Space is full of planets we will never visit and may never photograph up close. TOI-1752 c is one of them — a world orbiting a distant star, known to us only through careful measurements of light and gravity. Yet from those measurements alone, scientists have already learned a surprising amount about it.
A Star 336 Light-Years Away
To find TOI-1752 c, you first need to find its host star, TOI-1752. This star sits about 336 light-years from Earth. A light-year is the distance light travels in one year — roughly 9.5 trillion kilometres. So 336 light-years is an almost unimaginable stretch of space.
TOI-1752 is what astronomers call a red dwarf — a star that is smaller and cooler than our Sun. Its surface temperature is about 3,762 K (K stands for Kelvin, a scale scientists use to measure very high or very low temperatures — 3,762 K works out to roughly 3,489 degrees Celsius). Our own Sun’s surface is around 5,778 K, so TOI-1752 runs noticeably cooler. Red dwarfs are actually the most common type of star in our galaxy, even though they are too dim to see with the naked eye.
Two planets are known to orbit TOI-1752 so far. TOI-1752 c is the second one, and it is the focus of this article.
What We Know About TOI-1752 c
TOI-1752 c was discovered in 2026 using the transit method — more on that shortly. Here is what scientists have measured so far.
- Size: Its radius is about 2.29 times Earth’s radius. That makes it noticeably bigger than our planet.
- Mass: It is about 5.86 times as massive as Earth.
- Estimated temperature: Scientists calculate an equilibrium temperature — the expected surface temperature based on starlight alone — of about 291 K, which is roughly 18 degrees Celsius. That is close to a mild spring day on Earth.
- Year length: TOI-1752 c completes one full orbit around its star every 32.7 Earth days. That is just over a month.
Scientists haven’t yet measured everything about this planet. Details like the exact composition of any atmosphere it might have, or the precise conditions on its surface, are still unknown.
How the Transit Method Works
No telescope has ever taken a picture of TOI-1752 c. So how do we know it exists? The answer lies in a clever technique called the transit method.
Imagine you are watching a lamp across a dark room. Now imagine a small ball rolls slowly in front of that lamp. For a moment, the lamp dims slightly — just a little — because the ball is blocking some of its light. When the ball passes, the lamp brightens again. That is exactly what a transiting planet does to its star.
When TOI-1752 c passes between TOI-1752 and Earth, it blocks a tiny slice of the star’s light. Sensitive space telescopes can detect that dip. The dip tells astronomers several things:
- That a planet is there. A regular, repeating dip in a star’s brightness is a strong sign of an orbiting planet.
- How big the planet is. A larger planet blocks more light, so the size of the dip reveals the planet’s radius.
- How long the orbit is. The time between dips tells scientists how many Earth days one orbit takes — in this case, 32.7 days.
The transit method is the most productive planet-finding technique we have so far. It works best when a planet’s orbit is lined up almost edge-on from our point of view. If TOI-1752 c’s orbit were tilted differently, we might never have spotted it at all. You can explore how this works with our interactive planet-finding simulator.
How the Wobble Method Works
The transit method tells us a planet’s size, but not its mass. For mass, scientists often use a second technique called the radial velocity method — sometimes nicknamed the wobble method.
Here is the idea. We tend to think of a planet orbiting a star, but that is a slight simplification. In reality, the planet and the star both orbit a shared centre of gravity between them, a bit like two dancers spinning while holding hands. The star’s movement is very small compared to the planet’s, but it is real. As the star moves slightly toward us, its light gets compressed into shorter wavelengths — it shifts a little toward blue. As it moves away, the light stretches toward longer wavelengths — it shifts toward red. Scientists call this a Doppler shift, named after the physicist who studied how waves change with motion.
By measuring those tiny colour shifts very carefully, astronomers can work out how hard a planet is tugging on its star. A heavier planet pulls harder and creates a bigger wobble. That is how scientists determined that TOI-1752 c has a mass of about 5.86 times Earth’s mass.
Together, the transit method and the wobble method are a powerful pair. One gives us the planet’s size. The other gives us its mass. From both numbers combined, scientists can calculate the planet’s density — how tightly packed its material is — which gives clues about what the planet might be made of.
What Kind of World Might TOI-1752 c Be?
With a radius of 2.29 Earths and a mass of 5.86 Earths, TOI-1752 c falls into a category scientists sometimes call a sub-Neptune — a planet larger than Earth but smaller than Neptune. Planets in this size range are among the most common found around other stars, yet we do not have one in our own solar system to study up close.
The density we can work out from those two measurements suggests TOI-1752 c is probably not a bare rock like Earth. Scientists think it likely has a thick envelope of gas or possibly a deep layer of water or ice beneath any atmosphere, but we do not know for certain. The interior composition of planets this size is still an area of active research and honest uncertainty.
TOI-1752 c and the Question of Habitability
An estimated temperature of around 18 degrees Celsius sounds pleasant. It sits near what astronomers call the habitable zone — the range of distances from a star where temperatures might allow liquid water to exist on a planet’s surface. That is an interesting detail, but it comes with important caution.
The 291 K figure is an equilibrium temperature. It assumes a certain amount of reflected light, and it does not account for any greenhouse effect — the way an atmosphere can trap heat and raise surface temperatures significantly. We do not yet know whether TOI-1752 c even has an atmosphere, let alone what it is made of. Scientists have not found any signs of life or confirmed liquid water there. All we can honestly say is that the numbers place this planet in an intriguing region of its solar system.
What makes TOI-1752 c worth paying attention to is precisely that careful honesty. Two numbers — a dip in a star’s light, and a slight wobble in its colour — are enough to place a world 336 light-years away on the map of known planets. That is a quiet but remarkable achievement of human curiosity and physics working together.