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Wilhelm Heinrich Walter Baade (Schröttinghausen, Preußisch Oldendorfnow, March 24, 1893 – June 25, Göttingen1960) was a German astronomer. He emigrated to theUnited Statesin 1931 . B in 1952 made known that the distance to the Andromeda Galaxy more than twice as great as previously thought. It also doubled the distances and the age of the universe, which made the big bang hypothesis more plausible. He was in the 1920s also known as discoverer of numerous asteroids.

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[hide]*1 early life

Life Course[Edit]Edit

B Schröttinghausen in Westphalia was born as a son of the teacher Konrad Baade. The family later moved to Herford and from 1913 Baade studied astronomy at the University of Göttingen. Preparing his doctorate(1919) on the spectrum and the trajectory of Beta Lyrae was temporarily interrupted when he starting from 1917 until the end of the first world war, worked for the Institute for aero dynamism. At the same time he worked as an Assistant to the mathematician Felix Klein.

B started his career as an astronomer at the Observatory of the University of Hamburg under the direction of Richard Schorr, initially as Assistant, starting from 1927 as an independent researcher. In the aftermath of the first world war German astronomers could not join the International Astronomical Union, whereby B at that time could not live up to his ambition to one of the great American observatories to go to work. From 1920to 1931 , he worked with the 1 meter-reflector telescope in Bergedorf (Hamburg). His research concerned above all cometsplanets and asteroids. At that time he discovered a series of asteroids and Comet, later known under the name Comet Baade. His research expanded further forward to stars in the galactic halo and the spiral nebulae.

In 1931 he could his dream come true and emigrate to the United States to work on the Mount Wilson Observatory in California. In 1948 he moved to the new Palomar Observatory where he continued his astronomical studies and following the major events until his retirement in 1958. He still worked half a year at the Mount Stromlo Observatory in Canberra, Australia, where he was especially devoted to the further study of the RR Lyrae variable stars. In 1959 he returned to Germany, where he was distinguished as Gauss professor in Göttingen and there prepared a publication that would provide an overview of its observations of recent years. He died there in 1960 as a result of complications after hip surgery.

Research[Edit]Edit

Pulsation Theory[Edit]Edit

In 1926 published B a method of pulsation theory of periodic variable stars of type delta Cephei to prove. Important astronomers such as Anton Pannekoek and Fred Hoyle wrote the periodic changes in the brightness of Cepheid to eclipses in a binary starHarlow Shapley showed in 1914 that there definitely was a radial pulsation of a star, but the discussion was only terminated with the B-method, in 1946, further developed by Adriaan Jan Wagner.

Supernovae[Edit]Edit

At the Mount Wilson Observatory Baade studied the phenomenon of novae. That there is a separate class of extremely bright novae existed already in 1920 , was put forth by Knut Lundmark. B studied the light curves of the supernovae that Fritz Zwicky in Palomar had discovered. Together they found other supernovae in other galaxies. In some lectures in 1931 in the California Institute of Technology (Caltech) they called this phenomenon for the first time "Supernova". Baade and Zwicky In 1934 stated a supernova as an explosion of a normal star, which collapses to a neutron star. Most of the cosmic radiation would according to their joint article from 1934 supernovae and Cosmic Rays come from supernovae.

One of the many studies that Baade are accuracy as an observer and scientist all namesake, is his research on the nova from 1604 (SN 1604). B reconstruct the light curve and the object could identify as a supernova. He discovered the remains of the explosion thanks to the pictures that could be made with the 2.5 meter-Hooker telescope. He has published about this in 1943.

Star Populations[Edit]Edit

During the Second World War was B the only scientist on Mount Wilson, because most other members of the staff were involved in military research work. B itself, still German, if do not participate and was initially under house arrest. However, he could convince the Government that he formed no security risk and a few months later his curfew lifted. As a result, he could completely have the telescope. In addition, Los Angelesbecause of the war was darkened, whereby also the conditions were optimal for observation.

B could now freely the center of the Andromeda Galaxy and its satellite galaxies M32 and NGC 205 therein could study and individual stars. Before the war he was involved with Edwin Hubble also already in the "solve" to individual stars of the galaxies that Shapley had discovered in 1938. This brought Baade in 1944 to the concept that Star were to be divided into two populations. The type I population was mainly characterized by blue (young people) stars in spiral galaxies, the type II population by the weaker light red (older) stars in elliptical galaxies. These initial format he later refined even further. This was an important impetus to the study of the evolution of stars and galaxies.

