Choose your stars.
1 of 11 shownA sense of scale
How far away is the nearest star?
Proxima Centauri, the closest star to the Sun, is about 4.25 light-years away. That is roughly 40 trillion kilometers. Make the Sun a 6.7 cm tennis ball and that enormous gap becomes 1,933 km on Earth. Even at this scale, the next star is a long way from home.
Tennis Ball Sun is an interactive astronomy scale model. It keeps distances in proportion to the model Sun and places stars on a Google map. Your location can be the starting point, or you can explore the preview without sharing it.
The nearest-star distance, explained| Star | Real distance | On Earth |
|---|---|---|
| Proxima Centauri | 4.25 light-years | 1,933 km |
| Sirius | 8.61 light-years | 3,919 km |
| Vega | 25.04 light-years | 11,397 km |
| Arcturus | 36.7 light-years | 16,704 km |
| Polaris | 447 light-years | 203,446 km* |
Rounded values from this model. *Polaris exceeds one trip around Earth at tennis-ball scale; its link opens the smaller sand scale.
Go smaller
From a tennis ball to an atom
Change the model Sun from a tennis ball to a grain of sand, a human hair, a bacterium, or a hydrogen atom. The smaller the Sun, the more of space fits onto the same Earth map. With a tennis-ball Sun, one light-year is about 455 km. With an atom-sized Sun, it is less than a micrometer.
At atom scale, the model distance to the observable universe's horizon is about 31,588 km, compared with Earth's 40,075 km circumference. This compares a one-way distance with a trip around Earth; it does not mean the entire observable universe fits inside our planet.
The observable universe at atom scaleA few good questions
Is a light-year a measure of time?
No. A light-year is the distance light travels in a year, approximately 9.46 trillion kilometers. A star 4.25 light-years away is so distant that its light takes about 4.25 years to reach us.
How are the scaled distances calculated?
Each real distance is multiplied by the model Sun's diameter divided by the real Sun's diameter. This map uses 1,392,700 km for the Sun's diameter and 6.7 cm for a tennis ball. Changing scale applies the same factor to every object.
Are the stars shown in their real directions?
Stellar directions are derived from galactic coordinates, with the galactic center mapped upward and galactic longitude 90 degrees to the right. The Earth map is an analogy: it simplifies three-dimensional space and does not show where to look in your local night sky.
Why do some stars need a smaller scale?
When a model distance exceeds Earth's circumference, the map shows a smaller-scale suggestion. Stars such as Polaris and Betelgeuse need a smaller Sun to fit this distance budget. Earendel uses a 12.9-billion-light-year light-travel-distance reference; this differs from its present-day cosmological distance.
Do I have to share my location?
No. The preview works without it. The browser asks for location only after you click Use my location, unless you have already granted permission. When used, the coordinates are included in the Google Maps request to center the map; they are not added to shared links.
Model assumptions and rounded astronomical values: NASA Sun facts, SIMBAD stellar data, and NASA's Earendel observations.