Author Topic: Pale Red Dot  (Read 50748 times)

Offline zubenelgenubi

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Re: Pale Red Dot
« Reply #320 on: 11/04/2016 03:06 PM »
re: habitability of worlds around M-class, flaring red dwarfs

I read a Larry Niven short story, "Flare Time," set on a moon in such a system.

Then I found out the short story was part of a 1985 collaborative short story collection, "Medea: Harlan's World."  Authors also include Harlan Ellison, Jack Williamson, Frederik Pohl, Hal Clement, Thomas M Disch, Frank Herbert, Poul Anderson, Kate Wilhelm, Theodore Sturgeon, and Robert Silverburg.

The short stories stem from a 1975 UCLA seminar "10 Tuesdays Down a Rabbit Hole."

https://en.wikipedia.org/wiki/Medea:_Harlan%27s_World

I don't know if the climatology they worked out back then is still valid today--I don't remember any fatal flaws.

Has anyone gotten Niven's thoughts/observations about this discovery?
« Last Edit: 11/04/2016 03:22 PM by zubenelgenubi »
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Offline Star One

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Re: Pale Red Dot
« Reply #321 on: 11/08/2016 08:06 PM »
FIRST LIGHT FOR BREAKTHROUGH LISTEN AT PARKES TELESCOPE, AUSTRALIA

Giant Radio Telescope Turns to New-Found Nearby Planet

Breakthrough Listen to Study Proxima b

San Francisco – November 7, 2016 – Breakthrough Listen, the 10-year, $100-million astronomical search for intelligent life beyond Earth launched in 2015 by Internet entrepreneur Yuri Milner and Stephen Hawking, today announced its first observations using the Parkes Radio Telescope in New South Wales, Australia.
Parkes joins the Green Bank Telescope (GBT) in West Virginia, USA, and the Automated Planet Finder (APF) at Lick Observatory in California, USA, in their ongoing surveys to determine whether civilizations elsewhere have developed technologies similar to our own. Parkes radio telescope is part of the Australia Telescope National Facility, owned and managed by Australia’s Commonwealth Scientific and Industrial Research Organization (CSIRO).
Drawing on over nine months of experience in operation of the dedicated Breakthrough Listen instrument at GBT, a team of scientists and engineers from the University of California, Berkeley's SETI Research Center (BSRC) deployed similar hardware at Parkes, bringing Breakthrough Listen’s unprecedented search tools to a wide range of sky inaccessible from the GBT. The Southern Hemisphere sky is rich with targets, including the center of our own Milky Way galaxy, large swaths of the galactic plane, and numerous other galaxies in the nearby Universe.
‘The Dish’ at Parkes played an iconic role in receiving the first deliberate transmissions from the surface of another world, as the astronauts of Apollo 11 set foot on our Moon. Now, Parkes joins once again in expanding human horizons as we search for the answer to one of our oldest questions: Are we alone?
“The Parkes Radio Telescope is a superb instrument, with a rich history,” said Pete Worden, Chairman of Breakthrough Prize Foundation and Executive Director of the Breakthrough Initiatives. “We’re very pleased to be collaborating with CSIRO to take Listen to the next level.”
With its new combined all-sky range, superb telescope sensitivity and computing capacity, Breakthrough Listen is the most powerful, comprehensive, and intensive scientific search ever undertaken for signs of intelligent life beyond Earth.
Moreover, this expansion of Breakthrough Listen’s range follows the announcement on October 12 that it will be joining forces with the new FAST telescope – the world’s largest filled-aperture radio receiver – to coordinate their searches for artificial signals. The two programs will exchange observing plans, search methods and data, including the rapid sharing of promising new signals for additional observation and analysis. The partnership represents a major step toward establishing a fully connected, global search for intelligent life in the Universe.
“The addition of Parkes is an important milestone,” said Yuri Milner, founder of the Breakthrough Initiatives, which include Breakthrough Listen. “These major instruments are the ears of planet Earth, and now they are listening for signs of other civilizations.”
First light focused on exo-Earth

