In 2003, astronomers using the Hubble Space Telescope discovered something amazing deep in the M4 globular cluster 7,200 light years away—something that shouldn’t be: a planet, 2.5 times the size of Jupiter, orbiting 23 AUs from a pulsar (a rotating, pulsating neutron star), PSR B1620-26. The primary star, the pulsar, has a companion white dwarf orbiting approximately 1 AU out.
According to current theories, planets could not form in the early universe 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 (on that old a planet, life would have had 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 were exiled?
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 their magnetic axes. 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.
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, “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 theorise 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 theorise 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 away 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 and 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 Methuselah and any other world(s) circling PSR B1620–26 were “adopted,” right along with their sun. If so, could one of them develop life before being captured by the pulsar or 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 a life would face is that being captured by the pulsar would prove to be quite a 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 found themselves in a crowded neighborhood, they could explore nearby systems and move to one that was safer, though it is doubtful any planetary system in the core of a cluster would be safer, especially any system that was lingering in the core and thus increased the chances of itself colliding with another star system. No, more likely, they would have to figure out how to best 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 it is still thought that lingering too long in a cluster is not the best environment for life, a globular cluster has many stars in relatively close proximity; a supernova from a nearby star can have devastating effects on the planets of neighbouring star systems, and being in a globular cluster increases your chances of being near a supernova.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 old. It is thought that for the first 10 billion years, Methuselah led a “normal” life around a normal sun-like star. And, if so, could that life evolve into a space-faring species?Are there descendants scattered about the Milky Way (or at least in that region of the Milky Way)?
Notes:
- Early stars lacked heavy elements and thus could not form planets; however, when they died, they produced heavy elements, which became part of new nebulae within which new stars were born, and with heavy elements now in the mix, planets could finally be formed.
- 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 dwarfs.
