Astronomers find tantalizing hints of a potentially habitable exoplanet

Nov 08, 2012 by Jason Major, Universe Today
The star HD 40307 is thought to host at least 6 exoplanet candidates… one of them well within its habitable zone. Credit: G. Anglada/Celestia

Located 43 light-years away in the southern constellation Pictor, the orange-colored dwarf star HD 40307 has previously been found to hold three "super-Earth" exoplanets in close orbit. Now, a team of researchers poring over data from ESO's HARPS planet-hunting instrument are suggesting that there are likely at least six super-Earth exoplanets orbiting HD 40307—with one of them appearing to be tucked neatly into the star's water-friendly "Goldilocks" zone.

(High Accuracy Radial velocity Planet Searcher) on ESO's La Silla 3.6m telescope is a dedicated hunter, able to detect the oh-so-slight wobble of a star caused by the of orbiting planets. Led by Mikko Tuomi of the UK's University of Hertfordshire Centre for Astrophysics Research, a team of researchers reviewed publicly-available data from HARPS and has identified what seems to be three new exoplanets in the HD 40307 systems. The candidates, designated with the letters e, f, and g, all appear to be "" worlds… but the last one, HD 40307 g, is what's getting people excited, as the team has calculated it to be orbiting well within the region where could exist on its surface—this particular star's .

In addition, HD 40307 g is located far enough away from its star to likely not be tidally locked, according to the team's paper. This means it wouldn't have one side subject to constant heat and radiation while its other "far side" remains cold and dark, thus avoiding the intense variations in global climate, weather and winds that would come as a result.

"If the signal corresponding to HD 40307 g is a genuine Doppler signal of planetary origin, this candidate planet might be capable of supporting liquid water on its surface according to the current definition of the liquid water habitable zone around a star and is not likely to suffer from tidal locking." (Tuomi et al.)

If HD 40307 g is indeed confirmed, it may very well get onto the official short list of potentially habitable worlds outside our Solar System—although those others are quite a bit closer to the mass of our own planet.

While the other planetary candidates in the HD 40307 system are positioned much more closely to the star, with b, c, d, and e within or at the equivalent orbital distance of Mercury, g appears to be in the star's liquid-water habitable zone, orbiting at 0.6 AU in an approximately 200-day-long orbit. At this distance the estimated 7-Earth-mass exoplanet receives around 62% of the radiation that Earth gets from the Sun.

Representation of the liquid water habitable zone around HD 40307 compared to our Solar System. Credit: Tuomi et al.

Although news like this is exciting, as we're always eagerly anticipating the announcement of a true, terrestrial Earthlike world that could be host to life as we know it, it's important to remember that HD 40307 g is still a candidate—more observations are needed to not only confirm its existence but also to find out exactly what kind of planet it may be.

"A more detailed characterization of this candidate is very unlikely using ground based studies because it is very unlikely [sic] to transit the star, and a direct imaging mission seems the most promising way of learning more about its possible atmosphere and life-hosting capabilities," the team reports.

Still, just finding potential Earth-sized worlds in a system like HD 40307′s is a big deal for planetary scientists. This system is not like ours, yet somewhat similar planets have still formed… that in itself is a clue to what else may be out there.

"The planetary system around HD 40307 has an architecture radically different from that of the solar system… which indicates that a wide variety of formation histories might allow the emergence of roughly Earth-mass objects in the habitable zones of stars."

The team's paper will be published in the journal Astronomy & Astrophysics.

Another researcher on the team, Guillem Anglada-Escudé of Germany's Universität Göttingen, assembled this tour of the HD 40307 system (not including g) via Celestia.

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Explore further: Astronomer confirms a new "Super-Earth" planet

More information: arxiv.org/pdf/1211.1617v1.pdf

Press release

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Sonhouse
4 / 5 (2) Nov 08, 2012
It sounds to me a system waiting for a shift in planets. Our system has the big guys safely out away from the inner planets. If this system holds true, it looks to me like not a great place to send people with the idea of starting a colony, however long in the future that might be, could that system possibly be stable with so many giants close to its sun?
antialias_physorg
3.5 / 5 (4) Nov 08, 2012
it looks to me like not a great place to send people with the idea of starting a colony

Don't worry. 7 earth masses isn't habitable for humans (even if it does have water and/or an atmosphere that would suit us)?

could that system possibly be stable with so many giants close to its sun?

