Apparent vs Absolute Magnitude

(Contains minor Starstruck spoilers)
The chapter titles to Starstruck (and Starfall) use scientific terms to convey hints about the chapter. Two late chapters of Starstruck are titled “Apparent Magnitude” and “Absolute Magnitude.” A bit of insight on the astronomy meanings of these terms:

“Apparent Magnitude” is how a bright a star (or planet) appears from Earth. Astronomers assign a number to this, with objects that appear brighter from Earth actually having lower numbers than dim objects. For example, the Sun has an apparent magnitude of -27, the Moon -13 (magnitude is on a logarithmic scale, so the Sun is obviously MUCH more than twice as bright as the Moon). The brightest Star Sirius, has an apparent magnitude of about -1.5. Rigel is among the very brightest stars, with a magnitude of about 0 (the dimmest of stars still visible with the naked eye are about magnitude 6). Much, much dimmer objects can be seen with telescopes—for example, the Hubble Space Telescope can see things with a magnitude all the way up to about 32.

But Apparent Magnitude can be deceptive because it’s based on how bright something appears from Earth. How bright something appears to us is obviously a function of how bright it really is, as well as how far away it is. Bright as it seems to us, there are many stars that are much brighter than our Sun. Plus, there are distant galaxies whose combined brightness for their millions of stars is many, many times brighter than our Sun, but we can’t see them at all!

So scientists also refer to something’s “Absolute Magnitude.” Absolute Magnitude is how bright something REALLY is, from a constant distance. Rigel also has a very high Absolute Magnitude, as it’s about as much bigger than our Sun as our Sun is bigger than Earth. In fact, Rigel is about 130,000 times brighter than our own Sun in absolute magnitude! If the Earth were as far from Rigel as it is from our Sun, Rigel would fill fully a THIRD of the sky, and the Earth would be hotter than the planet Mercury!

Anyway, back to Starstruck. In the chapter “Apparent Magnitude” M faces a series of attempts on her life. These efforts fail because she, and her allies, have an advantage in numbers that they believe is absolute. From Jewel, the “apparent magnitude” of the threat against M seems dim.

But the dimness of that threat turns out to be deceptive. In the chapter “Absolute Magnitude,” she discovers the threat is actually much “brighter,” as her enemies are surprisingly able to bring superior numbers against her and her friends. The outcome of the final battle seems hopeless…

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