Starship Asterisk*

by **Ann** » Thu Apr 07, 2022 8:01 pm

Click to play embedded YouTube video.

Do watch this video, where Dr. Becky explains why astronomers believe that Earendel is a star.

Ann

by **Ann** » Thu Apr 07, 2022 5:32 am

Uncle Jeff wrote: ↑Thu Apr 07, 2022 2:38 am Why is this blip thought to be a "star" when equally fuzzy blips are galaxies?

There is a pretty good explanation in Sky & Telescope.

A lot of it has to do with mathematical modeling of how gravitational magnification works. The star Earendel and its galaxy, the Sunrise Arc, have been magnified by a foreground cluster.

The cluster’s gravitational lens had distorted the distant galaxy’s light into a long, thin crescent that the team nicknames “Sunrise Arc” in the current study. (Look through the bottom of a wine glass to see a similar arcs on less astronomical scales.)

But not all of the galaxy is magnified and distorted in the same way. Just as light passing through rippled water produces ripples of its own on the bottom of the swimming pool, the galaxy’s light ripples too, with some parts of it more highly magnified than others. The most highly magnified points are those on what astronomers call the critical curve.

“As objects approach the critical curve, their magnification increases,” Welch says. “For very small objects, such as stars, they can occasionally align so precisely with the critical curve that their magnification increases dramatically, up to a factor of thousands.”

Note that Earendel is located exactly on the critical curve (the dotted line). Also note that the critical curve is just a "line of magnification" as seen from the Earth.

Welch and his colleagues fit the Hubble images with multiple gravitational-lens computer models. They keyed the models to other star clusters in the Sunrise Arc galaxy, two of which appear on either side of Earendel, their light split into multiple images. (Only one of these clusters is labeled in the image above.) The star itself isn’t split, which suggests it’s nearer to the critical curve than the star clusters are.

We see just one image of the star, but two images of a star cluster close to Earendel. That was one of the clues used by astronomers to conclude that Earendel is a star located exactly on the critical curve of magnification as seen from the Earth.

The models also calculate the size of the star: less than about 2 light-years across and possibly far smaller than that. The size rules out the possibility that what Hubble has spotted is a star cluster — it’s more likely to be a single star.

: The Pleiades, 8 light-years across. Image: NASA, ESA, AURA/Caltech, Palomar Observatory

For comparison, how big is the Pleiades cluster? According to Sky & Telescope, the size of the central bright (mini dipper shaped) cluster is 8 light-years. The size of the small light source that astronomers gave the name Earendel is less than 2 light-years across, and possibly far less.

So as you can see, the identification of Earendel as a star has very much to do with mathematical modeling.

Ann

by **VictorBorun** » Thu Apr 07, 2022 4:57 am

Uncle Jeff wrote: ↑Thu Apr 07, 2022 2:38 am Why is this blip thought to be a "star" when equally fuzzy blips are galaxies?

The host galaxy WHL0137-zD1 aka Sunrise Arc is lensed into a long arc.
The WHL0137-LS aka Earendel is at a point that is lensed most, by 1000 … 40000 times, and yet remains a dot.
So it must be real small.

At a redshift of 6.2 ± 0.1, all the things we see have angular distance of 3 billion light years, so the lensing by 1000 … 40000 times must have shortened it to just 3 million ly … 75 kly. This is how we see Andromeda and Magellanic Clouds (save the red shift and the lense distortion). The thing can not be more than a light year in size; too small for a globular stellar cluster

by **Uncle Jeff** » Thu Apr 07, 2022 2:38 am

Why is this blip thought to be a "star" when equally fuzzy blips are galaxies?

by **VictorBorun** » Thu Apr 07, 2022 1:01 am

Ann wrote: ↑Wed Apr 06, 2022 4:45 am By distance I mean travel time, disregarding the fact that the expansion of the Universe has carried the distant galaxies still farther away from us since the light that reaches us from them was emitted.

Time travel distance is informative of how long it was since the object emitted the light we captured.
When all the picture we get is just a point, it's a good indicator of the distance.

