StartsWithABang writes: Beyond hydrogen and helium, every atom of every element we have on Earth was made in a star, processed in space and then finally condensed to form our world some 4.5 billion years ago. All the elements of the periodic table up through Uranium are found on our world, except one: technetium, element 43. But technetium is found in (some) stars, thanks to an amazing reaction: the s-process.
StartsWithABang writes: The Big Bang was the birth of all the matter and radiation in the Universe, and signifies the beginning of what we know as all of existence. Yet it didn't happen an infinite or even an indeterminate amount of time ago: it happened precisely 13.81 billion years ago, with an uncertainty of just 120 million years. But despite all of our observations and data about the Universe, there are just two independent lines of evidence that lead us to that conclusion. At least they agree!
StartsWithABang writes: Those constant, fixed points of light in the night sky — the stars — turn out not to be so constant if you looked with great precision at them. A star like our Sun varies in brightness, periodically, by about 0.1% over the span of a few years, but many stars vary by 99% or more from brightest to dimmest. For centuries, we knew of only a handful of these objects, yet now they’re known to be commonplace. Here's what causes their behavior and underlies it, along with the story of their discovery.
StartsWithABang writes: Everywhere we look in the Universe, we find more Universe that looks an awful lot like we do, with planets, stars, galaxies, groups and clusters similar to our own. Yet the Universe we see isn't all of what's out there, with normal matter (or any of the Standard Model particles) unable to explain even a simple majority of what we observe. Instead, we require five times as much dark matter to explain the mass we see, with at least seven independent lines of evidence supporting that inescapable conclusion.
StartsWithABang writes: When it comes to dark matter, the mysterious substance that makes up the vast majority of the mass in the Universe, there's a whole lot we don't understand or know about it. You might think that there are so many unknowns that are so huge that — quite reasonably — perhaps it doesn't exist at all, and there's some other explanation for the behavior of masses on galactic scales and up? And yet, you can't make that leap unless you've honestly (and scientifically) considered the full suite of evidence and facts that speak to the question of dark matter's existence. When you do, you find that there's no doubt: it's real, and it's spectacular.
StartsWithABang writes: Most mental images of galaxies invoke thoughts of two giant arms, spiraling out from the center and wrapping around, covered richly in stars. Yet this picture, though incredibly common, represents only about 10% of galaxies. Moreover, the galaxies that do have two grand, spiral arms won't have them for very long, as the classic picture we have of spirals represents only an intermediate stage in galaxy evolution.
StartsWithABang writes: The Andromeda galaxy is our closest large neighbor, dominating our local group with more than double the number of stars found in the Milky Way. While visible light can reveal a tremendous amount of information, it's by going to shorter (UV) and longer (IR) wavelengths that we can learn where the newest, hottest stars are, find that they form in clusters along the arms and in the center, see through the (visible) light-blocking dust, and pinpoint the location of the neutral gas that will form the next generation of stars.
StartsWithABang writes: When Giovanni Cassini discovered Saturn's moon Iapetus in 1671, he was puzzled to find that it was easily visible on the western side of the planet, but unable to be seen along the eastern side. Only 34 years later did he find it on the east side, finding it two full magnitudes dimmer. His theory was that Iapetus was locked to Saturn, and that it had one light hemisphere and one dark one. It took another 300 years, but now we finally know what caused this two-toned world: a captured Kuiper belt object is to blame!
StartsWithABang writes: While the stars exist in tremendous numbers (some 10^23+ in our observable Universe) and great varieties, every star that ever has shone or will shine will someday run out of fuel and die. When that happens, the inner core of the star contracts down to form a tiny, degenerate but very hot object. But even so, no object with a finite amount of energy can shine forever. At some point, even those stellar remnants will cool down out of the visible portion of the spectrum. But how long will that take, how will that happen, and has the Universe been around long enough (yet) so that such an object exists? Answers here.
StartsWithABang writes: Earlier today, NASA announced the most Earth-like exoplanet yet, a planet just 60% larger in radius than our own, orbiting a star of the same spectral class as our Sun and with an almost identical orbital period: 385 days. But is this really the most Earth-like planet we’ve discovered? It’s significantly larger and five times as massive, and may actually be more like Neptune than like Earth. In fact, other properties may be much more important if we truly want to find a “twin” to Earth: a rocky planet teeming with advanced chemical-based life.
StartsWithABang writes: Over 100 years ago, Rutherford's gold foil experiment discovered the atomic nucleus. At higher energies, we can split that nucleus apart into protons and neutrons, and at still higher ones, into individual quarks and gluons. But these quarks and gluons can combine in amazing ways: not just into mesons and baryons, but into exotic states like tetraquarks, pentaquarks and even glueballs. As the LHC brings these states from theory to reality, here's what we're poised to learn, and probe, by pushing the limits of quantum chromodynamics.
StartsWithABang writes: It's paradoxical how our eyes work: we adjust to the brightness of everything around us. A modestly illuminated night sky will leave just a few dozen stars and planets visible, while if you take that light pollution away, thousands of stars, the Milky Way and even galaxies can be seen with the naked eye alone. Perhaps surprisingly, there's a country out there with high mountains, dark skies, and great seeing that values astronomy: Chile. A great report from astrophysicist Brian Koberlein as he forays into observational astronomy and voyages to Chile to find out firsthand!
StartsWithABang writes: If it's weren't for our atmosphere at all, the average temperature on Earth's surface would be a paltry 255 kelvin (-18 C / 0 F), so the greenhouse effect does plenty of good by warming us an additional 33 C (59 F) on average. But over timescales of hundreds of millions of years, the Sun's energy output increases as its core temperature — and the rate of fusion — heats up. In one-to-two billion years, the Earth's oceans will boil, ending life as we know it on our world. Perhaps we're very lucky life evolved as fast as it did on Earth; a little slower and intelligent life may never have had a chance.
StartsWithABang writes: In the solar system, everything orbits the Sun: planets, asteroids, kuiper belt objects and more. That is, unless an object is in orbit around one of those, like a moon or a satellite object. Is it possible, then, for a moon or satellite to have another level: an object that orbits it, in turn? While we presently haven't discovered any in our Solar System, it is theoretically possible, with numerous candidates already identified for where to look for such objects.
StartsWithABang writes: Our Sun, like all stars, spends most of its life burning hydrogen into helium, placing it on the main sequence. When we run out of fuel, we'll start fusing helium into carbon, a process that still takes a long time, but not nearly as long as hydrogen burning. In the most massive stars, this will be followed by phases of carbon burning, oxygen burning, silicon burning and more. Yet even as there are more phases to undergo, these phases take increasingly shorter amounts of time, and a star running out of fuel literally sees its life end in the blink of an eye.