Every red dwarf star has at least one planet

Mar 04, 2014
Artist's impression. Credit: Neil Cook, University of Hertfordshire

Three new planets classified as habitable-zone super-Earths are amongst eight new planets discovered orbiting nearby red dwarf stars by an international team of astronomers from the UK and Chile.

The study identifies that virtually all red dwarfs, which make up at least three quarters of the in the Universe, have planets orbiting them. 

The research also suggests that habitable-zone super-Earth planets (where liquid water could exist and making them possible candidates to support life) orbit around at least a quarter of the red dwarfs in the Sun's own neighbourhood.

These new results have been obtained from analysing data from two high-precision planet surveys – the HARPS (High Accuracy Radial Velocity Planet Searcher) and UVES (Ultraviolet and Visual Echelle Spectrograph) – both operated by the European Southern Observatory in Chile. By combining the data, the team was able to detect signals that were not strong enough to be seen clearly in the data from either instrument alone.

Dr Mikko Tuomi, from the University of Hertfordshire's Centre for Astrophysics Research and lead author of the study, said: "We were looking at the data from UVES alone, and noticed some variability that could not be explained by random noise. By combining those with data from HARPS, we managed to spot this spectacular haul of ."

"We are clearly probing a highly abundant population of low-mass planets, and can readily expect to find many more in the near future – even around the very closest stars to the Sun."

To find evidence for the existence of these planets, the astronomers measured how much a star "wobbles" in space as it is affected by a planet's gravity. As an unseen planet orbits a distant star, the gravitational pull causes the star to move back and forth in space. This periodic wobble is detected in the star's light

The team used novel analysis techniques in squeezing the planetary signals out of the data. In particular, they applied the Bayes' rule of conditional probabilities that enables answering the question "What is the probability that a given star has planets orbiting it based on the available data?" This approach, together with a technique enabling the researchers to filter out excess noise in the measurements, made the detections possible.

Professor Hugh Jones, also from the University of Hertfordshire, commented: "This result is somewhat expected in the sense that studies of distant with the Kepler mission indicate a significant population of small radius . So it is pleasing to be able to confirm this result with a sample of stars that are among the brightest in their class."

The have been discovered around stars between 15 and 80 light years away and they have orbital periods between two weeks and nine years. This means they orbit their stars at distances ranging from about 0.05 to 4 times the Earth-Sun distance - 149 million kilometres (93 million miles).

These discoveries add eight new exoplanets signals to the previous total of 17 already known around such low-mass dwarfs. The paper also presents ten weaker signals for which further follow-up is necessary.

The paper will be published in Monthly Notices of the Royal Astronomical Society.

Explore further: First planet found around solar twin in star cluster

More information: Tuomi, M., Jones, H. R. A., Barnes, J. R., Anglada-Escude, G., and Jenkins, J. S. 2014. "Bayesian search for low-mass planets around nearby M dwarfs. Estimates for occurrence rate based on global detectability statistics", MNRAS, in press.

add to favorites email to friend print save as pdf

Related Stories

First planet found around solar twin in star cluster

Jan 15, 2014

Astronomers have used ESO's HARPS planet hunter in Chile, along with other telescopes around the world, to discover three planets orbiting stars in the cluster Messier 67. Although more than one thousand ...

Three planets in habitable zone of nearby star (w/ video)

Jun 25, 2013

(Phys.org) —A team of astronomers has combined new observations of Gliese 667C with existing data from HARPS at ESO's 3.6-metre telescope in Chile, to reveal a system with at least six planets. A record-breaking ...

NASA cries planetary 'bonanza' with 715 new worlds

Feb 26, 2014

NASA on Wednesday announced a torrent of new planet discoveries, hailing a "bonanza" of 715 worlds now known outside the solar system thanks to the Kepler space telescope's planet-hunting mission.

How common are earths around small stars?

Jun 03, 2013

(Phys.org) —The Kepler mission has revolutionized the study of exoplanet statistics by increasing the number of known extrasolar planets and planet candidates by a factor of five, and by discovering systems ...

Recommended for you

Lives and deaths of sibling stars

9 hours ago

This beautiful star cluster, NGC 3293, is found 8000 light-years from Earth in the constellation of Carina (The Keel). This cluster was first spotted by the French astronomer Nicolas-Louis de Lacaille in ...

