Brown Dwarves

I always feel like saying that is a slur, somehow...anyway, short post tonight (heading towards finals...who thought it was a good idea to hold regular exams a week before finals? Just cover the material in the final!) on brown dwarves.*

Brown dwarves are small objects that fill the rather broad size gap between planets and stars. Essentially failed stars, they start at around 12-15 Jupiter masses and go up to...well, the size of ignition, about 10% of the Sun's mass.

What's a failed star? It's an object that started collecting gas from a nebula (hydrogen, some helium maybe), and may even have created a disk of swirling material. Unfortunately, for whatever reason, it ran out of gas to accumulate. This means that its total mass was insufficient to crush the hydrogen atoms at its core into each other -- creating helium through nuclear fusion, and consequently kick-starting its life as a star. Instead, it just sits there like a largish ball of matter, quietly wiling away time.

Ok, that's why they're not stars, but what differentiates brown dwarves from rogue planets? Well, dwarves, ironically, are just too big. There are a few other differences, although if you look too closely, you'll find that astronomers are still a little fuzzy on the details.

Firstly, their pseudo-stellar-disk method of formation is similar to that of a star, not a typical planet. Many rogue planets are presumed to have been slingshot from an unstable orbit around a multi-star system. Not so with brown dwarves.

Secondly, they are hot gaseous bodies; most of our planets, and the other planets we've found outside our own solar system, are either terrestrial (can be hot or cold) or Jovian, which are typically cold. This is related to where they form: terrestrial bodies form closer to the star, with less chance of capturing or holding onto gases; gas giants form outside the "frost line," where most gases condense to liquids or ices.** Contrary to this, brown dwarves do not give off much light in the visible spectrum, if any, but they emit a good deal in the infrared (IR) spectrum. Compare the images from Jupiter in the IR spectrum here and an image of a brown dwarf binary system here.Other images are more dramatic, but clearly even from a far greater distance, the brown dwarves give off a great deal more infrared radiation.
 
Thirdly, planets differentiate if they're made out of more than one element (go look up diamond exoplanets, pretty awesome). Heavy metals like iron and nickel sink to the core, and lighter elements rise to the surface or atmosphere. Brown dwarves are just a ball of mush. Its gases may have been there since formation, or a small amount of hydrogen fusion may have occurred early in life; physicists are still arguing over the parameters.

So, brown dwarves. They're hard to detect and they make the border fuzzy between what seemed previously to be pretty nailed-down definitions. They aren't stars, and they aren't habitable. We can't quite seem to figure out what they're for, in the grand scheme of things. If I figure it out, I'll let you all know.




*Yes, dwarves; I hate American spelling.
**There are "hot Jupiters" being found by recent exoplanet searches, but the term is relative; they're still quite cold, and they are believed to have migrated inward towards their star from their original orbit outside the frost line.

Can You See Me Now?

I've mentioned this before, but one of the things that I find the most amazing about space is the vastness. To quote the Hitchhiker's Guide to the Galaxy (I often do), "Space is big. Really big. You just won't believe how vastly, hugely, mind-bogglingly big it is." It's very true. The more you think about the distances and time frames involved in properly studying the Universe, the more immense and incalculable it seems.

This bothers a lot of people, in much the same way as looking down from a height does. I'm going to take advantage of this opportunity to evoke the sensation in you, readers. Thinking that it takes 25,000 miles to go once around our planet's equator seems like a fairly large distance, right? It's a little over twice as far as the average person commutes to work in a year (my own calculations, based on Census data -- see bottom of page for how I got it). Then you think that you'd have to drive 9.5 times the Earth's circumference to get to our nearest neighbor, the Moon. To drive to Mars at the same speed, you would have to cover 3000 times the distance of your annual commute, or 1440 Earth circumferences. All that, and we haven't even left the inner solar system yet, much less looked at other stars.

It just gets more staggering from there; beyond our solar system are widely-spaced stars, beyond our local stars are the far-flung arms of our galaxy, beyond our galaxy are distant other galaxies in the Local Group, beyond the Local Group are other chains of galaxies spreading out into the Universe, at distances where even the light of billions of suns are a faint smudge in our telescopes. Just outside the (suddenly tiny) confines of our atmosphere is a vast, black stretch of...almost nothing...for distances that still take our most modern propulsion systems months to travel to.

And that's just space; don't look at time scales unless you want to feel real cosmic vertigo.

I find this all oddly comforting. There's something intensely personal about the fact that, in all this vastness, there is one tiny rock around one totally average star that is just right for our form of life to develop. Then there's all the other rocks out there that could support the same type of life. And all the ones that could have other kinds of life that we wouldn't even recognize. It doesn't matter how you think this Universe started, scientific or otherwise -- anyone who can think about these things and not get totally awestruck is missing out on one of the biggest beauties we know.

