Tag: Universe

Bad Astronomy review: Terra Nova

By Phil Plait | October 17, 2011 6:30 am

So I finally watched the pilot episodes of the new Fox scifi drama "Terra Nova" (it airs Mondays at 8:00 p.m. ET). I found it watchable, with some potential, and like every other TV show in existence (except "Firefly") it had some things I liked and some I didn’t. I got email about it due to a couple of lines in the pilot, which I’ll get to in a sec. First, a quick overview.

Gotta get back in time

The idea behind the show (no real spoilers here, since this is all explained in the first minute of the program) is that by the year 2149, the Earth is dying. Pollution, global warming, and so on have made the planet nearly uninhabitable. People need rebreathers just to go outside, and many scenes show huge chimneys pumping smoke into the air just to hammer home that point. Population control is mandatory; having more than two kids is an invitation for the police to come.

The show centers on a family – cop father, brilliant doctor mother, rebellious teenage son, science whiz-kid teenage daughter, and their youngest, a girl. And yeah, if you count three kids, good for you! That drives part of the plot in Part 1 of the show, so I won’t spoil it.

The big plot device in the show is that a fracture in time is discovered — how and why are not disclosed, perhaps to be revealed in a later episode — that goes to 85 million years in the past. People are being sent back in time to populate the still-clean planet, save humanity, fight dinosaurs, and so on.

I’ll note that I like how the time travel was handled. When we join the story, time travel has already been around a while — this family is sent back as part of the tenth wave of colonists — so the writers didn’t have to spend a lot of time talking about how it was done. It just is. Also, the writers circumvented the inevitable fan rage with a short expository scene stating how this isn’t really our past; the time line has split, so it doesn’t matter if you step on a butterfly or eat an entire herd of dinosaurs. It won’t change the future. That made me smile. Score one (pre-emptively) for the writers.

Of course, the show tried to distance itself from "Jurassic Park", and did so by having the first look at the dinosaurs be a herd of brachiosaurs, and then having the main characters in souped-up jeeps getting chased by a carnivorous velociraptor/T-Rex-like animal.

Um, yeah. Oops.

I’m no paleontologist, and I like watching dinosaurs with big sharp teeth eat a person as much as the next guy, so that part was fine. But then they went a little bit out of their way to add some astronomy, and kinda blew it. So I have to jump in here a bit.

What follows is me nitpicking the science of a couple of lines of dialogue. I don’t do this to be petty — I gave up on that in my reviews a long time ago — but just to use these lines to point out the real science. Any snarking is incidental.

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Astronomers have found when and how the cosmic fog was lifted

By Phil Plait | October 13, 2011 10:13 am

Take a look at the image displayed here [click to redshiftenate]. Every object you see there is a galaxy, a collection of billions of stars. See that one smack dab in the middle, the little red dot? The light we see from that galaxy traveled for 12.9 billion years before reaching the ESO’s Very Large Telescope in Chile. And when astronomers analyzed the light from it, and from a handful of other, similarly distant galaxies, they were able to pin down the timing of a pivotal event in the early Universe: when the cosmic fog cleared, and the Universe became transparent.

This event is called reionization, when radiation pouring out of very young galaxies flooded the Universe and stripped electrons off of their parent hydrogen atoms. An atom like this is said to be ionized. Before this time, the hydrogen gas was neutral: every proton had an electron around it. After this: zap. Ionized. This moment for the Universe was important because it changed how light flowed through space, which affects how we see it. The critical finding here is that reionization happened about 13 billion years ago, and took less time than previously thought, about 200 million years. Not only that, the culprit behind reionization may have been found: massive stars.

OK, those are the bullet points. Now let me explain in a little more detail.

Young, hot, dense, and chaotic

Imagine the Universe as it was 13.7 billion years ago. A thick, dense soup of matter permeates space, formed in the first three minutes after the Big Bang. The Universe was expanding, too, and cooling: as it got bigger, it got less dense, so the temperature dropped. During this time, electrons and protons were whizzing around on their own. Any time an electron would try to bond with a proton to form a neutral hydrogen atom, a high-energy photon (a particle of light) would come along and knock it loose again.

During this period, the Universe was opaque. Electrons are really good at absorbing photons, so light wouldn’t get far before being sucked up by an electron. But over time, things changed. All those photons lost energy as things cooled. Eventually, they didn’t have enough energy to prevent electrons combining with protons, so once an electron got together with a proton they stuck together. Neutral hydrogen became stable. This happened all over the Universe pretty much at the same time, and is called recombination. It occurred about 376,000 years after the Big Bang.

