Hubble Constant: Measuring the Expansion of the Universe
By J. Leavy (2239104L)
November 16, 2017
The rate of expansion of the universe, first derived as a possibility by Alexander Friedmann through his work with general relativity and his own Friedmann equations [1], was first observationally confirmed and roughly estimated by Edwin Hubble in 1929 [2], and has since appropriately come to be known as the Hubble Constant. Hubble’s work & observational data confirmed that the recessional velocity of a given galaxy was linearly related to the distance between the observed galaxy and the observer, and this relationship could be expressed (as Hubble’s Law):
V=HD
Where V is the recessional velocity, D is the distance, and H is the scaling factor that equates the two, known as the Hubble Constant [3].
Additionally, through unit analysis of these variables, Hubble provided a means for approximating the time the universe has been expanding: D/V=1/H
Since velocity is a distance unit by a time unit, unit analysis yields that the inverse of the Hubble Constant is an estimation for the time the universe has been expanding, and if one assumes the universe expands linearly for its life, an estimate of the age of the universe, known as the Hubble Time [3]:
If H=530s^(-1),D=〖(7.8*〖10〗^6〗_(in parsecs))*(〖30.857*〖10〗^12〗_(conversion to km) ),and V=3779
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With the 1991 launch of the Hubble Space Telescope (HST), astronomers have been given access to data orders of magnitude more accurate and plentiful. In 2001, Wendy Freedman and other researchers, using data obtained via the HST, calculated the value of H to 72 + 8 [6]. Working with data collected from the Chandra X-Ray Observatory in 2006, researcher Massimiliano Bonamente and his team derived a value for H of 77.6 +14.9, -12.5 [7]. Most recently at the LIGO observatory, the value for H was calculated to be 70.0 +12.0, -8.0
How does this relate to the age and origin of the universe? The principle is really quite simple: if the velocity and distance to most galaxies are known, one can extrapolate their motion backward to find the time that they were all compressed together at the moment of the universe's origin, the Big Bang. The duration between then and now is the universe's age. Of course, a simple linear extrapolation won't do; the gravity resulting from matter in the universe can be
It is easy to flip to the index of an astronomy textbook to discover that, say, the Sun lies 150 million kilometers away from Earth. It is far more difficult (if not impossible), however, to picture this distance in our mind. In this exercise, we will learn to access the often unpalatable distances encountered in astronomy by simply scaling the huge distances to more recognizable, familiar numbers. So long as every distance within the system of interest is scaled by the same
The law that Edwin Hubble created has ultimately supported the Big Bang Theory and our knowledge of galaxies. It states that Recessional Velocity is equivalent to Hubble's constant times distance, or V = Ho D. This basically says that the farther a galaxy is
In the early 1900s, Henrietta Leavitt was studying Cepheids in the Large Magellanic Cloud (the small satellite galaxy of the Milky Way) and found a relationship between their period and luminosity. This meant that, simply by measuring the period of a more distant Cepheid, astronomers could immediately determine its luminosity – and hence, its distance.
The late 1920’s most galaxy he observed we are moving away from earth. Each planet are moving farther and farther apart.Even galaxy gets feather apart. Did you know that it takes the light from the sun to the earth it takes 7 minutes to travel from there to here.
