UsingWavesToFindExoplanets/index.html at gh-pages · SungMatt/UsingWavesToFindExoplanets · GitHub

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<!DOCTYPE html>
<html>
<head>
    <title>
        Using Waves to find Exoplanets
    </title>
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    <meta name="description" content="Using Waves to Find Exoplanets. A project for PC4110, by Matthew Sung" />
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<div style="margin: 20px;">
<h1 id="header">
    Using Waves to find Exoplanets
</h1>
<br>
<p id="definition">
Exoplanets are planets outside our own solar system. A planet is defined by orbiting its star, and not crossing the orbit of other planets.
</p>
<br>
<p id="ways-of-finding-exoplanets">
There are many waves of finding exoplanets, for example;
<ol>
<li>
    Gravitational Lensing
</li>
<li>
    <i>
        <b>
        Radial Velocity
        </b>
    </i>
</li>
<li>
    Transit
</li>
<li>
    Direct Imaging
</li>
<li>
    Timing
</li>
</ol>
These are the five main ways of finding Exoplanets.
</p>
<p>
This write-up will be focusing on <i><b>Radial Velocity</b></i>, as that is the one most involving waves.
</p>
<p>
<a href="https://raw.githubusercontent.com/SungMatt/UsingWavesToFindExoplanets/gh-pages/Resources/Exoplanet_Discovery_Methods_Bar.png" title="Exoplanet Discovery Methods" ><img src="https://raw.githubusercontent.com/SungMatt/UsingWavesToFindExoplanets/gh-pages/Resources/Exoplanet_Discovery_Methods_Bar.png" alt="Number of extrasolar planet discoveries per year through September 2014, with colors indicating method of detection" height="360" width="603" /></a>
<div>
    <table style="width: 60%; background-color:transparent;table-layout:fixed; border:none; border-spacing:0;" role="presentation">
        <tr style="vertical-align: top;">
            <td>
                <div style="margin-right:20px;">
                    <div class="legend"><span class="legend-color" style="display:inline-block; width:1.5em; height:1.5em; margin:1px 0; border:1px solid black; background-color: #0000ab; color:black; font-size:100%; text-align:center;">&#160;</span>&#160;radial velocity
                    </div>
                    <div class="legend"><span class="legend-color" style="display:inline-block; width:1.5em; height:1.5em; margin:1px 0; border:1px solid black; background-color: #00ab00; color:black; font-size:100%; text-align:center;">&#160;</span>&#160;transit
                    </div>
                    <div class="legend"><span class="legend-color" style="display:inline-block; width:1.5em; height:1.5em; margin:1px 0; border:1px solid black; background-color: #abab00; color:black; font-size:100%; text-align:center;">&#160;</span>&#160;timing
                    </div>
                </div>
            </td>
            <td>
                <div style="margin-right: 20px;">
                    <div class="legend"><span class="legend-color" style="display:inline-block; width:1.5em; height:1.5em; margin:1px 0; border:1px solid black; background-color: #ab0000; color:black; font-size:100%; text-align:center;">&#160;</span>&#160;direct imaging
                    </div>
                    <div class="legend"><span class="legend-color" style="display:inline-block; width:1.5em; height:1.5em; margin:1px 0; border:1px solid black; background-color: #ab5500; color:black; font-size:100%; text-align:center;">&#160;</span>&#160;microlensing
                    </div>
                </div>
            </td>
        </tr>
    </table>
</div>
</p>
<div style="width: 300px; padding: 5px; margin: 25px; border-style: solid; border-color: white;">
<h2>Contents</h2>
<ol>
   <li><a href='#header'><span>Home</span></a></li>
   <li><a href='#definition'><span>Definition</span></a></li>
   <li class='active has-sub'><a href='#ways-of-finding-exoplanets'><span>5 Ways Of Finding Exoplanets</span></a>
   <li class='active has-sub'><a href='#radial-velocity'><span>Radial Velocity</span></a>
   <ul style="list-style-type:none">
         <li class='has-sub'><a href=''><span></span></a>
            <ol>
               <li><a href='#steps'><span>Steps To Find Exoplanets</span></a></li>
               <li class='last'><a href='#mathematics'><span>Mathematics</span></a></li>
            </ol>
         </li>
         <li class='has-sub'><a href='#examples'><span>Examples</span></a>
            <ol>
               <li><a href='#Gliese581b'><span>Gliese 581b</span></a></li>
               <li class='last'><a href='#Kepler16b'><span>Kepler 16b</span></a></li>
            </ol>
         </li>
   </ul>
   <li><a href='#Future'><span>Future of Detection</span></a></li>
   <li class='last'><a href='#References'><span>References</span></a></li>
</ol>
</div>
<h2 id="radial-velocity">
    <span>Radial Velocity</span>
</h2>
<p>
------------------------------
</p>
<p>
Radial Velocity is the exoplanet's orbital velocity around the star. We use the color of the star as a marker, as it has certain color.
