text: Below is an context that describes a sql query, paired with an question that provides further information. Write an answer that appropriately completes the request.  # noqa: E501
  ### Context:
  CREATE TABLE table_name_1 (period__days_ INTEGER, type VARCHAR, planetary_mass___m⊕__ VARCHAR, stellar_mass___m__ VARCHAR)
  ### Question:
  What is the smallest period (days) to have a planetary mass of 1, a stellar mass greater than 0.21 and of the type M0?
  ### Answer:
  SELECT MIN(period__days_) FROM table_name_1 WHERE planetary_mass___m⊕__ = 1 AND stellar_mass___m__ > 0.21 AND type = "m0"