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Monday, May 16, 2016

Likely Exocomets: Closing In on 'Alien Megastructure' Clues


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Likely Exocomets: Closing In on 'Alien Megastructure' Clues


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Artist’s impression of star KIC 8462852 shows the fragments of a comet orbiting the star, and periodically blocking the light.
NASA/JPL-CALTECH


After all the kerfuffle surrounding a certain star scrutinized by NASA’s Kepler Space Telescope last October, astronomers have been feverishly trying to find a, um, natural explanation for a bizarre transit signal. Though it has turned into something of an epic endeavor, astronomers are zeroing in on the most likely candidate.
You know the story: Kepler is used to detect the transit of exoplanets around other stars. Its strength is that it can detect the very faint dip in starlight of astonishingly small worlds of Earth-like dimensions (and smaller) at tens to hundreds of light-years distant. The Kepler database is crazy-big, so to help astronomers identify transit signals, the crowd-sourcing group Planet Hunters delves into the signals.
One signal, originating from a star designated KIC 846852 — which was eventually nicknamed “Tabby’s Star” after discoverer Tabetha S. Boyajian — was dramatic. And by dramatic I mean unprecedented: A series of transit signals caused the star’s brightness to dip up to 20 percent. For a mission that deals in transits that usually dim starlight by fractions of a percent, you can see why this signal caused a stir.
Most interestingly, this signal was confirmed to be real, so it wasn’t instrumental or analysis error, so astronomers started working on possible explanations. It wasn’t long before the “alien” card was pulled and the world’s media latched on — was this the first direct evidence of an advanced alien civilization building some kind of “megastructure” around their host star? Could this be the first evidence of a partially built “Dyson Sphere”? Science fiction fans rejoiced! (Tentatively.) I, for one, welcomed our neighboring extraterrestrial architects and their can-do attitude.
But scientists being the buzzkills that they are were already pointing their fingers at other, more plausible explanations — no aliens required.
One idea centered round the possibility of a planetary collision. Although the likelihood of us looking in the right place at the right time to see the exo-smashup was very slim, just because we were lucky, it didn’t mean it didn’t happen. Another idea focused around a vast swarm of comets blotting out the star from our viewpoint. Indeed, the latter explanation had some meat as there was another nearby star that could have destabilized Tabby’s Star’s Oort Cloud (the region surrounding a star that is thought to harbor countless billions of ancient icy bodies waiting to be knocked off their gravitational perch and fall through the inner star system).
Now, in research from Harvard-Smithsonian Center for Astrophysics, astronomers have studied Tabby’s star using the Submillimeter Array and the James Clerk Maxwell Telescope, located atop Mauna Kea in Hawaii, in an effort to possibly track down dust associated with a planetary collision. The warm dust that would be produced by such an event should glow in emissions at submillimeter and millimeter wavelengths.
They found none.
Though the signal of some warm dust in the system may not be detectable (as the signal is so weak), this null result puts some tough restraints on the amount of dust in the system. There’s simply not enough dust there to support the collision hypothesis, but might be consistent with a complete breakup of 30 massive Halley-like comets blocking the starlight from view.
But just because the exocomet idea has been reinforced, it’s not easy for astronomers to explain why dozens of comets happened to disintegrate; there is no simple or known mechanism that would do that. Interestingly, this new finding doesn’t necessarily disprove the megastructure hypothesis either, but in the interest of Occam’s Razor, a cloud of strange comets would certainly be a simpler explanation than an advanced extraterrestrial civilization doing some DIY around a nearby star.
So the message is becoming clear: we’re not saying it’s not aliens; it’s just the exocomet hypothesis is becoming more likely.

Hawking: Earth (Likely) Doomed, Humanity Needn't Be


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Hawking: Earth (Likely) Doomed, Humanity Needn't Be

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An artist's impression of a human colony on Mars -- could this be the answer to safeguarding our species?
CORBIS


The thing with Stephen Hawking is that the world tends to listen when he discusses big ideas.


Not content with informing us that God does not exist or that we could be wiped out by an alien invasion, the British physics superstar has now gone on the record to say humanity will score the mother of all “own goals” in the future. And that, he argues, is an excellent reason for getting humanity off the planet.
“Although the chance of a disaster to planet Earth in a given year may be quite low, it adds up over time, and becomes a near certainty in the next thousand or ten thousand years,” Hawking said during his first BBC Reith Lecture, that will be aired on Jan. 26. “By that time we should have spread out into space, and to other stars, so a disaster on Earth would not mean the end of the human race.
“However, we will not establish self-sustaining colonies in space for at least the next hundred years, so we have to be very careful in this period.”
Hawking argues that this statistical near-certainty of doom over the next few centuries will most likely be self inflicted. Of the most likely candidates he singles out are the usual suspects: nuclear war, global warming and genetically engineered superviruses.
Previously, Hawking has also warned about advances in artificial intelligence turning against humanity — a fear that is shared by other prominent figures, including SpaceX and Tesla founder Elon Musk.
But there is hope, fortunately.
“We are not going to stop making progress, or reverse it, so we have to recognize the dangers and control them,” he said. “I’m an optimist, and I believe we can.”

It may not sound very optimistic to be identifying all the weird and wonderful ways we’ll likely be made extinct, but with this knowledge perhaps we can avert the worst cataclysms we could inflict on ourselves in the future. Failing that, argues Hawking, we should really focus our efforts on space exploration and spreading humanity to the solar system and (possibly) beyond. The Earth may be doomed, but humanity needn’t be.
I can really get behind Hawking’s recurring message, urging us to explore space and I share some of his optimism for humanity. Space exploration, particularly the opportunities private rocket companies are showing us, getting stuff into space is getting easier and more affordable. Elon Musk even has long-term plans to set up a SpaceX-driven colony on Mars. A decade ago that would have been pure fantasy, but with the uptick in amazing rocket technology breakthroughs in recent years, it no longer sounds like an impossibility — though there’s still a very long way to go.
That said, Hawking’s warnings shouldn’t be seen as “just another” doomsday theory. Identifying the biggest threats, particularly the ones we could inflict on ourselves, will be key to helping us avoid them in the future.
I’m actually more pessimistic than Hawking about humanity’s ability of avoiding or fixing damage caused to our planet. Only now are we making serious moves to slow our emissions of greenhouse gases, when it’s already too late for many island nations that are being swamped by sea level rise. Irreversible damage has been caused to our planet by our persistent nature to grow and exploit its natural resources. It’s going to take the biggest ideas from the world’s brightest minds to think up geoengineering projects that could safeguard our future.
But in the meantime, why keep all our eggs in one basket? For better or worse, it’s never been a better time to push into space, possibly seeding new worlds — starting with Mars — with life.