It would seem that the modern understanding of the structure of the universe is already well established and generally accepted. But from time to time, it has to be defended against so-called anomalies, unexplained deviations from the norm that call the standard model into question. Let's talk today about how a strange cosmological phenomenon, by its nature and some coincidence of circumstances, called the "Axis of Evil", almost broke modern cosmology.
Echo of the Big Bang
The Earth looks into the sky with thousands of telescope eyes. Several dozen more are placed in orbit. The first telescopes were optical and were designed to observe the light part of the spectrum of electromagnetic radiation, which is accessible to the human eye. Modern ones peer into the bottomless space and observe its objects in the entire spectrum of electromagnetic radiation. Take the Swift space observatory, for example. It is designed to register and observe cosmic gamma-ray bursts - gigantic bursts of energy observed in distant galaxies. Place shortwave gamma radiation at the very beginning of the electromagnetic spectrum. The Russian orbital observatory Radioastron studies black holes and neutron stars in the radio range, closer to the other end of the spectrum.
Some orbiting observatories are better known, some less. Topping the popularity rating is the Hubble Space Telescope, which has been in orbit for 27 years. He studies space in the visible, ultraviolet and infrared ranges. Kepler is also widely known, equipped with a supersensitive photometer operating in the range of 430–890 nm (visible and infrared ranges) and capable of simultaneously observing the brightness fluctuations of 145,000 stars.
But among them there are orbital observatories, the main purpose of which is not individual stars, planets or galaxies, but the Universe itself. The purpose of finding them in orbit is to help astronomers understand the structure of our Universe, to try to understand its history. And perhaps, and see through the wall of incredible distances and other universes.
Launched by NASA in June 2001, the WMAP (Wilkinson Microwave Anisotropy Probe) observatory was one of those. The device was designed to study the background relic radiation that was formed as a result of the Big Bang. Until October 2010, it was 1.5 million km from the Earth in orbit near the Lagrange point L2 of the Sun-Earth system. In the period from 2001 to 2009, he scanned the celestial sphere and transmitted the results of observations to Earth. Based on the data obtained by the telescope, a detailed radio map of the sky was compiled at several electromagnetic wavelengths: from 1.4 cm to 3 mm, which corresponds to the microwave range.
The relic radiation fills the Universe evenly. This background microwave radiation, which arose in the era of primary hydrogen recombination, is a kind of "echo" of the Big Bang. It has a high degree of isotropy, that is, uniformity in all directions. Its radiation spectrum corresponds to the radiation spectrum of an absolutely black body with a temperature of 2.72548 ± 0.00057 K. The maximum radiation falls on electromagnetic waves with a length of 1.9 mm and a frequency of 160.4 GHz (microwave radiation). Without going into details, on the electromagnetic radiation scale it is between thermal infrared radiation and frequencies of cellular communications, radio and television broadcasting. The microwave background radiation is isotropic with an accuracy of 0.01%. This is exactly what the alternation of "warm" orange and "cold" blue areas on the radio maps of spacecraft indicates. It has some small scale anisotropy.
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In 2010, the observatory completed its mission. Just as WMAP once replaced the Cosmic Background Explorer (COBE) observatory, also known as Explorer 66, and it was replaced by the more sensitive and modern European Planck Observatory located at the same L2 point … Planck has a higher sensitivity and a wider frequency range.
Comparison of results from COBE, WMAP and Planck. An illustration of how different the sensitivity of their measuring instruments is
wikipedia.org
Pierced by the axis
The main provision of modern cosmology, on which most modern models of the structure of the Universe are based, is the so-called cosmological principle. According to him, at the same moment in time, every observer, wherever he is and in whatever direction he looks, will find, on average, the same picture in the Universe.
This independence from the place of observation, the equality of all points in space is called homogeneity. And independence from the direction of observation, the absence of a preferred direction in space, that is, the fact that the Universe does not prefer one direction to another, is isotropy. And its absence is anisotropy.