For a galaxy / a galaxy cluster / a filament between voids / a spot in the CBR map, however, I think we better use the distance as it was when the object emitted the light we capture.
The diameter of a galaxy divided by the distance to that galaxy is angular size of the galaxy in the picture we get.
And this angular size is not affected by the expansion of the space.
So that kind of distance is the most informative for a galaxy at a pic.

IMHO this kind of distance is used less than it should.

In fact there is a reason why the people are shy of it: for galaxies far, far away this kind of distance is counter-intuitively getting smaller for earlier galaxies.
Real early galaxies we get too see with greater angular sizes, or as more closely, than some later galaxies, that can be in front of the early galaxies yet are seen with smaller angular sizes, at a greater distance.

The turning point when the galaxies are seen the smallest is at z=1.5, with travel time of 6 billion years.
When we look at an earlier galaxy (possibly obscured by a 6 billion years travel time distant galaxy) we see a closer, and angularily larger galaxy. The light it emitted toward us had been getting farther away from us — for some time, till the moment of 6 billion years ago.
I mean the total amount of space between us had been expanding more quickly than the photons were travelling across.
As the photons covered, say, a million light years, the space between those photons and our place expanded, say, by a 2 million ly, so the photons found themselves 1 million ly further from their final destination.
Then the expansion of space slowed down, and after 6 billion years ago the progress of the photons became positive; in the end they reached us and made a picture of the galaxy.

by **VictorBorun** » Wed Apr 06, 2022 10:10 pm

Now to make simple things complex, the falling of the Hubble Parameter throughout the history was not uniform.

1.

For the first second of time since the Big Bang the H parameter was falling especially quickly because the matter was relativistically hot: as the space expanded by 2 times and the volume of the space expanded by 8 times the density fell by 16 times because the relativistically hot particles were losing their mass by 2 times.

2.

After 10 billion years since the Big Bang the density fell so low that the second inflation began to be significant: that of the dark energy. Before that the density of the dark energy was negligible, but it is not falling with the space expansion; so as the density of trivial matter, dark and normal, approaches 0, the total density approaches not zero but the density of the dark energy.
So the H parameter is approaching not 0, but a final non-zero constant level.
Today 2/3 of the the total density is of dark energy and 1/3 of the total density is of trivial dark matter and normal matter.
The way things are going the 2/3 will remain forever, so 2/3 of today's H² will remain forever; H will become Hubble Constant = 56 km/s by megaparsec.

by **VictorBorun** » Wed Apr 06, 2022 9:48 pm

Ann wrote: ↑Wed Apr 06, 2022 4:45 am Why does the redshift grow so much larger so quickly the closer we get to the Big Bang?

Since the end of Inflation the matter that remains is mostly trivial: its density is falling as the space is expanding.
The speed of the space expansion is called Hubble Parameter, H.
Fridman's cosmologic equation says

H² = density

So, H is falling, too.
So, in the past H was large, the space expansion was quick, the density was falling quickly, and H was falling quickly.

z=1000 at 0.38 million years since the Big Bang
The recombination of the proton-electron plasma into hydrogen atoms and the birth of the 3000°K relict photons
(now seen as 3°K photons)

z=6 at 900 million years since the Big Bang
The Earendel blue giant stellar system shines in an early galaxy the Sunrise Arc
(now seen as a 7 times colder object)

by **BillBixby** » Wed Apr 06, 2022 9:13 pm

Thank you, again, Chris.
I was using Doppler, not cosmological. My limited sonar experience and love of trains had me on the wrong track.
Bill

by **Chris Peterson** » Wed Apr 06, 2022 8:55 pm

BillBixby wrote: ↑Wed Apr 06, 2022 8:44 pm
Chris Peterson wrote: ↑Wed Apr 06, 2022 6:46 pm
BillBixby wrote: ↑Wed Apr 06, 2022 6:37 pm APOD robot link
hubblesite.org/contents/news-releases/2022/news-2022-003
lists redshift, I think, incorrectly. If I am correct, does anybody have a contact at NASA who might correct this error?

