Star Babies

     IN A UNIVERSE FULL OF TWINS, THE EARTH'S SUN GREW UP AN ONLY CHILD. IN OUR
REGION Of THE GALAXY, ABOUT TWO-THIRDS OF THE STARS HAVE A CLOSE COMPANION, OR
BINARY STAR.  THE GRAVITY BETWEN THE TWO STARS KEEP THEM FOREVER BOUND
TOGETHER--CIRCLING EACH OTHER FURIOUSLY.  THE SUN JUST HAPPENED TO HAVE BEEN
ONE OF THE FEW THAT WAS FORMED SINGLE. . .OR SO IT HAS ALWAYS BEEN THOUGHT.
ASTROPHYSICIST ANDREA GHEZ AT THE UNIVERSITY OF CALIFORNIA, LOS ANGELES, HAS
BEEN EXAMINING A CROP OF VERY YOUNG STARS IN THE TAURUS AND ORION
CONSTELLATIONS THAT MAY CHANGE THIS THEORY.

     Ghez: "When you look at a stellar nursery you see almost all binary stars, and when you see the middle-aged stars like our sun, about two-thirds of them are in binary star systems.  So, there's a discrepancy.  And the
model that I think would explain the discrepancy is that some of these systems are formed as multiple systems,
but . . . they fall apart by the time they get to be the age of our sun. . . .the secondary star actually became
unbound so it drifted away from our sun." 

     THE FACT THAT OUR SUN IS A SINGLET--WHETHER IT WAS BORN THAT WAY, OR LOST
IT'S TWIN--IS CRUCIAL TO THE CREATION OF THE SOLAR SYSTEM, SAYS GHEZ.  PLANETS
FORM AS THE GAS AND DUST AROUND A STAR COAGULATES INTO FIRST MARBLES AND THEN
BOULDERS AND FINALLY WHOLE PLANETS.  BUT A BINARY STAR THAT'S TOO CLOSE
BULLDOZES THROUGH THAT DEBRIS, DESTROYING ANY FLEDGLING EARTHS.

     Ghez:  "most of these stars are actually separated by the distance between our sun and just inside of say,
Pluto, so they're very close and. . . the second star is going to disrupt the gas and dust. . . so I think it's. . . unlikely
that the very closest binary systems are capable of forming stable planetary systems."

     SINCE ABOUT 25% OF BINARY STARS ARE FAR ENOUGH APART THAT THEY MIGHT
EVENTUALLY SEPARATE, GHEZ SAYS THERE'S A GOOD CHANCE ONLY ABOUT 25% OF ALL
THE STARS IN THE UNIVERSE SHOULD HAVE SURROUNDING PLANETS LIKE OUR SUN DOES.