Dr. Bortrum
07/01/2016
More on Hobbits and Exploding Stars
CHAPTER 70 Supernovae and Evolution
In my last two columns I touched on some topics related to evolution. In one column I mentioned the finding that the so-called "hobbits" who lived on the Indonesian island of Flores did not overlap with modern humans there, as originally seemed a possibility. A reanalysis of the dating of the fossils showed they were on the island over 60,000, not 18,000, years ago. In an article in the June 10 issue of Science, Elizabeth Culotta cites more recent work published by the same team of researchers in the journal Nature. The more recent work may indicate the origin of these little fellows and gals. The team found at another site in Flores a jawbone and teeth from a fossil or fossils dated at around 700,000 years ago! These fossils indicate these much earlier hobbits were even smaller than those living some 600,000 years later.
Although the researchers were not yet ready to positively state such a claim, the evidence indicates the possibility that the "hobbits" were descendants of the much taller Homo erectus, which arrived on the island about a million years ago. If so, the decrease in size would have been due to "island dwarfing", a process in which the large homo erectus individuals evolved to grow smaller due to the relative scarcity of food and other resources on the island. Such a process took place in the case of elephants, with pigmy elephants having been found on the island.
Well, having brought you up to date on the hobbits, let's turn to exploding stars and supernovae, which have played a crucial role in the evolution of all life here on Earth. Of course, we humans and all other life on our planet would not have evolved if the elements of which our bodies are composed did not exist. My first awareness of the sources of many of these elements probably came from hearing Carl Sagan expounding on "starstuff". He was talking about explosions of stars being the source of the heavier elements of the Periodic Table. The Big Bang gave rise to hydrogen, helium and some lithium but virtually all the rest of the elements, such as carbon, nitrogen, iron and a host of other elements found in living things were formed (and distributed) in the nuclear furnaces and violent explosions of stars. I must have discussed this in past columns but, until reading an article by astrophysicist Daniel Kasen titled "Stellar Fireworks" in the June 2016 issue of Scientific American, I didn't appreciate the frequency and variety of stellar explosions, supernovae.
A supernova is a big deal, lighting up the sky as brightly as a million suns. Only problem, since the supernovae detected to date are, thankfully, so far away that they appear to us as little specks of light that typically don't shine very long, possibly a few weeks, and then disappear. Until relatively recently, spotting a supernova was a rare event. However, with new telescopes, computer image processing and pattern-recognition technology, Kasen says that today we see thousands of supernovae in a year and that in a week we spot as many of them as were seen in all of the 20th century! The situation is similar to the ability to spot new planets, as we discussed last week, thanks in large measure to computer technology.
Kasen describes a "supernova zoo" of different types of supernovae. There's the "ordinary" supernova that results when a star having a mass of 10 or more times that of our Sun runs burns up all its nuclear fuel and collapses forming a neutron star. In the process, the outer layer explodes sending its debris containing all those goodies like carbon, silicon, iron, calcium and a host of other elements that we relied upon to form life on our planet and atmospheres that formed from such debris. The neutron star left behind in the supernova explosion is a weird beast, packing something like the mass of our Sun in a star measuring only a few miles in diameter!
There are lots of neutron stars and they often get close enough to orbit each other and eventually crash into each other. You might think this would really set off a super supernova but chances are instead that the two neutron stars would be so massive that they would form a black hole and only a small part of their mass would escape making the result a relative dud of a supernova. Another relative dud of a supernova could be the case of a really, really big star have the mass of a few hundred or even a thousand times the mass of our sun. The huge gravity in such a star would pull virtually all of it into the form of a black hole and hardly anything would escape as a supernova.
There are other kinds of supernovae that do light up more brightly than the "ordinary" supernova. One of the brightest occurs with a so-called "magnetar", which results when a rapidly rotating star of 10 or more more solar masses collapses forming a rapidly rotating magnetized neutron star. The formation of this "magnetar" can produce a brightness of about a trillion suns, compared to a brightness of about a billion suns for the "ordinary" supernova.
On numerous occasions, I've expressed my admiration for the patience exhibited by those who are or have been associated with long-term missions and studies of our universe. One such mission is NASA's Advanced Composition Explorer (ACE) mission, launched back in 1997. One of the elements that play an important role in our bodies is iron, Fe to us chemists. As noted above. iron is one of those elements that originates in exploding stars. In the May 6 issue of Science there's an article by W. R. Binns and 10 co-authors titled "Observation of the 60Fe nucleosynthesis-clock isotope in galactic cosmic rays". One of the instruments aboard the ACR spacecraft is a cosmic ray isotope spectrometer (CRIS), which is used to identify various isotopes of elements found in cosmic rays.
The isotope 60Fe (iron-60) is an isotope with a half-life long enough (2.6 million years) that we might expect to see some of that form of iron in cosmic rays emanating from supernovae close enough to us that there would be some of the isotope left after a few million years of traveling through space. What really impressed me was that the ACE researchers had been collecting data for 17 years and during that time they collected all of 15 atoms of 60Fe! This is not even one atom a year! This was out of a total of some 355 thousand atoms of iron collected over those 17 years. The conclusion from finding these few atoms of an iron isotope is that there was a supernova only a few thousand light-years from Earth that sent those iron atoms on their way here a few million years ago. Could some of the iron in my blood have come from that supernova?
Last month marked the death of Muhammad Ali, who might be considered a human supernova. He burst upon the scene in the field of boxing but became so much more than just a boxer. I found it interesting that there was such a tremendous outpouring of sadness and praise for a Muslim at the same time as the controversy over certain statements by one of our presidential candidates. I have a personal remembrance of Ali. Many years ago my wife and I took a Caribbean cruise and we stopped one evening in Puerto Rico to get off the ship to go to a hotel and attend a show. Before the show, we found ourselves standing at an elevator next to Ali. I didn't say anything to him but we saw him again that night at the show, where he was sitting in the front row, just a few feet from the stage. I don't remember any mention or acknowledgment of his presence by the performers. From my vantage point (way back) there was no physical barrier separating him from the stage.
To me, this was an indication of Ali's courage, sitting so close to the stage. Did I mention that the featured act involved a white tiger and two trainers whose identity was unknown to me at the time. It was only later that I realized they were the famed duo of Siegfried and Roy, who specialized in white tigers or lions and their show became a fixture in Las Vegas. Indeed, it was over a decade ago that one of the white tigers mauled Roy, grabbing him by the neck and carrying him offstage. It seems that Roy was suffering a stroke and the tiger may have sensed he was in trouble and was trying to help Roy. Roy did not harbor any ill will against the tiger and the tiger just died a couple years ago. Incidentally, I Googled Siegfried and Roy and Ali together and found a picture of the three of them together in Las Vegas. Could they have met for the first time that evening in Puerto Rico?
Next column, hopefully, on or about August 1.
Allen F. Bortrum
