Astronomy
esiegel | December 25, 2010"Appreciation is a wonderful thing: it makes what is excellent in others belong to us as well." -Voltaire
All over the world, there are celebrations going on today. Yes, it's Christmas, but there's a much older reason to celebrate. I'm not talking about Roman festivals, Ancient Greek celebrations, or even old Hebrew traditions, although I will give you the David Grisman Quintet's classic,
Shalom Aleichem.I'm talking about the sky. And not the night sky, either. If you want to see what the Sun does, day-from-day, all you need to do is construct a pinhole camera with a photographic plate on the…
esiegel | December 23, 2010"When I had satisfied myself that no star of that kind had ever shone before, I was led into such perplexity by the unbelievability of the thing that I began to doubt the faith of my own eyes." -Tycho Brahe
Supernovae are the most spectacular death-knells of the largest stars in our Universe. Nearly all stars burn light elements into heavier ones, releasing energy through the incredible process of nuclear fusion.
But all stars eventually run out of this fuel. For our Sun, we've got about another 6 billion years left. But the more massive your star, the faster it burns through its fuel.…
esiegel | December 20, 2010"We find them smaller and fainter, in constantly increasing numbers, and we know that we are reaching into space, farther and farther, until, with the faintest nebulae that can be detected with the greatest telescopes, we arrive at the frontier of the known Universe." -Edwin Hubble
There's really only one way to appreciate just how far we've come in our quest to learn about the Universe thanks to the Hubble Space Telescope.
That is, to take a look at something before the Hubble Space Telescope came along, and then to look at it with Hubble. Preferably, we can look at it multiple times, as…
esiegel | December 18, 2010"You cannot propel yourself forward by patting yourself on the back."
-Steve Prefontaine
But there are lots of amazing ways to propel yourself forward, indeed. Listen to one of the greatest musical groups of our times, Béla Fleck and the Flecktones, as they perform Victor Wooten's song,
Sex In A Pan,off their album UFO Tofu.
Last week, I told you about a runaway galaxy, speeding through the Universe and leaving a tail behind it.
Image credit: GALEX.
Of course, this is a composite image in visible and ultra-violet light. We saw here that the galaxy looks normal in visible light; only in the…
esiegel | December 17, 2010"The moon is eclipsed through the interposition of the earth... Anaxagoras was the first to set out distinctly the facts about eclipses and illuminations."
-Euripides, in Hippolytus, 431 B.C.
As we all know, the Earth revolves around the Sun while it rotates on its axis. The rotation causes day-and-night every 24 hours, while the revolution causes our seasons and our calendar year.
You'll notice, in the image above, that the Summer Solstice -- June 21st -- is when the North Pole of the Earth is tilted most directly towards the Sun, and that the Winter Solstice -- December 21st -- is when it'…
esiegel | December 8, 2010"Why it is that of all the billions and billions of strange objects in the Cosmos -- novas, quasars, pulsars, black holes -- you are beyond doubt the strangest?" -Walker Percy
Black holes. You've all heard them before, and you can visualize them pretty easily. How so? Start by thinking about the Earth.
Held together by the immense force of gravity, the Earth is a difficult world to leave.
What exactly do I mean by that?
It takes a tremendous amount of energy to get off of the planet Earth. If you were at the surface of the Earth, you'd have to be moving at around 40,000 km/hr (or 25,000 mi/…
catdynamics | December 7, 2010From Earth to the Universe was a brilliant outreach project for the 2009 International Year of Astronomy, displaying online, and in real life, some of the best astronomical images around.
Now we have the Year of the Solar System coming up, who knew, and more and better images are needed!
From Earth to the Solar System
FETTSS will be an online collection of images that can be freely downloaded and exhibited by organizations worldwide in whatever manner they choose.
In celebration of NASA's Year of the Solar System, the images will showcase the excitement and discoveries of planetary…
esiegel | December 3, 2010"The image is more than an idea. It is a vortex or cluster of fused ideas and is endowed with energy." -Ezra Pound
Back in the 1800s, observational astronomy was already entering its heyday. We had already discovered Uranus, the first planet not visible to the naked eye, knew of a number of comets and asteroids, and had a whole catalog of "bizarre" objects in the sky.
Some turned out to be star clusters, globular clusters, remnants of exploded stars, or other galaxies entirely! But one of the unfortunate things about astronomy around 1800 is that the Southern Hemisphere objects were grossly…
esiegel | December 1, 2010"Keep up the good work, if only for a while, if only for the twinkling of a tiny galaxy." -Wislawa Szymborska
You all know about shooting stars.
Seen from Earth, mostly during meteor showers, these aren't stars at all, but are tiny fragments of rock that hit the Earth's atmosphere, and streak across it, leaving a bright fireball as it burns up. If you're a great (and lucky) astrophotographer, you can nab a picture of one close up as it burns up.
But this principle, that a fast-moving object traveling through space will run into whatever matter is in its way, leads us to some amazing…
krandall | December 1, 2010By Dr. Rosalba Bonaccorsi
Environmental Scientist at the Carl Sagan Center for the Study of Life in the Universe, SETI Institute, and Gail Jacobs
Rosalba, what first sparked your interest in science?
I've always had big dreams -- even as a young girl. As soon as I started to walk, I took an interest in conducting experiments with whatever was available around such as household plants and various chemical compounds. I'm lucky I didn't end up poisoned or otherwise hurt! I remember dismantling alarm clocks. I was so curious!
