How big is the universe?

To calculate large, accurate calculations on a galaxy or cosmic scale, one needs an exact constant to make the landmark. It can be said that Hubble's constant is the same as Pi's for circles.

Those who learn about astronomy know the universe is always expanding. But the pace of expansion, even the most eminent scientists do not dare to claim accurately.

People named the Hubble Constant . Modern measurements have not been able to reach the conclusion of this constant value, because every different measurement gives a different value.

Artwork Quasar ULAS J1120 + 0641 has energy from a black hole 2 billion times bigger than the sun.(Photo: ESO).

What is the Hubble constant for?

For a long time, there were two explanations for the existence of: One was that it was already there, two that it started from a point. The first theory was rejected in late 1960, when it was confirmed that the Big Bang explosion had given birth to the universe.

As early as 1920, scientist Edwin Hubble was paying attention to the questions surrounding the Big Bang. How long has this explosion occurred? How big is this universe?

Using technologies similar to today's radar guns, Hubble knows that galaxies not only move away from Earth, but also apart. The relationship between the velocity of galaxies and their distance from the Earth is shown by Hubble's constant.

Thanks to the Hubble constant, people were able to answer the first question above. The Big Bang explosion occurred about 13.7 billion years ago.

Measurement of the rate of expansion of the universe

The basic idea of ​​measuring the rate of expansion of the universe or the value of the Hubble constant, is to observe light sources from a distance. Specifically, it is from supernova explosions (the explosion that ends the life of a star) or quasars (Quasar - extremely distant, extremely bright object with characteristic redshift). These light sources are strong enough and far enough for scientists to measure the intensity of the red-shift of the light from them.

Red shift phenomenon is the light when an object is away from the viewer tends to turn to the red wavelength, due to the Doppler effect between two mobile light sources. The bigger the redshift, the faster the object moves away. Therefore, if we measure the exact number, we will calculate the rate of expansion of the universe.

The rate of expansion of the universe is calculated in Kilometers per Second / Megaparsec (kps / Mpc), symbolized (km / s) / Mpc. This unit is simply understood: Suppose there is a certain space expanding at a speed of 10 (km / s) / Mpc, which means that 2 points in that space are separated by 1 megaparsec (3.26). million light-years), and travel 10 kilometers farther apart.

When scientists first discovered the universe was expanding in 1920, the scientists estimated the rate of expansion to be 625 kps / Mpc. But since the 1950s, more accurate measurements have shown this speed to be less than 100 kps / Mpc. In recent decades, many studies have suggested that the rate of space expansion is about 76-77 kps / Mpc.

However, the result must be an exact number, not a series of numbers. This number is important because it is the benchmark for other physical proportions in the universe. Without exact figures, astronomers cannot measure the size of galaxies, or the expanding history of the universe.

Every physical and scientific innovation we have on Earth is extremely small. To calculate larger, more accurate calculations at the galactic or cosmic scale, one needs an accurate constant to make the landmark. The Hubble constant can be compared to the universe as well as the Pi constant to the circle.

However, a recent study will probably solve that problem by observing quasars and gravity lenses in the universe.

Gravity lenses in the universe

Gravitational lens - gravity is actually not an object like the optical lens of a camera, but a phenomenon.

Galaxies or black holes are often so massive, that any light passing through them is bent. That is the phenomenon of gravity lens. Unlike optical lenses, light is most strongly bent at the center of gravity, weakening when it reaches the edge of a black hole or galaxy (optical lenses do not bend light shining directly at an angle of 90 degrees through it) bend light at the edge of the lens).

As such, any light from distant quasars or supernovae to Earth must pass a black hole or galaxy, and they will be bent by the gravity lens phenomenon.

Hubble noted that a red galaxy is bending the light of a green galaxy much farther away.This is the phenomenon of gravity lenses.(Source: ESA).

Quasars and landmarks of the universe

The quasars are extremely distant and extremely bright, with very large red (shirt) motion. In the visible light, the quasar looks like a normal star, a point light source. In fact, it is the light emitted from solid matter halo, located around the nucleus of active galaxies (young galaxies), usually supermassive black holes.

Because the quasars are so bright, they are easily seen from a great distance and become the leading research group of objects. The latest research shows they can be a clue to calculating Hubble constants when combined with gravity lens phenomena.

Scientists have found clues in a double quasar. A double quasar is not two quasars close together like a double star or double galaxy. It is an image of a single quasar whose light is bent by a gravitational lens and follows two paths to reach Earth.

Studying two images of the same quasar shows that they have a delay every time the parent quasar flashes. By measuring the time delay between two times, combined with the known mass of the lens galaxy, the scientists calculated the distance from the Earth to the lens galaxy and the quasar. Knowing the redshifts of both galaxies and quasars allows scientists to calculate the rate of expansion of the universe.

After years of observing the double quasar SDSS J1206 + 4332 , combining dozens of data from Hubble glass and COSMOGRAIL space gravitational lens observation network, scientists calculated the delay between two flashes of the quasar , giving the most accurate Hubble constant calculation ever.

'The beauty of this measurement is that it is independent of previous measurements , ' says Tommasso Treu, the author of the study.

The lens galaxy is marked with G0 in the image.A and B are pictures of double quasar SDSS J1206 + 4332.G2 is the galaxy is triplets.G3 and G4 are nearby galaxies.(Photo: Hubble Space Telescope).

The team concludes that the value of the Hubble constant is 72.5 kps / Mpc . This result is consistent with the measurements used from these, but 7% higher than those using cosmic microwave background radiation (electromagnetic radiation generated from the early universe, roughly 380,000 years after the Big Bang).

It is still not possible to end, because if there are any errors between the different measurement methods for the same constant, the cosmic magnitude has yet to be "solved". Even all three measurements may be wrong. The team intends to look for more distant quasars to be able to give a more accurate measurement of the cosmological constant of expansion.