Summer Stellar Vibes & Observation Plans

As our hemisphere of this big rock slowly moves into summer, everything focuses on change. The local flora and fauna prepare themselves to weather the harsh summer rays, much better than a certain undergraduate researcher who has lived his whole life underneath the swaddling blanket of Oregon’s clouds. There is an air about the EDEN group that something is about to happen. Which would make sense. Over the past 6 months the group has gone on a handful of observing runs for over a month of collected observable nights. During these observing runs every single undergraduate researcher has undergone at least their first overnight observing run. We have developed advanced systems to process photometric data from our observations. We have gained experience navigating through scientific papers and other astronomical publications to create a detailed database of many potential targets perfectly ripe for observing. We have also grown our international family with the addition of the Max Plank Institute for Astronomy as an institutional partner, joining Steward Observatory and the Vatican Observatory The entire EDEN team has grown in experience on how a survey and more importantly a team works in harmony.

Some personal development is beginning work on EOPAST, or the EDEN Observation Planning and Analysis Strategy Tool. The purpose of this tool will be to query the databases that Jose and Allie (of the Reduction and Targets teams respectively) are working on to provide a myriad of easily accessible information on potential targets for an observing run. To develop EOPAST, I have begun taking online python coding classes to better understand how to obtain and implement code. My plan is to hopefully also include many functionalities in this tool. These could include providing guide stars for targets, available times during a night a target is observable, and the ability to write observing scripts for the telescopes that EDEN frequently uses.

Here is some background information on what some of these terms and things actually mean. EDEN is focused on observing some of the dimmest and faintest stars in our galaxy. These are much dimmer than what humans can see, and provide even a challenge to telescopes to directly focus on. Even small variations from the intended target can be quite detrimental. These telescopes however have a comparatively wide view of a particular portion of the night sky. So, to go around this problem, astronomers instead focus their telescopes on a much brighter star that is in the celestial neighborhood. By focusing the telescope on that guide star, combined with the larger field of view, whenever the telescope takes an exposure the target star is somewhere in the image. Focusing on the brighter target also leaves less room for the tracking system to vary as it moves through the night sky.

Target visibility is a slightly more difficult concept to grasp, but ultimately it’s not that bad. One major component is a concept in astronomy called ‘air mass’ which is basically how much air light from a star must travel through. Objects with a high air mass suffer from more distortions due to the atmosphere, with a perfect air mass level being 1.00. Air mass depends on a number of factors, which include the local ‘sidereal’ time (or just how far away the local time is from the Universal ‘UTC’ timezone), the elevation of the observatory, and their ‘declination’ (which is similar to celestial latitude). Stars that are higher in the sky have a higher air mass generally, with a star directly above you having an air mass of 1.00. You can picture this in the image to the right. The stars that make the small circles have lower air mass, while the stars that make large circles have a higher air mass. Every star that is observable during any particular season has an ‘air mass curve’ as the star moves in the sky over the night.  At the peak of this curve is how close the star gets to the minimum of 1.00.Using the air mass curve, we can then plan when we observe a target and for how long we can observe it. For reference, we can get really good data whenever we observe a target when it is below 1.50 air mass. So, we look at the air mass curve of the target, and only observe it when it is high enough in the sky. Every night of the year this curve shifts for every star, some more than others. Whenever the air mass curve of a star shifts so far that it peaks during the day, we say that the star is ‘out of season.’ We can then plan observations months in advance, picking targets that are in season and have a low enough air mass.

The last concept I want to explain is the process of writing observing scripts. Many modern telescopes are moving to automate many of the processes that are associated with observing. One of the telescopes that our survey uses, the Schulman telescope, has the ability to read observing instructions and follow a plan over the course of a night. This script includes when to open the telescope up, what the coordinates of the guide star are, what angle the telescope must rotate itself, and how many exposures to take and for how long. The cherry on top is that the telesccope will shut down and close the dome all by itself at 4 in the morning, which means we don’t have to stay up until then.

I am also assisting one of our new team members, Luigi Mancini of the Max Planck Institute of Astronomy, to plan observations for late June/ July to utilize the Calar Alto 1.23m telescope of Spain and the Cassini 1.5m telescope of Italy. Using all of the concepts and techniques I just described, there is an interesting phenomenon that we are using to make these observations as powerful as they can be. Due to the large time difference between Southern Europe and Arizona, the telescopes in Europe can begin observing a target in a night, and by the time it reaches a high air mass or the sun begins to come up, our telescopes in Arizona can begin their night and pick up where they left off. All told, this would mean that it would be possible to observe a target continuously for almost 15 hours! This dramatically increases our chances of detecting an exoplanet.

I hope that you now have a better understanding of some of the aspects that go into planning observations. I think this stuff is incredibly cool, and I’m excited for what the future holds for this survey. We are finally poised to move into the next stage of our observations, which is to observe stars looking for previously-unknown exoplanets. This is an incredible time to be alive. These stars are out there, and we are gazing upon an ocean of limitless mystery and wonder.

Image credits: Featured Image, Shah of onebiguniverse-blog. Image 1: davesastrotools.com. Image 2: Videohive.net, Image 3: nikonusa.com