Astronomy - February 2014

62 ASTRONOMY t FEBRUARY 2014

Explore

THE TRUMPLER

classes of clusters

SKYGAZING

F

rom earliest times, observers

have gazed at loose collections of

stars, grouping them into amor-

phous forms that they correctly

assumed were moving through

space together. But no organization of these

objects existed until one meticulous astron-

omer imposed his classification scheme

upon them. Who he was and what he

accomplished makes a fascinating sidebar

— and a fun observing project — for

today’s amateur astronomers.

The man behind the plan

Robert Julius Trumpler was born in Zurich

on October 2, 1886, the third in a family of

10 children. At age 12, he took the competi-

tive examination for entrance to the Gym-

nasium (high school) and was first in his

class. His interest in astronomy began when

he heard a classmate speak about the origin

of the solar system.

Trumpler entered the University of

Zurich to study astronomy in 1906. Two

years later, he started advanced work at the

University of Göttingen, where he received

his Ph.D. in 1910.

At the meeting of the Astronomische

Gesellschaft in Hamburg in 1913, Trumpler

met Frank Schlesinger, director of the

Allegheny Observatory in Pittsburgh. They

discussed a program for determining the

Since 1930, astronomers have divided the thousands of open

clusters into 36 types. Find out what makes them diferent.

text by Michael E. Bakich; images by Bernhard Hubl

Michael E. Bakich is a senior editor of Astron-

omy. Bernhard Hubl is a highly accredited

astroimager who lives in Schlierbach, Austria.

NGC 6791 has a Trumpler classification of II3r. That means it’s a cluster that stands out against the background, shows a bit of central condensation, contains

both bright and faint stars, and ranks as a rich cluster with more than 100 suns.