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

Friday, 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 they were 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 solar system’s so-called Goldilocks, or habitable zone, an area 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 habour water in liquid form, and, as a result, potentially life of some sort. And that is obviously an exciting prospect. But talk we may one day be able to emigrate there is well wide the mark, to say the least.

There is, you see, a big difference between a planet that is “earth-like”, and one exactly like Earth. Or a planet that could be 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 be within the habitable zone.

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

Therefore, the sunny 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. In addition, the planet is also exposed to stellar wind pressures far greater than those that Earth experiences.

Not all that earth-like, after all. So while some form of life may manage to eke out an existence there, it 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 to is a relatively cool dwarf star.

At the very least, they’re quite possibly tidally locked. If we’re looking for a new planet to settle on then, it needs to be an Earth twin. This is a planet, as the name suggests, that is identical in almost every way to ours. And if there are at least one hundred billion planets in our galaxy, the Milky Way, then it stands to reason some proportion must be virtually identical to Earth.

But an Earth twin candidate needs to be more than a terrestrial planet, orbiting within the habitable zone of its solar system though. In their book, Rare Earth, published in 2000, US paleontologist Peter D. Ward, and Donald Brownlee, a professor of astronomy, outlined the criteria necessary for a planet to be classified as an Earth twin:

The right distance from a star; habitat for complex life; liquid water near surface; far enough to avoid tidal lock; right mass of star with long enough lifetime and not too much ultraviolet; stable planetary orbits; right planet mass to maintain atmosphere and ocean with a solid molten core and enough heat for plate tectonics; a Jupiter-like neighbor to clear out comets and asteroids; plate tectonics to build up land mass, enhance bio-diversity, and enable a magnetic field; not too much, nor too little ocean; a large moon at the right distance to stabilize tilt; a small Mars-like neighbor as possible source to seed Earth-like planet; maintenance of adequate temperature, composition and pressure for plants and animals; a galaxy with enough heavy elements, not too small, elliptical or irregular; right position the galaxy; few giant impacts like 65 million years ago; enough carbon for life, but not enough for runaway greenhouse effect; evolution of oxygen and photosythesis; and, of course, biological evolution.

That’s an extensive list. Some astronomers think two percent of the Milky Way’s planets may be Earth twins, meaning there could be two billion such bodies. Given the exacting conditions required for their existence though, I think the actual number may be far smaller.

It could a very long time, therefore, before any announcement is made regarding the discovery of a truly earth-like planet, that is, an Earth analog. It also means we have to take greater care of our own Earth. Clearly we’re not going to be emigrating anywhere else in any hurry.

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If we lived on Proxima b, we’d be residing in the twilight zone

Thursday, 15 September, 2016

No, we shouldn’t get too excited by the prospect that an Earth-like exoplanet circles the star nearest to us. Earth-like it may be, but make no mistake, Centauri b, that orbits red dwarf star Proxima Centauri, is not like Earth. For one thing, the planet is so close to its host star, it is tidally locked. This means it does not rotate on its axis as Earth does.

Therefore it is perpetually day time on one side of the side of the planet, while the other hemisphere is forever cloaked in darkness. One side would be rather warm, the other quite chilly. Only the border between the two, a veritable twilight zone, might be a little Earth-like. On that basis then, it may not be too bad

There will be three different climate zones. The side always facing its star will be consistently sun-baked, receiving scorching, direct sunlight without ever getting a break from it. Similarly, the side facing away from the star will experience eternal night, and should be dark and frozen, but with spectacular views of the Universe. The border between the night and day sides – a “ring” around the planet – will experience an eternal dawn/sunset, with perhaps the most Earth-like conditions.

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Does the solar system play host to an exoplanet? Possibly…

Thursday, 2 June, 2016

The solar system is host to eight regular planets, any number of dwarf planets, and now, possibly, an exoplanet. That’s if the planetary body, known as Planet 9, that is said to orbit on the far fringes of the solar system, can be shown to have originated elsewhere, something mathematical modelling suggests is possible.

