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    COMMANCHEDobyvani vesmiru a kosmonautika 🚀🛰️👩🏼‍🚀
    CLUMP
    CLUMP --- ---
    LEGI: Stin doury ma mit 40 miliard km, pokud to ma BBC spravne, na mobilu se mi to nechce hledat v primarnich zdrojich...

    First ever black hole image released - BBC News
    https://www.bbc.com/news/science-environment-47873592
    LEGI
    LEGI --- ---
    REDGUY: sorry za lama dotaz
    když má ta díra mít napříč 100 miliard km a Voyager je nějakejch 25 miliard km od Slunce, tím pádem by neměl "opustit" tu černou díru, resp. její stín, ale bejt tak v půlce, ne?
    když teda přijmu tuhle dummy srovnávačku
    TOXICMAN
    TOXICMAN --- ---
    LIVE broadcast - Beresheet lands on the Moon Fasten your seatbelts, we are about to land.
    https://www.youtube.com/watch?v=HMdUcchBYRA
    TOXICMAN
    TOXICMAN --- ---
    @TeamSpaceIL

    We are ready for landing!
    Following today’s maneuver Beresheet is again in an elliptical orbit, with its perilune (the closest point to the Moon) only 15-17 km from the moon’s surface and its epilune (the farthest point from the Moon) at 200 km.
    #IsraeltotheMoon #Beresheet
    ESTEN
    ESTEN --- ---
    JAKKILLER: accretion disc. Horky plazma, obihajici rychlosti blizko c.
    ONDRA_99
    ONDRA_99 --- ---
    SEJDA: Vsak jo. Jen rikam, ze pro vetsinu lidi kdyz se rekne "cerna dira", tak si bud nepredtavi z pohledu fyziky nic. Nebo kdyz aspon nejaky zaklady si pamatuje, tak si ji nejspis predstavi jako singularitu. Stejne tak jako si budou myslet ze velke hvezdy sou jen "zvetsene Slunce" a male hvezdy jen "zmensene Slunce" coz tak jednoduchy neni.
    SEJDA
    SEJDA --- ---
    ONDRA_99: nechapu proc by musela kolabovat, uz snad drive bylo ukazano, ze ma li v okoli dostatecne hmotna telesa, rotujici okolo obrovksou rychlosti, muze dochazet k velmi velmi pomalemu kolabovani.
    Nebo dokonce, prileti-li raketa s nepravdepodobnostnim pohonem k cerne dire, muze se stat, ze se na proces kolabovani obrati? :D
    ONDRA_99
    ONDRA_99 --- ---
    REDGUY: Kazdopadne to vypada na zajimave cteni. Bude to idealni na vecer pri cekani na Falcon Heavy. :)
    ONDRA_99
    ONDRA_99 --- ---
    ONDRA_99: A celkove (sem na zacatku toho pdf) jde o to, ze "cerna dira" je hodne obecny a vetsina lidi si pod nim predstavi jen ten jeden konkretni druh. Asi jako kdyz se rekne hvezda, tak si vetsina lidi predstavi Slunce a pak si reknou ze se lisi jen tim jestli je vetsi, nebo mensi.
    ONDRA_99
    ONDRA_99 --- ---
    ATOMIKS: Si precti to pdf. Uz jen abstract to castecne napovida. Ta masa tam v souctu je, ale rozporstreda do obri velikosti. Jde o to, ze kvuli necemu nezkolabovala do singularity (A black hole can use rotation and/or charge to keep from collapsing).
    ATOMIKS
    ATOMIKS --- ---
    no a kde tedy všechna ta slunce jsou, když to má hustotu vzduchu?
    REDGUY
    REDGUY --- ---
    LUDO: No kdyz je rec o supermasivnich, tak to neplati. Ani co se vzniku tyce (zvazujou se i jiny mechanismy vzniku nez zhrouceni hvezdy), ani co se hustoty tyce (viz predchozi zprava).
    LUDO
    LUDO --- ---
    REDGUY: hmm, doteraz som mal za to, ze cierna diera je iba extremnejsie stadium neutronovej hviezdy, a tie su superhuste
    REDGUY
    REDGUY --- ---
    Fun fact: velky cerny diry maji prekvapive nizkou hustotu protoze polomer zalezi ciste na hmotnosti. Z https://arxiv.org/pdf/1312.0340.pdf

    Surprisingly, the average density decreases dramatically for massive black holes. A black hole of 387 million solar masses would have the average density of water and would be comparable to a giant water balloon extending from the sun almost to Jupiter. A black hole of 11 billion solar masses would have the average density of air and would be analogous to a giant air filled party balloon extending 2.5 times farther out than Pluto.

    Takze jestli je xkcd spravne, tak tahle ma hustotu plus minus jako vzduch 8-0

    JAKKILLER
    JAKKILLER --- ---
    TOXICMAN: Hm, ted o tom vedu debatu s otcem. Je to accretion disc nebo je to zareni z casti galaxie ktera je za M87? Tady - https://eventhorizontelescope.org/- jsem nasel jsem tohle: "Scientists have obtained the first image of a black hole, using Event Horizon Telescope observations of the center of the galaxy M87. The image shows a bright ring formed as light bends in the intense gravity around a black hole that is 6.5 billion times more massive than the Sun. This long-sought image provides the strongest evidence to date for the existence of supermassive black holes and opens a new window onto the study of black holes, their event horizons, and gravity. Credit: Event Horizon Telescope Collaboration

    ESTEN
    ESTEN --- ---
    ATOMIKS: Kdyz uz, tak s popiskem:

    Figure 4. Top: three example models of some of the best-fitting snapshots from the image library of GRMHD simulations for April 11 corresponding to different spin parameters and accretion flows. Bottom: the same theoretical models, processed through a VLBI simulation pipeline with the same schedule, telescope characteristics, and weather parameters as in the April 11 run and imaged in the same way as Figure 3. Note that although the fit to the observations is equally good in the three cases, they refer to radically different physical scenarios; this highlights that a single good fit does not imply that a model is preferred over others (see Paper V).

    (Fig. 3 je ta "fotka" samotna.)
    HADIAK
    HADIAK --- ---
    sry :)

    ARCHIMEDES
    ARCHIMEDES --- ---
    ARCHIMEDES: Beresheet by měl dosednout mezi 21 a 22h SELČ.
    TOXICMAN
    TOXICMAN --- ---
    Accretion flow onto a Kerr Black Hole and Raytraced Emission
    https://www.youtube.com/watch?v=XmvpKFSvB7A
    Kliknutím sem můžete změnit nastavení reklam