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Assorted Personal Notations, Essays, and Other Jottings

Posts Tagged ‘extraterrestrial life

[BLOG] Some Friday links

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  • The Big Picture shares photos of motorbike racing in South Africa.
  • Centauri Dreams considers the stellar weather that planets of red dwarf stars might encounter.
  • Dead Things looks at two genetic studies which complicate the narrative of humanity’s spread.
  • Dangerous Minds shares the infamous anti-disco night of 1979 that spelled the end of the genre in North America.
  • The Everyday Sociology Blog considers how one makes a home among strangers.
  • Joe. My. God. notes that the UKIP MP claims the sun is responsible for the bulk of the Earth’s tides not the moon, and reports on a Kentucky judge who says gays ruined straight men’s ability to hug.
  • Language Log looks at changing patterns of language usage in Japanese.
  • Lawyers, Guns and Money mocks the cosmic perspective of Gary Johnson.
  • The LRB Blog reports from devastated Lesbos.
  • Maximos62 maps the smoke from this year’s Indonesian fires.
  • The NYRB Daily shares vintage photos from mid-1960s Cuba.
  • The Planetary Society Blog reports on a recent tour of NASA facilities.
  • Window on Eurasia reports on a call for a single Circassian alphabet, suggests a Russian initiative to use sufism to unite Russian Muslims will end badly, and argues that Russian criticism of language policy in post-Soviet countries is linked to geopolitics.

[BLOG] Some Saturday links

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  • The Dragon’s Gaze looks at Proxima Centauri b, its atmosphere and its geomagnetics and its history and, of course, its potential habitability.
  • The Dragon’s Tales wonders about the origins of Titan’s channels.
  • Torontoist notes mental health care issues for those without a family doctor.
  • The Volokh Conspiracy notes European Union rulings on linkage.
  • Window on Eurasia notes the poor position of local recruits in the Donbas republics’ militaries.

[FORUM] What do you think about Proxima Centauri b?

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I’ve been excited by the apparent discovery of Proxima Centauri b, reporting the first rumours of the world’s discovery and then sharing (among other things) two news round-up posts.

My excitement is well-justified: In a best-case scenario, Proxima Centauri b could be as close to being an Earth-like world as we could reasonably imagine. It could be a second Earth, even home to life. If it’s not, then it would still be of note as the closest extrasolar planet, a world worthy of study. It would certainly make a tempting target for our first interstellar probes. Proxima Centauri b, whatever it is exactly, is a world that matters.

What do you think? Are you excited for reasons I share? Are there things that get you going? Do you not care much, or at all?


Written by Randy McDonald

August 28, 2016 at 11:59 pm

[NEWS] Some more links about Proxima Centauri b

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The European Southern Observatory provided this artist’s impression of the surface of Proxima b. “The double star Alpha Centauri AB also appears in the image to the upper-right of Proxima itself. Proxima b is a little more massive than the Earth and orbits in the habitable zone around Proxima Centauri, where the temperature is suitable for liquid water to exist on its surface.”


Proxima Centauri b has continued to excite over the weekend. The MacLean’s article “Why everyone is excited about an exoplanet named Proxima b”, by Amanda Shendrake, points out the apparent import for a layman’s audience.

Just because an exoplanet is in a star’s habitable zone, however, does not mean it can host life. It simply means that if the exoplanet featured a similar atmosphere and surface pressure as the Earth, the planet could sustain liquid water. Unfortunately, we know nothing about Proxima b’s atmosphere.

For an exoplanet to be potentially habitable, scientists consider more than just whether or not it can host water. The star around which the exoplanet orbits needs to be of a particular type—one that burns long enough to allow life a chance to evolve, and emits appropriate amounts of ultraviolet radiation.

Additionally, the exoplanet must have significant similarities to Earth. The Earth Similarity Index (ESI) is a way to measure this likeness, and it places objects on a scale of zero to one, where one is Earth itself. The closer to 1.0, the more similar the exoplanet is to our home. The measurement takes into account radius, density, escape velocity, and surface temperature.

