The Search for Spots

Background

Our relationship with our Sun can be described as complicated. The existence of life on our planet is completely dependent upon it, but it can also prove to be problematic at times through unpredictable surges of harmful energy, known as flares. While our atmosphere deflects the bulk of this energy away from us, some still manages to break through with potential to damage electrical systems, resulting in blackouts.This can also be dangerous to our many orbital satellites and on-duty astronauts. It therefore benefits us to understand our Sun in an attempt to better predict when these hazardous phenomena may occur. Studies have revealed that flares correlate with sunspots, visibly darker areas on the Sun’s surface.

Our Sun. The dark blobs are sunspots.

Our Sun. The dark blobs are sunspots. Credit: NASA SDO

This solar activity is a result of the differential rotation of the Sun (meaning the surface of the Sun rotates slower at the poles than at the equator) combined with convection currents throughout the body; this results in a tangling of its magnetic field lines, which in turn results in the sunspots and flares.

Differential Rotation. The red lines indicate the changing magnetic field lines.

Differential Rotation. The red lines indicate the changing magnetic field lines.

Eventually, these lines become so twisted that the Sun’s magnetic field resets its polarity, starting the whole process over. For our Sun, the magnetic poles reverse approximately once every 11 years, with a total cycle of 22 years.

Our Work

We are attempting to understand magnetic activity by observing the stellar cycles of other stars similar to ours, particularly of known spotted stars in open cluster NGC 6811.

NGC 6811

NGC 6811 – image taken (by us!) in Flagstaff.

NGC 6811 is visible in our night sky during the summer, between the constellations Lyra and Cygnus, and is approximately 4000 light years away. Because of its distance from us, each star that we are interested in is much dimmer than what the human eye can see, and the entire cluster looks very tiny in the sky (the cluster could be blocked by a half moon); it is therefore nearly impossible to directly observe starspots.

NGC 6811 in the night sky - everything we study (and more) is within the red circle

NGC 6811 in the night sky – everything we study (and more) is within the tiny red circle (center). Credit: Sloan Digital Sky Survey

However, we can see overall changes in their apparent brightness to determine changes in average starspot amounts (more starspots = darker surface). To study the stellar cycles of our stars, we are using data from our own Gettysburg College observatory from 2007 as well as from the NURO Observatory in Flagstaff, AZ from 2013, 2014, and our own trip in late June of this year.

The NURO 'scope

The NURO ‘scope

These data were taken using a 31″ diameter telescope which tracked our stars throughout the night as a CCD semiconductor chip processed the collected light into a digital image. We can then use a computer program to determine how bright each star is in relation to some unchanging stars to determine the differential magnitude of each star.

Controlling NURO

Controlling NURO

Finally, we will plot the differential magnitudes over time to see how they change to determine the stellar activity for each star.

KIC9654919 Sample Data Sheet

KIC9654919 Sample Data Sheet – they x-axis represents time in Julian Date, the y-axis represents the difference in magnitude between the target star and a comparison star.

For a glimpse into our research and our trip to Arizona, check out the gallery below!

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