted by Nereide

Nereide @drnereide.bsky.social · 2d

"The nitrogen in our DNA, the calcium in our teeth, the iron in our blood, the carbon in our apple pies were made in the interiors of collapsing stars.
We are made of starstuff."

— Carl Sagan. Cosmos (1980).

Image source➡️ imagine.gsfc.nasa.gov/news/10sep08...

🔭 🧪 #science

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The image is an artist's illustration of one model of the bright gamma-ray burst GRB 080319B.
The explosion appears highly beamed into two bipolar jets, with a narrow inner jet (white) surrounded by a wider outer jet (green).

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Reposted by Nereide

Dr Elodie Chabrol @eloscicomm.bsky.social · 2d

Ça fait VRAIMENT TOUT DRÔLE de recevoir mes affiches CASIO Women Do Science ! 🥰 🤯
Tellement fière de faire partie de cette initiative !

🔗Découvrez ma page et téléchargez le poster ici lnkd.in/ejrpYndE
PS : Plume a validé les posters... mais a clairement refusé de recréer la pose 🐾

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Nereide @drnereide.bsky.social · 2d

enriching it with heavy elements, which contributes to the chemical enrichment of galaxies.

In other words, supernovae produce the elements that make up everything around us, including us.

So, yes, we are grateful to those distant stars: without their "deaths," we wouldn't exist!

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Nereide @drnereide.bsky.social · 2d

Yes, it is. When iron accumulates in the core of a massive star, energy generation through nuclear fusion finishs.

This leads to rapid gravitational collapse, followed by a supernova explosion. Supernovae pour the products of explosive nucleosynthesis into the interstellar medium,

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Nereide @drnereide.bsky.social · 2d

The quote “We are stardust, billion year old carbon” is from Joni Mitchell’s song Woodstock, though Crosby, Stills, Nash & Young’s cover made it iconic. :)

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Nereide @drnereide.bsky.social · 2d

You’re right, the bright star cluster does look like a reflection on the Bubble Nebula’s surface. The cosmos is really stunning.

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Nereide @drnereide.bsky.social · 2d

You're welcome!

Nereide @drnereide.bsky.social · 2d

Image description: Artist's illustration of one model of the bright gamma-ray burst GRB 080319B.
The explosion is highly beamed into two bipolar jets, with a narrow inner jet surrounded by a wider outer jet.
(More at the link above)

Image credit: NASA/Swift/Mary Pat Hrybyk-Keith and John Jones

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Nereide @drnereide.bsky.social · 2d

"The nitrogen in our DNA, the calcium in our teeth, the iron in our blood, the carbon in our apple pies were made in the interiors of collapsing stars.
We are made of starstuff."

— Carl Sagan. Cosmos (1980).

Image source➡️ imagine.gsfc.nasa.gov/news/10sep08...

🔭 🧪 #science

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Reposted by Nereide

Nereide @drnereide.bsky.social · 4d

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In this fascinating image by Russel Croman you can admire a stunning 3D effect of NGC 7635: the Bubble Nebula, an H II region emission nebula in Cassiopeia.

➡️ apod.nasa.gov/apod/ap05110...

The "bubble" is generated by the stellar wind from the...

🔭 🧪 #science

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The image shows NGC 7635, the Bubble Nebula. It is a 10-light-year gas sphere, pushed by the stellar wind of star BD+602522. To the lower right, a giant molecular cloud glows, heated by the star’s radiation. Shown in scientifically mapped colors to enhance contrast, it’s part of a larger star and shell complex, visible with a small telescope toward Cassiopeia.

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Reposted by Nereide

Nereide @drnereide.bsky.social · Sep 3

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An interesting study shares JWST breathtaking images of a protoplanetary disk seen edge-on around the protostar IRAS04302+2247, still nestled in its birth cloud.

The young star is located 525 ly away in the Taurus star-forming region.

Image Credit: ESA/Webb, NASA & CSA, M. Villenave et al

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"A wide-field image of IRAS 16594-4656 taken by the James Webb Space Telescope. The nebula’s bright core is split by a narrow dark band, with expansive rainbow lobes of light and colour radiating outward. Numerous background galaxies and stars are visible across the field."
From the press release.

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