No other planets in our solar system are Earth-like; however, in addition to being the nearest of the 44 potentially habitable exoplanets we’ve found, Proxima b also has the highest ESI.

(Nice infographics, too.)

At Scientific American, Elizabeth Tasker’s blog post “Yes, We’ve Discovered a Planet Orbiting the Nearest Star but…” notes the many, many caveats around identifying Proxima Centauri b as Earth-like. Sarah Scoles’ Wired article “Y’all Need to Chill About Proxima Centauri b” explores the same territory, and makes an argument as to the underlying motivation for this identification of worlds as potentially Earth-like.

[I]t’s not an Earth twin, no matter what the headlines say, and neither are any other planets scientists have found. Hot Jupiters may be cool; planets that rain glass may be a hit at parties; “Super-Earth” may be fun to say. And getting the full census of exoplanets is valuable. But most scientists, Messeri has found, really just want to find another Earth. Research priorities reflect that. The Kepler Space Telescope, which has discovered more planets than any other enterprise, was “specifically designed to survey a portion of our region of the Milky Way galaxy to discover dozens of Earth-size planets in or near the habitable zone,” according to NASA.

The search for an “Earth Twin” is the quest for a platonic ideal, says Messeri. “It allows us to imagine Earth at its best, Earth as we want to imagine it, Earth that isn’t hampered by climate change or war or disease,” she says.

In other words, Earth as we’ve never known it and never will. If scientists found a twin planet, Pure Earth would become, in our minds, a real place that still exists, somewhere out there.

But we haven’t discovered that place. And we might not ever. On a quest for the perfect partner, you usually find someone who’s pretty cool but yells at you when they’re hungry, or hates your mom. After you sign on to the perfect job, you discover that you’re supposed to wash everyone’s coffee mugs. In that way, finding Proxima Centauri b while searching for Pure Earth is just like every human quest for perfection.

“What we’ve actually found is something more real,” says Messeri, “and less ideal.”

Joseph Dussault at the Christian Science Monitor notes in “Do we need to change the way we talk about potentially habitable planets?” that the language used to describe these worlds may need to be altered, for lay audiences at least. Universe Today’s Matt Williams notes that Earth-like means something that is not a duplicate of Tahiti.

[F]inding a planet that is greater in size and mass than Earth, but significantly less than that of a gas giant, does not mean it is terrestrial. In fact, some scientists have recommended that the term “mini-Neptune” be used to describe planets that are more massive than Earth, but not necessarily composed of silicate minerals and metals.

And estimates of size and mass are not exactly metrics for determining whether or not a planet is “habitable”. This term is especially sticky when it comes to exoplanets. When scientists attach this word to extra-solar planets like Proxima b, Gliese 667 Cc, Kepler-452b, they are generally referring to the fact that the planet exists within its parent star’s “habitable zone” (aka. Goldilocks zone).

This term describes the region around a star where a planet will experience average surface temperatures that allow for liquid water to exist on its surface. For those planets that orbit too close to their star, they will experience intense heat that transforms surface waster into hydrogen and oxygen – the former escaping into space, the latter combining with carbon to form CO².

This is what scientists believe happened to Venus, where thick clouds of CO² and water vapor triggered a runaway greenhouse effect. This turned Venus from a world that once had oceans into the hellish environment we know today, where temperatures are hot enough to melt lead, atmospheric density if off the charts, and sulfuric acid rains from its thick clouds.

For planets that orbit beyond a star’s habitable zone, water ice will become frozen solid, and the only liquid water will likely be found in underground reservoirs (this is the case on Mars). As such, finding planets that are just right in terms of average surface temperature is intrinsic to the “low-hanging fruit” approach of searching for life in our Universe.

Even so, the optimism expressed by Bloomberg View’s Faye Flam in “What the New Planet Says About Life in the Universe” is something I would like to cling to. Proxima b’s ideal, or at least worlds like this ideal, might be perfectly suited for life.

