Nobel Prizes

in

Astrophysics & Cosmology

(A 12-part series)

Part 2 – Energy of Stars: Hans A Bethe

 

Finally, I got to carbon, and as you all know, in the case of carbon the reaction works out beautifully. One goes through six reactions, and at the end one comes back to carbon. In the process one has made four hydrogen atoms into one of helium.

-       Hans Bethe

The Nobel Prize is equated with the pinnacle of human achievement in both popular perception and professional esteem.  Since it was first awarded in 1901, the annual Nobel Prize for Physics has gone to major contributions in Astrophysics and Cosmology related fields only on eleven occasions. The first of these awardees (1967) was the German-American Hans Albrecht Bethe for his discoveries concerning energy production in stars.

 

How energy is produced in stars

The mechanism of generation of energy in stars has been one of the long-lasting problems for scientists, with a clear-cut understanding emerging only relatively recently. Hans Bethe made a crucial contribution towards this end.

Here is a summary of how our understanding of stellar energy generation developed:

1. 19th Century – Gravitational Contraction Hypothesis

Hermann von Helmholtz (1850s) and Lord Kelvin proposed that stars shine by slowly contracting under gravity (the Kelvin–Helmholtz mechanism), converting gravitational potential energy into heat.  This could power the Sun for only about 20 million years — far too short for geological and biological evidence of Earth’s age.

2. Turn of the 20th Century – Role of Radioactivity

The discovery of radioactivity (Becquerel, Curie, Rutherford) raised the idea that nuclear processes might provide long-lasting energy, but details were unclear.

3. 1920 – Hydrogen-Fusion Idea

Arthur Eddington suggested that fusion of hydrogen into helium could release vast energy, explaining the Sun’s longevity. This was based on Einstein’s mass–energy equivalence and astrophysical reasoning, but lacked a known nuclear reaction pathway.

Arthur Eddington

4. 1930s – Quantum Tunnelling and Fusion Pathways

George Gamow introduced a factor for quantum tunnelling, explaining how nuclear fusion can occur at stellar temperatures despite the strong Coulomb repulsion between the hydrogen nuclei.

George Gamow

Hans Bethe and Carl von Weizsäcker independently worked out the main stellar fusion cycles:

Proton–Proton (pp) chain (dominant in Sun-like stars), and CNO cycle (dominant in hotter, massive stars). This became the modern nuclear theory of stellar energy.

Hans Bethe              Carl Von Weizsacker

5. Experimental Confirmation

Solar neutrinos detected (1960s, Ray Davis) confirmed nuclear fusion in the Sun, though initial results showed the “solar neutrino problem”. This was resolved in the early 2000s by ‘neutrino oscillation’ theory (concerning the way neutrinos change flavour as they travel).

6. Present Day – Precision Models

Stellar structure and evolution models now integrate nuclear physics, plasma physics, and particle physics to predict luminosities, lifetimes, and nucleosynthesis with high precision, validated by helioseismology and astrophysical observations.

More on stellar energy generation

Stars generate energy through nuclear fusion, a process that converts mass into energy according to Einstein's equation E=mc². This energy counteracts gravitational collapse, maintaining hydrostatic equilibrium. In the 19th century, gravitational contraction was considered the Sun's energy source, but calculations showed it could only power the Sun for 20-30 million years—far less than geological evidence suggested for Earth's age. Nuclear fusion resolved this discrepancy by offering a mechanism capable of sustaining stellar luminosity for billions of years.

Nuclear fusion requires temperatures large enough to overcome the Coulomb repulsion between atomic nuclei (millions of kelvin) and density that ensures sufficient particle collisions. He quantum tunnelling effect allows fusion below classical temperature thresholds (critical for lower-mass stars).

The proton-proton chain

The Primary Energy Source for Main-Sequence Stars is the Proton-Proton (PP) Chain which is dominant in stars ≤1.3 solar masses (e.g., the Sun) The process is depicted in the diagram below:

The energy yield is 26.2 MeV per helium-4 nucleus. (A 10% temperature increase boosts energy by 46%.)

The CNO Cycle (Carbon-Nitrogen-Oxygen)

This is dominant in stars >1.3 solar masses. The process is depicted in the diagram below:

The energy yield: 25.0 MeV per helium-4 nucleus, with greater neutrino losses. (A 10% temperature increase boosts energy by 350%.)

