By Jett Peters
Is there extraterrestrial life in the Universe? Do you want to help in the search for answers? Through a unique citizen science project called Exoplanet Watch, anyone with a desire to help can pitch in. Exoplanets are any planets outside of our solar system. Identifying which of these planets have the right conditions for the existence of life is key in the extraterrestrial search. By helping NASA to log data on exoplanets, you can help them to target their efforts to explore these new worlds.
So how do we study these planets? There are several methods, but only one that is achievable with amateur equipment. Before we address the amateur option, let’s look at the direct imaging method, and explain why it is incredibly challenging. You might think this would be the most straightforward way to study exoplanets, but with the scale of the universe and brightness of the host star, the technical challenges are formidable. Dr. Kate Follette, a Professor at Amherst College, describes it this way: imagine trying to see a firefly buzzing near a lighthouse. Now imagine that firefly is buzzing 20 ft away from that lighthouse and you’re trying to see it from 1500 miles away (California to Minnesota). That is what it is like to directly image a hot Jupiter-type exoplanet. What’s amazing is that we can actually do that today, albeit with instruments like the James Webb Space telescope. But in order to see an Earth-like planet around a Sun-like star, we need to do 10,000 times better. Imagine replacing that firefly with a single cell of bioluminescent algae. So imaging planets directly is possible, but only for certain types of planets, and only with the most advanced professional instruments.
However, as previously mentioned, we can use a clever method to detect and study these planets with amateur-level equipment. This method is known as the transit method. It works by analyzing the light from the host star as the planet passes in front of the star. As the planet is crossing in front of the star from our point of view, it slightly dims the light coming from the host star. This dimming is incredibly faint, but with today’s cameras and computer analysis, we can detect it. An animation of an exoplanet transit can be seen in Figure 1.
But why would doing the transit method with a small telescope be a helpful contribution to science? The more often an exoplanet transit is observed and measured, the greater the accuracy of the transit midpoint. If the transit midpoint is well established, the window of time over which observations must be taken with the large Earth and space-based telescopes can be narrowed accordingly, ensuring these large instruments are used as efficiently as possible. Although the time savings might seem minor, time on large instruments such as the James Webb Space Telescope and Hubble is extremely costly. Think in terms of over $100,000 an hour, kind of costly!
So, how is studying exoplanets via the transit method done? The main idea is to image the star while the planet is passing through our line of sight, and then use a special software program to do photometry on the star. This can be done with a wide range of telescopes. Everyone at UDRO has adequate equipment to record an exoplanet transit. It has been proven to work with telescopes smaller than 71mm of aperture. However, it is important not to saturate the star when imaging. When the pixels that are recording the light from the star become saturated, information is lost, and cannot be recovered. It is also important to image some time before the transit begins, and some time after it finishes to provide a baseline for the host star’s brightness.
Timing and choosing what transit to capture can be done through NINA’s Exoplanets plugin, or just with the Swarthmore Transit Finder. The software most commonly used to photometer the star is EXOTIC, which stands for Exoplanet Transit Interpretation Code and has been developed by Exoplanet Watch. Exoplanet Watch’s slack group can be joined at this link; more detailed information on how to execute an exoplanet transit is available at this link. Once the transit has been reduced and a light curve has been produced, you can upload the light curve and data file to the AAVSO (American Association of Variable Star Observers). An example light curve can be seen in figure 2. If someone writes a paper and uses your data point, you will be credited on the paper.
