Since we have started exploring
the universe, we are fascinated by exoplanets (extra-solar planets), ‘aliens’,
their super natural powers, their super technology, their weird faces, shapes
and stuff like that. A lot of our literature and movies have used these ideas. From
the times of ‘The War of the Worlds (H.G. Wells - 1898)’ to ‘Men In Black
(Movies – 1997 to 2019)’, everyone likes these alien, planets and galaxies kind of
things.
Why? Well, because everyone is curious about these things.
I, being interested in astronomy, attend various sessions. Today (07 Aug 2020), I attended a session of AstronEra on YouTube about Exoplanet Searching. Ellen Glad spoke on the subject. AstronEra is conducting a lecture series. This was Episode-2. First Episode was streamed on 31st Jul. 2020. Next Episode will be on 14th Aug 2020. Ellen Glad will be faculty for the series. There will more episodes on 21st and 28th Aug. 2020
Session was about methods of searching exoplanets, steps followed for exploration, how it is determined whether the object found is planet or not, and technicalities in between. Ellen also spoke about her experience of working in exoplanet exploration project.
First of all, what is exoplanet? Exoplanet is any planet outside our solar system. There are thousands of exoplanet candidates, which mean they are explored, their location is noted, but further study about their mass, size, orbit has to be done in order to declare them as planet. There are several tools and methods to spot an exoplanet. NASA’s Exoplanet Archive is one of the tools which can be used to spot exoplanet and its host star. This provides information useful to find exoplanet.
Two methods are used to spot down exoplanets. 1) Transit Method, 2) Radial Velocity Method. NASA had launched various exoplanet hunting missions in space, which includes telescopes to look for exoplanets with use of transit method all the time. Ellen talked about what is Transit Method. She has worked with it in a college project of searching for exoplanet.
So, what is Transit Method? Suppose there is a planet, which is orbiting around its star. At certain point, we will see from earth that the planet is transiting through the star. Whenever the planet transits through the star, relative magnitude (brightness) decreases. It creates a dip in the chart, which says that there is a planet! Method to search for the planet with help of dip in the star’s magnitude (brightness) is called Transit Method. Ellen showed a chart of magnitude of a star with a dip.
In order to find an exoplanet with Transit Method, some steps need to be followed.
1. First step is to plan. Look for ETD (Exoplanet Transit Database) to know about occurring transit predictions. Look for how long transit is going be, where in the sky it is going to be. What is starting time, what is ending time, etc. According to that, the day is planned. Only clear sky is not sufficient for spotting the planet. Even the humidity needs to be on the spot to get clear images of stars.
2. Next step is to calibrate the Telescope. Two types of images show imperfections in telescope.
o A) Bias Images show imperfections in sensor. Zero second exposure photos are taken to look after any sensor imperfections.
o B) Flat Field Frames shows optical imperfections. Any problems in lenses are solved here. Five to seven frames of these are sufficient. Frames should be taken after sunset or before sunrise.
3. Then comes the step Pointing. Telescope is pointed to bright star and then the center is aligned. These calibration steps are very important to get sharp and accurate images.
4. Then, start the work, focus on the star.
Post – Processing, Imaging
5. Take Images. Hundreds of images are taken until transit is over or cloud is in between.
6. Perform Photometry. Photometry is performed on each star in the frame, and on each frame photographed. Photometry means determining magnitude (brightness) of the star. When photometry on the frames is done, then the magnitude is plotted with time, and presented in form of chart. If a chart of certain star shows the dip, then congratulations, you discovered a new exoplanet candidate!
This is an entire
process of finding an exoplanet. This data has a lot of value. This data can be
contributed to Exoplanet Transit Database. This database helps us understand
the universe more closely. We could find various elements, various materials and
various minerals on other planets which we have never seen. We can determine whether
they are in habitable-zone of their star or not. Whether they have water in liquid
form or not, whether they have life just like us or they are living in totally
different situation which we cannot even think. There are a lot of ways of
exploration and plenty of things yet to be discovered…
Huge thanks to AstronEra, for arranging such an interesting lecture series. Looking forward to attending more episodes of the series! Also I thank Ellen for such an interesting information she gave...!
- Shantanu Shinde
Email: shantanuspune@gmail.com
Mob. No.: 7887881031
Facebook: @shantanuspune
Instagram: @shantanuspune
Twitter: @shantanubole
