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Naming the new ISS module: a suggestion

March 26, 2009 on 2:20 pm | In Solar System | 202 Comments

As many of you have heard, NASA has had a public vote to help name the new node of the International Space Station — node 3 — shown here in its full glory:

Although the name Serenity for the new node got 70% of the vote on the NASA site, that’s totally misleading. Because someone started a write-in campaign to get the module named after himself:

And the name Colbert beat Serenity by over 40,000 votes! Before you shout, “curse you, Colbert” (I already did), I bring up the sad fact that NASA has said the results are not binding, and that this dubiously-qualified megalomaniac may not get his name on the module due to a technicality.

But if NASA had a sense of humor (or any sense of increasing positive publicity), they would listen to my advice:

Name the node COLBERT.

But pronounce it KOHL-burt.

Trust me, he’ll hate it. Loathe it. Perhaps even have someone on his show to throw one of his patented tirades at. Because it won’t be his name, but it completely follows the expressed will of the public. And that, my friends, is the way to make democracy work.

The Most Energetic Mystery in the Universe

March 25, 2009 on 1:05 pm | In Astronomy, Physics, black holes | 29 Comments

When we look out at galaxies, we find the most energetic particles we’ve ever found anywhere in the Universe coming from their centers. Why?

Because as far as we can tell, all galaxies, at their centers, have huge, supermassive black holes! When matter (like a star, globular cluster, intra-galactic gas, etc.) gets too close to one of these black holes, it gets ripped apart, and settles into a disk around the black hole. This disk is called an accretion disk:

Like everything in a strong gravitational field that moves, these particles radiate (give off high-energy photons), fall in towards the center of the black hole, and sometimes get accelerated and shot out of the galaxy!

For a galaxy like ours, with a black hole a few million times as massive as our Sun, we can get extremely energetic particles out: up to 1018 eV, which is 70,000 times more energetic than the LHC!

But our black hole is kind of a commoner — a weakling, even — when you look at other galaxies. There are huge galaxies out there, such as active galaxies and quasars, where instead of a few million times as massive as our Sun, their black holes are billions or even tens of billions times as massive as our Sun:

Well, in theory, the energies of these particles can be thousands or even tens of thousands of times higher than what our galaxy can produce! We’re talking about energies of 1022 eV, which is not only insane, it’s impossible!

Why? Because there’s a maximum energy that particles traveling through the Universe can have. There’s a bath of leftover light from the Big Bang permeating the entire Universe: the CMB. If you smash a particle with too much energy into one of these CMB photons (which is unavoidable as you travel millions of light years), it causes these high-energy particles to slow down until they’re below the “speed limit”. (Okay, it’s an energy limit, but it’s really close enough.)

And unlike cops that pull you over, the light that fills outer space slows you down until you’re below the cosmic energy limit: 5.7 x 1019 eV. Well, do we see a cutoff there?

Maybe. The AGASA experiment says no, there is no cutoff, but the Pierre Auger Observatory says yes, there is one. Who’s right? On one hand, we’ve definitely seen events where we’ve measured more energy than should be allowed. It may mean our theories need revising, or it may mean that there’s something super-energetic happening in our own backyard that we don’t know about. Or — on the other, more boring hand — perhaps we’ve just done a bad job of measuring things at very high energies. Whatever the case, explaining these events that exceed the cosmic energy limit of the Universe is, in fact, the most energetic mystery in the Universe!

A Little Sun in Your Life… Dire Consequences?

March 20, 2009 on 1:18 pm | In Astronomy, Physics | 22 Comments

I really get a kick out of reading The Straight Dope. What started as a weekly column in a Chicago newspaper has grown into a nationwide phenomenon and a small empire, and is often full of fascinating questions and extremely well-researched and knowledgeable answers.

But doesn’t anyone there know to contact me if you’ve got an astrophysics question? Today’s column, which will be nationally syndicated, declares that they cannot answer the following question:

If the pink grapefruit sitting in my fruit bowl spontaneously turned into a grapefruit-sized sun, what would happen to my flat, London, and the rest of the world? If I put it somewhere safe, could I enjoy not paying for central heating? Or would it end life as we know it by melting through my floor, into the African textile shop, through the subway system, and finally to a fiery chasm in the middle of the earth where it would make all volcanoes erupt and kill everything, before coming out the other side and changing the way all the planets spin?

Well, I may be no Cecil Adams, but I can certainly answer this one. Let’s take a look at how our Sun actually works, and then scale it down to be grapefruit-sized.

The Sun is a giant ball of mostly hydrogen gas. It’s extraordinarily massive — about 300,000 times as massive as Earth — and tremendous powerful. The Sun gives off what most people would call an unfathomable amount of energy, but in scientific notation, it’s about 4 x 1026 Watts, which is at least fathomable, although it’s absolutely tremendous. This means that even at the surface of the Earth, 150 million kilometers away, that means we have 129 Watts of solar energy striking us over every square foot that receives sunlight.

