Skew binary number system Skew binary number system The skew binary number system is a non-standard positional numeral system in which the "n"th digit contributes a value of formula_1 times the digit (digits are indexed from 0) instead of formula_2 times as they do in binary. Each digit has a value of 0, 1, or 2. Notice that a number can have many skew binary representations. For example, a decimal number 15 can be written as 1000, 201 and 122. Each number can be written uniquely in skew binary canonical form where there is only at most one instance of the digit 2, which
Contact binary Contact binary In astronomy, a contact binary is a binary star system whose component stars are so close that they touch each other or have merged to share their gaseous envelopes. A binary system whose stars share an envelope may also be called an overcontact binary. Almost all known contact binary systems are eclipsing binaries; eclipsing contact binaries are known as W Ursae Majoris variables, after their type star, W Ursae Majoris. Contact binaries are sometimes confused with common envelopes. However, whereas the configuration of two touching stars in a contact binary has a typical lifetime of millions to billions