YZ Ceti

YZ Ceti is a red dwarf star in the constellation Cetus. It is close to the Sun, only 12 light years away. But it is too dim to see without special tools.

YZ Ceti is a flare star. This means its brightness can change suddenly.

This star is near another famous star called Tau Ceti. They are only about 1.6 light years apart, much closer than the Sun is to Proxima Centauri. YZ Ceti is smaller and less heavy than the Sun, with only 13 percent of the Sun’s mass and 17 percent of its size.

Variability

YZ Ceti is a variable star designation, meaning its brightness changes sometimes. These changes happen when eruptions on the star's surface make it shine brighter for short periods. This type of star is called a UV Ceti star or a flare star.

Besides these bright flashes, YZ Ceti also has smaller, regular changes in brightness. These are caused by starspots—similar to sunspots—moving across the star's surface. Scientists call this kind of change a BY Draconis variables pattern. By watching these small changes, they learned that YZ Ceti takes about 68 days to spin once.

Planetary system

In 2017, scientists found three planets around the star YZ Ceti. They think there might be a fourth planet, but they are still studying it. These planets are very close to the star, so they are too hot for life like ours.

In 2023, scientists found bursts of radio waves from YZ Ceti. This suggests that the closest planet, YZ Ceti b, may have a magnetic field. This could be the first time such a field has been found on a rocky planet outside our solar system.

Main article: HAT-P-11b