Bad Idea

Is Pluto a Planet? You Decide!

Flow charts are all the rage on the internet these days, or so I've been told. They are also used at my new job. Im guessing that is because the engineers we sometimes have to deal with are used to visualizing systems as block diagrams. Anyway, that got me thinking, Could one of the most publicized astronomical controversies of the last few years be clarified using a flow chart? Here is the result: a flow chart to help you decide whether Pluto should be a planet. 

(For instructions on reading a flow chart, see xkcd).

For those seriously interested in the debate, here's what it boils down to. Most astronomers are concerned with very large questions: how the universe evolves from the Big Bang (cosmology), how galaxies form from the cooling plasma produced by the Big Bang, how stars form within Galaxies, and how the debris surrounding newly-formed stars coalesces into planets. 

For planet formation, the broad question is how dust grains that are less than a micron in size coagulate to form bodies thousands of kilometers across --- an increase in size of a factor of 100 trillion. This process probably has two steps, roughly speaking. First, objects the size of boulders and mountains must be formed. This probably happens slowly, as things collide and stick together. Eventually, something will get big enough that its gravity starts collecting other small bodies, accelerating its growth rapidly until it forms a full-fledged planet. 

We now know that Pluto is a member of the Kuiper belt --- a group of bodies of icy material that has stuck together to form objects with sizes ranging from boulders to mountains. Pluto is one of the largest members, and is interesting because it has enough gravity that it pulled itself into a round shape. Unlike the other planets, however, it did not get big enough to collect much of the material in its orbit. Therefore, it exists among a family of bodies that are similar to the asteroids, but that are icy instead of rocky. For this reason, some members of the International Astronomical Union (IAU) voted that Pluto should not be called a planet.

However, as I mentioned, Pluto is unusual among the Kuiper belt objects in that it has enough gravity to make itself round. In this sense, it is similar to other planets. Pluto probably has more interesting geology than other Kuiper belt objects, so it is useful to study it as an exceptional object. For this reason, and for the historical fact that we have called it a planet for about 75 years, many people feel it should keep its status as a planet. 

The IAU compromised to some degree, calling Pluto a "dwarf planet", along with the asteroid Ceres, and (as of 2009) three other Kuiper belt objects, Eris, Haumea, and Makemake. 

Of course, this doesn't make everyone happy. That's why we need a flow chart.

I Like to Ride My Bicycle

There has been some talk on the web as to whether riding a bike uses more energy than driving a car. I decided to check the numbers, because my gut instinct was that it is way, way more efficient to move myself and a 20 pound bike to work, than it is to move myself and a 3000 pound pound car to work. I would have guessed, say, 100 times more efficient.

There are some analyses on the web, but they tend to miss things (i.e., where food comes from) or be unecessarily convoluted.

I start with our cars. A gallon of gas contains about 31,500 Calories per gallon. Our Prius is getting 40 mpg, which translates to 788 Calories per mile. My 1974 BMW gets at best 20 mpg, or 1575 Calories per mile. If I only drive it short distances, I get closer to 14 mpg, or 2250 Calories per mile. This has to be corrected for the amount of energy needed to extract and refine petroleum so one gets gas, but since roughly half of a barrel of oil can be converted into gas, I doubt the numbers different by more than a factor of two.

Riding a bicycle burns about 42 Calories per mile, if you're riding at a leisurely pace (10 mph). If I go faster, air resistance causes me to burn maybe 50% more. Some of this energy (roughly 8 calories) would be used anyway if I were just watching TV, to keep my brain warm. So, lets say 34 Calories per mile to ride a bike to work, instead of calling in sick. On the face of things, then, it would appear that cycling is at least 23 times more efficient that our Prius. However, food needs to be grown, packaged, and delivered. In the US, for an average diet, every Calorie you eat took about 10-15 Calories of energy to grow, package, distribute, and prepare (link). So, it really takes at least 340 Calories per mile to ride a bike.

Now, cycling has other advantages that one could incorporate. For instance, I will be more healthy. Although some seem to claim this is bad for the environment --- if I live longer, my energy-intensive lifestyle is prolonged --- I think this argument is specious (killing myself is NOT an acceptable solution to our environmental problems!). Of course, bicycles cost a lot less energy to manufacture, but since we insist on having both a car and a bicycle (my wife won't let me carry our daughter on my bike), that point seems a bit moot as well.

Therefore, riding a bike is only about 2 times more efficient than driving a single person in a Prius, and about 4-5 times more efficient than a more ordinary car (assuming my BMW is ordinary, which it is not, because it is one of the best cars ever made!).