Hans Bethe's Seminal Contributions to Stellar Nucleosynthesis

In the 1930s, the source of stellar energy remained unresolved. Bethe, building on Arthur Eddington's hypothesis (1920) and George Gamow's quantum tunnelling work, sought a nuclear mechanism to explain stellar longevity.

Bethe published two papers in in 1939. The first paper detailed the proton-proton chain for low-mass stars, and the second one described the CNO cycle for high-mass stars, where carbon isotopes catalyse hydrogen fusion. Both processes convert hydrogen to helium, with 0.7% of fused mass released as energy.

Carl Friedrich von Weizsäcker had independently proposed the CNO cycle in 1938, but Bethe's work was more comprehensive. Initially, Bethe thought the CNO cycle powered the Sun due to overestimated core temperatures (20 MK vs actual 15.7 MK). Later experiments confirmed the PP dominance in the Sun.

Bethe was awarded the Nobel Prize in 1967 “for discoveries concerning energy production in stars", the first Nobel award specifically for an achievement in Astrophysics/Cosmology.

Bethe’s broader legacy

Bethe's work established stars as dynamic systems with "life cycles" (birth, evolution, death). The famous B2FH paper (1957), though not co-authored by Bethe, had a major influence on elemental synthesis. Bethe's models predicted neutrino fluxes, later confirmed by detectors like Homestake (Raymond Davis, 2002 Nobel prize) .

Detection of solar neutrinos (e.g., Super-Kamiokande experiments in Japan) confirmed hydrogen fusion in the Sun, and opened up the field of Neutrino Astronomy. Supernova remnants (e.g., Cassiopeia A) show enriched heavy elements, validating models of explosive nucleosynthesis. In galactic chemical evolution, stellar fusion products are recycled into molecular clouds, shaping the abundance of elements across cosmic time.

Bethe's work remains foundational, illustrating how quantum physics and nuclear theory solve cosmic puzzles. As he noted: "Stars have a life cycle much like animals... to give back the material of which they are made, so that new stars may live”. His insights continue guiding research in astrophysics, from stellar interiors to the origin of elements.

Hans A Bethe (1906-2005) – A biographical sketch

Early Life and Education

Hans Bethe was born on July 2, 1906, in Strasbourg, then part of the German Empire (now France). His father, Albrecht Bethe, was a physiologist, and his mother, Anna Kuhn, came from a family of academics. Growing up in an intellectually stimulating environment, Bethe displayed an early aptitude for mathematics and physics. 

After completing his secondary education in Frankfurt, he enrolled at the University of Frankfurt in 1924 but soon transferred to the University of Munich to study under the renowned physicist Arnold Sommerfeld.  Under Sommerfeld’s guidance, Bethe thrived in the rapidly evolving field of quantum mechanics. 

Doctoral Work and Early Career 

Bethe earned his PhD in 1928 with a thesis on electron diffraction in crystals, a foundational contribution to solid-state physics. He then conducted postdoctoral research at Cambridge (with Ralph Fowler) and Rome (with Enrico Fermi), deepening his expertise in quantum theory and nuclear physics. 

In the early 1930s, Bethe worked at the *University of Tübingen and later at Cornell University (from 1935), where he became a leading figure in theoretical physics. His work during this period included: 

• The Bethe formula (1930): Calculating the energy loss of charged particles passing through matter. 
• Nuclear physics (1936–1938): Developing theories of nuclear reactions and deuteron formation. 
• Quantum electrodynamics (QED): Later contributing to understanding the Lamb shift (1947). 

World War II and the Manhattan Project 

With the rise of the Nazis, Bethe, of Jewish descent, emigrated to the USA in 1935. During WWII, he joined the Manhattan Project (1942–1945) at Los Alamos, where J Robert Oppenheimer appointed him head of the Theoretical Division. There, his key contributions included critical mass calculations for nuclear weapons, the implosion mechanism for the plutonium bomb (tested at Trinity and used on Nagasaki). 

Though he supported the initial atomic bomb project, he later opposed the hydrogen bomb, advocating for arms control. 

