Adriaan Van Maanen
Encyclopedia
Adriaan van Maanen was a Dutch
–American
astronomer
.
Van Maanen, born into a well-to-do family in Friesland
, studied astronomy at the University of Utrecht (earning his Ph.D. in 1911) and worked briefly at the University of Groningen
. In 1911, he came to the United States
to work as a volunteer in an unpaid capacity at Yerkes Observatory
. Within a year he got a position at the Mount Wilson Observatory
, where he remained active until his death in 1946.
He discovered Van Maanen's star
.
He is well known for his astrometric measurements of internal motions in spiral nebulae. Being of the belief that nebulae were local, stellar and gaseous systems that existed in our galaxy, his measurements came to be at odds with Edwin Hubble
's discovery that the Andromeda Nebula
and other spiral nebulae were extragalactic objects. The speed at which he calculated the nebulae to rotate would have had the Cepheid stars, that Hubble had used to calculate the distance to the spirals, moving at speeds faster than that of light. In 1935, it was decided that since Hubble's calculations of extragalactic Cepheid distances were correct van Maanen's astrometric measurements had to be incorrect.
The origin of Van Maanen's measurement errors where that Van Maanen used a stereo blink comparator comparing new plates with plates some 10–20 years old, and by blinking between those two plates he could detect small discrepancies on the positions of the objects. His reference objects were the field stars fairly near the edge of the plates. However he didn't consider that due to optical effects these stars had been smeared out a little towards the edges, slightly different for the two plates. This caused systematic errors resulting in apparent movements which weren't real.
Another possible explanation is that Van Maanen simply saw what he had been trained to see for years. The belief that the "spiral nebulae" were relatively nearby and therefore ought to have a quite detectable rotation was quite widespread in the early 1900s and therefore very hard to ignore. Van Maanen then simply found what he was looking for. This does not, however, explain supposedly coroborating findings from Mount Wilson, Lowell Observatory, Russia, and the Netherlands.
Netherlands
The Netherlands is a constituent country of the Kingdom of the Netherlands, located mainly in North-West Europe and with several islands in the Caribbean. Mainland Netherlands borders the North Sea to the north and west, Belgium to the south, and Germany to the east, and shares maritime borders...
–American
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
astronomer
Astronomer
An astronomer is a scientist who studies celestial bodies such as planets, stars and galaxies.Historically, astronomy was more concerned with the classification and description of phenomena in the sky, while astrophysics attempted to explain these phenomena and the differences between them using...
.
Van Maanen, born into a well-to-do family in Friesland
Friesland
Friesland is a province in the north of the Netherlands and part of the ancient region of Frisia.Until the end of 1996, the province bore Friesland as its official name. In 1997 this Dutch name lost its official status to the Frisian Fryslân...
, studied astronomy at the University of Utrecht (earning his Ph.D. in 1911) and worked briefly at the University of Groningen
University of Groningen
The University of Groningen , located in the city of Groningen, was founded in 1614. It is one of the oldest universities in the Netherlands as well as one of its largest. Since its inception more than 100,000 students have graduated...
. In 1911, he came to the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
to work as a volunteer in an unpaid capacity at Yerkes Observatory
Yerkes Observatory
Yerkes Observatory is an astronomical observatory operated by the University of Chicago in Williams Bay, Wisconsin. The observatory, which calls itself "the birthplace of modern astrophysics," was founded in 1897 by George Ellery Hale and financed by Charles T. Yerkes...
. Within a year he got a position at the Mount Wilson Observatory
Mount Wilson Observatory
The Mount Wilson Observatory is an astronomical observatory in Los Angeles County, California, United States. The MWO is located on Mount Wilson, a 5,715 foot peak in the San Gabriel Mountains near Pasadena, northeast of Los Angeles...
, where he remained active until his death in 1946.
He discovered Van Maanen's star
Van Maanen's star
Van Maanen's star is a white dwarf star. Out of the white dwarfs known, it is the third closest to the Sun, after Sirius B and Procyon B, in that order, and the closest known solitary white dwarf...
.
He is well known for his astrometric measurements of internal motions in spiral nebulae. Being of the belief that nebulae were local, stellar and gaseous systems that existed in our galaxy, his measurements came to be at odds with Edwin Hubble
Edwin Hubble
Edwin Powell Hubble was an American astronomer who profoundly changed the understanding of the universe by confirming the existence of galaxies other than the Milky Way - our own galaxy...
's discovery that the Andromeda Nebula
Andromeda Galaxy
The Andromeda Galaxy is a spiral galaxy approximately 2.5 million light-years from Earth in the constellation Andromeda. It is also known as Messier 31, M31, or NGC 224, and is often referred to as the Great Andromeda Nebula in older texts. Andromeda is the nearest spiral galaxy to the...
and other spiral nebulae were extragalactic objects. The speed at which he calculated the nebulae to rotate would have had the Cepheid stars, that Hubble had used to calculate the distance to the spirals, moving at speeds faster than that of light. In 1935, it was decided that since Hubble's calculations of extragalactic Cepheid distances were correct van Maanen's astrometric measurements had to be incorrect.
The origin of Van Maanen's measurement errors where that Van Maanen used a stereo blink comparator comparing new plates with plates some 10–20 years old, and by blinking between those two plates he could detect small discrepancies on the positions of the objects. His reference objects were the field stars fairly near the edge of the plates. However he didn't consider that due to optical effects these stars had been smeared out a little towards the edges, slightly different for the two plates. This caused systematic errors resulting in apparent movements which weren't real.
Another possible explanation is that Van Maanen simply saw what he had been trained to see for years. The belief that the "spiral nebulae" were relatively nearby and therefore ought to have a quite detectable rotation was quite widespread in the early 1900s and therefore very hard to ignore. Van Maanen then simply found what he was looking for. This does not, however, explain supposedly coroborating findings from Mount Wilson, Lowell Observatory, Russia, and the Netherlands.
External links
- Angular Rotations of Spiral Nebulae, Hubble, E., ApJ, 81, 334 (1935) – NADS
- Internal Motions in Spiral Nebulae, Van Maanen, A., ApJ, 81, 336 (1935) – NADS
- Adriaan van Maanen and internal motions in spiral nebulae: A historical review, Quarterly Journal of the Royal Astronomical Society, Vol. 13, 1972
- Adriaan van Maanen on the significance of Internal Motions in Spiral Nebulae, Hetherington, N.S., J Hist Astron, 5. 52 (1974) – NADS
- On Spiral Nebulae, van Maanen et al. Chronological bibliography of articles on astrometrical measurements of spiral nebulae.