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Speaking as an astronomer: what an oddly pointless (even misleading) press release. Non-expert readers could be forgiven for reading that and thinking this is
by Keysh 3y ago
Speaking as an astronomer: what an oddly pointless (even misleading) press release.
Non-expert readers could be forgiven for reading that and thinking this is some sort of "discovery" ("Hubble observes something new and unusual!"), that the forbidden emission lines only appear in Type 2 Seyfert galaxies ("The spectral lines that Type-2 Seyfert galaxies emit are associated with specific 'forbidden' emission lines."), and that they only come from the active nucleus ("in the midst of an incredibly energetic galactic core"). But none of that is true.
Forbidden emission lines are ubiquitous in astronomy. Any time you see an object with emission lines, some of the emission will be forbidden. So we see forbidden emission lines from Seyfert 2 nuclei, from Seyfert 1 nuclei, from quasars, from non-Seyfert nuclei, from the nebula of star-forming regions, from planetary nebulae, from supernova remnants...
You could pick literally any spiral galaxy that Hubble has observed and title the image "Hubble sights a galaxy with 'forbidden light'", and the title would be just as correct. Or swap "nebula" for "galaxy" and use any Hubble image of a nebula in our own galaxy. (There's even forbidden emission coming from the solar corona.)
- kekebo 3y agoThe type of comment I come to hn for. Thanks for clarifying
- adastra22 3y agoWow this was a press release. I assumed at first this was just bog-standard terrible journalism. But no, this was written by NASA Goddard... I have a physics degree and I still don't understand what "forbidden spectra" meant according to this article.
- Keysh 3y agoIt actually says it was written by the European Space Agency, for what that’s worth.
- aeternum 3y agoWhat is the source of the energy for this 'forbidden' light? Is it from the rotational energy of the black hole?
- Keysh 3y agoIndividual atoms or ions can be excited to "meta-stable" states, from which they can decay via emission of forbidden light, by other photons (usually X-ray or UV) or by energetic collisions with other particles. It has nothing to do with black holes, except that accretion disks around black holes can, due to their high temperature, produce the necessary energetic photons. (But so can massive stars, for example.) The rotational energy of the black hole is not involved.