Vesto Melvin Slipher (/ˈslaɪfər/; November 11, 1875 – November 8, 1969) was an American astronomer who performed the first measurements of radial velocities for galaxies, providing the first empirical basis for the expansion of the universe. 
Vesto Melvin Slipher
|Born||November 11, 1875|
|Died||November 8, 1969 (aged 93)|
|Resting place||Citizens Cemetery, Flagstaff|
|Known for||Expanding universe|
|Relatives||Earl C. Slipher (brother)|
Slipher was born in Mulberry, Indiana, and completed his doctorate at Indiana University in 1909. He spent his entire career at Lowell Observatory in Flagstaff, Arizona, where he was promoted to assistant director in 1915, acting director in 1916, and finally director from 1926 until his retirement in 1952.
His brother Earl C. Slipher was also an astronomer and a director at the Lowell Observatory.
Slipher used spectroscopy to investigate the rotation periods of planets and the composition of planetary atmospheres. In 1912, he was the first to observe the shift of spectral lines of galaxies, making him the discoverer of galactic redshifts. In 1914, Slipher also made the first discovery of the rotation of spiral galaxies. He discovered the sodium layer in 1929. He was responsible for hiring Clyde Tombaugh and supervised the work that led to the discovery of Pluto in 1930.
Edwin Hubble is often incorrectly credited with discovering the redshift of galaxies; these measurements and their significance were understood before 1917 by James Edward Keeler (Lick & Allegheny), Vesto Melvin Slipher (Lowell), and William Wallace Campbell (Lick) at other observatories.
Combining his own measurements of galaxy distances with Vesto Slipher's measurements of the redshifts associated with the galaxies, Hubble and Milton Humason discovered a rough proportionality of the objects' distances with their redshifts. This redshift-distance correlation, nowadays termed Hubble's law, was formulated by Hubble and Humason in 1929 and became the basis for the modern model of the expanding universe.
1766 Slipher, provisional designation 1962 RF, is a Paduan asteroid from the central regions of the asteroid belt, approximately 18 kilometers in diameter. It was discovered on 7 September 1962, by astronomers of the Indiana Asteroid Program at Goethe Link Observatory in Indiana, United States. The asteroid was named after American astronomers Vesto Slipher and his brother Earl C. Slipher.Beta Cephei variable
Beta Cephei variables, also known as Beta Canis Majoris stars, are variable stars that exhibit small rapid variations in their brightness due to pulsations of the stars' surfaces, thought due to the unusual properties of iron at temperatures of 200,000 K in their interiors. These stars are usually hot blue-white stars of spectral class B and should not be confused with Cepheid variables, which are named after Delta Cephei and are luminous supergiant stars.Carl Wilhelm Wirtz
Carl Wilhelm Wirtz (24 August 1876 in Krefeld – 18 February 1939 in Hamburg) was an astronomer who spent his time between the Kiel Observatory (526) in Germany and the Observatory of Strasbourg, France. He is known for statistically showing the existence of a redshift-distance correlation for spiral galaxies.Earl C. Slipher
Earl Charles Slipher (; March 25, 1883 – August 7, 1964) was an American astronomer. He was the brother of astronomer Vesto Slipher.Edwin Hubble
Edwin Powell Hubble (November 20, 1889 – September 28, 1953) was an American astronomer. He played a crucial role in establishing the fields of extragalactic astronomy and observational cosmology and is regarded as one of the most important astronomers of all time.Hubble discovered that many objects previously thought to be clouds of dust and gas and classified as "nebulae" were actually galaxies beyond the Milky Way. He used the strong direct relationship between a classical Cepheid variable's luminosity and pulsation period (discovered in 1908 by Henrietta Swan Leavitt) for scaling galactic and extragalactic distances.Hubble provided evidence that the recessional velocity of a galaxy increases with its distance from the Earth, a property now known as "Hubble's law", despite the fact that it had been both proposed and demonstrated observationally two years earlier by Georges Lemaître. Hubble-Lemaître's Law implies that the universe is expanding. A decade before, the American astronomer Vesto Slipher had provided the first evidence that the light from many of these nebulae was strongly red-shifted, indicative of high recession velocities.Hubble's name is most widely recognized for the Hubble Space Telescope which was named in his honor, with a model prominently displayed in his hometown of Marshfield, Missouri.Henrietta Swan Leavitt