But what’s truly exciting, at least for me, is the way the Sun creates its energy. To understand it, we have to go down to the tiniest atomic levels, and look at the hydrogen atoms themselves:

Because the pressure at the center of the Sun is so high, due to the gravitational pressure of having 300,000 Earths pushing in at the core, the nuclei of these hydrogen atoms, protons, get pushed together with a tremendous force. The force is so large that it causes these nuclei to fuse together, in a process called nuclear fusion. With a little math, I can figure out that in order to create the amount of energy the Sun gives off, it has to fuse together about 3.6 x 1038 atoms of hydrogen every second! That little atomic reaction, happening over and over, trillions of times every nanosecond in the Sun’s core, is what produces all the heat, light, and energy we’ve ever received from the Sun.

Now, the person who asked this question wanted to know about having a little stable grapefruit-sized Sun.

Well, here’s a big downer for you: this thing ain’t gonna be stable. If you want to have nuclear fusion going on at the core of this grapefruit-sized ball of hydrogen, you’re going to need a tremendous amount of pressure to push the atoms at the center together. There are only two ways to handle it that we know of, and neither one of them will give you an answer that you’ll like, although they’re both fascinating.

The first way is to artificially increase the pressure, like lasers (shown here) would do. Practically, you wind up getting less energy out than you have to put in to increase the pressure to obtain fusion, which is another disappointment. Scientists working on this call it inertial confinement fusion, and so far, it has never yielded more energy than it took to get it going. So this way looks like a dud. But there’s another way to get nuclear fusion…

You can increase the pressure tremendously — albeit for a very short time — by setting off a small explosion around the hydrogen core, compressing it and causing ignition. There’s a problem with this way, too. The resulting fusion reaction is uncontrolled and runs away, igniting everything. This is commonly known as a hydrogen bomb.

Either way, you give off a tremendous amount of energy, your initial “grapefruit” gets blown apart like a super-powerful exploding grenade, and depending on how much of the hydrogen in there actually managed to fuse would determine what happened. If you scaled down the Sun so that the grapefruit worked on exactly the same scale, you’d only get about 100 million atoms fusing together, or about 100 microJoules of energy. Enough energy to push the hydrogen gas away, but not even enough energy to light a match. But, if you managed to fuse the entire grapefruit into helium, you’d get the energy equivalent of a 160 kiloTonne explosion, or about 11 times the energy of the atomic bomb dropped on Hiroshima, in your fruit bowl.

Without the entire mass of the Sun to insulate this nuclear explosion from the rest of the Solar System, this grapefruit-sized ball isn’t going to last long. Either way, you’re better off getting a heat lamp for your desk, and paying your electric bill.

Book Review: The Hunt for Planet X

March 13, 2009 on 12:49 pm | In Solar System | 14 Comments

Pluto, try as some people may to belittle it, is too beloved to simply go away. Even anti-Plutonians are fascinated by it. So to celebrate the state of Illinois’ very first Pluto Day, since Pluto was discovered exactly 79 years ago today, I present to you a review of Govert Schilling’s newly released book, The Hunt for Planet X: New Worlds and the Fate of Pluto.

This is one of the most detailed books about the Solar System, its history, and the neighborhood at and around our Sun. Schilling starts in the 18th Century, when the Solar System was “well known” with its six planets: Mercury, Venus, Earth, Mars, Jupiter, and Saturn. He tells fascinating versions of the discovery of Uranus, including its naming and its impact on those interested in Astronomy, a great version of the discovery of Neptune, a personal favorite historical story of mine, and spares no detail in telling about the important people and personalities involved.

There’s also a very intricate history given of the asteroid belt, including of a time when the asteroids Ceres, Pallas, and Vesta were all called planets. But the star of this book is no star at all, but the small, icy, distant world, Pluto.

The book talks about Clyde Tombaugh and the discovery of Pluto, omitting practically no detail, and continues to go on about the discovery of its major moon, Charon (and later the theory of its formation), and its two far smaller moons, Nix and Hydra. Throughout this, the reader gets a genuine feeling of the good fortune that goes into such a discovery, as well as the myriad of hours and patience that being a good observational astronomer requires. Amateur astronomers, especially, will find much to identify with in this book, including a kinship with many who share their passion for the heavens.

The last great thing that I really enjoyed about this book was its discussion of the Kuiper Belt and the many objects that have been discovered there so far. It really keeps in perspective that the first Kuiper Belt object other than Pluto and Charon was only discovered in 1992, and yet already, we know that there are many other icy worlds just as important to our Solar System as Pluto:

The book is very well illustrated throughout, with some wonderful pictures in both color and black and white, of the astronomical objects themselves, the astronomers who discovered them, and on special occasions, the actual astronomical data that were used in their discovery.

