This may not seem like such a big deal, but it's not very common for us to find exoplanets (planets outside of our own solar system) to be smaller than Earth in size, or us to fine one so relatively close. The planet, named UCF-1.01, is "just" 33 light years away. Additionally, Spitzer is normally used to study exoplanets already discovered and not to discover new exoplanets, so this is not only a first for the telescope, but a potential new role in for it.

Size-wise, UCF-1.01 is around 5,200 miles in diameter, and was discovered when scientists were using Spitzer to study Neptune-sized exoplanet GJ 436b, which orbits the red-dwarf star GJ 436. Scientists noticed "dips" in the infrared coming from the star that were not caused from GJ 436b passing by it. This in turn led to the discovery of UCT-1.01. Its year lasts only about 1.4 Earth days due to how close the planet orbits its star.

The planet's temperatures are around 1,000 degrees Fahrenheit, meaning there's very little in terms of atmosphere. This isn't surprising, considering how closely it orbits its sun. Scientists believe the planet itself has melted slightly, causing a molten surface.

It's a precious discovery, considering that of the 1,800 planetary candidates discovered by NASA, only three were smaller than Earth. Three. You can find out more about the Spitzer Space Telescope and its missions on NASA's .

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