Hello! As an expert in the field of astronomy, I'm here to provide you with accurate information about the cosmos.

The concept of "coldest star" can be a bit misleading because stars, by definition, are hot bodies that emit light and heat due to nuclear fusion reactions in their cores. However, if we're talking about the coolest stars in terms of surface temperature, we're looking at the red dwarfs, which are the smallest and coolest main-sequence stars.

The coolest known main-sequence star is currently identified as 2MASS J05233822-1403022, also known as WISE J052337.10-140302.2. It's a red dwarf located about 40 light-years from Earth and has a surface temperature of approximately 2,400 Kelvin (2,127 degrees Celsius or 3,863 degrees Fahrenheit). This is significantly cooler than our Sun, which has a surface temperature of about 5,500 Kelvin (5,227 degrees Celsius or 9,441 degrees Fahrenheit).

It's important to note that there are even cooler objects that are not quite stars, known as brown dwarfs. These are sub-stellar objects that are not massive enough to sustain the hydrogen fusion process that defines a star. The coolest known brown dwarf is WISE 1828+2650, with a temperature of about 250 Kelvin (-23 degrees Celsius or -9 degrees Fahrenheit).

So, to answer your question, the coldest star in the traditional sense is a red dwarf like 2MASS J05233822-1403022, while the coolest objects that are on the borderline of being considered stars are brown dwarfs like WISE 1828+2650.

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What's more, the new star may not hold its "coldest" title for long: Scientists with NASA's Spitzer Space Telescope are working to confirm an even cooler brown dwarf with possible surface temperatures dipping down to a balmy 86 degrees F (30 degrees C).read more >>