“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, or 30 percent of its current age, at a time that astronomers refer to as "redshift 1.5." Scientists use the word "redshift" because as the universe expands, light from distant objects is stretched or "shifted" to longer, redder wavelengths as it travels toward us.”
The reference is to the "previous single-star record holder", which does have a redshift of 1.5, which does correspond to when the Universe was a bit over 4 billion years old.
Thank you, Chris, for taking time to reply. I thought REDShift was for things moving AWAY from us and BLUEShift for things overtaking (toward) us. So, the previous record holder has a REDShift of 1.5, and is coming toward us? Yes, the light is traveling toward us, but from a star moving away from us, therefore redshift, moving away, not toward as stated in the NASA news release. If that is correct, then what remains of my mind is malfunctioning. Wouldn't be the first time.

Bill

Technically, cosmological redshift isn't about things moving away, but about the effect of space expanding while the light is traveling toward us. Not the same as Doppler redshift. But for most purposes, we can treat them as largely the same.

A redshift of 1.5 is produced by an object for which the light has been traveling towards us for 9.4 Gyr, and the object has been traveling away from us during that time (or more precisely, space has been expanding so the distance between us is increasing). Any positive redshift value means something is moving away from us.

by **BillBixby** » Wed Apr 06, 2022 8:44 pm

Chris Peterson wrote: ↑Wed Apr 06, 2022 6:46 pm
BillBixby wrote: ↑Wed Apr 06, 2022 6:37 pm APOD robot link
hubblesite.org/contents/news-releases/2022/news-2022-003
lists redshift, I think, incorrectly. If I am correct, does anybody have a contact at NASA who might correct this error?

“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, or 30 percent of its current age, at a time that astronomers refer to as "redshift 1.5." Scientists use the word "redshift" because as the universe expands, light from distant objects is stretched or "shifted" to longer, redder wavelengths as it travels toward us.”
The reference is to the "previous single-star record holder", which does have a redshift of 1.5, which does correspond to when the Universe was a bit over 4 billion years old.

Thank you, Chris, for taking time to reply. I thought REDShift was for things moving AWAY from us and BLUEShift for things overtaking (toward) us. So, the previous record holder has a REDShift of 1.5, and is coming toward us? Yes, the light is traveling toward us, but from a star moving away from us, therefore redshift, moving away, not toward as stated in the NASA news release. If that is correct, then what remains of my mind is malfunctioning. Wouldn't be the first time.

Bill

by **Ann** » Wed Apr 06, 2022 7:47 pm

Chris Peterson wrote: ↑Wed Apr 06, 2022 6:46 pm
BillBixby wrote: ↑Wed Apr 06, 2022 6:37 pm APOD robot link
hubblesite.org/contents/news-releases/2022/news-2022-003
lists redshift, I think, incorrectly. If I am correct, does anybody have a contact at NASA who might correct this error?

“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, or 30 percent of its current age, at a time that astronomers refer to as "redshift 1.5." Scientists use the word "redshift" because as the universe expands, light from distant objects is stretched or "shifted" to longer, redder wavelengths as it travels toward us.”
The reference is to the "previous single-star record holder", which does have a redshift of 1.5, which does correspond to when the Universe was a bit over 4 billion years old.

: This image shows the the huge galaxy cluster MACS J1149.5+223, whose light has taken over 5 billion years to reach us. Highlighted is the position where the star LS1 appeared — its image magnified by a factor 2000 by gravitational microlensing. The galaxy in which the star is located can be seen three times on the sky — multiplied by strong gravitational lensing. Credit: NASA, ESA, S. Rodney (John Hopkins University, USA) and the FrontierSN team; T. Treu (University of California Los Angeles, USA), P. Kelly (University of California Berkeley, USA) and the GLASS team; J. Lotz (STScI) and the Frontier Fields team; M. Postman (STScI) and the CLASH team; and Z. Levay (STScI)

Wikipedia wrote:

MACS J1149 Lensed Star 1, also known as Icarus, is a blue supergiant star observed through a gravitational lens. It is the second most distant individual star to have been detected so far (second only to WHL0137-LS, a.k.a. Earendel, as of March 2022), at approximately 14 billion light-years from Earth (redshift z=1.49; comoving distance of 14.4 billion light-years; lookback time of 9.34 billion years).Light from the star was emitted 4.4 billion years after the Big Bang.

