Stefano M
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h/t +annarita ruberto
Oxygen in the Great Carina Nebula
I has chanced upon astrophotographer +Dylan O'Donnell website and I was astonished by his work.
I'm sharing the image below, taken by him thanks to an 11″ Celestron F2 RASA telescope and a QHY9 mono CCD.
In this image, he decided the Hubble palette was the most compelling as the doubly ionised Oxygen spewing from the core is really brilliant and not normally so visible against the normally-red Hydrogen, seen here in the green areas.
► More technical information, at this link>> http://deography.com/oxygen-in-the-great-carina-nebula/
A jewel of the southern sky, the Great Carina Nebula, also known as NGC 3372, spans over 300 light-years, one of our galaxy's largest star forming regions. It lies in the Sagittarius-Carina arm of the Milky Way that is 7,500 light years from Earth. The Chandra X-Ray Observatory has detected more than 14,000 stars in the region.
The Carina Nebula is home to young, extremely massive stars, including the still enigmatic variable Eta Carinae, a star with well over 100 times the mass of the Sun. Eta Carinae is the brightest star near the image center, just left of the dusty Keyhole Nebula (NGC 3324). While Eta Carinae itself maybe on the verge of a supernova explosion, X-ray images indicate that the Great Carina Nebula has been a veritable supernova factory.
The Carina Nebula is one of the largest diffuse nebulae known (one of the largest H II regions, composed of ionized hydrogen gas, in our Milky Way galaxy), one that contains several open star clusters. In fact, there are many star clusters in its vicinity. Many of them are probably foreground clusters in front of the nebula. Two of these clusters are definitely within the nebula - Trumpler 14 and Trumpler 16. Trumpler 16 includes the star Eta Carinae as one of its member stars.
The Carina Nebula is home to several notable objects: the Mystic Mountain, the Homunculus Nebula, and the previously mentioned Keyhole Nebula.
It was discovered by Nicolas Louis de Lacaille in 1751–52 from the Cape of Good Hope.
Further reading and references
► Carina Nebula>> http://www.constellation-guide.com/carina-nebula/
► The Great Nebula in Carina, NGC 3372 >> http://oldweb.aao.gov.au/images/captions/uks006.html
► Carina Nebula - Hubble's 25th anniversary>> https://hubble25th.org/images/10
► NGC 3372 - The Eta Carinae Nebula>> http://www.atlasoftheuniverse.com/nebulae/ngc3372.html
#Universe, #CarinaNebula, #DiffuseNebulae, #Astronomy
I has chanced upon astrophotographer +Dylan O'Donnell website and I was astonished by his work.
I'm sharing the image below, taken by him thanks to an 11″ Celestron F2 RASA telescope and a QHY9 mono CCD.
In this image, he decided the Hubble palette was the most compelling as the doubly ionised Oxygen spewing from the core is really brilliant and not normally so visible against the normally-red Hydrogen, seen here in the green areas.
► More technical information, at this link>> http://deography.com/oxygen-in-the-great-carina-nebula/
A jewel of the southern sky, the Great Carina Nebula, also known as NGC 3372, spans over 300 light-years, one of our galaxy's largest star forming regions. It lies in the Sagittarius-Carina arm of the Milky Way that is 7,500 light years from Earth. The Chandra X-Ray Observatory has detected more than 14,000 stars in the region.
The Carina Nebula is home to young, extremely massive stars, including the still enigmatic variable Eta Carinae, a star with well over 100 times the mass of the Sun. Eta Carinae is the brightest star near the image center, just left of the dusty Keyhole Nebula (NGC 3324). While Eta Carinae itself maybe on the verge of a supernova explosion, X-ray images indicate that the Great Carina Nebula has been a veritable supernova factory.
The Carina Nebula is one of the largest diffuse nebulae known (one of the largest H II regions, composed of ionized hydrogen gas, in our Milky Way galaxy), one that contains several open star clusters. In fact, there are many star clusters in its vicinity. Many of them are probably foreground clusters in front of the nebula. Two of these clusters are definitely within the nebula - Trumpler 14 and Trumpler 16. Trumpler 16 includes the star Eta Carinae as one of its member stars.
