## Wednesday, July 24, 2013

### Project Minerva: The hits keep on coming!

Project Minerva co-investigator and former student-mentor of mine, Prof. Nate McCrady, recently won a large grant from NASA's Experimental Program to Stimulate Competitive Research (EPSCoR). w00t!! The funds will be used to pay for student and staff salaries at U. Montana to work on the project, and to purchase one of the four Minerva telescopes.
From NPR:
NASA recently awarded a 1.125 million dollar grant to researchers at the University of Montana to explore, among other things, whether there is life on other planets.
UM will join with three other universities around the country to take part in "Project Minerva", which will use an array of four telescopes to research so-called "exoplanets". UM Associate Professor of Astrophysics, Nate McCrady, will lead the effort in Missoula. In this feature interview, McCrady talks with News Director Sally Mauk about the study of exoplanets - planets that orbit stars other than the sun.
Listen to the interview on the Montana NPR website, here.

## Tuesday, July 23, 2013

### Whoa! Factor 9: A view of home from space

 A view of Saturn, its rings and something more familiar, from the Cassini spacecraft.
The NASA Cassini-Huygens mission is a space craft sent to orbit and study Saturn and its moons. It was launched in 1997 and finally arrived at Saturn in 2004. It's first task was to launch the Huygens probe, which landed on Saturn's largest moon, Titan. The Cassini orbiter is now studying the structure of Saturn's rings, among other tasks.

About a few days ago I received this email from Geoff Marcy:
Dear All,
Today, on July 19, the NASA "Cassini" spacecraft at Saturn will point at Earth and take a picture.
The idea of the image is to highlight how fragile and beautiful the Earth is within the vast, cold, darkness of the universe.
Our colleague Dr. Carolyn Porco is the head of the NASA Cassini imaging team.
NASA and Porco will be pointing the Cassini spacecraft camera at Earth on July 19 at 2:30 (pacific).
They will take an unprecedented planned and publicized image of the Earth and our Moon next to Saturn and its ring system:
http://diamondskyproductions.com/recent/index.php#tdtes
To contribute to this historic event in human history, we plan to point the Keck 1 telescope at Saturn at 7:15pm during twilight and take a photo of Saturn, in return.
Geoff
Look back at the picture at the top of the page. See that blueish, bright star down below Saturn's rings? That's your planet. That's the Earth, the whole entire world, the only habitable, terrestrial planet that we know of. As eloquently stated by Carl Sagan:
The Earth is a very small stage in a vast cosmic arena. Think of the rivers of blood spilled by all those generals and emperors so that in glory and triumph they could become the momentary masters of a fraction of a dot. Think of the endless cruelties visited by the inhabitants of one corner of this pixel on the scarcely distinguishable inhabitants of some other corner. How frequent their misunderstandings, how eager they are to kill one another, how fervent their hatreds. Our posturings, our imagined self-importance, the delusion that we have some privileged position in the universe, are challenged by this point of pale light. Our planet is a lonely speck in the great enveloping cosmic dark. In our obscurity – in all this vastness – there is no hint that help will come from elsewhere to save us from ourselves.
The Earth is the only world known, so far, to harbor life. There is nowhere else, at least in the near future, to which our species could migrate. Visit, yes. Settle, not yet. Like it or not, for the moment, the Earth is where we make our stand. It has been said that astronomy is a humbling and character-building experience. There is perhaps no better demonstration of the folly of human conceits than this distant image of our tiny world. To me, it underscores our responsibility to deal more kindly with one another and to preserve and cherish the pale blue dot, the only home we've ever known.
Here's a closeup, showing the Earth (bright dot) and the Moon (slightly fainter dot below the Earth):

This is why ecological conservatism is more than just tree-hugging and warm fuzzies. This fragile, tiny little mote of dust that we call home is all that we have. There's no life raft (yet), no do-overs. If we destroy habitability on this planet, that's it for humans. Not that it'll matter in a cosmic sense. The Earth will carry on, the laws of nature will continue to operate, new life forms will emerge and rise to take the place that we once occupied. But I'd rather those lifeforms be the kids of my kids' kids, not some unfamiliar creature. That's our job. We are supposed to be the caretakers of this little garden. Too bad we don't act like it.

In the mean time, let's hope we either get our act together to save our place in the emptiness of space, or put together a plan to find another home. I'm working on the latter!

## Sunday, July 21, 2013

### Nerd joke (I think) I made up

Where did the majority of cryptologists grow up?

