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#darkmatter

5 posts5 participants0 posts today
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Ethan Siegel

Astronomers just found the smallest galaxy ever With just a mere 16 solar masses worth of stars, galaxy Ursa Major III/UNIONS 1 is by far the smallest galaxy ever discovered. But is it truly a galaxy, or just a collection of stars? bigthink.com/starts-with-... #space #astronomy #darkmatter

Astronomers just found the sma...

Big ThinkAstronomers just found the smallest galaxy everWith stars, gas, and dark matter, galaxies come in a great array of sizes. This new one, Ursa Major III/UNIONS 1, is the smallest by far.
Public
Gravity Grinch

Black Hole Week might be over, but today's arxiv had an interesting paper on a dwarf galaxy where a black hole provided enough mass to explain the observables and a dark-matter halo fit seems disfavoured: arxiv.org/abs/2505.06198

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arXiv.orgThe "Dark-Matter Dominated" Galaxy Segue 1 Modeled with a Black Hole and no Dark HaloThe dwarf spheroidal galaxy, Segue 1, is thought to have one of the largest ratios of dark matter to stellar mass. Using orbit-based dynamical models, we model Segue 1, including a dark halo and a central black hole. The best-fit model requires a black hole mass of $4 \pm 1.5 \times 10^5\ M_\odot$. The value of the black hole mass is the same with or without a dark halo. The mass-to-light ratio of the stars is poorly constrained by the dynamical modeling, reflecting that Segue 1 is dominated by mass other than stars. Dynamical models that exclude a black hole provide a worse fit and require a dark halo with very small scale radii of around 100 parsecs. Additionally, the zero black hole models require a stellar orbital distribution that is highly radially biased. The model with a black hole provides an orbital structure that is close to isotropic, more similar to other well-studied systems. We argue that the two-parameter models of stars and black hole provide a better description of Segue 1 than the three-parameter models of stars and two dark halo components. Additional support for a central black hole comes from a significant increase in the central rotation. Using individual velocities, we measure a rotation amplitude of $9.0 \pm 2.4\ \mathrm{km\ s^{-1}}$. Segue 1 is likely being tidally stripped at large radii, and we might be witnessing the remnant nucleus of a more massive system. Alternatively, given the high black hole mass relative to the stellar mass, Segue 1 is analogous to Little Red Dots seen in the early Universe.
#BlackHole#astronomy#astrophysics
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Ville 'cos' R

Katsottua: Dark Matter.

Koska juoni on aika jännä, en paljasta tässä paljon mitään muuta kun että kyseessä scifihenkinen draama, vaikka sijottuu nykymaailmaan. Vähän Severance-tyylinen mysteerikuvio.

Sangen hyvä ja juoni eskaloituu loppua kohden hienosti. Lässytyskohtauksia oli ehkä vähän liikaa, mutta ei häirinnyt kokemusta. Suosittelen. Toista kautta tuskin nähdään, kun juoni pääsi päätökseensä.

#sarjat#darkmatter
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