Friday, September 6, 2013

Exoplanets and Extraterrestrial Life: The Search Continues

We've learned a great deal: and are discovering that there's much more to learn.

Not long ago, scientists wondered if planets circled other stars. Today, they've found hundreds: and are looking for life beyond the Solar system.
  1. Planets of Red Dwarfs: Informed Speculation
  2. Reviewing Kepler

Space Aliens?

I'd be delighted by news of life on Mars, or in Ceres, or anywhere else in the universe. When, or if, we find extraterrestrial life, I'm quite sure it won't look like what's been in the movies.

I've seen fictional space aliens go from the villains of "Earth vs. the Flying Saucers" to "Close Encounters of the Third Kind" and "Aliens." I think these movies say more about the audiences they were aimed at than what we may find on other planets, and that's another topic.

Expectations, Reasonable and Otherwise

Maybe we'll find people like us: self-aware spirits with physical bodies, able to make reasoned decisions. That would be really exciting. We could learn what parts of our human experience come from being human: and what are part of being a person of any species.

There could be trouble, too. Some folks might expect our neighbors to bring peace, joy, and an end to all problems: the cargo cult attitude I saw in some 'flying saucer' enthusiasts. That sort of adoration of a thing or person other than God is a really bad idea. (Catechism of the Catholic Church, 2112-2114)

We might even learn that movies like "Invaders from Mars" and "Independence Day" were right, and there's an alien armada heading our way. That'd be trouble of a different sort, and highly unlikely. My opinion.

Alone, or Not?

A big question is whether or not there's life elsewhere in the universe, and whether we've got this place to ourselves or have neighbors. I'm quite certain that we don't know, and that the answer to both might be "yes."

I'm pretty sure that some folks won't like the idea that we're not alone. That's nothing new. Seven centuries back some of Europe's serious thinkers said that other worlds couldn't exist: because Aristotle said so.

That's when the Church stepped in. Ever since 1277, saying that other worlds can't exist has been against the rules. (January 29, 2012)

I've posted about our search for extraterrestrial life fairly often:

1. Planets of Red Dwarfs: Informed Speculation

"Are Exoplanets Orbiting Red Dwarf Stars too Dry for Life?" (August 27, 2013)

"If water is the source of life, then finding the source of water certainly qualifies as a worthy astrobiological endeavor. Scientists have formulated certain scenarios for how our planet became wet and stayed wet, but other planets may not have been able to tap this same source.

"One place where water availability could be a problem is around low-mass stars.

" 'Low-mass stars are appealing from an astrobiology point of view because there are so many of them,' said Fred Ciesla of the University of Chicago...."
I usually call still-hypothetical study of life that's not on Earth exobiology. Astrobiology is another word for the same thing, and I wrote about that last week:

Damp, Dry, Drenched, and Otherwise

Life, the sort we're familiar with, isn't particularly picky: but liquid water is a must.

It doesn't have to be a whole lot of water. 'Damp' will do for some critters. Others wait out long dry spells punctuated by torrential rain.

Temperature limits on what's "habitable" are wider than we thought. Some critters get along fine where water is solid most of the year. That wasn't a surprise, since the current iteration of Western culture started near the Arctic circle.

Starting about three decades back, we started finding things like giant tube worms living where water is near the boiling point. That was unexpected.

Scientists found so many critters living in extreme conditions that they made a new word to describe them: extremeophile. Some extremeophiles aren't remarkable for thriving where it's hot or cold. Some like acid, or can't endure oxygen, and that's yet another topic.

How Planets Form

"...The class of M dwarf stars - which weigh between 10 and 50 percent the mass of our sun - are the most common stars in our galaxy. A recent analysis of data from NASA's Kepler spacecraft showed that six percent of these red dwarf stars likely have habitable Earth-size planets.

"Habitability in this case is defined by surface temperatures that are conducive to liquid water. But what if there is no water there to begin with? Indeed, previous research using computer simulations suggested that planets near M dwarfs might be devoid of water....

"...Recent understanding about the formation of our solar system suggests that the source of planetary water is a complicated business that depends on the environment that the central star is born in. This could change the prognosis for water around M dwarfs...."
Scientists had quite a few ideas for how planets formed in my youth. In my youth some textbooks said the Solar system might have started when our star and another collided.

Stars are so far apart in our part of this galaxy that collisions almost never happen, so if that theory was right, Earth might be unique. Right now it looks like our moon formed when another planet hit Earth, and that's almost another topic.

Scientists started getting much more data about stars and planets toward the end of the 20th century.

Somewhere in the universe there may be planets that formed when two stars collided, but nearly all planets apparently develop when a cloud of gas and dust collapses into a disk. The disk's center has most of the material, and becomes the star; what's left becomes planets. That's an oversimplification. Moving on.

I think the 'collapsing cloud' explanation for how stars and planets form is probably correct, since we've spotted quite a few planetary systems 'under construction' around new stars.

Earth, Water, Heat, and Aluminum-26

Earth's water is a bit hard to explain, since our part of the Solar system was almost certainly too warm when this planet formed. This world's oceans are quite real, though: so the water came from somewhere.

Right now it looks like our water came from rocks and dust that collected ice crystals outside the "frost line." That's about 2.5 times the distance from Earth to the sun. The early Solar system wasn't as sedate as today's, so debris had ample opportunity to get sent inward.

