Stars Caught in Fiery Merger

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In 2002, astronomers witnessed one of the strangest celestial events ever. A star on the outskirts of our Milky Way briefly grew one million times brighter, outshining almost all other stars in our galaxy. It didn’t explode as a supernova, but just sort of hiccuped a brilliant burst of light.

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The star, called V838 Monocerotis, expanded to an enormous size, cooled and reddened (above). Since then razor-sharp Hubble Space Telescope pictures have caught the eerie “light echo” around the star as the glow from the flash rebounds off of interstellar dust. This phenomenon gives the illusion that material is streaming off the star as velocities faster than the speed of light.

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Astronomers remain at a loss to satisfactorily explain the outburst, but there has been lots of speculation. Did the star ignite helium at the core, swallow a planet, or swallow a companion star?

In September 2008, another strange stellar burst was seen deep in the heart of the Milky Way, 10,000 light-years away in the opposite direction of V838 Mon.

Called V1309 Scorpii, it too would have joined the “stellar weirdo” list if not for a fortuitous observation that caught the pre-disaster activity — like a shopping mall security camera recording a crime from start to finish.

Our galactic surveillance camera is the nearly two decade-long Optical Gravitational Lensing Experiment (OGLE), that looks for small changes in the brightness of tens of millions of stars in the direction of the galactic center.

A major goal of the project is to capture gravitational microlensing events where an unseen body passes between a background star and Earth. This causes the background star to momentarily brighten as the gravitational field of the foreground object amplifies the starlight like a magnifying glass. Light changes can also be caused by intrinsically variable stars, and planets passing in front of stars.

From 2001 to 2008 the OGLE survey made over 1,300 observations of the orange dwarf star before it blew its top in 2008. The star just happened to be in the field of view.

The survey shows that the star oscillated in brightness for years before the brilliant flash. Mysteriously the oscillation period was first measured at 1.4 days but grew shorter leading up to the 2008 blowout.

It’s unlikely the variability could have been caused by star spots coming and going. A 1.4-day period would not remain so stable for so long. Like sunspots, starspots should change in size and migrate. It’s also unlikely the star was pulsating because the oscillation rate got shorter over a several year period.

The best explanation is that actually two stars were seen orbiting edge-on to our line of sight. The amount of light from the system would momentarily drop every time one star passed behind the other. If the stars were spiraling together the orbital period would shorten, as observed.

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The fast orbit meant that double star system was an unusual “contact binary” where a pair of stars are so close together they are nearly touching each other and share a common coronal envelope — like a pair of waltzing skaters whirling around each other rapidly. Friction between the two stars would put drag on the system, and rob orbital momentum, causing the stars to get closer to each other.

When the stars merged all hell broke loose. The momentum from the orbit was converted to heat, causing the new merged star to skyrocket in temperature. The star also suddenly grew 10,000 times brighter.

WIDE ANGLE: Massive Cosmic Explosions

Imagine for a moment that the contact binary had an inhabited planet with an advanced civilization. Its astronomers would have noted the shortening orbital period between the binary duo.

This would presage a true apocalypse for the civilization. Anticipation would be reminiscent of today’s “2012″ silly doomsday hysteria, except this would be for real. Astronomers would realize that the inevitable merger would incinerate the surface of their planet, perhaps boil away its oceans, and strip away the atmosphere. They would have a real doomsday clock the counted down each shrinkage of the binary’s orbital period.

ANALYSIS: Why Does a Star Explode?

A space ark with a small population of refuges might be dispatched to find shelter on a moon of one of the system’s gas giant outer planets. That is, assuming the merged star did swell up big enough to devour the entire system, as V838 Mon has done.

At the right distance, they would be in a newly expanded habitable zone around the swelled-up star.

The civilization’s political and social upheaval would be unimaginably severe because only a fraction of the global population of planet could be saved. Independent nations would embark on a technological “survival-race” to see how many citizens could be launched off the planet. The 1933 science fiction novel “When Worlds Collide,” presents just such a scenario.

Those left on the doomed planet might gamble to set up survival habitats in deep underground caverns with air, water and food processing capabilities.

This is also reminiscent of the projection of a post-nuclear holocaust underground shelters envision in the 1964 dark-comedy film, “Dr. Strangelove“:

U.S. President: “Well I… I would hate to have to decide.. who stays up and.. who goes down.”

Dr. Strangelove: “ . . .a computer could be set and programmed to accept factors from youth, health, sexual fertility, intelligence, and a cross section of necessary skills. Of course it would be absolutely vital that our top government and military men be included to foster and impart the required principles of leadership and tradition.”

Artwork credit: ESO

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