Showing all posts about red dwarf

A planet might orbit Alpha Centauri A: send Chrysalis there instead

21 August 2025

The planet’s existence — orbiting Alpha Centauri A, part of the nearest stellar system to the Sun — has not yet been confirmed. If there though, the body would be situated within Alpha Centauri A’s (AKA Rigil Kentaurus) habitable zone, a star similar to our Sun.

That could be a more “Earth-like” planet, certainly more so than any planets orbiting the third member of the Alpha Centauri trinary: red dwarf star Proxima Centauri.

If anyone is serious about sending a sixty-kilometre long, multi-generational spaceship, named Chrysalis, on a four-hundred year, one-way, journey to Alpha Centauri, then the would-be planet hosted by Alpha Centauri A would be a more sensible destination.

Once, that is, the planet is confirmed to exist, in-fact resides in Alpha Centauri A’s habitable zone, and is truly “Earth-like”, not just some rock with a slight atmosphere, and a bit of liquid water.

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A four-hundred year, one way, trip to Proxima Centauri? Is this sci-fi?

13 August 2025

A proposal to build a multi-generational spaceship — named Chrysalis — that’s nearly sixty-kilometres in length, and would spend four-hundred years travelling to the star presently closest to the Sun, Proxima Centuri, recently won first prize in the Project Hyperion Design Competition.

The vessel, which would be fitted out with tropical forests, schools, workplaces, libraries, and manufacturing facilities, among other things, could house over two-thousand people. Obviously some travellers on Chrysalis, would live their entire lives only on the gigantic ship.

So far, so good. Aside from the ethical matter of consigning your descendants to a life lived on a sixty-kilometre long tin-can, whether they like it or not. But the proposal becomes a little murkier when we learn the vessel’s precise destination:

Chrysalis is designed to house several generations of people until it enters the star system, where it could shuttle them to the surface of the planet Proxima Centuri b — an Earth-size exoplanet that is thought to be potentially habitable.

Proxima Centuri b is thought to be habitable? So to recap: someone wants to spend untold trillions of dollars building a massive spaceship, that will carry some two-thousand people, on a four-hundred year long, one way voyage, to a planet thought to be habitable?

Am I the only one who sees a problem with this?

Wouldn’t we first want to be one-hundred percent certain the planet in question, Proxima Centuri b, was in fact habitable, in Earth-analog fashion, before even drawing up blueprints for the vessel? Apparently not. Chrysalis‘ designers appear to be so confident Proxima Centuri b is fit for human habitation, they’re laying on shuttles to get people on the ground.

Doubtless passengers are relieved they’re not required to parachute to the surface.

Proxima Centuri b was discovered in 2016. The body is a super-Earth, meaning it is larger than our home planet, but still smaller than the likes of Uranus or Neptune. In addition, the planet is located in what is considered to be Proxima Centuri’s habitable zone. Planets within a star’s habitable, or Goldilocks zone, as Earth is in the Sun’s, are generally deemed to be conducive to life. Temperatures are neither too hot, nor too cold, and water can exist in liquid form.

But talk of Goldilocks zones usually applies more to G-type main-sequence stars, or yellow dwarfs, such as the Sun. Proxima Centuri is a red dwarf star, a rather different kettle of fish. I’m not even sure the term habitable zone should be uttered in the same sentence as red dwarfs.

I’ve written about these stars before. They fascinate me. As mentioned, one is the star nearest to us. They also live for trillions of years (compared to billions for many other stars, including the Sun). Red dwarfs will probably be the last stars shining in the universe.

But, as I’ve said previously, they’re not all that life-friendly, particularly for human life. As I’ve written this before, I’ll be succinct. Planets in the supposed habitable zones of red dwarfs, would be — on account of their relative closeness to the star — tidally locked. One side of the planet forever faces the star, and bakes, while the other, cloaked in perpetual darkness, freezes. Most hospitable.

Red dwarfs also emit powerful flares. The outlook would not be good for the inhabitants of a planet in the path of one of these stellar outbursts. Proxima Centuri b may be possessed of some sort of atmosphere, and water might be present, but the planet is no Earth.

What if, on reaching the distant planet, those aboard Chrysalis find it to be completely uninhabitable? Would they be able to return to Earth? No, because the journey is one way. Passengers would be on a multi-century trip to their deaths.

Of course, the Chrysalis project is hypothetical, but that doesn’t mean there isn’t merit in the idea. If the vessel is ever to be constructed, a more suitable destination planet, not just one thought to be habitable, needs to be chosen.

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If there is life on K2-18b the K2-18 red dwarf star will kill it off

25 April 2025

News that traces of chemicals possibly indicating the presence of life on a planet, known as K2-18b, some one-hundred-and-twenty-four light years from Earth, resulted in a flurry of headlines the other week. Scientists find strongest evidence yet of life on an alien planet. Scientists claim they’ve discovered most promising ‘hints’ of potential for life on distant planet. And: Scientists Find Promising Indication of Extraterrestrial Life — 124 Light-Years Away.

Sure, it’s exciting. This is news many of us have been waiting for. Even if it’s not quite the definitive announcement we would have preferred. The problem though is the media outlets writing about the discovery of chemical “fingerprints” in the atmosphere of K2-18b, have not looked at the whole story. In fact, it seems they’ve only looked at the first few words. After all, why allow the full facts of the matter to get in the way of a click-bait worthy headline? The biggest — literally — part of the story is K2-18, the star the would-be life-hosting planet K2-18b is orbiting.

I’ve written about this before, but let’s revisit the subject, since it’s topical.