Ann

by **Chris Peterson** » Wed Apr 06, 2022 6:46 pm

BillBixby wrote: ↑Wed Apr 06, 2022 6:37 pm APOD robot link
hubblesite.org/contents/news-releases/2022/news-2022-003
lists redshift, I think, incorrectly. If I am correct, does anybody have a contact at NASA who might correct this error?

“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, or 30 percent of its current age, at a time that astronomers refer to as "redshift 1.5." Scientists use the word "redshift" because as the universe expands, light from distant objects is stretched or "shifted" to longer, redder wavelengths as it travels toward us.”

The reference is to the "previous single-star record holder", which does have a redshift of 1.5, which does correspond to when the Universe was a bit over 4 billion years old.

by **BillBixby** » Wed Apr 06, 2022 6:37 pm

APOD robot link
hubblesite.org/contents/news-releases/2022/news-2022-003
lists redshift, I think, incorrectly. If I am correct, does anybody have a contact at NASA who might correct this error?

“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, or 30 percent of its current age, at a time that astronomers refer to as "redshift 1.5." Scientists use the word "redshift" because as the universe expands, light from distant objects is stretched or "shifted" to longer, redder wavelengths as it travels toward us.”

by **TitaniumMithril** » Wed Apr 06, 2022 3:35 pm

I had to register just to mention that "Earendel" (later Eärendil) is a prominent character in early Tolkien mythology - the only man to ever sail west and reach Valinor (kind of Elvish heaven). He did so to plea to the Valar (demi-gods) to save Middle Earth from the evil Vala Melkor. After the literally-earth-rending battle that ensued, the Valar filled his ship with a shining white flame and put Earendel and his ship into the sky to become the evening star in the west - the "Star of High Hope" to those in Middle Earth.

by **orin stepanek** » Wed Apr 06, 2022 12:51 pm

Kitty says; " the farther we can see; the more we
want to see" !

Today's APOD> +1

by **Ann** » Wed Apr 06, 2022 11:36 am

NASA revealed the news of its discovery of Earendel the day after us Asteriskian*s were told about Art Neuendorffer's passing. I think I will always associate Earendel with Art.

The portrait of Alfred E. Neuman has been made from stickers. I apologize for some un-Art-like stickers about Trump and Brexit.

Ann

by **Ann** » Wed Apr 06, 2022 10:52 am

: Earendel: A Star in the Early Universe. Note the two images of the same star cluster to the left and the right of Earendel. Image Credit: NASA, ESA, B. Welch (JHU), D. Coe (STScI); Processing: A. Pagan (STScI)

Multiple images of a blue background galaxy being magnified by
foreground galaxy cluster CL0024+17. Image: NASA, ESA, M.J. Jee and H. Ford

The reason why the star Earendel is being so enormously magnified is that it is located exactly on the "maximum magnification line" produced by the foreground cluster. And the reason why the "mirrored star cluster" next to Earendel is seen twice (to the left and the right of Earendel) is because this cluster is not located perfectly on the magnification line created by the cluster. So it is just one cluster, but we see two images of it.

Gravitational lensing not only magnifies background objects, but extremely often it also splits them into multiple images. Take a look at the blue background galaxy being magnified by foreground galaxy cluster CL0024+17 in the picture at right. The image of this background galaxy is seen at least five times, possibly six. I am uncertain about the galaxy image that I have labeled "4 ?".

The reason why we don't see multiple images of Earendel is also, the way I understand it, that Earendel is perfectly located on the magnification line created by the foreground cluster.

Ann

by **Ann** » Wed Apr 06, 2022 4:45 am

Chris Peterson wrote: ↑Wed Apr 06, 2022 4:24 am
APOD Robot wrote: ↑Wed Apr 06, 2022 4:05 am Explanation: Is Earendel the farthest star yet discovered? This scientific possibility started when the Hubble Space Telescope observed a huge cluster of galaxies. The gravitational lens effect of this cluster was seen to magnify and distort a galaxy far in the background. This distorted background galaxy -- so far away it has a redshift of 6.2 -- appears in the featured image as a long red string, while beads on that string are likely to be star clusters. The galaxy cluster lens creates a line of maximum magnification line where superposed background objects may appear magnified many thousands of times. On the intersection between the galaxy line and the maximum magnification line is one "bead" which shows evidence of originating from a single bright star in the early universe -- now named Earendel. Future investigations may include more imaging by Hubble to see how Earendel's brightness varies, and, quite possibly, by the new James Webb Space Telescope when it becomes operational later this year.Â Earendel's great distance exceeds that of any known stable star -- although the star that exploded creating GRB 090423 had a redshift of 8.2.
z = 6.2 equates to a light travel time of about 12.8 Gyr.
z = 8.2 equates to a light travel time of about 13.1 Gyr.