After WWII, Bethe returned to Cornell University, where he continued groundbreaking work in multiple fields: 

1. Nuclear Physics: 

   - Bethe-Weizsäcker formula (1935) describing nuclear binding energies. 

   - Theory of nuclear reactions (1936–1939) explaining how stars produce energy (though astrophysics was a major focus, he also contributed to terrestrial nuclear processes). 

2. Solid-State Physics: 

   - Work on electron behaviour in metals and semiconductors. 

3. Quantum Field Theory:

   - Contributions to renormalization in QED alongside Feynman and Schwinger. 

The Nobel Award

The Nobel Prize in Physics 1967 was awarded to Hans Albrecht Bethe "for his contributions to the theory of nuclear reactions, especially his discoveries concerning the energy production in stars"

Hans A Bethe receiving his Nobel Prize in 1967

Interestingly, Bethe was not only the first recipient of the Nobel Physics Prize for work on Astrophysics, but also the sole one, unlike most awards in recent times.

Later Years and Public Advocacy

Bethe remained scientifically active well into his 90s, publishing papers on neutrino physics and supernovae. Beyond research, he was deeply engaged in science policy. He opposed the hydrogen bomb (1950s), signing the Einstein-Szilard letter warning of nuclear proliferation, advocated for the Partial Nuclear Test Ban Treaty (1963), and supported peaceful uses of nuclear energy, including fusion research. 

Personal Life and Outlook 

Bethe married Rose Ewald (daughter of physicist Paul Ewald) in 1939, and they had two children. Known for his modesty, warmth, and collaborative spirit, he mentored many future Nobel laureates, including Richard Feynman. 

Despite his role in developing the atomic bomb, Bethe believed in scientific responsibility, arguing that physicists must consider the ethical implications of their work. He remained optimistic about humanity’s ability to use science for good, once stating:  "The most important thing is to keep trying—to never stop asking questions." 

Death and Legacy

Hans Bethe died on March 6, 2005, in Ithaca, New York, at age 98. His legacy includes: the Bethe Prize, awarded for outstanding contributions to astrophysics.  His life’s work had a lasting influence across nuclear, quantum, and solid-state physics. 

Footnote

The picture below tells a story of its own. Bethe had visited Chennai (then Madras) apparently as a guest of the MatScience Institute or IITM.

 

 

Nobel Prizes

in

Astrophysics & Cosmology

A Twelve Part Series

Part 1 - Overview

It is my express wish that in awarding the prizes no consideration be given to the nationality of the candidates, but that the most worthy shall receive the prize.

-         Alfred Nobel

The Nobel Prize is equated with the pinnacle of human achievement in both popular perception and professional esteem. Since it was first awarded in 1901, the annual Nobel Prize for Physics has gone to major contributions in Astrophysics and Cosmology related fields only on eleven occasions. This series of articles presents the life and work of each of the 26 awardees in these disciplines till now.

Introduction

Since their inception at the beginning of the last century, Nobel prizes have become symbols of the highest achievement in select fields of human endeavour – Physics, Chemistry, Physiology/Medicine, Literature and Peace.

This is the curtain raiser to a series of eleven articles to follow, outlining the history of the Nobel prize awarded to outstanding work related to Astronomy/Astrophysics/Cosmology within the broader field of Physics. The proposed series has been inspired by a book recently published in Kannada by Prof P Venkataramiah on ‘Nobel Laureates in the Family’ which I have reviewed in an earlier blog article here.  

These articles, one for each year of the award, will draw material from the Nobel archives and other sources, with some assistance from AI.  Each will present a detailed account of the award to the recipient/s, including an elucidation of the work involved from a physics perspective, and a biographical sketch.

