2 Persons are tagged with #astrophysics

#astrophysics

wazoox@diasp.eu
Emmanuel Florac

Giant structure in space challenges our understanding of the universe

#science #space #astrophysics

About 9.2 billion light-years from Earth is a colossal structure which has confounded astronomers.

The discovery might upend current cosmological theories.

What they’ve found is a 1.3-billion-light-year-across, almost perfect ring of galaxies. No such structure has been seen before. And it doesn’t match any known formation mechanism. It has been dubbed the “Big Ring.”

https://cosmosmagazine.com/space/astronomy/giant-structure-space-universe/

Giant structure in space challenges our understanding of the universe

About 9.2 billion light-years from Earth is a colossal structure in the universe which has confounded astronomers.

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rhysy@diaspora.glasswings.com
Rhysy

This is an intriguing but very preliminary result.

Basically they've found four globular clusters in very close proximity to each other, a few arcseconds apart and without an associated host galaxy. You might get the odd one or two wandering around after being torn from their parent galaxies by some interaction or other, but four is extremely unlikely. So one possibility is that they're part of a dark galaxy in which all the optical emission is in the globular clusters. This would be weird since the highest mass fraction in globular clusters is around 10-20%. This might have been higher when those galaxies were formed, but over time stars should be lost from the clusters to fill in the gap.

That this hasn't happened here would make this extremely weird unless it's just formed. In which case there ought to be plenty of gas lying around... but here things get immediately dubious. There's a possible parent galaxy not all that far away and it's not clear to me why this isn't the most obvious interpretation - they mention it's discussed in a (much longer) earlier paper, but that looks excessively technical, and they don't actually say why they seemingly don't think this is very likely.

Additionally, they show what the diffuse light would look like in their data if it comprised the same stellar mass as in the globular clusters. It would be detectable, but just barely, so this doesn't look like they've achieved a very strong constraint on the diffuse emission to me. As they say, it wouldn't have to be much more diffuse to be completely undetectable.

Much more interesting than the deep optical data they have here would be measurements of the gas and the velocities of the clusters. If they're all at similar velocities that would be compelling evidence that they're physically associated, and if there's lots of gas, that would argue in favour of a recent origin. As it is, without having read their earlier paper, I think it's more likely that these are just clusters in the halo of the nearest galaxy and nothing unusual.

#Science
#Space
#Astronomy
#Astrophysics

https://arxiv.org/abs/2405.12907

Deep HST/UVIS imaging of the candidate dark galaxy CDG-1

CDG-1 is a tight grouping of four likely globular clusters in the Perseus cluster, and a candidate dark galaxy with little or no diffuse light. Here we provide new constraints on the luminosity of any underlying stellar emission, using HST/UVIS...

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rhysy@diaspora.glasswings.com
Rhysy

On a weird paper claiming to have found a sample of very red, gas-rich galaxies not forming stars. In the original draft (which I'd downloaded some months ago) they didn't have any images of their sample, but presented a very nice narrative of how these were definitely very strange objects. But when I checked the images manually, which they now include in an appendix in the final version, many of them look like normal spiral galaxies. With great big blue spiral arms, it's very difficult to believe they really have unusual low levels of star formation. You just don't get blue structures like this without forming stars. For sure the central regions may be quenched, but surely not the whole galaxy as they claim.

I should probably try and read the new version but I just don't want to.

#Science
#Space
#Galaxies
#Astrophysics

https://llittlephysicists.blogspot.com/2024/05/red-dead-but-very-well-fed.html

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rhysy@diaspora.glasswings.com
Rhysy

The spacecraft used Venus flybys to sling itself successively closer to the sun, and on April 28, 2021, it touched the corona for the first time. It was now the closest spacecraft to our star and the fastest human-made object ever launched. (In fact, last month it passed by the sun for the 18th time at a speed that would get you from Washington, D.C., to Los Angeles in about 20 seconds, and from the Earth to the moon in 36 minutes.)

From near Earth, the solar wind looks like a turbulent fluid that is loosely related to the sun at only the largest scales. But from up close, its structure directly reflects the structures on the solar surface. Instead of being a disorganized fluid, the near-sun solar plasma whooshes outward in streamlets that often match the sizes of the convective supergranules on the sun’s surface — the cells around which magnetic fields concentrate, amplify and escape into the corona.

During each solar orbit, the spacecraft zoomed through those streamlets, and it found a telltale fingerprint of magnetic activity that permeated the plasma and pointed to a source for the corona’s heat. Called “switchbacks,” these fingerprints were S-shaped structures formed by brief reversals in the locally measured magnetic field. Such switchbacks form (at least, according to most scientists) when closed magnetic loops collide with open magnetic loops and connect with them, during what’s known as an interchange reconnection event. As with good champagne in a bottle, the only way to release energy and plasma from a tangled, closed magnetic loop is to uncork it by breaking it open and reconnecting it with an open field line. These reconnection events generate heat and sling solar material into space — thus warming the corona and accelerating particles in the solar wind.