Stability is pobably not really an issue. If you really want to settle anywhere you'd need to plan ahead for 10000 years at most (100000 if you're really paranoid). On those kinds of timescales the system is stable. Anything beyond such a timeframe means that you'd either be able to deal with the instability or have moved off somewhere else.
Sonhouse
4.7 / 5 (7) Nov 08, 2012
7 Earth masses does not mean its a killer planet until we get data on the radius. If it is large enough, surface gravity could be within human tolerance. If it is the size of the moon all bets are off. Gravity at 10 g or something? NEXT:)
Peteri
4 / 5 (6) Nov 08, 2012
It sounds to me a system waiting for a shift in planets. Our system has the big guys safely out away from the inner planets. If this system holds true, it looks to me like not a great place to send people with the idea of starting a colony, however long in the future that might be, could that system possibly be stable with so many giants close to its sun?


At 253 trillion miles there's not a snowball's hope in hell of humans ever setting up a colony in the HD 40307 system or even any of the closer stellar systems - humans can't even be bothered to revisit the Moon which, at only 240 thousand miles away, is right on their doorstep!
The Singularity
2.5 / 5 (4) Nov 08, 2012
Necessity is the mother of invention. If we had to, we would.
Would you visit a desert that has no air, no water, no camels, & no dune boarding?. Not to mention dangerous levels of radiation. It's hardly a nice holiday destination is it.
Sonhouse
2.3 / 5 (6) Nov 08, 2012
It sounds to me a system waiting for a shift in planets. Our system has the big guys safely out away from the inner planets. If this system holds true, it looks to me like not a great place to send people with the idea of starting a colony, however long in the future that might be, could that system possibly be stable with so many giants close to its sun?


At 253 trillion miles there's not a snowball's hope in hell of humans ever setting up a colony in the HD 40307 system or even any of the closer stellar systems - humans can't even be bothered to revisit the Moon which, at only 240 thousand miles away, is right on their doorstep!

A lot depends on the human race surviving as an advanced technological civilization. If in the next 200 years the climate change beats us back to horses and plows, we can forget all that speculation of interstellar colonies. For right now, even though the US was the first to put men on the moon, a lot of interest is building up, water there.
GSwift7
2.9 / 5 (13) Nov 08, 2012
A lot depends on the human race surviving as an advanced technological civilization. If in the next 200 years the climate change beats us back to horses and plows, we can forget all that speculation of interstellar colonies


That's hillarious. So, you think climate change represents a threat? Even more, you think climate change is a bigger threat than war, famine, disease, economic collapse, astroid collision, supervolcano eruption, or super tsunami?

Keep in mind that climate change has benefits as well as hazards. As long as we are capable of adapting to the negative, that leaves only positives. Despite the showboating occuring recently over hurricanes and droughts by politicians, NOAA says it's not climate related.

You know, Alice happened at high tide. The previous record storm surge happend at low tide. If they were both at either high or low tide, the old record would still be the record by a couple feet.

As for droughts and heat waves, the old ones are worse too
Thadieus
5 / 5 (2) Nov 08, 2012
Ladies and Gentleman,
This just the beginning of a long journey. We have not even left our front porch.
antialias_physorg
3.9 / 5 (11) Nov 09, 2012
Even more, you think climate change is a bigger threat than war, famine, disease, economic collapse, astroid collision, supervolcano eruption, or super tsunami?

With the exception of a killer asteroid (and with some qualifiers ar supervolcano): yes.
Climate change is a systemic problem. If the entire system goes into a state that does not support life anymore then we're screwed. The others you mentioned bad, but they are only local problems (even all out nuclear war)

Keep in mind that climate change has benefits

Where? Making a few square kilometers arable that were already arable for different plants? That's not a benefit.
GSwift7
2.7 / 5 (12) Nov 09, 2012
Climate change is a systemic problem. If the entire system goes into a state that does not support life anymore then we're screwed.