After 14 days of commissioning and test observations, first light for Breakthrough Listen at Parkes was achieved on November 7, with an observation of the newly-discovered Earth-size planet orbiting the nearest star to the Sun. Proxima Centauri, a red dwarf star 4.3 light years from Earth, is now known to have a planet ("Proxima b") within its habitable zone – the region where water could exist in liquid form on the planet’s surface. Such “exo-Earths” (habitable zone exoplanets) are among the primary targets for Breakthrough Listen.
“The chances of any particular planet hosting intelligent life-forms are probably minuscule,” said Andrew Siemion, director of UC Berkeley SETI Research Center. “But once we knew there was a planet right next door, we had to ask the question, and it was a fitting first observation for Parkes. To find a civilization just 4.2 light years away would change everything.”
As the closest known exoplanet, Proxima b is also the current primary target for Breakthrough Listen's sister initiative, Breakthrough Starshot, which is developing the technology to send gram-scale spacecraft to the nearest stars.
“Parkes is one of the most highly cited radio telescopes in the world, with a long list of achievements to its credit, including the discovery of the first ‘fast radio burst’. Parkes’ unique view of the southern sky, and cutting-edge instrumentation, means we have a great opportunity to contribute to the search for extra-terrestrial life,” said Douglas Bock, Director of CSIRO Astronomy and Space Science.
Open data policy

As with the other Breakthrough Listen telescopes, data from Parkes will be freely available to the public online. Scientists, programmers, students, and others are invited to access the Breakthrough Listen archive for scientific research purposes, including helping perfect algorithms to sift through petabytes of raw data from the telescopes, screening for interfering signals from earth-bound technology. Volunteers can also help analyze data from Parkes by donating their spare computing power as part of BSRC’s legendary SETI@home project.
Scope of Parkes observations

Breakthrough Listen at Parkes will be the most comprehensive search of the southern sky for artificial signals in six key samples:
All 43 stars (at south declinations) within 5 parsecs, at 1-15 GHz*. Sensitive to the levels of radio transmission at which signals ‘leak’ from Earth-based radar transmitters (with available receivers).
1000 stars (south) of all spectral-types (OBAFGKM) within 50 parsecs (1-4 GHz).
One Million Nearby Stars (south). In 2016-2017, first 5,000 stars; 1 minute exposure (1-4 GHz).
Galactic plane and Center (1-4 GHz).
Centers of 100 nearby galaxies (south declinations): spirals, ellipticals, dwarfs, irregulars (1-4 GHz).
Exotic sources will include white dwarfs, neutron stars, black holes, and other anomalous natural sources (1-4 GHz).
Project Leadership

Pete Worden, Chairman, Breakthrough Prize Foundation
Lord Martin Rees, Astronomer Royal, Fellow of Trinity College; Emeritus Professor of Cosmology and Astrophysics, University of Cambridge
Andrew Siemion, Director, Berkeley SETI Research Center, University of California
Dan Werthimer, Co-founder and chief scientist of the SETI@home project; director of SERENDIP; principal investigator for CASPER, University of California
Matthew Bailes, Swinburne University
João Alves, University of Vienna
Jim Cordes, Cornell University
Paul Davies, Arizona State University
Frank Drake, UC Santa Cruz
Ron Ekers, CSIRO/ATNF
Andrew Fraknoi, Foothill College
Michael Garrett, University of Manchester
John Gertz, SETI Institute
Paul Horowitz, Harvard University
Andrew Howard, University of Hawaii
Nikolai Kardashev, Russian Academy of Sciences
Joseph Lazio, NASA JPL
Di Li, Chinese National Astronomical Observatory (CAS)
Chris Lintott, Oxford University
Avi Loeb, Harvard University
Shin-ya Narusawa, Nishi-Harima Astronomical Observatory (NHAO)
Brian Schmidt, Australian National University
Sara Seager, MIT
Seth Shostak, SETI Institute
Jill Tarter, SETI Institute
Lucianne Walkowicz, Adler Planetarium
Jason Wright, Penn State University
Shelley Wright, UC San Diego
For media inquiries: media@breakthroughprize.org
or
Rubenstein Communications, Inc.
New York, New York
Janet Wootten
jwootten@rubenstein.com / +1.212.843.8024
Facebook: www.facebook.com/BreakthroughPrize/
Twitter: twitter.com/brkthroughprize
Youtube: www.youtube.com/user/breakthroughprize

Offline Star One

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Re: Pale Red Dot
« Reply #322 on: 11/12/2016 06:36 PM »
Another planet around another nearby red dwarf.