The Carina Nebula is home to several notable objects: the Mystic Mountain, the Homunculus Nebula, and the previously mentioned Keyhole Nebula.
It was discovered by Nicolas Louis de Lacaille in 1751–52 from the Cape of Good Hope.
Further reading and references
► Carina Nebula>> http://www.constellation-guide.com/carina-nebula/
► The Great Nebula in Carina, NGC 3372 >> http://oldweb.aao.gov.au/images/captions/uks006.html
► Carina Nebula - Hubble's 25th anniversary>> https://hubble25th.org/images/10
► NGC 3372 - The Eta Carinae Nebula>> http://www.atlasoftheuniverse.com/nebulae/ngc3372.html
#Universe, #CarinaNebula, #DiffuseNebulae, #Astronomy
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Il sapere superficiale prima o poi presenta il conto, che è... salato.
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Mathematicians explain why solving the Rubik's Cube is so difficult
"If you thought solving a Rubik’s cube was difficult, you were right and maths can back you up. A recent study shows that the question of whether a scrambled Rubik’s cube of any size can be solved in a given number of moves is what’s called NP-complete – that’s maths lingo for a problem even mathematicians find hard to solve." …
"So if you’re frustrated about how long it’s taking you to solve a Rubik’s cube, it’s not just you. “You have the excuse now: Rubik’s cubes are legitimately hard,” Rudoy says. You’re not going to figure it out quickly, so you might as well sit back and enjoy the puzzle." …
#RubiksCube #mathematics #algorithm
"If you thought solving a Rubik’s cube was difficult, you were right and maths can back you up. A recent study shows that the question of whether a scrambled Rubik’s cube of any size can be solved in a given number of moves is what’s called NP-complete – that’s maths lingo for a problem even mathematicians find hard to solve." …
"So if you’re frustrated about how long it’s taking you to solve a Rubik’s cube, it’s not just you. “You have the excuse now: Rubik’s cubes are legitimately hard,” Rudoy says. You’re not going to figure it out quickly, so you might as well sit back and enjoy the puzzle." …
#RubiksCube #mathematics #algorithm
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h/t +annarita ruberto
Topsy-Turvy Motion Creates Light Switch Effect at Uranus
The alien aurorae on Jupiter and Saturn are well-studied, but not much is known about the aurorae of the giant ice planet Uranus.
"More than 30 years after Voyager 2 sped past Uranus, Georgia Institute of Technology researchers are using the spacecraft’s data to learn more about the icy planet. Their new study suggests that Uranus’ magnetosphere, the region defined by the planet’s magnetic field and the material trapped inside it, gets flipped on and off like a light switch every day as it rotates along with the planet. It’s “open” in one orientation, allowing solar wind to flow into the magnetosphere; it later closes, forming a shield against the solar wind and deflecting it away from the planet."
► Learn more at Georgia Tech>>
http://www.news.gatech.edu/2017/06/26/topsy-turvy-motion-creates-light-switch-effect-uranus
► The paper, “Diurnal and Seasonal Variability of Uranus’ Magnetosphere", has been published, 27 June 2017, in the Journal of Geophysical Research: Space Physics.>> http://onlinelibrary.wiley.com/doi/10.1002/2017JA024063/full
► Image explanation: This is a composite image of Uranus by Voyager 2 and two different observations made by Hubble — one for the ring and one for the aurorae.
Credit: ESA/Hubble & NASA, L. Lamy / Observatoire de Paris
Further reading
► Alien aurorae on Uranus>> https://www.spacetelescope.org/images/potw1714a/
► Non-terrestrial auroras>> https://en.wikipedia.org/wiki/Aurora#Non-terrestrial_auroras
► Hubble Spots Auroras on Uranus>> https://www.nasa.gov/image-feature/goddard/2017/hubble-spots-auroras-on-uranus
#SolarSystem, #AlienAurora, #UranusMagnetosphere, #Voyager2, #Research
The alien aurorae on Jupiter and Saturn are well-studied, but not much is known about the aurorae of the giant ice planet Uranus.
"More than 30 years after Voyager 2 sped past Uranus, Georgia Institute of Technology researchers are using the spacecraft’s data to learn more about the icy planet. Their new study suggests that Uranus’ magnetosphere, the region defined by the planet’s magnetic field and the material trapped inside it, gets flipped on and off like a light switch every day as it rotates along with the planet. It’s “open” in one orientation, allowing solar wind to flow into the magnetosphere; it later closes, forming a shield against the solar wind and deflecting it away from the planet."
