Skeptophilia (skep-to-fil-i-a) (n.) - the love of logical thought, skepticism, and thinking critically. Being an exploration of the applications of skeptical thinking to the world at large, with periodic excursions into linguistics, music, politics, cryptozoology, and why people keep seeing the face of Jesus on grilled cheese sandwiches.

Thursday, May 23, 2024

Vanishing act

In Madeleine L'Engle's seminal young-adult fantasy novel The Wind in the Door, there's something that is making the stars go out.

Not just stop shining, but disappear entirely.  Here's the scene where the protagonist, Meg Murry, first witnesses it happening:
The warm rose and lavender of sunset faded, dimmed, was extinguished.  The sky was drenched with green at the horizon, muting upwards into a deep, purply blue through which stars began to appear in totally unfamiliar constellations.

Meg asked, "Where are we?"

"Never mind where.  Watch."

She stood beside him, looking at the brilliance of the stars.  Then came a sound, a violent, silent, electrical report, which made her press her hands in pain against her ears.  Across the sky, where the stars were clustered as thickly as in the Milky Way, a crack shivered, slivered, became a line of nothingness.

Within that crack, every star that had been there only a moment ago winked out of existence.
A central point in the story is that according to the laws of physics, this isn't supposed to happen.  Stars don't just vanish.  When they end their lives, they do so in an obvious and violent fashion -- even small-mass stars like the Sun swell into a red giant, and eventually undergo core collapse and blow off their outer atmospheres, creating a planetary nebula.  

The Cat's Eye Nebula [Image is in the Public Domain courtesy of NASA/JPL and the ESO]

Larger stars end their lives even more dramatically, as supernovas which lead to the formation of a neutron star or a black hole depending on how much matter is left over once the star blows up.

Well, that's what we thought always happened.

A study out of the University of Copenhagen has found that like in A Wind in the Door, sometimes stars simply... vanish.  A team of astrophysicists has found that instead of the usual progression of Main Sequence > Giant or Supergiant > BOOM! > White Dwarf, Neutron Star, or Black Hole, there are stars that undergo what the astrophysicists are (accurately if uncreatively) calling "complete collapse."  In a complete collapse, the gravitational pull is so high that even considering the power of a supernova, there's just not enough energy available for the outer atmosphere to achieve escape velocity.  So instead of exploding, it just kind of goes...

... pfft.

Unlike what Meg Murry witnessed, though, the matter that formed those stars is still there somewhere; the Law of Conservation of Matter and Energy is strictly enforced in all jurisdictions.  The star that was the focus of the study, VFTS 243, is part of a binary system -- and its companion star continued in its original orbit around their mutual center of mass without so much as a flutter, so the mass of its now-invisible partner is still there.  But the expected cataclysmic blast that usually precedes black hole formation never happened.

"We believe that the core of a star can collapse under its own weight, as happens to massive stars in the final phase of their lives," said Alejandro Vigna-G√≥mez, who co-authored the study.  "But instead of the contraction culminating into a bright supernova explosion that would outshine its own galaxy, expected for stars more than eight times as massive as the Sun, the collapse continues until the star becomes a black hole.  Were one to stand gazing up at a visible star going through a total collapse, it might, just at the right time, be like watching a star suddenly extinguish and disappear from the heavens.  The collapse is so complete that no explosion occurs, nothing escapes and one wouldn't see any bright supernova in the night sky.  Astronomers have actually observed the sudden disappearance of brightly shining stars in recent times.  We cannot be sure of a connection, but the results we have obtained from analyzing VFTS 243 has brought us much closer to a credible explanation."

You can see why I was immediately reminded of the scene in L'Engle's book.  And while I'm sure the answer isn't evil beings called Echthroi who are trying to extinguish all the light in the universe, the actual phenomenon is still a little on the unsettling side.

Once again showing that we are very far from understanding everything there is out there.  This sort of vanishing act has been high on the list of Things That Aren't Supposed To Happen.  It'll be interesting to see what the theorists propose with when they've had a shot at analyzing the situation, and if they can come up with some sort of factor that determines whether a massive star detonates -- or simply disappears.

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