22 ASTRONOMY • MAY 2018
Recent observations reveal
that chaos and mayhem
ruled our planetary system’s
first days. by Jesse Emspak
New insights into
HOW THE
SOLAR
SYSTEM
FORMED
The early solar system was rife with
tiny planetesimals, seen here filling
the sky above a young Jupiter. The
giant planet itself likely formed some
3.5 astronomical units (AU) from the
Sun, migrated inward to 1.5 AU, and
then tacked outward again to its
current location. RON MILLER FOR ASTRONOMY