Pi in the Sky 5 promo graphic

Update: March 15, 2018 – The answers to the 2018 NASA Pi Day Challenge are here! View the illustrated answer key

In the News

Pi in the Sky 5

The 2018 NASA Pi Day Challenge

Can you solve these stellar mysteries with pi? Click to get started.

Pi Day, the annual celebration of one of mathematics’ most popular numbers, is back! Representing the ratio of a circle’s circumference to its diameter, pi has many practical applications, including the development and operation of space missions at NASA’s Jet Propulsion Laboratory.

The March 14 holiday is celebrated around the world by math enthusiasts and casual fans alike – from memorizing digits of pi (the current Pi World Ranking record is 70,030 digits) to baking and eating pies.

JPL is inviting people to participate in its 2018 NASA Pi Day Challenge – four illustrated math puzzlers involving pi and real problems scientists and engineers solve to explore space, also available as a free poster! Answers will be released on March 15. 

Why March 14?

Pi is what’s known as an irrational number, meaning its decimal representation never ends and it never repeats. It has been calculated to more than one trillion digits, but NASA scientists and engineers actually use far fewer digits in their calculations (see “How Many Decimals of Pi Do We Really Need?”). The approximation 3.14 is often precise enough, hence the celebration occurring on March 14, or 3/14 (when written in U.S. month/day format). The first known celebration occurred in 1988, and in 2009, the U.S. House of Representatives passed a resolution designating March 14 as Pi Day and encouraging teachers and students to celebrate the day with activities that teach students about pi.

NASA’s Pi Day Challenge

Pi in the Sky 5

Lessons: Pi in the Sky

Explore the entire NASA Pi Day Challenge lesson collection, including free posters and handouts!

To show students how pi is used at NASA and give them a chance to do the very same math, the JPL Education Office has once again put together a Pi Day challenge featuring real-world math problems used for space exploration. This year’s challenge includes exploring the interior of Mars, finding missing helium in the clouds of Jupiter, searching for Earth-size exoplanets and uncovering the mysteries of an asteroid from outside our solar system.

Here’s some of the science behind this year’s challenge:

Scheduled to launch May 5, 2018, the InSight Mars lander will be equipped with several scientific instruments, including a heat flow probe and a seismometer. Together, these instruments will help scientists understand the interior structure of the Red Planet. It’s the first time we’ll get an in-depth look at what’s happening inside Mars. On Earth, seismometers are used to measure the strength and location of earthquakes. Similarly, the seismometer on Insight will allow us to measure marsquakes! The way seismic waves travel through the interior of Mars can tell us a lot about what lies beneath the surface. This year’s Quake Quandary problem challenges students to determine the distance from InSight to a hypothetical marsquake using pi!

Also launching in spring is NASA’s Transiting Exoplanet Survey Satellite, or TESS, mission. TESS is designed to build upon the discoveries made by NASA’s Kepler Space Telescope by searching for exoplanets – planets that orbit stars other than our Sun. Like Kepler, TESS will monitor hundreds of thousands of stars across the sky, looking for the temporary dips in brightness that occur when an exoplanet passes in front of its star from the perspective of TESS. The amount that the star dims helps scientists determine the radius of the exoplanet. Like those exoplanet-hunting scientists, students will have to use pi along with data from Kepler to find the size of an exoplanet in the Solar Sleuth challenge.

Jupiter is our solar system’s largest planet. Shrouded in clouds, the planet’s interior holds clues to the formation of our solar system. In 1995, NASA’s Galileo spacecraft dropped a probe into Jupiter’s atmosphere. The probe detected unusually low levels of helium in the upper atmosphere. It has been hypothesized that the helium was depleted out of the upper atmosphere and transported deeper inside the planet. The extreme pressure inside Jupiter condenses helium into droplets that form inside a liquid metallic hydrogen layer below. Because the helium is denser than the surrounding hydrogen, the helium droplets fall like rain through the liquid metallic hydrogen. In 2016, the Juno spacecraft, which is designed to study Jupiter’s interior, entered orbit around the planet. Juno’s initial gravity measurements have helped scientists better understand the inner layers of Jupiter and how they interact, giving them a clearer window into what goes on inside the planet. In the Helium Heist problem, students can use pi to find out just how much helium has been depleted from Jupiter’s upper atmosphere over the planet’s lifetime.