</p>
<h3 id="steps">
    Steps for finding exoplanets
</h3>
<ol>
    <li>
        Observe color of star over a long period.
    </li>
    <li>
        If color of star varies, without brightness changing, measure wavelength difference over time.
    </li>
    <li>
        If brightness varies, you found a double star.
    </li>
    <li>
        Wavelength difference will allow you to find the speed of the planet around the star, and thus its orbit.
    </li>
</ol>
<h3 id="mathematics">
Mathematics
</h3>
<p>
Using the Doppler shift formula,  λ<sub>0</sub>/λ=v/c
<br>
Where:
<br>
λ<sub>0</sub> is initial wavelength
<br>
λ is wavelength
<br>
v is relative velocity of object
<br>
c is the speed of light (299 792 458 m/s)
<br>
Velocity will be the relative velocity to the viewer. As most planets are much closer to their planet than the star system is to earth, We can assume that the angle between the line connecting two opposing ends of the orbit and the viewer is taken to be 90º.
</p>
<br>
<p>
    This motion as observed from earth follows <i>Simple Harmonic Motion</i>, however, as the star's light is usually much brighter and extincts the light from the planet, we observe the brightness difference of the star. The varying magnitude of the star would allow us to detect when the planet is transiting across the star surface when viewed from earth or just a rocky body.
</p>
<h2>
    <span id="Examples">Examples</span>
</h2>
<p>
------------------------------
</p>
<p id="Gliese581b">
    <i>Gliese 581 c</i>, is an exoplanet detected by <i>Radial Velocity</i>, on April 4<sup>th</sup> 2007. It is of particular intrest to astronomers as <i>Gliese 581 c</i> lives in the parent star's <i>habitable zone</i>, which is the distance from the star in which liquid water can exist on its surface.
    <i>Gilese 581 c</i> has a mass of 5.5 times of earth, and orbits its parent star at 11 million km (7% of earth's orbital radius, 149597870.6 km).
</p>
<p id="Kepler 16b">
    <i>Kepler 16(AB)b</i>, is a very special exoplanet, as this exoplanet orbits 2 stars, instead of one. This is the first exoplanet to be discovered orbiting a binary planet.
    <a href="https://raw.githubusercontent.com/SungMatt/UsingWavesToFindExoplanets/gh-pages/Resources/Kepler16b.gif" title="Exoplanet Discovery Methods" ><img src="https://raw.githubusercontent.com/SungMatt/UsingWavesToFindExoplanets/gh-pages/Resources/Kepler16b.gif" alt="Author's rendition of Kepler 16b's orbit."/></a>
</p>
<br>
<br>
<h2 id="Future">
    The Future of Exoplanet detection
</h2>
<p>
    The future of exoplanet detection looks very promising, and is pushed by the boom of technology. Out of all the exoplanet detection methods, <i>Radial Velocity</i> looks the most developed and advanced of them all. This is because optics design has been becoming better and better to detect spectral lines.
</p>
<p>
    The current spectrography equipment has a resolution of 0.3m/s, while the next generation technologies will refine it down to 0.1m/s. This will allow the detection of down to earth sized exoplanets.
</p>
<p>
    The future is looking bright for exoplanets indeed!
</p>
<br>
<br>
<h2 id="references">
References
</h2>
<p>
    <a href="http://upload.wikimedia.org/wikipedia/commons/c/c5/Exoplanet_Discovery_Methods_Bar.png">Graph</a>
    <br>
    <a href="http://www.planetary.org/explore/space-topics/exoplanets/radial-velocity.html">Quick reference</a>
    <br>
    Astro club work, 2012-2015
    <br>
    Own readings
</p>
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