Here is a summary of the eleven occasions when the award was made to work directly or indirectly related to Astronomy/Astrophysics/Cosmology:

	Year	Recipient/s	Nationality	Citation
1	1967	Hans A Bethe (1906-2005)	German-American	“For his contributions to the theory of nuclear reactions, especially his discoveries concerning the energy production in stars.”
2	1974	1) Martin Ryle (1918-1984)  2) Antony Hewish (1924-2021)	British    British	“For their pioneering research in radio astrophysics… Ryle for aperture-synthesis techniques, Hewish for a decisive role in the discovery of pulsars.”
3	1978	1) Arno A Penzias (1933-2024) 2) Robert W Wilson (1936- )	American   American	“For their discovery of cosmic microwave background radiation.”
4	1983	1) Subrahmanyan Chandrasekhar (1910-1995) 2) William A Fowler (1911-1995)	Indian-American    American	“For studies… important to the structure and evolution of the stars” (Chandrasekhar) and “for… nuclear reactions of importance in the formation of the chemical elements in the universe” (Fowler)
5	1993	1) Russell A Hulse (1950- ) 2) Joseph H Taylor Jr (1941- )	American   American	“For the discovery of a new type of pulsar, a discovery that has opened up new possibilities for the study of gravitation.”
6	2002	1) Raymond Davis Jr (1914-2006) 2) Masatoshi Koshiba (1926-2020) 3) Riccardo Giacconi (1931-2018)	American   Japanese   Italian-American	“For pioneering contributions to astrophysics, in particular for the detection of cosmic neutrinos” (Davis & Koshiba) and “for pioneering contributions to astrophysics, which have led to the discovery of cosmic X-ray sources” (Giacconi).
7	2006	1) John C Mather (1946- ) 2) George F Smoot (1945- )	American   American	“For their discovery of the blackbody form and anisotropy of the cosmic microwave background radiation.”
8	2011	1) Saul Perlmutter (1959- ) 2) Brian P Schmidt (1967- ) 3) Adam G Riess (1969- )	American   American-Australian American	“For the discovery of the accelerating expansion of the Universe through observations of distant supernovae.”
9	2017	1) Rainer Weiss (1932- ) 2) Barry C Barish (1936- ) 3) Kip S Thorne (1940- )	German-American American   American	“For decisive contributions to the LIGO detector and the observation of gravitational waves.”
10	2019	1) James Peebles (1935- ) 2) Michel Mayor (1942- ) 3) Didier Queloz (1966- )	Canadian-American Swiss   Swiss	Half to James Peebles “for theoretical discoveries in physical cosmology”; the other half jointly to Mayor & Queloz “for the discovery of an exoplanet orbiting a solar-type star.”
11	2020	1) Roger Penrose (1931- ) 2) Reinhard Genzel (1952- ) 3) Andrea Ghez (1965- )	British   German   American	Penrose: for work showing GR predicts black-hole formation; Genzel & Ghez: “for the discovery of a compact object (supermassive black hole) at the centre of our galaxy.”

This list excludes the following three awardees whose achievements relate only marginally to the areas of interest here:

1. Victor F Hess, Austrian-American physicist, who got the 1936 Nobel Prize in Physics ‘for his discovery of cosmic radiation’,
2. P M S Blackett, British physicist, who got the Nobel award in 1948 ‘for his contributions to his development of the Wilson Cloud Chamber method and its use in discovering cosmic ray interactions’, and
3. Hannes Alfven, Swedish Engineer and pioneer of magnetohydrodynamics and plasma physics, who got the Nobel award in 1970. 

Perhaps understandably, the list is dominated by one single nationality.

The Unlucky Lot

As it is now, the early 20th century was a golden age for astronomy, astrophysics, and cosmology, with many scientists making groundbreaking contributions that fundamentally reshaped our understanding of the universe. Several key figures did not receive a Nobel Prize in Physics despite their monumental work, often because their fields were not yet recognized by the Nobel Committee or because the scope of the prize was more traditionally focused on laboratory and theoretical physics. Here are some of the most deserving candidates:

1. Edwin Hubble (1889–1953) who discovered the expansion of the universe (Hubble's Law, 1929), providing the first observational evidence for the Big Bang theory and showed the existence of galaxies beyond the Milky Way.

[The Nobel Committee did not consider Astronomy a part of Physics at the time. Hubble justifiably aspired for a Nobel prize, but sadly none was awarded for Astronomy until the 1970s.]

2. Arthur Eddington (1882–1944) who provided experimental confirmation of Einstein's General Relativity during the 1919 solar eclipse, pioneered stellar structure theory (e.g., the Eddington limit for radiation pressure in stars), and also did some early work on nuclear fusion in stars. 

[His work was more theoretical/observational than experimental, and the Nobel Committee was slow to recognize Astrophysics.]

