In pop astronomy circles—yes, such things do exist—the ostensible
standard-bearer for high-energy phenomena is the supernova, a massive stellar
explosion that effectively destroys entire stars. Supernovae garner a lot of well-deserved
hype because they’re not only among the most luminous events known to humankind,
but they’re also the “engines” that create nearly all of the complex
elements found in the universe (read: anything with an atomic number higher
than eight, as in oxygen). That’s not too bad for an also-ran.
While supernovae certainly put out astronomical (pun
intended) levels of energy, they pale in comparison to the most luminous and
energetic phenomena known to science: gamma ray bursts (GRBs). GRBs are several
thousand times more luminous and energetic than supernovae.
Gamma rays are the highest energy form of radiation—effectively,
the “brightest” kind of light in the sky. So it’s not surprising that
a cosmic-level burst of gamma rays would rate higher on the astronomic
“wow” scale than even a supernova.
What is surprising
about GRBs is that they’re an almost daily event—researchers observe at least
300 or so GRBs in any given year. Yet science has no clear idea where they come
from.
That’s like having a full-scale fireworks show above your
house everyday but not knowing who’s launching those skyrockets. The GRBs literally
appear in the sky at random, lighting off massive displays of energy that last
mere seconds—with effects that dissipate completely in hours.
In many ways, GRBs are among the most compelling mysteries
confronting astrophysics. They are also among the most frustrating.
GRBs are virtually invisible to earthbound instrumentation.
That’s because the earth’s atmosphere screens out most gamma rays (lucky for
us, too).
Scientists didn’t even know GRBs existed until the late
1960s, when the United States launched the Vela satellite project to search for
clandestine nuclear testing on Earth. What the Vela satellites picked up were
massive, random, unexplained bursts of gamma rays that astronomers eventually
realized were coming from deep space.
In the decades since, astrophysicists have tried to
determine the origin of GRBs, and a compelling candidate is a special breed of—you
guessed it—supernovae.
WHAT SPECIAL BREED OF SUPERNOVAE DO ASTROPHYSICISTS CONSIDER
TO BE A LIKELY SOURCE FOR UNEXPLAINED GAMMA RAY BURSTS?
What special breed of supernovae do astrophysicists consider
to be a likely source for gamma ray bursts (GRBs), the most luminous cosmic
event known to science whose origins have eluded astrophysicists for nearly
four decades?
What do you call a really, really powerful supernova? A hypernova, of course. What differentiates
a hypernova from a mere supernova is both the size of the star that’s blowing
up and the type of celestial object the remains of the star become.
In the case of a hypernova, a giant star collapses directly
into a black hole—do not pass Go, do not collect $200. During this cosmic squeeze
play, the collapsing star spews out jets of highly energetic plasma from each
of its poles. These plasma jets contain staggering amounts of gamma rays, and
that’s what makes hypernovae a compelling candidate for the source of GRBs.
Of course, as usual, there’s a caveat. Giant stars are statistically
rare, and giant stars that collapse directly into black holes are rarer still, but
GRBs are eerily commonplace. Thus, either hypernovae are not the sole source of
GRBs, or scientists have greatly underestimated the frequency of black hole formation.
On the subject of GRB commonality—you know you’re in Geek
Territory when you read a sentence like that—it’s safe to say that the Milky
Way has not hosted a GRB in quite a long time. Be thankful: The level of lethal
gamma rays emitted by a “local” GRB—say, any burst occurring within
the more than 100,000 light-year diameter of our galaxy—would probably be
enough to poison every living thing on earth. (And before you ask, yes,
scientists have theorized a localized GRB as a potential cause of the extinction
of the dinosaurs.)
The good news is that the Milky Way is unlikely to see any
native GRB anytime soon, as GRBs appear to be native to distant star-forming
regions at the edge of the universe. Perhaps GRBs and the hypernovae that might
cause them are merely a symptom of galactic adolescence, the growing pains of a
young galaxy that the venerable Milky Way has long since outgrown. If so, we
may be so fortunate as to never experience a GRB up close and personal—except,
of course, in the mysterious realms of Geek Trivia.
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The Trivia Geek, also
known as Jay Garmon, is a former advertising copywriter and Web developer who’s
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