Fermi finds a 'transformer' pulsar

Jul 22, 2014

(Phys.org) —In late June 2013, an exceptional binary containing a rapidly spinning neutron star underwent a dramatic change in behavior never before observed. The pulsar's radio beacon vanished, while at ...

User comments : 28

Adjust slider to filter visible comments by rank

Display comments: newest first

GSwift7
4.9 / 5 (9) Mar 04, 2014
Wow, that's really cool.

They figured out a new method that enables new discoveries with existing data, which is awesome.

Also, discovery of a significant number of planets around nearby stars will be essential in the next decade of exoplanet research. These nearby exoplanets will be our best chance to get details like surface, atmosphere, etc. If we can find and characterize enough of these nearby planets, we might be able to identify patterns to infer what planets farther away might be like. It's not a very concrete way to do it, but it's a start.

It may not matter much right now, but eventually, the types of exoplanets and exomoons around our nearest neighbors will have a huge impact on the types of missions we might want to try. If there's no sign of a place that might be livable (habitable would be good, but survivable at the very least) within <10 LY, that would seriously limit us. OTOH, if there's a temperate terrestrial planet or moon, we're gonna want to send a probe ASAP.
richardwenzel987
4.9 / 5 (12) Mar 04, 2014
If I'm not mistaken, red dwarfs have a rather broad habitable zone. On the other hand, planets in that habitable zone are likely to be tidally locked or perhaps in a resonant relationship, with very long nights. Also, red dwarfs have a difficult radiation environment due to flare events. Not sure what all that means in terms of life forms. They might be good targets for SETI efforts.

Humor here: note that flying saucer et descriptions frequently give aliens BIG EYES! Just what you might expect if they come from red dwarf planetary systems!
Maggnus
5 / 5 (7) Mar 04, 2014
If I'm not mistaken, red dwarfs have a rather broad habitable zone.
I could also be mistaken, but I think its the other way around. Worse, going from my oft fuzzy memory, I seem to recall the habitable zone is so close to the star that any planets in it would likely be tidally locked. (erm tooseeked lol!)

Humor here: note that flying saucer et descriptions frequently give aliens BIG EYES! Just what you might expect if they come from red dwarf planetary systems!


:D


Q-Star
5 / 5 (7) Mar 04, 2014
If I'm not mistaken, red dwarfs have a rather broad habitable zone.
I could also be mistaken, but I think its the other way around. Worse, going from my oft fuzzy memory, I seem to recall the habitable zone is so close to the star that any planets in it would likely be tidally locked. (erm tooseeked lol!)


Correct, narrow habitable zone AND tidally locked. But as far a possible "life supporting zone", the other poster was also correct, the extreme (random but common), radiation events that are a hallmark of red dwarfs would make it just about impossible for any life form we could imagine to arise on one.
Rimino
Mar 04, 2014
This comment has been removed by a moderator.
Modernmystic
4.2 / 5 (5) Mar 04, 2014
Red dwarf stars have all kinds of issues with habitability and generally being inimical to life. High variability, tidal lock within the habitable zone and IIRC low metalicity. Not to mention the spectrum of light they give off is not conducive for us for colonization, nor aliens for evolution (low incidence of mutation). We might find some simple life or some extremophiles, but I doubt we'll be finding our cosmological kin around an M class star.
MandoZink
5 / 5 (3) Mar 04, 2014
"Habitable" is such a broad term, based on loosely defined assumptions and optimistic uncertainties. I look forward to a day when we we have a wide array of "habitable" nomenclatures defined which we base on various, better understood criteria for supporting life, be it the emergence of self-replicating organisms or just a place we might safely visit.

No disappointment about that now, however. We will progress. All optimism and awe here. It's been the nature of scientific advancement that something we might never have conceived of will surprise the hell out of us.

GSwift7
5 / 5 (7) Mar 04, 2014
the extreme (random but common), radiation events that are a hallmark of red dwarfs would make it just about impossible for any life form


Might a deep ocean and a thick atmosphere provide enough protection? That might also distribute heat well enough so that tidal lock isn't a non-starter.

A sufficiently eliptical orbit might help also. Tidal heating could expand the habitable zone and thereby avoid tidal lock. We really don't know how common highly eliptical orbits are yet.