Through a computer-simulated study, astronomers at Lund University in Sweden show that it is highly likely that the so-called Planet 9 is an exoplanet. This would make it the first exoplanet to be discovered inside our own solar system. The theory is that our sun, in its youth some 4.5 billion years ago, stole Planet 9 from its original star.

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Planet Nine, a captured exoplanet? How B-grade sci-fi is that idea?

Monday, 9 May, 2016

There has been much talk in recent months about Planet Nine, a would-be planetary body lurking on the extreme far reaches of the solar system. Now astronomers are trying to figure out its origins, with some believing it formed relatively close to the Sun, before being dispatched to the solar system’s outer reaches after a run-in with Jupiter.

Others however think Planet Nine is an exoplanet, a once rogue exoplanet possibly, that was captured by the Sun, after drifting too closely to our solar system.

The final scenario sounds like a plot line from a B-grade sci-fi movie, and it seems to be comparably unlikely. Planet Nine could be an extraterrestrial invader. “Planet 9 may be an exoplanet in our own solar system,” said Gongjie Li, another astronomer at Harvard’s Center for Astrophysics whose recent modelling paper explores this very possibility, among others.

I’m not sure though I like that particular notion being described as “a plot line from a B-grade sci-fi movie”, since it’s an idea I’ve been kicking around, as if it were a cosmic soccer ball, so to speak, in one of my sci-fi writing projects.

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Turn your DSLR to the night sky in the hunt for exoplanets

Thursday, 11 December, 2014

Rather than, say, annoy those you’re dining with, by taking photos of every dish to be served at the restaurant you plan on eating at tonight, why not put your DSLR camera to better use? Better use as in deploying it to search the night sky for exoplanets.

Sure, there are a few hoops to jump through, mainly in building a tracker, but discovering a planet beyond the solar system might rate as quite an achievement.

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715 new planets found in the Milky Way recently, 480 billion to go

Friday, 7 March, 2014

Data collected from the Kepler space telescope has revealed the presence of 715 hitherto unknown planets, in orbits around other stars in the Milky Way galaxy. Many of these planets are thought to be rocky bodies, like Earth.

Most of the 715 exoplanets orbit closely to their parent stars, making them too hot to support life as we know it. But four of the worlds are less than 2.5 times the size of Earth and reside in the “habitable zone,” that just-right range of distances that could allow liquid water to exist on their surfaces.

If each star in the galaxy hosts an average of 1.6 planets though, then it is pretty certain many, many, more exoplanets will come to light in due course.

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Looking for Earth like planets? Well, you won’t have to look too far

Friday, 4 October, 2013

There could be billions – fifteen to thirty billion possibly – of Earth-like planets, capable of hosting life, right here in the Milky Way… this based on observations made by the orbiting, and alas, no longer fully functioning, Kepler telescope, that looked at a mere fraction of a slice of the night sky, over the last four years.

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Exoplanets are us, custom design your own new world

Tuesday, 4 June, 2013

At the rate at which exoplanets are being discovered, it is completely possible we could end up owning one of our own, in the same way, say, that some people own islands. Spending time on your exoplanet, however, may be another matter, especially if the voyage takes a couple of hundred years, which could well be the case.

Enter then PlanetMaker. It will neither give you possession of an exoplanet, nor transport you there within your lifetime, but it will allow you to design – how ever you want – your own such planet. For best results use either Firefox or Chrome.

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Kepler’s ongoing mission to seek out new worlds may be endangered

Thursday, 23 May, 2013

Earth orbiting space telescope Kepler, which has been doing a stellar job of locating exoplanets, looks to be malfunctioning, and may soon be unable to continue searching for planets beyond the solar system:

We attempted to return to reaction wheel control as the spacecraft rotated into communication, and commanded a stop rotation. Initially, it appeared that all three wheels responded and that rotation had been successfully stopped, but reaction wheel 4 remained at full torque while the spin rate dropped to zero. This is a clear indication that there has been an internal failure within the reaction wheel, likely a structural failure of the wheel bearing. The spacecraft was then transitioned back to Thruster-Controlled Safe Mode.

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I’d like to visit an exoplanet that has two suns and three moons

Tuesday, 20 December, 2011

First we found them, then we catalogued them, now we’re preparing to turn exoplanets into holiday destinations.

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