No, that's not the real climate change theory. That's only what you read in alarmist press releases. None of the serious climate scientists would agree with that statement. The effect just isn't predicted to be that big, and the estimates keep going down, not up.
antialias_physorg
4.1 / 5 (9) Nov 09, 2012
And it's not just arable land. Oceans start becoming acidified and less oxygen rich: which means less maritime life. Given that the oceans are already pretty close to depletion that's a MAJOR food source that could just be virtually gone in a few decades.

once you sturt cutting into these circles of life at any point the ramifications are much wider than a simple "we'll just have a little less of everything". Ecosystems can shift radically if overstretched.
GSwift7
1.9 / 5 (13) Nov 09, 2012
Oh my. Did you hit yourself in the head with somthing?

Since when does an increase in carbon dioxide result in a decrease in ecosystem richness? There's zero reason to think that a slightly more acidic ocean would be a net negative. You do understand that phytoplankton actually thrive on icreased levels of carbon dioxide, right? They are the base of the world's food chain.

Why do you knuckle-heads continue to say such nonsense? You know that nobody outside your alarmist cult believes that junk, right? Go to a party and start talking about that stuff, I dare you. Do it in real life, with real people. You'll see the nodding heads and the rolling eyes, the nervous excuse to be somewhere else, away from the crazy guy.

Wake up dude.

You sound as whacked out as the EU conspiracy nuts when you go off the cliff on climate alarmism. Really, take a deep breath, go read the NOAA web site's FAQ's and then come back to have a reasonable converstion about it without the foolishness
antialias_physorg
4.6 / 5 (9) Nov 09, 2012
Since when does an increase in carbon dioxide result in a decrease in ecosystem richness?

Since a warming of temperatures decreases oxygen solubility in water.

No, we are nowhere near the dead zones of the Triassic - but we shouldn't be so sure of ourselves that we're not heading that way.
http://phys.org/n...res.html

phytoplankton actually thrive on icreased levels of carbon dioxide

However, we do not eat phytoplankton. We eat the fish that eat phytoplankton. And these fish require oxygen to survive (and also an environment that isn't too acidic)

You sound as whacked out as the EU conspiracy nuts when you go off the cliff on climate alarmism.

Just look at what the experst are saying. No need to believe me.
http://www.bbc.co...10789349
We're facing an observable decline in biodiversity due to warming. And that isn't a good sign

GSwift7
1.7 / 5 (11) Nov 09, 2012
Since a warming of temperatures decreases oxygen solubility in water


same goes for carbon, but that's irrelevant. The main driving factor in ocean gas content and acidity is living organisms. The pH in ocean water changes by a factor of 2 between day and night, in response to the daily cycle of life. Same thing with oxygen, iron, carbon, etc.

Remember all the hand waving and whining about the BP oil spill? Yeah. That was a big surprise, wasn't it? Gee, the ocean didn't suddely die? Remember all the talk about dead zones and oxygen depletion? Didn't happen. Hmmm. Do you feel misled? They lied to you on purpose to get people to donate money and support the cause. It's a sham; a con game; a racket. NOAA tried to tell you the truth, but you believed the scary headlines in stead. Now you're doing it again.

Ignore NOAA if you like, but don't expect anyone to take you seriously.
GSwift7
2 / 5 (12) Nov 09, 2012
However, we do not eat phytoplankton. We eat the fish that eat phytoplankton. And these fish require oxygen to survive (and also an environment that isn't too acidic)


Oh brother. Phytoplankton make the majority of the oxygen. More phytoplankton = more oxygen.

An environment that isn't too acidic? What kind of nonsense is that? Actually, animals do better in water that's slightly acidic, and as I just said, the natural fluctuations are huge on time scales of hours, weeks, seasons, years, decades, etc. Ocean life is extremely adaptable, otherwise there wouldn't be any. Ocean life has thrived durring much more challenging times than anything that might result from human environmental effects.

