How do scientists find and track asteroids?

In one line

The rule

Asteroids are found and tracked by observing their positions in the sky over time, measuring their brightness, and calculating their orbits using repeated images and mathematical models.

No single formula, but tracking uses the basic idea: Position at time t₁, t₂, t₃ → Calculate path (orbit).

Let's understand it simply

Imagine you are playing cricket at night, and someone throws a ball high in the air. You can see it because the streetlight shines on it. If you take a photo every second, you can see where the ball is at each moment. By looking at the photos, you can tell how fast it is moving and where it is going.

Scientists do something similar with asteroids. They use big telescopes (like giant eyes) to take many pictures of the sky. Asteroids look like tiny moving dots among the stars. By comparing pictures taken at different times, they spot which dots have moved. That’s how they find and follow asteroids.

How it works

1. Scanning the sky: Scientists use telescopes to take wide pictures of the night sky, often with special cameras.
2. Taking repeated images: They take several pictures of the same part of the sky, minutes or hours apart.
3. Spotting movement: Computers compare the images to find dots (asteroids) that move, while stars stay in the same place.
4. Measuring position: They record the exact position of the moving dot in each image.
5. Calculating the orbit: Using the positions and times, they use maths to work out the asteroid’s path around the Sun.
6. Tracking over time: They keep watching the asteroid to update its path and check if it might come close to Earth.

The story behind it

The first asteroid, Ceres, was found in 1801 by Giuseppe Piazzi, an Italian astronomer. He was looking for a missing planet between Mars and Jupiter. He noticed a tiny dot that moved differently from the stars. Over the years, scientists built better telescopes and cameras. Today, computer programs help scan thousands of images quickly. Modern surveys like Pan-STARRS and NASA’s NEOWISE use robotic telescopes to find new asteroids every night. The work is now a team effort, with scientists around the world sharing data.

Where you see it in real life

• NASA’s Near-Earth Object Observations: Scientists use space telescopes to spot asteroids that could come close to Earth.
• ISRO’s asteroid tracking: Indian scientists use observatories like the IUCAA Girawali Observatory to monitor asteroids.
• School science fairs: Students sometimes track bright asteroids using backyard telescopes and free online images.
• Movies like ‘Armageddon’: Show scientists racing to find and track dangerous asteroids.
• News reports: When a big asteroid passes near Earth, scientists announce its path and how close it will come.
• Space missions: Spacecraft like NASA’s OSIRIS-REx visit asteroids after tracking their orbits for years.

Why it matters

• Protecting Earth: Tracking asteroids helps warn us if any might hit Earth, so we can prepare or try to stop them.
• Understanding the solar system: Asteroids are leftovers from when planets formed. Studying them teaches us about the past.
• Space mining: Some asteroids have metals and water. Tracking them helps plan future mining missions.
• Science and technology careers: Learning to find and track asteroids uses maths, computers, and teamwork—skills needed in many jobs.

Worked example

Let’s see how a scientist tracks an asteroid:

Given:  Three images of the same sky area, taken at 8:00 pm, 8:10 pm, and 8:20 pm.
Step 1: Compare the images to find a dot that moves.
Step 2: Measure its position in each image (say, X₁, X₂, X₃).
Step 3: Calculate how far it moved each time (distance/time = speed).
Step 4: Use the positions and times to estimate its orbit around the Sun.
Step 5: Predict where it will be next week or next year.

Common mistakes

• Confusing stars with asteroids: Stars do not move in the images; asteroids do. Always look for the moving dot.
• Thinking all asteroids are dangerous: Most never come close to Earth. Only a small number are tracked for safety.
• Believing only space telescopes can find asteroids: Many are found with ground-based telescopes on Earth.
• Forgetting to take enough images: Without several pictures, you cannot track the movement or calculate the path.

Remember it

Asteroids are tracked by taking many sky pictures, finding the moving dots, and using maths to predict their path.