As a young girl, I was in poor health and as a result spent a lot of…
esiegel | November 30, 2010"It is all a matter of time scale. An event that would be unthinkable in a hundred years may be inevitable in a hundred million." -Carl Sagan
There's some speculation that NASA, later this week, might announce evidence for life on Saturn's moon Titan.
I'm not going to comment on the speculation, but it's worth asking the question, scientifically, "How would the Universe make life, from scratch?"
Let's start by telling you what "scratch" means. If you're familiar with the story of the Universe, one of the things you know is that things were very hot and dense in the past. So hot that you…
esiegel | November 24, 2010"The Sun, with all those planets revolving around it and dependent on it, can still ripen a bunch of grapes as if it had nothing else in the universe to do." -Galileo
So tomorrow is American Thanksgiving, and it's one of our traditions that I'm most happy to take part in. So without any ado, let me give thanks with you.
Thanks not just for the wonderful world we have, with its glorious skies and all the secrets it slowly reveals to us, but for everything that allows us to have the world we have.
Thanks to the atom, with its massive, compact nucleus and its oppositely-charged, much lighter…
esiegel | November 19, 2010"I came at exactly the right time... I was 26 years old, and all the monks and priests down here were ready to retire. So I overlapped enough that I got to know them all." -Allan Sandage
As many of you have heard, Allan Sandage passed away last Saturday. Let me tell you a little bit about this man, why he stands as such a towering figure in modern cosmology, and why he should be held in even higher esteem than he normally is.
Allan Sandage was a coworker of Edwin Hubble's, and he took up one of the most pressing questions of the day after Hubble's death in 1953: What is the Age of the…
esiegel | November 17, 2010"I've been noticing gravity since I was very young." -Cameron Diaz
Yesterday, I told you about one of the simplest arguments for dark matter. We look out at the fluctuations in the microwave background on all the different angular scales we can measure -- from about 0.2 degrees all the way up to the whole sky -- and look at what the temperature fluctuations are doing.
We also look at the large-scale structure in the Universe, and try to correlate how mass clumps together.
We are only allowed -- by the laws of physics -- a few parameters to play with to try to fit this massive data set. We…
esiegel | November 16, 2010"What makes the universe so hard to comprehend is that there's nothing to compare it with." -Anonymous
If I were brand new to theoretical cosmology, I might be skeptical of a whole bunch of "dark" things that I'd heard of. "Dark matter?" "Dark energy?" Come on; you've got to be kidding me! You're telling me that 95% of the Universe is not made of protons, neutrons, and electrons, like all the matter we know?
After all, I look out at the Universe, and this is what I see.
Stars, galaxies, gas and dust... normal matter, all of it. Yet all I need to do is start with two very well-supported…
esiegel | November 5, 2010"I have just gone over my comet computations again, and it is humiliating to perceive how very little more I know than I did seven years ago when I first did this kind of work." -Maria Mitchell, Astronomer
If you were around back in 1997, perhaps you remembered seeing Comet Hartley 2 back then, as it brightened and came close to Earth, as captured by NASA.
Unlike the other comets you know of, like Halley's Comet, Hartley 2 returns close to Earth every 6.5 years, while most comets take nearly a century!
Comet Hartley 2 doesn't look like it originates from the Kuiper Belt. Rather, it looks…
esiegel | November 2, 2010"Every man is free to rise as far as he's able or willing, but the degree to which he thinks determines the degree to which he'll rise." -Ayn Rand
We're all aware that one of the ways that human life on Earth could end, conceivably, is the same way that the dinosaurs went down.
And asteroid tracking and deflection technology is fast becoming one of the hot issues of the day. It appears so often in the news that you'd think we are at a high risk, any day, of being hit by a catastrophic asteroid.
But -- and my opinion here definitely runs against the mainstream -- I think this hysteria is…
esiegel | October 27, 2010"Really, the fundamental, ultimate mystery -- the only thing you need to know to understand the deepest metaphysical secrets -- is this: that for every outside there is an inside and for every inside there is an outside, and although they are different, they go together." -Alan Watts
We've talked, recently, about the scale of the Universe, and trust me, it's huge.
Filled with hundreds of billions of giant, Milky Way-sized galaxies,
each of which contains nearly a trillion stars,
the whole thing is really, really big. And, after nearly 14 billion years of expansion since the big bang, the…
esiegel | October 20, 2010"The laws in this city are clearly racist. All laws are racist. The law of gravity is racist." -Marion Barry
The law of gravity, contrary to what Marion Barry says, is -- perhaps -- the most indiscriminate of all the laws of nature.
What do I mean? Well, you get a large collection of matter and energy together, like in a galaxy, and what does it do? It pulls -- with the entirety of the irresistible force of gravity -- on everything. Give the most massive collections of matter enough time, and they'll pull in everything around them for tens of millions of light years.
And when you do, you'll…
esiegel | October 19, 2010"It is a mistake to look too far ahead. Only one link in the chain of destiny can be handled at a time." -Winston Churchill
And yet, when you look out, you can't help but wonder how far away these points of light in the sky are.
Some things are easy. Our Solar System, for instance. Just by knowing Newton's Laws of gravity and observing the positions of the planets over time, we can determine the distances to any of the planets, our Moon, or our Sun to incredible (better than 99.999%) accuracy.
But what about the stars? They're much, much farther away than anything in our Solar System, and…