Tim Bedding

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Tim Bedding
Born (1966-07-21) 21 July 1966 (age 57)
NationalityAustralian
OccupationAstrophysicist

Timothy R. Bedding FAA (born 21 July 1966) is an Australian astronomer known for his work on asteroseismology, the study of stellar oscillations. In particular, he contributed to the first detections of solar-like oscillations in stars such as eta Bootis, beta Hydri and alpha Centauri. [1] He also led the discovery, using data from the Kepler space telescope, that red giants oscillate in mixed modes that are directly sensitive to the core properties of the star and can be used to distinguish red giants burning helium in their cores from those that are still only burning hydrogen in a shell. [2]

Bedding has worked in the School of Physics at the University of Sydney since 1995 [3] and was Head of School from 2012 to 2018. [4] He received the University's Excellence in Teaching Award in 1999 and was appointed as a Payne Scott Professor in 2019. [5]

The asteroid 231470 Bedding is named after him. [6]

He played on the Australian team in the 1990 Ultimate Frisbee World Championships in Oslo, Norway. [7]

In May 2020 Bedding was elected Fellow of the Australian Academy of Science. [8] In 2022, he was awarded an ARC Laureate Fellowship to use asteroseismology to measure the ages of stars.

See also

Related Research Articles

<span class="mw-page-title-main">Main sequence</span> Continuous band of stars that appears on plots of stellar color versus brightness

In astronomy, the main sequence is a classification of stars which appear on plots of stellar color versus brightness as a continuous and distinctive band. Stars on this band are known as main-sequence stars or dwarf stars, and positions of stars on and off the band are believed to indicate their physical properties, as well as their progress through several types of star life-cycles. These are the most numerous true stars in the universe and include the Sun. Color-magnitude plots are known as Hertzsprung–Russell diagrams after Ejnar Hertzsprung and Henry Norris Russell.

<span class="mw-page-title-main">Star</span> Large self-illuminated object in space

A star is an astronomical object comprising a luminous spheroid of plasma held together by self-gravity. The nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night; their immense distances from Earth make them appear as fixed points of light. The most prominent stars have been categorised into constellations and asterisms, and many of the brightest stars have proper names. Astronomers have assembled star catalogues that identify the known stars and provide standardized stellar designations. The observable universe contains an estimated 1022 to 1024 stars. Only about 4,000 of these stars are visible to the naked eye—all within the Milky Way galaxy.

<span class="mw-page-title-main">Stellar evolution</span> Changes to stars over their lifespans

Stellar evolution is the process by which a star changes over the course of time. Depending on the mass of the star, its lifetime can range from a few million years for the most massive to trillions of years for the least massive, which is considerably longer than the current age of the universe. The table shows the lifetimes of stars as a function of their masses. All stars are formed from collapsing clouds of gas and dust, often called nebulae or molecular clouds. Over the course of millions of years, these protostars settle down into a state of equilibrium, becoming what is known as a main-sequence star.

<span class="mw-page-title-main">Stellar nucleosynthesis</span> Creation of chemical elements within stars

Stellar nucleosynthesis is the creation (nucleosynthesis) of chemical elements by nuclear fusion reactions within stars. Stellar nucleosynthesis has occurred since the original creation of hydrogen, helium and lithium during the Big Bang. As a predictive theory, it yields accurate estimates of the observed abundances of the elements. It explains why the observed abundances of elements change over time and why some elements and their isotopes are much more abundant than others. The theory was initially proposed by Fred Hoyle in 1946, who later refined it in 1954. Further advances were made, especially to nucleosynthesis by neutron capture of the elements heavier than iron, by Margaret and Geoffrey Burbidge, William Alfred Fowler and Fred Hoyle in their famous 1957 B2FH paper, which became one of the most heavily cited papers in astrophysics history.

<span class="mw-page-title-main">Red supergiant</span> Stars with a supergiant luminosity class with a spectral type of K or M

Red supergiants (RSGs) are stars with a supergiant luminosity class of spectral type K or M. They are the largest stars in the universe in terms of volume, although they are not the most massive or luminous. Betelgeuse and Antares A are the brightest and best known red supergiants (RSGs), indeed the only first magnitude red supergiant stars.

