ALMA data reveal that a powerful stellar flare erupted from Proxima Centauri last March. This space weather may make that system rather inhospitable to life after all.
News of a major stellar flare from Proxima Centauri is interesting because flares like these are problematic for habitability. Moreover, this one may tell us something about the nature of the planetary system around this star, making us rethink previous evidence for dust belts there.But back to the habitability question. Can red dwarf stars sustain life in a habitable zone much closer to the primary than in our own Solar System, when they are subject to such violent outbursts? What we learn in a new paper from Meredith MacGregor and Alycia Weinberger (Carnegie Institution for Science) is that the flare at its peak on March 24, 2017 was 10 times brighter than the largest flares our G-class Sun produces at similar wavelengths (1.3 mm).
Proxima b is a terrestrial-mass planet in the habitable-zone of Proxima Centauri. Proxima Centauri's high stellar activity however casts doubt on the habitability of Proxima b: sufficiently bright and frequent flares and any associated proton events may destroy the planet's ozone layer, allowing lethal levels of UV flux to reach its surface. In March 2016, the Evryscope observed the first naked-eye-visible superflare detected from Proxima Centauri. Proxima increased in brightness by a factor of ~68 during the superflare and released a bolometric energy of 10^33.5 erg, ~10X larger than any previously-detected flare from Proxima. Over the last two years the Evryscope has recorded 23 other large Proxima flares ranging in bolometric energy from 10^30.6 erg to 10^32.4 erg; coupling those rates with the single superflare detection, we predict at least five superflares occur each year. Simultaneous high-resolution HARPS spectroscopy during the Evryscope superflare constrains the superflare's UV spectrum and any associated coronal mass ejections. We use these results and the Evryscope flare rates to model the photochemical effects of NOx atmospheric species generated by particle events from this extreme stellar activity, and show that the repeated flaring is sufficient to reduce the ozone of an Earth-like atmosphere by 90% within five years. We estimate complete depletion occurs within several hundred kyr. The UV light produced by the Evryscope superflare therefore reached the surface with ~100X the intensity required to kill simple UV-hardy microorganisms, suggesting that life would struggle to survive in the areas of Proxima b exposed to these flares.
The TRAPPIST-1 system provides an exquisite laboratory for understanding exoplanetary atmospheres and interiors. Their mutual gravitational interactions leads to transit timing variations, from which Grimm et al. (2018) recently measured the planetary masses with precisions ranging from 5% to 12%. Using these masses and the <5% radius measurements on each planet, we apply the method described in Suissa et al. (2018) to infer the minimum and maximum CRF (core radius fraction) of each planet. Further, we modify the maximum limit to account for the fact that a light volatile envelope is excluded for planets b through f. Only planet e is found to have a significant probability of having a non-zero minimum CRF, with a 0.7% false-alarm probability it has no core. Our method further allows us to measure the CRF of planet e to be greater than (49 +/- 7)% but less than (72 +/- 2)%, which is compatible with that of the Earth. TRAPPIST-1e therefore possess a large iron core similar to the Earth, in addition to being Earth-sized and located in the temperature zone.
Attention #reddoters! New observing campaign starting today at HARPS @ESO. Updates on science work and follow-up opportunities to follow!
https://twitter.com/RedDotsSpace/status/1015712357392306176QuoteAttention #reddoters! New observing campaign starting today at HARPS @ESO. Updates on science work and follow-up opportunities to follow!
Starting today to september 30th. New 3 targets : GJ 887 #10 nearest star-system, GJ 1061 #20, GJ 54.1 #21. Contributed observations welcome! @AAVSO call with details to be issued in short.
Oh, maybe not including proxima this time;https://twitter.com/RedDotsSpace/status/1015920018687750145QuoteStarting today to september 30th. New 3 targets : GJ 887 #10 nearest star-system, GJ 1061 #20, GJ 54.1 #21. Contributed observations welcome! @AAVSO call with details to be issued in short.
