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What is the oldest star in the universe? What about the younger one?

The oldest known star, officially called HD 140283 but nicknamed Methuselah, lies 190.1 light-years away. Britain’s Schmidt Telescope (AAO) Anglo-Australian Observatory imaged the star in blue light for a digital sky survey. (Image credit: Digitized Sky Survey (DSS), STScI/AURA, Palomar/Caltech, UKSTU/AAO)

Among the myriad stars that sparkle in the vastness of space, some are so old that they have witnessed the dawning of the universe, and others are so small that even the most powerful telescopes on Earth have been unable to observe them. But is it possible to tell which star is the youngest and which is the oldest?

It is difficult to determine the smallest star in our universe because stars are constantly being born, but there are a few candidates among the stars that we know of. In contrast, scientists have known about the oldest recorded star – appropriately nicknamed Methuselah – for decades.

Stars are born deep in vast clouds of dust and gas known as nebulae. according to NASA (Opens in a new tab), some masses of gas in the nebula are overburdened with so much material that their own gravity forces them to collapse (because more mass means more gravity), and the intense gravitational pull at the center of the collapsing cloud causes gas – mostly hydrogen – to join what becomes a protostar. These stellar embryos begin fusing hydrogen nuclei into helium and emit radiation in the process. A star cannot be called a star until it radiates energy, which is what makes it so bright. Some dull stars sparkle in life.

New stars are forming all the time, but in 2022 astronomer Rubing Dong and his colleagues captured images of young stellar embryos in the constellation of the binary star system Z Canis Majoris. Turbulence caused by a cosmic intruder was captured by the Subaru Telescope, Karl Jansky Very Large Array, and Atacama Large Millimeter/ Millimeter Array. (Image credit: ALMA (ESO/NAOJ/NRAO), S. Dagnello (NRAO/AUI/NSF), NAOJ)

astronomer robing dong (Opens in a new tab), an assistant professor in the Department of Physics and Astronomy at Victoria University in Canada, observed these fledgling stars. He led a 2022 study in Nature Astronomy (Opens in a new tab) On a binary star system believed to be only about a million years old. Dong and colleagues were able to establish an approximate age for some of these stellar embryos. They often throw tantrums, known as accumulation fits.

“When stars experience cumulative eruptions, they get hotter and brighter,” Dong told Live Science in an email. “The matter around them is heating up. The ice in the protoplanetary disk may evaporate, and some chemical reactions may be triggered in the disk due to the heating of the material.”

As young stars are still accumulating material, they expel massive jets of gas, or gas streams, from either end as a result. This means that they are still accumulating mass. Because the outflows fade as they age, the amount of gas emitted helps astronomers estimate the age of the star. More gas means a younger star.

Meanwhile, estimates of the age of the star HD 140283, known as Methuselah, have sparked controversy. Preliminary estimates from observations made in 2000 indicate that it is 16 billion years old, according to NASA (Opens in a new tab). This would make it older than the universe, which is about 13.8 billion years old. Astronomers immediately suggested that there was an error in how the age of this star was calculated. If not, it raised the possibility that the universe appeared eons earlier than previously thought.

To get to the heart of the matter, astronomers used the Hubble Space Telescope to re-establish Methoslah’s age in 2013, coming up with an estimate of 14.5 billion years based on its brightness and its distance from Earth, which is about 190 lights. Years. This would make it slightly older than the universe, although there are error bars in estimating the age.

Related: What is the largest known star in the universe? (How about the younger one?)

“We measured the distance in order to determine the absolute luminosity, and therefore the age, with the help of theoretical studies of the evolution of stars,” said Howard Bond. (Opens in a new tab), an astronomer honorary at the Space Telescope Science Institute, the Hubble Space Telescope Operations Center in Maryland, who helped date Methusela. “We found a compatible age—within measurement uncertainties and theory With the age of the universe.

Methuselah is a giant star (Opens in a new tab)It’s brighter than most stars but still not as bright as giant stars, Bond told Live Science in an email, and they are so massive that their size appears out of the ordinary for their temperature and mass. Giants are also redder than giants. Stars release energy by burning hydrogen in their core and converting it to helium through it nuclear fusion. Massive stars reach a sub-giant stage when they begin to deplete their hydrogen reserves. At this point in a star’s life, its brightness or luminosity becomes an excellent way to estimate its age. Dim giant stars are older.

Methuselah is reddish and has been slowly fading over billions of years, although its relative proximity to Earth means it doesn’t look very faint to us and can be seen with the right binoculars. The sun hardly outlived by comparison. Our star is just under 5 billion years old and is expected to live about 5 billion more years when that happens It cools and swells so far in the solar system that it will It swallows the planets orbiting around it, including the Earth.

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