Michiel Baldur Maximiliaan van der Klis (born 9 June 1953) is a Dutch astronomer best known for his work on extreme 'pairings' of stars called

X-ray binaries An X-ray (also known in many languages as Röntgen radiation) is a form of high-energy electromagnetic radiation with a wavelength shorter than those of ultraviolet rays and longer than those of gamma rays. Roughly, X-rays have a wavelengt ...

, more particularly his explanation of the occurrence of

quasi-periodic oscillations In X-ray astronomy, quasi-periodic oscillation (QPO) is the manner in which the X-ray light from an astronomical object flickers about certain frequencies. In these situations, the X-rays are emitted near the inner edge of an accretion disk in w ...

(QPOs) in these systems and his co-discovery of the first millisecond X-ray

pulsar A pulsar (''pulsating star, on the model of quasar'') is a highly magnetized rotating neutron star that emits beams of electromagnetic radiation out of its Poles of astronomical bodies#Magnetic poles, magnetic poles. This radiation can be obse ...

. In the 1980s he gained worldwide fame with his investigation of QPOs. His revolutionary discoveries have had an enormous impact in his field of research; in effect, they have made it what it is today. Van der Klis pioneered special mathematical analysis techniques that are now regarded as the “gold standard” within his discipline.

Research

Van der Klis's research focuses on

, pairs of stars orbiting each other that emit

X-ray An X-ray (also known in many languages as Röntgen radiation) is a form of high-energy electromagnetic radiation with a wavelength shorter than those of ultraviolet rays and longer than those of gamma rays. Roughly, X-rays have a wavelength ran ...

radiation. Some

binary star system A binary star or binary star system is a Star system, system of two stars that are gravity, gravitationally bound to and in orbit around each other. Binary stars in the night sky that are seen as a single object to the naked eye are often resolved ...

s contain a

compact object In astronomy, the term compact object (or compact star) refers collectively to white dwarfs, neutron stars, and black holes. It could also include exotic stars if such hypothetical, dense bodies are confirmed to exist. All compact objects have a ...

like a

neutron star A neutron star is the gravitationally collapsed Stellar core, core of a massive supergiant star. It results from the supernova explosion of a stellar evolution#Massive star, massive star—combined with gravitational collapse—that compresses ...

or a

black hole A black hole is a massive, compact astronomical object so dense that its gravity prevents anything from escaping, even light. Albert Einstein's theory of general relativity predicts that a sufficiently compact mass will form a black hole. Th ...

. By studying the dynamics of materials in the vicinity of such objects one can learn about their

mass Mass is an Intrinsic and extrinsic properties, intrinsic property of a physical body, body. It was traditionally believed to be related to the physical quantity, quantity of matter in a body, until the discovery of the atom and particle physi ...

radius In classical geometry, a radius (: radii or radiuses) of a circle or sphere is any of the line segments from its Centre (geometry), center to its perimeter, and in more modern usage, it is also their length. The radius of a regular polygon is th ...

and

rotational speed Rotational frequency, also known as rotational speed or rate of rotation (symbols ''ν'', lowercase Greek nu, and also ''n''), is the frequency of rotation of an object around an axis. Its SI unit is the reciprocal seconds (s−1); other com ...

. Moreover, this kind of research provides a testing ground for

cosmology Cosmology () is a branch of physics and metaphysics dealing with the nature of the universe, the cosmos. The term ''cosmology'' was first used in English in 1656 in Thomas Blount's ''Glossographia'', with the meaning of "a speaking of the wo ...

and

general relativity General relativity, also known as the general theory of relativity, and as Einstein's theory of gravity, is the differential geometry, geometric theory of gravitation published by Albert Einstein in 1915 and is the current description of grav ...

. Van der Klis made a number of breakthrough discoveries. In 1984 he discovered the first type of QPOs (quasi-periodic oscillations of the X-ray emission) of compact stars while he was working with ESA's EXOSAT satellite to study the strongest X-ray sources near the centre of the

Milky Way The Milky Way or Milky Way Galaxy is the galaxy that includes the Solar System, with the name describing the #Appearance, galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars in other arms of the galax ...

. One of his achievements is the explanation in 1985 why

s emitted from binary systems do not come in steady pulses (like the radiowaves emitted by pulsars), but in short irregular bursts. His studies in the years 1984-1987 clarified the principles for classifying the several hundreds of strong X-ray sources known to exist in our

Galaxy A galaxy is a Physical system, system of stars, stellar remnants, interstellar medium, interstellar gas, cosmic dust, dust, and dark matter bound together by gravity. The word is derived from the Ancient Greek, Greek ' (), literally 'milky', ...

. In the 1990s, he and his research group, including Rudy Wijnands, discovered the first millisecond X-ray pulsar in a binary system, SAX J1808.4-3658, a neutron star spinning around its axis more than 400 times per second. The discovery of this superfast spinning neutron star attracted great international attention.

