Tabby’s Star Dust-Up: There’s No Alien Megastructure

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Sadly, not aliens (NASA/Getty/Ian O’Neill)

If you were hoping that the bizarre transit signals coming from Tabby’s Star were signs of a massive alien construction site, you’d better sit down.

A new study published in Astrophysical Journal Letters today documents a highly-detailed astronomical study of the star, concluding that this stellar oddity is driven by natural phenomena and most likely not caused by an extraterrestrial intelligence.

Since citizen scientists of the exoplanet project Planet Hunters identified the odd transit signal of KIC 8462852 from publicly-available data collected by NASA’s Kepler Space Telescope in 2015, the world has been captivated by what it means. Though KIC 8462852 is a fairly average star as stars go, it exhibited inexplicable dimming events that have never been seen before.

Finding something extraordinary in deep space is often followed by extraordinary explanations, including the possibility that some super-advanced alien civilization is building a “megastructure” around its star. Over time, more rational hypotheses have been ruled out, but how do you rule out aliens fiddling with their star’s brightness? Well, that’s taken a little more time.

Now, thanks to a study headed by astronomer Tabetha Boyajian of Louisiana State University in Baton Rouge, it seems the alien megastructure hypothesis has bitten the dust, literally.

“Dust is most likely the reason why the star’s light appears to dim and brighten,” Boyajian said in a statement. “The new data shows that different colors of light are being blocked at different intensities. Therefore, whatever is passing between us and the star is not opaque, as would be expected from a planet or alien megastructure.”

As you’d expect, if something solid (like a massive Alien Made™ solar energy collector) were to pass in front of a star, all wavelengths of light would be stopped at the same time. The fact that the dimming events are wavelength (brightness) dependent suggests that whatever is blocking the starlight isn’t a solid mass.

Boyajian, Tabby’s Star’s namesake who led the team that discovered the stellar dimming phenomenon, and her team of over 100 astronomers carried out an unprecedented observation campaign on the star from March 2016 to December 2017 using the Las Cumbres Observatory network. The project was supported by a Kickstarter campaign that raised $100,000 from 1,700 backers.

During the campaign, four distinct dimming events were detected at Tabby’s Star and each were given names by the project’s crowdfunding community. Starting in May 2017, the first two dips were named “Elsie” and “Celeste,” and the second two were named after the lost cities of Scotland’s “Scara Brae” and Cambodia’s “Angkor.”

“They’re ancient; we are watching things that happened more than 1,000 years ago. They’re almost certainly caused by something ordinary, at least on a cosmic scale. And yet that makes them more interesting, not less. But most of all, they’re mysterious.” — from “The First Post-Kepler Brightness Dips of KIC 8462852,” ApJL, 2018

Although the story of the alien megastructure may be coming to an end, this astronomical saga has been an incredible success for science outreach and public engagement with citizen science projects, like Planet Hunters. In this incredible age of astronomy where there’s simply too much data to analyse, scientists are increasingly turning to the public for help in making groundbreaking discoveries.

“If it wasn’t for people with an unbiased look on our universe, this unusual star would have been overlooked,” added Boyajian. “Again, without the public support for this dedicated observing run, we would not have this large amount of data.”

So, the search continues and I, for one, am excited for the next “alien megastructure” mystery …

Read more: The ‘Alien Megastructure’ Star Is Doing Weird Things Again

It’s a Trap: Extraterrestrial Ozone May be Hidden at Exoplanets’ Equators

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ESO/M. KORNMESSER

Fortunately for life on Earth, our planet has an ozone layer. This high-altitude gas performs an invaluable service to biology, acting as a kind of global “sunscreen” that blocks the most damaging forms of ultraviolet radiation. Early in the evolution of terrestrial life, if there were no ozone layer, life would have found it difficult to gain a foothold.

So, in our effort to seek out exoplanets that are suitable for life, future telescopes will seek out so-called “biosignatures” in the atmospheres of alien worlds. Astrobiologists would be excited to find ozone in particular — not only for its biology-friendly, UV-blocking abilities, but also because the molecule’s building blocks (three oxygen atoms) can originate from biological activity on the planet’s surface.

But in a new study published Wednesday (Nov. 29) in the journal Monthly Notices of the Royal Astronomical Society, researchers modeling atmospheric dynamics on tidally-locked “habitable zone” exoplanets have concluded that finding ozone in these exo-atmospheres may be a lot more challenging than we thought.