Besides, you know that ocean acidification is actually only theoretical, right? NOAA just started getting the first data back on ocean pH on large scales. There's no baseline to compare to, so they can't say whether it's actually changed or not.
antialias_physorg
4.2 / 5 (10) Nov 09, 2012
same goes for carbon, but that's irrelevant.

That is offset by a higher CO2 content in the atmosphere which forces more carbon into the water (which is the process by which we get the already observed ocean acidifiaction)

Some forms of plankton do have a calcium structure and it's much harder for it to build up that structure if it's trying to do so in an acidic environment. That could be a danger to some food chains.

The pH in ocean water changes by a factor of 2 between day and night

Which is irrelevant becaue the long term stability of a structure is determined by the average pH value. If that shifts upwards by 0.1 then that means a lot of change overall even with a daily variability . Though please post a link where you get that variation from. A change of 2pH values is a HUGE shift. The sources I can find speak only of a change of 1 (max) in shallow water.
rubberman
4 / 5 (8) Nov 09, 2012
GS7 - I went to the NOAA site. They acknowledge the GHG effect and AGW. Instead of saying AGW/climate change is a bigger threat than the hazards you list, lets look at it this way: It's effect will continue to intensify, the other hazards you list will never go away and will also intensify in times resource depletion. We don't have a 100 year supply of anything that we pull out of the ground. Potable water reserves are shrinking while population is growing, food production is becoming more costly in a world where wage increase doesn't match rate of inflation, AP pointed out the decline in biodiversity (resultant not only from climate change but also from our "other" activities. If we keep doing what we are doing, the world we create will be one of reduced comfort for the masses with the "worst" areas expanding considerably. The rich still won't care but that is besides the point. With the climate, our effect will be felt for thousands of years.
GSwift7
1.9 / 5 (9) Nov 09, 2012
Look, here's one of the most recent and conprehensive studies on ocean pH, from the Scripps Institute (a very pro-conservation organization, so it's not Big Oil talking here):

http://scrippsnew...eID=1234

Here's a shocking quote that should settle this issue for anyone interested in the truth:

Some ecosystems such as coral reefs experience a daily range in pH that exceeds the predicted decrease in pH over the next century. While these data suggest that marine organisms may be more adapted to fluctuations in pH than previously thought much more research is needed


Yeah, that's right. Until December of last year, they didn't even know the natural range of variation. They had to invent a sensor to do the study becaue there wasn't one made yet. And, guess what; ocean life is more adaptable than they assumed. Big freaking surprise.
antialias_physorg
4.6 / 5 (9) Nov 09, 2012
You might want to look up 'coral bleaching' and the recent mass bleaching events.

The adaptability of life isn't naively linear. There are tipping points when chemical processes shift suddenly and stresses become to great to bear (the most obvious - and most dramatic one - is when the denaturation conditions of proteins are reached)

The mantra of "we adapted to the last 0.1pH/degree/ppmCO2 increase means we'll have no trouble to adapt to the next 0.1 also...ad infinitum" is just plain stupid.
GSwift7
1.9 / 5 (9) Nov 09, 2012
Potable water reserves are shrinking while population is growing, food production is becoming more costly in a world where wage increase doesn't match rate of inflation, AP pointed out the decline in biodiversity (resultant not only from climate change but also from our "other" activities. If we keep doing what we are doing, the world we create will be one of reduced comfort for the masses with the "worst" areas expanding considerably. The rich still won't care


Now THAT's a reasonable point of view. I totally agree with those statements, and I agree that those are huge (and growing) problems. Those aren't climate change or ocean acidification though.

I'm not too worried about species diversity, but that's a debatable issue, and I'm willing to admit that I could be wrong on this one, but here's my take on it: Nature is amazingly resilient. Nature finds a way to use every available niche. Every available spot where there's a food source has multiple organisms competing. cont
GSwift7
2 / 5 (12) Nov 09, 2012
continued.

