Hubble constant, isHubble's lawThe constant value in.Hubble's law is about physicsCosmologyThis law was first formulated in 1929 after nearly ten years of observation by Hubble and Milton Schumerson. It is considered to be the first observation basis on the extended space paradigm and is often cited as supportbig bangAn important evidence of.With the proposition of Hubble's law,Cosmic expansionThe concept of.
In September 2019, German scientists usedGravitational lensing effectThe Hubble constant is calculated to be 82.4, so the age of the universe is calculated to be 11.4 billion years, more than 2 billion years younger than the 13.7 billion years of mainstream opinion.[1]In 2022, an analysis by American astrophysicists,The expansion rate of the current universe is determined, that is, the Hubble constant is 73.4 (km/s)/Mpc gap, and the uncertainty is only 1.3%.[2]
Chinese name
Hubble constant
Foreign name
Hubble constant
Alias
Hubble's law
Constant value
67.80 ± 0.77 (km/s)/Mpc (determined by European Space Agency)
Hubble's lawZhonghe alien systemRetrogression speedThe ratio of the same distance.It is a constant, usually expressed in H, and its unit is km/(second · millionth second difference).This ratio is sometimes referred to as the velocity distance ratio, or Hubble ratio.
Hubble's law
European Space AgencyAnnounced on March 21, 2013, pursuant toPlanck satelliteThe new Hubble constant value is 67.80 ± 0.77 (km/s)/Mpc (MpcMillisecond gap, about 3 million light years), that is, the speed of the galaxy away from the Earth increases by 67.80 ± 0.77 kilometers per second for every additional 3 million light years (or every 3 million years).
Discovery history
Announce
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In 1929, Hubble first discovered theApparent velocityIt is proportional to the distance (that is, the greater the distance, the greater the apparent velocity), and gives the speed distance ratio, with the symbol K and the ratio 500.Later people called it the Hubble constant and used the symbol H.In 1931, Hubble and s. Hammarson determined that H was 558 for the second time, and later revised it to 526.
When measuring H by HubbleCepheid variableAnd the brightest star in the galaxy.In 1952, Bud pointed out that,Andromeda galaxyThe magnitude zero point of Cepheid variable in should change by 1.5 degrees, so the Hubble constant should be revised to H=260.1958SandwichIt is pointed out that the brightest star mentioned by Hubble is actually located atIonized hydrogen regionTherefore, a magnitude correction of 1.8 is added to reduce the Hubble constant to H=75.From 1974 to 1976, Sandage and Taman revised the Hubble constant again by using seven distance indicators, and obtained H=55, which was only 1/10 of the measured value of Hubble in that year.That is to say, pressHubble's lawTo calculate the distance between galaxies, the new revised value of H is 10 times larger than that of Hubble.
stayRelativistic cosmologyHubble constant can be compared withCosmic scale factorR (t) is linked: H=(t)/R (t).In some cosmology, the Hubble constant is a function of time. Usually, H represents the modern value of the Hubble constant, and H is called Hubbleparameter。
Since the 1970s, many astronomers have measured H by various methods, and the values obtained by various researchers are very inconsistent.
The difference between the measured values of Hubble constant lies in the difference betweenDistance modulusDifferent.Except observedsystematic error、random errorandGalaxyBesides external factors such as the calibration uncertainty of the internal distance index, there are internal reasons.For example, due to the differences in chemical composition, age, and evolutionary experience between different galaxies, the distance index andAbsolute magnitudeThe relationship between them will not be consistent.
On May 7, 2009,NASAAccording to NASA's data on distant galaxiesIa supernovaThe latest measurement results of, the published Hubble constant is (74.2 ± 3.6) (km/s)/MpcUncertaintyIt is further reduced to less than 5%.
In September 2019, German scientists wrote an article in Science magazine that the Hubble constant was calculated to be 82.4 by using the gravitational lens effect, thus the age of the universe was calculated to be 11.4 billion years old, more than 2 billion years younger than the 13.7 billion years according to the mainstream view.[1]
In 2022, an analysis by American astrophysicists,The expansion rate of the current universe is determined, that is, the Hubble constant is 73.4 (km/s)/Mpc gap, and the uncertainty is only 1.3%.[2]
