What is the farthest star from the earth. How far is the edge of the Universe from the most distant galaxy? Cosmic merger of galaxies
The science
A newly discovered celestial object is vying for the title of the most distant observable space object in the Universe from us, astronomers reported. This object is a galaxy MACS0647-JD, which is located 13.3 billion light years from Earth.
The universe itself is believed to be 13.7 billion years old, so the light we see from this galaxy today is from the very beginning of the cosmos.
Scientists observe the object using NASA space telescopes "Hubble" And "Spitzer", and these observations were made possible with the help of a natural cosmic “magnifying lens”. This lens is actually a huge cluster of galaxies whose combined gravity warps space-time, producing what is called gravitational lens. When light from a distant galaxy passes through such a lens on its way to Earth, it is amplified.
Here's what a gravitational lens looks like:
“Such lenses can magnify the light of an object so much that no human-made telescope can do it.”, - speaks Marc Postman, astronomer from Scientific Institute Baltimore Space Telescope. - Without such magnification, it takes a Herculean effort to see such a distant galaxy."
The new distant galaxy is very small, much smaller than our Milky Way- said the scientists. This object, judging by the light that has reached us, is very young; it came to us from an era when the Universe itself was at the very early stage of its development. It was only 420 million years old, which is 3 percent of its modern age.
The small galaxy is only 600 light years wide, but as you know, the Milky Way is much larger - 150 thousand light years wide. Astronomers believe that the galaxy MACS0647-JD eventually merged with other small galaxies to form a larger one.
Cosmic merger of galaxies
"This object may be one of many building blocks of some larger galaxy,- say the researchers. – Over the next 13 billion years, it could have undergone dozens, hundreds or even thousands of mergers with other galaxies or their fragments."
Astronomers continue to observe even more distant objects as their observing techniques and instruments improve. The previous object to hold the title of the most distant galaxy observed was galaxy SXDF-NB1006-2, which is located 12.91 billion light-years from Earth. This object was seen using telescopes "Subaru" And "Kek" in Hawaii.
In May 2015, the Hubble telescope recorded an outbreak of the most distant, and therefore oldest, galaxy known to date. The radiation took as much as 13.1 billion light years to reach Earth and be detected by our equipment. According to scientists, the galaxy was born approximately 690 million years after the Big Bang.
One would think that if the light from the galaxy EGS-zs8-1 (namely, this is the elegant name scientists gave it) flew towards us for 13.1 billion years, then the distance to it would be equal to that which the light will travel during these 13 ,1 billion years.
Galaxy EGS-zs8-1 is the most distant galaxy discovered to date But we must not forget some features of the structure of our world, which will greatly affect the calculation of distance. The fact is that the universe is expanding, and it is doing so at an accelerating rate. It turns out that while the light traveled 13.1 billion years to our planet, space expanded more and more, and the galaxy moved away from us faster and faster. A visual representation of the process is shown in the figure below.
Given the expansion of space, the most distant galaxy EGS-zs8-1 in this moment is located approximately 30.1 billion light years from us, which is a record among all other similar objects. It is interesting that up to a certain point we will discover more and more distant galaxies, the light of which has not yet reached our planet. It is safe to say that the EGS-zs8-1 galaxy record will be broken in the future.
This is interesting: There is often a misconception about the size of the universe. Its width is compared with its age, which is 13.79 billion years. This does not take into account that the universe is expanding at an accelerating rate. According to rough estimates, the diameter of the visible universe is 93 billion light years. But there is also an invisible part of the universe that we will never be able to see. Read more about the size of the universe and invisible galaxies in the article ““.
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Astronomers from Texas A&M University and the University of Texas at Austin have discovered the most distant galaxy known to us. According to spectrography, it is located at a distance of approximately 30 billion light years from solar system(or from our Galaxy, which is in in this case not so significant, because the diameter of the Milky Way is only 100 thousand light years).
The most distant object in the Universe received the romantic name z8_GND_5296.
"It's exciting to know that we are the first people in the world to see it," said Vithal Tilvi, PhD, co-author of the paper, which has now been published online (to view for free scientific works use sci-hub.org).
The discovered galaxy z8_GND_5296 formed 700 million years after big bang. Actually, we see it in this state now, because the light from the newborn galaxy has only now reached us, having traveled a distance of 13.1 billion light years. But since in the process the Universe expanded, at this moment, as calculations show, the distance between our galaxies is 30 billion light years.
The interesting thing about newborn galaxies is that there is an active process of formation of new stars. If in our Milky Way While one new star appears per year, in z8_GND_5296 there are approximately 300 per year. We can now safely observe what happened 13.1 billion years ago through telescopes.
The age of distant galaxies can be determined by the cosmological redshift, caused, among other things, by the Doppler effect. The faster an object moves away from the observer, the stronger the Doppler effect manifests itself. Galaxy z8_GND_5296 showed a redshift of 7.51. About a hundred galaxies have a redshift greater than 7, meaning they formed before the Universe was 770 million years old, and the previous record was 7.215. But only a few galaxies have their distance confirmed by spectrography, that is, by the Lyman alpha spectral line (more on it below).
