Thursday, December 01, 2022

Hubble: ‘Single star’ detected at record distance



They called it the nickname “Earendel” and it is the furthest single star still imaged by a telescope.

The light of this object took 12.9 billion years to reach us.

It is at this kind of distance that telescopes can normally only solve galaxies containing thousands of stars.

But the Hubble Space Observatory selected Earendel individually by exploiting a natural phenomenon similar to the use of a zoom lens.

This is called gravitational lensing and it works as follows: If there is a large group of galaxies in the line of sight, the gravitational pull of this mass of matter will bend and magnify the light of further distant objects behind it.

Usually it’s just other galaxies, but in this particular case Earendel was in a sweat spot in the lens effect.

“We’re lucky. It’s really extreme; it’s really exciting to find something with such a high magnification,” says Brian Welch, a PhD student at Johns Hopkins University in Maryland, USA. “If you happen to hit that real sweat spot, as we have in this case, the magnification can grow to factors of 1000s,” he told BBC News.

The previous record maker was a star named Icarus. Again, captured by Hubble, this star was observed nine billion light-years in the distance.

Earendel is therefore considerably further away. We see it only 900 million years after the Big Bang, or at a time when the Universe was only 6% of its current age.


After more than three decades of operation, Hubble continues to make remarkable discoveries

The name Earendel comes from an Old English word meaning “morning star” or “rising light”. It’s not much to look at in the Hubble photo – just a dull lump on a long crescent of light created by the lens called the “Sunrise Arc”.

Mr Welch and colleagues report the star’s discovery in the journal Nature. There is still a lot to learn about its properties, the authors admit.

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For example, there is uncertainty about Earendel’s size. It is at least 50 times the mass of our own Sun, but depending on the exact amount of magnification it can be much larger. However, even at 50 solar masses, it would be one of the largest stars ever observed.

It’s very likely that what Hubble spied on was a binary. That is, they are actually two stars orbiting each other. This is very common. In such cases, however, there is usually a larger measure and it is this object’s light that will dominate the signal.

Some astronomers will question whether Earendel is not just a tight group of many stars, but Mr. Welch said there are limits to how large the phenomenon can be before the lens effect begins to smear the light into a more elongated, cigar-like shape. He is confident that Hubble has tracked down one, or at most two stars.

One alternative explanation could be that the spot of light is an object in the foreground that happens to have a similar light profile. Certain failed stars, or brown dwarfs as they are known, may fit the data. But the probability is low. After five years of observations, the feature remained totally static in the field of view. If it were a much closer brown dwarf, its position in the air would be expected to float slightly.

Comparison Of Hubble And James Webb

Comparison of Hubble and James Webb

A fascinating piece of speculation surrounding Earendel is its composition. There is a way the data can be interpreted to suggest that it is a pioneer star, an object made from the pristine gas created in the Big Bang.

Theory tells us that the very first stars that shone in the universe existed only hydrogen and helium. Astronomers call them Population III stars. Only when these stars and their descendants fused heavier elements did the cosmic environment change to the one we recognize around us today.

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But a star of 50 solar masses would only burn for a very short time, perhaps at most a million years before it would run out of fuel and collapse and die. For a pioneer star to exist 900 million years after the Big Bang, it would have to grow from a long-surviving, isolated and unpolluted gas cloud. Not impossible, but probably a bit too far.

“Yes, we expect Earendel to be more likely to be a star that is a bit enriched in heavier elements, but not as much as the local stars around us today,” Mr Welch said.

“There’s a small chance that it’s a Population III star. A few other studies suggest you can find them in the orbits of some galaxies. But this is something we’ll follow in much more detail from other telescopes like James. going to need. Webb. “

James Webb is the successor to Hubble. It was launched in December and has a much larger mirror and superior analytical tools. It will be able to tease details that are outside of Hubble.

Webb will start full-time science activities in two or three months. Mr Welch and colleagues have already found time on the new observatory to go and look at Earendel.

But it’s worth celebrating Hubble’s continued brilliance for a moment. It was launched in 1990 and even as a new wonder observatory prepares to take over the reins, Hubble continues pioneering studies.

“The Hubble Space Telescope is doing very well,” said Dr Jennifer Wiseman, a Nasa project scientist.

“It’s powerful. It’s as scientifically productive as ever, and we’re looking forward to the kind of science Hubble is going to do in the years to come. We’m especially excited about the James Webb Space Telescope, which is also working in space with Hubble. “By having both of these wonderful facilities. We’re going to learn more about the Universe than we have ever been able to.”

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