2015A Day 37: Inside the solar system – Extreme Wavefront Control Lab

This is the final night of my 7-night run at the Clay on MagAO, sharing nights with Alycia & TJ. I have a few hours per night to image Pluto and Charon with Clio and VisAO, to get their separate photometric light curves in many filters over their 6.4-day period. We’re also doing some astrometry and high-res imaging to prepare for a stellar occultation by Pluto on 29 June. This event will be visible from the area around New Zealand, Australia, and Antarctica, and we have the good fortune of having SOFIA for this event. The prediction webpage is here. Even though we’re not observing a Pluto occultation during this run, I’ll give a little background on occultations.

The predicted shadow path of the Pluto occultation on 29 June 2015. The three solid lines show the paths of Pluto's centerline, upper limb, and lower limb. The dashed line above Australia is the 3-sigma line from the north limb. — The predicted shadow path of the Pluto occultation on 29 June 2015. The three solid lines show the paths of Pluto’s centerline, upper limb, and lower limb. The dashed line above Australia is the 3-sigma line from the north limb.

When we observe a stellar occultation, we observe the brightness of the star and how quickly it changes as Pluto moves in front of it. From a SNR point of view, it would be optimal if the occulting body were invisible so it wouldn’t add background noise to the observations. For this event, we get pretty close to that as Pluto is 2 mags fainter than the star.

With occultations, we can probe the temperature of Pluto’s atmosphere as a function of altitude but using the known refractivity of component gasses. As Pluto’s atmosphere passes in front of the star, it bends the light thereby dimming it. Using this method, we can detect and measure Pluto’s microbar atmosphere from more than 30 AU away.

Here’s another example of refraction: moonset on Sunday morning. You can see the shape of the moon contract and expand as it passes through different atmospheric layers. With slightly different temperatures (as well as scattering and absorption), the refraction changes from layer to layer.

Some other photos from last night and tonight:

Atom's first night running Clio. This is Thanawuth (Atom) Thanathibodee, a rising senior at MIT. He started his summer work two days after finals, and will be working on Pluto all summer. — Atom’s first night running Clio. This is Thanawuth (Atom) Thanathibodee, a rising senior at MIT. He started his summer work two days after finals, and will be working on Pluto all summer.

Our control room tonight (clockwise from left): Kim Ward-Duong on AO, Atom on Clio, Alberto on all things telescope (and DON'T call him by the wrong name), me falling over in the chair, Katie Morzinski and Jared Males on VisAO. — Our control room tonight (clockwise from left): Kim Ward-Duong on AO, Atom on Clio, Alberto on all things telescope (and DON’T call him by the wrong name), me falling over in the chair, Katie Morzinski and Jared Males on VisAO.

Arizonans. I think this was the moment after I learned of our common link to Flagstaff. Kim was an undergrad at NAU and worked at Lowell! Kim is now in grad school at ASU, and Katie is at U of A. (I worked at Lowell for 16 years.) — Arizonans. I think this was the moment after I learned of our common link to Flagstaff. Kim was an undergrad at NAU and worked at Lowell, and Katie worked at Lowell too! Kim is now in grad school at ASU, and Katie is at U of A. (I worked at Lowell for 16 years.)

And now the song. I had to get a primer from Katie, with a run-down of all the various rules. This is the only song I’m aware of that mentions Pluto specifically. A quick google search of song lyrics shows that of course there are more, but I’m too tired to listen to them now. So I’ll give you Christine Lavin’s Planet X:

Sadly, Chris Daughtry does not seem to have covered this (yet).