Quote
And it seems the trend is likely to continue, with the latest discovery comes from a team of European scientists. Using data from the ESO’s High Accuracy Radial velocity Planet Searcher (HARPS) and HARPS-N instruments, they detected an exoplanet candidate orbiting around GJ 536 – an M-class red dwarf star located about 32.7 light years (10.03 parsecs) from Earth.

According to their study, “A super-Earth Orbiting the Nearby M-dwarf GJ 536“, this planet is a super-Earth – a class of exoplanet that has between more than one, but less than 15, times the mass of Earth. In this case, the planet boasts a minimum of 5.36 ± 0.69 Earth masses, has an orbital period of 8.7076 ± 0.0025 days, and orbits its sun at a distance of 0.06661 AU.

http://www.universetoday.com/131879/discovery-nearby-super-earth-5-times-mass/

Paper.

https://arxiv.org/pdf/1611.02122v1.pdf

Offline hop

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Re: Pale Red Dot
« Reply #323 on: 11/17/2016 03:53 AM »
Paper arguing the Proxima is indeed bound to A and B: https://arxiv.org/abs/1611.03495
Quote
Proxima and Alpha Centauri AB have almost identical distances and proper motions with respect to the Sun. Although the probability of such similar parameters is in principle very low, the question whether they actually form a single gravitationally bound triple system has been open since the discovery of Proxima one century ago. Owing to recent high precision radial velocity measurements and the revision of the parameters of the Alpha Cen pair, we show that Proxima and Alpha Cen are gravitationally bound with a high degree of confidence. The orbital period of Proxima is approximately 600 000 years, with a moderate excentricity of 0.42 +0.07 -0.08. Proxima comes within 5.3 -0.9 +1.2 kAU of Alpha Cen at periastron, and the apastron occurs at 12.9 +0.3 -0.1 kAU. This orbital motion may have influenced the formation or evolution of the recently discovered planet orbiting Proxima as well as circumbinary planet formation around Alpha Cen.

There's also a summary on astrobites https://astrobites.org/2016/11/16/settling-the-proxima-centauri-question/

Online redliox

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Re: Pale Red Dot
« Reply #324 on: 11/17/2016 07:29 AM »
Paper arguing the Proxima is indeed bound to A and B: https://arxiv.org/abs/1611.03495

The paper says that Proxima should be the same age and material as AB.  In turn this implies their exoplanets would also be kin to each other.  This would make them an interesting study on extreme planetary formation.
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Offline Star One

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Re: Pale Red Dot
« Reply #325 on: 02/08/2017 07:05 PM »
NASA Finds Planets of Red Dwarf Stars May Face Oxygen Loss in Habitable Zones
The search for life beyond Earth starts in habitable zones, the regions around stars where conditions could potentially allow liquid water – which is essential for life as we know it – to pool on a planet’s surface. New NASA research suggests some of these zones might not actually be able to support life due to frequent stellar eruptions – which spew huge amounts of stellar material and radiation out into space – from young red dwarf stars.

Now, an interdisciplinary team of NASA scientists wants to expand how habitable zones are defined, taking into account the impact of stellar activity, which can threaten an exoplanet’s atmosphere with oxygen loss. This research was published in The Astrophysical Journal Letters on Feb. 6, 2017.

"If we want to find an exoplanet that can develop and sustain life, we must figure out which stars make the best parents,” said Vladimir Airapetian, lead author of the paper and a solar scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “We’re coming closer to understanding what kind of parent stars we need.”

To determine a star’s habitable zone, scientists have traditionally considered how much heat and light the star emits. Stars more massive than our sun produce more heat and light, so the habitable zone must be farther out. Smaller, cooler stars yield close-in habitable zones.

But along with heat and visible light, stars emit X-ray and ultraviolet radiation, and produce stellar eruptions such as flares and coronal mass ejections – collectively called space weather. One possible effect of this radiation is atmospheric erosion, in which high-energy particles drag atmospheric molecules – such as hydrogen and oxygen, the two ingredients for water – out into space. Airapetian and his team's new model for habitable zones now takes this effect into account.


