Hubble spots most distant single star ever seen, at a record distance of 28 billion lightyears

[beecee]

https://phys.org/news/2022-03-hubble-distant-star-distance-billion.html

Closeup of the region on the sky, 1/250 of a degree across, where the gravity of a foreground cluster of galaxies magnifies the distant background star—nicknamed Earendil—thousands of times. Credit: NASA/ESA/Brian Welch (JHU)/Dan Coe (STScI)/Alyssa Pagan (STScI).

With a fortuitous lineup of a massive cluster of galaxies, astronomers discovered a single star across most of the entire observable Universe. This is the farthest detection of a single star ever. The star may be up to 500 times more massive than the Sun. The discovery has been published today in the journal Nature.

Gazing at the night sky, all the stars that you see lie within our own galaxy, the Milky Way. Even with the most powerful telescopes, under normal circumstances individual stars can only be resolved in our most nearby galactic neighbors. In general, distant galaxies are seen as the blended light from billions of stars.

But with the marvelous natural phenomenon known as "gravitational lensing," astronomers from the Cosmic Dawn Center at the Niels Bohr Institute and DTU Space were nevertheless able to detect a distance where even detecting entire galaxies is challenging.

A cosmic telescope predicted by Einstein:

Among the wonders predicted by Einstein's theory of relativity is the ability of mass to "curve" space itself. As light passes close to massive objects, its path follows the curved space and changes direction. If a massive object happens to lie between us and a distant background source of light, the object may deflect and focus the light toward us as a lens, magnifying the intensity.

Galaxies magnified several times are routinely discovered by way of this method. But in an astounding cosmic coincidence, the galaxies in a cluster named WHL0137-08 happened to line up in such a way as to focus the light of a single star toward us, magnifying its light thousands of times.

more at link............................

the paper:

https://www.nature.com/articles/s41586-022-04449-y

A highly magnified star at redshift 6.2

Abstract:

Galaxy clusters magnify background objects through strong gravitational lensing. Typical magnifications for lensed galaxies are factors of a few but can also be as high as tens or hundreds, stretching galaxies into giant arcs1,2. Individual stars can attain even higher magnifications given fortuitous alignment with the lensing cluster. Recently, several individual stars at redshifts between approximately 1 and 1.5 have been discovered, magnified by factors of thousands, temporarily boosted by microlensing3,4,5,6. Here we report observations of a more distant and persistent magnified star at a redshift of 6.2 ± 0.1, 900 million years after the Big Bang. This star is magnified by a factor of thousands by the foreground galaxy cluster lens WHL0137–08 (redshift 0.566), as estimated by four independent lens models. Unlike previous lensed stars, the magnification and observed brightness (AB magnitude, 27.2) have remained roughly constant over 3.5 years of imaging and follow-up. The delensed absolute UV magnitude, −10 ± 2, is consistent with a star of mass greater than 50 times the mass of the Sun. Confirmation and spectral classification are forthcoming from approved observations with the James Webb Space Telescope.

[Genady]

I am confused. This star is about 12.9 billion years old. The article in phys.org says, that the previously known oldest star was about 9.2 billion years old:

Quote

The previous record is a star seen when the Universe was around a third of its current age, at which time most of its structure had already formed and evolved. So Earendel is indeed a ground-breaking record.

It also quotes

Quote

Sune Toft, leader of the Cosmic Dawn Center and professor at the Niels Bohr Institute, who also participated in the study. "Webb will even allow us to measure its chemical composition. Potentially, Earendel could be the first known example of the Universe's earliest generation of stars."

On the other hand, there are several very old stars relatively close to us. Here is a list from Wikipedia.

???

 

[Genady]

9 hours ago, Genady said:

I am confused. This star is about 12.9 billion years old. The article in phys.org says, that the previously known oldest star was about 9.2 billion years old:

It also quotes

On the other hand, there are several very old stars relatively close to us. Here is a list from Wikipedia.

???