If one species succeeds, it's at the expense of something else. When one fails, it's a benefit to something else. The weakest organisms fail and the stronger ones replace them. If you have an ecosystem that can support 1000 rodents, it doesn't matter whether they are field mice, squirels, or rats. If there are 330 of each at first and then all the mice die, then you'll end up with 500 squirels and 500 rats in stead. Nature fills the niches.

You might want to look up 'coral bleaching' and the recent mass bleaching events


OMG. If coral was that fragile there wouldn't be any. Corals have survived extremes of ocean temp and acidity for millions of years, including countless sudden changes. Some of those species are still around in their original form. Go to Kansas and look at the coral fossils in the road cut-aways. You can see many types that still live today.
Ventilator
3 / 5 (7) Nov 09, 2012
Earth is a space craft with a built-in life support system for the life on it. Our biosphere is not independent from our atmosphere and hydrosphere. Environmental impact from human use of carbon-releasing fuels is adding to the naturally occurring changes of our entire ecosystem, driving us towards the same issue that hit the Apollo 13 crew when they had to adjust to a similar issue: loss of life due to improperly managed resource consumption.

This is literally an issue of taking on a swimming pool for the first time. Too much chlorine and one cannot safely swim in it. Too little chlorine and it's not safe due to what's growing in it.

Life is about the balances; only so many naturally occurring points of stability can be altered before the house of cards falls down, and it will do so harder than we seem to expect.
baudrunner
1 / 5 (5) Nov 10, 2012
I can't accept the "Goldilocks zone" theory, where it is necessary to occupy this discreet zone for a planet to be able to sustain life. I mean, look at Nibiru. Its 3,600 year cycle around around our sun - and possibly one of our neighbors too, perhaps the Centauri system - takes it well out of the so-called "habitable" area. It is warmed primarily by heat emanating from its internal structure, and which is trapped by the greenhouse effect of its atmosphere, to which its volcanic activity contributes. It is a very dynamic world, rife with intelligent life which has extraordinary longevity. It occupies our "safe" zone only periodically, and then only for a relatively short duration.
baudrunner
1 / 5 (5) Nov 10, 2012
By the way, don't be skeptical. If you're lucky, you can see Nibiru, even by day, since it is relatively close now. It was at its nearest in the southern hemisphere, and has been seen as it crossed into the northern hemisphere field of view. There have been quite a view videos taken of it in the daytime sky.

It's possible that the top-secret X37-B mission was an investigative one of Nibiru, although why on Earth they want to keep it secret I have no idea. All this hush-hush stuff is annoying. We all want to know.
Czcibor
3.8 / 5 (5) Nov 11, 2012
7 Earth masses? That means (assuming roughly Earth composition) roughly 1.9 g. Presumably there should be some kind of one super ocean, which would mean lower density, increase radius and effectively slightly lower gravity at its surface. Rather inhospitable (but NOT directly lethal) conditions for homo sapiens. But should be acceptable for short and muscular transhumans.
Czcibor
2.3 / 5 (3) Nov 11, 2012
The adaptability of life isn't naively linear. There are tipping points when chemical processes shift suddenly and stresses become to great to bear (the most obvious - and most dramatic one - is when the denaturation conditions of proteins are reached)

The mantra of "we adapted to the last 0.1pH/degree/ppmCO2 increase means we'll have no trouble to adapt to the next 0.1 also...ad infinitum" is just plain stupid.


Aren't you fighting a straw man here? With claiming that your opponent assumes that mechanism works up to infinity?
Czcibor
1 / 5 (2) Nov 11, 2012
No, we are nowhere near the dead zones of the Triassic - but we shouldn't be so sure of ourselves that we're not heading that way.
http://phys.org/n...res.html
Let's assume purely for argument sake that's a scenario that we're going to have in a few centuries. Would that bring down a technological civilization? (Yes, I know, we would have to add ourselves on a list next to other culprit of mass extinctions on planetary scale) But I merely ask about the end of first world countries. Would that really cause a collapse of civilization or merely cause serious damage to agriculture which is responsible in developed countries for a few percent of GDP and force us move our fields of GMO crops to Canada/Scandinavia/ North Siberia/ Greenland /Antarctica?
Torbjorn_Larsson_OM
5 / 5 (2) Nov 11, 2012
@ Sonhouse: Stability is checked in the paper.

