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

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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

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  • 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?

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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

[BLOG] Some Tuesday links

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  • blogTO shares some photos of Toronto in the gritty 1980s.
  • The Dragon’s Gaze links to a paper examining the habitable zones of post-main sequence stars.
  • Far Outliers notes the ethnic rivalries among First World War prisoners in the Russian interior, and examines how Czechoslovakia got its independence.
  • The Map Room Blog looks at the mapping technology behind Pokémon Go.
  • pollotenchegg looks at how the populations of Ukrainian cities have evolved.
  • Savage Minds considers anthropology students of colour.
  • Transit Toronto notes</a the end of tunnelling for the Eglinton LRT.
  • Window on Eurasia suggests the post-Soviet states built Soviet-style parodies of capitalism for themselves.

[BLOG] Some Monday links

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  • At Antipope, Charlie Stross writes about how colonizing even a nearby and Earth-like Proxima Centauri b would be far beyond our abilities.
  • The Broadside Blog’s Caitlin Kelly responds to Canada’s mourning of the Tragically Hip.
  • Centauri Dreams considers the life that may exist in the oceans of Europa.
  • D-Brief notes an Alaskan village that is being evacuated because of climate change-related erosion.
  • The Dragon’s Gaze notes that Gliese 1132b is likely a Venus analog.
  • The Dragon’s Tales wonders about Titan’s polar regions.
  • False Steps considers the Soviet plans for a substantial lunar settlement.
  • Far Outliers reports on the Czech and Slovak secret agents active in the United States during the First World War.
  • Gizmodo notes the steady spread of lakes on the surface of East Antarctica.
  • Language Hat examines the birth of the modern Uzbeks.
  • Language Log shares bilingual Spanish-Chinese signage from Argentina.
  • Marginal Revolution notes the arrival of tourists in Belgium seeking euthanasia.
  • Maximos62 shares footage from Singapore’s Festival of the Hungry Ghost.
  • Steve Munro notes the little publicity given to the 514 streetcar.
  • Justin Petrone reflects on Estonian stereotypes of Latvia.
  • pollotenchegg looks at the regional demographics of Ukraine.
  • The Russian Demographics Blog notes the inclusion of Cossacks in the Russian census.
  • Strange Maps shares a map of the actually-existing Middle East.
  • Understanding Society examines the interwar ideology of Austrofascism.
  • Window on Eurasia looks at what the Soviet coup attempt in 1991 did and did not do.

[BRIEF NOTE] On the possible detection of Proxima Centauri b

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Space artist David A. Hardy shared the above 1972 painting, of a rocky world with pools of liquid on its surface in close orbit of Proxima Centauri, soon after the news broke of the possible discovery of a broadly Earth-like planet in orbit of the star nearest to our solar system. Matt Williams’ Universe Today article “Earth-like Planet Around Proxima Centauri Discovered” has been frequently cited.

[T]he German weekly Der Spiegel announced recently that astronomers have discovered an Earth-like planet orbiting Proxima Centauri, just 4.25 light-years away. Yes, in what is an apparent trifecta, this newly-discovered exoplanet is Earth-like, orbits within it’s sun’s habitable zone, and is within our reach. But is this too good to be true? [. . . ] Citing anonymous sources, the magazine stated:

“The still nameless planet is believed to be Earth-like and orbits at a distance to Proxima Centauri that could allow it to have liquid water on its surface — an important requirement for the emergence of life. Never before have scientists discovered a second Earth that is so close by.”

In addition, they claim that the discovery was made by the European Southern Observatory (ESO) using the La Silla Observatory‘s reflecting telescope. Coincidentally, it was this same observatory that announced the discovery of Alpha Centauri Bb back in 2012, which was also declared to be “the closest exoplanet to Earth”. Unfortunately, subsequent analysis cast doubt on its existence, claiming it was a spurious artifact of the data analysis.

However, according to Der Spiegel’s unnamed source – whom they claim was involved with the La Silla team that made the find – this latest discovery is the real deal, and was the result of intensive work. “Finding small celestial bodies is a lot of hard work,” the source was quoted as saying. “We were moving at the technically feasible limit of measurement.”

The article goes on to state that the European Southern Observatory (ESO) will be announcing the finding at the end of August. But according to numerous sources, in response to a request for comment by AFP, ESO spokesman Richard Hook refused to confirm or deny the discovery of an exoplanet around Proxima Centauri. “We are not making any comment,” he is reported as saying.

The Pale Red Dot research project, devoted to the surveillance of Proxima Centauri in the search of detecting a close-orbiting planet, has reported on finding a possible signal.

From palereddit.org #exoplanets #alphacentauri #proximacentauri #palereddotA 2013 study did suggest a 10-20 day cycle of some sort. Such, the project acknowledges, may not be spoor of a planet at all but rather a function of the star or even the instruments used. Any planet more massive than one or two Earths would already have been detected, based on previous surveys.

If everything is as reported–if!–then there could well be a planet of mass comparable to that of the Earth orbiting the nearest star to our solar system within said star’s circumstellar habitable zone. That by itself would not ensure that such a planet would be like Earth, as serious constraints to the habitability of exoplanets in red dwarf systems exist. In particular, Proxima Centauri’s nature as a violent flare star means that even if a hypothetical planet did start off with the resources needed to support life, successive flares may have eroded the planet’s surface into lifeless rock.

Even so, it goes without saying that the discovery of such a world would be epoch-making. Besides the potential of this world as itself, it signals remarkable things about the wider universe. If such an uncomprisingly dim and violent star as Proxima Centauri can support even a very broadly Earth-like planet, surely planets like ours must be quite common? How likely would it be that we are not alone?

D-Brief and The Dragon’s Gaze have more. Suffice it to say I will be waiting for bated breath for more.

Written by Randy McDonald

August 15, 2016 at 10:34 pm

[BLOG] Some Monday links

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  • At Antipope, Charlie Stross describes how Brexit has forced him to rewrite his latest novel.
  • D-Brief suggests early Venus was once habitable, and notes the rumour of an Earth-like planet found around Proxima Centauri.
  • The Dragon’s Gaze notes the detection of storms of brown dwarfs.
  • The Dragon’s Tales reports on more signs of water on Mars.
  • False Steps notes an early American proposal for a space station in orbit of the Moon.
  • Language Hat talks about lost books, titles deserving broader readership.
  • The LRB Blog talks about the EU and Brexit.
  • Marginal Revolution notes a study suggesting Trump support is concentrated among people close to those who have lost out from trade.
  • Neuroskeptic reports on the story of H.M., a man who lost the ability to form new memories following a brain surgery.
  • The Volokh Conspiracy engages the idea of voting with a lesser evil.
  • Window on Eurasia notes the role of immigrants in Moscow’s economy.

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