Henrietta Swan Leavitt (; July 4, 1868 – December 12, 1921) was an American astronomer. A graduate of Radcliffe College, she worked at the Harvard College Observatory as a "computer", tasked with examining photographic plates in order to measure and catalog the brightness of stars. This work led her to discover the relation between the luminosity and the period of Cepheid variables. Though she received little recognition in her lifetime, Leavitt's discovery provided astronomers with the first "standard candle" with which to measure the distance to faraway galaxies. After her death, Edwin Hubble used Leavitt's luminosity–period relation, together with the galactic spectral shifts first measured by Vesto Slipher at Lowell Observatory, in order to establish that the universe is expanding (see Hubble's law).History of the Big Bang theory
The history of the Big Bang theory began with the Big Bang's development from observations and theoretical considerations. Much of the theoretical work in cosmology now involves extensions and refinements to the basic Big Bang model.Hubble's law
Hubble's law, also known as the Hubble–Lemaître law, is the observation in physical cosmology that:
Hubble's law is considered the first observational basis for the expansion of the universe and today serves as one of the pieces of evidence most often cited in support of the Big Bang model. The motion of astronomical objects due solely to this expansion is known as the Hubble flow.
Although widely attributed to Edwin Hubble, the law was first derived from the general relativity equations in 1922 by Alexander Friedmann. Friedmann published a set of equations, now known as the Friedmann equations, showing that the universe might expand, and presenting the expansion speed if this was the case. Then Georges Lemaître, in a 1927 article, proposed the expansion of the universe and suggested an estimated value of the rate of expansion, which when corrected by Hubble became known as the Hubble constant. Though the Hubble constant is roughly constant in the velocity-distance space at any given moment in time, the Hubble parameter , which the Hubble constant is the current value of, varies with time, so the term 'constant' is sometimes thought of as somewhat of a misnomer. Moreover, two years later Edwin Hubble confirmed the existence of cosmic expansion, and determined a more accurate value for the constant that now bears his name. Hubble inferred the recession velocity of the objects from their redshifts, many of which were earlier measured and related to velocity by Vesto Slipher in 1917. In October 2018, scientists presented a new third way (two earlier methods gave problematic results that do not agree), using information from gravitational wave events (especially those involving the merger of neutron stars, like GW170817), of determining the Hubble Constant, essential in establishing the exact rate of expansion of the universe.
The law is often expressed by the equation v = H0D, with H0 the constant of proportionality—Hubble constant—between the "proper distance" D to a galaxy, which can change over time, unlike the comoving distance, and its velocity v, i.e. the derivative of proper distance with respect to cosmological time coordinate. (See uses of the proper distance for some discussion of the subtleties of this definition of 'velocity'.) Also, the SI unit of H0 is s−1, but it is most frequently quoted in (km/s)/Mpc, thus giving the speed in km/s of a galaxy 1 megaparsec (3.09×1019 km) away. The reciprocal of H0 is the Hubble time.Lalande Prize
The Lalande Prize (French: Prix Lalande) was an award for scientific advances in astronomy, given from 1802 until 1970 by the French Academy of Sciences.
The prize was endowed by astronomer Jérôme Lalande in 1801, a few years before his death in 1807, to enable the Academy of Sciences to make an annual award "to the person who makes the most unusual observation or writes the most useful paper to further the progress of Astronomy, in France or elsewhere."
It was combined with the Valz Prize (Prix Valz) in 1970 to create the Lalande-Valz Prize and then with a further 122 foundation prizes in 1997, resulting in the establishment of the Grande Médaille. The Grande Medaille is not limited to the field of astronomy.List of people from Flagstaff, Arizona
This is a listing of notable people who were born in, or have lived in, Flagstaff, Arizona.Nebula
A nebula (Latin for "cloud" or "fog"; pl. nebulae, nebulæ, or nebulas) is an interstellar cloud of dust, hydrogen, helium and other ionized gases. Originally, the term was used to describe any diffuse astronomical object, including galaxies beyond the Milky Way. The Andromeda Galaxy, for instance, was once referred to as the Andromeda Nebula (and spiral galaxies in general as "spiral nebulae") before the true nature of galaxies was confirmed in the early 20th century by Vesto Slipher, Edwin Hubble and others.
