Key Figures in Astronomy

As a PhD student at Cambridge University, Jocelyn Bell Burnell discovered the first pulsar. She used the Interplanetary Scintillation Array, which she also helped to set up. The discovery led to a Nobel Prize in 1974. However, this went not to Bell Burnell but to her supervisor Antony Hewish and to Martin Ryle. The radio astronomer became a member of the Royal Society in 2003 and was appointed Dame Commander of the Order of the British Empire by Queen Elizabeth II four years later. For her discovery of the first pulsar, Bel Burnell received the 2018 Special Breakthrough Prize in Fundamental Physics, the prize money of which she is donating to women, ethnic minorities, and refugees who are underrepresented as physics scholarship recipients.

Albert Einstein is one of the most important (theoretical) physicists. With his research on space, time, matter, and gravity, he changed the worldview that had been established by Newton. He became world famous through his publications on the theory of special relativity (1905) and the theory of general relativity (1915). Einstein received the Nobel Prize in 1922 for his work on the interaction of photons with matter.

 Stephen Hawking was a British theoretical physicist and one of the most well-known scientists of our time. He focused mainly on general relativity and quantum gravity. He became particularly famous for his work on black holes, showing that they are not completely “black” but emit radiation — known as Hawking radiation. With this, he was the first to link the laws of quantum physics with gravity. In addition to his scientific work, Hawking made complex topics accessible to a broad audience through popular science books such as „A Brief History of Time“. Despite his severe illness, ALS, he remained scientifically active until his death in 2018 and inspired people all over the world.

„I do not think that the wireless waves I have discovered will have any practical application.“ – Heinrich Hertz

German physicist Heinrich Hertz was quite mistaken! Unfortunately, he did not live to see the practical application of radio waves. In 1886, Hertz was the first person to successfully generate electromagnetic waves experimentally and transmit them from a transmitter to a receiver. He thus proved the existence of electromagnetic waves, which had been predicted 22 years earlier by Scottish physicist James Clerk Maxwell. Based on this discovery, the physical quantity of frequency was given the unit hertz (Hz) in 1933.

British physicist Stanley Hey is seen as a pioneer of radio astronomy. While working as a radar researcher for the British military, he discovered radio waves from sunspots in 1942. Four years later, he and some colleagues discovered the radio galaxy Cygnus A. Hey worked successfully on developing radio astronomy from the metre band to the centimetre band and also built an interferometer using two radio telescopes. Furthermore, the asteroid (22473) Stanleyhey is named in his honour.

Just over 100 years ago, American astronomer Edwin Hubble carried out distance measurements at Mount Wilson Observatory in California—at that time the largest reflecting telescope in the world—and proved that there are other galaxies in the universe besides the Milky Way. He also studied the expansion of the universe and discovered a correlation between the redshift of starlight and its distance. From his observations, he concluded that astronomical objects move away from us faster the further away they are. Due to his groundbreaking scientific work, the expansion rate of the universe (Hubble constant) and a space telescope, among other things, were named after him.

In the 1930s, the telephone company Bell Phone Laboratories was struggling with interference signals in the shortwave band and commissioned Karl Guthe Jansky to find the source. Jansky built a rotating directional antenna in a field, discovered a noise signal with it, and determined that the maximum signal shifted by four minutes each day. The conclusion was that the source of the radio signal must be cosmic in origin and located outside the solar system. In addition, the signal peaked whenever the antenna was pointed at the constellation „Sagittarius“. Today we know that the center of the Milky Way lies in this direction. Karl Guthe Jansky is thus considered the father of radio astronomy.

George Lemaitre was a Belgian theologian and astrophysicist. His primary interest was the expansion of the universe, and in this context he developed ideas about the origin of the universe that led to the Big Bang theory. There were many critics, including Einstein, but Lemaitre was able to convince him personally of his theory many years later.

In 1864, Scottish physicist James Maxwell predicted the existence of electromagnetic waves, which Heinrich Hertz was able to confirm experimentally 22 years later. Since radio waves are also electromagnetic waves, Maxwell thus indirectly made a fundamental contribution to the later development of radio astronomy. He developed the so called Maxwell's equations, which were fundamental to various fields of physics. Maxwell was also able to proof that electromagnetic waves travel at a constant speed - the speed of light.

At the end of the 19th century, there was a problem: the theoretical predictions for the radiation emitted by a black body (an ideal radiator) did not match the experimental results. German physicist Max Planck attempted to solve this problem by combining thermodynamics and electromagnetic theory. He proposed the theory that energy is not transferred in a continuous flow, but in small, fixed “ packages” or quanta. This idea contradicted the prevailing classical theories of energy transfer at the time. Planck introduced a new physical constant, known as Planck's quantum of action, to describe his theory. Using this constant, he formulated the famous equation E = h*f and Planck's law of radiation, which made it possible to correctly calculate the radiation of a black body. This equation describes the relationship between the energy of a light particle and the frequency of light.

Grote Reber was a pioneer of radio astronomy who built the first telescope specifically designed for radio astronomy. In 1937, he built a nine-meter parabolic antenna at his own expense and set it up in his garden. He used it to make the first survey of the entire sky in radio and discovered that there are several other strong radio sources in addition to the Milky Way.

Maarten Schmidt was a Dutch astronomer who continued his scientific work in the USA after completing his doctorate. He was particularly interested in quasars and discovered through spectral analysis that these objects have a high redshift and are located in the distant universe. He is also the co-founder of the Schmidt-Kennicutt law, which describes the relationship between gas density in a galaxy and the star formation rate there.

The German astronomer and physicist Karl Schwarzschild is one of the pioneers of modern astrophysics. Among other things, Schwarzschild worked on the theory of relativity and laid important foundations for research into black holes. For this reason, some properties of these objects have been named after him – the Schwarzschild radius is particularly well known. This is a measure of the size of a spherical black hole. Within the Schwarzschild radius, nothing – not even light – can escape the strong gravity of a black hole.