Do newer stars in globular clusters die before they get old?

According to theories of star life cycles, when a typical star exhausts its hydrogen fuel, it goes through a set of end-life stages before expiring, expanding and contracting over time. However, a new analysis of a globular cluster orbiting the Milky Way found that the younger generation of stars didn’t seem to reach the later stage of life known as the asymptotic giant branch phase. The astronomers conducting the study discovered this by looking for emission from sodium atoms in stellar atmospheres; since the older generation of stars has far less sodium than the younger generation, its presence is a marker of when a given star formed. None of the asymptotic giant stars in the globular cluster had the expected sodium emission, meaning that something weird was happening.

However, a new observation of one of the Milky Way’s globular clusters turned up a problem: the younger generation of stars in the cluster didn’t seem to be passing through the asymptotic giant phase. Simon W. Campbell and colleagues found that while the red giant star population included stars from both older and younger populations, the asymptotic giant stars only represented the older generation. That’s in strong contradiction to theory: the era of a star’s formation shouldn’t affect its life cycle. The reason for this deviation is mysterious. [Read more…]

The headline to the Ars Technica story, alas, is misleading. There’s no reason to think the younger stars are living longer; in fact, it’s likely those stars are burning out sooner than expected for some unknown reason, unless there’s a way they’ve found to destroy or mask the sodium in their atmospheres.

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Talking about dark matter in a bar

Next Tuesday (June 4, 2013) I will be speaking at SciencePub RVA, a monthly gathering at The Camel in Richmond, Virginia. The doors open at 6 PM, and my talk starts at 7 PM. The event is free, but we’d love it if you would register, so we have an idea of the crowd size. (Also, tip your servers. Seriously. They’re your friends.)

Mining for dark matter

Dark matter makes up about 80% of all the mass in the Universe, but what exactly is it? To see how scientists are trying to answer this question, we’ll examine the evidence for dark matter in the Universe, from the early days of the cosmos to the structure of galaxies. Then, we’ll travel a half-mile underground to the Soudan laboratory in northern Minnesota, where one experiment works to detect dark matter particles directly.

SS Cygni is a special kind of binary system, consisting of a red dwarf star and a white dwarf. According to theoretical models, the white dwarf strips gas from its companion, which leads to periodic outbursts of intense light: a recurrent nova. However, previous observations of the system placed it too far away for those models to work, casting doubt on the theory — a problem for types of systems other than recurrent novas. A new observation using radio telescopes found a much more amenable distance, but led to another problem: why were these two distance measurements so different?

Both used a method known as parallax, a geometrical technique for measuring distances to objects relatively close to the Solar System. The key difference is how the two measurements were calibrated. Parallax doesn’t require knowledge about the emission of light from the object (unlike other distance measurements such as those that use type Ia supernovas), but it still requires reference points. [Read more…]

New distance measurements solve one mystery – and create a new one

Early galaxies: live large, die big, burn bright

How did the biggest galaxies form? Based on the ages of stars inhabiting them, the largest elliptical galaxies — those kind of boring egg-shaped clouds of stars with no pretty spiral arms — formed fairly early in the history of the Universe. While smaller elliptical galaxies likely are the modern version of submillimeter bright galaxies (SBGs), star-forming structures visible from the early cosmos, astronomers have failed to identify the progenitors of the largest galaxies. However, a new paper might have the answer: the authors caught a pair of early galaxies right before they collided, after which they likely merged into one.

Where one galaxy is insufficient, two may do instead. A new set of observations caught two bright elliptical galaxies right before the act of merging into one that would have a combined mass large enough to make the equivalent of 400 billion Suns. Hai Fu and colleagues determined that these galaxies collided more than 10 billion years ago and that the merger was driving extremely rapid star formation, at least ten times the rate seen in ordinary galaxies. Based on these observations, the researchers concluded that such collisions could be responsible for the birth of the largest galaxies, allowing for most of them to finish forming by 9.5 billion years ago. [Read more…]

My cats, Pascal and Harriet, with a few of my books that deal with the topic of relativity.

My cats, Pascal and Harriet, with a few of my books that deal with the topic of relativity.

Albert Einstein is many people’s archetype of the genius scientist, and his most famous equation is E = mc2. Or is it? When you look at Einstein’s published scientific papers over decades of work, he didn’t (usually) write the equation in that form. In fact, he pointed out that was an inaccurate form, since it’s a limiting case of a far more general principle. In my latest piece for Double X Science, I argued that the form of the equation is far less important than its meaning, and it doesn’t really matter if Einstein wrote E = mc2 or not.

When you study relativity, you find those equations are specific forms of more general expressions and concepts. To wit: The energy of a particle is only proportional to its mass if you take the measurement while moving at the same speed as the particle. Physical quantities in relativity are measured relative to their state of motion – hence the name. [Read more…]

Did Einstein ever write his most famous equation?

The real poop on human digestion

I won’t lie: I love Mary Roach‘s books. She is likely the funniest nonfiction writer working today; her beat is the weird side of science. I reviewed her most recent book, Gulp: Adventures on the Alimentary Canal, for Double X Science:

Consider this question a 6-year-old might ask: Why doesn’t the stomach digest itself? After all, the human stomach contains hydrochloric acid, which is uses to break down some pretty tough substances for digestion. The answer, as Roach points out, is that it does: The acid dissolves the lining of the stomach over the course of a few days, but new cells replace the destroyed ones. When a person dies, no new cells are born, leaving the acid to work undeterred…with predictably gross results.

However, Gulp isn’t a gross-out book, though I don’t advise you read the chapter on coprophagia (poop-eating) during lunch, as I did. [Read more…]

Was the Big Bang actually the beginning?

The big question is what's inside the box? Is it the mushroom of true knowledge that makes us grow? Or is it a coin of incremental data that buys us a little more time before the goomba of unknowability stops our exploration?

The big question is what’s inside the box? Is it the mushroom of true knowledge that makes us grow? Or is it a coin of incremental data that buys us a little more time before the Goombah of unknowability stops our exploration?

I usually avoid the kinds of sexy big questions that often make cosmology books by Paul Davies or Stephen Hawking or Roger Penrose popular. The main reason for that is because those big questions may not be answerable, because they are beyond the reach of our telescopes or experiments. One such question—what, if anything, came before the Big Bang?—is cause for a great deal of speculation, and a good amount of nonsense. If memory serves, Pope John Paul II was the first pontiff to explicitly accept Big Bang cosmology, but he also forbade Catholic cosmologists from even pondering the question of whether anything came before.

However, BBC Future provided me a great opportunity to examine the meta-question: “Will we ever know what happened before the Big Bang?” That’s a question better suited to me: it’s not speculation, but pondering how can we know? And the answer isn’t clear:

First of all, the language we use to describe what we know and don’t know can sometimes be muddy. For instance, the Universe may be defined as all that exists in a physical sense, but we can only observe part of that. Nobody sensible thinks the observable Universe is all there is, though. Galaxies in every direction seem similar to each other; there’s no evident special direction in space, meaning that the Universe doesn’t have an edge (or a centre). In other words, if we were to instantaneously relocate to a galaxy far, far away, we’d see a cosmos very similar to the one we observe from Earth, and it would have an effective radius of 46 billion light-years. We can’t see beyond that radius, wherever we’re located. [Read more…]

Thanks again to Simon Frantz, my editor at BBC Future, who asked me to write the piece and helped turn it into something coherent, instead of Grumpy Matthew grumbling into his coffee.