#Science
#Space
#Astrophysics

https://www.quantamagazine.org/how-a-nasa-probe-solved-a-scorching-solar-mystery-20240429/

How a NASA Probe Solved a Scorching Solar Mystery | Quanta Magazine

The outer layers of the sun’s atmosphere are a blistering million degrees hotter than its surface. The hidden culprit? Magnetic activity.

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rhysy@diaspora.glasswings.com
Rhysy

Fun ! But someone needs to tell them they can use other words than "however".

Einstein's theory of general relativity predicts neutron stars to be lighter than three times the mass of our Sun. However, the exact value of the maximum mass that a neutron star can have before collapsing into a black hole is unknown. “Considering electromagnetic observations and our present grasp of stellar evolution, there were expected to be very few black holes or neutron stars within the range of three to five solar masses. However, the mass of one of the newly discovered objects precisely aligns with this range,” Buonanno elaborates.

In recent years, astronomers have uncovered several objects whose masses potentially fit within this elusive gap. In the case of GW190814, LIGO and Virgo identified an object at the lower boundary of the mass spectrum. However, the compact object detected via the gravitational-wave signal GW230529 marks the first instance where its mass unequivocally falls within this gap... None of the previous candidates for objects in this mass range have been identified with the same certainty.

Scientists can only make an educated guess as to how the heavier of the compact objects – most likely a lightweight black hole – in the binary that emitted GW230529 was formed. It is too light to be the direct product of a supernova. It is possible – but unlikely – that it was formed during a supernova, where material initially ejected in the explosion falls back and causes the newly formed black hole to grow. It is even less likely that the black hole was formed in the merger of two neutron stars. An origin as a primordial black hole in the early days of the universe is also possible, but not very likely. Finally, the researchers cannot completely rule out the possibility that the heavier object is not a light black hole, but an extremely heavy neutron star.

#Science
#Space
#Astronomy
#Astrophysics

https://www.mpg.de/21778967/0404-grav-mysterious-object-in-the-gap-152520-x

Mysterious object in the gap

When a black hole and a neutron star merge

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psychmesu@diaspora.glasswings.com
psychmesu

https://mastodon.online/@umplus/112175055235649848 umplus@mastodon.online - #UMPlus - Magical night in Atacama

https://www.universomagico.net/2024/03/noche-magica-en-atacama.html

Astronomer Petr Horálek has produced a magical image. The Atacama Desert has been the setting chosen to photograph a spectacularly colorful sky in which the bright stars, which give light to the sky, become the protagonists. In addition, the red color of the hydrogen atoms ionized by the energetic stars is distributed throughout the galaxy, tinting the.....
#astronomy #space #astrophysics #astrophotography

Universo Mágico (@umplus@mastodon.online)

Attached: 1 image #UMPlus - Magical night in Atacama https://www.universomagico.net/2024/03/noche-magica-en-atacama.html Astronomer Petr Horálek has produced a magical image. The Atacama Desert has been the setting chosen to photograph a...

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rhysy@diaspora.glasswings.com
Rhysy

A recent paper attempts to say that maybe the distance of NGC 1052-DF4 is actually 17 Mpc, not 20 Mpc after all ! GASP !

Why is this in any way interesting ? Well, DF4 was one of those galaxies claimed to lack dark matter. The distance in this case matters a lot : if it was at 20 Mpc, it'd be weird, but if it was only 13 Mpc, it'd be normal. Independent measurements have confirmed it's actually 20 Mpc, so it is indeed a strange object after all. But then, simulations found a way to produce such an object just by rare but physically-normal conditions : in the right circumstances, it is possible to strip the dark matter from a dwarf galaxy but leave its stars intact.

The authors of this paper say there should still be some signatures of tidal interactions left over though, so they go looking for them with incredibly deep imaging. They confirm that this is the case for the similarly-famous galaxy NGC 1052-DF2 (thought I'm skeptical of this), but very clearly show that DF4 is undisturbed. Absolutely nothing is going on in its outskirts at all. This is the reason they propose that the distance controversy might need to be re-ignited, noting that other galaxies in the region have been found to be at 17 Mpc rather than 20 Mpc.

To me this feels like a weak and circumstantial argument, and 17 Mpc wouldn't be enough to explain the lack of dark matter anyway. Not only that, but this ignores the now-sizeable population of other galaxies with similar claims for serious dark matter deficiencies.

#Space
#Science
#Astronomy
#Astrophysics

https://llittlephysicists.blogspot.com/2024/02/back-from-grave.html

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rhysy@diaspora.glasswings.com
Rhysy

On arXiv today, a very nice paper shows that one of the largest optically dark gas clouds isn't quite optically dark after all : it has at least one small patch of very new star formation. It's optically pathetic but the data is good enough that it's definitely real. This has implications for the formation of the cloud itself, which now looks more likely to be the result of ram pressure stripping from one of the galaxies in the vicinity. Many questions still remain, however, not least as to why only a very small part of the cloud is forming stars and why it's apparently only just started doing so.

#Science
#Astronomy
#Astrophysics
#Galaxies

https://llittlephysicists.blogspot.com/2024/02/taking-galactic-paternity-test.html

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