The radius of the Universe is at least 39 billion light years. It would seem that this contradicts the age of the Universe at 13.8 billion years, but there is no contradiction if we take into account the expansion of the very fabric of space-time: for this physical process There is no speed limit.
Scientists are not entirely clear why they cannot observe other galaxies up to 1 billion years old. Distant galaxies are observed by a clear manifestation of the L α (Lyman alpha) spectral line, which corresponds to the transition of an electron from the second energy level to the first. For some reason, in galaxies younger than 1 billion years, the Lyman alpha line appears increasingly weaker. One theory is that it was at that time that the Universe transitioned from an opaque state with neutral hydrogen to a translucent state with ionized hydrogen. We simply cannot see galaxies that are hidden in a “fog” of neutral hydrogen.
How was z8_GND_5296 able to break through the neutral hydrogen fog? Scientists speculate that it ionized the immediate surroundings, so that protons were able to break through. Thus, z8_GND_5296 is the very first galaxy known to us that emerged from the opaque mess of neutral hydrogen that filled the Universe in the first hundreds of millions of years after the Big Bang.
In the vast expanses of the Internet, I somehow came across the following picture.
Of course, this small circle in the middle of the Milky Way is breathtaking and makes you think about many things, from the frailty of existence to the limitless size of the universe, but the question still arises: how true is all this?
Unfortunately, the creators of the image did not indicate the radius of the yellow circle, and judging it by eye is a dubious exercise. However, the authors of Twitter @FakeAstropix asked the same question as me, and claim that this picture is correct for about 99% of the stars visible in the night sky.
Another question is how many stars can you see in the sky without using optics? It is believed that up to 6,000 stars can be observed with the naked eye from the surface of the Earth. But in reality, this number will be much less - firstly, in the northern hemisphere we will physically be able to see no more than half of this amount (the same is true for residents of the southern hemisphere), and secondly, we are talking about ideal observation conditions, which in reality are practically impossible to achieve. Just look at the light pollution in the sky. And when it comes to the most distant visible stars, then in most cases we need ideal conditions to notice them.
But still, which of the small flickering points in the sky are the farthest from us? Here is the list that I have managed to compile so far (although of course I wouldn’t be at all surprised if I missed a lot of things, so don’t judge too harshly).
Deneb- the most bright Star in the constellation Cygnus and the twentieth brightest star in the night sky, with an apparent magnitude of +1.25 (the limit of visibility for the human eye is considered to be +6, maximum +6.5 for people with truly excellent vision). This blue-white supergiant, which is between 1,500 (last estimate) and 2,600 light-years away, means that the Deneb light we see was emitted sometime between the birth of the Roman Republic and the fall of the Western Roman Empire.
Deneb's mass is about 200 times the mass of our star, and its luminosity is 50,000 times greater than the solar minimum. If he were in the place of Sirius, he would sparkle in our sky brighter than the full Moon.
P The swan is painted red
Mu Cephei also known as Herschel's Garnet Star, a red supergiant, possibly the largest star visible to the naked eye. Its luminosity exceeds the solar one from 60,000 to 100,000 times; the radius, according to recent estimates, can be 1500 times greater than the solar one. Mu Cephei is located at a distance of 5500-6000 light years from us. The star is at the end of its life path and will soon (by astronomical standards) turn into a supernova. Its apparent magnitude varies from +3.4 to +5. It is believed to be one of the reddest stars in the northern sky.
Plaskett's Star is located at a distance of 6600 light years from Earth in the constellation Monoceros and is one of the most massive systems double stars in the Milky Way. Star A has a mass of 50 solar masses and a luminosity 220,000 times greater than that of our star. Star B has approximately the same mass, but its luminosity is lower - “only” 120,000 solar. The apparent magnitude of star A is +6.05, which means it can theoretically be seen with the naked eye.
System Eta Carina is located at a distance of 7500 - 8000 light years from us. It consists of two stars, the main one - a bright blue variable, is one of the largest and most unstable stars in our galaxy with a mass of about 150 solar, 30 of which the star has already lost. In the 17th century, Eta Carinae had a fourth magnitude; by 1730 it became one of the brightest in the constellation Carinae, but by 1782 it had again become very faint. Then, in 1820, the star’s brightness began to sharply increase and in April 1843 it reached an apparent magnitude of −0.8, temporarily becoming the second brightest in the sky after Sirius. After this, the brightness of Eta Carinae rapidly fell, and by 1870 the star became invisible to the naked eye.
However, in 2007, the star's brightness increased again, it reached magnitude +5 and became visible again. The star's current luminosity is estimated to be at least a million solar and it appears to be a prime candidate for being the next supernova in the Milky Way. Some even believe that it has already exploded.
In conclusion, it is worth mentioning that there have been cases in history when people were able to observe much more distant stars. For example, in 1987, a supernova erupted in the Large Magellanic Cloud, located 160,000 light-years away, and was visible to the naked eye. Another thing is that, unlike all the supergiants listed above, it could be observed over a much shorter period of time.