RE: https://mastodon.social/@pomarede/115860719793606685
"[...] in a **modest neighborhood** called The Solar System [...]", "solar *interstellar neighborhood*", "[...] it's like a huge collected **city** [...]": Mr. Hawking seemed to be well aware it was all our **home**! 🛖 It has been so exciting to join him in the "ultimate voyage" which is his *Genius* documentary...! I recommend it if you want to get a bit more familiar with your cosmic neighborhood! 🌌 🗺️ ✨
#Laniakea #Astronomy #StephenHawking #Milkyway #LaniakeaSupercluster #Solarsystem #Earth
Hidden Vela Supercluster Revealed by First Hybrid Redshift & Peculiar Velocity Reconstruction
A large fraction of the extragalactic sky is obscured by foreground dust and stars along the plane of the Milky Way, leaving a major gap (~ 20%) in whole-sky maps of large-scale structures -- an incompleteness that is even more severe for peculiar velocity samples. This has long limited an unambiguous interpretation of observed cosmic flows and their connection to the underlying mass-density field.
We present a new hybrid reconstruction methodology which combines 65,518 galaxy peculiar velocity distances from the CF4++ catalogue (Courtois2025) with 8283 new galaxy redshifts observed near the southern Galactic plane (|b| <= 10 degrees) Zone of Avoidance. A major advance is the inclusion of 2176 high-sensitivity, interferometric HI redshifts obtained with the SARAO MeerKAT telescope which for the first time provide coverage of the innermost 3degrees-wide strip of the southern ZOA and to unprecedented depth.
This hybrid redshifts & peculiar velocities approach yields a substantially revised view of the inferred overdensities in and around the ZOA. In particular, the Vela supercluster emerges as a dominant mass concentration, rivaling the Shapley concentration and exceeding the mass associated with Laniakea and the Great Attractor region. With a total mass of 33.8 10^16 Msol, a characteristic radius of 70 hmpc, and a double core morphology at a distance of 189 hmpc, Vela dominates the mass budget and gravitational influence of the southern Zone of Avoidance. These results provide the most complete and dynamically consistent picture to date of the southern Zone of Avoidance and demonstrate the transformative potential of hybrid reconstruction techniques tailored for the next generation of large-scale surveys.
Structures cosmiques : une famille de géantes
Comment Quipu, structure parmi les plus grandes, a-t-elle été identifiée ? De quoi sont composés les filaments de galaxies et de matière noire qui forment les structures de l'univers ? En quoi leur identification permet-elle de préciser notre compréhension de la cosmologie ?
Revisiting the Great Attractor: The Local Group's streamline trajectory, cosmic velocity and dynamical fate
We revisit the Great Attractor using the Manticore-Local suite of digital twins of the nearby Universe. The Great Attractor concept has been proposed as an answer to three distinct questions: what sources the Local Group velocity in the cosmic microwave background frame, where present-day velocity streamlines converge, and where the Local Group is moving to. Addressing the original motivation of the Great Attractor -- explaining the Local Group cosmic velocity -- we find that mass within $155~h^{-1}\mathrm{Mpc}$ accounts for only ${\sim}72\%$ of that velocity magnitude with ${\sim}38\,°$ directional offset. We show that even in the purely linear regime convergence within this volume is not guaranteed, particularly when also accounting for small-scale contributions to the observer velocity; no single structure, including the proposed Great Attractor, would be expected to dominate the velocity budget. Streamline convergence is smoothing-scale-dependent, transitioning from Virgo at small scales through the Hydra--Centaurus region at intermediate scales to Shapley at large scales; at intermediate smoothing the convergence point lies near Abell 3565 with an asymmetric basin of mass $\log( M / (h^{-1} \mathrm{M}_\odot)) = 16.4 \pm 0.1$ that excludes Norma. To address the third question, we evolve the Manticore-Local realisations to scale factor $a = 10$ in a new Beyond-Present-Time simulation suite and identify the asymptotic future location of the Local Group. We find that the dominant motion is towards Virgo, but even it contributes at most one third of the Local Group velocity. Our results demonstrate that the classical Great Attractor is not a dynamically dominant structure but an artifact of the instantaneous velocity field, and that no single attractor is likely to account for the Local Group motion in the cosmic rest frame.
It's Stephen Hawking's birthday. The occasion to share this fantastic video he produced as part of his Genius documentatry series. Hawking elaborates on our place in the Universe, including our membership to the Laniakea supercluster of galaxies that we discovered back in 2014.
The complete documentary: https://www.pbslearningmedia.org/resource/hawking_genius_ep06_full/where-are-we-full-episode-genius-by-stephen-hawking/
#StephenHawking #Cosmology #Laniakea #LaniakeaSupercluster #galaxies #astrodon #astronomy #astrophysics #science #cosmography
The Unapologetic Vatican in the Shapley Supercluster
In 1992, the Vatican admitted that Galileo Galilei was right and the Earth is not at the center of the Universe. This was a bit late, 350 years after Galileo died and 33 years after humans landed on…
YOU ARE YOUAREHERE HERE
yellow structure depicted is the Laniakea Supercluster, a vast cosmic region that houses approximately 100,000 galaxies. The red dot in the image represents our home, the Milky Way, which boasts...
Nature - Volume 513 Issue 7516, 4 September 2014
A slice through the Laniakea supercluster — home: velocity flow streams within our supercluster are shown white, external flows dark blue. The Milky Way...
La🌓upla Diplomática
Daniel Pomarède
Francis Mangion (M)