3. Georges Lemaître (1894–1966) who proposed the "primeval atom" theory (later called the Big Bang) in 1927–1933, and independently derived Hubble's Law before Hubble. 

[Cosmology was not yet a Nobel-recognized field, and his work was initially overshadowed by Hubble’s observations.]

4. Fred Hoyle (1915–2001) who formulated the theory of stellar nucleosynthesis, and was one of the authors of the path breaking B2FH (Margaret Burbridge, Geoffrey Burbridge, William Fowler and Fred Hoyle) paper on the origin of chemical elements.

[His outspoken opposition to the Big Bang theory may have been a dampener.]    

5. Cecilia Payne-Gaposchkin (1900–1979) who discovered that stars are primarily composed of hydrogen and helium (her 1925 thesis is one of the most important in astrophysics), and laid the foundation for stellar composition studies. 

[Gender bias in science was pronounced at the time; her work was initially dismissed by senior astronomers like Henry Norris Russell (who later acknowledged her findings).]

6. Henrietta Swan Leavitt (1868–1921) who discovered the period-luminosity relation for Cepheid variables (1912), allowing Hubble to measure galactic distances. 

[She was a "computer" (not a formally recognized scientist) at Harvard, and women were rarely considered for high honors. Nobel Prizes are also not given posthumously.]

7. Fritz Zwicky (1898–1974) who proposed the idea of dark matter (1933) through galaxy cluster dynamics, and pioneered supernova and neutron star research. 

[His ideas were too ahead of their time, and his abrasive personality may have hindered recognition.]

8. Karl Schwarzschild (1873–1916) who gave the first exact solution to Einstein's field equations (Schwarzschild metric, 1916), predicting black holes. 

[He died young, and black holes were not yet experimentally confirmed.]

9. Milton Humason (1891–1972) who provided critical spectroscopic data supporting Hubble's Law. 

[Seen as an observer rather than a theorist, and Nobel prizes were rarely given to non-PhDs at the time.]

10. Vesto Slipher (1875–1969) who first measured galactic redshifts (1912–1917), laying the groundwork for Hubble’s expansion discovery. 

[His work was overshadowed by Hubble’s later synthesis.]

11. Vera Rubin (1928–2016) who pioneered work on galactic rotation rates that produced the first widely accepted evidence for the existence of dark matter.

[The recently inaugurated Vera C Rubin Observatory in Chile is some consolation to her memory.]

12. Jocelyn Bell Burner (1943- ) who discovered the first radio pulsars in 1967.

[She was a mere ‘student’ at the time of the discovery and, as such, not a credible candidate for the award which went to her ‘teacher’ Anthony Hewish. However, the lucrative Breakthrough Prize bestowed upon her later was adequate compensation.]

These scientists reshaped our cosmic understanding, and many later prizes in astrophysics (e.g., for cosmic microwave background, exoplanets, black holes) owe a debt to their foundational work.

[It makes as much sense to write about these pioneers, who were unlucky not to get the award, as about the ones who did. I intend to feature them separately in a follow up series of articles.]

Alfred Nobel, the man behind the prizes

Alfred Bernhard Nobel (1833 – 1896) after whom these famous awards are known was a Swedish chemist, engineer, inventor, industrialist and philanthropist. His father, Immanuel Nobel, was an inventor and industrialist who eventually moved to Russia for work. Alfred received a broad education in natural sciences, literature, and languages. He was fluent in Swedish, Russian, French, English, and German. In Paris, Nobel studied chemistry under the famed chemist Théophile-Jules Pelouze, where he encountered Ascanio Sobrero, the discoverer of nitroglycerin—a highly volatile explosive compound.

In 1867, Nobel discovered how to stabilize nitroglycerin by combining it with absorbent materials like kieselguhr, creating "dynamite." This invention revolutionized construction, mining, and warfare. Eventually he was to hold 355 patents. Nobel's inventions extended to blasting caps, gelignite, and ballistite (a precursor to smokeless gunpowder).

Nobel established an industrial empire consisting of 90 armaments factories and laboratories in over 20 countries.