Just a cosmic hop, skip and jump away, an Earth-size planet orbits the closest star to our sun, Proxima Centauri.Ever since the discovery of the exoplanet — known as Proxima Centauri b— in 2016, people have wondered whether it could be capable of sustaining life.Now, using computer models similar to those used to study climate change on Earth, researchers have found that, under a wide range of conditions, Proxima Centauri b can sustain enormous areas of liquid water on its surface, potentially raising its prospects for harboring living organisms. [9 Strange, Scientific Excuses for Why Humans Haven't Found Aliens Yet]"The major message from our simulations is that there's a decent chance that the planet would be habitable," said Anthony Del Genio, a planetary scientist at the NASA Goddard Institute for Space Studies in New York City. Del Genio is also the lead author of a paper describing the new research, which was published Sept. 5 in the journal Astrobiology.
Conversational piece. Hopefully data from either JWST or the upcoming large new observatories on Earth can conclude Proxima's living condition. I've heard speculations that go either way to Earthlike or dead.
Quote from: redliox on 09/12/2018 09:24 pmConversational piece. Hopefully data from either JWST or the upcoming large new observatories on Earth can conclude Proxima's living condition. I've heard speculations that go either way to Earthlike or dead.Do you think only AI driven searches of data even on these large telescopes are going to be the only way to turn up transit events because of the difficulty of the target?
The Closest Exoplanet to Earth Could Be 'Highly Habitable'...https://www.livescience.com/63546-proxima-b-nearest-exoplanet-habitable.html
But the new simulations were more comprehensive than prior ones; they also included a dynamic, circulating ocean, which was able to transfer heat from one side of the exoplanet to the other very effectively. In the researchers' findings, the movement of the atmosphere and ocean combined so that "even though the night side never sees any starlight, there's a band of liquid water that's sustained around the equatorial region," Del Genio told Live Science.He likened this heat circulation to our own planet's seaside climates. The U.S. East Coast is balmier than it would be otherwise, he said, because the Gulf Stream carries warm water up from the tropics. In California, by contrast, ocean currents bring cold water down from the North, and the West Coast is colder than it otherwise would be, Del Genio added.
Quote from: Star One on 09/12/2018 06:57 pm The Closest Exoplanet to Earth Could Be 'Highly Habitable'...https://www.livescience.com/63546-proxima-b-nearest-exoplanet-habitable.htmlThis is fascinating! another exerpt from the article:QuoteBut the new simulations were more comprehensive than prior ones; they also included a dynamic, circulating ocean, which was able to transfer heat from one side of the exoplanet to the other very effectively. In the researchers' findings, the movement of the atmosphere and ocean combined so that "even though the night side never sees any starlight, there's a band of liquid water that's sustained around the equatorial region," Del Genio told Live Science.He likened this heat circulation to our own planet's seaside climates. The U.S. East Coast is balmier than it would be otherwise, he said, because the Gulf Stream carries warm water up from the tropics. In California, by contrast, ocean currents bring cold water down from the North, and the West Coast is colder than it otherwise would be, Del Genio added.Myself a Californian who is much more comfortable in the warmer waters of Massachusetts I can attest to this fact.This is all well and good, but what about the enormous stellar flares?
Quote from: jbenton on 09/15/2018 12:22 amThis is all well and good, but what about the enormous stellar flares?I’d hope they’ve accounted for that otherwise these simulations would be worthless.
This is all well and good, but what about the enormous stellar flares?
Quote from: Star One on 09/15/2018 11:16 amQuote from: jbenton on 09/15/2018 12:22 amThis is all well and good, but what about the enormous stellar flares?I’d hope they’ve accounted for that otherwise these simulations would be worthless.It's not just the flares that are problematic. M-dwarfs are VERY active when descending the Hiyashi track to become main sequence stars, and this takes ~100 MY. During this time there is HUGE volatile loss (water etc), so whether any planet starts with an ocean is very dependent on the initial conditions ... to be left with any water you have to start with a LOT and it is unclear if there is a good delivery mechanism for so much.Hence, I'm pessimistic on the habitability of M-dwarf planets (not ruling it out, but I suspect it is a rare case). On Proxima b in particular, I'm dubious given it is rather active. The Trappist-1 planets feel like a better betHowever, all this is dependent on initial conditions once planets have formed and the star turns on. And I don't think we know enough go be certain ...--- Tony