Red Dwarf Hellholes

Recently, two exoplanets have taken the science news cycle by storm. The first, Proxima b, is touted as the closest temperate exoplanet beyond our solar system. Located a mere 4.22 light-years from Earth, this (presumably) rocky world orbits its star, Proxima Centauri, at just the right distance within the habitable zone. Should this world possess an atmosphere, it would receive just the right amount of energy for any water on its surface to exist in a liquid state. As liquid water is essential for life on Earth, logic dictates that life may be possible there too.

Whether or not Proxima b has the right orbit about its star is academic; there are many other factors to consider before calling it “Earth-like.” For starters, habitable zone exoplanets around red dwarfs will be “tidally locked.” Tidal locking occurs because red dwarf habitable zones are very close to the cool star; so to receive the same amount of heating as our (obviously) habitable Earth, habitable exoplanets around red dwarfs need to cuddle up close. And because they are so close, the same hemisphere will always face the star, while the other hemisphere will always face away. These strange worlds are anything but “Earth-like.”

Also, Proxima Centauri is an angry little star, blasting its locale with regular flares, irradiating its interplanetary space with X-rays, UV and high-energy particles — things that will strip atmospheres from planets and drench planetary surfaces with biology-wrecking radiation. As I’ve previously written, Proxima b is likely a hellhole. And things don’t bode well for that other “habitable” exoplanet TRAPPIST-1d, either.

It’s a Trap

But let’s just say, for astrobiology-sake, that a tidally-locked world orbiting a red dwarf does host an atmosphere and an alien biosphere has managed to evolve despite these stellar challenges. This biosphere is also pretty Earth-like in that oxygen-producing lifeforms are there and the planetary atmosphere has its own ozone layer. As previously mentioned, ozone would be a pretty awesome molecule to find (in conjunction with other biosignatures). But what if no ozone is detected? Well, according to Ludmila Carone, of the Max Planck Institute for Astronomy in Germany, and her team, not finding detecting ozone doesn’t necessarily mean it’s not there, it’s just that the atmospheric dynamics of tidally-locked worlds are very different to Earth’s.

“Absence of traces of ozone in future observations does not have to mean there is no oxygen at all,” said Carone in a statement. “It might be found in different places than on Earth, or it might be very well hidden.”

Earth’s ozone is predominantly produced at the equator where sun-driven chemical reactions occur high in the atmosphere. Atmospheric flows then transport chemicals like ozone toward the poles, giving our planet a global distribution. When carrying out simulations of tidally-locked worlds, however, Carone’s team found that atmospheric flows may operate in reverse, where atmospheric flows travel from the poles to the equator. Therefore, any ozone produced at the equator will become trapped there, greatly reducing our ability to detect it.

“In principle, an exoplanet with an ozone layer that covers only the equatorial region may still be habitable,” added Carone. “Proxima b and TRAPPIST-1d orbit red dwarfs, reddish stars that emit very little harmful UV light to begin with. On the other hand, these stars can be very temperamental, and prone to violent outbursts of harmful radiation including UV.”

So the upshot is, until we have observatories powerful enough to study these hypothetical exoplanetary atmospheres — such as NASA’s James Webb Space Telescope (JWST) or the ESO’s Extremely Large Telescope (ELT) — we won’t know. But modelling the hypothetical atmospheres of these very alien worlds will help us understand what we will, or won’t, see in the not-so-distant future.

“We all knew from the beginning that the hunt for alien life will be a challenge,” said Carone. “As it turns out, we are only just scratching the surface of how difficult it really will be.”

Sorry, Proxima Centauri Is Probably a Hellhole, Too

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The surface of Proxima b as imagined in this artist’s impression. Sadly, the reality probably doesn’t include an atmosphere (ESO/M. Kornmesser)

The funny thing about habitable zones is that they’re not necessarily habitable. In fact, depending on the star, some of them are likely downright horrible.

Take, for example, the “habitable zone exoplanet” orbiting our neighboring star Proxima Centauri. When the discovery of Proxima b was announced last year, the world erupted with excitement. After all, astronomers had detected an Earth-sized world right on our galactic doorstep, a mere four light-years away.

Immediately there was discussion about Proxima b’s habitable potential (could there be aliens?) and the possibility of the world becoming an interstellar target (might we one day go there on vacation?).