Distances in the universe[Edit]Edit

During the war studied B variable RR Lyrae stars, which could be measured as cepheïdeachtige star also distances by Henrietta Leavitt and Williamina Fleming was demonstrated. The ideal sea conditions would enable him to find that also in the Andromeda galaxy that way previous distance measurements based on the variable to be able to refine Cepheids . Sadly the RR Lyrae stars are not found with 2.5 meter-Hooker telescope that him when was available.

After the inauguration of the new 5 meter Hale telescope on Mount Palomar in 1948 -, Baade resumed his quest, but could not perceive there again. The only explanation was that Andromeda was much further away than initially thought. There was an error in the cepheïdenafstandsschaal because there is no unconscious mind held that the visible Cepheid by Andromeda Galaxy and perhaps other Star types were. Also at the Cepheids and Cepheid, there were bright population I-light weaker population II Cepheid to exist, the first type four times brighter than the second.

Baade suggested so two luminosity-period and revalued relationships in this way the distances in the universe. At equal flight speeds of the galaxies (it was nothing changed), but also doubled the time elapsed distance doubled, was since the big bang (see Hubble constant). In 1952 announced Baade on the Assembly of the International Astronomical Union in Rome that the time scale for the universe now of about 1.8 billion years had to be extended to about 3.6 billion years.

Identification of radio sources[Edit]Edit

In 1954 Walter Baade could settle the discussion created between Martin Ryle and Thomas Gold. Question was whether the radio sources discovered stars were within our Galaxy or individual galaxies. Martin Ryle thought the stars were radioastronomie group and with his University of Cambridge on the dozens of cosmic radio sources can be located, including the radio source Cygnus A. This allowed the 5 meter-Baade telescope at Palomar Observatory to determine the focus and optical counterpart of it. It turned out to indeed be a Galaxy and B could show that most radio sources were galaxies.

Discovered celestial bodies[Edit]Edit

Baade named after him in 1922 discovered the Comet Baade. In addition he discovered 10 asteroids.

Asteroids discovered: 10
930 Westphalia 10 March1920
934 Thüringia 15 August1920
5656 Oldfield 8 October1920
944 Hidalgo 31 October1920
966 Muschi 9 november1921
967 Helionape 9 november1921
1036 Ganymede 23 October1924
1103 Sequoia 9 november1928
(7448) 1948 AA 14 January1948
1566 Icarus 27 June1949

Awards[Edit]Edit

named after him[Edit]Edit

  • Walter Baade telescope (6.5 m), one of the two Magellan telescopes in Chile.
  • B-method, for calibration of the cepheïde period Wesselinck-lichtkracht relationship
  • Comet B
  • (1501) Baade, asteroid
  • B crater, crater on the Moon
  • Vallis Baade, Valley on the Moon

Publications[Edit]Edit

  • Baade, Walter, Über eine Möglichkeit, Pulsationstheorie der Veränderlichen zu prüfen δ Cephei-which, Astr. Nach. 228, 359 (1926).
  • Baade, w. & f. Zwicky, Cosmic Rays from Super novae, Proceedings of the National Academy of Sciences of the United States of America (proc. NAT. ACAD. Sci) 20, 259-63 (1934).
  • Baade, Walter & f. Zwicky, On Super-Novae, proc. NAT. ACAD. Sci. 20, 254-59 (1934).
  • Baade, Walter, The Crab Nebula, Astrophysical Journal (AP. j.) 96, 188 (1942).
  • Baade w., The resolution of Messier 32, NGC 205, and the central region of the Andromeda nebula, AP. j. 100 137-146 (1944).
  • Baade, Walter, A Revision of the Extra-Galactic Distance Scale, trans. IAU 8, 397-98 (1952).
  • Baade, w. & r. Minkowski, Identification of the Radio Sources in Cassiopeia, Cygnus A and Puppis A, AP. j., vol. 119, p. 206-214 (1954).
  • Baade w., The period-luminosity relation of the Cepheids PASP 68 5-16 (1956).