From two methods they can say: "– there exists a substantial number of dynamically stable orbits allowed by the data." Specifically a likely resonance between e & f predicts the seen small eccentricities (except for g, the outer habitable). Such things help.

They want more measurements to verify the constraints. (Specifically, masses above the likely ranges blows the system up.)

Since all systems with two or more planets are inherently chaotic, all systems are "waiting for a shift in planets." In our case, the giants have been (J-S resonance in the Nice model) and continue to be (Jupiter destabilizing Mars) the largest problem.

@ baudrunner:

No data, so no Nibiru. This is a science blog, let us keep away from the anti-science.
Torbjorn_Larsson_OM
4 / 5 (4) Nov 11, 2012
Speaking of anti-science and other moral problems:

@ GSwift7: You are trying to deny verified consequences: it takes some time to include or exclude individual extremes. But in general the hot extremes are an increasing envelope as AGW is increasing temperature, quite naturally. And they already kill & cost more than if we had fixed the problem earlier, we know that too. (Google!)

Continued AGW will mean mass extinction. On what horizon do you mean adapt? It takes ~ 1 million year for diversity to recover, and now we know its level is randomly set after. (Google, recent paper.) So it doesn't have to be improvement after, despite naive "hot planet, more bioproductivity" ideas.

Czibor:

Meanwhile, moral problem: AGW _kills_, we know that happens as we speak! No one can seriously propose the regime as recommended for any society.
ShotmanMaslo
1 / 5 (3) Nov 11, 2012
Climate change will hardly endanger humanity. A worst case scenario will cost us millions of lives, trillions of dollars and a substantial loss of biodiversity. Thats really bad, but not something that modern civilisation cannot cope with quite easily.
antialias_physorg
1 / 5 (1) Nov 12, 2012
and a substantial loss of biodiversity.

That really depends on where that loss occurs. If we substantially reduce entire section of the food chain (e.g. phytoplankton or plant pollinators like bees) then we kill off our food sources.

And that is NOT something modern civilization can cope with.
alfie_null
5 / 5 (1) Nov 12, 2012
Climate change will hardly endanger humanity. ...

Perhaps what you meant to say was "I can't imagine that climate change will endanger humanity ..."
GSwift7
1 / 5 (4) Nov 13, 2012
to Torbjorn:

You are trying to deny verified consequences: it takes some time to include or exclude individual extremes. But in general the hot extremes are an increasing envelope as AGW is increasing temperature, quite naturally


Are you claiming that extremes have become more severe or more frequent? The historical and paleo records do not support that claim. According to NOAA and USGS the recent rise in reported incidents is a product of better monitoring/global coverage. Increased damage is a product of urbanization of coastline, not climate change.

As for adaptation taking millions of years, that's true, and it's already happened. According to Scripps, the coral are already adapted to handle more extremes than we predict from global warming. You see, the corals would already be extinct if they couldn't survive past conditions far exceeding modern GW predictions.
ShotmanMaslo
1 / 5 (1) Nov 14, 2012


And that is NOT something modern civilization can cope with.


Yes, it likely can. Substantial loss of phytoplancton or pollinators will lead to famines, but we are not dependent on them as a civilisation.
antialias_physorg
3 / 5 (2) Nov 14, 2012
Presumably there should be some kind of one super ocean, which would mean lower density,

Oceans (on Earth) have an average depth of 3-4km . Our planet is 13000km in diameter. A 'superocean' - even with an unrealistically large average depth of 100km - will do diddly-squat in changing the overall average density/gravity.

Larger gravity with the same material percentages as Earth will mean a higher density (as gravity and pressures within the planetary mass are higher). Which means smaller radius. Under those conditions the surface gravity will be higher than a straightforward volumetric comparison would indicate.
jibbles
1.5 / 5 (2) Nov 18, 2012
we are punctuating the equilibrium of earth's biosphere. life does not thrive in instability.

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