Alas, for the moment, these exo-dreams are pure fantasy as the only things we know about this world are its mass and its orbital period around the star. We have no clue about the composition of this exoplanet’s atmosphere — or even if it has an atmosphere at all. And, according to new research published in The Astrophysical Journal Letters, Proxima b would probably be a very unlikely place to find extraterrestrial life and you’d be ill advised to invest in a vacation home there.

Like TRAPPIST-1 — that other star system that contains “habitable, but probably not so habitable” exoplanets — Proxima Centauri is a red dwarf star. By their nature, red dwarfs are small and cooler than our sun. Their habitable zones are therefore very compact; to receive enough heating energy to keep water in a liquid state on their surfaces, any “habitable” red dwarf exoplanets would need to snuggle up really close to their star. Liquid water (as we all know) is essential for life. So, if you want to find life as we know it (not that weird Titan life), studying habitable zone planets would be a good place to start. And as red dwarfs are abundant in our galaxy, seeking out habitable zone planets in red dwarf star systems would, at first, seem like an even better place to start.

Except, probably not.

Red dwarfs are angry. They erupt with powerful flares, have powerful stellar winds and their habitable zones are awash with intense ultraviolet radiation. And, like TRAPPIST-1, Proxima Centauri probably wouldn’t be a great place to live.

But the researchers decided to test this hypothesis by throwing Earth in at the deep end.

“We decided to take the only habitable planet we know of so far — Earth — and put it where Proxima b is,” said Katherine Garcia-Sage, a space scientist at NASA’s Goddard Space Flight Center in Greenbelt, Md., and lead author of the study.

The big advantage for Earth is that it possesses a powerful global magnetic field that can deflect our sun’s solar wind and coronal mass ejections with a minimum of effort. But put Earth in a habitable zone orbit around Proxima Centauri and bad stuff starts to happen, fast.

At this location, the intensity of extreme ultraviolet radiation becomes a problem. Using data from NASA’s Chandra X-ray Observatory, the researchers could gauge the star’s activity and how much radiation would hit Proxima b. According to their calculations, the exoplanet receives hundreds of times more extreme ultraviolet radiation than Earth receives from our sun and, even if we assume Proxima b has an “Earth-like” magnetosphere, it will lose its atmosphere very quickly.

As ultraviolet radiation will ionize the exoplanet’s atmosphere, electrons (that are negatively charged) will be readily stripped from light atoms (hydrogen) and eventually the heavier atoms too (like oxygen and nitrogen). As the electrons are lost to space, a powerful “charge separation” is created and the positively charged ions that are left behind in the atmosphere will be dragged with the electrons, causing them to also be lost to space. Granted, the global magnetic field will have an effect on the rate of atmosphere loss, but the researchers estimate that this process will drain an atmosphere from Proxima b 10,000 times faster than what happens on Earth.

“This was a simple calculation based on average activity from the host star,” added Garcia-Sage. “It doesn’t consider variations like extreme heating in the star’s atmosphere or violent stellar disturbances to the exoplanet’s magnetic field — things we’d expect provide even more ionizing radiation and atmospheric escape.”

In the worst-case scenario, where the outer atmospheric temperatures are highest and the planet exhibits an “open” field line configuration, Proxima b would lose the equivalent of the whole of Earth’s atmosphere in just 100 million years. If the atmospheric temperatures are cool and a “closed” magnetic field line configuration is assumed, it will take 2 billion years for the atmosphere to be completely lost to space. Either way you look at it, unless the atmosphere is being continuously replaced (perhaps by very active volcanism), Proxima b will have very little chance to see life evolve.

“Things can get interesting if an exoplanet holds on to its atmosphere, but Proxima b’s atmospheric loss rates here are so high that habitability is implausible,” said Jeremy Drake, of the Harvard-Smithsonian Center for Astrophysics and study co-author. “This questions the habitability of planets around such red dwarfs in general.”

TRAPPIST-1: The ‘Habitable’ Star System That’s Probably a Hellhole

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Red dwarfs can be angry little stars (NASA/GSFC/S. Wiessinger)

There are few places that elicit such vivid thoughts of exotic habitable exoplanets than TRAPPIST-1 — a star system located less than 40 light-years from Earth. Alas, according to two recent studies, the planetary system surrounding the tiny red dwarf star may actually be horrible.

