TOI-697 b is a planet 306 light-years away — so far that no telescope can take its picture directly. Yet scientists know it exists, know its size, and even have a good idea of its mass. How? They used two clever methods that turn tiny signals from starlight into real discoveries.
Meeting TOI-697 b
TOI-697 b was discovered in 2026 using the transit method — a technique that catches a planet by the tiny shadow it casts as it crosses its star. A light-year is the distance light travels in one year, which is nearly 10 trillion kilometres. At 306 light-years, TOI-697 b is deep in our galaxy, far beyond anything any spacecraft has ever visited.
The planet orbits a star called TOI-697. So far, scientists have found only one planet in this system. That does not mean it is the only one — it may simply mean others are too small, or orbit at the wrong angle, to detect yet.
TOI-697 b is bigger than Earth but much smaller than the gas giants (huge planets made mostly of gas, like Jupiter or Saturn) in our own solar system. Worlds in this size range are among the most common types found around other stars, and scientists are very curious about what they are made of.
How the Transit Method Works
Imagine holding a tiny coin in front of a bright lamp across a dark room. The lamp dims just a little. That is the basic idea behind the transit method.
When a planet passes in front of its star — from our point of view here on Earth — it blocks a small fraction of the star’s light. A telescope watching that star will notice the light dip slightly, then return to normal when the planet moves away. This dip is called a transit.
Here is how astronomers use it, step by step:
- A telescope stares at a star and measures its brightness very carefully, again and again.
- If the brightness dips by a tiny, regular amount — and then the same dip repeats — that is a sign a planet may be orbiting there.
- How deep the dip is tells scientists how big the planet is compared to the star. A bigger planet blocks more light, so the dip is deeper.
- How often the dip repeats tells scientists how long one orbit takes — the planet’s year.
For TOI-697 b, one orbit takes just 8.61 Earth days. That is a very short year, which tells us the planet sits very close to its star. The transit signal was consistent and repeated, giving scientists confidence this is a real planet.
If you want to see how this process feels, the How We Find Them simulator lets you watch a simulated transit in action.
How the Wobble Method Works
The transit method tells scientists a planet’s size, but not its mass — how much matter it contains. For that, astronomers often turn to a second technique called the radial velocity method, sometimes nicknamed the wobble method.
Here is the idea. A planet does not just orbit its star; the star also moves very slightly in response to the planet’s gravity. Gravity is the pulling force between any two objects. Even a small planet tugs its star a tiny bit. That tug makes the star wobble back and forth as the planet goes around it.
Scientists can detect this wobble by looking at the star’s light very carefully. When the star wobbles toward us, its light gets very slightly bluer. When it wobbles away, its light gets very slightly redder. This shift in colour is called the Doppler effect — the same reason a car horn sounds higher-pitched as it approaches and lower as it drives away.
By measuring how big the colour shift is and how fast it changes, astronomers can work out the planet’s mass. A heavier planet produces a bigger wobble.
For TOI-697 b, this method gave scientists a mass of about 6.16 times Earth’s mass. Combined with the radius from the transit, that lets scientists start to figure out what the planet might be made of.
What We Know About TOI-697 b
Here is a summary of what the data tells us so far:
- Distance from Earth: 306 light-years
- Radius: 2.36 times Earth’s radius
- Mass: 6.16 times Earth’s mass
- Likely temperature: around 840 K, which is about 567 degrees Celsius — extremely hot
- Year length: 8.61 Earth days
These are careful estimates, not perfect measurements. The mass especially carries some uncertainty, as the wobble method involves assumptions about the star and the angle of the orbit. Scientists are honest about this — they say “about 6.16 times Earth” rather than treating it as an exact number.
What Kind of World Might It Be?
Knowing the radius and mass together is powerful. Scientists can calculate the planet’s density — how tightly packed its material is. A very dense planet is likely made mostly of rock and metal, like Earth. A less dense planet probably has a thick atmosphere of gas or even layers of water and ice underneath its atmosphere.
TOI-697 b is roughly 2.36 times wider than Earth but only about 6 times more massive. That combination suggests it is not purely rocky. Scientists think it may have a rocky core surrounded by a thick envelope of lighter gases or other lighter materials. But we do not know for certain — determining what a planet is made of from 306 light-years away is still very difficult.
What we can say with confidence is that TOI-697 b is not a place where life as we know it could survive. At around 567 degrees Celsius, it is far hotter than any oven — hotter even than the surface of Venus. It sits much closer to its star than the habitable zone, which is the region around a star where liquid water could possibly exist on a planet’s surface.
What the Host Star Tells Us
The star TOI-697 has a surface temperature of 5,682 K (K stands for Kelvin, a temperature scale scientists use — 5,682 K is scorching hot). That is somewhat similar to our own Sun, which makes TOI-697 a Sun-like star, though not identical. Stars like this burn steadily for billions of years, which gives planets time to develop and change.
Because TOI-697 b orbits so close and so fast — completing a full trip around its star in under nine days — it receives a tremendous amount of heat and radiation from TOI-697. That is likely the main reason its temperature is estimated to be so high.
TOI-697 b will not be the last word on this system. As telescopes improve and observation time grows, scientists may find more planets orbiting TOI-697, or learn more about the one they already know. For now, this world stands as a good example of how much we can learn about a planet we will never visit — simply by watching the light from a distant star, very carefully, for a very long time.