So I want to share some of the things that help make the Universe a warmer, fuzzier place to think about again:

1. SETI (http://www.seti.org/): de-funded by the government after less than a year's actual operation, the Search for ExtraTerrestrial Intelligence has not been idle. Looking for signals from other planets, the now-private group uses its own radio telescopes (or gets time on other telescopes pointing in likely directions) and gathers data. The head scientist, Seth Shostak, recently claimed that SETI was likely to find an alien signal within the next 25 years . You can even help them sort through it by running a SETI@home program while your computer is idling.
2. The Drake Equation: this equation applies to our galaxy, or any other galaxy with at least one civilization. It basically summarizes all of intelligent-life astrobiology. Made up of about 7 terms (depending upon which version you use), it tells you just how likely it is to find intelligent life advanced enough to be broadcasting signals into space in your galactic vicinity at the present time. The trick is that we don't have exact numbers for most of the terms, but the upshot is that all but the most conservative estimates turn up at least a few alien civilizations in our galaxy. A good introduction to the nitty-gritty of the equation can be found here (http://www.pbs.org/wgbh/nova/space/drake-equation.html).
3. Hubble Image Gallery (http://hubblesite.org/gallery/): This might seem counter-intuitive, but there's just something about seeing these beautiful, colorful pictures that makes the Universe look like a friendlier place.
4. Things Close to Home (http://www.nasa.gov/mission_pages/cassini/main/index.html and http://mars.jpl.nasa.gov/msl/): if you're feeling a little...a-claustrophobic still, take a gander at some of the neighborhood scenery. NASA's Cassini-Huygens and Curiosity missions are returning routinely gorgeous pictures of planets that are within our reach, our cosmic siblings. Cassini is focusing on Saturn and its moons (some of which are prime local candidates for life), and Curiosity is, of course, on Mars. Check out especially the skyline pictures from Curiosity, and think about how those things that look like low hills are mountains up to 5 miles high!

*Fun Census calculations: I used the 2011 ACS numbers for average commute time for the entire US. (while I have your ear, the American Community Survey recently had its funding axed in Congress; this seriously erodes the information we have about the state of our nation's populace. Go read about about the fight, it was all over major media sources.) This number was 25.3 minutes. I assumed 55 mph as a median driving speed, to factor in both highways and local traffic. This gives 23 miles commute, one-way. Double that for a day's trip, 46 miles. Now, multiply that by the traditional 5 day workweek and 50 weeks of work per year, and you get approximately 11,600 miles per year.

Cosmic Face-off

It's almost December, 2012, and some people are panicking. Apparently one of the apocalyptic theories is centering around a planetary conjunction (link) happening in a few weeks. I'm going to ignore the apocalyptic part entirely (already read the news today, thanks) and focus on conjunctions, which have boggled me as astronomical "events" for years now.

In fact, there's a basic division I've noticed across amateur astronomers, that I've never really understood. Forget quibbling over 'scope type or comparing CCD camera specs, this is a base-level aesthetic difference. I'm talking about the conjunction/cluster faction vs. the objects faction.

To clarify, in the first group, I'm placing the group of astronomy buffs who go out in the middle of winter, stand on piles of newspaper with a thermos, 12 layers of clothes, and 2 sets of gloves on in order to watch a conjunction or track down an open cluster. In the second group, I'm placing the group of astronomy buffs who go out in the middle of winter, stand on piles of newspaper with a thermos, 12 layers of clothes, and 2 sets of gloves in order to take a several-minute exposure of a nebula or sketch a galaxy. It's not that people don't dabble in both, but most astronomers I've known have a preference for one or the other.

Bias alert: I'm in the second group. I just don't get the attraction of watching a planet and a star appearing to approach each other, or seeing a blob of stars that formed together hanging in space. Give me the faintly-glowing building blocks of the Universe, the bright, whirling arms of a star cradle, or the death-ring of a planetary nebula. Something to really wrap my mind around the varied nature of the dimensions in which we live.

Conjunctions just baffle me. We see shapes in the sky all the time: sometimes they're made of stars, sometimes they're made with planets, but they're just all bright dots from here. We've known for quite some time that they aren't actually close to each other, so what is the attraction? I can see sitting up all night looking at Jupiter or Saturn by itself, but they're only fascinating to me as visible objects, not "stars." Stars are fascinating to think about in comparison to our own Sun, to imagine the other lives that might be orbiting them, or as parts of a constellation telling an old (and probably creepy) myth, but not solely as bright dots in the night sky.

Somehow, I feel astronomy guilt over this, like there's something I'm missing about the philosophy of observational astronomy. I know, objectively, that a sparkling smudge of starlight from a galaxy millions of lightyears away is no more or less appealing than a conjunction, Nature's temporary installation in the cosmic art gallery. But, like most art, I just don't get it. If anyone from the other side of the fence would like to jump in and explain what I'm not seeing when I look up, feel free, I'd love to finally get it!