For anyone who knows a thing or two about red dwarfs, this may not come as a surprise. Although they are much smaller than our sun, red dwarfs can pack a powerful space weather punch for any world that orbits too close. And, by their nature, any habitable zone surrounding a red dwarf would have to be really compact, a small detail that would bury any “habitable” exoplanet in a terrible onslaught of ultraviolet radiation and a blowtorch of stellar winds. These factors would make the space weather environment around TRAPPIST-1 extreme to say the least.

“The concept of a habitable zone is based on planets being in orbits where liquid water could exist,” said Manasvi Lingam, a Harvard University researcher who led a Center for Astrophysics (CfA) study, published in the International Journal of Astrobiology. “This is only one factor, however, in determining whether a planet is hospitable for life.”

The habitable zone around any star is the distance at which a small rocky world can orbit and receive just the right amount of heating to maintain liquid water on its hypothetical surface. Orbit too close and the water vaporizes; too far and it freezes. As life needs liquid water to evolve, seeking out exoplanets in their star’s habitable zone is a good place to start.

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The peaceful surface of a TRAPPIST-1 habitable zone exoplanet as imagined in this artist’s rendering (NASA/JPL-Caltech)

For the sun-Earth system, we live in the middle of the habitable zone, at a distance of one astronomical unit (1 AU). For a world orbiting a red dwarf like TRAPPIST-1, its orbital distance would be a fraction of that — i.e. three worlds orbit TRAPPIST-1 in the star’s habitable zone at between 2.8% and 4.5% the distance the Earth orbits the sun. This is because red dwarfs are very dim and produce meager heating — for a world to receive the same degree of heating that our planet enjoys, a red dwarf world would need to snuggle up really close to its star.

But just because TRAPPIST-1 is dim, it doesn’t mean it holds back on ultraviolet radiation. And, according to this study, the three “habitable” exoplanets in the TRAPPIST-1 system are likely anything but — they would receive disproportionate quantities of damaging ultraviolet radiation.

“Because of the onslaught by the star’s radiation, our results suggest the atmosphere on planets in the TRAPPIST-1 system would largely be destroyed,” said co-author Avi Loeb, who also works at Harvard. “This would hurt the chances of life forming or persisting.”

Life as we know it needs an atmosphere, so the erosion by UV radiation seems like a significant downer for the possible evolution of complex life.

That’s not the only bad news for our extraterrestrial life dreams around TRAPPIST-1, however. Another study carried out by the CfA and the University of Massachusetts in Lowell (and published in The Astrophysical Journal Letters) found more problems. Like the sun, TRAPPIST-1 generates stellar winds that blast energetic particles into space. As these worlds orbit the star so close, they would be sitting right next to the proverbial nozzle of a stellar blowtorch — models suggest they experience 1,000 to 100,000 times stellar wind pressure than the solar wind exerts on Earth.

And, again, that’s not good news if a planet wants to hold onto its atmosphere.

“The Earth’s magnetic field acts like a shield against the potentially damaging effects of the solar wind,” said Cecilia Garraffo of the CfA and study lead. “If Earth were much closer to the sun and subjected to the onslaught of particles like the TRAPPIST-1 star delivers, our planetary shield would fail pretty quickly.”

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The TRAPPIST-1 exoplanet family. TRAPPIST-1 e, f and g are located in the system’s habitable zone (NASA/JPL-Caltech)

So it looks like TRAPPIST-1 e, f and g really take a pounding from their angry little star, but the researchers point out that it doesn’t mean we should forget red dwarfs as potential life-giving places. It’s just that life would have many more challenges to endure than we do on our comparatively peaceful place in the galaxy.

“We’re definitely not saying people should give up searching for life around red dwarf stars,” said co-author Jeremy Drake, also from CfA. “But our work and the work of our colleagues shows we should also target as many stars as possible that are more like the sun.”

Great Balls of ‘Space Mud’ May Have Built Earth and Delivered Life’s Ingredients

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Artist’s impression of the molten surface of early Earth (NASA)

When imagining how our planet formed 4.6 billion years ago from the protoplanetary disk surrounding our sun, images of large pieces of marauding space rock slamming into the molten surface of our proto-Earth likely come to mind.

But this conventional model of planetary creation may be missing a small, yet significant, detail. Those massive space rocks may not have been the conventional solid asteroids — they might have been massive balls of space mud.