We really don't have constraints on what is possible yet, so who knows?
Q-Star
5 / 5 (6) Mar 04, 2014
the extreme (random but common), radiation events that are a hallmark of red dwarfs would make it just about impossible for any life form


Might a deep ocean and a thick atmosphere provide enough protection? That might also distribute heat well enough so that tidal lock isn't a non-starter.

A sufficiently eliptical orbit might help also. Tidal heating could expand the habitable zone and thereby avoid tidal lock. We really don't know how common highly eliptical orbits are yet.

We really don't have constraints on what is possible yet, so who knows?


I suppose it's possible, but only barely so. The real worth of these studies, for me anyway, is in the addition of data to the overall body of information on planetary formation. I wish they would leave the "life bearing" aspect out of it and focus on the physics of planetary system formation. But that's just my personal opinion and not one I would promote as being any better than any other person's preferred focus.
GSwift7
5 / 5 (6) Mar 04, 2014
I wish they would leave the "life bearing" aspect out of it and focus on the physics of planetary system formation


I agree that habitability, or at least survivability, is super speculative, but it's difficult to restrain the imagination. In a sense it's wasteful and distracting, but isn't it the sheer wonder of the unknown that drives us in the first place?

Just a few years ago there were few professionals who would have dared to hope that planets are so pervasive. I struggle to avoid imagining that potentially habitable planets may be similarly abundant.

But, yes, I grudgingly agree with you. We know so little about the conditions that might make planets habitable right now. Realistically, we need to collect data on specific cases and evaluate them as we can. JWST, if it works, should allow us to really narrow down the characteristics on these nearby planets around small stars. I'm looking forward to it.
Maggnus
5 / 5 (3) Mar 04, 2014
I'm looking forward to it.
Me too! Especially if red dwarf planets are as common as this article is suggesting they may be, and considering how close some of those types of stars are to us, I can imagine a mission to one of them in my lifetime.

Yes yes, optimistic in the extreme, but how cool would that be?
GSwift7
5 / 5 (4) Mar 04, 2014
I can imagine a mission to one of them in my lifetime.

Yes yes, optimistic in the extreme, but how cool would that be?


We could launch a probe in our lifetimes, but getting results back in less than a current human lifetime is doubtful. Maybe if it became a big enough priority that you could get a blank check for funding, but otherwise there's a lot of work we need to do first. There are two key technical challenges that come to mind for me. The first is simply building a machine that can keep running for the amount of time needed (decades of high mechanical stress). The second is thermal efficiency. In order to get to any nearby star in a reasonable amount of time, you would need a very high constant acceleration, which means an engine with loads of power. Unless that engine is extremely efficient, you cannot radiate off the waste heat fast enough. If there's a solution to those two problems, which is a big if, it's not gonna be cheap to figure out.
Maggnus
5 / 5 (3) Mar 04, 2014
Sure, rain all over my parade! :)

You're right of course, and the idea of sending a small probe that far seems wasteful (Look what I did Ma!) There are some interesting propulsion concepts that might see fruition in that period, and with a constant acceleration its just barely possible we could get it up to a percent of the speed of light (seems to me I read somewhere that 8% is achievable with today's technology, but that might be my enthusiasm talking). With a bit of luck (well ok, a lot) and some new age-reducing drugs I might be around to hear its arrival.
MandoZink
5 / 5 (5) Mar 04, 2014
I cannot recall the source, but in the last month I watched a video of a just recently modeled analysis of the atmosphere on a tidal-locked planet in the "habitable zone" of a red dwarf. It found that the temperature difference between star-facing and opposite sides would not be as great as thought due to the persistent circulation pattern that the model determined. Warm air would constantly flow to the dark side, then rise up and continue a flow of cold upper air that would transit at a higher altitudes to the warmer side where it would descend.

They also speculated on the type of life that wold have to evolve and exist in such conditions, Needless to say, it would be windy. I do not recall whether radiation was discussed, but the video was very interesting. I should have bookmarked it.
EnricM
4 / 5 (2) Mar 05, 2014
If there's no sign of a place that might be livable (habitable would be good, but survivable at the very least) within <10 LY, that would seriously limit us. OTOH, if there's a temperate terrestrial planet or moon, we're gonna want to send a probe ASAP[/b]

Why is it important that a planet is habitable? And why would it "limit us" ?
We can send a probe no matter how the planet is... and I don't think that anybody will seriously think on colonising habitable exoplanets, specially those were there already might be live.