In this artist’s concept, X-ray and extreme ultraviolet light from a young red dwarf star cause ions to escape from an exoplanet’s atmosphere. Scientists have developed a model that estimates the oxygen ion escape rate on planets around red dwarfs, which plays an important role in determining an exoplanet’s habitability.
Credits: NASA Goddard/Conceptual Image Lab, Michael Lentz, animator/Genna Duberstein, producer
Download this video in HD formats from NASA Goddard's Scientific Visualization Studio
The search for habitable planets often hones in on red dwarfs, as these are the coolest, smallest and most numerous stars in the universe – and therefore relatively amenable to small planet detection.

"On the downside, red dwarfs are also prone to more frequent and powerful stellar eruptions than the sun," said William Danchi, a Goddard astronomer and co-author of the paper. "To assess the habitability of planets around these stars, we need to understand how these various effects balance out."

Another important habitability factor is a star's age, say the scientists, based on observations they've gathered from NASA’s Kepler mission. Every day, young stars produce superflares, powerful flares and eruptions at least 10 times more powerful than those observed on the sun. On their older, matured counterparts resembling our middle-aged sun today, such superflares are only observed once every 100 years.

“When we look at young red dwarfs in our galaxy, we see they’re much less luminous than our sun today,” Airapetian said. “By the classical definition, the habitable zone around red dwarfs must be 10 to 20 times closer-in than Earth is to the sun. Now we know these red dwarf stars generate a lot of X-ray and extreme ultraviolet emissions at the habitable zones of exoplanets through frequent flares and stellar storms.”

Superflares cause atmospheric erosion when high-energy X-ray and extreme ultraviolet emissions first break molecules into atoms and then ionize atmospheric gases. During ionization, radiation strikes the atoms and knocks off electrons. Electrons are much lighter than the newly formed ions, so they escape gravity’s pull far more readily and race out into space.

Opposites attract, so as more and more negatively charged electrons are generated, they create a powerful charge separation that lures positively charged ions out of the atmosphere in a process called ion escape.

“We know oxygen ion escape happens on Earth at a smaller scale since the sun exhibits only a fraction of the activity of younger stars,” said Alex Glocer, a Goddard astrophysicist and co-author of the paper. “To see how this effect scales when you get more high-energy input like you’d see from young stars, we developed a model.”

The model estimates the oxygen escape on planets around red dwarfs, assuming they don’t compensate with volcanic activity or comet bombardment. Various earlier atmospheric erosion models indicated hydrogen is most vulnerable to ion escape. As the lightest element, hydrogen easily escapes into space, presumably leaving behind an atmosphere rich with heavier elements such as oxygen and nitrogen.

But when the scientists accounted for superflares, their new model indicates the violent storms of young red dwarfs generate enough high-energy radiation to enable the escape of even oxygen and nitrogen – building blocks for life’s essential molecules.   

“The more X-ray and extreme ultraviolet energy there is, the more electrons are generated and the stronger the ion escape effect becomes,” Glocer said. “This effect is very sensitive to the amount of energy the star emits, which means it must play a strong role in determining what is and is not a habitable planet.”

Considering oxygen escape alone, the model estimates a young red dwarf could render a close-in exoplanet uninhabitable within a few tens to a hundred million years. The loss of both atmospheric hydrogen and oxygen would reduce and eliminate the planet’s water supply before life would have a chance to develop.

“The results of this work could have profound implications for the atmospheric chemistry of these worlds,” said Shawn Domagal-Goldman, a Goddard space scientist not involved with the study. “The team’s conclusions will impact our ongoing studies of missions that would search for signs of life in the chemical composition of those atmospheres.”

Modeling the oxygen loss rate is the first step in the team’s efforts to expand the classical definition of habitability into what they call space weather-affected habitable zones. When exoplanets orbit a mature star with a mild space weather environment, the classical definition is sufficient. When the host star exhibits X-ray and extreme ultraviolet levels greater than seven to 10 times the average emissions from our sun, then the new definition applies. The team’s future work will include modeling nitrogen escape, which may be comparable to oxygen escape since nitrogen is just slightly lighter than oxygen.

The new habitability model has implications for the recently discovered planet orbiting the red dwarf Proxima Centauri, our nearest stellar neighbor. Airapetian and his team applied their model to the roughly Earth-sized planet, dubbed Proxima b, which orbits Proxima Centauri 20 times closer than Earth is to the sun.