► Learn more at Georgia Tech>>
http://www.news.gatech.edu/2017/06/26/topsy-turvy-motion-creates-light-switch-effect-uranus
► The paper, “Diurnal and Seasonal Variability of Uranus’ Magnetosphere", has been published, 27 June 2017, in the Journal of Geophysical Research: Space Physics.>> http://onlinelibrary.wiley.com/doi/10.1002/2017JA024063/full
► Image explanation: This is a composite image of Uranus by Voyager 2 and two different observations made by Hubble — one for the ring and one for the aurorae.
Credit: ESA/Hubble & NASA, L. Lamy / Observatoire de Paris
Further reading
► Alien aurorae on Uranus>> https://www.spacetelescope.org/images/potw1714a/
► Non-terrestrial auroras>> https://en.wikipedia.org/wiki/Aurora#Non-terrestrial_auroras
► Hubble Spots Auroras on Uranus>> https://www.nasa.gov/image-feature/goddard/2017/hubble-spots-auroras-on-uranus
#SolarSystem, #AlienAurora, #UranusMagnetosphere, #Voyager2, #Research
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Il medico non è un automa privo di emozioni.
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h/t +annarita ruberto
A Bright and Unusual X-ray Flare in B2 Star Rho Ophiuchi A
Stars can be like enormous magnets. In particular, stars similar to the Sun produce their own magnetic field in the “tachocline”, the transition region of the Sun between the radiative interior and the differentially rotating outer convective zone.
The stellar magnetic field is responsible for the formation of stellar corona, where plasma is confined and heated up to several million degrees. At this temperature, plasma emits at X-rays and UV.
Massive stars are fully radiative, and thus they are not expected to produce neither magnetic field nor coronal mass ejection. However, nature likes to allow exceptions to its own rules, and those ones are particularly interesting to scientists.
One of such exceptions consists of (magnetic) B-type stars.
B-type stars have from 2 to 16 times the mass of the Sun, are fully radiative and, thus, produce no magnetic field. Anyway, rare B-type stars are observed to have intense magnetic field and coronal X-ray emission, similar to that one observed in our Sun.
The study “The early B-type star Rho Oph A is an X-ray lighthouse”, from astronomer Ignazio Pillitteri at the Astronomical Observatory of Palermo (Italy) and his collaborators, is focused on one of these stars. They have analyzed X-ray observations of B2 star Rho Ophiuchi A (8-9 solar masses), and observed a long, intense and unusual X-ray flare. Rho Ophiuchi (ρ Ophiuchi) is a multiple star system in the constellation Ophiuchus. The central pair is known as Rho Ophiuchi AB. It consists of at least two blue-colored subgiants or main-sequence stars, designated Rho Ophiuchi A and B, respectively.
In the paper, recently published in Astronomy & Astrophysics, researchers claim this flare is quite similar to those ones observed in the Sun, where plasma is confined and heated in "coronal loops". Regarding the flare observed in Rho Oph A, the plasma is heated up to 60 millions degrees by a magnetic field of 300 G (the average solar magnetic field is 1 G), in a loop long about 25% - 30% of the stellar radius.
►The paper published in Astronomy & Astrophysics >> https://www.aanda.org/articles/aa/abs/2017/06/aa30070-16/aa30070-16.html
►The article in Italian at INAF - Astronomical Observatory of Palermo >>
http://www.astropa.inaf.it/pubblicato-lo-studio-the-early-b-type-star-rho-oph-a-is-an-x-ray-lighthouse-di-i-pillitteri/
► Image explanation: This wide-field view shows a spectacular region of dark and bright clouds, forming part of a region of star formation in the constellation of Ophiuchus (The Serpent Bearer). This picture was created from images in the Digitized Sky Survey 2.
Credit: ESO/Digitized Sky Survey 2 >> https://cdn.eso.org/images/screen/eso1604d.jpg
#Bstars, #CoronalActivity, #Flare, #Research, #StellarStructureandEvolution
Stars can be like enormous magnets. In particular, stars similar to the Sun produce their own magnetic field in the “tachocline”, the transition region of the Sun between the radiative interior and the differentially rotating outer convective zone.