IF there is a colonisation effort it would be safer and easier to aim at Mars like planets, asteroids and low-g sterile moons.
Birger
not rated yet Mar 05, 2014
If red dwarf stars generally have low amounts of heavy elements, the small-radius planets observed may have a diffe rent ratio of elements than terreestrial planets of the solar system.
I am particularly concerned about the planets have very thick atmospheres of hydrogen and helium. The planet formation process in a low-metallicity protoplanetary disc could be significantly different from the one that took place in the early solar system.
antialias_physorg
4.5 / 5 (2) Mar 05, 2014
If there's no sign of a place that might be livable (habitable would be good, but survivable at the very least) within <10 LY, that would seriously limit us.

That distance limits it to 8 star systems (4 of which are binaries). Only the Alpha Centauri binary system has a confirmed planet which is far too near its parent star.

It may not matter much right now, but eventually, the types of exoplanets and exomoons around our nearest neighbors will have a huge impact on the types of missions we might want to try

Not really. At those distances you can chart a curve of estimated progress in attainable probe speeds (drive technology) vs. flight times. Using that graph we'll probably wait another few hundred years before we launch a probe to get an earliest arrival/return time. No rush.
antialias_physorg
5 / 5 (2) Mar 05, 2014
Correct, narrow habitable zone AND tidally locked. But as far a possible "life supporting zone", the other poster was also correct, the extreme (random but common), radiation events that are a hallmark of red dwarfs would make it just about impossible for any life form we could imagine to arise on one.


I'm really not so sure. We've detected life kilometers underground on Earth. At great depth it really doesn't matter what color the parent star is (or how close it is. Or if there is one at all!) - the predominant form of energy down there is from radioactice decay of the planet's own material and the remainder of the heat trapped during formation.
So I'm not really sure what this hype about 'habitable zones' is all about. If a planet (presumably) has water in some form and it is large enough to have to still have a heated interior then life (as we know it) can at least subsist. And where life can subsist, life (presumably) may also originate.
GSwift7
5 / 5 (2) Mar 05, 2014
to EnricM:

Good points to talk about there. Opinions will vary on this, so no problem if you don't agree with me. It's all hypothetical anyway.

I am thinking that it will be difficult to get funding for an interstellar mission of any kind unless we detect a planet that might be a place where people could survive. If the only kind of planets around our nearest stars are no different than the planets and moons here, then there's not much reason to go explore them in the near future. It would almost surely delay exploration outside our solar system.

As for life on a nearby exoplanet, that's a whole different ballgame. My previous comments are based on the assumption that there isn't any sign of life. As long as there's a planet where we might find liquid water on the surface, even if the atmosphere is CO2 and SO2, it would be survivable for a colony.

I think enough people would be willing to fund a robot probe if we thought there might be liquid water somewhere nearby.
GSwift7
5 / 5 (2) Mar 05, 2014
few hundred years before we launch a probe to get an earliest arrival/return time. No rush


Based on the present knowledge of nearby stars, yes. I think that if we find a place that might be capable of having liquid surface water, people's opinions would change, and it might accelerate the timetable, perhaps to less than 100 years (for launch). Even if a future probe could pass it along the way, it would be good to get one going (plan for some failures, right?)

As I said in my previous post, this is just opinion and it's all hypothetical, so purely crystal ball stuff for now, but still fun to talk about.

Based on our limited choice of nearby stars, it's not looking very likely that we'll find liquid water, but who knows. We appear to have found frozen water on both the moon and Mercury, and who would have thought we'd find that 30 years ago?

As for Alpha Centauri, couldn't there still be an earth sized planet that we can't see?
antialias_physorg
5 / 5 (2) Mar 05, 2014
I think that if we find a place that might be capable of having liquid surface water, people's opinions would change

I don't think it depends on people's opinion. Consider that currently we have probes that go extrasolar at 17km/s (Voyager 1) - which means, if it was pointed at Proxima Centauri (which it isn't) it'd need 70k years to get there. If we wait ten thousand years to work on probes that will go just 10 times as fast they'll get there 53k years earlier.

Even if a future probe could pass it along the way, it would be good to get one going (plan for some failures, right?)

Considering that your contingency plan is still 50k years out. Nah.