Now, if I carpooled, I'd be using the same energy to drive as to cycle. A full Prius would be 2 times more efficient! A scooter, at 70 mpg, is equally efficient as a bicycle. Cycling isn't as green as I thought, because our system for producing and distributing food is inefficient! To really make a difference, I'd need to ride my bike AND buy my food from local sources.

As a corollary, I now understand why machines will end up ruling the earth, and why the premise of The Matrix is really dumb. Meatbags waste energy!

An Echo of Light from Matter Devoured by a Black Hole

I just did my second press conference, at the American Astronomical Society meeting in Seattle. It was the last day, and there weren't many people left at the conference, but that turned out to be good --- my result was the best of the news offerings that day!

I found evidence that the black hole at the center of our Galaxy devoured a small amount of mass (equivalent to the planet Mercury. . . or Pluto, for the stubborn) about 70 years ago. I identified an echo produced as light traveled away from the black hole. The light encountered gas and dust, and was reflected towards us. Because of the length of time it took for the light to reach the clouds before it was reflected, we see the echoes long after the original source of the light had disappeared.

It had long been thought that this phenomena caused gas to fluoresce near the Galactic center. The new aspect of this was that we saw the echo move over the course of three years, as the "ripple" of light moved across the cloud.

The original press release was produced by the Chandra X-ray Center. The work was also covered at geeky repositories of science news like space.com, New Scientist, and by the always-popular (if nothing else) FOX news.

Best of all, though, New Scientist did an interview, and it is available as a Podcast! (Link) I feel like this could be the start of my fifteen minutes of fame! Why, having a Podcast was number 6 on my list of things to do before I make a new list! Of course, number 1 is being on the Daily Show. . . Jon Stewart, are you bored and reading this?

Our Governmet: Protecting Unborn Lives from Astronomers

My next-door neighbor Stan just bought a computer with his research grant, and while he was away one day the secretary came into his office and affixed a UCLA property sticker on his computer. This was a little odd, because UCLA has stopped keeping track of inexpensive computer equipment. It turns out that his grant was administered by the Jet Propulsion Laboratory, and they wanted UCLA to keep track of the computer. So, OK, it made sense.

But then a government auditor came by yesterday, to confirm the existence of the computer, and affix a couple more stickers, as shown in this image. Stan of course asked, "What's the bottom one?" The auditor told him that it was to prevent the computer from being used for non-registered human embryonic stem cell research (hESC). Stan thought it was a joke, but apparently the auditor had no sense of humor.

Stan does study the birth places of stars and planets, but he doesn't think the prohibition against working with stem cells will significantly impact his research. However, we're all now wondering whether he'll be able to look at the this link from his computer.

And we're all just really impressed at how our government defends its principles.

Lost in Conversion

For the tenth anniversary of the orbiting X-ray observatory the Rossi X-ray Timing Explorer, I made a new version of the All-Sky Monitor Movie an animation showing how the X-ray sky looked every 12 hours over the last decade. The original version was made by Don Smith (now at Guilford colloge) and I, under the supervision of Ed Morgan, Al Levine, and Hale Bradt at MIT. A description of the movie, along with the movie itself (which is 41 MB large) is on my (slightly more) professional site.

This being a weblog, it is my opportunity to gripe a bit. I spent several days on the new movie, which is not much time compared to the months it takes me to complete my usual research projects, but it was my vacation time. I had to get Ed Morgan to recover the original routines to make the individual frames off of a back-up, because the disk they were on recently died, and then modify the routine so that the images looked less "Dr. Who-ey" as someone put it. Then I needed to track down a program to compile them as an mpeg (the MJPEG tools worked well). I was happy with how it turned out.

I then turned it over to NASA, so they could put out a press release. It was in the "top 10 most e-mailed news articles" on Yahoo for like 20 minutes early on a Saturday morning! However, if you have the badwidth to spare, you'll see that when they converted it to MOV and SWF formats (what's SWF? is it for a personal ad?), it looks like crap.

Oh, well. I didn't expect to be up for "best animated short" later this month, anyway. . .

Astrophysical Data, Old School

A couple years back, a friend found a box of glass slides at MIT that had been created for a presentation in the 60's or very early 70's. That's way before PowerPoint was invented, and perhaps even before 35 mm slides. In fact, it was also clearly before computerized data collection systems.

Here is a scanned image of the slide that caught my attention. It was apparently created to display how data was collected on an experiement that was launched on a rocket flight. The data was recorded by taking time-lapse photos of instruments that one might find on a lab bench!

The top image contains a circular chamber with radial tracks in it, which is probably bubble chamber that recorded the arrival of protons and electrons, along with a gauge at the center of the bubble chamber to record the pressure. The bottom image contains a line that is probably from an oscilliscope, and an analog stopwatch to record the time at which the image was taken.

Based on what was going on at that time at MIT, my guess is that it was one of the early experiments to study cosmic rays from the sun or X-rays from astronomical sources.