The stellar magnetic field is responsible for the formation of stellar corona, where plasma is confined and heated up to several million degrees. At this temperature, plasma emits at X-rays and UV.
Massive stars are fully radiative, and thus they are not expected to produce neither magnetic field nor coronal mass ejection. However, nature likes to allow exceptions to its own rules, and those ones are particularly interesting to scientists.
One of such exceptions consists of (magnetic) B-type stars.
B-type stars have from 2 to 16 times the mass of the Sun, are fully radiative and, thus, produce no magnetic field. Anyway, rare B-type stars are observed to have intense magnetic field and coronal X-ray emission, similar to that one observed in our Sun.
The study “The early B-type star Rho Oph A is an X-ray lighthouse”, from astronomer Ignazio Pillitteri at the Astronomical Observatory of Palermo (Italy) and his collaborators, is focused on one of these stars. They have analyzed X-ray observations of B2 star Rho Ophiuchi A (8-9 solar masses), and observed a long, intense and unusual X-ray flare. Rho Ophiuchi (ρ Ophiuchi) is a multiple star system in the constellation Ophiuchus. The central pair is known as Rho Ophiuchi AB. It consists of at least two blue-colored subgiants or main-sequence stars, designated Rho Ophiuchi A and B, respectively.
In the paper, recently published in Astronomy & Astrophysics, researchers claim this flare is quite similar to those ones observed in the Sun, where plasma is confined and heated in "coronal loops". Regarding the flare observed in Rho Oph A, the plasma is heated up to 60 millions degrees by a magnetic field of 300 G (the average solar magnetic field is 1 G), in a loop long about 25% - 30% of the stellar radius.
►The paper published in Astronomy & Astrophysics >> https://www.aanda.org/articles/aa/abs/2017/06/aa30070-16/aa30070-16.html
►The article in Italian at INAF - Astronomical Observatory of Palermo >>
http://www.astropa.inaf.it/pubblicato-lo-studio-the-early-b-type-star-rho-oph-a-is-an-x-ray-lighthouse-di-i-pillitteri/
► Image explanation: This wide-field view shows a spectacular region of dark and bright clouds, forming part of a region of star formation in the constellation of Ophiuchus (The Serpent Bearer). This picture was created from images in the Digitized Sky Survey 2.
Credit: ESO/Digitized Sky Survey 2 >> https://cdn.eso.org/images/screen/eso1604d.jpg
#Bstars, #CoronalActivity, #Flare, #Research, #StellarStructureandEvolution
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Sindrome sgombroide, Anisakis: solo a leggerne passa l'appetito. Purtroppo le intossicazioni e le parassitosi da consumo di pesce sono più frequenti di un tempo. Tuttavia possiamo proteggerci con qualche semplice accorgimento.
Qui c'è qualche informazione pratica.
Larve di Anisakis nel pesce crudo
http://prontosoccorso.eumed.org/area-pubblica/4086/larve-di-anisakis-nel-pesce-crudo/
Il consumo di pesce crudo
http://prontosoccorso.eumed.org/area-pubblica/7858/il-consumo-di-pesce-crudo/
Qui c'è qualche informazione pratica.
Larve di Anisakis nel pesce crudo
http://prontosoccorso.eumed.org/area-pubblica/4086/larve-di-anisakis-nel-pesce-crudo/
Il consumo di pesce crudo
http://prontosoccorso.eumed.org/area-pubblica/7858/il-consumo-di-pesce-crudo/
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The unnatural desire for naturalness
There's a particle called the muon that's almost like the electron, except it's about 206.768 times heavier. Nobody knows why. The number 206.768 is something we measure experimentally, with no explanation so far. Theories of physics tend to involve a bunch of unexplained numbers like this. If you combine general relativity with Standard Model of particle physics, there are about 25 of these constants.
Many particle physicists prefer theories where these constants are not incredibly huge and not incredibly tiny. They call such theories natural. Naturalness sounds good - just like whole wheat bread. But there's no solid evidence that this particular kind of naturalness is really a good thing. Why should the universe prefer numbers that aren't huge and aren't tiny? Nobody knows.
