Age and size of the Universe:
How Hubble has calculated the age of the cosmos
and discovered the Universe is expanding at an ever
faster rate
The top ranked scientific justification for building Hubble was to determine the
size and age of the Universe through observations of Cepheid variables. The periodic brightness variations of these stars depends on physical properties of the stars
such as their mass and true brightness. This means that astronomers, just by looking
at the variability of their light, can find out about the Cepheids’ physical nature,
which then can be used to determine their distance.
Astronomers have used Hubble to observe Cepheids with extraordinary results.
The Cepheids have then been used as stepping-stones to make distance measurements for supernovae, which have, in turn, given a measure for the scale of
the Universe. Today we know the age of the Universe to a much higher precision
than before Hubble: around 13.7 billion years.
The expansion of the Universe
Another purposes of Hubble was to determine the rate of expansion of the Universe, known as the Hubble Constant. After eight years of Cepheid observations
this work was concluded by finding that the expansion increases with 70 km/second for every 3.26 million light-years you look further out into space.
For many years cosmologists have discussed whether the expansion of the Universe would stop in some distant future or continue ever more slowly. The observations of distant supernovae made by Hubble indicate that the expansion is nowhere near slowing down. In fact, due to some mysterious property of space itself,
called dark energy, the expansion is accelerating. This surprising conclusion came
from combined measurements of remote supernovae with most of the world’s
top-class telescopes, including Hubble.
The discovery of the accelerating expansion of the Universe led to three astronomers, Saul Perlmutter, Adam Riess and Brian Schmidt, being awarded the 2011
Nobel Prize in Physics.
This image shows a smoothed reconstruction of the total (mostly dark)
matter distribution in the COSMOS field, created from data taken by
the Hubble Space Telescope and ground-based telescopes. It was inferred from the weak gravitational lensing distortions that are imprinted
onto the shapes of background galaxies. The colour coding indicates the
distance of the foreground mass concentrations as gathered from the
weak lensing effect. Structures shown in white, cyan, and green are typically closer to us than those indicated in orange and red. To improve the
resolution of the map, data from galaxies both with and without redshift
information were used.
The new study presents the most comprehensive analysis of data from
the COSMOS survey. The researchers have, for the first time ever, used
Hubble and the natural “weak lenses” in space to characterise the
accelerated expansion of the Universe.
Credit: NASA, ESA, P. Simon (University of Bonn) and T. Schrabback
(Leiden Observatory)