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CATEGORIZED UNDER: Astronomy, Cool stuff

Another record breaker: ultra-deep image reveals ultra-distant galaxy

By Phil Plait | January 26, 2011 11:03 am

Astronomers have just announced they have discovered what may be the most distant galaxy ever seen, smashing the previous record holder. This galaxy is at a mind-crushing distance of 13.2 billion light years from Earth, making it not just the most distant galaxy but also the most distant extant object ever detected!

Here is the object in question:

The small box shows the location of the galaxy, which is invisible by eye in the image. The zoomed region shows it in the infrared, where it glows more strongly.

[NOTE: Let me be clear up front and say that this is a candidate galaxy, since it hasn't been confirmed using other distance determination methods. However, having read the paper I think the astronomers did an excellent job showing this is very likely to be a galaxy 13.2 giga-light years away. From here on out I'll refer to it as if it's real, but to be fair bear in mind there is some small chance it may turn out not to be real.]

Named UDFj-39546284, the galaxy is seen as it was just 480 million years after the Universe itself formed! The previous record holder — which was announced just last October — was 13.1 billion light years away. This new galaxy beats that by 120 million light years, a substantial amount. Mind you, these galaxies formed not long after the Big Bang, which happened 13.73 billion years ago. We think the very first galaxies started forming 200 – 300 million years after the Bang; if that’s correct then we won’t see any galaxies more than about 13.5 billion light years away. Going from 13.1 to 13.2 billion light years represents a big jump closer to that ultimate limit!

The galaxy was found in the infrared Hubble Ultra Deep Field, or HUDF, an incredible observation where Hubble pointed at one patch of sky and stared at it for 173,000 seconds: 48 solid hours! After Hubble’s Wide Field Camera 3 observed it, this supposedly blank patch of sky came alive with thousands upon thousands of distant galaxies, and in fact the last record-breaking galaxy was found in the image. The picture here shows the whole HUDF image, with the first picture at the top of this post outlined. Click it to see it in full size, and you’ll start to get an appreciation of just how freaking tough these observations are. The sky is full of faint galaxies!

This new discovery was found using what’s called the dropout technique. Read More

CATEGORIZED UNDER: Astronomy, Cool stuff

How deep the Universe

By Phil Plait | January 17, 2011 11:07 am

The Universe is a big place.

I mean, really big. Big enough for anything. Literally, big enough for everything. Everything you see, everywhere you go, it’s all inside. And there’s room for all of it, with space to spare. I get used to it sometimes, and then, suddenly, I’m thrown into a state where I’m forced to remember just how much of the Universe there is.

Let me show you something:

[Click to galactinate, and while it may take a little while to download the entire 3500 x 2000 pixel image, it will definitely be worth your time.]

This is the nearby spiral galaxy NGC 1345 as seen by Hubble. Lovely, isn’t it? You wouldn’t even think it’s a spiral at first; the arms are so faint compared to the sprawling core and inner regions. But it so happens the galaxy is close to our own, making fainter parts easier to observe.

Now there you go. Did you see that? What I said? "The nearby spiral…". "The galaxy is close to our own…". But it isn’t.

Look. Let your eyes move to the top of the galaxy, just to the right of center. See that bright star? You can tell it’s a star because it has those spikes going through it, an artifact of how point sources are seen by some of the Hubble cameras. Given how bright it is, that star is almost certainly in our own galaxy, and not some luminous giant in NGC 1345; it’s just coincidentally superposed on the more distant galaxy. That means it’s no more than a few thousand light years away, and given its deep red color, that means it’s most likely a very cool and faint red dwarf, and therefore in all likelihood much closer even than that.

But even if it’s only a thousand light years away, that’s 10 quadrillion kilometers! That distance is impossible to imagine: it’s more than 60 million times farther away than the Sun… and the Sun is hardly close. If you could fly an airplane to the Sun, it would take 20 years. Twenty years! And that star is millions of times farther away.

… and that star is the closest thing in that picture. I said NGC 1345 is nearby, and on a cosmic scale it is; it’s part of a small cluster of galaxies a mere 85 million light years away: 850 quintillion kilometers. That’s 850,000,000,000,000,000,000 kilometers.


But now let your eyes roam over the image. You can see dozens of smaller galaxies crowding the frame. Those are background galaxies much, much farther away than NGC 1345. I’ve extracted three of them here. Each looks to be a spiral galaxy — the one on the upper right is edge-on, but the tell-tale dark dust lane across its middle is a dead giveaway that it’s a disk galaxy — and although the distances aren’t known, it’s safe to bet they are hundreds of millions of light years away. Maybe more. In my time on Hubble we’d routinely see background galaxies that were well over a billion light years away. Routinely. Mind you, each of these background objects is itself an entire galaxy, containing tens or hundreds of billion of stars, perhaps as big, rich, and diverse as our own Milky Way.

