astronomy

All posts tagged astronomy

Icy exomoons need a nurturing environment to grow up in

Posted by admin on April 17, 2015
Posted in: BSU Journal Club. Tagged: , , .

At journal club today, we talked about a study from Heller and Pudritz that looks at the formation of moons around gas giant planets in extrasolar systems.

Heller and Pudritz modeled the conditions in circumplanetary disks around Jupiter-like planets to find where temperatures are right for icy moons like Jupiter’s to form. Like Goldilocks, moon formation requires conditions that are juuust right: the planet can’t be too close to its star or too small.

But given the right conditions, moons will happily accrete around a gas giant and the most massive circumplanetary disks around super-Jovian planets can form moons the size of Mars.

Heller and Pudritz point out that this means if we find an icy moon around one of the many gas giant exoplanets orbiting at about 1 AU from their host stars, we can infer the planet didn’t form there. Instead, it must have formed farther out and migrated in.

And at 1 AU around a Sun- like star, the discovery of such an exomoon would naturally make it a high priority target for habitability studies.

Attendees at today’s journal club included Nathan Grigsby, Jared Hand, Catherine Hartman, Emily Jensen, Liz Kandziolka, and Jacob Sabin.

Observing the Exoplanet-Host 55 Cnc from BSU’s Campus

Posted by admin on April 7, 2015
Posted in: Observing. Tagged: , , .

Had fun playing with the telescope again last night on BSU’s campus.

This time, we observed 55 Cnc, one of very few naked-eye stars that hosts transiting exoplanets. 55 Cnc’s planetary system comprises five fairly large planets, including one twice the size and eight times the mass of Earth in an orbit that roasts its surface at a temperature of 2,360 K — hot enough to vaporize iron.

Below is our image of the sky, annotated by the astrometry.net service (try to ignore the dark doughnut that is probably a dust mote on the telescope). 55 Cnc is the bright star at the bottom and is also called HD 75732.

55 Cnc observed by BSU's campus.

55 Cnc observed by BSU’s campus.

Naming Pluto’s Surface Features and more

Posted by admin on March 23, 2015
Posted in: BSU Journal Club. Tagged: , , , , .
Artist's conception of Pluto's and Charon's surfaces. From http://www.ourpluto.org/home.

Artist’s conception of Pluto’s and Charon’s surfaces. From http://www.ourpluto.org/home.

We talked briefly about several things at Friday’s Journal Club. First, we discussed astrobites.org, a great blog that covers the interesting nitty-gritty of astronomy research. I pointed out that they are requesting submissions from undergrad researchers.

Second, we discussed the New Horizons mission’s request for suggestions for names of features on the surface of Pluto and its moons. After the mission flies by the system, there will be mounds of high resolution images, probably showing a variety of complex surface morphologies. And all that stuff is going to need names.

Third, Jacob presented a recent paper that extends the Titius-Bode relation to extrasolar systems and predict there are about 2 planets in habitable zones per star in our galaxy. A potentially fascinating result, but unfortunately, the T-B relation is probably just an interesting coincidence for our solar system — it has no theoretical basis, and so there’s no reason to believe it can be generalized to other planetary systems. Nevertheless, the article got a lot of press last week.

Finally, we talked about coding in astronomy, and I wanted to post this resource I just heard about, https://python4astronomers.github.io/. Looks to have a lot of helpful tutorials relevant to astronomy.

Friday’s attendees included Jennifer Briggs, Trent Garrett, Nathan Grigsby, Tanier Jaramillo, Emily Jensen, Liz Kandziolka, and Jacob Sabin.

Observing on BSU’s campus

Posted by admin on March 19, 2015
Posted in: Observing. Tagged: , .

Thanks to two of our folks in BSU physics, we’ve finally managed to get one of our telescopes working and took a beautiful image last night of the Orion Nebula.

Orion Nebula captured on-campus at Boise State on 2015 Mar 18.

Orion Nebula captured on-campus at Boise State on 2015 Mar 18.

Update (2015 Mar 29) — I submitted the FITS file image of the Orion nebula to astrometry.net, and it returned the following annotated image:

Astrometry.net fit for our Orion image. From http://nova.astrometry.net/user_images/622647#annotated.

Astrometry.net fit for our Orion image. From http://nova.astrometry.net/user_images/622647#annotated.

Just for my info, the reported image size is 14.6 x 10.9 arcmin and pixel scale is 0.547 arcsec/pixel.

Modeling AGN time-series with Gaussian Processes

Posted by admin on March 17, 2015
Posted in: Data Science. Tagged: , , .

Another attempt at using Gaussian processes to model time series, I’m looking at light curves from active galactic nuclei (AGN). The key thing I’m trying to do here is find and model flaring events.

First, I was interested to see if I could spot outliers representing the peaks of flares, while using a Gaussian processes (GP) model for background variability. The document below shows that attempt. The red band in each plot shows the GP prediction if there were no significant outliers, while the red dots show the outliers. (BTW, the way I embedded the code is very klunky but explained here.)

[gview file=”http://www.astrojack.com/wp-content/uploads/2015/03/looking_for_outliers.pdf”]

Next, I wanted to try to fit one of the apparent flaring events with a model that allowed for correlated noise. To that end, I adapted the example from Foreman-Mackey’s george python module. My solution is shown below. I need to incorporate a variable number of flaring events (I only allowed one for this example), but the model fit worked pretty well. In the second plot below, the blue band shows the range of model fits from the Markov-Chain Monte-Carlo (MCMC) analysis.

[gview file=”http://www.astrojack.com/wp-content/uploads/2015/03/fit_using_GP.pdf”]