In October 2017, astronomers spotted a uniquely-shaped object traveling in our solar system. Its path and high velocity led scientists to believe ‘Oumuamua, as it has been dubbed, is actually an object from outside of our solar system – the first ever interstellar visitor to be detected – that made its way to our neighborhood thanks to the Sun’s gravity. In addition to its high speed, ‘Oumuamua is reflecting the Sun’s light with great variation as the asteroid rotates on its axis, causing scientists to conclude it has an elongated shape. In the Asteroid Ace problem, students can use pi to find the rate of rotation for ‘Oumuamua and compare it with Earth’s rotation rate.

Explore More

Join the Conversation

Standards-Aligned Lessons


Facts and Figures



TAGS: Pi Day, Math, Science, Engineering, NASA Pi Day Challenge, K-12, Lesson, Activity, Slideshow, Mars, Jupiter, Exoplanets, Kepler, Kepler-186f, Juno, InSight, TESS, ‘Oumuamua, asteroid, asteroids, NEO, Nearth Earth Object

  • Lyle Tavernier

In the News

On April 19, an asteroid named 2014 JO25 will safely fly by Earth, passing at a distance of about 1.1 million miles (1.8 million kilometers) of the planet. This asteroid poses no threat to Earth and, in fact, asteroids safely fly by Earth quite regularly. What makes the upcoming close approach of asteroid 2014 JO25 unique is that it is a rather large asteroid, measuring about 2,000 feet (more than 600 meters) across. The last time an asteroid that large, or larger, came that close to Earth was in 2004. Not much is known about asteroid 2014 JO25 other than its approximate size, its trajectory (or path around the sun) and that its surface is about twice as reflective as that of the moon. When it passes by, the asteroid will be bright enough that small optical telescopes can be used to spot it in the night sky. Scientists around the world will also study the asteroid with telescopes to determine its composition and rotation and with radar that could reveal small surface features.

Modeling an Asteroid Lesson - NASA/JPL Education

Asteroid Resources for Educators

Explore our collection of standards-aligned lessons all about asteroids!

› View Asteroid Lessons from NASA!

Why It's Important

Asteroids are some of what remains of the material that formed our solar system about 4.6 billion years ago. Unchanged by the forces that have altered rocks on our home planet, the moon, Mars and other destinations around the solar system, asteroids provide a glimpse into what conditions were like when our solar system took shape. Studying the chemical and physical properties, as well as the location and motion of asteroids, is vital to helping us understand how the sun, planets and other solar system bodies came to be.

The study of asteroids is so important, in fact, that NASA has sent several spacecraft to study some of these objects up close. For example, in 2007, the Dawn mission was sent to explore the two largest objects in the asteroid belt, Vesta and Ceres. Dawn arrived at the giant protoplanet Vesta in 2011 and orbited it for about one year before flying to the dwarf planet Ceres, which it continues to orbit and study today. Data from the Dawn mission showed Vesta to be a fascinating world more closely related to terrestrial planets than to typical asteroids and revealed clues that indicate there is a large amount of ice and maybe subsurface liquid water on Ceres. In 2016, NASA launched a spacecraft called OSIRIS-REx, which is headed for an asteroid called Bennu. When it arrives in August 2018, OSIRIS-REx will map the asteroid and collect a sample to return to Earth.

Learn more about NASA's OSIRIS-REx spacecraft and its mission to asteroid Bennu.

But there is another reason studying asteroids and their movements is important: detecting nearby asteroids and predicting any hazard they might pose to Earth.

This graphic shows the orbits of all the known 'potentially hazardous asteroids,' numbering over 1,400 as of early 2013.

This graphic shows the orbits of all the known "potentially hazardous asteroids," numbering over 1,400 as of early 2013. Being classified as a potentially hazardous asteroid does not mean that an asteroid will impact Earth. None of these asteroids depicted is a worrisome threat over the next hundred years. By continuing to observe and track these asteroids, their orbits can be refined and more precise predictions made of their future close approaches and impact probabilities. Image credit: NASA/JPL-Caltech | › Full image and caption

Both 2014 JO25 and Bennu are considered near-Earth objects, meaning their orbits bring them closer than 1.3 astronomical units (AU) from the sun. For comparison, Earth is 1 AU from the sun, or about 93,000,000 miles (150,000,000 kilometers). Also, both asteroids are classified as “potentially hazardous.” A potentially hazardous asteroid is one with an orbit that comes within 0.05 AU (about 4,650,000 miles or 7,480,000 km) of Earth’s orbit and has an absolute magnitude, a measure of brightness, of 22 or less. (On the magnitude scale, the lower the number, the brighter the object.) Absolute magnitude can be an indicator of size, so in other words, potentially hazardous asteroids are large – typically larger than about 500 feet (140 meters) across – and could get close to Earth. Having a designation of “potentially hazardous” does not necessarily indicate the object is a threat to Earth. Scientists use the classification to indicate an object deserves increased attention.

