NASA's Hubble telescope helps scientists solve mystery of dead galaxies Why did some galaxies from the early universe suddenly stop making stars? Astronomers look back in time to find out.

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Why did some galaxies in the early universe suddenly stop forming stars? Astronomers look back in time to find out.

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The sleeping giant galaxy at the center of this image is 10 billion light-years away.


As mere mortals, we yearn to travel back in time—a passion nurtured by iconic contraptions like Marty McFly’s Car, Hermione Granger’s Time Turner, and Doctor Who’s Police Box. What is often forgotten, however, are real-life astronomers who already do this.

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Recently, one such research team harnessed time travel to solve a space mystery dating back billions of years, using a unique combination of super sensitive telescopes: Some of the universe’s early galaxies strangely put out stars. Stopped ejecting and inactive, or muted?

Galaxies are believed to be at the peak of their star-forming potential right now, so it’s especially surprising when we discover a dormant state. Right now, they should be making more stars than ever.

“The most massive galaxies in our universe formed incredibly early, right after the Big Bang,” Kate Whitaker, a professor of astronomy at the University of Massachusetts-Amherst and lead author of a new study, said in a statement. “But for some reason, they’ve stopped. They’re not making new stars anymore.”

It turns out, some older galaxies only ran low on star fuel, or cold gas, during their lifetimes. The group’s study results were published Wednesday in the journal Nature and could rewrite our knowledge of how the universe evolved.

But wait, you probably still have astronomers going back in time. If they can swing it, why didn’t they come to Stephen Hawking’s famous time-traveller-dinner party?

You may have heard the term “light-year,” which refers to the distance of light in one Earth year. We need this term as a measure because light does not travel instantaneously. Of course, turning on your bedroom lamp makes it glow almost instantly, but if someone standing on the Moon, about 238,900 miles (384,472 kilometers) away, turns on a flashlight, its rays won’t reach us for more than a second. Will be able to reach

That means moonlight is about a second lag for us Earthlings. In fact, when we look at the Moon, we are seeing everything a second after it happened. We are like looking back in time.

Astronomers extend that concept to billions. Using powerful telescopes as time machines, they see Deep Space – eg, billions of light years away. For example, for this study that unravels the mystery of premature “dying” galaxies, the team looked at six cosmic bodies 10 billion to 12 billion light-years away in the universe.

Therefore, it took 10 billion to 12 billion years for any light within the study area to reach their telescope lens. That means astronomers were looking far enough back in time to see the moments immediately after the Big Bang – which occurred about 14 billion years ago – unfold in real time.

Look and behold, this is how they solved the cosmic puzzle. The researchers say that galaxies either burn up too quickly from their supply of cold gas or are blocked from refilling.

More specifically, Whitaker and fellow researchers demystified the issue by using a mix of powerful telescopes: the Hubble Space Telescope and the Atacama Large Millimeter/submillimeter Array, or ALMA. The Hubble Space Telescope is sensitive to light across the spectrum – even the kind humans cannot see.

And as if time travel wasn’t hypothetical enough, the team took advantage of another tool called gravitational lensing to magnify the collected light. Originally, the lens’s approach traveled along a line punctuated by hundreds of other galaxy clusters.

The gravitational pull of those galaxies was so strong that rays of light coming from the team’s six galaxies pulled them in as they traveled to Earth. This helped shed light – no pun intended – on juicy details that would have otherwise been missed within the galaxies.

ALMA, on the other hand, used those details to look at the level of cold gas, or star fuel, that is needed to make galaxies into stellar bodies. “The early universe contained abundant cold gas, so these galaxies from 12 billion years ago must have had a lot left in the fuel tank,” Whitaker said.

Now we know – thanks to the closest approach to time travel – those tanks are emptied.

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