Is Voyager-1 leaving the solar system?

The Voyager Spacecraft on the edge of the Heliosphere  Image credit: NASA/JPL-Caltech

 Are there any space-program followers that are looking at the Voyager-1 news and scratching their heads?  When I first heard the ship was about to leave the solar system, I was very excited.  As I envisioned the spaceship diving into the deep expanse between the stars, not only did it conjure up images of a beautiful, bald woman demanding to be ‘one with the creator of V’GER[1], it also gave me a sense of pride that a ship from the seventies could last so long and somehow be gravity assisted to such an astonishing speed as to be ‘sling-shotted’ into interstellar space!

According to a NASA news release on June 27^th, the spacecraft had reached 2 out of 3 criteria that would indicate it was in interstellar space.  The Suns charged solar particles have almost disappeared and cosmic rays have increased 10%, what remains is for the spacecraft to detect a switch from the sun’s magnetic field direction to the galactic magnetic field direction.  The particle shifting was expected due to that magnetic shift, but instruments on the spacecraft have not detected the field change, itself[2].  

I recently explored the concept of a human trip to the stars, a program promoted by the One-hundred Year Star Ship organization[3]. As I progressed through my writing exercise I thought something didn’t seem right about Voyager-1’s anticipated breakthrough. As of July 1^st 2013, Voyager-1 was 18½ billion kilometers away from the sun (124 AU)[4]. It’s an astonishing distance when you realized that the earth’s distance from the sun, defining one Astronomical Unit (AU), is a less than 1% of the ship’s travel from its home star.  To further put it in perspective, Pluto’s average distance from the sun is 40 AU (5.9 billion kilometers), its aphelion (greatest orbital distance) is 52 AU (7.8 billion km) from the sun.  We now know Pluto lies in the heart of a region called the Kuiper belt, a region of icy asteroids and planetoids, similar to the asteroid belt, but comprised of rock, ice, and frozen nitrogen extending from 30 to 55 astronomical units.  Pluto was the first of, so far, 1300 Trans-Neptunian Objects (TNOs) detected in the Kuiper belt.  Past Pluto is the largest TNO, Eris, first detected in 2003 and situated in a region called the Scattered Disk, an area that stretches between 55 and 100 AU.  The furthest known plutoid is Sedna, detected in 2004, currently at 90 AU and having an an Aphelion of at least 542 AU. Some scientist place Sedna in the inner Oort cloud, an undefined region of space that is believed by many to be the home of the solar system’s long-period comets[5].  As you see, our physical solar system has been extending further and further out from our traditional boundary of Pluto over the last couple of decades.

It was the knowledge of the Oort cloud that started me to question the statement that Voyager-1 is on the verge of exiting our solar system.  In 1950 Jan Hendrick Oort proposed that the comets came from a common region well beyond the known outer bodies of the solar system[6]. This region was later hypothesized to have two sub-regions, the inner Oort cloud, a donut shaped region that loosely follows the solar system’s ecliptic, and the outer Oort cloud, which is believed to be a spherical shape. Both ‘clouds’ are composed of the same icy materials very loosely tied to the sun’s gravitational influence.  Jan Oort, earlier in his career, was one of the very first people to discover an imbalance in the apparent universe and the gravitation effects it displayed.  This imbalance is now attributed to what we call dark matter. His Comet region theory attempted to partially explain the unaccounted for mass found in the galaxy. This cloud of scattered ice is believed to be the remaining proto-planetary material that made the solar system and its sister stars.   Due to its extreme remoteness and difficultly to verify observationally, the Oort cloud is still technically considered hypothetical. Still, most scientists accept its existence.

