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According to the British newspaper Daily Mail, astronomers recently gave the most accurate measurements of the rate of expansion of the universe to date. Recent measurements by a team of scientists using NASA's Spitzer Space Telescope show that the universe is expanding at a rate of about 46 miles (74 km) per second per million parsecs (more precisely: 74.3 ± 2.1 (km/s)/Mpc).

The American astronomer Edin Hubble first discovered at the beginning of the last century that the universe was in a state of constant expansion through a large number of meticulous observations, and that this expansion has been going on since the dawn of the universe.

According to the current mainstream scientific understanding, scientists believe that the universe was born in a big bang about 13.7 billion years ago, and since it is a violent expansion process, it will be crucial to calculate the speed of its expansion, this value is called the "Hubble constant", which is generally represented by a capital H in physics, and this value will be extremely critical for determining the age and size of the universe.

The Spitzer Space Telescope works in the longer wavelength infrared band, not the visible light band. Its latest measurements increase the accuracy of a similar observation previously conducted by the Hubble Space Telescope by three orders of magnitude, reducing the uncertainty range of this value to less than 3 percent, a major leap forward in the field of cosmological measurements. Astronomers say the latest precision is 74.3 ± 2.1 (km/s)/Mpc, with 1 million parsecs equivalent to about 3 million light-years.

Michael Erner is a Spitzer Project scientist from NASA's California Jet Propulsion Laboratory (JPL). "This time the Spitzer telescope has once again done a job that didn't belong to it," he said. Previously, it surprised us with its study of exoplanet atmospheres, but this time, it has become a powerful tool for cosmology. ”

The data from this discovery, combined with data previously published by NASA's Wilkinson Microwave Anisotropy Probe, will allow the scientists to make an independent dark energy measurement. Dark energy is one of the biggest unsolved mysteries in the universe.

In the late '90s, astronomers were shocked to discover that our universe was in fact expanding at an accelerated pace. This is a very abnormal phenomenon because the universe is full of matter and dark matter – both of which have mass and therefore both have gravity. Under these gravitational pulls, the universe should gradually slow down, or at least keep balance, even if it is expanding, but it should never be accelerating. In order to figure out the answer to this question, astronomers have had to conceive an "unknown mysterious force" that alone fights the gravitational pull of all matter and dark matter in the entire universe, and even defeats them all and pushes the universe to expand at an accelerated rate. Because scientists don't know anything about this mysterious and powerful force, people have given it a rightful name: "dark energy". Endy Freedman, the study's first author and director of the Carnegie Observatory in the United States, said: "It's a huge mystery. ”

"It's great that we can use the Spitzer Space Telescope to do this kind of research that touches on the most fundamental question of cosmology, which is the precise rate of expansion of the universe at this stage, and to measure the proportion of dark energy in the universe from another perspective," she said. ”

Since the wavelength is in the infrared band, the Spitzer Space Telescope can take the observations previously made by the Hubble Space Telescope in the visible light band one step further, because the Spitzer Telescope's field of view can penetrate dust and gas clouds and make better observations of a class of stars known as Cepheids compared to Hubble.

These variables are pulsating variables that are often used by astronomers as a measuring stick because of their apparent characteristics between their brightness and their luminous periods: we can measure the expansion rate of the universe by finding such variables at known distances and observing how fast they leave us.

Cepheids can be used as measuring scales because the distance between them and the Earth can be measured directly. In 1908, Henrietta Leavitt, a famous American female astronomer, noticed that there is a strict correlation between the brightness and the light period of a class of stars called Cepheids, which is the famous "periphotographic relationship".

To further illustrate why this nature is important, imagine a person who is moving away from you with a candle in his hand. As the person gets farther away, the candle in his hand will dim, so we can directly measure the brightness of the candle to get the distance from the candle to our location. The same is true for Cepheid variables in the universe, which are known as the "standard candles" in the universe. By measuring their brightness in the sky, astronomers can measure their distance.

The Spitzer telescope selected 10 in the Milky Way and 80 Cepheid variable stars in the nearby Large Magellanic galaxy for observation. Through these observations, the team was able to measure their brightness with greater accuracy and calculate their actual distance, thereby improving on previous measurements made on the subject. With this data, astronomers can take a step up the ladder of the cosmic scale to estimate the expansion rate of the entire universe.

"It was unthinkable to use the words 'exactly' and 'cosmology' in the same sentence just 10 years ago, when our understanding of the size and age of the universe was very vague, with errors of more than two orders of magnitude," Ms. Friedman said. "But we're talking about a few percentages of precision now, which is incredible," she said. A paper on the findings will be published in the Journal of Astrophysics in the near future. (