Despite the immense wealth he had amassed, Nobel led a relatively isolated personal life. He never married and was known to be introspective, a lover of literature, and a pacifist at heart. He maintained a long correspondence with Austrian pacifist Bertha von Suttner, who would later win the Nobel Peace Prize in 1905.

Nobel’s Will

One year before his death, Nobel signed a handwritten will at the Swedish–Norwegian Club in Paris. Its contents shocked his family and the public: He wrote in part: “The whole of my remaining realizable estate shall be dealt with in the following way: the capital... shall constitute a fund, the interest on which shall be annually distributed in the form of prizes to those who, during the preceding year, have conferred the greatest benefit on mankind…”. This requirement underwent major re-interpretations and adaptations in course of time.

Nobel specified five fields: Physics, Chemistry, Physiology or Medicine, Literature, and Peace (to the person or society that promotes peace and fraternity between nations).

[Note: The Nobel Prize in Economic Sciences was added later, in 1968, by the Swedish central bank.]

Nobel’s action led to a lot of unpleasant reactions and consequences. His relatives were unhappy, and the will was challenged in court. It took four years to resolve the attendant disputes and establish the Nobel Foundation in 1900.

Nobel’s handwritten will

Nobel specified that the Peace Prize be awarded by a Norwegian committee, while others were to be awarded by Swedish institutions—a symbolic gesture, as Sweden and Norway were in a union at the time.

The Nobel Prizes, first awarded in 1901, remain among the most prestigious awards in the world.

Nobel’s name, once associated with explosives, became a global symbol of peace, progress, and human achievement. He left about 31 million Swedish kronor (equivalent to over USD 250 million today) to fund the prizes.

Alfred Nobel was a paradoxical figure—an inventor of deadly explosives who chose to dedicate his fortune to honoring those who advance humanity. His actions led to an eventual global recognition of scientific, literary, and humanitarian excellence, and his name endures as a beacon of peace and progress.

Nobel Physics Awards

Physics was the prize area which Alfred Nobel mentioned first in his will from 1895. At the end of the nineteenth century, many people considered physics as the foremost of the sciences, and perhaps Nobel saw it this way as well. His own research was also closely tied to physics.

The Nobel Prize in Physics has been awarded 118 times to 227 Nobel Prize laureates between 1901 and 2024. John Bardeen is the only laureate who has been awarded the Nobel Prize in Physics twice, in 1956 and 1972. This means that a total of 226 individuals have received the Nobel Prize in Physics.

The Nobel Foundation, a private institution established in 1900, has ultimate responsibility for fulfilling the intentions in Alfred Nobel’s will. The main mission of the Nobel Foundation is to manage Alfred Nobel’s fortune in a manner that ensures a secure financial standing for the Nobel Prize over the long term and that the prize-awarding institutions are guaranteed independence in their work of selecting recipients.

The Foundation is also tasked with strengthening the Nobel Prize’s position by administering and developing the brands and intangible assets that have been built up during the Nobel Prize’s history, which spans well over a century.

The Nobel Foundation also strives to safeguard the prize-awarding institutions’ common interests and to represent the Nobel organization as a whole. In the past two decades a number of outreach activities have been developed with the aim of inspiring and disseminating knowledge about the Nobel Prize.

Who selects the Nobel Prize laureates?

In his last will and testament, Alfred Nobel specifically designated the institutions responsible for the prizes he wished to be established: The Royal Swedish Academy of Sciences for the Nobel Prize in Physics and Chemistry, Karolinska Institutet for the Nobel Prize in Physiology or Medicine, the Swedish Academy for the Nobel Prize in Literature, and a committee of five persons to be elected by the Norwegian Parliament (Storting) for the Nobel Peace Prize.

By the terms of Alfred Nobel’s will, the Nobel Prize in Physics has been awarded by the Royal Swedish Academy of Sciences since 1901.

The Royal Swedish Academy of Sciences in Stockholm

The Academy was founded in 1739 and has today about 440 Swedish and 175 foreign members. Membership in the Academy constitutes exclusive recognition of successful research achievements. The Academy appoints members of the Nobel Committee, the working body, for a three-year term.

Nomination to the Nobel Prize in Physics is by invitation only. The names of the nominees and other information about the nominations cannot be revealed until 50 years later.