Which means that they at one point must have been touching each other. To help verify this was Edward Hubble who found there is a directly proportional “relation between Redshift and Distance”(pg.22). Meaning galaxy’s light spectrum increases in wavelength from the light we receive from a galaxy and the speed with which it moves away from earth. He used that to calculate the distance of the galaxy from Earth, and then approximated the age for the universe. “There is... a way to confirm that the galaxies are really moving apart, as indicated by the red shifts”(page32). This discovery was a great importance to the Standard Model. Once it was clear that the universe was expanding, Hubble proceeded to calculate the speed the galaxies that are moving away from us. A constant now called “Hubble’s constant”, which determines that galaxies increase in constant proportion to their distance. The next thing important to the Standard Model was the Theory of General Relativity published by Albert Einstein. His model predicted an expanding universe; “in order to achieve a model that fit…Einstein was forced to mutilate his equation by introducing a term called cosmological constant”(page 35). Which made the formula consistent with a static Universe. The next important thing about the Standard Model was when the radiation expanded, dropped frequency and gained wavelength. There was “diffuse background of radio static left over from near the beginning of the universe”(page46). “Arno A. Penzias and Robert W. Wilson, set out to use the antenna to measure the intensity of the radio waves emitted from our galaxy at high galactic latitudes, out of the planes of the Milky Way”(page46). Which confirmed the Standard Model theory that remained
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Edwin hubble invented the space telescope, he made some of the most important discoveries in modern astronomy. As an astronomer, Dr. Hubble was a late bloomer. Before discovering his passion for the stars, Dr. Hubble earned a law degree and served in World War I. 1373 Cincinnati, provisional designation 1935 QN, is an asteroid of the outer asteroid belt, approximately 20 kilometers in diameter. It was discovered by the famous American astronomer Edwin Hubble at Mount Wilson Observatory on August 30, 1935. In his short paper, Hubble presented the observational evidence for one of science’s greatest discoveries the expanding universe. Hubble showed that galaxies are receding away from us with a velocity that is proportional to their distance
Mega parsec (Mpc) is a unit that consists of 1 million parsec, where 1 parsec is equal to 3.26 light years. Distance indicators are used to measure distances of objects brighter than Cepheid stars. Hubble’s Law is the relationship between the distances of galaxies; the further away the galaxy is the faster its moving. Spiral Galaxy is where there is a central hub surrounded by a disk of stars, gas and dust in a spiral pattern. Elliptical Galaxy is a round ball shape galaxy which consisting of almost a trillion stars in them. Irregular Galaxies are small galaxies that have no fixed shape. Barred Spiral Galaxy is a galaxy that has a nucleus which has a shape of a bar from which the spirals arms extend. Star Burst Galaxy is galaxies that are undergoing
Calculating stellar movements 5 millions years in the future is no simple math problem. Objects that are great distances appear to move much slower the those closer. We are only just beginning to learn about the behavior of the stars and we cannot know if the will behave the way we expect.
we can see that the modulus of this quantity increases as the Hubble radius increases too. Thus if we have \left|\Omega_{k,0}\right|\leq0.01
Edwin Hubble’s curiosity about the universe started at youth and has grown. Without this, he would have no desire to study the stars or galaxies. Hubble’s interest in astronomy at the age of eight. On his eighth birthday party he spent the night with his grandfather star gazing (Freidman 16). When he was twelve years old he would ask his parents to seep outside and look at the stars at midnight with his friend Sam Shelton (18). His grandfather asked Hubble an astronomical question, and Hubble answered it so cleverly that his
The idea that the universe is expanding was introduced to me as a given, an understood idea that I would come to understand in later years, not unlike many other principles of science as a fact so fundamental it was discovered or derived centuries ago. However, Hubble’s Law, a concept so central to our basic understanding of the universe, made its debut just under a century ago alongside our adoption of what we consider incredibly modern events such as the Industrial Revolution, the advent of motion pictures, our widespread adoption of automobiles and telephones, and Einstein himself developing the theory of general relativity. This makes us contemplate just how exponential our learning curve as a species has been, when we consider that it
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The Hubble’s constant is a measure of the current expansion rate of the universe (1). Researchers have deduced that the expansion rate of the universe is found by the current density and composition it holds (1). Hubble’s constant is represented by H0; the equation use is 1/H0 (1). According to Hubble’s constant, it is around 72 km/sec/Mega parsec (1). Thus, approximately equals to about 13.77 billion years; give or take about 50 million years (1). However, researchers discovered that the universe is currently expanding slower than previous years; affecting the rate of the universe (1).