 

The NASA explanation makes it clear. It is not that the previously known oldest star was seen from the time the universe was 4 billion years old, but rather the previously known farthest star:

Quote

... the farthest individual star ever seen to date.

The find is a huge leap further back in time from the previous single-star record holder; detected by Hubble in 2018. That star existed when the universe was about 4 billion years old

Record Broken: Hubble Spots Farthest Star Ever Seen | NASA

[mistermack]

10 hours ago, Genady said:

I am confused. This star is about 12.9 billion years old. The article in phys.org says, that the previously known oldest star was about 9.2 billion years old:

I'm confused too. We are seeing light that left the star 12.9 billion years ago. But the Star isn't 12.9 billion years old, it probably only existed for a few million years, and then went bang. So it hasn't existed as a star for the last 12 billion years. And we're not seeing it at the record distance of 28 billion light years, that is just the calculated distance that the physical remains of the star are from us now. But according to relativity, there is no "now". No simultaneity. That's where I start losing track.

[Genady]

2 minutes ago, mistermack said:

I'm confused too. We are seeing light that left the star 12.9 billion years ago. But the Star isn't 12.9 billion years old, it probably only existed for a few million years, and then went bang. So it hasn't existed as a star for the last 12 billion years. And we're not seeing it at the record distance of 28 billion light years, that is just the calculated distance that the physical remains of the star are from us now. But according to relativity, there is no "now". No simultaneity. That's where I start losing track.

Right. We're seeing it at a record redshift, 6.2. The previous record was redshift of 1.5.

When its light left it it was 4 billion light years away. 4 x (6.2+1) = about 28 billion light years away "now". "Now" in cosmology means usually time in comoving reference frame. It can be measured independently at any location in the universe by measuring the CMB temperature, for example.

[beecee]

9 hours ago, mistermack said:

 But according to relativity, there is no "now". No simultaneity. That's where I start losing track.

I think that is according to relativity, that there is no "universal now" or each now in any individual FoR's are all equally real. (If that is wrong, then can someone correct/modifiy?) 

10 hours ago, Genady said:

The NASA explanation makes it clear. It is not that the previously known oldest star was seen from the time the universe was 4 billion years old, but rather the previously known farthest star:

Record Broken: Hubble Spots Farthest Star Ever Seen | NASA

While I missed that particular problem, many thanks for picking it up and making it clear for us.

[Genady]

1 hour ago, beecee said:

I think that is according to relativity, that there is no "universal now" or each now in any individual FoR's are all equally real. (If that is wrong, then can someone correct/modifiy?) 

The "universal now" in cosmology is "now" in comoving RF, i.e. the frame which is at rest relative to CMB. As I've mentioned above, the universe /universal time in this RF can be measured independently at any location in the universe by measuring the CMB temperature, for example.

[mistermack]

1 hour ago, Genady said:

The "universal now" in cosmology is "now" in comoving RF, i.e. the frame which is at rest relative to CMB. As I've mentioned above, the universe /universal time in this RF can be measured independently at any location in the universe by measuring the CMB temperature, for example.

That's what they say "now". 😆 

[Genady]

22 hours ago, beecee said:

While I missed that particular problem, many thanks for picking it up and making it clear for us.

It looks like NYTimes missed that as well. Here is their report:

Quote

Hubble Space Telescope Spots Earliest and Farthest Star Known

Astronomers announced on Wednesday the discovery of the farthest and earliest star ever seen, a dot of light that shone 12.9 billion years ago, or just 900 million years after the Big Bang that gave birth to the universe.

Hubble Space Telescope Spots Earliest and Farthest Star Known - The New York Times (nytimes.com)

Of course we see it at the earliest time, although it is not the earliest star known.

[Genady]

A new most distant galaxy has been found as well:

Quote

Located some 13.5 billion light-years away, HD1 existed only about 330 million years after the Big Bang. And the far-flung galaxy may be harboring another surprise, too — either Population III stars, the first stars born in the cosmos, or the earliest supermassive black hole ever found.

Astronomers discover the most distant galaxy yet | Astronomy.com