The right to submit proposals for the award of a Nobel Prize in Physics is, by statute, enjoyed by: 

1.  Swedish and foreign members of the Royal Swedish Academy of Sciences;

2     Members of the Nobel Committee for Physics;

3      Nobel Prize laureates in physics;

4      Tenured professors in the Physical sciences at the universities and institutes of technology of Sweden, Denmark, Finland, Iceland and Norway, and Karolinska Institutet, Stockholm;

5       Holders of corresponding chairs in at least six universities or university colleges (normally, hundreds of universities) selected by the Academy of Sciences with a view to ensuring the appropriate distribution over the different countries and their seats of learning; and

6       Other scientists from whom the Academy may see fit to invite proposals. 

Decisions as to the selection of the scientific scholars referred to in paragraphs 5 and 6 above are taken each year before the end of the month of September.

The Royal Swedish Academy of Sciences is responsible for the selection of the Nobel Prize laureates in physics. The Academy appoints a working body, the Nobel Committee for Physics, which screens the nominations and presents a proposal for final candidates. The committee consists nominally of five voting members, but since many years, it also includes voting adjunct members. The Committee’s proposal is discussed in a larger body, the Physics Class of the Academy, who may suggest a modification or forward a different proposal to the Academy. Finally, additional proposals may be raised at the final Academy meeting. It is in principle possible to suggest that no prize be given the current year, but that is a seldom used choice.

Who is eligible for the Nobel Prize in Physics?

The candidates eligible for the physics prize are those nominated by qualified persons who have received an invitation from the Nobel Committee to submit names for consideration. No one can nominate himself or herself.

How are the physics laureates selected?

The nomination process for Nobel Prize laureates in physics.

© Nobel Prize Outreach. Ill. Niklas Elmehed

Below is a brief description of the process involved in selecting the Nobel Prize laureates in physics.

September – Nomination forms are sent out. The Nobel Committee sends out invitations for proposals for Nobel Prize nominees to thousands of specially selected university professors and other scholars, all around the globe. Members of the Royal Swedish Academy of Sciences as well as Nobel Prize laureates may also propose candidates. It is not possible to nominate oneself or to spontaneously submit a proposal without receiving an invitation.

February – Deadline for submission. The completed nomination forms must reach the Nobel Committee no later than 31 January of the following year. The Committee screens the nominations and selects the preliminary candidates.

March-May – Consultation with experts. The Nobel Committee sends the names of the preliminary candidates to specially appointed experts for their assessment of the candidates’ work.

June-August – Writing of the report. The Nobel Committee puts together the report with recommendations to be submitted to the Academy. The report is signed by all members of the Committee.

September – Committee submits recommendations. The Nobel Committee submits its report with recommendations on the final candidates to the members of the Academy. The report is discussed at two meetings of the Physics Class of the Academy.

October – Nobel Prize laureates are chosen. In early October, the Academy selects the Nobel Prize laureates in physics through a majority vote. The decision is final and without appeal. The names of the Nobel Prize laureates are then announced.

December – Nobel Prize laureates receive their prize. The Nobel Prize award ceremony takes place on 10 December in Stockholm, where the Nobel Prize laureates receive their Nobel Prize, which consists of a Nobel Prize medal and diploma, and a document confirming the prize amount.

Are the nominations made public?

The statutes of the Nobel Foundation restrict disclosure of information about the nominations, whether publicly or privately, for 50 years. The restriction concerns the nominees and nominators, as well as investigations and opinions related to the award of a prize.

10 December – A magic date

Since 1901, the Nobel Prizes have been presented to Nobel Prize laureates at ceremonies on 10 December, the anniversary of Alfred Nobel’s death.

As stipulated in Nobel’s will, the Nobel Prizes in Physics, Chemistry, Physiology or Medicine and Literature are awarded in Stockholm, Sweden, while the Nobel Peace Prize is awarded in Oslo, Norway.

A typical Nobel awards ceremony in Stockholm, Sweden on Dec 10

Looking forward

By now the selection process for the 2025 awards should be well under way, with the names of the winners scheduled to be announced early in October. Considering that Astrophysics and Cosmology continue to be at the cutting edge of current scientific research, another award in this field his highly probable. If it happens, the number of my blog articles in the present series will swell by one!