how big is 3i atlas

The size of 3I/ATLAS's nucleus (its solid icy core) is uncertain and estimates vary. The most reliable recent observations by the Hubble Space Telescope indicate the nucleus diameter is between 0.32 km (320 meters) and 5.6 km (3.5 miles), with a likely diameter of less than 1 km (0.62 miles) based on dust loss rates. However, some more recent data from the Vera C. Rubin Observatory suggest the nucleus could be as large as about 7 miles (11.2 km) in diameter, making it potentially the largest interstellar object observed so far. Meanwhile, NASA's SPHEREx mission found a massive carbon dioxide gas coma surrounding 3I/ATLAS spanning at least 348,000 km, indicating a very extensive surrounding cloud of gas and dust, but the nucleus itself remains in the lower size range estimates according to Hubble and other telescopes. There is some debate and uncertainty about the exact size of the nucleus, with estimates ranging from a few hundred meters up to about 11 km.