Everything would be fine, but only in the process of processing the data obtained by the WMAP probe, conclusions were made about just such anisotropy of the Universe. The results of the data analysis showed the presence in space of a certain extended area around which the orientation of the entire structure of the Universe takes place. That is, in space, there is still a direction in which galaxies and large space objects are lined up. This phenomenon, capable of breaking the modern concept of the Universe, was called the "Axis of Evil". The term itself was coined by the Portuguese physicist and cosmologist João Magueijo working in the UK.
The blue areas are the coldest, the orange areas are the “warmest”. White line - "Axis of Evil". Outlined with an oval - Eridani's Supervoid
wikipedia.org
This name is believed to be associated not so much with the "geometry" of the phenomenon, but with the influence that the phenomenon can have on the current prevailing ideas about the Universe. Among other things, a few years earlier, US President George W. Bush introduced the same term in relation to countries that, according to the United States, sponsor international terrorism and pose a threat to peace and stability on the planet.
It should be noted that our Universe has some inhomogeneity and anisotropy. Otherwise, there would be no galaxies, no stars, no planets. And, in the end, you and me too. These are all deviations from the homogeneity of the universe. The cosmological principle applies to very large scales, well beyond the size of a galaxy cluster. We are talking about hundreds of millions of light years. On a smaller scale, inhomogeneity is possible as a consequence of quantum fluctuations caused by the Big Bang.
Mageiju, observing the "warm" (orange) and "cold" (blue) regions of fluctuations of the microwave background radiation, made an interesting discovery. He found that even on the largest scales, fluctuations in the relict radiation (temperature fluctuations) are not randomly located, but relatively ordered.
A separate example of such anisotropy manifestation is a relic cold spot in the constellation Eridanus. Here, microwave radiation is significantly lower than in the surrounding areas. Nearly a billion light-years across, the Eridani Supervoid has far fewer stars, gas, and galaxies than usual.
There is no exact understanding of what could have caused such a gaping hole. Professor Laura Mersini-Houghton of the University of North Carolina gives this fascinating explanation: "This is definitely an imprint of another universe beyond our own."
Seemed?
And in 2009 ESA launched the more advanced Planck telescope into orbit. The spacecraft had two instruments on board for studying the sky: a low-frequency receiver covering the frequency range from 30 to 70 GHz, which corresponds to wavelengths from about 4 to 10 mm, and a high-frequency receiver with a frequency from 100 to 857 GHz and wavelengths from 0, 35 to 1 mm. The collected radiation is focused on the instruments by a system of two mirrors - the main one, measuring 1.9 by 1.5 m, and the secondary one, the size of which is 1.1 by 1.0 m. The telescope's receivers were cooled to almost absolute zero, operating at a temperature of –273, 05 ° C, that is, 0.1 ° C above absolute zero. Observation of the sky "Planck" continued until the depletion in January 2012 of liquid helium cooling the receivers.
Telescope "Planck" at the Lagrange point L2 of the Sun - Earth system
popsci.com
He had to refute the results obtained by WMAP, or, on the contrary, confirm them. And the first analysis of the obtained data, carried out in 2013, showed that the "Axis of Evil" in the Universe really exists. But at that time all the data received by the spacecraft had not yet been published.
It was only last year that a team of researchers at University College London (UCL) and Imperial College London, based on the results of an analysis of a complete dataset from a telescope, established that there really is no "axis". The data obtained from the telescope between 2009 and 2013 was analyzed using a supercomputer. The results of the analysis showed: the Universe is isotropic. The study by British astronomers was published in May 2016 by Physical Review Letters.
Daniela Saadeh, a research cosmologist at the Department of Physics and Astronomy at University College London, who took part in the study, does not hide her joy: "We can say that we saved cosmology from a complete revision."
In an explanation of the study's findings posted on the college's website, Daniela explains: “The study's results are the best evidence that the universe is the same in all directions. Our current understanding of the structure of the universe is based on the assumption that it does not prefer one direction to another. But you need to understand that Einstein's theory of relativity, in principle, does not deny the possibility of the existence of unbalanced space. Universes that rotate or stretch may well exist, so it is very important that this is not the case in our case. Although we, of course, cannot completely rule out this, but our calculations indicate that the probability of this is only one in 121,000."
Scanning the celestial sphere with the Planck telescope
esa.int
Sergey Sobol