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Black energy is stranger than previously believed

Credit: Flickr/Hubble - ESA

A team of researchers have recently been looking at three super massif primitive black holes so that they can measure the rate of Universe expansion.  Once again, the results are unexpected.  The details of their study was published in Nature Astronomy.

Expansion of the Universe

A little before the 1920s Edwin Hubble made a discovery that revolutionised astronomy.  He discovered that galaxies move away from us as well as from one another.  In other words the universe is constantly expanding.  Imagine a muffin in the oven with some chocolate chips on top. As the muffin expands the distance between each chocolate drop also widens.  Twenty years ago researchers made another incredible discovery.  They discovered that more galaxies leak out of the Milky Way over time.  The Universe is therefore expanding but, more than that, this expansion is accelerating with time.  

We are aware of a repulsive material which is the opposite of gravity which seems to speed up the expansion of the Universe.  Astronomers have named this entity “black energy”.  This force is still mysterious but it appears that it is even more stranger than previously believed.  Until now we thought that there was a constant acceleration of Universe expansion.  However a study suggests that the force of black energy could have varied since the Big Bang. 

Quasars like “Standard candles”

One of the methods that is used to measure the rate of Universe expansion focuses on old supernovas, used as “standard candles”. By analysing the distance that separates us from these objects, on several time intervals, astronomers have quite a precise idea of this rate of expansion.  However the majority of these supernovas go back up to 9 billion years.  In other words we have no idea what the rate of Universe expansion was like during their youth.  This is where the quasars come into play.

Quasars are supermassive black holes that are found at the heart of galaxies.  They are the brightest objects in the Universe as a result of a disk of matter which swirl around it. Some of these ultra bright objects are more than 12 billion light years away.  (The Universe is 13.8 billion light years old.) A team of researchers from the University of Florence, in Italy have recently studied almost 1,600 of them.  By using these cosmic “candles”, astronomers can then estimate the rate of Universe expansion when it was still very young.  This rate which we thought was constant look like it wasn’t at all.

quasar
Quasar 3C 273,The brightest ever observed. Credits : NASA, Esa

Is black energy increasingly powerful?

We showed that results from our technique match up with those from supernova measurements over the last 9 billion years, giving us confidence that our results are reliable at even earlier times,” stated Elisabetta Lusso, of Durham University in England.  However by observing quasars that go back to a billion years after the Big Bang the researchers discovered  “that the universe’s expansion rate up to the present day was faster than we expected” which “could mean dark energy is getting stronger as the cosmos grows older,” explained Guido Risaliti, of the University of Florence in Italy and lead author of the study.

In other words, with these two methods using supernovas and quasars, the same results are obtained for the most recent 9 billion years.  However in a primitive Universe, where only quasars can be used to give measurements, we can see a difference in comparison to what was previously believed for the standard cosmological method.  If this is really the case we will perhaps need a new physic theory to explain this difference.

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