When talking about distance on a cosmic scale, kilometres don’t make much sense as things will get out of hand very quickly.
Instead, astronomers and astrophysicists use light years (the distance light can travel in one year) to measure distance.
This week NASA shared the news that the Hubble Space Telescope has detected the light of star that existed in the first billion years of the big bang. This doesn’t mean it’s the oldest, but it is the farthest from Earth we’ve observed.
The star has been named Earendel which means morning star or brightest angel in old English and its light took 12.9 billion years to reach Earth. How does NASA know this?
Experts in the field use – among other data points – redshift to determine how old a star might be. Redshift is when light from distant stars stretches thanks to the expansion of the universe leaving us with longer, redder wavelengths. The degree to which a star has redshifted, gives an idea of how far away it may be.
“Normally at these distances, entire galaxies look like small smudges, with the light from millions of stars blending together,” explains Brian Welch, lead author of the paper describing this discovery at Johns Hopkins University. “The galaxy hosting this star has been magnified and distorted by gravitational lensing into a long crescent that we named the Sunrise Arc.”
The paper, “A highly magnified star at redshift 6.2” was published in the journal Nature this week.
“Earendel existed so long ago that it may not have had all the same raw materials as the stars around us today,” says Welch. “Studying Earendel will be a window into an era of the universe that we are unfamiliar with, but that led to everything we do know. It’s like we’ve been reading a really interesting book, but we started with the second chapter, and now we will have a chance to see how it all got started.”
But we need to rewind a bit because being able to see this star required something monumental to happen.
A galaxy cluster dubbed WHL0137-08 sits between Earth and Earendel, with NASA describing the galaxy as huge and for good reason. The gravitational pull of this galaxy warped the fabric of space-time to create a “powerful natural magnifying glass that distorts and greatly amplifies the light from distant objects behind it”.
This brightened Earendel’s light by a factor of a thousand or more giving astronomers a brilliant view of the star.
Because of the vast distances, NASA believes that Erandel will be observable for a few years yet and that means, we could point the most powerful space telescope built, the James Webb Space Telescope at Earendel and observe it.
“With Webb we expect to confirm Earendel is indeed a star, as well as measure its brightness and temperature,” Dan Coe who lead the Hubble RELICS (Reionization Lensing Cluster Survey) program where this data was gathered told NASA.
“We also expect to find the Sunrise Arc galaxy is lacking in heavy elements that form in subsequent generations of stars. This would suggest Earendel is a rare, massive metal-poor star,” Coe added.
This is quite frankly a monumental discovery and the fact that it was made using data from the ageing Hubble Space Telescope makes it even more impressive.
We are now even more excited for the James Webb Space Telescope to come online so that we can learn more about the vast expanse we call space.
