Saturday, January 5, 2008
Methuselah - 13 Billion Yr Old Planet (Garden of Eden?)
According to current theories, planets could not form in the early universe (1) - for one thing, early stellar nurseries shouldn't have enough heavy elements to create stars with planets. But somehow at least one planet was formed in the young universe - while the universe is 14 to 15 billion years old, this planet, dubbed Methuselah, is nearly 13 billion years old.
Imagine that - a planet almost as old as the universe itself. Could a civilization have arisen there? Or died out and rose again (that old of a planet, life would have time to restart several times)? And in the final years, moved out into the stars?
I can't help but think of old races often called "The Ancients" or similar such nomenclature in science fiction tales - very old races that seed the rest of the galaxy before ascending or mysteriously moving on to other galaxies, leaving this one behind.
And if life first began in this universe on such an old planet (or, more likely, a smaller sister planet), could that then be the real Garden of Eden, from which Adam and Eve where exiled from?
Of course, orbiting a pulsar is dangerous for life for two reasons: 1) a pulsar is a result of a supernova which tends to destroy worlds (strip away the atmospheres at the very least) and 2) pulsars give off extremely intense beams of radiation along the lines of its magnetic axis - if any planet is in the path of the beam of the rapidly spinning star, the radiation would be too intense for life to survive or form (2).
As we have seen in a previous post, Planets, planets everywhere, planets can reform around a pulsar - from the rocky debris of the original planets, blasted from the supernova explosion.
Scientists, however, do not feel that Methuselah is a "reconstituted" planet. One theory is that the planet (and maybe others too small to be detected by present means) was captured from a sideswipe with another younger system later on - a system that existed for 10 billion years before wandering too deep into the core of the globular cluster, where distances between star systems can sometimes be less than 1 light year.
Recall from an earlier post, An Aside - Are There Alien Worlds in Our Own Solar System?, there is some evidence that our own solar system has "adopted" objects from an alien solar system passing by in the distant past - possibly when it was still in an open globular cluster (scientists theorize that our sun was first formed in an open cluster).
In fact, the scientists feel that the white dwarf companion was also "adopted" by the primary neutron star. They theorize that the pulsar did have a dwarf companion at first, but when a yellow star system came too close, the gravitational tug-of-war kicked out the dwarf and the yellow star took its place, along with at least one of its planets. The new system then moved out from the core of the globular cluster - reducing any chances for further collisions.
In this new binary system, some of the mass from the yellow star got sucked into the pulsar, speeding up its rotation, giving it the incredible spin rate of 100 revolutions every second. After some millions of years, the yellow star became a red giant and then a white dwarf.
So it is quite possible that the Methuselah, and any other world(s) circling PSR B1620-26, were "adopted," right along with their sun. If so, could one of them developed life before being captured by the pulsar/dwarf system? Early planetary systems would most likely be made up of gaseous planets - there shouldn't be enough heavy elements for terrestrial planets to form. But then we didn't think any planets as old as Methuselah should exist either. Maybe, just maybe, a small terrestrial planet does exist along with Methuselah. And even if not, life is not necessarily restricted to terrestrial planets - life could begin and thrive on non-terrestrial planets (albeit, such life would not be life as we know it).
One problem such life would face is that being captured by the pulsar would prove to be quite the dramatic change. If they are lucky, the radiation beam from the pulsar would point far above the ecliptic, thus avoiding being bathed in intense radiation every 1/100th of a second; but even then, the difference in light (and heat) would be devastating as it is rather certain the planets' new orbits around the binary pair would be different than when they were just circling around their single parent star. But as we see on Earth, life, once formed, is tenacious and will find a way to survive, even during the occasional mass extinctions.
For intelligent life, depending upon their level of technological advancement, they could migrate to a sister world circling the new binary system, one that was now more hospitable than their home world. Otherwise, they would be forced to adapt to their new, darker, colder world. Or, if they were highly advanced at the time the collision was imminent, and finding themselves in a crowded neighborhood, could explore nearby systems and move to one that was safer -though it is doubtful any planetary system in the core of cluster would be safer, especially any system that was lingering in the core, and thus increased chances of itself colliding with another star system. No, more likely they would have to figure out how best to ride out the collision.
At first scientists thought planetary systems couldn't survive long in a cluster, especially a globular cluster - but increasing evidence is showing that sometimes this is not the case. Although, lingering too long in a cluster is still thought not the best environment for life; for one thing, a globular cluster has many stars in relatively close proximity - a supernova from a nearby star can have devastating effects for life on the planets of neighboring star systems and being in a globular cluster, chances for being near a supernova are rather high. For the Earth, a supernova 30 light years or closer would be quite devastating for life - for other planets, the distance could be greater, depending upon how thick their protective atmospheres are (to show you how protective our atmosphere is, for astronauts outside the Earth's atmosphere, a supernova 3,000 light years away could be deadly).
But, it is not impossible. That extrasolar system could have been one of the earliest gardens of life in the universe. 12.7 billion years ago the planetary system was formed. Our own system is "merely" 4.5 billion years. It is thought that the first 10 billion years Methuselah led a "normal" life around a normal sun like star. And if it was, was that life able to evolve to a space faring species? Are there descendants scattered about the Milky Way (or at least in that region of the Milky Way)?
1. Early stars were poor in heavy elements, and thus could not form planets, but when they died, they produced heavy elements which then became part of new nebulae within which new stars were born - and with heavy elements now in the mix, allowing planets to finally be formed as well.
2. While pulsars are formed from massive stars, white dwarfs are formed from the average main sequence star - most stars in the galaxy will end their lives as white dwarves.
Britt, Robert Roy. "Primeval Planet: Oldest Known World Conjures Prospect of Ancient Life." Science. SPACE.com. 10 July 2003. 6 January 2008. <http://www.space.com/scienceastronomy/oldest_planet_030710-1.html>
"Extrasolar Visions - 'Methuselah' PSR B1620-26 c." Extrasolar Planet Guide. 5 January 2008. <http://www.extrasolar.net/planettour.asp?PlanetID=30>
"Messier Object 4." The Messier Catalog. SEDS. 21 August 2007. 6 January 2008. <http://www.seds.org/Messier/M/m004.html>
Mukai, Koji and Eric Christian. "Destruction of the Earth by a Nearby Supernova." Ask an Astrophysicist. Imagine the Universe! 1 December 2005. 5 January 2008. <http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/980521a.html>
"Oldest Planet Challenges Existing Theories." This Week in Science. 11 July 2003. 5 January 2008. <http://www.twis.org/2003_07_11_science_news.html>
Richmond, Michael. "Will a Nearby Supernova Endanger Life on Earth?" 8 April 2005. 5 January 2008. <http://stupendous.rit.edu/richmond/answers/snrisks.txt>