At last, the Universe is cool enough that we can not only build deuterium, but build up and up the periodic table from there. Add another proton to a deuteron and you get helium-3; add another neutron to a deuteron and you get hydrogen-3, better known as tritium. If you then add a deuteron to either helium-3 or tritium, you get helium-4 out, plus either a proton or neutron, respectively. By time the Universe is 3 minutes and 45 seconds old, practically all of the neutrons have been used to form helium The pathway that protons and neutrons take in the early Universe to form the lightest elements and The nucleon-to-photon ratio determines how much of these elements we will wind up with in our Universe today.
These measurements allow us to know the density of normal matter in the entire Universe very precisely. The big problem is that by this time, the Universe has expanded and cooled enough that its density is only one-billionth the density in the Sun's core. Nuclear fusion cannot occur any longer, and there are no ways to stable fuse either a proton with helium-4 or two helium-4 nuclei. Li-5 and Be-8 are both highly unstable, and decay away after a tiny fraction of a second.
The predicted abundances of helium-4, deuterium, helium-3 and lithium-7 as predicted by Big Bang The first stars in the Universe will be made of this combination of elements; nothing more. The Universe does form elements immediately after the Big Bang, but almost all of what it forms is either hydrogen or helium.
There's a tiny, tiny amount of lithium left over from the Big Bang, since beryllium-7 decays into lithium, but it's less than 1-part-in-a-billion by mass. When the Universe cools down enough that electrons can bind to these nuclei, we'll have our first elements: the ingredients that the very first generations of stars will be made out of. But they won't be made out of the elements we think of as essential to existence, including carbon, nitrogen, oxygen, silicon and more. Instead, it's just hydrogen and helium, to the It took less than four minutes to go from the start of the hot Big Bang to the first stable atomic nuclei, all amidst a bath of hot, dense, expanding-and-cooling radiation.
The cosmic story that would lead to us has, in truth, finally begun. This is a BETA experience. You may opt-out by clicking here. More From Forbes. Nov 11, , am EST. Nov 10, , pm EST. He heard about an experiment by Robert F. Curl and Richard E.
Smalley, both chemists at Rice University at the time, in which they had ablated an aluminum surface and found all kinds of new aluminum molecular clusters. When they substituted graphite a so-called grand-PAH for aluminum, a most bizarre molecule appeared: C 60 , 60 carbon atoms arranged like a soccer ball.
In Kroto, Curl and Smalley were awarded the Nobel Prize in Chemistry for their roles in discovering the molecule, called buckminsterfullerene, or just fullerene also known as a buckyball. Kroto was convinced that buckyballs were present in space and were likely to be the source of some DIB fingerprints. Only a few people believed him, though, and he and his colleagues moved on.
Yet in , a quarter of a century after their initial discovery in the laboratory, C 60 and its cousin C 70 were observed in the infrared in planetary nebula Tc1 in the constellation Cygnus.
Whether these molecules were, in fact, related to the visible-wavelength DIBs was still undecided. Theoretical work suggested so, but scientists lacked confirming experimental data. One, then two lines from this molecule matched known DIB wavelengths. Later, researchers showed that these fingerprints matched four or five DIBs. Then, in , an international team led by Martin A.
This discovery indicates that at least one type of molecule conclusively leaves its fingerprints all over interstellar space. Buckyballs are believed to evolve from PAHs, and their presence in space implies that their parent molecules must also be out there. Yet it was not until that researchers observed the fingerprints of a PAH-family molecule in space.
The compound they saw, benzonitrile C 6 H 5 -CN , is a rare aromatic hydrocarbon that is more easily detected than its relatives.
And even more recently, scientists observed double-ring cyanonaphthalene molecules, revealing that larger PAHs are present as well. The first molecules would have dissipated fairly quickly after the earliest epochs. As the universe matured, expanded and cooled, the leftover hydrogen nuclei began to gather electrons of their own. After that, the helium atoms were largely left alone. Once H 2 had been made, though, the entire tree of chemistry unfolded. Eventually this chain led to water, ethanol and larger species.
No telescopes had the power to separate these signatures. Then along came the Stratospheric Observatory for Infrared Astronomy SOFIA , a repurposed jumbo jet with a hole cut in its side so an infrared telescope can look out. There, in the haystack of far-infrared data within another burned-out cinder of an exploded star in the planetary nebula NGC , part of the constellation Cygnus, was the fingerprint that had gone missing for so long.
This hellish place, with its high temperatures and energies, was not unlike the early universe. Nevertheless, the finding helps to constrain our knowledge of this compound. The discovery might also give us clues about where else this chemical may be lurking in space today, directing us toward other planetary nebulae or even other regions of space that are so far away they correspond to earlier epochs of time, going back to the edge of the universe.
Present observations suggest that the first stars formed from clouds of gas around — million years after the Big Bang.
Heavier atoms such as carbon, oxygen and iron, have since been continuously produced in the hearts of stars and catapulted throughout the universe in spectacular stellar explosions called supernovae. But stars and galaxies do not tell the whole story. Unlike stars and galaxies, dark matter does not emit any light or electromagnetic radiation of any kind, so that we can detect it only through its gravitational effects.
Even less is known about it than dark matter. This idea stems from the observation that all galaxies seems to be receding from each other at an accelerating pace, implying that some invisible extra energy is at work. Planck data can give us a good estimate for the density and radius of the observable universe.
Another variable you need is the fraction of matter that is stored in baryons, which are particles made up of three smaller particles called quarks. The most common baryons by far are protons and neutrons, so Padilla only considers those two in this example. Finally, consider the mass of a proton and a neutron about the same , and you have everything you need to come up with a good estimate for how many particles are in the observable universe.
In essence, Padilla takes the total density of the universe, multiplies it by the fraction of the density that is just baryons protons and neutrons , multiplies that density by the volume of the universe to get the mass of all the baryons, and then he divides that mass by the mass of one bayron to get the total number of baryons in the universe.
But we are not looking for the number of baryons, we are looking for the number of particles. Each baryon is made up of three quarks, which are the particles we are counting. What's more, the total number of protons will equal the total number of electrons, which is the other particle we are counting.
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