Monday, May 31, 2010

Johnson Family Tour of Palomar Observatory

Sunday morning we woke up early, packed a picnic lunch, loaded the kids into the car, and headed South for a day at Palomar Observatory, one of Caltech's optical observatories, along with Keck. I had arranged for our visit with the site manager Dan, who volunteered to give us a private tour of all four active telescopes on the mountain, including the 60-inch (five-foot diameter) also known as the P60, the Oschin 48-inch Schmidt (P48), the little 24-inch, and the mighty 200-inch Hale Telescope.

When we saw the P60 and P48, Owen was fairly impressed, as was Marcus. They both said, "whoooaaahh" when we saw the "medium-sized" telescopes and they definitely wanted to touch their shiny exteriors. Owen was nervous about some of the steep, narrow stairwells. Marcus wanted to touch the hard hats hanging on the walls.

After the first two telescopes we ate lunch at the "Monastery," which is the fancy name for the observer's dorm rooms. Back in the day women weren't allowed to observe, so it really was a lot like a monastery. After eating lunch and grabbing some "special treats" from the big bowl of observing candy, it was time to head off to see the pride of Palomar Mountain. We entered through the ground level where we saw the impressive, 1930s-engineered supporting structure for the dome and telescope, along with various oil pumps and cool looking equipment. We then went up the narrow stars and entered the dome through a side entrance, which led directly under the monstrous 200-inch telescope. Owen's eyes lit up, and so did ours. For the first time all day Owen was literally speechless.

Here he is right after we entered the dome floor

Hanging under the telescope is the Cassegrain instrument cage, which is big enough for a few people to work standing up. In the picture below you get a better sense of scale. The outline on the floor is roughly the size of the 5-meter primary mirror, which rests just above the instrument cage.

There was a scale model of the telescope set up to the side where Owen & Marcus were able to press buttons on an actual-size control paddle to move the model telescope North, South, East and West. We then went up another level to the visitor's deck, about 20 feet off of the dome floor. Dan then went down and started moving the telescope. Then he started moving the gigantic 1000-ton dome, which sits on a nearly frictionless set of well-oiled bearings. It was a weird sensation trying to figure out if we were moving, or if it was the telescope moving while we stayed still. Here's a movie:

While the dome and telescope were moving, Owen stood in rapt attention and then suddenly exclaimed, "Daddy. Nothing is better than this!!" I had to agree. It's certainly not every day that you get to watch a 1000-ton telescope slew while standing on a 1000-ton moving platform.
I really love my job!

After seeing the biggest telescope on the mountain, we hiked over to see the smallest one, the 24-inch telescope, or the TFT as my colleague Mike Brown likes to call it (two-foot telescope, as opposed to the TMT or Thirty-Meter Telescope, the new Caltech/UC telescope soon to be built in Hawaii).

Uncle Dan and Marcus on the way to the TFT

Owen and me outside the TFT

I did my thesis observing on a 24-inch telescope, the CAT, at Lick Observatory. So I have a special place in my heart for the littlest telescope on the mountain.

Another fun part of the day was when Owen "drove" the car from the P60 over to the Monastary. He sat on my lap and steered as I held the car at a steady 7 mph on the empty mountain-top road.

Here are some more pictures from our fun family outing:

Outside the coude room.

Here's a picture of the laser guide star in action, taken by someone with a much better camera than mine!

Eye protection is key, even when the laser is no longer operational.

Owen waits on a long exposure...

Mar drives, too!

Outside the Oschin 48-inch telescope.

Thursday, May 27, 2010

super duper?

On an outing to the LA zoo today, the boys and I were stopped by a dapper fellow
surrounded by a TV crew, lights, microphones and camera in hand. After a few silly, somewhat awkward questions, I learned that we were being filmed for a bit on Jay Leno to air June 11th! It stars comedian Elon Gould as the UK's Super Duper Nanny. I played along and so did the boys and will most likely be made to look like a complete idiot on the show. So, tune in & hopefully you'll see me and the cuties... and hopefully I didn't make too much a fool of myself.

Monday, May 24, 2010

Owen L. Johnson: Bike-rider


Owen has been riding his "running bike" for about a year now. So we took the training wheels off of his other bike, which he rarely used, and he just took off riding like he'd been doing it all his life (or 1/5 of his life). Too bad his "big-boy bike" now looks like a clown cycle!


Also, a neighbor of ours kindly gave us a hand-me-down tricycle for Marcus, so we'll soon extend our family's maximum self-propelled range (MSPR).

Wednesday, May 19, 2010

Giant Exoplanets in the Stellar Mass-Metallicity Plane

Jupiters you seek?
Find massive, metal-rich stars
Planets you will find

The diagram is from Greg Laughlin's I made up the haiku last night. Both pretty much summarize the major results of my latest paper, written with coauthors Kimberly Aller (just-graduated UCB physics/astro major and my REU summer student at U. Hawaii last year), Andrew Howard (UCB Postdoc and planet-hunter extraordinaire), and Justin Crepp (Caltech postdoc, statistics and high-contrast imaging expert).

The dependence of giant planet "occurrence" (where and how often we find gas-giant planets) was the focus of my thesis work at UC Berkeley. I expanded the mass range of our planet search by including "retired" massive stars in our survey. Massive stars are normally rapid rotators, which smears out their spectra and makes them difficult planet-search targets. But when stars get old enough to run out of hydrogen, they move into retirement, which causes them to slow down and become better-behaved targets.