K2-18 is a red dwarf star. Red dwarfs — as the name suggests — are small. Some might only be a little bigger than Jupiter, the largest planet in the solar system. Red dwarfs are dimmer and cooler compared to a star like the Sun. They however have long lifespans, typically measured in trillions of years, rather than billions, as is the case for many other stars in the universe. At first glance, red dwarfs seem like ideal stars to host planets that might give rise to life. Their longevity gives lifeforms an eon to take hold and develop. But red dwarfs are not really life-friendly stars.

One problem lies in their size. Being so small, the habitable, or Goldilocks zone, the area of their solar system best suited for the fostering of life, that is neither too hot, nor too cool, is quite close to the star. Any planets in the habitable zone will be tidally locked. This means one side of the planet permanently faces the star, while the other is perpetually shrouded in darkness. In other words, the star facing side of a planet will be incredibly warm, while the dark side will be quite cold. Neither extreme may be particularly conducive to life, especially complex lifeforms.

But that’s not the worst of it. Red dwarfs also emit powerful flares that can render nearby planets lifeless. Some of these outbursts can be even more intense than those generated by the Sun. While one study of these flares found they might emanate from the polar regions of red dwarfs, rather than their equators, being the plane planets usually orbit a star along, the odds remain stacked against life here. None of this information is new, but has just about been completely overlooked in the recent news stories, about the possibility of life on K2-18b.

Here may be an unfortunate instance of a star that brings life into being, only to take it away later.

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Potentially habitable Earth size planet forty light years away

4 July 2024

That’s the good news. Tory Shepherd, writing for The Guardian, says the recently discovered exoplanet, dubbed Gliese 12b, might be able to host liquid water. We all know what that means. If there’s water, there may be life. Gliese 12b is so named because it orbits a star called Gliese. Now for the bad news. Gliese is a red dwarf.

I personally don’t have a problem with red dwarf, or M-type, stars. They’re actually kind of cool. And common. Up to seventy-five percent of stars in the cosmos are thought to be red dwarfs. The star nearest to Earth, Proxima Centauri, is a red dwarf. And while most stars in the universe have relatively short lifespans — for instance the Sun, which is about half way through its ten billion year life — red dwarfs live for trillions of years.

The last stars — as we currently understand them, at least — shining in the universe, will be red dwarfs. Go the red dwarfs. But, the problem is any planets orbiting in a red dwarf’s habitable-zone, will be tidally locked. That is, only one side of the planet will face its host star. That half of the planet therefore, in this case Gliese 12b, will be overly warm, while the other, dark side, will be rather cold.

This may not be particularly conducive to life. But some scientists have suggested life on planets orbiting red dwarfs in the habitable-zone, may take hold near the day-night terminator. This is where it will be neither too hot, nor too cold. But this would be an extremely narrow corridor, somewhat limiting the chances of life, especially intelligent life, developing.

Then there’s the red dwarfs themselves. They’re prone to regularly emitting intense radiation flares, which could have the effect of sterilising the surface of nearby planets. This points to the likelihood of Gliese 12b not being all that habitable at all. I think we need to reserve our excitement for the discovery of habitable Earth size planets, for maybe when they’re found orbiting other types of stars.

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NASA finds seven earth size planets, but are they anything like Earth?

24 February 2017

After days of keeping us in suspense about a new discovery, NASA let the cat out of the bag, in the early hours of yesterday morning. The TRAPPIST optic robotic telescope, located in Chile, recently identified a dwarf star, about forty light years distant from Earth, that is host to seven planets around about the same size as Earth.

Come on now, you didn’t think NASA was going to announce that an alien civilisation had been found, did you? This is still a significant discovery though.

Particularly as three of the seven bodies orbiting TRAPPIST-1 — the star also takes its name from the Belgian operated telescope — are within its star system’s so-called Goldilocks, or habitable zone. This is an area around a star capable of supporting life, that is neither too hot, nor too cold.

It is this bit that is especially of interest, as it means these planets may harbour water in liquid form, and, as a result, potentially life of some sort. And that is obviously an exciting prospect. But talk that we may one day be able to emigrate there is well wide of the mark, to say the least.

There’s a big difference between a planet that is earth-like, and one exactly like Earth. Such bodies are called an Earth twin, or Earth analog. For example, Proxima b, an exoplanet within the habitable zone around Proxima Centauri, the nearest star to the Sun, is considered to be earth-like, as it is a rocky, or terrestrial planet.

It might have some sort of atmosphere, and possibly there could be liquid water on its surface. But Proxima b may be far from habitable, at least as far as humans are concerned. As Proxima Centauri is a red dwarf star, which are relatively cool, Proxima b would need to be quite close to the star, to be within the habitable zone.

With that sort of proximity however, Proxima b would be tidally locked, meaning the planet’s rotational period matches the time it takes to orbit the star. The result here is only one side of the planet would ever face the star.

Therefore, the day side of Proxima b would be quite warm, whereas the night side would be extremely cold. The only spots that might be conducive to life, would be near the day-night terminator. Red dwarf stars themselves pose problems for any planets they host. For instance, they are prone to emitting powerful flares, which may have the effect of sterilising nearby planets.

Not so earth-like, after all. So while some form of life may manage to eke out an existence there, the environment would hardly be suitable for human occupation. The same conditions could well apply to the planets within the Goldilocks zone of TRAPPIST-1, given it too is a relatively cool dwarf star.

I think we might be waiting a long time indeed for news that a planet as habitable as Earth is found. In the meantime we should give thought to taking greater care of our own Earth. Clearly we’re not going to be rocketing off anywhere else in any hurry.

Originally published Friday 24 February 2017, with subsequent revisions, updates to lapsed URLs, etc.

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