by Alyssa Hui
Did you know there are planets that exist outside of our solar system? Believe it, because they are called exoplanets and there are more planets than just Jupiter, Mars or Venus. Citizen Scientists as well as many other organizations have been studying planets that have a lack of information. Scientists want to understand how and where exoplanets form and what they are like. Studying exoplanets are important, because it is a great way to search for life beyond our Earth. Today, I will review the transit method and the Citizen science project called Planet Hunters.
Citizen Scientists receive most of their data from NASA when they sent the Kepler spacecraft to space. NASA Kepler mission was launched in 2009 and uses the transit technique to detect exoplanets. The transit method helps detect planets that pass in front of the stars they orbit: planets block out starlight which causes the star to dim for a few hours. Every thirty minutes, the Kepler spacecraft gazes at a northern constellation called the “Cygnus” and records the brightness of certain stars that come to view. The measurements of a star’s brightness over time is a light curve. The Kepler spacecraft records data for more than 150,000 stars which is sent to Earth at regular intervals. The data is then downloaded and added to the rest of the data that is collected about light curves. Below is an image of the Kepler spacecraft field of view.
Citation: Hunters Team, Planet. The Kepler Public Data. Digital image. Planet Hunters. Zooniverse, n.d. Web. 25 July 2014. <http://www.planethunters.org/science>.
How do we analyze the light curves that are sent from space? Well the Kepler team has developed computer algorithms (calculations and problem solving made by a computer), to examine light curve data. The computer programs try to inspect every light curve, but the algorithms do make mistakes. The human brain is very good at detecting patterns and when you put human brains together, scientists can understand the data way better. Being a Planet Hunter is an online experiment that allows humans to find patterns in the light curves shown on the website. Citizen participants as well as the Planet Hunters science team, analyzes the data and helps understand types of light curves and also identify oddities.
To help classify the data and find exoplanets, we should look for sharp dips in brightness in the light curve. A dip or transit ( when planets pass in front of their stars ) can occur in a “quiet” or a “variable” light curve. Quiet curves appear more scattered while variable curves appear more wave like. The size of the planet is also reflected in the depth of the transit points. For an example, if a planet is larger, than the dip in the graph would be lower and if the planet is smaller than the dip in the graph will be higher. Below are graphs to help clarify what was stated, showing dips from planets in both variable and quiet curves.
Note: This graph shows a quiet light curve without any variability with a transit. Citation: Hunters Team, Planet. Citizen Science. Light Curve graph. Digital image. Exoplanets Yale Astronomy. Yale, n.d. Web. 25 July 2014. <http://exoplanets.astro.yale.edu/science/citizenscience.php>.
Note: This graph shows a variable light curve with a wave-like variability with a transit. Citation: Hunters Team, Planet. Citizen Science. Light Curve graph. Digital image. Exoplanets Yale Astronomy. Yale, n.d. Web. 25 July 2014. <http://exoplanets.astro.yale.edu/science/citizenscience.php>.
When scientists are detecting planets, finding one transit it is usually not enough, Citizen scientists have to look for repeating transits. The time it takes a planet to complete one orbit is called the orbital period. It can simply mean, counting the number of days from one transit to the next. Planets that are in longer orbital periods, will be more challenging to detect for both humans and computers, because a transit may not appear in every 30-day set of light curve data. The easiest planets to find are large planets that have short orbital periods. Smaller planets with long orbital periods will be more challenging and take longer to detect. It will definitely take time for scientists to detect these planets that orbit stars outside of our solar system. That is why scientists need our help, because the more people that help them the easier they can understand and observe the data.
I have been exploring exoplanets myself, because I feel that exoplanets is a very difficult topic and project to understand and study. I also think they are cool and interesting. I have also been showing images of exoplanets in the Space Visualization Lab (SVL) at the Adler to our amazing guests. If you want to learn and view more about exoplanets stay tuned for my next blog post. I hope you all enjoyed exploring teen blog posts about the astronomy and science that is interesting to them. To learn more about exoplanets you can visit all of the web pages and sites I have used while researching. Thank you once again!
- “Planethunters.org.” Planet Hunters. N.p., n.d. Web. 25 July 2014. <http://www.planethunters.org/classify>.
- “The MEarth Team.” The MEarth Team. N.p., n.d. Web. 25 July 2014. <http://www.cfa.harvard.edu/MEarth/Team.html>.
- “Planets Around Other Stars – NASA Science.” Planets Around Other Stars – NASA Science. N.p., n.d. Web. 23 July 2014. <http://science.nasa.gov/astrophysics/focus-areas/exoplanet-exploration/>.
- “Variable Stars (examples).” Planet Hunters. N.p., n.d. Web. 25 July 2014. <http://blog.planethunters.org/2010/12/28/variable-stars-examples/>.
- “Quiet Stars (examples).” Planet Hunters. N.p., n.d. Web. 25 July 2014. <http://blog.planethunters.org/2010/12/25/quiet-stars-examples/>.
- “Exoplanets.” : Science. N.p., n.d. Web. 25 July 2014. <http://exoplanets.astro.yale.edu/science/citizenscience.php>.