So far, only three Trans-Neptunium objects have been found that lie in the Oort region:

Designation	Peirhelion (AU)	Aphelion (AU)
90377 Sedna	76.23	542.66
2000 CR105	44.12	228.78
2006 SQ372	24.17	813.15

[7]

Only Sedna lies entirely outside the Kuiper belt region, the other TNOs start their highly elliptical orbits within the Kuiper Belt and extend well beyond the Scattered Disk Region.  The Inner or ‘Donut Oort’ is believed to be between 100 and 2,000 AU, the Outer or ‘Spheroid Oort’ is believed to range from 2,000 to 50,000 AU, some theorist put the outer shell as far out as 100,000 AU. That distance would put the Oort cloud nearly half way to Proxima Centauri, our closest stellar neighbor.  The extents of the Oort cloud will remain subject to interpretation having only three objects for a data set, and these extents cannot be defined until we have much more information and many more candidates.

So then, is the Voyager-1 leaving the solar system?  Under the definition of the sun’s magnetic field it appears that it is about to leave, but if the Oort cloud is part of the solar system, which seems to me it is, then Voyager-1 still has a long way to go. Even if we limit the solar system to the outer extents of the smaller, Donut Ort, then the spacecraft has only completed 6% of its journey to the edge of our system.

It is still an amazing accomplishment! It’s also coincidental that as Voyager treks on at 3.6 AU per year[8] our grasp of the solar system extends in conjunction with its reach.  In 2020 when the power supply of the ship is expected to be depleted, what will be our understanding of the extents of the solar system?

At 150 AU, will Voyager-1 still be within the realm of Sol? Or, has it already left us?

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[1] Star Trek: the Motion Picture, Dir: Robert Wise, Wri: Gene Roddenberry and Alan Dean Foster, Perf: William Shatner, Leonard Nimoy, Persis Khambatta, Stephen Collins. Paramount Pictures, 1979. Film

[2] Philips, Tony “Voyager 1 approaches interstellar space”, NASA, NASA news services, 27 June 2013, WEB, retrieved 20 June 2013, http://science.nasa.gov/science-news/science-at-nasa/201327jun_voyager

[3] “100 year Starship”,100 Year Starship, 100 Year Starship, n.d. WEB, retrieved 20 June 2013, http://100yss.org/

[4] Chang, Allicia “NASA’s Voyager 1 spacecraft encounters unknown Region of space at solar system’s edge”, Huffpost,TheHuffingtonPost.com, Inc.,28 June 2013,WEB, retrieved 30 June  2013, http://m.huffpost.com/us/entry/3515547

[5] Brown, Mike “Sedna (2003 VB12)”,Caltech Division of Geology and Planetary sciences, California Institue of Technology, n.d. WEB, retrieved 1 July 2013, http://www.gps.caltech.edu/~mbrown/sedna/

[6] Erickson, Kristen “Kuiper Belt & Oort Cloud: Read More”, NASA Solar System Exploration, NASA Science Mission Directorate, 26 April 2013, WEB, Retrieved 3 July 3, 2013, 7/3/13 7:37 AM http://solarsystem.nasa.gov/planets/profile.cfm?Object=KBOs&Display=OverviewLong

[7] Yeomans, Donald K “JPL Small-Body Database Browser”, NASA Solar System Dynamics, NASA Jet Propulsion Laboratory, 2013-Jul-04 02:07 UT (server date/time), http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2005CR105

[8] Angrum, Andrea, “Voyager the interstellar mission”, NASA Solar System, NASA Jet Propulsion Laboratory,  n.d., WEB, Retrieved 3 July 2013, http://voyager.jpl.nasa.gov/mission/interstellar.html

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Seventeen Billion Earth Like Planets and we are all alone....

17 billion earth-like planets, and My God, we are probably and profoundly alone!

In January the Harvard-Smithsonian Center for Astrophysics had released and estimation that there are 17 billion earth sized planets in our galaxy based on NASA’s Keppler mission Data.[i]  NASA repeated the findings and continued to talk of Keppler’s mission to find earth-like planets.[ii]  Soon, almost every internet news site was announcing 17 billion ‘earth-like’ planets.

The problem is their definition of ‘earth-like’ is any terrestrial planet whose size is smaller than Neptune, with some of those over three of four times the size of Earth.  NASA did admit that the vast majority of those known ‘earth-like’ planets are too close to their suns, making them inhospitable.