Don't Put on that Tin Foil Hat!

I noiticed this on Boing Boing: four MIT students did a study on the effectiveness of aluminum foil hats in blocking radio-wavelength mind-control waves.. Suprisingly, in some cases the hats amplify radio waves. In their words:

The helmets amplify frequency bands that coincide with those allocated to the US government between 1.2 Ghz and 1.4 Ghz. According to the FCC, These bands are supposedly reserved for ''radio location'' (ie, GPS), and other communications with satellites. The 2.6 Ghz band coincides with mobile phone technology. Though not affiliated by government, these bands are at the hands of multinational corporations.

It requires no stretch of the imagination to conclude that the current helmet craze is likely to have been propagated by the Government, possibly with the involvement of the FCC. We hope this report will encourage the paranoid community to develop improved helmet designs to avoid falling prey to these shortcomings.

Please Don't Panic

A couple years ago, Fred Baganoff and I created an image of the center of our Galaxy as seen by the Chandra X-ray Observatory. It's been used in many places, including on the cover of the 2004 Calendar for Chandra, the cover of the "Science with Constellation-X" white paper, and in a couple press releases.

However, I must admit that I feel like I've really hit the big time now that the image is in the Weekly World News. The image has been flipped and blurred on one edge, but is unmistakably mine. They interpret the Galactic center as a giant acid cloud about to destroy Earth. Needless to say, that hypothesis doesn't have the support of the wider scientific community. If after reading it you find yourself worried, I would suggest living in a giant solid-glass jar that will protect you from the acid, and keep you from bothering the rest of your friends with your unfounded neurotic fears.

Thanks to Craig Heinke for sending me the link. I bet they thought the astronomers who made the image would never find it. I wonder whether they asked NASA's permission to use this? Oh, well. I didn't ask permission to re-use their article for this weblog, so we're even. Long-live fair use!

Galactic Center Haiku (I)

I was wandering through an American Astronomical Society Conference last year, trying to look at the hundreds of posters people had made to display their research. It didn't take long for me to realize, once again, that it is impossible to read all of them. Most of them had way too much information, because the authors wanted to explain all of their research. I just wanted to find the interesting punchlines, and look at some pretty pictures.

I started thinking, how can I make a poster that gets to the point as succinctly as possible? Of course, the answer was, "Haiku!" You're limited to three lines of five, seven, and five syllables per poem. I knew I could write it, since I leaned it in grade school (along with couplets and limericks), and it doesn't even have to rhyme.

This idea didn't really appear out of nowhere. Haiku was also the preferred means of expression for my fellow astronomers, who wrote haiku to express their frustration while studying for their qualifying exams, or when complaining via e-mail about their collaborators. I wish I had copies of those.

Anyway, here is the poster I made after coming up with the idea. I actually put it up at a Galactic Center workship in Santa Barbara in April 2005.

Black Holes Swarming at the Galactic Center

On January 10, 2005, I gave my first press conference, in which I presented evidence that tens of thousands of black holes have settled into the center of our Galaxy. The press release is located on the Chandra X-ray Observatory web site. It was covered by Scientific American, Sky and Telescope Magazine, and USA Today (Jon Miller, whose work leads that article, is a good friend, and graduated in my PhD class from MIT).

I always figured that I'd only get into USA Today if I committed some horrible crime. Now I can get rid of that to-do list...

During the press conference, I was asked how to explain this result to someone's grandmother who has never had a college astronomy course. Here is basically what I said:

At the center of our Galaxy, the density of stars is a million times larger than in our own neighborhood. These stars age and eventually die, leaving behind a white dwarf, neutron star, or black hole. The black holes result from the deaths of the most massive stars, and are the heaviest of the three. Whereas a star like our sun will live for ten billion years and turn into a white dwarf, a star thirty times more massive will live only a few million years and turn into a black hole.

By looking at the motions of the stars at the center of the Galaxy, we know that there is a black hole there weighing several million times the mass of the Sun. As stars orbit this super-massive black hole, the heaviest ones tend to sink, and the lighter ones tend to get kicked out. Most of the heaviest stars turn into black holes fairly quickly, so the heavy objects that collect near the Galactic center are going to be black holes.

The black holes themselves don't emit any light, and so are hard to find. However, most stars come in pairs, orbiting each other like the Earth orbits the Sun. If a black hole happens to be orbited by a star, and the star is too close, the black hole can tear apart the star. As the matter from the star falls into the black hole, it heats up to tens of millions of degrees and emits X-rays (very energetic light). We looked in X-rays to try to find the small fraction black holes in these sorts of binaries, and discovered that they are highly concentrated within three light-years of the super-massive black hole at the center of our Galaxy.