This strange detail of planetary evolution is described in a new study published in the American Association for the Advancement of Science (AAAS) journal Science Advances and it kinda makes logical sense.

Using the wonderfully-named Mars and Asteroids Global Hydrology Numerical Model (or “MAGHNUM”), planetary scientists Phil Bland (Cornell University) and Bryan Travis (Planetary Science Institute) simulated the movement of material inside primordial carbonaceous chondrite asteroids — i.e. the earliest asteroids that formed from the sun’s protoplanetary disk that eventually went on to become the building blocks for Earth.

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A simulated cross section of a 200-meter wide asteroid showing its internal temperature profile and convection currents (temperatures in Celsius). Credit: PSI

It turns out that these first asteroids weren’t cold and solid lumps of rock at all. By simulating the distribution of rock grains inside these asteroids, the researchers realized that the internal heat of the objects would have melted the icy volatiles inside, which then mixed with the fine dust particles. Convection would have then dominated a large portion of these asteroids, causing continuous mixing of water and dust. Like a child squishing a puddle of dirt to create sloppy “mud pies,” this convection would have formed a ball of, you guessed it, space mud.

Travis points out that “these bodies would have accreted as a high-porosity aggregate of igneous clasts and fine-grained primordial dust, with ice filling much of the pore space. Mud would have formed when the ice melted from heat released from decay of radioactive isotopes, and the resulting water mixed with fine-grained dust.”

In other words: balls of mud held together by mutual gravity, gently convected by the heat produced by the natural decay of radioactive materials.

Should this model hold up to further scrutiny, it has obvious implications for the genesis of life on Earth and could impact the study of exoplanets and their habitable potential. The ingredients for life on Earth originated in the primordial protoplanetary soup, but until now the assumption has been that the space rocks carrying water and other chemicals were solid and frozen. If they were in fact churning away in space as dynamic mud asteroids, they could have been the “pressure cookers” that delivered those ingredients to Earth’s surface.

So the next question would be: how did these exotic asteroids shape life on Earth?

Smallest ‘Super-Earth’ Discovered With an Atmosphere — but It’s No Oasis

MPIA

For the first time, astronomers have detected an atmosphere around a small (and likely) rocky exoplanet orbiting a star only 39 light-years away. Although atmospheres have been detected on larger alien worlds, this is the smallest world to date that has been found sporting atmospheric gases.

Alas, Gliese (GJ) 1132b isn’t a place we’d necessarily call “habitable”; it orbits its red dwarf a little too close to have an atmosphere anything like Earth’s, so you’d have to be very optimistic if you expect to find life (as we know it) camping there. But this is still a huge discovery that is creating a lot of excitement — especially as this exo-atmosphere has apparently evolved intact so close to a star.

The atmosphere was discovered by an international team of astronomers using the 2.2 meter ESO/MPG telescope at La Silla Observatory in Chile. As the exoplanet orbited in front of the star from our perspective (known as a “transit”), the researchers were able to deduce the physical size of the world by the fraction of starlight it blocked. The exoplanet is around 40 percent bigger than Earth (and 60 percent more massive) making it a so-called “super-Earth.”

Through precision observations of the infrared light coming from the exoplanet during the 1.6 day transits, the astronomers noticed that the planet looked larger at certain wavelengths of light than others. In short, this means that the planet has an atmosphere that blocks certain infrared wavelengths, but allows other wavelengths to pass straight through. Researchers of the University of Cambridge and the Max Planck Institute for Astronomy then used this information to model certain chemical compositions, leading to the conclusion that the atmosphere could be a thick with methane or water vapor.

Judging by the exoplanet’s close proximity to its star, this could mean that the planet is a water world, with an extremely dense and steamy atmosphere. But this is just one of the possibilities.

“The presence of the atmosphere is a reason for cautious optimism,” writes a Max Planck Institute for Astronomy news release. “M dwarfs are the most common types of star, and show high levels of activity; for some set-ups, this activity (in the shape of flares and particle streams) can be expected to blow away nearby planets’ atmospheres. GJ 1132b provides a hopeful counterexample of an atmosphere that has endured for billion of years (that is, long enough for us to detect it). Given the great number of M dwarf stars, such atmospheres could mean that the preconditions for life are quite common in the universe.”

To definitively work out what chemicals are in GJ 1132b’s atmosphere, we may not be waiting that long. New techniques for deriving high-resolution spectra of exoplanetary atmospheres are in the works and this exoplanet will be high on the list of priorities in the hunt for extraterrestrial biosignatures. (For more on this, you can check out a recent article I wrote for HowStuffWorks.)

