Dark Star

[Recusant]

After a site search, and specifically the Science board, it seems that the term dark star is practically absent here. The term itself has been around since at least the 1800s though I imagine it was probably used in astrology or in a metaphorical sense at that time. In pop culture, off the top of my head I note that it's the title of a somewhat bleak science fiction film, and a Grateful Dead song. I haven't heard it in science before that I can recall.

This item could go in the cosmology thread, but right now it seems more like a specific bit of science exotica. I don't know how recently scientists started speculating about a star at least partially composed of dark matter, but it's something I hadn't considered. Dr. Ilie, quoted in the article, appears to be pretty certain they exist.

"JWST May Have The Best Evidence Yet of a Bizarre 'Dark Star'" | Science Alert

JWST might have spotted the 'smoking gun' of a hypothetical object called a dark star in the distant Universe. If confirmed, this discovery could solve several mysteries of physics.

A dark star may sound like an oxymoron, but it would still emit light and energy. It wouldn't be powered by nuclear fusion like a garden-variety star, however – it would be running on a core of interacting dark matter particles.

"Supermassive dark stars are extremely bright, giant, yet puffy clouds made primarily out of hydrogen and helium, which are supported against gravitational collapse by the minute amounts of self-annihilating dark matter inside them," says Cosmin Ilie, an astrophysicist at Colgate University in the US.

Now, researchers have found the best evidence so far for the existence of dark stars. While studying four of the most distant objects ever observed, the team found that all are consistent with a dark star explanation.

Most intriguingly, though, one of the objects showed a particular light absorption feature at the wavelength of 1,640 Angstrom. This is considered a sure sign of dark stars, which arises from singly ionized helium in their atmospheres.

"While the signal-to-noise ratio of this feature is relatively low, it is the first time we found a potential smoking gun signature of a dark star. Which, in itself, is remarkable," says Ilie [University of Texas press release].

Soon after JWST fired up in 2021 and began peering farther back in space and time than humans ever had before, it caught some unexpected sights. Near the dawn of time sat what looked like huge galaxies at a moment when there shouldn't have been enough time (literally) for them to have grown so big.

Astrophysicists quickly came up with a possible explanation for some of these: Dark stars, which could contain as much as a million Suns-worth of mass, would look similar to galaxies from this distance.

[Continues . . .]

The paper is open access:

"Spectroscopic Supermassive Dark Star candidates" | Proceedings of the National Academy of Sciences

Abstract:

Dark Stars (DSs), i.e., early stars composed almost entirely of hydrogen and helium but powered by Dark Matter (DM), could form in zero metallicity clouds located close to the center of high redshift DM halos. In 2023, three of us identified (in a PNAS work) the first three photometric DS candidates: JADES-GS-z11-0, JADES-GS-z12-0, and JADES-GS-z13-0.

We report here our results of a follow-up analysis based on available NIRSpec JWST data. We find that JADES-GS-z11-0 and JADES-GS-z13-0 are spectroscopically consistent with a DS interpretation. Moreover, we find two additional spectroscopic DS candidates: JADES-GS-z14-0 and JADES-GS-z14-1, with the former being the second most distant luminous object ever observed.

We furthermore identify, in the spectrum of JADES-GS-z14-0, a tentative feature (S/N ~ 2) indicative of the smoking gun signature of DSs: the He II 1640 absorption line. In view of ALMA's recent identification of a probable O III nebular emission line in the spectrum of JADES-GS-z14-0, the simple interpretation of this object as an isolated DS is unlikely.

If both spectral features survive follow-up observations, it would imply a DS embedded in a metal rich environment, requiring theoretical refinements of the formation of evolution of DSs, which in previous studies were assumed to form in isolation, without any companions.

[Dark Lightning]

That's wild stuff!

[The Magic Pudding..]

I like the CSNY Darkstar, it used to be on the end of 45/90 minute tape.
If an album didn't fill up a side a good song from a weak album often got added.

[Recusant]

Yeah that's a fine track. A well-played Rhodes piano is something I always enjoy. 

 


This seems as good a dark matter thread as any for this item.

"Mysterious Glow Detected in Space Could Be Dark Matter Destroying Itself" | Science Alert

A strange gamma-ray glow emanating from the heart of the Milky Way could be the long-sought fingerprint of dark matter particles annihilating each other, evidence suggests.

A new research effort involving simulations of Milky-Way-like galaxies shows that the mysterious, unexplained extra gamma radiation emanating from the region is equally likely to be due to dark matter annihilation as to millisecond pulsars – and the dark matter hypothesis might even have a slight edge.

"Dark matter dominates the Universe and holds galaxies together. It's extremely consequential and we're desperately thinking all the time of ideas as to how we could detect it," says astrophysicist Joseph Silk of Johns Hopkins University.

"Gamma rays, and specifically the excess light we're observing at the center of our galaxy, could be our first clue."

This gamma-ray glow, known as the Galactic Center GeV Excess (GCE), has puzzled astronomers since its discovery in 2009 in data from NASA's Fermi Gamma-ray Space Telescope. Something in the galactic center is producing a glow in the highest-energy form of light in the Universe, but whatever that something is, astronomers have yet to pin it down.

There are two leading candidates. One of those is dark matter, the mysterious source of extra gravity hanging around the Universe that can't be explained by the normal matter that makes up everything we can directly detect.

[. . .]

The other candidate is millisecond pulsars. These are neutron stars at the very end of their life cycle, formed from the collapsed core of a massive star that has ejected most of its material in a supernova explosion. What makes a neutron star a pulsar is its extremely rapid spin. As it spins, it emits beams of radio waves, particles, and radiation, including X-rays and gamma rays. As these beams sweep around, the pulsar appears to, well, pulse.

Astronomers have yet to detect the population of pulsars that could be responsible for the GCE, but there are ways to narrow down the possibilities. The population of old stars that should include pulsars in the galactic bulge – the central, bubble-shaped region of the Milky Way – seems to form an X-shape, while previous research suggests the Milky Way's dark matter halo is spherical.

[Continues . . .]

The paper is behind a paywall, but I found a preprint version:

"Fermi-LAT Galactic Center Excess morphology of dark matter in simulations of the Milky Way galaxy" | arXiv

Abstract (as published):

The strongest experimental evidence for dark matter is the Galactic Center gamma-ray excess observed by the Fermi telescope and even predicted prior to discovery as a potential dark matter signature via weakly interacting massive particle dark matter self-annihilations. However, an equally compelling explanation of the excess gamma-ray flux refers to a population of old millisecond pulsars that also accounts for the observed boxy morphology inferred from the bulge old star population.

We employ a set of Milky Way-like galaxies found in the hestia constrained simulations of the local universe to explore the rich morphology of the central dark matter distribution, motivated by the GAIA discovery of a vigorous early merging history of the Milky Way galaxy. We predict a significantly nonspherical gamma-ray morphology from the weakly interacting massive particle interpretation. Future experiments, such as the Cherenkov Telescope Array, that extend to higher energies, should distinguish between the competing interpretations.