Studying this planet could reveal something important about the timeline of life in the universe, and whether we earthlings are early to the party. That’s because stars like Proxima Centauri are the future of the universe. Called red dwarfs, these make up the majority of stars in the galaxy, and they live about 1,000 times as long as our sun.

In a paper made public last month, Harvard astronomer Avi Loeb looked at the cosmic implications of life surrounding red dwarfs. Loeb calculated that if life is just as likely to form around these stars as sun-like ones, then the vast majority of life in the universe has yet to be born, and we earthlings are not just early, he said, but “premature.”

That’s because scientists believe eventually, all the raw materials for star formation will be used up and all the stars will die, leaving a dark universe of dust and black holes. For most of the trillions of years stretching between now and cosmic darkness, red dwarfs will be the only game in town.

The papers at arXiV at least allow for hope. Why not encourage it?

Written by Randy McDonald

August 28, 2016 at 10:29 pm

[NEWS] Some links about the discovery of Proxima Centauri b

The first confirmation I had of the discovery of Proxima Centauri b came from James Nicoll, who shared the European Southern Observatory’s announcement that the Pale Red Dot search program bore spectacular fruit.

Phil Plait at Bad Astronomy, Jennifer Ouellette at Gizmodo, and Franck Marchis at the Planetary Society Blog provided among the first blogged reactions I saw on my Facebook feed. Marchis’ summary of what led to the discovery deserves reproduction.

We now know of 3,374 exoplanets, an enormously large number, given that we discovered the first one only in 1995. Like the cartographers of the seventeenth century, who slowly build a map of our world, astronomers are drawing a map of our galactic neighborhood. We think we have a good handle on the location of nearby stars—that is, ones that are less than 50 light-years away. We know their distance, size, temperature, and if they are multiple systems or single stars, for example; but ultimately what we would really like to add to this 3D map of the galaxy are the planets in orbit around these stars.

The Pale Red Dot group was particularly interested in finding planets around Proxima Centauri, the star closest to the Sun. Proxima Centauri is only 4.25 light-years away, so it’s in our cosmic backyard. Because of its small mass, it’s too faint to be seen with the naked eye, and was discovered only in 1915. At the end of the 1990s, astronomers tried to detect potential large planets in orbit around this star using the radial-velocity method and came back empty-handed.

In the article published today in Nature, a group of modern astronomers reported on what they learned by using two high-precision radial-velocity instruments: HARPS at the 3.6m telescope of La Silla and UVES at the VLT 8m class telescope, both part of the European Southern Observatory. Several of these observations were done as part of other programs that took place between 2000 and 2016, but from January 2016 to March 2016, the team collected what we call high-cadence data, a fancy way to state that the star was observed once per night to increase its chance of detecting a tiny variation in its motion (about a meter per second, or the speed of a human walking) that might be caused by the presence of a small planet.

This ambitious program has paid off beyond our wildest dreams in that we have now unambiguously detected a planet with a minimum mass 1.3 times that of Earth orbiting the star right in the middle of the goldilocks zone (0.05 AU). I am not a specialist in radial-velocity measurement, but this detection seems quite convincing in that it has a false-alarm probability of less than 0.1% and uses a careful comparison of star activity (done by using additional small telescopes during the survey) that are known to mimic the signal of a planet. That is a very significant new data point to add in our cosmic map.

This world, Marchis notes, is not necessarily an Earth analog. Its tidal locking to Proxima aside, as is Proxima Centauri’s nature as a very active flare star, we know only basic data about Proxima Centauri b: “The planet’s MINIMUM mass is 1.3 Earths because we don’t really know the orientation of the orbital plane with respect to the observer. (The radial-velocity method provides a measurement of m sin i, with i being the inclination of the system with respect to us.) Assuming random orientations of orbital planes, we have a 90% probability that the true mass is less than 2.3 times the minimum mass, so 3 Earths. In short, this could be a super-Earth or something more exotic, like a baby-Neptune.”