Although we’ll not be taking a vacation to GJ 1132b any time soon, the discovery of an atmosphere around such a small alien world will boost hopes that similar sized super-Earths will also host atmospheres, despite living close to red dwarf stars that are known for their flaring activity. If atmospheres can persist, particularly on exoplanets orbiting within a star’s so-called habitable zone, then there really should be cause for optimism that there really might be an “Earth 2.0” out there orbiting one of the many red dwarfs in our galaxy.

Mysterious Fomalhaut b Might Not Be an Exoplanet After All

The famous exoplanet was the first to be directly imaged by Hubble in 2008 but many mysteries surround its identity — so astronomers are testing the possibility that it might actually be an exotic neutron star.

NASA, ESA, P. Kalas, J. Graham, E. Chiang, E. Kite (University of California, Berkeley), M. Clampin (NASA Goddard Space Flight Center), M. Fitzgerald (Lawrence Livermore National Laboratory), and K. Stapelfeldt and J. Krist (NASA Jet Propulsion Laboratory)

Located 25 light-years from Earth, the bright star Fomalhaut is quite the celebrity. As part of a triple star system (its distant, yet gravitationally bound siblings are orange dwarf TW Piscis Austrini and M-type red dwarf LP 876-10) Fomalhaut is filled with an impressive field of debris, sharing a likeness with the Lord Of The Rings’Eye of Sauron.” And, in 2008, the eerie star system shot to fame as the host of the first ever directly-imaged exoplanet.

At the time, the Hubble Space Telescope spotted a mere speck in Fomalhaut’s “eye,” but in the years that followed the exoplanet was confirmed — it was a massive exoplanet approximately the size of Jupiter orbiting the star at a distance of around 100 AU (astronomical units, where 1 AU is the average distance the Earth orbits the sun). It was designated Fomalhaut b.

This was a big deal. Not only was it the first direct observation of a world orbiting another star, Hubble was the aging space telescope that found it. Although the exoplanet was confirmed in 2013 and the International Astronomical Union (IAU) officially named the exoplanet “Dagon” after a public vote in 2015, controversy surrounding the exoplanet was never far away, however.

Astronomers continue to pick at Fomalhaut’s mysteries and, in new research to be published in the journal Monthly Notices of the Royal Astronomical Society, Fomalhaut b’s identity has been thrown into doubt yet again.

“It has been hypothesized to be a planet, however there are issues with the observed colors of the object that do not fit planetary models,” the researchers write. “An alternative hypothesis is that the object is a neutron star in the near fore- or background of Fomalhaut’s disk.” The research team is lead by Katja Poppenhaeger, of Queen’s University, Belfast, and a preprint of their paper (“A Test of the Neutron Star Hypothesis for Fomalhaut b”) can be found via arXiv.org.

Artist’s impression of Fomalhaut b inside its star’s debris disk (ESA, NASA, and L. Calcada – ESO for STScI)

Fomalhaut b was detected in visible and near-infrared wavelengths, but followup studies in other wavelengths revealed some peculiarities. For starters, the object is very bright in blue wavelengths, something that doesn’t quite fit with exoplanetary formation models. To account for this, theorists pointed to a possible planetary accretion disk like a system of rings. This may be the reason for the blue excess; the debris is reflecting more starlight than would be expected to be reflected by the planet alone. However, when other studies revealed the object is orbiting outside the star system’s orbital plane, this explanation wasn’t fully consistent with what astronomers were seeing.

Other explanations were put forward — could it be a small, warm world with lots of planetesimals surrounding it? Or is it just a clump of loosely-bound material and not a planet at all? — but none seem to quite fit the bill.

In this new research, Poppenhaeger’s team pondered the idea that Fomalhaut b might actually be a neutron star either in front or behind the Fomalhaut debris disk and, although their work hasn’t proven whether Fomalhaut b is an exoplanet or not, they’ve managed to put some limits on the neutron star hypothesis.

Neutron stars are the left-overs of massive stars that have run out of fuel and gone supernova. They are exotic objects that are extremely dense and small and, from our perspective, may produce emissions in visible and infrared wavelengths that resemble a planetary body. Cool and old neutron stars will even generate bluer light, which could explain the strange Fomalhaut b spectra.

