Tag Archives: Kepler

Cosmology

Tabby’s Star

KIC_8462852_in_IR_and_UV

Tabby’s Star, officially known by the cryptic notation KIC 8462852 is a very odd object. The star is around 1,500 light years from Earth, and has been puzzling astronomers with its strangely fluctuating brightness. Recent analysis shows that is even weirder than first thought, which has scientists baffled. Could the observations be caused by a storm of wildly orbiting comets? Or, much more compelling (for SciFi buffs), could it be an alien megastructure periodically shrouding the star?

From Space:

KIC 8462852 was observed by NASA’s Kepler mission and has become infamous for its bizarre and unprecedented transit signal that was flagged by citizen scientists. Now new research of precision Kepler observations has shown that the overall brightness of the star — unofficially named “Tabby’s Star” after astronomer Tabetha S. Boyajian who discovered the peculiar signal — has been decreasing, which poses a new and confusing problem for astronomers trying to understand what the heck is going on.

Kepler’s prime mission is to look for small worlds that pass in front of their parent stars causing a slight dimming of starlight. The “transit method” has been hugely successful and has confirmed well over 2,000 planets orbiting other stars in our galaxy.

But Tabby’s Star’s transit signal, otherwise known as a “light-curve”, stopped astronomers in their tracks. Something passed in front of it, dimming its starlight a whopping 20 percent and other jumbled transit signals revealed that something wasn’t quite right with this particular star. Then, in an interview with The Atlantic, Penn State University astronomer Jason Wright speculated that the signal could be indicative of an “alien megastructure” that’s in the process of being built. You can catch up on the controversy surrounding the anomalous signal in my recent Discovery News article “Closing In on ‘Alien Megastructure’ Clues.”

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So, in an effort to track down a rational explanation, Bradley Schaefer from Louisiana State University decided to study historical observations of KIC 8462852 in astronomical photographic plates from the past century to see if the star exhibited any bizarre fluctuations in brightness in the past. Sure enough, yes, the star is a bit of an oddball and has shown a long-term decreasing trend in brightness! Since the 19th Century, its brightness has decreased steadily by nearly 20 percent.

Now, astronomers Ben Montet (from Caltech) and Joshua Simon (from the Carnegie Institute) have released a paper to the arXiv preprint service detailing recent Kepler observations of KIC 8462852 since the space telescope was launched in 2009. Although the dataset for this time period is comparatively small, Monet and Simon found yet another surprise.

In the 4 years of Kepler’s primary mission, the star showed an unprecedented dimming of 3.5 percent. So not only did Kepler detect transient dips in brightness of up to 20 percent, there also seems to be a very definite downward trend in brightness throughout our observational history of the star.

No matter how you slice it, this is strange.

Read the entire story here.

Image: Tabby’s Star, KIC 8462852, in infrared (2MASS survey) and ultraviolet (GALEX). Courtesy: IPAC/NASA (Infrared), STScI/NASA (Ultraviolet). Public Domain.

BigBang

The Curious Case of the Strange Transit Signal

Something very strange is happening over at KIC 8462852. But, it may not be an alien intelligence.

KIC-8462852–Where-is-the-flux

NASA’s extrasolar, planet-hunting space telescope, found some odd changes in the luminosity of a star — KIC 8462852— located in the constellation of Cygnus, about 1,400 light-years from Earth. In a recent paper submitted to the Royal Astronomical Society, astronomers reported that:

“Over the duration of the Kepler mission, KIC 8462852 was observed to undergo irregularly shaped, aperiodic dips in flux down to below the 20 percent level.”

But despite several years of monitoring, astronomers have yet to come up with a feasible, natural explanation. And, this has conspiracy theorists, alien hunters and SciFi enthusiasts very excited. Could it be a massive alien structure shielding the star, or is there simpler and natural, but less amazing possibility? Occam’s razor could well prevail again, but I certainly hope not in this case.

