YZ Ceti

YZ Ceti is a red dwarf star located in the constellation Cetus. Even though it is relatively close to the Sun at just 12 light years, this star cannot be seen without special equipment because it is too dim. YZ Ceti is special because it is a flare star, meaning its brightness changes suddenly from time to time.

This star is interesting because it is very close to another well-known star called Tau Ceti. The distance between YZ Ceti and Tau Ceti is only about 1.6 light years, which is much closer than the distance from the Sun to its nearest neighbor, Proxima Centauri. YZ Ceti has only about 13 percent of the mass of the Sun and is also much smaller, with just 17% of the Sun’s radius.

Variability

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

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

Planetary system

In 2017, scientists found three planets around the star YZ Ceti, with a possible fourth planet still being studied. These planets orbit very close to the star, making them too hot to support life as we know it.

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

Main article: HAT-P-11b