Astronomers Deal With Outrageous Phenomena
Even for scientists accustomed to big things, some observations seem too outrageous to explain.
Astronomers report most ‘outrageously’ luminous galaxies ever observed (Science Daily). Just how outrageous are the new observations of superluminous galaxies?
Astronomers at the University of Massachusetts Amherst report that they have observed the most luminous galaxies ever seen in the Universe, objects so bright that established descriptors such as “ultra-” and “hyper-luminous” used to describe previously brightest known galaxies don’t even come close. Lead author and undergraduate Kevin Harrington says, “We’ve taken to calling them ‘outrageously luminous’ among ourselves, because there is no scientific term to apply.”
Previous luminous galaxies were dubbed “ultra-luminous” if they were estimated to have a trillion times the luminosity of the sun. What do you call something that has 100 trillion? That’s what they found from a mountaintop observatory in Mexico and verified with two orbiting telescopes.
Yun adds, “The galaxies we found were not predicted by theory to exist; they’re too big and too bright, so no one really looked for them before.” Discovering them will help astronomers understand more about the early Universe. “Knowing that they really do exist and how much they have grown in the first 4 billion years since the Big Bang helps us estimate how much material was there for them to work with. Their existence teaches us about the process of collecting matter and of galaxy formation. They suggest that this process is more complex than many people thought.“
Some of the brightness may be an artifact of gravitational lensing, the article goes on to say. But something outrageous is happening at the objects themselves. “We still don’t know how many tens to hundreds of solar masses of gas can be converted into stars so efficiently in these objects, and studying these objects might help us to find out.”
Heavy Thoughts About Heavy Elements
Current theory about supernova explosions can only account for the creation of some elements in the periodic table. “But there’s a hole in our understanding,” states an article about this on PhysOrg. Heavier elements (gold, platinum, uranium and others) require a theoretical process called the rapid neutron-capture process (r-process). According to this model, heavy elements get built up rapidly from lighter seed nuclei.
It takes an exotic set of circumstances to get the r-process working, because it requires the infusion of large numbers of neutrons. The article describes how neutron stars first have to form with the seed nuclei. Then, if two neutron stars merge, the resulting supernova should be able to reach the required energy levels. How often does this scenario take place?
During the formation of a neutron star, a large amount of neutrons is released. If two of these neutron stars happen to be orbiting each other, they will eventually merge to form one giant neutron star. During that explosion neutrons are released and r-process elements can form.
A dwarf galaxy named Reticulum II appears to have an abundance of heavy elements. The astronomers interviewed in the article assume that those elements were formed from such scenarios. This would have happened 12 billion years ago, not long after the big bang, they assume.
What this means is that a single rare event produced a rather large amount of this r-process material. All those elements were then incorporated into the surrounding gas and from there into the next generations of stars. It is those stars that we can still observe today.
Since the merger of two neutron stars implies previous generations of stars, the astronomer did not predict finding these heavy elements so far back in time. In fact, when Alex Ji detected them, he thought he had messed up the observations. “During the hour-long discussions that followed, I kept observing more stars while carrying out preliminary analyses of the data at hand to ensure that this was a real signal,” he remarked.
How Did Heavy Elements Get to Earth’s Surface?
Why do we see flakes of palladium, platinum and other heavy elements on the surface of the Earth? It’s been presumed that geological processes dredge them up from the interior (assuming these first originated from the rare neutron-star mergers). Imagine the surprise when scientists found that bacteria have a lot to do with it. PhysOrg quotes Frank Reith from the University of Adelaide:
“Traditionally it was thought that these platinum group metals only formed under high pressure and temperature systems deep underground, and that when they were brought to the surface through weathering and uplift, they just sat there and nothing further happened to them,” says Dr Reith.
“We’ve shown that that is far from the case. We’ve linked specialised bacterial communities, found in biofilms on the grains of platinum group minerals at three separate locations around the world, with the dispersion and re-concentration of these elements in surface environments.
In short, “nuggets of platinum and related metals can be reformed at the surface through bacterial processes,” the scientists found. Reith adds,
“We’ve shown the biofilms occur across a range of platinum-group-metal grains and in different locations,” says Dr Reith. “And we’ve shown, that at the Brazil site at least, the entire process of formation of platinum and palladium was mediated by microbes.“
There is so much that scientists still do not understand, it behooves them to learn humility. The three more infamous words in science reports are: “now we know.”