From Wired:

Last week, astronomers—amateur and pro—got excited about some strange results from the Kepler Space Telescope, the NASA observatory tasked with searching for Earth-like planets. As those planets orbit their own distant suns, periodically blocking light from Kepler’s view, the telescope documents the flickers. But over the last several years, it has picked up a strange pattern of blips from one star in particular, KIC 8462852.

Light from that star dramatically plunges in irregular intervals—not the consistent pattern you’d expect from an orbiting planet. But what could possibly cause such a thing? Gotta be aliens, right? Clearly someone—something—has assembled a megastructure around its sun, like that hollow Celestial head in Guardians of the Galaxy. Or maybe it’s a solar array, collecting energy-giving radiation and preventing light from reaching NASA’s telescope.

This, of course, is almost certainly poppycock. When you’re searching the vast expanse of space, lots of things look like they could be signs of extraterrestrial life. Astronomical observers are constantly looking for tiny glimmers of information in the mess of noise that streams through space toward Earth, and often, things that at first look like signals end up being mirages. This has all happened before; it will all happen again. For example:

Pulsars

In 1967, astronomer Jocelyn Bell was monitoring signals from the Mullard Radio Astronomy Observatory, trying to analyze the behavior of quasars, energy-spewing regions surrounding supermassive black holes within distant galaxies. What she found, though, was a series of regular pulses, always from the same part of the sky, that she labeled LGM-1: Little Green Men. Soon, though, she found similar signals coming from another part of the sky, and realized that she wasn’t seeing messages from two different alien civilizations: It was radiation from a spinning, magnetized neutron star—the first measured pulsar.

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Sparks at Parkes

In 1998, astronomers at the 64-meter Parkes radio telescope in Australia started noticing mysterious radio signals called perytons—unexplained, millisecond-long bursts. The researchers there didn’t immediately cry alien, though; they could tell that the radio signals were terrestrial in origin, because they showed up across the entire spectrum monitored by the telescope. They didn’t know until this year, however, exactly where those emissions came from: a microwave oven on the observatory’s campus, which released a short, powerful radio signal when staffers opened its door in the middle of heating.

Read the entire story here.

Image: Flux time series for KIC 8462852 showing different portions of the 4-year Kepler observations. Courtesy: T. S. Boyajian et al, Planet Hunters X. KIC 8462852 – Where’s the flux?

 

 

Art, BigBang

Exotic Exoplanets Await Your Arrival

NASA_kepler16b_poster

Vintage travel posters from the late 1890s through to the 1950s colorfully captured the public’s imagination. Now, not to be outdone by the classic works from the Art Nouveau and Art Deco periods, NASA has published a series of its own. But, these posters go beyond illustrating alpine ski resorts, sumptuous hotels and luxurious cruises. Rather, NASA has its sights on exotic and very distant travels — from tens to hundreds of millions of light-years. One such spot is the destination Kepler-16.

Kepler-16 A/B is a binary star system in the constellation of Cygnus that was targeted for analysis by the Kepler exoplanet hunting spacecraft. The star system is home to a Saturn-sized planet Kepler 16b orbiting the red dwarf star, Kepler 16-B, and  is 196 light-years from Earth.

See more of NASA’s travel posters here.

 

BigBang

Revisiting Drake

In 1960 radio astronomer Frank Drake began the first systematic search for intelligent signals emanating from space. He was not successful, but his pioneering efforts paved the way for numerous other programs, including SETI (Search for Extra-Terrestrial Intelligence). The Drake Equation is named for him, and put simply, gives an estimate of the number of active, extraterrestrial civilizations with methods of communication in our own galaxy. Drake postulated the equation as a way to get the scientific community engaged in the search for life beyond our home planet.