<span class="mw-page-title-main">Mira variable</span> Type of variable star

Mira variables are a class of pulsating stars characterized by very red colours, pulsation periods longer than 100 days, and amplitudes greater than one magnitude in infrared and 2.5 magnitude at visual wavelengths. They are red giants in the very late stages of stellar evolution, on the asymptotic giant branch (AGB), that will expel their outer envelopes as planetary nebulae and become white dwarfs within a few million years.

<span class="mw-page-title-main">CoRoT</span> European space telescope that operated between 2006 - 2014

CoRoT was a space telescope mission which operated from 2006 to 2013. The mission's two objectives were to search for extrasolar planets with short orbital periods, particularly those of large terrestrial size, and to perform asteroseismology by measuring solar-like oscillations in stars. The mission was led by the French Space Agency (CNES) in conjunction with the European Space Agency (ESA) and other international partners.

<span class="mw-page-title-main">Blue giant</span> Hot, giant star of early spectral type

In astronomy, a blue giant is a hot star with a luminosity class of III (giant) or II. In the standard Hertzsprung–Russell diagram, these stars lie above and to the right of the main sequence.

<span class="mw-page-title-main">Blue supergiant</span> Hot, luminous star with a spectral type of B9 or earlier

A blue supergiant (BSG) is a hot, luminous star, often referred to as an OB supergiant. They have luminosity class I and spectral class B9 or earlier.

<span class="mw-page-title-main">Asteroseismology</span> Study of oscillations in stars

Asteroseismology is the study of oscillations in stars. Stars have many resonant modes and frequencies, and the path of sound waves passing through a star depends on the speed of sound, which in turn depends on local temperature and chemical composition. Because the resulting oscillation modes are sensitive to different parts of the star, they inform astronomers about the internal structure of the star, which is otherwise not directly possible from overall properties like brightness and surface temperature.

Helioseismology, a term coined by Douglas Gough, is the study of the structure and dynamics of the Sun through its oscillations. These are principally caused by sound waves that are continuously driven and damped by convection near the Sun's surface. It is similar to geoseismology, or asteroseismology, which are respectively the studies of the Earth or stars through their oscillations. While the Sun's oscillations were first detected in the early 1960s, it was only in the mid-1970s that it was realized that the oscillations propagated throughout the Sun and could allow scientists to study the Sun's deep interior. The modern field is separated into global helioseismology, which studies the Sun's resonant modes directly, and local helioseismology, which studies the propagation of the component waves near the Sun's surface.

<span class="mw-page-title-main">Giant star</span> Type of star, larger and brighter than the Sun

A giant star, also simply a giant, is a star with substantially larger radius and luminosity than a main-sequence star of the same surface temperature. They lie above the main sequence on the Hertzsprung–Russell diagram and correspond to luminosity classes II and III. The terms giant and dwarf were coined for stars of quite different luminosity despite similar temperature or spectral type by Ejnar Hertzsprung about 1905.

<span class="mw-page-title-main">Asymptotic giant branch</span> Stars powered by fusion of hydrogen and helium in shell with an inactive core of carbon and oxygen

The asymptotic giant branch (AGB) is a region of the Hertzsprung–Russell diagram populated by evolved cool luminous stars. This is a period of stellar evolution undertaken by all low- to intermediate-mass stars (about 0.5 to 8 solar masses) late in their lives.

<span class="mw-page-title-main">Red-giant branch</span> Portion of the giant branch before helium ignition

The red-giant branch (RGB), sometimes called the first giant branch, is the portion of the giant branch before helium ignition occurs in the course of stellar evolution. It is a stage that follows the main sequence for low- to intermediate-mass stars. Red-giant-branch stars have an inert helium core surrounded by a shell of hydrogen fusing via the CNO cycle. They are K- and M-class stars much larger and more luminous than main-sequence stars of the same temperature.

