2. (7) The present age of the Universe is t 0 = t(z= 0) ˇ13:8 Gyr. Since almost all the age of the universe is at low redshift (z = 0 – 2), the galaxies may have formed nearly at the same epoch, regardless of their constraints on the redshift space. Assuming the Universe is 13.5 billion years old at present, how old is the Universe at redshifts, z, of z = 0.5 ... etc, z= 100? This is an incredible accomplishment. In this animation, the galaxy on the left was formed a long time ago, while the galaxy on the right was formed more recently. The galaxy is seen as it was 6.1 billion years ago. So, redshift also gives astronomers a way to understand how far away things are in addition to how fast they are moving. An alternative route to this result would have been to use the general differential expression for comoving distance dr / dz; since c dt = [R 0 / (1 + z)] dr, this gives the age of the universe as an integral over z. For instance, objects with the current redshift z from 5 to 10 will remain observable for no more than 4–6 billion years. What the Hubble constant really depends on is how old was the universe at the time, but if you have a dynamical model of the universe, you can map that into z and come up with a function H(z). The universe was much smaller when the light left the z=2 object than when it left the z=1 object. As the universe's expansion is accelerating, all currently observable objects will eventually appear to freeze in time, while emitting progressively redder and fainter light. 2013 April 8 A Redshift Lookup Table for our Universe Image Credit: Sergey V. Pilipenko (LPI, MIPT) Explanation: How far away is If there is one question in science it should be: \How old is the Universe?" When we insert the redshift dependences of H (z) and (z), (3.45) this gives us the time-redshift relation. A matter-dominated Universe grows with time as [tex]a \propto t^{\frac{2}{3}} [/tex]. Cosmological Redshift: the wavelength of the emitted radiation is lengthened due to the expansion of the Universe. a= (1 + z) 1 and da= (1 + z) 2dzgives the age of the Universe as a function of redshift z: t(z) = 1 H 0 Z 1 z dz0 (1 + z0) p (z0) (\Age of the Universe"). THE AGE–REDSHIFT TEST The theoretical age of an object at redshift z is given as =ò ¢ +¢ ¢ ¥ p p tz dz zHz (, ) (1 ) ( , ),(1) z th where p stands for all the parameters of the cosmological model under consideration and H(, )z p is the Hubble parameter at redshift z. The reason is, in the second case the universe was only 3.37 billion years old whereas the z=1 quasar is seen in a much older universe, one just under 6 billion years old. Astronomers assign the letter z to redshift. Hubble galaxy at redshift z = 0.65 This image, taken by the NASA/ESA Hubble Space Telescope, shows a galaxy similar in mass to the Milky Way. Cosmological Calculator for the Flat Universe by Nick Gnedin Input either one: Length units: 0 H 0 km/s/Mpc redshift <=> scale factor parsecs: light years: Functions. z = (λ observed - λ rest) / λ rest. The effect of dark energy on the galaxy formation epoch has been studied by Alcaniz and Lima (2001) [24] . The earliest epochs of the universe lie at a z of about 100. z tells you the number of years the light from the object has traveled to reach us, however this is not the distance to the object in light years, because the universe has been expanding as the light traveled and the object is now much farther away. That explains why sometimes a story will come out that says a galaxy has a redshift of z=1 or something like that.