Methuselah Star
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HD 140283 (also known as the Methuselah star) is a metal-poor subgiant star about 190 
light year A light-year, alternatively spelled light year, is a large unit of length used to express astronomical distances and is equivalent to about 9.46 trillion kilometers (), or 5.88 trillion miles ().One trillion here is taken to be 1012 ...
s away from the Earth in the constellation Libra, near the boundary with Ophiuchus in the Milky Way Galaxy. Its apparent magnitude is 7.205. It is one of the oldest stars known. The star's light is somewhat blueshifted as it is moving toward rather than away from the Earth and it has been known to astronomers for over a century as a high-velocity star based on its other vectors (proper motion). An early spectroscopic analysis by Joseph W. Chamberlain and
Lawrence Aller Lawrence Hugh Aller (September 24, 1913 – March 16, 2003) was an American astronomer. He was born in Tacoma, Washington. He never finished high school and worked for a time as a gold miner. He received his bachelor's degree from the University ...
revealed it to have a substantially lower metal content than the Sun. Modern spectroscopic analyses find an iron content about a factor of 250 lower than that of the Sun. It is one of the closest metal-poor ( Population II) stars to Earth. The star was already known by
1912 Events January * January 1 – The Republic of China (1912–49), Republic of China is established. * January 5 – The Prague Conference (6th All-Russian Conference of the Russian Social Democratic Labour Party) opens. * January 6 ...
when W. S. Adams measured its
astrometry Astrometry is a branch of astronomy that involves precise measurements of the positions and movements of stars and other celestial bodies. It provides the kinematics and physical origin of the Solar System and this galaxy, the Milky Way. His ...
using a
spectrograph An optical spectrometer (spectrophotometer, spectrograph or spectroscope) is an instrument used to measure properties of light over a specific portion of the electromagnetic spectrum, typically used in spectroscopic analysis to identify mate ...
in the Mount Wilson Observatory.


