How Old is the Universe?

Hubble Space Telescope Deep Field

Hi! I?M Everyday Einstein, Sabrina Stierwalt, bringing you Quick and Dirty Tips that will help you make experience of technology.

Our universe is 13.8 billion years old, a timescale a lot longer than the extra relatable spans of masses or lots of years that effect our lived experiences. So how do astronomers arrive at such an considerable variety?

The universe, quite virtually, ought to at least be as old because the oldest thing we can locate in it. Thus, a direct test of the age of the universe is to head trying to find historical stars.

Stars in clusters, or agglomerations of stars, all born at the equal time, can be most appropriately age-dated by way of searching out what is known as the ?Main collection flip off? For the cluster. The longest level of a celebrity?S existence is spent burning hydrogen. During this segment, stars comply with a relation among their temperature and brightness called the primary sequence. In different phrases, hotter stars shine brighter.

Once a star runs out of hydrogen to burn, it will begin to cool and thus leave this main sequence relation before becoming a supergiant, a white dwarf or even a black hole. Based on our knowledge of stellar evolution, astronomers can estimate how long certain types of stars will continue burning hydrogen on the main sequence. Our Sun, a relatively low mass star, has been burning hydrogen for nearly 5 billion years and will continue to do so for another 4 to 5 billion more. Even though they have more fuel to burn, more massive stars spend a shorter time on the main sequence because they burn through that fuel much faster.

See also: Will the Sun Explode?

As a star cluster ages, the maximum massive stars leave the primary collection first, accompanied via stars of reducing mass. Observations of highly young famous person clusters will thus screen all varieties of stars filling out the main series. Older clusters will display a much less entire major series as the most big stars have already exhausted their hydrogen fuel and ?Became off? The main collection.

The most large stars nonetheless on the main collection (i.E. Nonetheless burning hydrogen) place a restriction at the age of the cluster. The oldest determined famous person clusters have ages in the range of eleven-13 billion years.

In a previous episode, we discussed the end stages of a dying star’s life and how a low mass star like our sun can evolve into white dwarf. White dwarfs are extremely dense objects that pack the equivalent of the Sun’s mass into the size of Earth. A teaspoon of white dwarf material weighs 15 tons!

Since white dwarfs are no longer burning elements through fusion to produce and emit radiation, they are instead left to cool much like the dying embers of a fire. The temperatures of white dwarf stars can thus tell us how long they have spent cooling and place a limit on their age.Observations with the Hubble Space Telescope find the oldest white dwarfs to be in the range of 12-13 billion years old.

WMAP image of the CMB

While age-dating the universe through ancient stars is an important check, the most direct determination of its age comes from relic radiation left behind from the Big Bang, called the cosmic microwave background radiation, or CMB for short.

Simply positioned, our universe is expanding as time is going on, leaving more and more space between us and our extragalactic acquaintances. We can flip returned the clock however, by using rewinding this enlargement, through the help of facts encoded in the CMB, to determine how long the universe has been increasing.

The CMB is radiation produced all through the Big Bang, the singularity that in a fragment of a 2nd began the mixture of high densities, temperatures, and pressures that later increased and cooled into the universe we study today. The CMB radiation has cooled notably as it has traveled, however it nevertheless encodes records from the Big Bang occasion. The CMB thus offers us the equivalent of a infant picture of our universe, a image of what came about in the starting.

The age of the universe is tied to a few cosmological parameters that collectively describe the expansion of the universe:

  1. the rate of expansion of the universe, known as the Hubble constant
  2. the density of both baryonic (normal) and dark matter in the universe (i.e. how much matter needs to be expanded)
  3. the cosmological constant, a parameter tied to the acceleration of that expansion

From very precise maps of the CMB made by space probes like WMAP and the Planck satellite, astronomers and physicists measure these parameters. From them, the determine an estimate of the age of the universe within the theoretical framework of Lambda Cold Dark Matter cosmology, which includes our understanding of what components make up the universe.

This technique finds the age of the universe to be thirteen.8 billion years antique, plus or minus 37 million years. This uncertainty within the age, that’s pretty small in comparison to a complete time of thirteen.Eight billion, comes from the uncertainties associated with measuring each of the 3 cosmological parameters.

To put this age in angle, the age of our Solar System is best about 4.5 billion years. Certain isotopes that have been created with the Solar System, like potassium and uranium, offer clues as to the age of our Solar System. These isotopes go through radioactive decay, and for that reason, provide a totally accurate size of the time elapsed on the grounds that their formation.

The fact that the age determined by the CMB is consistent with the minimum ages calculated for the oldest star clusters and white dwarf stars tells us astronomers that we are on the right track. Keep in mind, though, that we are defining the age of the universe as the time that has elapsed since the Big Bang. None of our observational evidence can tell us what may have happened before the Big Bang—a question that may be better answered by a theoretical astrophysicist or even a philosopher, rather than an observational astronomer.

Until next time, this is Sabrina Stierwalt with Everyday Einstein’s Quick and Dirty Tips for helping you make sense of science. You can become a fan ofEveryday Einstein on Facebook orfollow me on Twitter, where I’m@QDTeinstein. If you have a question that you’d like to see on a future episode, send me an email at

WMAP image of CMB courtesy of

Hubble Space Telescope Deep Field courtesy of

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