And in the course of things, this was a short exposure for Hubble, just a little over half an hour. I once worked on a Hubble image that had an exposure that lasted for days, and we saw objects so faint that the faintest star you can see with your naked eye would be ten billion times brighter. These objects were essentially as far away as anything we possibly can see.

And yet the Universe is deeper even than that. It stretches on and on… and while it’s finite — it has an actual size — in practical terms it’s infinite. Why? Because it’s expanding. If you could somehow hitch a ride on a photon, the fastest thing in the cosmos, you’d still never reach the edge of the Universe even if it had one. That’s because the edge would be receding away from you faster than you could reach it. You’d forever be playing catch-up. Literally, forever.

I sometimes think it’s fantastic that we can see anything at all when we gaze upwards. And yet, there it is. Splayed out for us to study, for us to explore.

Some people feel small, insignificant, when they look out into all that space, all that blackness. It’s easy to feel that way, but it’s not a fair assessment. It can be a struggle, and a mighty one, but it’s worth the effort to seek out the awe and the grandeur in it as well. In all that vastness, all that depth, it’s entirely possible there are trillions of planets like Earth, and maybe more. But none is this Earth. Nowhere else is there another you, another me.

In the end, when you make that effort, this is one of most important lessons you learn: we’re a part of all this. A unique part. And that’s a fine thing to know.

Image credit: ESA/Hubble & NASA

Galaxy cluster at the edge of the Universe

By Phil Plait | May 10, 2010 9:57 am

Astronomers have found the most distant galaxy cluster ever seen: the sexily-named SXDF-XCLJ0218-0510.

First, the picture, then the words:


Yikes! What’s all that then?

Okay, first, this picture is littered with stars and galaxies. The galaxies are so far away they’re hard to distinguish from the stars! The dots that have arrows pointing to them are the galaxies that are most likely part of the cluster. The ones with circles have had their distance measured and are known to be part of the cluster for sure. The contour lines represent the detection of very hot gas, which is a dead giveaway that we’re dealing with a cluster here; all big clusters have gas swirling around them that gives off X-rays; the lines are like a topographic map telling you where the (otherwise invisible) gas is in the picture.

"So what?", you might say. We’ve seen lots of clusters before. Ah, but this one is different: it’s a whopping 9.6 billion light years away.

Billion. With a B.
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CATEGORIZED UNDER: Astronomy, Pretty pictures, Science

From here to infinity… logarithmically

By Phil Plait | January 11, 2010 12:00 pm

Logarithms are cool. Sure, some of you may have flashbacks to middle school and may collapse on the floor twitching upon their mere mention, but seriously, logs are the language of the Universe. Our senses (eyesight and hearing) are sensitive logarithmically, and a lot of ways the world behaves make a lot more sense when you plot them using logs.

For those of you scratching your heads, a simple way to think of logs is to think factors of ten. Instead of counting like we normally do — 1, 2, 3, 4 and so on — in log space you count by factors of 10: 1, 10, 100, 1000, and so on. There are lots of advantages to this, one being that you can make graphs that show things that are very small and very big on the same plot. Using regular numbers, it would be hard to make a graph showing the size of a human (2 meters tall) and a skyscraper (200 meters tall) on the same plot, but using logarithms, they are only two ticks apart in size. Easy peasy.

And if you take this idea to the extreme, what do you get? Why, you could get a plot of the whole freaking Universe, from the surface of the Earth out to the fires of the Big Bang itself!

But who would do such a thing? Astronomers at Princeton, that’s who.


[Click to exponentiate.]

That picture is just a small piece of a much larger graphic showing, well, everything. At the bottom is the Earth and at the top is the most distant thing we can see: the cosmic microwave background, the cooling fireball from the Big Bang. Included are planets, asteroids, stars, galaxies, and pretty much everything you can think of, all plotted out for your perusal. The vertical axis represents distance, and the horizontal is cleverly done in Right Ascension, sorta like longitude (East/West) on the sky. That way they get the whole sky — the whole Universe — on one graph.

I know xkcd did something like this, but I’d love to see this done up as a vastly scrollable webpage with actual images instead of dots, and the objects actually described (rollovers, popups, links, whatever). If done correctly, that would cause a wave of nerdgasms across the web, and not-so-incidentally be an awesome learning tool. Any takers?

Tip o’ the order of magnitude to Stuart at @astronomyblog.

CATEGORIZED UNDER: Astronomy, Cool stuff, Pretty pictures

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