George Herbig (1920–2013) Astronomer Who Pioneered Studies of Young Stars

COMMENT OBITUARY George Herbig (1920–2013) Astronomer who pioneered studies of young stars.

eorge Herbig’s research, which Herbig was fascinated by stars that spanned more than 70 years, built are oddballs, recognizing that because the foundation on which rests our stars live so much longer than humans, Gpresent-day understanding of the birth of important evolutionary stages — if brief stars and of the properties of young stars. enough — may be seen only very rarely. He had an uncanny ability to identify In 1936, a faint variable star, FU Orionis, astronomical objects and research topics brightened 100-fold within six months, that would become key elements in the and has barely declined in luminosity study of early stellar evolution. since. Herbig studied this star and similar Herbig, who died on 12 October, was cases, and realized that such events repre- an only child born in modest circum- sent important episodes in the early lives stances in Wheeling, West Virginia. His of some stars. Unafraid to take a stand father, a tailor, had settled there after against the prevailing wisdom, Herbig emigrating from Germany. Sometime maintained that these ‘FUor’ events rep- ASTRONOMY FOR INST. HAWAII KAREN TERAMURA/UNIV. after his father’s early death, Herbig resent rapidly rotating young stars near moved to Los Angeles, California, where the point of break-up. Most in the com- as a teenager he built his first telescope. munity believe that such events are the The nearby Mount Wilson Observatory, result of heating in a surrounding disk, housing what was then the world’s largest which makes the disk self-luminous. But telescope, with a 2.5-metre mirror, fos- there are now signs that a hybrid model tered his growing interest in astronomy. combining both these aspects might Through joining the Los Angeles explain what is actually happening. Astronomical Society as a young man, At an age when most people retire, Herbig met many of the great astrono- Herbig embarked with his students on a mers of the time, and had the opportunity series of observational studies of clusters to attend observations at Mount Wilson. He study of these young stars (G. H. Herbig Adv. of very young stars — groups of many hun- later spoke of the awe he had experienced Astr. Astrophys. 1, 47–103; 1962). dreds or thousands of stars born together. when looking, using the spectrograph slit of As part of his investigation of T Tauri He espoused the idea that star formation the 2.5-metre telescope, at the giant star Mira stars, Herbig studied a region of dark in clusters proceeds over several millions — a luminous red spot, seemingly boiling as clouds in the Orion constellation, in which of years, with most low-mass stars forming a result of its light passing through Earth’s he noticed small nebulous objects with first, until the birth of very energetic massive turbulent atmosphere. At the tender age peculiar spectra. This class is now known stars suddenly destroys the clouds of gas and of 20 he published his first brief scientific as Herbig–Haro objects, after Herbig and dust from which stars are born and brings results, on the diameter of stars. astronomer Guillermo Haro, who had inde- further star formation to a rapid halt. From observations spanning from the late pendently discovered them. Over several Modest, mild-mannered and softly spo- 1930s to the early 1940s, Herbig’s mentor, decades of study, Herbig and his collabora- ken, George exuded a quiet authority. He was Alfred Joy, had discovered a peculiar class tors established that Herbig–Haro objects an independent and private man, usually of variable stars named after the prototype move with supersonic velocities away from observing alone, and commonly processing star T Tauri. These objects are often associ- newborn stars, and are thus the signposts of and analysing the data himself. During his ated with dark interstellar clouds, and it was recent star-formation events. long career he saw major transformations in initially speculated that their characteristic T Tauri stars are low-mass stars that even- instrumentation and techniques — such as variable brightness could be attributed to the tually become similar to or smaller than the from photographic plates guided by eye to stars passing through the gas and dust of the Sun. Herbig recognized that counterparts of charge-coupled device cameras on telescopes interstellar medium. these young stars, with masses several times controlled by computers. T Tauri stars became the topic of Herbig’s that of the Sun, ought to exist as well. After We would sometimes joke that we had mis- 1948 PhD thesis, A Study of Variable Stars in exhaustive studies, he published in 1960 a spent our lives; we could have stayed at the Nebulosity. His work supported the growing landmark paper describing the discovery pub while all the wonderful new hardware consensus that these stars are very young — and characterization of the more-massive and software was being developed, and then with their luminosity arising not from nuclear stars, now known as Herbig Ae and Be stars. have accomplished in a few years what had burning, but from the release of energy as Observations with telescopes, both ground- taken a lifetime. Of course, it is only in hind- the stars contract under gravity. Following based and spaceborne, have revealed that sight that there seems to be a shortcut in the decades-long systematic studies of T Tauri disks of debris can surround these stars, winding path to knowledge and discovery. ■ stars, Herbig synthesized, in 1962, all that was and that in some cases these disks harbour known at the time about the class in a now- newly formed planets and cometary bodies. Bo Reipurth is an astronomer at the famous paper, ‘The Properties and Problems As sites of planetary genesis, these Herbig University of Hawaii, and worked closely of T Tauri Stars and Related Objects’, which stars have in recent years become the subject with George Herbig in his later years. has become the foundation for the modern of intense study. e-mail: [email protected]