Even so, this is huge. The nearest star to our own hosts a potentially Earth-like world? The Dragon’s Gaze was quick to link to the discovery paper, but it was when I saw the news appear on Joe. My. God. that I knew this was big.

Centauri Dreams’ Paul Gilster reacted at length, going back to Proxima’s first appearance in science fiction in 1935 and noting the many potential issues with Proxima Centauri b being truly habitable.

We have a long way to go before knowing whether a planet around a red dwarf like this can truly be habitable. Tidal locking is always an issue because a planet this close to its host (Proxima Centauri b is on an 11.2-day orbit) is probably going to have one side fixed facing the star, the other in permanent night. There are papers arguing, however, that tidal lock does not prevent a stable atmosphere with global circulation and heat distribution from occurring.

And what about Proxima’s magnetic field? The average global magnetic flux is high compared to the Sun’s (600±150 Gauss vs. the Sun’s 1 G). Couple this with flare activity and there are scenarios where a planet gradually has its atmosphere stripped away. A strong planetary magnetic field could, however, prevent this erosion. Nor would X-rays (400 times the flux the Earth receives) necessarily destroy the planet’s ability to keep an atmosphere.

And then there’s the matter of the planet’s origins, and how that could affect what is found there. From the paper:

…forming Proxima b from in-situ disk material is implausible because disk models for small stars would contain less than 1 M Earth of solids within the central AU. Instead, either 1) the planet migrated in via type I migration, 2) planetary embryos migrated in and coalesced at the current planet’s orbit, or 3) pebbles/small planetesimals migrated via aerodynamic drag and later coagulated into a larger body. While migrated planets and embryos originating beyond the ice-line would be volatile rich, pebble migration would produce much drier worlds.

Discover‘s blogs provided good coverage, D-Brief looking up the Alpha Centauri system’s more notable appearances in science fiction and Crux summing up the data.

The question of habitability has been coming up. The Pale Red Dot team engaged in a Reddit AMA about their discovery, while co-discover Ignas Ribisi analyses the potential for habitability, and liquid water, at length. (Much depends on how this world is tidally locked, it turns out.) In a charming poetic analysis, Sean Raymond also examines the question of how the planet is in synchronous orbit with its sun. Gizmodo, meanwhile, published an article suggesting that Proxima’s flares need not pose a challenge for life on Proxima b, that the phenomenon of biofluorescence–briefly, using proteins to absorb high-energy light and retransmit it in less harmful forms–could well be present.

New Scientist has an enlightening article that, among other things, looks at the background to the planet’s discovery and hints at more.

Astronomers will still want to turn their scopes towards Proxima Centauri – to confirm that the planet is real, and avoid a repeat of an earlier embarrassment. Despite initial excitement, the claimed discovery in 2012 of a planet orbiting neighbouring Alpha Centauri B now looks to have been a mistake.

[Mikko] Tuomi and his colleagues have done everything they can to avoid that happening again. He first saw signs of Proxima b in 2013, when looking at data taken by the Very Large Telescope at Paranal Observatory in Chile between 2003 and 2009. “I spent weeks trying to make the signal go away, trying to show that it was caused by the star’s activity or pure measurement noise rather than a planet,” he says. But the team became increasingly convinced.

To confirm the find, the group examined data from other telescopes and in January this year began the Pale Red Dot campaign, using another instrument in Chile – the HARPS planet-searcher at the La Silla Observatory. The observations lasted 60 nights, but the team was confident of a discovery after just 10 nights of data, says Tuomi. “It was as predicted by the previous observations. We knew this was going to become a year to remember for exoplanet science.”

“I think this is a very solid thing,” says Snellen. “For me personally, this is the scientific discovery of the year, maybe of the decade.”