There are some negatives to this book, and I would be remiss if I didn’t tell you what they are. There is a sense of despair when he discusses theories that didn’t pan out, such as the Nemesis theory (that the Sun has a super-long-period binary companion), the search for a fifth very massive giant planet, and the idea of Vulcan (a planet closer to the Sun than Mercury). This is also not a quick, easy read. Because the book is so dense with details, it often takes quite some time to digest all the information that’s being related. This book could have also used an editor, as every story in the book is given the same weight, whereas many are clearly both more important to the book overall and also are simply more interesting. And this is a personal distaste, but the sheer amount of time and space devoted to the naming of Solar System objects is way out of proportion to their actual importance. Finally, there’s hardly any mention at all of planets around other stars, which would certainly not be out of place in this book.

But to anyone really interested in Pluto and in understanding our Solar System in general, this book contains all the latest, up-to-date scientific information, including on Neptune’s Moon, Triton, and on things as esoteric as what you can learn from an occultation. This book will probably be obsolete when the New Horizons mission gets to Pluto in 2015, but until then, you won’t find a better, more comprehensive source of information that’s accessible to a non-scientist about the Solar System. Overall, to anyone interested in learning about some of the lesser-known worlds in our Solar System and the stories of their discovery, The Hunt For Planet X is for you.

Happy Pluto Day!

Why is Venus the Brightest?

March 11, 2009 on 9:59 am | In Astronomy, Solar System | 31 Comments

Sometimes, when you look up in either the early, pre-dawn morning or early, post-sunset evening sky, there’s one point of light that outshines all the others. It’s usually relatively close to where the Sun was, and unlike most points of light you see in the night sky, this one doesn’t twinkle. I’m talking, of course, about the planet Venus:

Yes, it isn’t nearly as bright as the Moon, but it’s certainly much brighter than everything else you can see. Well, it was only a matter of time before someone wrote in and asked why. Reader Dan asks:

Can you explain why Venus is so bright in the sky right now? I don’t think I have ever seen it so bright in my life.

Venus, as we’ve talked about before, is covered in a very thick layer of greenhouse gases. This makes its surface extremely reflective, so that about 70% of the sunlight that comes in to Venus gets reflected as visible light.

But Venus is also extremely close to Earth. In fact, Venus gets within about 40 million km of Earth, which is less than 1/3 of the distance to the Sun. At its farthest, Venus is about 250 million km from Earth. Why? Because Venus and Earth both orbit the Sun; sometimes they’re on the same side as one another, and sometimes they’re on opposite sides. When they’re both on the same side, Venus has its closest approach to Earth:

But I’m going to force you to think about the geometry of this a little bit. One side of Venus faces the Sun, and gets illuminated; the other one is dark. Imagine that the Earth is far away from Venus. What will the planet Venus then look like from Earth? It will be mostly “full”, and the closer to being in direct opposition to Earth, the more “full” Venus will appear. But the more “full” it appears, the further away it is, and so it should also look smaller. Take a look at these shots of Venus, through the same telescope, when it’s far away from Earth:

When it’s more full, it’s also smaller. But when less of it is illuminated, it’s closer to us. Take a look at what Venus looks like when it’s closest to us:

So when Venus is close to us, it looks like a crescent, but it looks like a very large crescent, and when it’s far from us, it looks like a disc, but a much smaller disc. Which of these two things is more important for the brightness of Venus?

Well, we can find out. You see, Dan is right; Venus is nearly at its brightest right now. Have a pair of binoculars? Well, about 11 days ago, somebody did, and photographed Venus and the Moon together in the sky. Here’s what they saw:

Venus is at its brightest when it’s a crescent! It turns out that being closer to us means everything. Astronomers use magnitudes to measure brightness, and the smaller your number is, the brighter you are. This is useful for stars, where very bright stars are typically 0 or 1 (the very brightest, Sirius, is -1.5), and the dimmest ones visible with the naked eye are 5 or 6.

What about things that aren’t stars, though? Not surprisingly, the Sun is the brightest, at -26.7, and the Full Moon is second, at -12.6. But Venus is third! When Venus is a crescent, it’s -4.6, and when it’s full (but far away), it’s -3.8, which is interesting! Why? Because when it’s full, you can’t see it during the day, even under optimal conditions. But right now, when it’s a crescent, you can! Check out this photograph by John Harper of Venus during the day:

It’s a crescent, just like we said it should be! So that is why Venus is the brightest thing in the sky, and that’s why it’s brighter now than it usually is. Get out your binoculars and have a look! And if you do it tonight, look on the other side of you too, because the Moon is full and it rises at 8:30 PM! Enjoy!

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