Stars with less mass that ours start with smaller clouds, which means smaller disks. On top of that, they're quite a bit hotter when their fusion fires light up. If all stars started with the same ingredients, low-mass stars might have Earth-size planets in 'habitable zone' orbits: but with those icy rocks too few and far out to form oceans on the Earth-size world.

But all stars and planets aren't created equal. Our planet had more aluminum-26 than usual. It's an isotope of aluminum with a half-life of about 700,000 years. Decaying aluminum-26 probably heated Earth more than the average planet of that size.

In a low-mass star's system without as much of this unstable isotope, an Earth-size planet might stay cool enough to keep more of its original water. Maybe enough to form oceans.

Then again, maybe not. We still don't know, one way or the other.

What sort of planets circle other stars is still informed speculation: but the flood of new data makes it more "informed" and less "speculation."

2. Reviewing Kepler

(Dr. David Koch, Kepler Deputy Principal Investigator, via Wikipedia, used w/o permission.)
Cutaway view of the Kepler observatory.
"Planet-Hunting Days of NASA's Kepler Spacecraft Likely Over"
Mike Wall, (August 15, 2013)

"The revolutionary planet-hunting activities of NASA's prolific Kepler space telescope have come to an end.

"NASA has given up hope of restoring the Kepler spacecraft to full health and is now attempting to determine what the observatory can accomplish in its compromised state, agency officials announced today (Aug. 15).

" 'We are now moving on to the next phase of Kepler's mission, because that's what the data requires us to do,' Paul Hertz, director of NASA's astrophysics division, told reporters during a press conference today. 'This is not the last you'll hear from Kepler. There's a huge amount of data collected that we'll continue to analyze.'..."
"A huge amount of data" is an understatement. So far, scientists have found 150 planets by analyzing what Kepler reported. Results aren't in yet on the 3,548 sets of data that may show a planet: or not.

Kepler searched for planets by recording light from stars in part of the constellation Cygnus. Light from some of the stars gets a little dimmer at regular intervals. Sometimes the light dims because a planet circling that star gets between us and the star.

Sorting out planet shadows from other reasons for changes in brightness is complicated, so 150 'definite' planets and more than 3,000 'maybes' so far is doing pretty well. My opinion.

What struck me was how many planets Kepler found this way. Kepler planners picked that spot in Cygnus because relatively nearby stars are thick there, but the only planets Kepler could spot were those whose orbits happened to take them exactly between the star and us.

On top of that, the Kepler telescope only paid attention to stars within 3,000 light years of Earth. On a galactic scale, that's 'nearby.'

(Painting by Jon Lomberg, Kepler mission diagram added by NASA, Smithsonian via Wikipedia, used w/o permission)

End of Kepler's Planet Hunt

"...The $600 million Kepler mission launched in March 2009 on a 3.5-year prime mission to determine how commonly Earth-like planets occur around the Milky Way galaxy.

"Kepler detects exoplanets by noting the tiny brightness dips caused when these worlds cross in front of, or transit, their parent stars. The observatory needs three working reaction wheels - gyroscope-like devices that maintain Kepler's position in space - to do this precision work.

"Kepler had four of these wheels when it launched - three for immediate use and one spare. But one wheel, known as number 2, failed in July 2012. And then wheel four conked out on May 11 of this year, halting the spacecraft's planet hunt...."
(Mike Wall,
What's important here is that Kepler is still a useful research tool. With only two reaction wheels out of service, it doesn't have the extreme stability needed for planet hunting. But scientists may find ways to use the space telescope. The last I heard, we might learn whether the Kepler program keeps going in a few months.

Getting Technical

"Kepler Mission Manager Update: Pointing Test Results"
NASA press release (August 19, 2013)

"Following months of analysis and testing, the team is ending its attempts to restore the spacecraft to full working order as the recent pointing test proved unsuccessful. We are now considering what new science research it can carry out in its current condition.

"On Aug. 8, engineers conducted a system-level performance test using Reaction Wheel 1 (RW1), 2 and 3. RW1 and 3 are the 'good' wheels that have shown no signs of degradation. RW2 is the one that failed in July 2012. The test was conducted to see if the wheels, demonstrated to at least still spin on command, could adequately control spacecraft pointing...."
I love reading this sort of stuff. Your experience may vary.

A Two-Wheel Kepler and NASA

"...The spacecraft was returned to its point rest state, which is a stable configuration where Kepler uses thrusters to control its pointing with minimal fuel use.

"The team will now perform an engineering study to assess what modifications are required to manage science operations with the spacecraft using a combination of its remaining two good reaction wheels and thrusters for spacecraft attitude control.

"Informed by contributions from the broader science community in response to the call for scientific white papers announced Aug. 2, the team also will perform a study to identify possible science opportunities for a two-wheel Kepler mission.

"Depending on the outcome of these studies, which are expected to be completed later this year, NASA HQ will assess the scientific priority of a two-wheel Kepler mission. Such an assessment may include prioritization relative to other NASA astrophysics missions competing for operational funding at the NASA Senior Review board early next year...."
(NASA press release)
Even if the Kepler telescope is shut down, we've still got data collected from 2009 to 2013: and probably hundreds of planets waiting to be found. Maybe thousands.

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From time to time, a service that I use will display links to - odd - services and retailers.

I block a few of the more obvious dubious advertisers.

For example: psychic anything, numerology, mediums, and related practices are on the no-no list for Catholics. It has to do with the Church's stand on divination. I try to block those ads.

Sometime regrettable advertisements get through, anyway.

Bottom line? What that service displays reflects the local culture's norms, - not Catholic teaching.