Hubble reveals: dark energy has existed for at least 9 billion years

This is after a three-year study of exploding stars. The researchers used the Hubble Space Telescope to locate such stars in deep space

Dark energy - the mysterious force accelerating the expansion of the universe - has been with us for at least the last 9 billion years. This is the conclusion of astronomers who presented the results of a three-year study using the Hubble Space Telescope. The findings may rule out some alternative theories that the strength of dark energy changes over time. Dark energy makes up at least 70 percent of the universe, and the rest is mostly dark matter (25%) and normal matter (5%). "It seems as if dark energy accelerated the expansion of the universe already 9 billion years ago," said co-researcher Adam Rice of the Space Telescope Science Institute in Baltimore, out of the total 13.7 billion years of the universe - most of the life of the universe. The findings are consistent with the idea that dark energy behaves exactly like Einstein's cosmological constant. The cosmological constant describes the idea that there is density and pressure in "empty" space. In this scenario, dark energy never changes, and has the same properties throughout the universe.  repulsive forceEinstein first became convinced of the existence of a repulsive force in space in his attempt to discover the balance of the universe against the internal push of its own gravity, which he believed to be the main cause of the universe's inward collapse. Its cosmological constant remained a curious hypothesis until 1998, when astronomers used observations of supernovae taken by ground-based telescopes and the Hubble Space Telescope to show that the expansion of the universe was indeed accelerating. The findings lead the scientists to believe that there is indeed a repulsive force against the gravitational force in space, a force known as "dark energy". Since then many attempts have been made to explain the nature of dark energy. One of these properties is the behavior similar to the cosmological constant, another property is that dark energy behaves like a field that changes over time. Alternatively, a change to the theory of attraction is proposed in order to explain the mysterious force. The latest data from the Hubble Space Telescope contradicts the theory that dark energy may have behaved differently billions of years ago compared to its behavior today, or may not even have existed. Some astronomers believe that dark energy was supposed to mimic the dominant force of the universe at the time, for example matter. Previous Hubble observations of the most distant supernovae known revealed that the early universe was dominated by matter whose gravity slowed the expansion of the universe. The observations also confirmed that the rate of expansion of the universe began to accelerate 5-6 billion years ago. This is the time when astronomers believe that the repulsive force of dark energy has taken over that of gravity. "Rope pulling"Imagine that there is a tug-of-war competition and that the other side suddenly disappears behind a screen. Someone else is on the other side. We call it dark energy, said Dr. Rice. "In 1998, we saw that the side that hides behind the screen is the winning side. He pulled harder and the universe accelerated. In 2004 we realized that this was not always the case. There were times when our side – the normal stuff – won. The universe has slowed its expansion. Now we show that even at that time the thing on the other side of the rope had already begun to pull." The discovery came from analyzing observations of 23 exploding stars or supernovae. Using Hubble to dig deep into the universe, astronomers were able to see back to a time when the universe was less than half its current age. "These supernovae provide markers that allow us to measure the expansion rate of the universe 9 billion years ago," said Rice. Understanding the nature of dark energy is without a doubt the main problem of physics today, says Mario Livio, from the Space Telescope Science Center." In October, NASA said that the Hubble Space Telescope will have a service mission, and it may not crash due to a malfunction in one of the essential components. for further readingThe space telescope The Hubble will undergo an upgrade Yuval Ne'am: All our knowledge of physics covers 5% of the universe To download the image in high resolution