Most nebulae are of vast size; some are hundreds of light years in diameter. A nebula that is barely visible to the human eye from Earth would appear larger, but no brighter, from close by. The Orion Nebula, the brightest nebula in the sky and occupying an area twice the diameter of the full Moon, can be viewed with the naked eye but was missed by early astronomers. Although denser than the space surrounding them, most nebulae are far less dense than any vacuum created on Earth – a nebular cloud the size of the Earth would have a total mass of only a few kilograms. Many nebulae are visible due to fluorescence caused by embedded hot stars, while others are so diffuse they can only be detected with long exposures and special filters. Some nebulae are variably illuminated by T Tauri variable stars.
Nebulae are often star-forming regions, such as in the "Pillars of Creation" in the Eagle Nebula. In these regions the formations of gas, dust, and other materials "clump" together to form denser regions, which attract further matter, and eventually will become dense enough to form stars. The remaining material is then believed to form planets and other planetary system objects.Physical cosmology
Physical cosmology is a branch of cosmology concerned with the studies of the largest-scale structures and dynamics of the Universe and with fundamental questions about its origin, structure, evolution, and ultimate fate. Cosmology as a science originated with the Copernican principle, which implies that celestial bodies obey identical physical laws to those on Earth, and Newtonian mechanics, which first allowed us to understand those physical laws. Physical cosmology, as it is now understood, began with the development in 1915 of Albert Einstein's general theory of relativity, followed by major observational discoveries in the 1920s: first, Edwin Hubble discovered that the universe contains a huge number of external galaxies beyond our own Milky Way; then, work by Vesto Slipher and others showed that the universe is expanding. These advances made it possible to speculate about the origin of the universe, and allowed the establishment of the Big Bang Theory, by Georges Lemaître, as the leading cosmological model. A few researchers still advocate a handful of alternative cosmologies; however, most cosmologists agree that the Big Bang theory explains the observations better.
Dramatic advances in observational cosmology since the 1990s, including the cosmic microwave background, distant supernovae and galaxy redshift surveys, have led to the development of a standard model of cosmology. This model requires the universe to contain large amounts of dark matter and dark energy whose nature is currently not well understood, but the model gives detailed predictions that are in excellent agreement with many diverse observations.Cosmology draws heavily on the work of many disparate areas of research in theoretical and applied physics. Areas relevant to cosmology include particle physics experiments and theory, theoretical and observational astrophysics, general relativity, quantum mechanics, and plasma physics.Redshift
In physics, redshift is a phenomenon where electromagnetic radiation (such as light) from an object undergoes an increase in wavelength. Whether or not the radiation is visible, "redshift" means an increase in wavelength, equivalent to a decrease in wave frequency and photon energy, in accordance with, respectively, the wave and quantum theories of light.
Neither the emitted nor perceived light is necessarily red; instead, the term refers to the human perception of longer wavelengths as red, which is at the section of the visible spectrum with the longest wavelengths. Examples of redshifting are a gamma ray perceived as an X-ray, or initially visible light perceived as radio waves. The opposite of a redshift is a blueshift, where wavelengths shorten and energy increases. However, redshift is a more common term and sometimes blueshift is referred to as negative redshift.
There are three main causes of red (and blue shifts) in astronomy and cosmology:
Objects move apart (or closer together) in space. This is an example of the Doppler effect.
Space itself expands, causing objects to become separated without changing their positions in space. This is known as cosmological redshift. All sufficiently distant light sources (generally more than a few million light years away) show redshift corresponding to the rate of increase in their distance from Earth, known as Hubble's Law.
Gravitational redshift is a relativistic effect observed due to strong gravitational fields, which distort spacetime and exert a force on light and other particles.Knowledge of redshifts and blueshifts has been used to develop several terrestrial technologies such as Doppler radar and radar guns. Redshifts are also seen in the spectroscopic observations of astronomical objects. Its value is represented by the letter z.