For example, many particle physicists get upset that the density of the vacuum is about
0.000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001
Planck masses per Planck volume. They find it 'unnatural' that this number is so tiny. They think it requires 'fine-tuning', which is supposed to be bad.
I agree that it would be nice to explain this number. But it would also be nice to explain the mass of the muon. Is it really more urgent to explain a tiny number than a number like 206.768, which is neither tiny nor huge?
+Sabine Hossenfelder say no, and I tend to agree. More precisely: I see no a priori reason why naturalness should be a feature of fundamental physics. If for some mysterious reason the quest for naturalness always led to good discoveries, I would support it. In science, it makes sense to do things because they tend to work, even if we're not sure why. But in fact, the quest for naturalness has not always been fruitful. Sometimes it seems to lead us into dead ends.
Besides the cosmological constant, another thing physicists worry about is the Higgs mass. Avoiding the 'unnaturalness' of this mass is a popular argument for supersymmetry... but so far that's not working so well. Sabine writes:
Here is a different example for this idiocy. High energy physicists think it’s a problem that the mass of the Higgs is 15 orders of magnitude smaller than the Planck mass because that means you’d need two constants to cancel each other for 15 digits. That’s supposedly unlikely, but please don’t ask anyone according to which probability distribution it’s unlikely. Because they can’t answer that question. Indeed, depending on character, they’ll either walk off or talk down to you. Guess how I know.
Now consider for a moment that the mass of the Higgs was actually about as large as the Planck mass. To be precise, let’s say it’s 1.1370982612166126 times the Planck mass. Now you’d again have to explain how you get exactly those 16 digits. But that is, according to current lore, not a fine-tuning problem. So, erm, what was the problem again?
Sabine explains things in such down-to-earth terms, with so few of the esoteric technicalities that usually grace discussions of naturalness, that it may be worth reading a more typical discussion of naturalness just to imbibe some of the lore.
This one is quite good, because it includes a lot of lore but doesn't try too hard to intimidate you into believing in the virtue of naturalness:
• G.F. Giudice, Naturally speaking: the naturalness criterion and physics at the LHC, available at https://arxiv.org/abs/0801.2562.
#physics
There's a particle called the muon that's almost like the electron, except it's about 206.768 times heavier. Nobody knows why. The number 206.768 is something we measure experimentally, with no explanation so far. Theories of physics tend to involve a bunch of unexplained numbers like this. If you combine general relativity with Standard Model of particle physics, there are about 25 of these constants.
Many particle physicists prefer theories where these constants are not incredibly huge and not incredibly tiny. They call such theories natural. Naturalness sounds good - just like whole wheat bread. But there's no solid evidence that this particular kind of naturalness is really a good thing. Why should the universe prefer numbers that aren't huge and aren't tiny? Nobody knows.
For example, many particle physicists get upset that the density of the vacuum is about
0.000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001
Planck masses per Planck volume. They find it 'unnatural' that this number is so tiny. They think it requires 'fine-tuning', which is supposed to be bad.
I agree that it would be nice to explain this number. But it would also be nice to explain the mass of the muon. Is it really more urgent to explain a tiny number than a number like 206.768, which is neither tiny nor huge?
+Sabine Hossenfelder say no, and I tend to agree. More precisely: I see no a priori reason why naturalness should be a feature of fundamental physics. If for some mysterious reason the quest for naturalness always led to good discoveries, I would support it. In science, it makes sense to do things because they tend to work, even if we're not sure why. But in fact, the quest for naturalness has not always been fruitful. Sometimes it seems to lead us into dead ends.
Besides the cosmological constant, another thing physicists worry about is the Higgs mass. Avoiding the 'unnaturalness' of this mass is a popular argument for supersymmetry... but so far that's not working so well. Sabine writes:
Here is a different example for this idiocy. High energy physicists think it’s a problem that the mass of the Higgs is 15 orders of magnitude smaller than the Planck mass because that means you’d need two constants to cancel each other for 15 digits. That’s supposedly unlikely, but please don’t ask anyone according to which probability distribution it’s unlikely. Because they can’t answer that question. Indeed, depending on character, they’ll either walk off or talk down to you. Guess how I know.