<span class="mw-page-title-main">Subgiant</span> Type of star larger than main-sequence but smaller than a giant

A subgiant is a star that is brighter than a normal main-sequence star of the same spectral class, but not as bright as giant stars. The term subgiant is applied both to a particular spectral luminosity class and to a stage in the evolution of a star.

<span class="mw-page-title-main">Epsilon Ophiuchi</span> Star in the constellation Ophiuchus

Epsilon Ophiuchi or ε Ophiuchi, formally named Yed Posterior, is a red giant star in the constellation of Ophiuchus. Located less than five degrees south of the celestial equator in the eastern part of the constellation, it forms a naked eye optical double with Delta Ophiuchi. With an apparent visual magnitude of 3.220, the star can be seen with the naked eye from most of the Earth under suitably dark skies. Parallax measurements yield an estimated distance of 106.4 light-years from the Sun.

Solar-like oscillations are oscillations in stars that are excited in the same way as those in the Sun, namely by turbulent convection in its outer layers. Stars that show solar-like oscillations are called solar-like oscillators. The oscillations are standing pressure and mixed pressure-gravity modes that are excited over a range in frequency, with the amplitudes roughly following a bell-shaped distribution. Unlike opacity-driven oscillators, all the modes in the frequency range are excited, making the oscillations relatively easy to identify. The surface convection also damps the modes, and each is well-approximated in frequency space by a Lorentzian curve, the width of which corresponds to the lifetime of the mode: the faster it decays, the broader is the Lorentzian. All stars with surface convection zones are expected to show solar-like oscillations, including cool main-sequence stars, subgiants and red giants. Because of the small amplitudes of the oscillations, their study has advanced tremendously thanks to space-based missions.

<span class="mw-page-title-main">Red giant</span> Type of large cool star that has exhausted its core hydrogen

A red giant is a luminous giant star of low or intermediate mass in a late phase of stellar evolution. The outer atmosphere is inflated and tenuous, making the radius large and the surface temperature around 5,000 K or lower. The appearance of the red giant is from yellow-white to reddish-orange, including the spectral types K and M, sometimes G, but also class S stars and most carbon stars.

Yvonne Elsworth FRS FInstP FRAS is an Irish physicist, Professor of Helioseismology and Poynting Professor of Physics in the School of Physics and Astronomy at the University of Birmingham. Elsworth was until 2015 also the Head of the Birmingham Solar Oscillations Network (BiSON), the longest running helioseismology network with data covering well over three solar cycles.

<span class="mw-page-title-main">Gas giant</span> Giant planet mainly composed of light elements

A gas giant is a giant planet composed mainly of hydrogen and helium. Gas giants are also called failed stars because they contain the same basic elements as a star. Jupiter and Saturn are the gas giants of the Solar System. The term "gas giant" was originally synonymous with "giant planet". However, in the 1990s, it became known that Uranus and Neptune are really a distinct class of giant planets, being composed mainly of heavier volatile substances. For this reason, Uranus and Neptune are now often classified in the separate category of ice giants.

References

  1. Chaplin, W.J.; Miglio, A. (August 2013), "Asteroseismology of Solar-Type and Red-Giant Stars", Annual Review of Astronomy and Astrophysics, 51 (1): 353–392, arXiv: 1303.1957 , Bibcode:2013ARA&A..51..353C, doi:10.1146/annurev-astro-082812-140938, S2CID   119222611
  2. Bedding, Timothy R.; et al. (2011). "Gravity modes as a way to distinguish between hydrogen- and helium-burning red giant stars". Nature . 471 (7340): 608–11. arXiv: 1103.5805 . Bibcode:2011Natur.471..608B. doi:10.1038/nature09935. PMID   21455175. S2CID   4338871.
  3. Professor Tim Bedding - Staff Profile at the University of Sydney
  4. History of the University of Sydney School of Physics
  5. Academics recognised for leadership, teaching and research impact
  6. "Guest Speaker - Prof Tim Bedding (University of Sydney) - SASI". www.sasi.net.au.
  7. "National Team Results". afda.com. Australian Flying Disc Association.
  8. "Tim Bedding". Australian Academy of Science. Retrieved 25 May 2020.