Academic career

Van der Klis obtained his PhD at University of Amsterdam in 1983 working on observations of X-ray binaries. For a while he worked at the

ESA The European Space Agency (ESA) is a 23-member international organization devoted to space exploration. With its headquarters in Paris and a staff of around 2,547 people globally as of 2023, ESA was founded in 1975 in the context of European ...

lab

ESTEC The European Space Research and Technology Centre (ESTEC) is the European Space Agency's main technology development and test centre for spacecraft and space technology. It is situated in Noordwijk, South Holland, in the western Netherlands, alth ...

in Noordwijk. In 1989 he returned to the University of Amsterdam as an associate professor and was made full professor of

Astronomy Astronomy is a natural science that studies celestial objects and the phenomena that occur in the cosmos. It uses mathematics, physics, and chemistry in order to explain their origin and their overall evolution. Objects of interest includ ...

in 1993. Since 2002 he is an elected member of the

Royal Netherlands Academy of Arts and Sciences The Royal Netherlands Academy of Arts and Sciences (, KNAW) is an organization dedicated to the advancement of science and literature in the Netherlands. The academy is housed in the Trippenhuis in Amsterdam. In addition to various advisory a ...

(KNAW) and since 2003 also of the

Koninklijke Hollandsche Maatschappij der Wetenschappen The ''Koninklijke Hollandsche Maatschappij der Wetenschappen'' (Royal Holland Society of Sciences and Humanities), located on the east side of the Spaarne in downtown Haarlem, Netherlands, was established in 1752 and is the oldest society for the ...

(KHMW). Since 2005 he is Director of the Astronomical Institute Anton Pannekoek of the

University of Amsterdam The University of Amsterdam (abbreviated as UvA, ) is a public university, public research university located in Amsterdam, Netherlands. Established in 1632 by municipal authorities, it is the fourth-oldest academic institution in the Netherlan ...

and Chair of the Netherlands Research School for Astronomy (NOVA).

Honors and awards

Van der Klis received a number of awards for his pioneering research, including the

Bruno Rossi Prize The Bruno Rossi Prize is awarded annually by the High Energy Astrophysics division of the American Astronomical Society "for a significant contribution to High Energy Astrophysics, with particular emphasis on recent, original work". Named after as ...

(1987), the most important international distinction awarded in high-energy

astrophysics Astrophysics is a science that employs the methods and principles of physics and chemistry in the study of astronomical objects and phenomena. As one of the founders of the discipline, James Keeler, said, astrophysics "seeks to ascertain the ...

, and the

Spinoza Prize The Spinoza Prize () is an annual award of 1.5 million euro prize money, to be spent on new research given by the Dutch Research Council (NWO). The award is the highest scientific award in the Netherlands. It is named after the philosopher Baruc ...

(2004). On April 27, 2010, the

(KNAW) awarded an Academy Professorship to him. The international review committee noted: "He is a world leader in the X-ray radiation of compact objects and has formulated an intriguing connection between black holes and neutron stars, the two most extreme objects in the universe. He and his research group also discovered the first X-ray pulsar with a rotation speed of four hundred revolutions per second." He was elected a Legacy Fellow of the

American Astronomical Society The American Astronomical Society (AAS, sometimes spoken as "double-A-S") is an American society of professional astronomers and other interested individuals, headquartered in Washington, DC. The primary objective of the AAS is to promote the adv ...

in 2020.

Awards

*1987

*1990

COSPAR The Committee on Space Research (COSPAR) was established on October 3, 1958 by the International Council for Science, International Council for Scientific Unions (ICSU) and its first chair was Hildegard Korf Kallmann-Bijl. Among COSPAR's objec ...

Zel'dovich Medal *1991 NWO Pionier grant *1998 Visiting

Miller A miller is a person who operates a mill, a machine to grind a grain (for example corn or wheat) to make flour. Milling is among the oldest of human occupations. "Miller", "Milne" and other variants are common surnames, as are their equivalents ...

Professorship Award, University of California Berkeley *2004

*2010

KNAW The Royal Netherlands Academy of Arts and Sciences (, KNAW) is an organization dedicated to the advancement of science and literature in the Netherlands. The academy is housed in the Trippenhuis in Amsterdam. In addition to various advisory a ...

Academy Professorship

References

* Jury report for his 2004 Spinozapremie. * * Jury report for his 2010 KNAW nomination.

External links

Link to all papers by Michiel van der Klis on the ArXivLink to the NARCIS scientific portal
{{DEFAULTSORT:Klis, Michiel Van Der 1953 births Living people 20th-century Dutch astronomers University of Amsterdam alumni Academic staff of the University of Amsterdam Members of the Royal Netherlands Academy of Arts and Sciences Scientists from The Hague Spinoza Prize winners Fellows of the American Astronomical Society 21st-century Dutch astronomers