Fine, so let’s assume 10% of those planets are in the goldilocks zone, the zone in orbit where it’s not too hot and not too cold for liquid water to exist, but just right. This 10% also incorporates a habitable zone for stars. Stars also can get too close to the center of the galaxy, exposing their worlds to extreme cosmic radiation.[iii] That still leaves us nearly 1.7 billion, more reasonably labeled, ‘earth-like’ planets.

The goldilocks zone is still a rather vague criterion for ‘habitability’ though.  Our solar system has three planets in the goldilocks zone.  And so far, we have discovered only one other system with three planets in the goldilocks zone.  Here at Sol, we have Venus which is surrounded by a hot, dense blanket of carbon dioxide and temperatures that can melt lead; Venus is totally hostile to life.  We also have Mars which is too cold, dry, and naked to cosmic radiation for any perceptible life. It may have had conditions more favorable for life before, but there is, so far, nothing to show life is or even was on the 4^th planet.   These two neighbors of ours are most likely the norms.  If Mars is so small it couldn’t support a dense atmosphere and therefore life, then any planet smaller probably can’t either.  If Venus, being smaller than earth, still accumulates a dense hostile atmosphere, then any of those planets larger than earth are very likely tobe susceptible to the same problem.  But let us assume 10% of the 1.7 billion worlds might still harbor life or 170 million planets.

While our planet’s habitability was threatened by cataclysmic events, one of those events can actually be credited to life’s continued history.  Slammed by a mars size planet early in our history, we consequently were given a moon whose gravitational tidal effects, maintains our planet’s tectonic activity, and possibly its long lasting magnetic field.[iv]  This magnetic field is essential for protecting life and Earth is the only known terrestrial planet that has a field of any strength.[v]  So of those 170 million potentially habitable planets we currently have, 10% are truly habitable for life (I think I am being generous). That still gives us 17 million truly ‘earth-like’, life-harboring planets.

The history of life on this planet has been tumultuous.  There have been mass extinctions at the rate of every 100 million years during our turbulent 3.5 billion year life bearing history. An asteroid, only a little larger then the one that killed off the dinosaurs, could have wiped out ALL of life.  Not all threats are extra-terrestrial either. The planet itself has nearly destroyed life in its far distant past with super-volcanoes and ice-sheets that covered the entire globe.[vi]  There is evidence that life had nearly destroyed itself by releasing a toxic substance earlier in its history, (that toxic substance was called oxygen, but more on that later).  Let’s say that 10% of the ‘earth-like’ planets actually maintain to sustain life.  That means there are 1.7 million earth-like planets that have life in our galaxy.  That is an awesome thought and an exciting premise.

Now our history as a living planet, is mostly microbial.  If there is life on mars (or was), it is almost certainly microbial.  Of the life forms on earth, even now, the vast majority are the much smaller, less complex prokaryotal (bacterial) single-cell life forms. Cell for cell there are 10 times more bacteria in your last stool then the number of cells that makes up your body. It was only after 1.5 billion years of life that the larger more complex single cell life form, called eukaryotic cells seemed to have evolved.   These larger, more complex life forms fed off mostly the prokaryotes, and each other.  It was in these life forms that the DNA Double Helix evolved.  About a half a billion years after they had emerged in our world, a eukaryotic cell went to absorb a prokaryotal cell, but it did not digest it. Instead, for some unexplained reason, it assimilated it. They not only lived together symbiotically, but the DNA structure of the host cell eventually altered to reproduce the embedded prokaryotal when it reproduced itself.  This assimilated prokaryotal cell structural was the first mitochondria.[vii]  The mitochondria, complete with their own DNA are essential for eukaryotic life to survive and even thrive under an oxygenated environment.  The ability of the cells to use oxygen had raised their energy states, a mitochondrion enhanced living cell has a much shorter life, but it is a very dynamic and energized life. The eukaryotic life flourished, and the high metabolism allowed the development of coordinating, multi-cellular life forms.  Multi-cellular life is a very lucky by-product of a very lucky symbiotic relationship.  It’s fair to say this would be a very rare event.  It took the earth 2.5 billion years of single cell life before multi-cellular life could evolve. Given the unusual and complex symbiotic relationship and the time frame, I estimate there are only 1% of the planets mentioned with complex life, life developed into a multi-cellular form.   This estimate is probably very generous considering it took half of life’s 5 billion year history to reach this point.

