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The BBC's Milky Way's centre exploded 3.5 million years ago says:

A cataclysmic energy flare ripped through our galaxy, the Milky Way, about 3.5 million years ago, a team of astronomers say.

They say the so-called Sifter flare started near the super massive black hole in the centre of the galaxy.

The impact was felt 200,000 light-years away.

[...]The flare created two enormous "ionisation cones" that sliced through the Milky Way.

It mentions "The team - led by Professor Joss Bland-Hawthorn from Australia" and "co-author Magma Guglielmo from the University of Sydney" and says "The findings will be published in the Astrophysical Journal."

Right now I'm just asking the following:

Question: Who is Sifter, and what is "the so-called Sifter flare"?


update: @bertieb's comment notes that the BBC has corrected the passage. The new sentence says:

The so-called Seyfert flare started near the supermassive black hole in the centre of the galaxy, they add.

When first published, the article called it a "so-called Sifter flare" and that's what originally inspired this question.

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    $\begingroup$ For what it's worth, the BBC article has been updated as of this comment :) $\endgroup$ – bertieb Oct 7 '19 at 13:00
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    $\begingroup$ Another news item about the same event. Carl Seyfert (1911-1960) was a US astronomer ..."is best known for his 1943 research paper on high-excitation line emission from the centers of some spiral galaxies, which are named Seyfert galaxies after him". $\endgroup$ – Fred Oct 7 '19 at 15:01
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    $\begingroup$ A bit more info on Active galactic nucleus $\endgroup$ – Fred Oct 7 '19 at 15:04
  • $\begingroup$ @bertieb thanks for that! I've updated the question accordingly. $\endgroup$ – uhoh Oct 8 '19 at 3:07
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As has now been corrected, BBC has misunderstood term "Seyfert flare", instead calling it a "Sifter flare".


A "Seyfert flare", is not really a common term, but the authors refer to an energetic outburst from the type of active galaxies called Seyfert galaxies (after Carl Seyfert).

Like a quasar, a Seyfert galaxy is powered by gas accretion onto a central, supermassive black hole, although they're less luminous by roughly two orders of magnitude.

In this case, there is evidence for a highly energetic ($10^{56\text{-}57}\,\mathrm{erg}$) explosion occurring only a few million years ago, resulting a an ionizing, bipolar cone extending outward from the Milky Way's central black hole, Sgr A*.

This powerful flare resulted in huge, 10 kpc-scale, X-ray/gamma-ray-emitting bubbles. The line ratios of $\mathrm{C\,IV}/\mathrm{C\,II}$ and $\mathrm{Si\,IV}/\mathrm{Si\,II}$ points toward ionizing radiation energies of at least 50 eV.

The orientation of these cones is seen in this figure from the paper, which will be on the arXiv tomorrow. The first-author, Joss Bland-Hawthorn, explains in a video here.

enter image description here

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Answering the who is part of the question.

Carl Seyfert (1911-1960) was a US astronomer.

He is best known for his 1943 research paper on high-excitation line emission from the centers of some spiral galaxies, which are named Seyfert galaxies after him. Seyfert's Sextet, a group of galaxies, is also named after him.

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  • $\begingroup$ Thanks for the additional information! $\endgroup$ – uhoh Oct 8 '19 at 16:24

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