Now consider for a moment that the mass of the Higgs was actually about as large as the Planck mass. To be precise, let’s say it’s 1.1370982612166126 times the Planck mass. Now you’d again have to explain how you get exactly those 16 digits. But that is, according to current lore, not a fine-tuning problem. So, erm, what was the problem again?
Sabine explains things in such down-to-earth terms, with so few of the esoteric technicalities that usually grace discussions of naturalness, that it may be worth reading a more typical discussion of naturalness just to imbibe some of the lore.
This one is quite good, because it includes a lot of lore but doesn't try too hard to intimidate you into believing in the virtue of naturalness:
• G.F. Giudice, Naturally speaking: the naturalness criterion and physics at the LHC, available at https://arxiv.org/abs/0801.2562.
#physics
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Post has shared content
h/t +annarita ruberto
Gravitational Waves Could Hint at Hidden Dimensions
That is what seems to suggest a recent study at Max Planck Institute for Gravitational Physics in Potsdam, Germany.
Gustavo Lucena Gómez and his colleague David Andriot set out to calculate how potential extra dimensions- in addition to the four ones we are used to consider from "after" Einstein- would affect the gravitational waves, ripples in space-time caused by the motion of massive objects and detected, for the first time in 2015, by LIGO.
They found two peculiar effects: extra waves at high frequencies, and a modification of how gravitational waves stretch space.
In their paper, they discuss whether these two effects could be observed.
More precisely, they study the consequences of putative extra dimensions on four-dimensional gravitational waves, and whether related effects could be detected.
So Lucena Gómez and Andriot focused in detail on the physics associated with the two effects mentioned above, explain why they could not have been detected so far, and discuss to what extent they could be observed in the future.
► Read the article from Max Planck Institute for Gravitational Physics >>
http://www.aei.mpg.de/2070241/hints-of-extra-dimensions-in-gravitational-waves
► Read the paper "Signatures of extra dimensions in gravitational waves", published in the Journal of Cosmology and Astroparticle Physics, Volume 2017, June 2017
► The preprint version of the study>> https://arxiv.org/pdf/1704.07392.pdf
► Image explanation: Merging black holes generate gravitational waves. These ripples in space-time might be used to unveil hidden dimensions.
© Simulating eXtreme Spacetimes (SXS)
Further reading
► Gravitational waves could show hints of extra dimensions>>
https://www.newscientist.com/article/mg23431244-200-gravitational-waves-could-show-hints-of-extra-dimensions/
#Astrophysics, #ExtraDimensions, #GravitationalWaves, #Research
That is what seems to suggest a recent study at Max Planck Institute for Gravitational Physics in Potsdam, Germany.
Gustavo Lucena Gómez and his colleague David Andriot set out to calculate how potential extra dimensions- in addition to the four ones we are used to consider from "after" Einstein- would affect the gravitational waves, ripples in space-time caused by the motion of massive objects and detected, for the first time in 2015, by LIGO.
They found two peculiar effects: extra waves at high frequencies, and a modification of how gravitational waves stretch space.
In their paper, they discuss whether these two effects could be observed.
More precisely, they study the consequences of putative extra dimensions on four-dimensional gravitational waves, and whether related effects could be detected.
So Lucena Gómez and Andriot focused in detail on the physics associated with the two effects mentioned above, explain why they could not have been detected so far, and discuss to what extent they could be observed in the future.
► Read the article from Max Planck Institute for Gravitational Physics >>
http://www.aei.mpg.de/2070241/hints-of-extra-dimensions-in-gravitational-waves
► Read the paper "Signatures of extra dimensions in gravitational waves", published in the Journal of Cosmology and Astroparticle Physics, Volume 2017, June 2017
► The preprint version of the study>> https://arxiv.org/pdf/1704.07392.pdf
► Image explanation: Merging black holes generate gravitational waves. These ripples in space-time might be used to unveil hidden dimensions.
© Simulating eXtreme Spacetimes (SXS)
Further reading
► Gravitational waves could show hints of extra dimensions>>
https://www.newscientist.com/article/mg23431244-200-gravitational-waves-could-show-hints-of-extra-dimensions/
#Astrophysics, #ExtraDimensions, #GravitationalWaves, #Research
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