News From Space: Alpha Centauri’s “Superhabitable” World

alpha_centauri_newsScientists and astronomers have learned a great deal about the universe in recent years, thanks to craft like the Kepler space probe and the recently launched Gaian space observatory. As these and other instruments look out into the universe and uncover stars and exoplanets, it not only lets us expand our knowledge of the universe, but gives us a chance to reflect upon the meaning of this thing we call “habitability”.

Basically, our notions of what constitutes a habitable environment are shaped by our own. Since Earth is a life-sustaining environment from which we originated, we tend to think that conditions on another life-giving planet would have to be similar. However, scientists René Heller and John Armstrong contend that there might be a planet even more suitable in this galaxy, and in the neighboring system of Alpha Centauri B.

alpha_centauriBb1For those unfamiliar, Alpha Centauri A/B is a triple star system some 4.3 light years away from Earth, making it the closest star system to Earth. The nice thing about having a hypothetical “superhabitable” planet in this system is that it makes it a lot easier to indulge in a bit of a thought experiment, and will make it that much more easy to observe and examine.

According to the arguments put forward by Heller, of the Department of Physics and Astronomy, McMaster University, Hamilton; and Armstrong, of the Department of Physics, Weber State University in Ogden, this planet may be even more suitable for supporting life than our own. It all comes down to meeting the particulars, and maybe even exceeding them.

habitable_sunsFor example, a habitable planet needs the right kind sun – one that has existed and remained stable for a long time. If the sun in question is too large, then it will have a very short life; and if it’s too small, it might last a long time. But the planet will have to be very close to stay warm and that can cause all sorts of problems, such as a tidally locked planet with one side constantly facing the sun.

Our own sun is a G2-type star, which means it has been alive and stable for roughly 4.6 billion years. However, K-type dwarfs, which are smaller than the Sun, have lives longer than the age of the universe. Alpha Centauri B is specifically a K1V-type star that fits the bill with an estimated age of between 4.85 and 8.9 billion years, and is already known to have an Earth-like planet called Alpha Centauri B b.

alpha_centauriBb2As to the superhabitable planet, assuming it exists, it will be located somewhere between 0.5 and 1.4 astronomical units (46 – 130 million mi, 75 – 209 million km) from Alpha Centauri B. All things being equal, it will have a circular orbit 1. 85 AU (276 million km / 172 million miles) away, which would place it in the middle of the star’s habitable zone.

Also, for a planet to sustain life it has to be geologically active, meaning it has to have a rotating molten core to generate a magnetic field to ward off cosmic radiation and protect the atmosphere from being stripped away by solar winds. A slightly more massive planet with more gravity means more tectonic activity, so a better magnetic field and a more stable climate.

 

PlutoHowever, the most striking difference between the superhabitable world and Earth would be that the former would lack our continents and deep oceans – both of which can be hostile to life. Instead, Heller and Armstrong see a world with less water than ours, which would help to avoid both a runaway greenhouse effect and a snowball planet that an overabundance of water can trigger.

Our superhabitable planet might not even be in the habitable zone. It could be a moon of some giant planet further away. Jupiter’s moon Io is a volcanic hellhole due to tidal heating, but a larger moon that Heller and Armstrong call a “Super Europa” in the right orbit around a gas giant could heat enough to support life even if it’s technically outside the star’s habitable zone.

 

alien-worldAccording to Heller and Armstrong, this world would look significantly different from our own. It would be an older world, larger and more rugged, and would provide more places for life to exist. What water there was would be evenly scattered across the surface in the form of lakes and small, shallow seas. And, it would also be slightly more massive, which would mean more gravity.

This way, the shallow waters would hold much larger populations of more diverse life than is found on Earth, while the temperatures would be more moderated. However, it would be a warmer world than Earth, which also makes for more diversity and potentially more oxygen, which the higher gravity would help with by allowing the planet to better retain its atmosphere.

panspermia1Another point made by Heller and Armstrong is that there may be more than one habitable planet in the Alpha Centauri B system. Cosmic bombardments early in the history of the Solar System is how the Earth got its water and minerals. If life had already emerged on one planet in the early history of the Alpha Centauri B system, then the bombardment might have spread it to other worlds.

But of course, this is all theoretical. Such a planet may or may not exist, and may or may not have triggered the emergence of life on other worlds within the system. But what is exciting about it is just how plausible its existence may prove to be, and how easy it will be to verify once we can get some space probes between here and there.

Just imagine the sheer awesomeness of being able to see it, the images of a super-sized Earth-moon beamed back across light years, letting us know that there is indeed life on worlds besides our own. Now imagine being able to study that life and learning that our conceptions of this too have been limited. What a time that will be! I hope we all live to see it…

 

 

Sources: gizmag.com, universetoday.com

News From Space: First Blue Exoplanet Discovered!

HD_189733_b_deep_blue_dotEver since our astronomers have gained the ability to see into deep space and discern what lies in distant solar systems, a total of 910 extra-solar planets have been discovered. Of those, only a handful have been confirmed as potentially habitable by Earth scientists. Despite these discovered, it was not until recently that a “blue planet” outside of the Solar System, thanks to NASAs Hubble telescope.

But here’s the kicker: as it turns out, the planet is not blue due to the presence of liquid water. The blue color likely comes from clouds in the atmosphere made of molten glass. The planet is known as HD 189733 b, located roughly 63 light years away from Earth in the constellation of Vulpecula (aka. the Fox). Initially discovered in 2005 by French astronomers who observed it passing in front of its star, HD 189733 b is one of the best-studied exoplanets.

Hd189733b_blue_planet_artPrior to this new finding, it was already known that the planet was a hot Jupiter — a massive gas giant that orbits very close to its parent star — and that, using polarimetry, it was most likely blue. Since that time, the blue color has been confirmed by a spectrograph aboard Hubble which scanned the planet during an eclipse. As it passed behind its parent star and out of our vision, Hubble recorded less blue light coming from the star, while the other colors remained the same.

This strongly indicates that the light reflected by HD 189733 b’s atmosphere is blue and thus, if we were close enough to directly observe the planet, it would appear blue. This is an apparent first for astrophysicists and astronomers, who wouldn’t normally be able to observe such a fluctuation from 63 light years away. But the size of the planet, plus the amount of light reflecting off it from its very-close-by star, mean that Hubble can do its thing.

blue_planet_image2-640x660As for the cause of the color itself, the current theory is that the planets atmosphere is full of clouds that contain tiny silicate particles, which absorb some light frequencies but reflect and scatter blue light. In the words of NASA, because the surface of the planet is around  815 Celsius (1,500 Fahrenheit), these particles are likely in a molten, liquid state that periodically turn into rain. Yes, you read that right, the planet experiences periods of molten glass rain!

In addition to that, it is also known that its orbital period (length of a year) is only 2.2 days. The planet is also tidally locked, meaning that one side is always facing towards the sun while the other experiences perpetual night. So basically, outside of its blue color, HD 189733 b is about as uninhabitable as it gets.

Ah well, the search for a truly Earth-like exoplanet continues I guess! And in the meantime, enjoy this short video from Hubble ESA – a computer graphic representation of the universe’s other “blue planet”:

Source: Extremetech.com