The team also saw signs of a second potential planet around Proxima Centauri, a super-Earth with an orbit of between 60 and 500 days. If such an outer planet exists, it might be possible to observe it, says Tuomi.

What can be said but that we need–want–so much more data? What is Proxima Centauri b actually like? Could it be Earth-like? Are there oceans, life?

I, and the Earth, await more.

[BLOG] Some Thursday links

  • News of Proxima Centauri b spread across the blogosphere yesterday, to Discover‘s D-Brief and Crux, to Joe. My. God., to the Planetary Society Blog, and to Centauri Dreams and The Dragon’s Gaze.
  • blogTO notes the impending opening of Toronto’s first Uniqlo and suggests TTC buses may soon have a new colour scheme.
  • The Dragon’s Gaze discusses detecting exo-Titans and looks at the Kepler-539 system.
  • Marginal Revolution notes Poland’s pension obligations.
  • The Map Room Blog looks at how empty maps are of use to colonialists.
  • Steve Munro examines traffic on King Street.
  • The NYR Daily looks at what an attic of ephemera reveals about early Islam.
  • Otto Pohl announces his arrival in Kurdistan.
  • The Russian Demographics Blog and Window on Eurasia note that more than half of Russia’s medal-winners at the Olympics were not ethnically Russian, at least not wholly.
  • Window on Eurasia looks at Ukraine’s balance sheet 25 years after independence and considers if Belarus is on the way to becoming the next Ukraine.

[AH] WI there was a Venus-sized planet between Mars and Jupiter?

In astronomer and writer Chris Impey‘s 2010 Talking About Life, an anthology of his interviews with leading experts in astronomy and related fields about extraterrestrial life, there was a passage in his interview with Debra Fischer that caught my attention for its alternate history potential. Solar systems, including our own, are apparently as densely packed with planets as possible.

DF: The amazing thing I learned when we discovered the Upsilon Andromedae system is that our Solar System s actually dynamically full of planets. When people who model the Solar System try to drop in an extra planet, the whole system goes into chaos–some planets are lost, some fall into the star, some are ejected, and then everything finally settles down. Each planet has its own gravitational domain and those domains are pushed up next to each other. Our Solar System resides on the verge of instability it’s stable, but only just.

CI: Is this related to the numerical coincidence of their nearly geometric spacing?

DF: Bode’s law? Yes. They clear out disks; many lines of evidence suggest that core accretion is the correct model. Then they begin to migrate in until they come into a zone; again, if they get any closer. they’re ejected. When I noted this back in 2000, Hal Levinson raised his hand and said, “No, no, that’s not true–there a place between Mars and Jupiter where a Venus-sized planet will survive.” And I think, “How many simulations did you have to run to find that tiny little window? That doesn’t count!” [Laughs](269-270).

The WI question is obvious. What if there was a planet the mass of Venus orbiting in our solar system between Mars and Jupiter?

This planet–call it *Ceres, after the largest dwarf planet orbiting between Mars and Jupiter–would be a big one. Venus is more than 80% as massive as the Earth. Such a massive planet would be able to hold onto its volatiles–its atmosphere, its water–in a way that a nearer Mars could not. This planet might even be massive enough to be geologically active. *Ceres might provide a relatively hospitable environment, more hospitable than Venus or even Mars.

It’s important to not overstate this potential habitability. Whatever the precise nature of its orbit, *Ceres would also be very cold, orbiting outside of the orbit of Mars and likely even an elastic definition of our sun’s circumstellar habitable zone. A sufficiently dense heat-retaining atmosphere might change things, but would it warm *Ceres enough?

Given *Ceres’ location near the frost line of the solar system, and its high gravity, it’s likely to have attracted and kept quite a lot of ice. Perhaps it will be an ocean world; perhaps it will be a world with a frozen surface on top of a planet-wide ocean, a super-Europa even. As seen in the night sky from Earth, its atmosphere and icy surface may make it very bright indeed.


Written by Randy McDonald

August 23, 2016 at 11:57 pm