Considering the host star’s age and the planet’s proximity to its host star, the scientists expect that Proxima b is subjected to torrents of X-ray and extreme ultraviolet radiation from superflares occurring roughly every two hours. They estimate oxygen would escape Proxima b’s atmosphere in 10 million years. Additionally, intense magnetic activity and stellar wind – the continuous flow of charged particles from a star – exacerbate already harsh space weather conditions. The scientists concluded that it’s quite unlikely Proxima b is habitable.   

“We have pessimistic results for planets around young red dwarfs in this study, but we also have a better understanding of which stars have good prospects for habitability,” Airapetian said. “As we learn more about what we need from a host star, it seems more and more that our sun is just one of those perfect parent stars, to have supported life on Earth.”

Related:

Solar Storms May Have Been Key to Life on Earth
ESO Discovers Earth-Size Planet in Habitable Zone of Nearest Star
NASA's Swift Mission Observes Mega Flares from a Mini Star
In the Zone: How Scientists Search for Habitable Planets
Lina Tran
NASA's Goddard Space Flight Center, Greenbelt, Md.
Last Updated: Feb. 8, 2017
Editor: Rob Garner

Offline Vultur

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Re: Pale Red Dot
« Reply #326 on: 02/09/2017 02:31 AM »
Something I've been wondering about for a while, though - what does that intense radiation do to the planet's surface?

I've read that water ice gets dissociated on Europa's surface by radiation from Jupiter's radiation belt, making oxygen which forms an ultra-super-thin ~picobar O2 "atmosphere" which hardly deserves the name. But Europa's gravity is pretty limited - even less than our Moon's, not enough to really hold an atmosphere.

So I'm wondering if an Earth-size planet's surface might get altered by radiation, releasing enough gas to replenish some sort of atmosphere (maybe not a habitable one)? Or is the radiation involved not that intense? I guess breaking O2 out of SiO2 would be really hard...

Offline Star One

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Re: Pale Red Dot
« Reply #327 on: 02/13/2017 03:33 PM »
Finding Proxima b: the 'planet hunters' searching for signs of alien life around nearby stars

http://www.wired.co.uk/article/the-pale-red-dot-proxima-centauri-could-be-home-to-extraterrestrial-life

Offline Star One

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Pale Red Dot
« Reply #328 on: 02/14/2017 07:28 PM »
The cosmic shoreline: the evidence that escape determines which planets have atmospheres, and what this may mean for Proxima Centauri b

Kevin J. Zahnle, David C. Catling
(Submitted on 11 Feb 2017)
Quote
The planets of the Solar System divide neatly between those with atmospheres and those without when arranged by insolation (I) and escape velocity (vesc). The dividing line goes as I∝v4esc. Exoplanets with reported masses and radii are shown to crowd against the extrapolation of the Solar System trend, making a metaphorical cosmic shoreline that unites all the planets. The I∝v4esc relation may implicate thermal escape. We therefore address the general behavior of hydrodynamic thermal escape models ranging from Pluto to highly-irradiated Extrasolar Giant Planets (EGPs). Energy-limited escape is harder to test because copious XUV radiation is mostly a feature of young stars, and hence requires extrapolating to historic XUV fluences (Ixuv) using proxies and power laws. An energy-limited shoreline should scale as Ixuv∝v3escρ√, which differs distinctly from the apparent Ixuv∝v4esc relation. Energy-limited escape does provide good quantitative agreement to the highly irradiated EGPs. Diffusion-limited escape implies that no planet can lose more than 1% of its mass as H2. Impact erosion, to the extent that impact velocities vimp can be estimated for exoplanets, fits to a vimp≈4−5vesc shoreline. The proportionality constant is consistent with what the collision of comet Shoemaker-Levy 9 showed us we should expect of modest impacts in deep atmospheres. With respect to the shoreline, Proxima Centauri b is on the metaphorical beach. Known hazards include its rapid energetic accretion, high impact velocities, its early life on the wrong side of the runaway greenhouse, and Proxima Centauri's XUV radiation. In its favor is a vast phase space of unknown unknowns.

https://arxiv.org/abs/1702.03386
« Last Edit: 02/14/2017 07:29 PM by Star One »

Online sghill

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Re: Pale Red Dot
« Reply #329 on: 02/15/2017 01:56 PM »
More about Ion Escape.

I read this as bad news for critters on Proxima B.

