-Auromic Behera and Preity Sukla Sahani
ଓଡ଼ିଆ ରେ ଏହି ଲେଖା କୁ ପଢ଼ିବା ପାଁଇ ଏଠାରେ କ୍ଲିକ୍ କରନ୍ତୁI
INTRODUCTION
Well, we always try to get a sight of stars, planets, and other structures in the sky with the means we have with us. However, do you know how scientists and astronomers actually determine about the planets and other structures like stars, galaxies, etc.? Finding exoplanets and other systems is a complicated process to start with- it can easily be detected by various ways, Here we will be discussing two methods, i.e. Transit Method and Direct Imaging in a simple manners.
TRANSIT METHOD
Let us say there is a Planet X roaming around a star far away or, in better terms, orbiting it. Whenever it moves, the intensity of the light also decreases. This particular term is known as ‘drop in starlight’. Usually, we use the light spectrum as a reference to determine the minute details about the information which one would capture. Now, how does it actually work? The most important factor for this is ‘position’. It can only detect when an object is present in between the observer and the light source.
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Figure 1 : Drop in Starlight |
What have we achieved so far?
Using the transit method, one can easily identify the external features such as it’s atmosphere , size, orbital period, temperature, etc. As we can detect the type of atmosphere, it is also easy to detect the type of gas and its suitability to sustain life in it via spectroscopy, as the primary mission is to find a Habitable Planet. You will be amazed to know that around 76.5 percent of exoplanets and other structures have been found by the Transit Method itself!
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Figure 2: TESS around an Orbiting Planet |
What’s the catch here?
The Transit Method only tells us about the existence of a structure, which means there can be moments where they give false positives, which sums up around 40 percent of all things discovered. Due to the alignment of structures, one can easily use this method. Sadly, only around 10 percent of planets actually align, which shows a very small variation, making it hard to recognise. Due to which, this method is used to identify a large number of structures at a time. The limited number of findings also makes it difficult to go into deeper areas of the undiscovered system.
Discovery till date
During Kepler Mission from 2009-2013, 2337 exoplanets were discovered, and after it’s system failure, It was directed into K2 mission in which it found 178 more exoplanets. The most recent TESS (Transiting Exoplanet Survey Satellite ) The satellite has found 180 exoplanets till now. James Webb telescope, launched in 2021 - is expected to increase the number of confirmed exoplanets.
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Figure 3 : Planet LHS3844b, discovered in 2018 by NASA's TESS Mission located 48.6 light years away from Earth and has a radius 1.3 times that of Earth |
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Figure 4 : TOI 700d 's simulated image, It is the first Earth-size habitable-zone planet discovered by TESS |
DIRECT IMAGING
To solve the problem of losing reflected starlight, which often happens in the The Transit Method, Direct Imaging was introduced. Now it is not always based upon the light, instead it is more dependent upon the Thermal Emissions of the planet, which, as the name suggests, depicts its data from the temperature of the structure’s surface. The most important thing here is, it helps in confirmation of the structure which is generally detected by other methods .
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Figure 5 : Exoplanets around a star found using Direct Imaging Technique |
Advantages ?
At par with the transit method, the Direct Method has more accuracy in the field, i.e., gives up less false positives. Whenever any structure is detected using D.I. It has always been helpful for scientists to guess and discover the type of elements the structure is made of and, of course, the rate of sustainability it has. It has always been helpful in finding out great systems in the galaxy and beyond. And to mention, the InfraRed method has also been helpful in finding some of the small systems which are not possible in the Thermal Imaging method.
Well, it is very rare that any system can be caught off for this reason and it is strongly supported by the amount of discoveries made till date. ”Lights” which play an important role here may not even reach to the observer sometimes, which results in the losing of resources, time, etc. This mostly gives results for the planet having a large mass or simply if it is a giant planet. Sometimes, while measuring the thermal emissions, it gets disrupted due to the Atmospheric Turbulence of Earth, making it harder to get the correct data. Well, and yes, it is not a perfect method to find a sustainable planet for mankind.
As of now, 50 exoplanets have been detected using the technique, The first the discovered exoplanet was captured using ESO’s Very Large Telescope Array. Subsequently, more exoplanets were discovered, after a few discoveries, The Hubble Telescope was able to add its name by finding The Fomalhaut system, deriving the Fomalhaut-B planet from it. Kepler space telescope did discover 4600 exoplanetary candidates during it’s brief lifetime. Further discoveries are also taking place to achieve an enormous success rate.
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Figure 6: Findings using Direct Imaging Technique |
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Figure 8 : The Fomalhaut system (by Hubble Telescope) Highlighted part showing the course of planet over years |
CONCLUSION
While there can be many methods to reach out to exoplanets and discover systems, any of the systems is not completely self-reliable. It has to work with any other system to get at least specific data about the system. While Transit is better in numbers, D.I. technique is better in terms of quality. Taking them together, many systems have been and will be found out in the recent future!
References:
- https://www.universetoday.com/140341/what-is-direct-imaging/
- https://exoplanets.nasa.gov/tess/
- https://exoplanets.nasa.gov/news/1605/observing-exoplanets-what-can-we-really-see/
- http://research.iac.es/proyecto/tep//transitmet.html
Written By –
Auromic Behera and Preity Sukla
Sahani