Age and significance

Because HD 140283 is neither on the
main sequence In astronomy, the main sequence is a continuous and distinctive band of stars that appears on plots of stellar color versus brightness. These color-magnitude plots are known as Hertzsprung–Russell diagrams after their co-developers, Ejnar Her ...
nor a
red giant A red giant is a luminous giant star of low or intermediate mass (roughly 0.3–8 solar masses ()) in a late phase of stellar evolution. The outer atmosphere is inflated and tenuous, making the radius large and the surface temperature around or ...
, its early position in the
Hertzsprung–Russell diagram The Hertzsprung–Russell diagram, abbreviated as H–R diagram, HR diagram or HRD, is a scatter plot of stars showing the relationship between the stars' absolute magnitudes or luminosity, luminosities versus their stellar classifications or eff ...
has been interpreted with its data and theoretical models of
stellar evolution 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 cons ...
based on quantum mechanics and the observations of processes in millions of stars to infer its apparent old age. For field stars (as opposed to stars in clusters), it is rare to know a star's luminosity, surface temperature, and composition precisely enough to get a well-constrained value for its age. Because of their relative scarcity, this is even rarer for a Population II star such as HD 140283. A study published in 2013 used the Fine Guidance Sensors of NASA's Hubble Space Telescope to measure a precise parallax (and therefore distance and
luminosity Luminosity is an absolute measure of radiated electromagnetic power (light), the radiant power emitted by a light-emitting object over time. In astronomy, luminosity is the total amount of electromagnetic energy emitted per unit of time by a st ...
) for the star. This information was used to estimate an age for the star of 14.46 ± 0.8 billion years. Due to the uncertainty in the value, this age for the star would possibly conflict with the calculated age of the Universe as determined by the final 2018
Planck satellite ''Planck'' was a space observatory operated by the European Space Agency (ESA) from 2009 to 2013, which mapped the anisotropies of the cosmic microwave background (CMB) at microwave and infrared frequencies, with high sensitivity and small angu ...
results of 13.761±0.038 billion years. However, more recent models of its stellar evolution have suggested revision of the star's age to 13.7 billion years or 12 billion years. Once dubbed the " Methuselah Star" by the popular press due to its age, if the assumptions of stellar evolution are correct in the report, the star must have formed soon after the Big Bang and is one of the
oldest star The age of the oldest known stars approaches the age of the universe, about 13.8 billion years. Some of these are among the first stars from reionization (the stellar dawn), ending the Dark Ages about 370,000 years after Big Bang. Thes ...
s known as of 2021. The search for such very iron-poor stars has shown they are almost all anomalies in globular clusters and the Galactic Halo. This accords with a narrative that they are rare survivors of their generation. If so, the apparent visual data of the oldest of these enables us to longstop-date the reionization (first star formation) phase of the Universe independently of theories and evidence of the first few million years after the
Big Bang The Big Bang event is a physical theory that describes how the universe expanded from an initial state of high density and temperature. Various cosmological models of the Big Bang explain the evolution of the observable universe from the ...
. Most stars from Population II and Population III are no longer observable. Theories exist allowing for an older age of the universe than conventionally accepted, which can still accommodate the observed redshift of early objects and earlier radiation. Some depart from the conventional big-bang/ inflation model, such as the
steady-state In systems theory, a system or a process is in a steady state if the variables (called state variables) which define the behavior of the system or the process are unchanging in time. In continuous time, this means that for those properties ''p'' ...
and cyclic models. To date no accurate, greater-age evidence from a cosmic object has been found that calls into question the
Planck satellite ''Planck'' was a space observatory operated by the European Space Agency (ESA) from 2009 to 2013, which mapped the anisotropies of the cosmic microwave background (CMB) at microwave and infrared frequencies, with high sensitivity and small angu ...
results. Studies of the star also help astronomers understand the Universe's early history. Very low but non-zero metallicities of stars like HD 140283 indicate the star was formed from existing materials in the second generation of stellar creation; their heavy-element content is believed to have come from zero-metal stars ( Population III stars), which have never been observed. Those first stars are thought to have been formed from existing materials a few hundred million years after the Big Bang, and they died in explosions (
supernova A supernova is a powerful and luminous explosion of a star. It has the plural form supernovae or supernovas, and is abbreviated SN or SNe. This transient astronomical event occurs during the last evolutionary stages of a massive star or when ...
e) after only a few million years. A second generation of stars, the generation in which HD 140283 is theorized to have been formed from existing materials, could not have coalesced until gas, heated from the supernova explosions of the earlier stars, cooled down. This
hypothesis A hypothesis (plural hypotheses) is a proposed explanation for a phenomenon. For a hypothesis to be a scientific hypothesis, the scientific method requires that one can testable, test it. Scientists generally base scientific hypotheses on prev ...
of such stars' birth and our best models of the early universe indicate that the time it took for the gases to cool was likely only a few tens of millions of years. The proportions of elements in such metal-poor stars is modelled to tell us much of the earlier
nucleosynthetic Nucleosynthesis is the process that creates new atomic nuclei from pre-existing nucleons (protons and neutrons) and nuclei. According to current theories, the first nuclei were formed a few minutes after the Big Bang, through nuclear reactions in ...
("metals") yield, that is of elements other than hydrogen and helium from the supernovae of the locally-extinct Population III stars. Some of the latter may be visible in
gravitational lensing A gravitational lens is a distribution of matter (such as a cluster of galaxies) between a distant light source and an observer that is capable of bending the light from the source as the light travels toward the observer. This effect is known ...
in looking at deepest images such as the
Hubble Ultra-Deep Field The Hubble Ultra-Deep Field (HUDF) is a deep-field image of a small region of space in the constellation Fornax, containing an estimated 10,000 galaxies. The original data for the image was collected by the Hubble Space Telescope from Septemb ...
(i.e., their brief existence before their turning into supernovae). As with , CS22892-0052, and , HD 140283 has an excess of
oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as we ...
and the
alpha elements Alpha (uppercase , lowercase ; grc, ἄλφα, ''álpha'', or ell, άλφα, álfa) is the first letter of the Greek alphabet. In the system of Greek numerals, it has a value of one. Alpha is derived from the Phoenician letter aleph , whic ...
relative to iron. While the proportions of these elements is much lower in HD 140283 than in the Sun, they are not as low as is the case for iron. The implication is that the first population of stars generated the alpha elements preferentially to other groups of elements, including the
iron peak The iron peak is a local maximum in the vicinity of Fe ( Cr, Mn, Fe, Co and Ni) on the graph of the abundances of the chemical elements. For elements lighter than iron on the periodic table, nuclear fusion releases energy. For iron, and for ...
and
s-process The slow neutron-capture process, or ''s''-process, is a series of reactions in nuclear astrophysics that occur in stars, particularly asymptotic giant branch stars. The ''s''-process is responsible for the creation ( nucleosynthesis) of approxim ...
. Unlike those other metal-poor stars, HD 140283 has a detectable amount of
lithium Lithium (from el, λίθος, lithos, lit=stone) is a chemical element with the symbol Li and atomic number 3. It is a soft, silvery-white alkali metal. Under standard conditions, it is the least dense metal and the least dense solid ...
, a consequence of HD 140283 having not yet evolved into a
red giant A red giant is a luminous giant star of low or intermediate mass (roughly 0.3–8 solar masses ()) in a late phase of stellar evolution. The outer atmosphere is inflated and tenuous, making the radius large and the surface temperature around or ...
and thereby not yet having undergone the first
dredge-up A dredge-up is any one of several stages in the evolution of some stars. By definition, during a ''dredge-up'', a convection zone extends all the way from the star's surface down to the layers of material that have undergone fusion. Consequently, ...
.


See also

*
Libra in Chinese astronomy According to traditional Chinese uranography, the modern constellation Libra is located within the eastern quadrant of the sky, which is symbolized as the Azure Dragon of the East (東方青龍, ''Dōng Fāng Qīng Lóng''). The name of the weste ...
*
HE 1523-0901 HE 1523-0901 is the designation given to a red giant star in the Milky Way galaxy approximately 7500 light years from Earth. It is thought to be a second generation, Population II, or metal-poor, star ( e/Hnbsp;= −2.95). The star w ...


References

{{DEFAULTSORT:HD 140283 Durchmusterung objects
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140283 076976 Libra (constellation) G-type subgiants High-proper-motion stars Population II stars