Likely it's a UV blasted rock....

http://iopscience.iop.org/article/10.3847/2041-8213/836/1/L3

Abstract
Atmospheres of exoplanets in the habitable zones around active young G-K-M stars are subject to extreme X-ray and EUV (XUV) fluxes from their host stars that can initiate atmospheric erosion. Atmospheric loss affects exoplanetary habitability in terms of surface water inventory, atmospheric pressure, the efficiency of greenhouse warming, and the dosage of the UV surface irradiation. Thermal escape models suggest that exoplanetary atmospheres around active K-M stars should undergo massive hydrogen escape, while heavier species including oxygen will accumulate forming an oxidizing atmosphere. Here, we show that non-thermal oxygen ion escape could be as important as thermal, hydrodynamic H escape in removing the constituents of water from exoplanetary atmospheres under supersolar XUV irradiation. Our models suggest that the atmospheres of a significant fraction of Earth-like exoplanets around M dwarfs and active K stars exposed to high XUV fluxes will incur a significant atmospheric loss rate of oxygen and nitrogen, which will make them uninhabitable within a few tens to hundreds of Myr, given a low replenishment rate from volcanism or cometary bombardment. Our non-thermal escape models have important implications for the habitability of the Proxima Centauri's terrestrial planet.
« Last Edit: 02/15/2017 01:57 PM by sghill »
Bring the thunder Elon!

Offline Alpha_Centauri

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Re: Pale Red Dot
« Reply #330 on: 03/20/2017 06:02 PM »
This one is interesting, it considers what can be accomplished with the existing ESO VLT observatory with feasible upgrades to operational (SPHERE) and under-construction (EXPRESSO) instruments:

Atmospheric characterization of Proxima b by coupling the SPHERE high-contrast imager to the ESPRESSO spectrograph

...
Big question though is how much would this change cost.

A bit more detail here.  Appears they have applied for funding, no idea whether they have secured it though.  Plan was to be ready for end of 2020.

https://obswww.unige.ch/people/christophe.lovis/SPHERE-ESPRESSO_Lovis.pdf

Offline Star One

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Pale Red Dot
« Reply #331 on: 04/28/2017 07:14 PM »
The full spectral radiative properties of Proxima Centauri

Quote
The discovery of Proxima b, a terrestrial temperate planet, presents the opportunity of studying a potentially habitable world in optimal conditions. A key aspect to model its habitability is to understand the radiation environment of the planet in the full spectral domain. We characterize the X-rays to mid-IR radiative properties of Proxima with the goal of providing the top-of-atmosphere fluxes on the planet. We also aim at constraining the fundamental properties of the star. We employ observations from a large number of facilities and make use of different methodologies to piece together the full spectral energy distribution of Proxima. In the high-energy domain, we pay particular attention to the contribution by rotational modulation, activity cycle, and flares so that the data provided are representative of the overall radiation dose received by the atmosphere of the planet. We present the full spectrum of Proxima covering 0.7 to 30000 nm. The integration of the data shows that the top-of-atmosphere average XUV irradiance on Proxima b is 0.293 W m^-2, i.e., nearly 60 times higher than Earth, and that the total irradiance is 877+/-44 W m^-2, or 64+/-3% of the solar constant but with a significantly redder spectrum. We also provide laws for the XUV evolution of Proxima corresponding to two scenarios. Regarding the fundamental properties of Proxima, we find M=0.120+/-0.003 Msun, R=0.146+/-0.007 Rsun, Teff=2980+/-80 K, and L=0.00151+/-0.00008 Lsun. In addition, our analysis reveals a ~20% excess in the 3-30 micron flux of the star that is best interpreted as arising from warm dust in the system. The data provided here should be useful to further investigate the current atmospheric properties of Proxima b as well as its past history, with the overall aim of firmly establishing the habitability of the planet.

https://arxiv.org/abs/1704.08449

Does this indicate anything in particular as regards the habitability of Proxima b?
« Last Edit: 04/28/2017 07:16 PM by Star One »

Offline Hungry4info3

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Re: Pale Red Dot
« Reply #332 on: 04/28/2017 09:12 PM »
From the paper

"If we assume synchronous rotation, our estimates indicate that Proxima b could have lost 0.47 Earth-oceans to 1.07 Earth-oceans between 10 Myr and 90 Myr, when it reached the inner edge of the habitable zone at 1.5 x Earth-insolation. Our new calculations therefore suggest that, during that time, Proxima b may have lost more water than previously estimated by Ribas (2016), by about a factor of 1.25 to 3. Assuming non-synchronous rotation, the amount of water lost could range from 0.9 Earth-oceans to 1.91 Earth-oceans between 10 Myr and 200 Myr, when it reached the habitable zone inner edge at 0.9 x Earth-insolation."