Out of more than 730,000 known asteroids, about 16,000 are near-Earth objects, and there are currently 1,784 potentially hazardous asteroids. But the risks of a large asteroid like 2014 JO25 or Bennu impacting Earth are exceedingly rare. And thanks to the Center for Near Earth Object Studies, or CNEOS, at NASA’s Jet Propulsion Laboratory, we have a very good understanding of where many of these asteroids are and where they are headed. Supporting NASA’s Planetary Defense Coordination Office, CNEOS continually uses new data acquired by telescopes and submitted to the Minor Planet Center to update orbit calculations, analyzes asteroid impact risks over the next century and provides data for every near-Earth object.

How It Works

animated gif of asteroid 2013 MZ5 moving in a fixed background of stars

This animated gif shows asteroid 2013 MZ5 as seen by the University of Hawaii's PanSTARR-1 telescope. The asteroid moves relative to a fixed background of stars. Asteroid 2013 MZ5 is in the right of the first image, towards the top, moving diagonally left/down. Image credit: PS-1/UH

Detecting near-Earth objects, or NEOs, is done by comparing multiple images, taken several minutes apart, of the same region of the sky. The vast majority of the objects appearing in these images are stars and galaxies, and their positions are fixed in the same relative position on all the images. Because a moving near-Earth object would be in a slightly different position on each image while the background stars and galaxies are in the same positions, it can be easy to identify the moving target if it is bright enough.

Surveys done by NASA-supported ground-based telescopes – including Pans-STARRS1 in Maui, Hawaii, as well as the Catalina Sky Survey near Tucson, Arizona – have identified thousands of near-Earth objects. And a space-based telescope called NEOWISE has identified hundreds of others while scanning the skies at near-infrared wavelengths of light from its polar orbit around Earth. Many ground-based telescopes perform follow-up observations to further aid in orbit calculations and to study the physical properties of the objects.

One of the ways that NASA detects and tracks asteroids is with a space telescope called NEOWISE. The spacecraft uses infrared to detect and characterize asteroids and comets. Since December 2013, NEOWISE has discovered 72 near-Earth objects and characterized 439 others. Credit: NASA-JPL/Caltech

Once a near-Earth object is detected, its orbital characteristics are analyzed and astronomers determine if it is a potentially hazardous asteroid. This information is entered into CNEOS’ database, where it is continually updated and impact risks are monitored as new data becomes available.

Teach It

Asteroid 2014 JO25 won’t be this close for another 500 years, so now is a great opportunity to share this close approach with students and remind them that while it’s a close encounter by space standards, Earthlings need not be concerned. Try these standards-aligned lessons and activities with students:

  • Grades 1-6: Whip Up a Moon-Like Crater - Use baking ingredients to whip up a moon-like crater as an asteroid-impact demonstration for students. This activity works in classrooms, camps and at home.

  • Grades 3-5: Modeling an Asteroid - Students will shape their own asteroid models out of clay as a hands-on lesson in how asteroids form, what they are made of, and where they can be found in our solar system.

  • Grades 8-12: Math Rocks: A Lesson in Asteroid Dynamics - Students use math to investigate a real-life asteroid impact.

  • All ages: If you have a telescope, consider trying to view the asteroid at night. You’ll have to know where to look. Solar System Ambassador Eddie Irizarry shares how to find 2014 JO25 here. If you’re looking for more technical information about its location, use JPL’s Solar System Dynamics site to find the asteroid’s ephemeris.

Follow @AsteroidWatch on Twitter or visit the NASA Asteroid Watch website to find out more about upcoming close approaches.

Explore More

TAGS: Asteroid Flyby, Asteroids, Near-Earth Objects, NEOs, Asteroid 2014 JO25, Dawn, OSIRIS-REx, NEOWISE

  • Lyle Tavernier