Highlight this entire line to to see the punchline: North and South Decoder

## Tuesday, July 9, 2013

### How to read a scientific paper

Here are some very handy instructions on how to read a scientific paper, which I give to all of my undergrads and first-year students:

http://www.biochem.arizona.edu/classes/bioc568/papers.htm

Technically, it's written for biology students, but it works equally well for astronomy/physics students. The topics covered include:

### I learned Python!

From xkcd, via Tim:

## Saturday, July 6, 2013

### On IAU Naming Conventions

Via Kartik on Facebook. The comedian Charles Fliescher gives an epic talk on making clear, concise names for places where people don't exist. Fun fact: Euler's work led to string theory, and he did it all without a body!

## Wednesday, July 3, 2013

### Moving. Again.

I started this blog back in 2007 sitting on an empty floor, in an empty living room in Albany, CA, my laptop perched on a cardboard box filled with our stuff. I started writing this blog to distract me from the sadness of leaving. I was mourning because of what I was leaving behind. I even knew that the things I was leaving---classmates, student housing, my Campbell Hall office---weren't permanent. My friends were moving on, too. Heck, my office was about to be torn down. Berkeley, CA was going to move on even if I didn't. I knew this. But it didn't make it less sad. So I started writing, and I haven't stopped.

And here we are again. Another house full of moving boxes. But this time I'm not mourning alone. It hit Owen, too. Owen found an artifact of our old familiar life, one of the old blankets that used to be a permanent fixture of our couch, lying on the floor of the closet. We sat together in the darkness on the blanket, and we cried, together. We cried for the friends we're leaving behind. We cried for the familiar life that will now change. We cried because, as Owen put it, our house feels so empty and it all feels like it's happening too soon.

But it's time to go. A nice couple made an offer on our house Sunday, we countered, and they accepted. It's their house now and it's time for the Johnsons to start anew in our house that's waiting for us in Cambridgeport. It's time to start my new job, make new discoveries, start the year at a new school for the boys, plant new roots, and Erin to restart her career. Also, because it's academia, there are friends there, from Berkeley even!

It's too soon, but at the same time, too long in coming. We've known about this day for a long time now. Jeez, since April. So while it feels too soon, it's also just about time.

## Tuesday, July 2, 2013

### Chemical Calisthenics

I was this Wired article about using hip hop to teach physics and math. Definitely a good read. In the article there was a link to the Blackalicious video shown below. My good friend Pat gave me the heads-up about the group back in the early oughts, but I mostly forgot about them because Blazing Arrow and Nia somehow failed to make it onto my iPod (I need to figure out what went wrong!).

So many excellent tracks. A-to-Z. Tomorrow. The Sky is Falling. The brilliant story-telling of Cliff Hanger. But I never got to see a video until tonight because I came across the music in the pre-Youtube era.

Anyway, I present to you Chemical Calisthenics. Bombalicious:

## Monday, July 1, 2013

### Fun with sub-Nyquist sampling (or Aliasing as Art)

A subwoofer agitates a stream of water at 24 +/- $\epsilon$ Hz, where $\epsilon \sim 1$, while video is recorded at a frame rate of 24  Hz (i.e. sub-Nyquist). Fun ensues!

This effect is known as aliasing, which is also responsible for helicopter blades and car wheels appearing to spin backwards in films. Aliasing is also important in finding planets. We sample the radial velocity variations of stars caused by their planets using instruments such as HIRES at the Keck observatory. If we don't sample with dense enough time coverage (high enough frequency), a sub-sampled radial velocity signal can appear at a shorter or longer period. Here's an example from Wikipedia:

Imagine that the red curve is the true signal and the apparent (measured) signal is blue. You gotta mind your time-sampling! The optimal sampling is less than half the period (twice the frequency), which is known Nyquist samling.

This is what caused planet hunters (including me) to get the orbital period of 55 Cancri e wrong. Bekki Dawson and Dan Fabrycky found the correct signal at a much shorter orbital period than was previously thought. Since the planet was closer to the star, the probability that it would transit increased by a large amount (roughly a factor of 3, if memory serves). This prompted Josh Winn and collaborators to search for transits with a space telescope called MOST. And this is how the brightest transiting planetary system was discovered!

(The fuller story involves a prejudice against the existence of planetary periods less than 1 day, which caused our diagnostic periodogram plots to be plotted starting at 1. This hid the true period near 0.73 days, and drew attention to the aliased signal near 2.8 days. Other more technical details not suited for this blog are covered by Dawson & Fabrycky.)