"In spite of the strong volatile loses, the planet could still have a significant amount of water reservoir when it entered the habitable zone deepening on the initial content. What could have occurred beyond this point is uncertain. If we assume that the water loss processes were still active upon entering the habitable zone, we find that Proxima b could have lost up to 15-20 Earth-oceans during its lifetime. However this needs to be considered an extreme upper limit because the volatile loss mechanics would probably be significantly less efficient under such conditions."

Offline Star One

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Pale Red Dot
« Reply #333 on: 05/16/2017 08:11 AM »
Proxima B: Our closest neighbouring exoplanet could host 'alien life' climate models suggest

Climate simulations have revealed Proxima B could have liquid water on its surface.

http://www.ibtimes.co.uk/proxima-b-our-closest-neighbouring-exoplanet-could-host-alien-life-climate-models-suggest-1621694

This should be noted.

Quote
"Our model is better able to take into account the variations in radiation received by the planet due to its orbit than previous models. We find that in the right conditions, Proxima B could have liquid water on its surface and could be habitable. Our model does suffer from limitations, notably we have simply assumed that the planet has an earth-like atmosphere", Nathan Mayne told IBTimes UK.

"It's interesting for us to see that when we change a given parameter (over a reasonable range), the simulated climate and temperatures do not change that much. Proxima B could benefit from a remarkably stable climate regime".

Here's the paper in question.

https://arxiv.org/pdf/1702.08463.pdf
« Last Edit: 05/16/2017 08:20 AM by Star One »

Offline Star One

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Re: Pale Red Dot
« Reply #334 on: 07/16/2017 01:59 PM »
Arecibo observatory joins Red Dots today for simultaneous observations of Barnard’s star

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The National Science Foundation’s Arecibo Observatory and the Planetary Habitability Laboratory of the University of Puerto Rico at Arecibo joins forces with Red Dots today to learn a bit more about the nearest red-dwarfs and its possible planets. This collaboration will simultaneously observe in both the optical and radio spectrum Barnard’s Star, a popular star in the science fiction literature. Next week we will have a few more articles here on Red Dots on the history of this remarkable star (featuring a special guest article by Centauri Dream‘s author Paul Gilster). Those adept to science fiction literature may recall that Arecibo’s telescope is the mythical observatory where Dr. Ellie Harroway starts her Search for Extra Terrestrial Intelligence (or SETI) in Carl Sagan’s novel and film Contact, so the execution of these coordinated observations is a special event for us.

Observations on Barnard’s star will last for about 1.5 hours and they will be carried out at the so-called C-band, which corresponds to frequencies between 4 to 5 GHz. For comparison, kitchen microwave ovens work at frequencies of about 2.5 GHz. These will be complemented with spectra, and photometric monitoring with the follow-up facilities already being used in Red Dots including;  SNO, LCO, TJO, and CARMENES. Data might also be obtained with ESO’s HARPS, but the weather forecast at La Silla is not promising today.

https://reddots.space/arecibo-observatory-joins-red-dots-today-for-simultaneous-observations-of-barnards-star/

Offline Alpha_Centauri

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Re: Pale Red Dot
« Reply #335 on: 10/05/2017 01:46 PM »
https://www.twitter.com/RedDotsSpace/status/915922545643278337

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Data collection finished! Final articles and reports in the next few days. Stay tunned #proximab #barnards #ross154
« Last Edit: 10/05/2017 10:41 PM by Alpha_Centauri »

Offline Star One

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Pale Red Dot
« Reply #336 on: 10/05/2017 04:40 PM »
Further to the above is another tweet.