The Drake equation is:

N = R^{\ast} \cdot f_p \cdot n_e \cdot f_{\ell} \cdot f_i \cdot f_c \cdot L

where:

N = the number of civilizations in our galaxy with which communication might be possible (i.e. which are on our current past light cone); and

R* = the average number of star formation per year in our galaxy

fp = the fraction of those stars that have planets

ne = the average number of planets that can potentially support life per star that has planets

fl = the fraction of planets that could support life that actually develop life at some point

fi = the fraction of planets with life that actually go on to develop intelligent life (civilizations)

fc = the fraction of civilizations that develop a technology that releases detectable signs of their existence into space

L = the length of time for which such civilizations release detectable signals into space

Now, based on recent discoveries of hundreds of extra-solar planets, or exoplanets (those beyond our solar system), by the Kepler space telescope and other Earth-bound observatories, researchers are fine-tuning the original Drake Equation for the 21st century.

From the New Scientist:

An iconic tool in the search for extraterrestrial life is getting a 21st-century reboot – just as our best planet-hunting telescope seems to have died. Though the loss of NASA’s Kepler telescope is a blow, the reboot could mean we find signs of life on extrasolar planets within a decade.

The new tool takes the form of an equation. In 1961 astronomer Frank Drake scribbled his now-famous equation for calculating the number of detectable civilisations in the Milky Way. The Drake equation includes a number of terms that at the time seemed unknowable – including the very existence of planets beyond our solar system.

But the past two decades have seen exoplanets pop up like weeds, particularly in the last few years thanks in large part to the Kepler space telescope. Launched in 2009Movie Camera, Kepler has found more than 130 worlds and detected 3000 or so more possibles. The bounty has given astronomers the first proper census of planets in one region of our galaxy, allowing us to make estimates of the total population of life-friendly worlds across the Milky Way.

With that kind of data in hand, Sara Seager at the Massachusetts Institute of Technology reckons the Drake equation is ripe for a revamp. Her version narrows a few of the original terms to account for our new best bets of finding life, based in part on what Kepler has revealed. If the original Drake equation was a hatchet, the new Seager equation is a scalpel.

Seager presented her work this week at a conference in Cambridge, Massachusetts, entitled “Exoplanets in the Post-Kepler Era”. The timing could not be more prescient. Last week Kepler suffered a surprise hardware failure that knocked out its ability to see planetary signals clearly. If it can’t be fixed, the mission is over.

“When we talked about the post-Kepler era, we thought that would be three to four years from now,” co-organiser David Charbonneau of the Harvard-Smithsonian Center for Astrophysics said last week. “We now know the post-Kepler era probably started two days ago.”

But Kepler has collected data for four years, slightly longer than the mission’s original goal, and so far only the first 18 months’ worth have been analysed. That means it may have already gathered enough information to give alien-hunters a fighting chance.

The original Drake equation includes seven terms, which multiplied together give the number of intelligent alien civilisations we could hope to detect (see diagram). Kepler was supposed to pin down two terms: the fraction of stars that have planets, and the number of those planets that are habitable.

To do that, Kepler had been staring unflinchingly at some 150,000 stars near the constellation Cygnus, looking for periodic changes in brightness caused by a planet crossing, or transiting, a star’s face as seen from Earth. This method tells us a planet’s size and its rough distance from its host star.

Size gives a clue to a planet’s composition, which tells us whether it is rocky like Earth or gassy like Neptune. Before Kepler, only a few exoplanets had been identified as small enough to be rocky, because other search methods were better suited to spotting larger, gas giant worlds.

“Kepler is the single most revolutionary project that has ever been undertaken in exoplanets,” says Charbonneau. “It broke open the piggybank and rocky planets poured out.” A planet’s distance from its star is also crucial, because that tells us whether the temperature is right for liquid water – and so perhaps life – to exist.

But with Kepler’s recent woes, hopes of finding enough potentially habitable planets, or Earth twins, to satisfy the Drake equation have dimmed. The mission was supposed to run for three-and-a-half years, which should have been enough to pinpoint Earth-sized planets with years of a similar length. After the telescope came online, the mission team realised that other sun-like stars are more active than ours, and they bounce around too much in the telescope’s field of view. To find enough Earths, they would need seven or eight years of data.

Read the entire article here.

Image courtesy of the BBC. Drake Equation courtesy of Wikipedia.