That means 17 thousand planets in our galaxy have multi-cellular life.  Think about it! 17,000 planets teeming with growing, crawling, swimming, climbing creatures.

Once again, looking at earth’s history, humans are the only creatures we know of that have had sentience.  To some that may be unfair, when you consider intelligent animals like the whale or higher apes, but if you consider our writings and our ability to model the earth for our use, you should accept that we are at least different, cognitively.  Of the 1 billion years that complex life has swarmed the earth, Homonoids has been here a mere 1 million years of it.  If you consider only Homosapiens, excluding Neandrathals and Homo Habilis you could reduce that time frame to 100,000 years. Assuming the entire Homonoid family as a sentient, environment changing creature, that would mean 0.1% of the planets in the galaxy have had time to develop sentient creatures.

That means there are 17 planets in the galaxy that have sentient, environment changing beings.

Again, looking at our history in the last 1 million years, we have only just begun to build a technology that can explore the universe. We only now can send probes into space, can look at the universe through a telescope and realize it is expanding.   We have just learned the fundamentals of relativity, electronics, and physics in the last 100 years and use them to explore beyond our frail world.  That’s 0.01% of our existence.   That means statistically, there is only one planet in our galaxy that has reached the sentient awareness of the universe around them.

One planet, us!

Using the above percentage, that also means one planet per 29,000 galaxies that have life aware of the universe and its origins.

So statistically we are alone, but we are very, very, very, very special.

   

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[i] Aguilar, David and Christine Pulliam, “At least one in six stars has an earth-sized planet”, Harvard-Smithsonian Center for Astrophysics, Harvard University in conjunction with the Smithsonian Astrophysical Observatory, 7 January 2013, WEB, retrieved 29 June 2013, http://www.cfa.harvard.edu/news/2013/p201301.html

[ii] Michele Johnson, “Kepler mission news: At least one in Six stars has an earth-sized planet”, NASA, NASA news,10 January 2013, WEB, Retrieved 29 June 2013, http://www.NASA.gov/mission_pages/kepler/news/17-percent-of-stars-have-earth-size-planets.html

[iii] Mullen, Leslie, “Galactic Habitable Zones”, Astrobiology Magazine, FirstGov - NASA, 18 May 2001, WEB, Retrieved 29 June 2013, http://www.astrobio.net/exclusive/139/ 

[iv] Canup, Robin and Erik Asphaug,). "Origin of the Moon in a giant impact near the end of the Earth's formation". Nature, Vol. 412 16 August, 2001: 708–712, Retrieved 2013-12-10, http://www.es.ucsc.edu/%7Ercoe/eart206/canup_Moon_Nature_01.pdf

[v] table: http://www.astronomynotes.com/solarsys/plantblb.htm based on NASA planetary fact sheet by Williams, David “Planetary Fact Sheet – Metric”, NSSDC, Goddard Spaceflight Center, 28 September 2012, WEB, retrieved:unknown,  http://nssdc.gsfc.nasa.gov/planetary/factsheet/

[vi] Shields-zhou, G.A. with A.C. Hill and B.A. Macgabhann ”Chapter 17: The Cryogenian Period”, University of Maryland – Department of Geology, Felix M. Gradstein, James G. Ogg, Mark Schmitz and Gabi Ogg. Published by Elsevier B.V., 2012, PDF, Retrieved 29 June 2013, http://www.geol.umd.edu/~hcui/NeoproterozoicGeobiology/GeolTimeScale2012/Ch17-Cryogenian.pdf

[vii] Carprette, David R. “Evolutionary Origin of Mitochondria”, Rice University,, 26 May 2005, WEB, Retrieved 29 June 2013, http://www.ruf.rice.edu/~bioslabs/studies/mitochondria/mitorigin.html