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Pale Red Dot @Pale_red_dot
It's true! Do you want to learn about possible siblings to #proximab All data available soon. Get ready to join the discussions with @reddotsspace #reddots

https://mobile.twitter.com/Pale_red_dot/status/915925141808394243
« Last Edit: 10/05/2017 04:40 PM by Star One »

Offline jebbo

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Re: Pale Red Dot
« Reply #337 on: 10/07/2017 07:52 AM »

Offline hop

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Re: Pale Red Dot
« Reply #338 on: 11/03/2017 01:10 AM »
Hints of a Kuiper belt analog and possibly other stuff around Proxima Centauri

ALMA Discovery of Dust Belts Around Proxima Centauri Guillem Anglada et al accepted for publication in The Astrophysical Journal Letters

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Proxima Centauri, the star closest to our Sun, is known to host at least one terrestrial planet candidate in a temperate orbit. Here we report the ALMA detection of the star at 1.3 mm wavelength and the discovery of a belt of dust orbiting around it at distances ranging between 1 and 4 au, approximately. Given the low luminosity of the Proxima Centauri star, we estimate a characteristic temperature of about 40 K for this dust, which might constitute the dust component of a small-scale analog to our solar system Kuiper belt. The estimated total mass, including dust and bodies up to 50 km in size, is of the order of 0.01 Earth masses, which is similar to that of the solar Kuiper belt. Our data also show a hint of warmer dust closer to the star. We also find signs of two additional features that might be associated with the Proxima Centauri system, which, however, still require further observations to be confirmed: an outer extremely cold (about 10 K) belt around the star at about 30 au, whose orbital plane is tilted about 45 degrees with respect to the plane of the sky; and additionally, we marginally detect a compact 1.3 mm emission source at a projected distance of about 1.2 arcsec from the star, whose nature is still unknown.

Offline Star One

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Pale Red Dot
« Reply #339 on: 11/03/2017 04:41 PM »
eso1735 — Science Release
ALMA Discovers Cold Dust Around Nearest Star


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The ALMA Observatory in Chile has detected dust around the closest star to the Solar System, Proxima Centauri. These new observations reveal the glow coming from cold dust in a region between one to four times as far from Proxima Centauri as the Earth is from the Sun. The data also hint at the presence of an even cooler outer dust belt and may indicate the presence of an elaborate planetary system. These structures are similar to the much larger belts in the Solar System and are also expected to be made from particles of rock and ice that failed to form planets.

Proxima Centauri is the closest star to the Sun. It is a faint red dwarf lying just four light-years away in the southern constellation of Centaurus (The Centaur). It is orbited by the Earth-sized temperate world Proxima b, discovered in 2016 and the closest planet to the Solar System. But there is more to this system than just a single planet. The new ALMA observations reveal emission from clouds of cold cosmic dust surrounding the star.

The lead author of the new study, Guillem Anglada [1], from the Instituto de Astrofísica de Andalucía (CSIC), Granada, Spain, explains the significance of this find: “The dust around Proxima is important because, following the discovery of the terrestrial planet Proxima b, it’s the first indication of the presence of an elaborate planetary system, and not just a single planet, around the star closest to our Sun.”

Dust belts are the remains of material that did not form into larger bodies such as planets. The particles of rock and ice in these belts vary in size from the tiniest dust grain, smaller than a millimetre across, up to asteroid-like bodies many kilometres in diameter [2].

Dust appears to lie in a belt that extends a few hundred million kilometres from Proxima Centauri and has a total mass of about one hundredth of the Earth’s mass. This belt is estimated to have a temperature of about –230 degrees Celsius, as cold as that of the Kuiper Belt in the outer Solar System.

There are also hints in the ALMA data of another belt of even colder dust about ten times further out. If confirmed, the nature of an outer belt is intriguing, given its very cold environment far from a star that is cooler and fainter than the Sun. Both belts are much further from Proxima Centauri than the planet Proxima b, which orbits at just four million kilometres from its parent star [3].

Guillem Anglada explains the implications of the discovery: “This result suggests that Proxima Centauri may have a multiple planet system with a rich history of interactions that resulted in the formation of a dust belt. Further study may also provide information that might point to the locations of as yet unidentified additional planets.”

Proxima Centauri's planetary system is also particularly interesting because there are plans — the Starshot project — for future direct exploration of the system with microprobes attached to laser-driven sails. A knowledge of the dust environment around the star is essential for planning such a mission.

https://www.eso.org/public/news/eso1735/

« Last Edit: 11/03/2017 04:44 PM by Star One »

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