In a universe with an age now placed at about 13.7 Gyr.

Thank you, Chris! I have been looking for an easy way to calculate the distances to very far away objects from their redshifts. (By distance I mean travel time, disregarding the fact that the expansion of the Universe has carried the distant galaxies still farther away from us since the light that reaches us from them was emitted.)

I have not found an easy way to calculate distance from redshift, because even the simplest calculation tool required me to fill in at least two (or was it three?) extra numbers or factors apart from the redshift z, one of which was the Hubble constant, H₀.

Is H₀ generally taken to be about 70 km/s² these days?

And why does the redshift grow so much larger (seemingly almost exponentially larger) the closer we get to the time of Big Bang? SN Refsdal, a supernova magnified several times in several places, had a lookback time or travel time of 9.34 Gyr, but its redshift was "only" z = 1.49. Earendel, with a lookback time of 12.8 Gyr, some 3.5 Gyr farther back in time than SN Refsdal, is redshifted by z = 6.2. And the supernova that was seen at a travel time of 13.1 Gyr, only 300 million years before Earendel, has a redshift of 8.2.

Why does the redshift grow so much larger so quickly the closer we get to the Big Bang?

Ann

by **Chris Peterson** » Wed Apr 06, 2022 4:24 am

APOD Robot wrote: ↑Wed Apr 06, 2022 4:05 am Explanation: Is Earendel the farthest star yet discovered? This scientific possibility started when the Hubble Space Telescope observed a huge cluster of galaxies. The gravitational lens effect of this cluster was seen to magnify and distort a galaxy far in the background. This distorted background galaxy -- so far away it has a redshift of 6.2 -- appears in the featured image as a long red string, while beads on that string are likely to be star clusters. The galaxy cluster lens creates a line of maximum magnification line where superposed background objects may appear magnified many thousands of times. On the intersection between the galaxy line and the maximum magnification line is one "bead" which shows evidence of originating from a single bright star in the early universe -- now named Earendel. Future investigations may include more imaging by Hubble to see how Earendel's brightness varies, and, quite possibly, by the new James Webb Space Telescope when it becomes operational later this year.Â Earendel's great distance exceeds that of any known stable star -- although the star that exploded creating GRB 090423 had a redshift of 8.2.

z = 6.2 equates to a light travel time of about 12.8 Gyr.
z = 8.2 equates to a light travel time of about 13.1 Gyr.

In a universe with an age now placed at about 13.7 Gyr.

by **bystander** » Wed Apr 06, 2022 4:12 am

viewtopic.php?t=42301

by **APOD Robot** » Wed Apr 06, 2022 4:05 am

Earendel: A Star in the Early Universe

Explanation: Is Earendel the farthest star yet discovered? This scientific possibility started when the Hubble Space Telescope observed a huge cluster of galaxies. The gravitational lens effectÂ of this cluster was seen to magnify and distort a galaxy far in the background. This distorted background galaxy -- so far away it has a redshift of 6.2 -- appears in the featured image as a long red string, while beads on that string are likely to be star clusters.Â Â The galaxy cluster lens creates a line of maximum magnification line where superposed background objects may appear magnified many thousands of times. On the intersection between the galaxy line and the maximum magnification line is one "bead" which shows evidence of originating from a single bright star in the early universe -- now named Earendel. Future investigations may include more imagingÂ by Hubble to see how Earendel's brightness varies, and, quite possibly, by the new James Webb Space Telescope when it becomes operational later this year.Â Earendel's great distance exceeds that of any known stable star -- although the star that exploded creating GRB 090423 had a redshift of 8.2.

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