Neutron stars also produce ultraviolet light and X-rays and, although it is hard to separate the UV light coming from the exoplanet and the UV light coming from the star, X-ray emissions should be resolvable.

Artist’s impression of a magnetar, an extreme example of a neutron star (ESO/L.Calçada)

So, using observations from NASA’s Chandra X-ray Observatory, the researchers looked at Fomalhaut b in soft X-rays and were able to put some pretty strong constraints on whether or not this object really could be a neutron star. As it turned out, Chandra didn’t detect X-rays (within its capabilities). This doesn’t necessarily mean that it isn’t a neutron star, it constrains what kind of neutron star it could be. Interestingly, it also reveals how far away this object could be.

Assuming it is a neutron star with a typical radius of 10 kilometers, and as no X-ray emissions within Chandra’s wavelength range were detected, this object would be a neutron star with a surface temperature cooler than 90,000 Kelvin — revealing that it is over 10 million years old. For this hypothesis to hold, the neutron star would actually lie behind the Fomalhaut system, around 44 light-years (13.5 parsecs) from Earth.

Further studies are obviously needed and, although the researchers point out that Fomalhaut b is still most likely an exoplanet with an extensive ring system (just with some strange and as-yet unexplained characteristics), it’s interesting to think that it could also be a neutron star that isn’t actually in the Fomalhaut system at all. In fact, it could be the closest neutron star to Earth, providing a wonderful opportunity for astronomical studies of these strange and exotic objects.

About Those ‘Habitable’ Exoplanets (RT America Interview)

On Monday, I appeared on RT America’s live news broadcast to talk exoplanets — particularly the three small (possibly rocky) worlds that orbit the stars Kepler-62 and Kepler-69. It was a lot of fun discussing ‘Goldilocks Zones’ and the possibilities of extraterrestrials. Enjoy!

Discovery News coverage of Kepler-62:

Life: Not So Grim On The Galactic Rim?

M80 -- an old globular cluster in the Milky Way -- is full of metal-poor stars. Do they still have exoplanetary potential? (NASA)
M80 — an old globular cluster in the Milky Way — is full of metal-poor stars. Do they still have exoplanetary potential? (NASA)

The galaxy may be brimming with habitable small worlds and many older star systems could possess the conditions ripe for advanced alien civilizations to evolve. This prediction comes in the wake of new analysis of data from NASA’s Kepler space telescope and ground based observatories by a team of Danish and American astronomers.

Led by Lars Buchhave of the Niels Bohr Institute in Copenhagen, the team has revealed that stars containing low quantities of heavy elements — known as “metal poor” stars — are still capable of nurturing exoplanets with Earth-like qualities.

“I wanted to investigate whether planets only form around certain types of stars and whether there is a correlation between the size of the planets and the type of host star it is orbiting,” Buchhave said.

After analyzing the elemental composition of stars hosting 226 small exoplanets — some as small as the rocky planets in the Solar System — Buchhave’s team discovered that “unlike the gas giants, the occurrence of smaller planets is not strongly dependent on stars with a high content of heavy elements. Planets that are up to four times the size of Earth can form around very different stars — also stars that are poorer in heavy elements,” he concluded.

The Kepler mission, for example, is actively carrying out a search for exoplanets that pass in front of their host stars (events known as “transits”). With Kepler’s sensitive eye, it is capable of detecting exoplanets of similar size to Earth, or even as small as Mars.

Interestingly, as it surveys Sun-like stars, Kepler can detect tiny, rocky worlds that orbit within the “habitable zones” of their stars. It’s no huge leap of the imagination to think alien life may have evolved on some of these worlds.

But a problem facing astronomers hunting for bona fide “Earth-like” exoplanets is that many older stars have low quantities of heavier elements (such as the silicon and iron) that small rocky worlds need to become… well… rocky. But Buchhave’s discovery suggests that stars once considered infertile may in fact have a shot at birthing small exoplanets.

Jill Tarter, Chair of the SETI Institute, points out that this could be a boon for the search for intelligent extraterrestrials. “The idea that very old stars could also sport habitable planets is encouraging for our searches,” she said in a SETI press release on Wednesday.

Tarter also highlights the fact that life took a long time to evolve into an advanced technological state on Earth. Therefore, should there be small habitable rocky worlds orbiting ancient stars (as this research suggests), perhaps alien life far older and more technologically advanced than ourselves are out there.