Besides: We really don't know how to build tech that will stay operable under the fierce radiation conditions in outer space for any kind of timeframe needed for such a venture. That needs something that can constantly self-monitor and self-repair at the atomic level.
GSwift7
5 / 5 (3) Mar 05, 2014
I don't think it depends on people's opinion ... If we wait ten thousand years to work on probes that will go just 10 times as fast they'll get there 53k years earlier


Yeah, I know it's a stretch. It would cost a lot of money, but I honestly think we could have a reasonbly fast spacecraft in less than 100 years. You would need to convince the public to spend some major money on it though. That's why I was suggesting that perhaps identifying a planet with liquid water would be enough to motivate people into funding something on the scale of Apolo or the Manhattan Project.

It probably doesn't matter anyway. As you pointed out, there aren't very many stars nearby, and unless there's something compelling to go take a look at, there's no motivation to make the trip at all.

On the bright side, we will almost surely know if there is an inviting planet in our neighborhood (or not) within our lifetimes. The next generation of telescopes should at least answer that question.
oliverrp
2 / 5 (1) Mar 05, 2014
"The study identifies that virtually all red dwarfs, which make up at least three quarters of the stars in the Universe, have planets orbiting them."

I'm concerned that this study concludes two huge somethings (virtually all red dwarfs have planets and red dwarfs make up at least 75% of all stars), based on a miniscule data sample and ?.

GSwift7
5 / 5 (3) Mar 05, 2014
I'm concerned that this study concludes two huge somethings (virtually all red dwarfs have planets and red dwarfs make up at least 75% of all stars)


The evidence for the percentage of red dwarf size stars is actually fairly solid. I haven't looked at the actual paper, but maybe the title of the news article was being more sensational than it should about the other conclusion? Take a look at the paper, if it's available, and let us know if that's the case? I'd look, but I'm headed out the door in...
Maggnus
5 / 5 (3) Mar 05, 2014
I'm concerned that this study concludes two huge somethings (virtually all red dwarfs have planets and red dwarfs make up at least 75% of all stars), based on a miniscule data sample and ?.
That's an assumption on your part! :)

The number of red stars has been postulated for a long time (see here for eg: https://www.astro...iv.html) Basically, it is a function of how stars are formed.

As for the planets thing - well, as Gswift says, check out the actual paper, maybe they have some pretty good data upon which to make their assumption.
antialias_physorg
4.7 / 5 (3) Mar 05, 2014
Here's a link to the paper on arxiv:

http://arxiv.org/abs/1403.0430

From this it looks like its relatively 'easy' to find planets around dwarf stars (as the stars are less massive and therefore tend to wobble more as the planets revolve around them). Or, conversey, it is easier to find low mass planets as opposed to with high mass stars. If I read it right the probability for such a start to have at least one certain radius-range planet is as high as 90 percent (possibly 95%) heavy-tailed towards the low radius end of the distribution.

If you don't want to slog through the statistical and methodical detail: table 5 and figure 7 are probably the most interesting things to glean.

GSwift7
5 / 5 (2) Mar 06, 2014
If you don't want to slog through the statistical and methodical detail: table 5 and figure 7 are probably the most interesting things to glean


If I'm reading it right, they're not even looking at planets below 3 earth mass.

Based on what I could understand (admittedly limited), the title of this article might not be too far off. It looks like they are extrapolating for the smaller planets?

When you get into other types of stars, like binary and such, this could be a lot different percentage.
philw1776
not rated yet Mar 08, 2014
M stars (red dwarfs) tend to flare a lot when young. The majority stop this nasty behavior after a couple thousand million years, though some don't. So older biospheres might not have the flare problems.
The BB spectrum of M stars is shifted way into the longer wavelengths as you would expect. I recall but not precisely some paper on wavelength of light and photosynthethis that says longer wavelengths than previously thought might support it.
Planets around M stars should be tidally locked EXCEPT possibly in some elliptical orbits or more likely as we have learned from Kepler, closer than in our solar system planetary neighbors could well induce rotational resonances (Mercury). Problem being the huge tidal forces likely sweeping oceanic tides of tens to hundreds of meters across the surface never mind the active volcanic churning (Io).
russell_russell
not rated yet Mar 08, 2014
More humor.
What is the probability that the universe does not harbor life.
Leave out the data point earth.

Prompted by:

"...the Bayes' rule of conditional probabilities that enables answering the question "What is the probability that a given star has planets orbiting it based on the available data?"

Up the ante.
"What is the probability that a given star has celestial bodies orbiting it based on the available data?"