Is a ‘Star Wars’ type galaxy starting to look likely?

Remember that scene in ‘Star Wars: A New Hope‘ when Luke and Obi Wan go into the Mos Eisley cantina? The place was full of aliens. Leaning on the bar, arguing, drinking various foaming substances and playing cool, swing music. If you’ve any sort of interest in science, you’d be like me and go directly into ‘go along for the ride’ mode. It just isn’t probable.

But wait a minute. Just the other day we were told that our very own Milky Way could contain up to 2 billion (yes, billion with a ‘b’) ‘earthlike planets’. Gosh. Two billion planets that could potentially support life like us.

What does ‘earthlike’ mean in this context? The report comes from Kepler’s search for planets orbiting planets like our sun and in the ‘Goldilocks’ zone. Which means the planet is ‘not too hot for liquid water and not too cold’. Kepler can’t actually see any of these planets, their presence is surmised from periodic dimming of the sun’s light as something passes in front of it and from slight perturbations in the sun’s orbit. But scientists can calculate the likely size of the body. For instance, Kepler 22-B is estimated at 2.4 times the size of Earth.

But there’s much more to life on Earth than liquid water and reasonable temperature. The article goes on to quote from “Rare Earth”, a book by Peter Ward and Donald Brownlee, which discusses in detail what would be needed to define a planet as an ‘earth analog’. Some of the things they list don’t readily spring to mind, such as a giant like Jupiter acting as a mine sweeper to reduce the amount of debris penetrating to habitable zones to pose a threat to life. We also need that molten metal core inside the Earth to generate a magnetic field which protects us from harmful cosmic rays. Then we need a breathable atmosphere, a year length not too much different from our own, and gravity at least 80% of our own. (Less than that and the planet wouldn’t hold atmosphere).

We just don’t know enough about any of these planets to know if they’re really ‘earthlike’. The point is made that both Venus and Earth are in the habitable zone around our sun and they are much the same size. But we won’t be setting up a colony on Venus any time soon.

Yes, but that’s humans. Getting back to the cantina scene, we are presented with a number of alien species, all presumably capable of space flight. So what about other life forms on these earthlike planets? Sure, that’s possible – but then we come up against the famous Drake equation (https://en.wikipedia.org/wiki/Drake_equation), which considers variables such as technology and the life of civilisations.

Mind you, Kepler’s discoveries are a breakthrough from the time not too many decades ago (maybe only two) when scientists could do no better than to say that our sun was nothing special so other stars would quite probably have planets. The Drake equation dates back to those times. This is such an exciting time to be interested in the universe. I keep getting this feeling that space travel as written in science fiction might not be all that far away. Soon, it seems, we’ll have places to visit, too.

I’m not too sure I’ll be running auditions for a new cantina scene, though.

NASA OFFERS GOOD NEWS FROM OTHER PLANETS

Hubble telescope image courtesy NASA

Earth-bound biologists, ecologists and climatologists have had little good news to offer us lately. But astrophysicists with their eyes on the skies continue to make new, more wondrous discoveries in exoplanetary science, assuring us that our own little solar system is not alone in the galaxy.

The older-generation Kepler and Hubble telescopes, which gave us our first glimpses of planets circling distance stars, have begun to reach their limit of usefulness. Kepler went dark last October, after almost a decade of observation from Earth orbit; Hubble remains fully functional after five in-orbit repairs but will eventually be replaced by the James Webb Space Telescope due to be launched in 2021. 

NASA’s newest tool in the hunt for exoplanets is the Transiting Exoplanet Survey Satellite, or TESS, which launched last April and began observations in July, 2018. In its first four months of operation, TESS found eight confirmed new planets and 320 more as-yet unconfirmed possibilities, according to Xu Chelsea Huang of MIT.

Observations from TESS are stretching our understanding of planetary formation and what a “planet” can look like. Some of TESS’s discoveries include HD21749b, only 52 light years away, with the lowest temperature known for a planet orbiting so close to a bright, nearby star. 

“If we want to study atmospheres of cool planets, this is the one to start with,” Huang said. The planet has a thick atmosphere, but Huang’s use of the term “cool” is relative: the planet is likely too hot and gassy to support life. Its orbit takes 36 Earth days, the longest known orbital period for planets transiting within 100 light-years of bright stars.

Or take the denizens of the star system Pi Mensae. Pi Mensae c orbits its star every 6.27 days and has a density similar to water; Pi Mensae b has a mass ten times that of Jupiter that orbits the star every 5.7 years in a wildly swinging ellipse—sometimes as close as that of Earth, sometimes as far as that of Jupiter.

Huang describes another planet TESS found, LHS 3844b, as “likely a lava world.” It has a radius just 1.3 times Earth’s, but it swings around its planet every 11 hours, giving it a surface temperature of about 540° C.

All of which goes to show that the universe is stranger by far than anyone could have predicted. These are only the newest planets among the thousands that have been discovered over the last decade by scientists using NASA instruments. And that can only be good news.

Cheers, Donna

*Information for this post taken from “Less than a year after launch, TESS is already finding bizarre worlds,” by Lisa Grossman, Science News, January 8, 2019.

PROXIMA B: HOME TO THE ALIENS NEXT DOOR?

 Scientists from the European Southern Observatory caused a stir this week when they announced the discovery of a planet circling the nearest star to Earth’s own Sol. And not just any old planet, either, but one situated in the so-called “Goldilocks” zone, close enough to the star Proxima to be capable of sustaining liquid water on its surface. The planet, dubbed “Proxima b,” is thought to be rocky and just slightly larger than our own Earth, both conditions that might lead us to think it capable of providing an environment conducive to life.

The Proxima system is the closest solar system to Earth at 4.23 light years. So to find a possibly habitable planet in that system is enough to have heads spinning both in the scientific community and among those whose business it is to mix science and fiction. Another Earth! And practically on our cosmic doorstep!

Artist's rendition of the surface of Proxima b.

Yet for those without much imagination, Proxima b is likely to be something of a disappointment. The planet orbits a red dwarf star, which gives off little heat and not much visible light. And, even though the position of the planet in close orbit compensates in some ways for the low energy output of its star, photosynthesis as we currently know it would not be possible.

Then poor Proxima b is locked in a permanent one-sided relationship with its sun. That is, one hemisphere of the planet is always facing the star (and is thus constantly blasted with heat and radiation), while one hemisphere is always faced away (freezing and desolate). Solar flares and other hazards of the planet’s location close to the unstable red dwarf would make survival on the “day” side dicey. No access to heat or light on the “night” side would make it impossible. Life as we know it could only develop in the twilight zones between the two hemispheres.

Vision for whatever creatures do manage to emerge on Proxima b would be quite different from ours, tuned to the longer wavelengths of the infrared, rather than the shorter ultra-violet rays created by a yellow sun at the peak of its life cycle. They would also be used to a very quick “year” (eleven of our days to make an orbit around Proxima) and no “days” to speak of.

Now a writer with imagination could make a lot of those significant differences from our Earth. I can’t wait to read the first stories about invasion, uh, contact  with the aliens from Proxima b.

Information for this post drawn from: Forbes Magazine, "Starts With a Bang" blog, Ethan Siegle, Contributor, September 6,2016

Cheers,
Donna