Although this seems to make logical sense, it may not make biological sense. Metal-poor stars might have the ability to create small worlds, but just because there are likely many small worlds out there, it doesn’t mean life can be nurtured. But then again, regions of the Milky Way once considered to be devoid of exoplanets may now have a stab at providing a planetary habitat for extraterrestrial biology to gain a foothold. Whether or not these metal poor stars host the right ingredients for the building blocks of life probably won’t be known for some time.

In 2009, I wrote an article (see “Life Is Grim On The Galactic Rim“) that grabbed the attention of National Geographic writer Ken Croswell who quoted my Astroengine.com article in the December 2010 edition of the magazine. In the text, I discussed some research that investigated the strange lack of protoplanetary disks around a selection of metal-poor star clusters in the outermost regions of the galaxy. The lack of a protoplanetary disk means a lack of exoplanet-birthing potential and a grim outlook for life to evolve in regions of the galaxy distant from the galactic core.

The conclusion of this 2009 work appears to contradict these most recent findings and the suggestion that advanced alien civilizations may have evolved around metal-poor stars. Whether these stars are the exception rather than the rule, or whether their low metallicity influences the size or visibility of their protoplanetary disks would be an interesting factor to consider.

Although SETI searches have yet to turn up any signal from an advanced alien technology, Kepler is proving that stars — regardless of their metallicity — have the ability to host small rocky worlds. Should life have taken hold on these worlds, then perhaps, some day, we may intercept an interstellar phone call from one of them.

This topic and a myriad of others will be discussed on June 22-24 where the world’s leaders in the field of alien and exoplanet hunting will meet at the Hyatt Santa Clara hotel in California’s Silicon Valley for SETIcon.

UPDATE: After tweeting this article, @spacearcheology retweeted my link with the following comment:

This is something I neglected to consider in the original post. If there are indeed many more small rocky worlds out there — particularly around metal-poor stars that are, by their nature, ancient — why the heck haven’t we detected any ancient extraterrestrial intelligences yet? This has just become the Fermi Paradox PLUS…

Exoplanet Count Tops 700

An artist's impression of a lone exoplanet transiting its parent star. There are now 700 confirmed alien worlds orbiting other stars (ESO)
An artist's impression of a lone exoplanet transiting its parent star. There are now 700 confirmed alien worlds orbiting other stars (ESO)

On Friday, the Extrasolar Planets Encyclopedia registered more than 700 confirmed exoplanets. Although this is an amazing milestone, it won’t be long until the “first thousand” are confirmed.

There are now more than 700 confirmed exoplanets in the database. The latest addition is the planet HD 100655 b.
— announced via the Exoplanet iPhone app

Only two months ago, the encyclopedia — administered by astrobiologist Jean Schneider of the Paris-Meudon Observatory — registered 600 confirmed alien worlds. Since then, there has been a slew of announcements including the addition of a batch of 50 exoplanets by the European Southern Observatory’s (ESO) High Accuracy Radial velocity Planet Searcher (or HARPS) in September.

The first exoplanet was discovered orbiting a Main Sequence star in 1995, and the rate of exoplanet detections has been accelerating ever since.

It is worth noting that hundreds more candidate exoplanet detections have been made, many of which have been spotted by NASA’s Kepler space telescope. Kepler is staring at the same patch of sky, waiting for alien worlds to cross the line of sight between their parent star and Earth, registering a slight dip in starlight brightness. The 1,235 candidates will be confirmed (or denied) as Kepler awaits future transits.

Detecting the slight dimming of starlight isn’t the only tool exoplanet hunters have to spot these alien worlds. The “radial velocity” method — as employed by systems such as the ESO’s HARPS — can detect the slight “wobble” of stars as orbiting worlds gravitationally “tug” on their parent stars. Both methods have their advantages and both are notching up an impressive exoplanet count. “Microlensing” has also been employed to spot a handful of exoplanets, as has direct imaging.

Exoplanetary studies are amongst the most exciting astronomical projects out there. Not only are we realizing there is a veritable zoo of worlds — some Earth-sized, others many times the mass of Jupiter — we are also pondering the most profound question: could extraterrestrial life inhabit these worlds?

For now, we have no clue, but life as we know it has a habit of springing up where we least expect it, it’s only a matter of time before we start to have some clue as to the existence of life as we don’t know it.