3 More Numerical Fun Facts About Pluto

How big does the Sun look from Pluto? How bright would it be? And, if you could travel to Pluto, what would the sky look like? Keep on reading to find out!

Jason Marshall, PhD
5-minute read
Episode #248

As you’ve probably heard, after nearly 10 years en route, our intrepid piano-sized, space-exploring robotic friend, New Horizons, successfully made it to (and then sped on by) the dwarf planet Pluto. And the pictures we’ve received thus far have been nothing short of incredible. Those of us who have grown up knowing Pluto as little more than a faint smudge in the sky (which is all of us) have been introduced to a lovely and surprisingly interesting new world.

In anticipation of this historic arrival, last week we took a look at 5 numerical fun facts about the famous dwarf planet Pluto. And now, in celebration of New Horizons’ success, we’re going to take a look at 3 more. Namely, how big is the Sun from Pluto’s perspective? How bright does it appear? And, if you could travel to Pluto, what would the sky look like? Those questions—and their numerical fun fact answers—are exactly what we’ll be talking about today.

Fact #1: How Big Does the Sun Look from Pluto?

As you’ve probably noticed, the further away something is from you, the smaller it looks—trees look really big when you’re standing right next to them, but really small when they’re perched atop a distant mountain peak. As we learned last time, Pluto is currently about 33 times farther away from the Sun than the typical distance between the Earth and the Sun. So, given that things look smaller the farther away they are, and that the Sun is much farther away from Pluto than it is from the Earth, you might wonder: How big would the Sun look from Pluto?

From Pluto the Sun would look roughly 33 times smaller than it does from Earth.

The short answer is that, from Pluto, the Sun would look roughly 33 times smaller than it does from Earth. And that’s because the angular size of something—that’s the angle that the object appears to span from the perspective of the observer—is inversely proportional to the observer’s distance from it. So if one person is twice as far away from something as another, the person who’s farther away will see the object as being half as big in angular extent.

What would the Sun look like if it was 1/33 its current size (as it would from the surface of Pluto)? Well, the Sun and Moon are roughly the same angular size from our perspective, so we can answer this by thinking about what the full Moon would look like if its apparent angular size was shrunk down 33 times. The answer is that the Moon would appear to be right around the same size as the smallest details on the actual full Moon that we can currently just make out. In other words, the Moon would look like a point on the sky without any detail to it. Which is exactly how the Sun would look from Pluto—a point on the sky … just as the other stars appear to us.


About the Author

Jason Marshall, PhD

Jason Marshall is the author of The Math Dude's Quick and Dirty Guide to Algebra. He provides clear explanations of math terms and principles, and his simple tricks for solving basic algebra problems will have even the most math-phobic person looking forward to working out whatever math problem comes their way.