A special relativistic redshift formula (and its classical approximation) can be used to calculate the redshift of a nearby object when spacetime is flat. However, in many contexts, such as black holes and Big Bang cosmology, redshifts must be calculated using general relativity. Special relativistic, gravitational, and cosmological redshifts can be understood under the umbrella of frame transformation laws. There exist other physical processes that can lead to a shift in the frequency of electromagnetic radiation, including scattering and optical effects; however, the resulting changes are distinguishable from true redshift and are not generally referred to as such (see section on physical optics and radiative transfer).Reflection nebula
In astronomy, reflection nebulae are clouds of interstellar dust which might reflect the light of a nearby star or stars. The energy from the nearby stars is insufficient to ionize the gas of the nebula to create an emission nebula, but is enough to give sufficient scattering to make the dust visible. Thus, the frequency spectrum shown by reflection nebulae is similar to that of the illuminating stars. Among the microscopic particles responsible for the scattering are carbon compounds (e. g. diamond dust) and compounds of other elements such as iron and nickel. The latter two are often aligned with the galactic magnetic field and cause the scattered light to be slightly polarized.Slipher (lunar crater)
Slipher is a lunar impact crater, that is located in the northern latitudes on the far side of the Moon. The crater overlies the southwestern outer rim of the much larger walled plain D'Alembert, and it occupies a portion of the interior floor of D'Alembert. To the south-southeast is the crater Langevin.
Because it overlies D'Alembert, Slipher is a younger formation and it has undergone much less erosion. The rim is circular but has a somewhat irregular edge. The rim is jumbled and irregular where it intersects D'Alembert. Overlapping the western rim and inner walls of Slipher is the smaller Slipher S, a fresh feature with a sharp-edged outer rim. The interior floor of Slipher is somewhat uneven except in the northeast, and there is a cluster of low central ridges near the midpoint.Sodium layer
The sodium layer is a layer of neutral atoms of sodium within Earth's mesosphere. This layer usually lies within an altitude range of 80–105 km (50–65 mi) above sea level and has a depth of about 5 km (3.1 mi). The sodium comes from the ablation of meteors. Atmospheric sodium below this layer is normally chemically bound in compounds such as sodium oxide, while the sodium atoms above the layer tend to be ionized.
The density varies with season; the average column density (the number of atoms per unit area above any point on the earth's surface) is roughly 4 billion sodium atoms/cm2. For a typical thickness of 5 km this corresponds to volume density of roughly 8000 sodium atoms/cm3. Atoms of sodium in this layer can become excited due to sunlight, solar wind, or other causes. Once excited, these atoms radiate very efficiently around 589 nm, which is in the yellow portion of the spectrum. These radiation bands are known as the sodium D lines. The resulting radiation is one of the sources of air glow.
Astronomers have found the sodium layer to be useful for creating an artificial laser guide star in the upper atmosphere. The star is used by adaptive optics to compensate for movements in the atmosphere. As a result, optical telescopes can perform much closer to their theoretical limit of resolution.
The sodium layer was first discovered in 1929 by American astronomer Vesto Slipher. In 1939 the British-American geophysicist Sydney Chapman proposed a reaction-cycle theory to explain the night-glow phenomenon.Static universe
A static universe, also referred to as a "stationary" or "infinite" or "static infinite" universe, is a cosmological model in which the universe is both spatially infinite and temporally infinite, and space is neither expanding nor contracting. Such a universe does not have so-called spatial curvature; that is to say that it is 'flat' or Euclidean. A static infinite universe was first proposed by Thomas Digges (1546 .. 1595) .In contrast to this model, Albert Einstein proposed a temporally infinite but spatially finite model as his preferred cosmology during 1917, in his paper Cosmological Considerations in the General Theory of Relativity.
After the discovery of the redshift–distance relationship (deduced by the inverse correlation of galactic brightness to redshift) by Vesto Slipher and Edwin Hubble, the astrophysicist and Roman Catholic priest Georges Lemaître interpreted the redshift as proof of universal expansion and thus a Big Bang, whereas Fritz Zwicky proposed that the redshift was caused by the photons losing energy as they passed through the matter and/or forces in intergalactic space. Zwicky's proposal would come to be termed 'tired light'- a term invented by the major Big Bang proponent Richard Tolman.Timeline of cosmological theories
This timeline of cosmological theories and discoveries is a chronological record of the development of humanity's understanding of the cosmos over the last two-plus millennia. Modern cosmological ideas follow the development of the scientific discipline of physical cosmology.