By measuring the fraction of target stars with planets (number of planet-hosts divided by total number of stars), in 2007 I published this plot:

This showed a general trend: massive stars have more planets than low-mass stars. However, by dividing the stellar sample into these broad bins, we couldn't see the underlying form of the relationship. Does the planet fraction rise exponentially? Linearly? Does it turn over?

When I went to Hawaii as a postdoc, I enlarged my sample of retired massive stars by using the larger, Keck telescope. By tripling my sample size I hoped to eventually get a clearer picture than the one we had in 2007.

Last summer, UCB undergraduate astrophysics student Kimberly Aller visited the Institute for Astronomy at the University of Hawaii to do a summer project with me. I started Kimberly off on an small project that she quickly devoured in about two weeks. So I decided to give her a larger, more challenging project: Measure the functional form describing planet occurrence as a function of stellar mass. Oh, and she had to take into account the known effects of stellar metallicity.

Metallicity is a measure of the amount of heave elements in a star's atmosphere. Astronomers call everything heavier than helium a "metal," and for stars we use the amount of iron as a proxy for all of the other "heavy" elements. Debra Fischer and Jeff Valenti showed that stars with heavy metals are far more likely than metal-deficient stars to harbor a giant planet.

So Kimberly used the method of Bayesian inference to simultaneously measure the effects of mass and metallicity on planet occurrence among a sample of 1194 target stars with masses ranging from 20% the mass of the Sun up to twice the Sun's mass. Many thanks to Mike Fitzgerald for originally pointing out this method, way back in 2005! One of the huge advantages of the method is that we don't have to bin the data, which allows us to sense the underlying relationship much more sensitively.

Here's the main figure:
The gray line shows the measured fraction of stars with planets, as a function of stellar mass. The red line is the prediction from our best-fitting model, which accounts for both mass and metallicity. The blue line shows the underlying stellar mass relationship, which is almost exactly linear. The picture is much clearer now!

Kimberly did such a good job developing and implementing the methodology that I decided we needed to publish our results ASAP!

Well, ASAP turned into almost a year later and resulted in a much longer paper than I had originally planned. One reason is that I moved and started a new job right after the summer ended! The other reason for the delay is that this is a pretty important result and I wanted to make sure as possible that we are correct. Andrew Howard helped me check and recheck our planet detections and the targets we used in our analysis. Justin Crepp took our model for a "test drive" and uncovered a couple of major flaws in our early draft. I also received a lot of feedback from the community after giving talks presenting our results and sharing the preprint of our paper. Science in action!

There are two reasons why this result is important. First, it tells us where to look for more planets (hence the haiku above). Second, this result gives us important clues about how planets form. Theoretical models of planet formation must produce more planets around massive, metal-rich stars. In the paper we argue that this implies a bottom-up formation process, whereby Jupiter-like planets start from the collisions of little dust grains, which turn into boulders, then Earth-sized bodies, which then sweep up massive amounts of gas to result in a gas-giant planet with a solid core.

As for where to look for planets, my postdoc Justin Crepp is nearly ready to submit our paper on where to find the next "photogenic" planets! More on that later...

For now, I'm off to our daily, department astro-ph discussion!

All fixed!

The folks at astro-ph responded to my distressed email and replaced my mangled paper this morning. Whew! Apparently when I uploaded a replacement last night, the ms.tex file went missing. I don't understand how and I don't really care. It's fixed now!

Tuesday, May 18, 2010

astro-ph ate my paper!

I've never had a problem with astro-ph before, but tonight it ate my latest paper. Here's the preview version, which I obsessively checked late last night:

And here's the mess that ended up in the official posting.

From now on I'm putting a URL in the meta data pointing to a backup copy. This is fairly disastrous for the debut of what I feel is an important result.

Sorry, I'm venting now. More on the actual science in the paper later...

Monday, May 17, 2010

busy, busy

by e

the last few weeks included a visit from papi, quilting for an auction for owen's preschool, lots of trips to the speech therapist for marcus (who is a bit delayed in his language development) & racing around on a pedal-bike with no training wheels!

during papi's visit we made our way to manhattan beach for a foggy morning of boardwalk bike riding. we also visited the home of the french dip sandwich at phillipe's. so tasty!

Sunday, May 16, 2010

Google Equations!

You can now make pretty equations using LaTeX commands inside of Google Docs! I'm swooning...

Google also added Drawings, but unfortunately the application needs a lot of work. I found it very limited. For example, there's no eraser! WTF?

Heh, complaining about something I didn't know existed a few hours ago reminds me of this:

Louis CK - Everythings Amazing & Nobodys Happy

The whole thing is funny, but the relevant part is halfway through. But seriously, no Eraser Tool?!

As a note to myself, when the iPhone Google apps forget what timezone I'm in, I need to reset Safari. It took me an hour to figure this out. But I shouldn't forget that my phone is talking to a satellite IN SPACE. I should give it a minute...

Saturday, May 15, 2010

My talks

So the video from the Discover/TMT discussion won't be available until the Discover Magazine article is published in a month or two. Until then, if you have a hankering to see me talk about science, here's a webcast of a recent talk I gave for a conference at the Kavli Institute for Theoretical Astrophysics at UC Santa Barbara.

I can't ever bring myself to watch videos of my presentations, so take a look and let me know how I did:

If for some reason you can't access the Flash video, here are the other formats:

Thursday, May 13, 2010