<h1>Star</h1>
<ul>
<li>Self-luminous, gaseous objects that fuse elements</li>
<li>Obtain <a href="/second-brain/energy">energy</a> from nuclear <a href="/second-brain/fusion">fusion</a></li>
<li>Considered a star when it can sustain itself through  nuclear reactions (making its own <a href="/second-brain/energy">energy</a>)</li>
<li>How long it takes a star to form depends on its <a href="/second-brain/mass">mass</a></li>
</ul>
<h2>Distance from the <a href="/second-brain/earth">Earth</a></h2>
<ol>
<li><a href="/second-brain/parallax">Parallax</a>
<ul>
<li>Limited to ~400 <a href="/second-brain/light-year">light-year</a>s</li>
</ul>
</li>
<li>Using brightness measurements
<ul>
<li>Look at the star, determine it's color spectrum (good indication of it's actual brightness)</li>
<li>Compare the actual brightness with the apparent brightness, they can determine the Distance
<ul>
<li>It's apparent brightness will be dimmer</li>
</ul>
</li>
</ul>
</li>
</ol>
<p><a href="/second-brain/space">Space</a> <a href="/second-brain/astronomy">Astronomy</a></p>

Star

Distance from the Earth

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