On November 3, 2018, Dan Caselden was playing Counter-Strike when he made history in astronomy. He would always jump on his laptop after he died to check on the automated search of NASA space telescope images.It was suddenly, in the early hours, that something strange appeared. Caselden said it was quite confusing. It moved faster than any other thing I have seen. It was very strange because it was so faint and fast.Original story reprinted by permission of Quanta Magazine. This independent publication published by the Simons Foundation has an editorial policy that allows for the reproduction of this article. It covers research developments in mathematics, the physical and the life sciences and aims to increase public understanding.Caselden sent an email to the Backyard Worlds: Planet 9 team. After excluding the possibility of it being an image artifact they realized that they were seeing something very unusual. An extremely faint object, 50 light-years from them, was blazing through space at 200 km per second. It was named WISE 1534-1043. However, due to its unique characteristics and chance discovery, it quickly earned the nickname Accident.Astronomers believe Caselden discovered a brown dwarf, a star that has lost its bulk and is unable to start nuclear fusion. According to Sarah Casewell, an Astronomer at the University of Leicester, the star forms like a star. It never gains enough mass to fuse hydrogen with helium or start burning anything.The Accident's discovery highlighted the fact that we still have much to discover about brown dwarfs. The mass range of these objects is between 13 and 75 times that of Jupiter, although it remains a mystery where the boundaries lie. Beth Biller, an astronomer from the University of Edinburgh in Britain, stated that people often disagree about this in conferences, especially the lower limit. The 13 Jupiter masses are the approximate mass at which deuterium can fuse. This is what distinguishes brown dwarfs and gas giant planets. However, this boundary can be varied. Biller said that there is nothing special about the 13 Jupiter masses. It's entirely ad-hoc.Temperatures of brown dwarfs can also vary widely. Biller said that the hottest have surface temperatures around 2,000° Celsius, which is about the temperature of a candle flame. Below 200 degrees is the coldest. Brown dwarfs, which do not have heat from their own sources, will slowly cool to lower temperatures over billions of year. Subdwarfs can also be cooler, as they blur the line between brown dwarfs and planets. Below freezing is the temperature of WISE 0855-0714. Biller said that it is the coldest object outside of our solar system.It is not clear what a brown dwarf may look like from up close. They are not likely to be brown, despite their name being suggested by Jill Tarter, an astronomer in 1975. They are more orange or red. It's a good or bad name. Davy Kirkpatrick, an Astronomer at the California Institute of Technology, stated that it has remained so.These atmospheres can also show banding or spotlike storms. Biller and her colleagues used the storms last year to measure wind speed at a brown dwarf located 34 light-years from them. First, they watched the atmosphere of the brown dwarf rotate and brought in features. Then they compared that speed with a measurement of its interior rotation speed. This was derived from its magnetic field. The researchers compared the two values and calculated a wind speed more than 5 times Jupiter's.Brown dwarfs can bridge the gap between planets and stars, which allows them to help us understand both. The boundary between the largest and smallest stars at the top of the mass scale can provide insight into the process of nuclear fusion. Nolan Grieves, a Swiss University researcher, stated that an object must reach temperatures of 3 million degrees Celsius within its core in order to ignite nuclear fusion. This causes a chain reaction which turns hydrogen into Helium. No one knows exactly how much mass is required for this to occur, or when a brown dwarf becomes an star. Biller said that there are many aspects of stellar development that we still don't know much about. One of these questions is where exactly the fusion limit is.
