[HN Gopher] The seven hour explosion nobody could explain
       ___________________________________________________________________
        
       The seven hour explosion nobody could explain
        
       Author : mellosouls
       Score  : 71 points
       Date   : 2026-03-17 11:14 UTC (4 days ago)
        
 (HTM) web link (phys.org)
 (TXT) w3m dump (phys.org)
        
       | comrade1234 wrote:
       | tldr: it was the office microwave.
       | 
       | (just kidding - probably a black hole)
        
         | Sharlin wrote:
         | You're referring to [1] which is certainly a fun (and
         | instructive) story. But FRBs are pretty much the exact opposite
         | to seven-hour events.
         | 
         | [1] https://www.nature.com/nature-index/news/its-the-
         | microwave-h...
        
           | b112 wrote:
           | A black hole is, but what if something big fell into it?
        
       | purplejacket wrote:
       | The paper on which the article is based,
       | 
       | https://watermark02.silverchair.com/stag328.pdf?token=AQECAH...
       | 
       | mentions 3 three alternative interpretations for GRB 250702B:
       | 
       | 1. Ultralong Collapsars: These stellar-engine models can explain
       | long durations but struggle to account for the specific timing of
       | this event. Specifically, they cannot easily produce a 12-hour
       | gradual rise in X-rays followed by a multi-hour peak, as the jet
       | would have to fight through a massive progenitor star while its
       | power is still very low.
       | 
       | 2. White Dwarf (WD) Tidal Disruptions: While an Intermediate Mass
       | Black Hole (IMBH) disrupting a White Dwarf could theoretically
       | provide the necessary gravity, the numbers do not add up for this
       | specific burst. The timing between flares is too long for a WD
       | scenario, and the total energy required would demand an
       | unrealistically narrow jet. When physical constraints like
       | detonation are factored in, this model is considered highly
       | unlikely.
       | 
       | 3. Micro-TDEs (Main Sequence star by a stellar-mass BH/NS): This
       | is considered a competitive alternative that can explain the
       | burst's sub-second variability and long duration. However, it
       | faces two main issues: current afterglow data suggests the
       | surrounding gas density matches an IMBH environment better than a
       | micro-TDE environment, and the burst's extreme energy would
       | require very high jet efficiency or a very narrow beam.
        
       | carlsborg wrote:
       | 3I/ATLAS first detected on: July 1 2025
       | 
       | Gamma ray burst that kept going for seven hours, fired three
       | distinct bursts spread across an entire day: July 2 2025
       | 
       | just saying
        
         | EA-3167 wrote:
         | This event originated in a different galaxy.
        
       | saltcured wrote:
       | If this were a scifi horror story, it would be that there was a
       | high energy event so far away and so long ago that the protracted
       | duration is due to red-shift. Those X-rays were actually
       | unimaginably higher energy particles and the duration of the
       | event was also brief but has gotten smeared over time by
       | inflation.
        
         | btilly wrote:
         | That's actually not possible due to something called the GZK
         | cutoff. Which is a weird phenomena that causes apparently empty
         | space to turn somewhat cloudy for sufficiently high energy
         | photons. Here is how it works.
         | 
         | If an electron and a positron meet, they turn into two very
         | high energy photons.
         | 
         | Because physics is time reversible, if two high energy photons
         | meet, they have a chance to turn into an electron-positron
         | pair.
         | 
         | If an extremely high energy photon meets a low energy one,
         | there is a moving reference frame in which they have the same
         | energy, and are both high energy. Therefore they have a chance
         | to turn into an electron-positron pair whose center of mass is
         | in that reference frame.
         | 
         | The result is that if a photon is above something like 10^15 eV
         | in energy, it can annihilate itself against any photon in the
         | cosmic microwave background radiation (CMBR). There are lots of
         | photons in the CMBR. Those collisions are sufficiently likely
         | that such photons essentially cannot travel intergalactic
         | distances.
         | 
         | If you go back to the early universe, the CMBR was much denser
         | than it is today. Making the distance that such photons could
         | reasonably travel even shorter then than it is today.
         | 
         | That said, no good storyteller should let inconvenient physical
         | fact keep them from writing a good story.
        
       ___________________________________________________________________
       (page generated 2026-03-21 23:00 UTC)