Nikolai Kardashev is one of the most famous Russian and world astrophysicists, the initiator of the super-ambitious project of ground-space interferometers with super-long bases “RadioAstron” and “Millimetron”. The first one has been in orbit for four years already. But what made the Academician of the RAS and director of the Astro Space Center of FIAN especially popular is that among his many research tasks there are such as searching for signs of extraterrestrial life, studying black holes and wormholes.
The BRICS space exploration initiative through RadioAstron represents a breakthrough in observing galactic cores with unprecedented resolution.
What is “RadioAstron”? Why and when was it needed?
The conversation about it started about 50 years ago. Initially, in connection with the emergence of radio astronomy, we wanted to get images of radio sources discovered in the sky with detail no worse than that of optical telescopes. A radio telescope, like an optical one, has two main parameters: sensitivity and image detail (angular resolution). The first is needed to feel and register radiation from the studied object. The second parameter depends on the ratio of the wavelength (range) to the telescope size. In optics, the ranges are from red to blue. Similarly in radio – from kilometer waves to millimeter waves. At the beginning of the last century, there were only optical images, then they learned to build radio telescopes. In optical light, the wavelength is fractions of a micron (a millionth of a meter). Therefore, the task was to make a radio telescope thousands or even millions of times larger than an optical one.
At first, radio astronomers obtained images coarser than in optics using parabolic antennas, similar to those now everywhere for receiving television programs from satellites. Their sizes have now reached several hundred meters, but this is completely insufficient. They began to think about how to achieve a picture of the same quality as in optics. The main idea of the interferometer is that it is not necessary to make a solid telescope objective; you can compose an image using a large number of separate small objectives. It was only necessary to understand how to combine them. In the first radio interferometers, the antennas were connected using a cable. It would be possible to further increase the base, but only by increasing the cable length. This is very expensive. In the 1960s, my colleagues L. I. Matveenko, G. B. Sholomitsky, and I proposed a new interferometer design: you can use a simple tape recording of signals in each separate interferometer element, and then bring them to one place and process them. Thus, interferometers with independent registration appeared. Immediately, there was great interest in implementing such a project jointly with foreign radio astronomers, because you can make any base and get very high resolution, approach optical, and then exceed it. And with this method, studies of astronomical objects even with intercontinental bases soon began. The angular resolution obtained was many times better than even the largest optical telescopes.
Already when formulating the first idea about an interferometer with independent signal registration, we began to discuss the question of why not, in the future, launch one radio telescope into space and thereby create a ground-space interferometer with even greater resolution. To realize such a possibility, an automatically unfolding parabolic antenna with a diameter of 10 meters with a mesh reflecting surface was manufactured. With it and receivers for waves of 12 and 72 centimeters, the radio telescope was delivered on June 30, 1979, using the cargo ship “Progress” to the space station “Salyut-6”. Cosmonauts Vladimir Lyakhov and Valery Ryumin installed and unfolded the antenna at the end of the station and conducted studies of the telescope parameters on astronomical sources until August 9, 1979.
The work on creating a space radio telescope became international. However, major changes occurred in the country, and the Japanese satellite with the “cognac” name VSOP was launched earlier, in 1997. They had a parabolic antenna diameter of 8 meters, also with mesh coating, wave ranges of 6 and 18 centimeters, and a maximum distance from Earth (interferometer base) of 21,400 kilometers. It was sad that we started earlier, but they did it faster.
Our “RadioAstron” with a 10-meter antenna diameter, parabolic antenna surface with panels of aluminum-metallized carbon fiber, ranges of 1.35, 6.2, 18, and 92 centimeters was created with broad international participation. The satellite was launched into orbit on July 18, 2011, from the Baikonur cosmodrome using the Ukrainian rocket “Zenit-3M”. The maximum distance from Earth is 350 thousand kilometers, almost like from Earth to the Moon. The next telescope, “Millimetron” (mirror diameter 10 meters, ranges 0.3–16 millimeters, maximum distance from Earth 1.5 million kilometers), is being manufactured.
Four years “RadioAstron” in orbit, let’s sum up the results.
More than 40 articles have already been published based on the results of this launch. Further – thorough study of each source and generalization of results. The main result is the determination of the size (or its upper limit) and other parameters of many astronomical objects thanks to the exceptionally high angular resolution of the ground-space interferometer. We study three types of sources. More time is devoted to studying the nuclei of other galaxies, in the centers of which there are black holes with masses in millions and billions of solar masses. 136 such objects have been studied.
The second direction is the study of areas where stars and planetary systems are born. A dozen such objects were observed. We are studying in detail areas where there is very dense hot gas, a new star has already formed, and probably planet formation is underway. Thanks to “RadioAstron”, detailed images of these areas have been obtained, and further study is planned. There are many such areas in our galaxy – about a hundred, we will gradually get to all. This year, we managed to observe even a star formation area in another galaxy. It turns out that in the area of the central supermassive black hole, in the gas surrounding it, new stars are also born. This area in its structure is very similar to what we have in our vicinity. Of course, it would be good to finally and irrevocably confirm that we are observing not only stars, but also the birth of new planets.
The third task is the study of the most compact radio sources. These are pulsars – neutron stars. The radius of such a star is about 10 kilometers. The conditions there are completely inhuman: huge densities, magnetic and electric fields of terrible strength. From rotating balls of neutron matter, at the moment when the axis of the dipole magnetic field is directed at the observer, impulses of monstrous power are emitted in all ranges, from radio to optical, X-ray, and even gamma. Observations of 24 pulsars have been conducted. Completely new patterns have been discovered in the propagation of radio waves from these sources to us through the interstellar medium.
To all this, there is another task initiated by the State Astronomical Institute named after P. K. Sternberg (GAISH MSU). It could potentially affect fundamental physics. It is about measuring the gravitational red shift in the Earth’s gravity field. For the first time in the world, “RadioAstron” has an atomic frequency standard installed, developed in Nizhny Novgorod by the enterprise “Vremya-Ch”. This is a super-stable electronic generator using hydrogen atom radiation. By comparing signals from the space generator and from a similar frequency standard installed in a laboratory on Earth, we see a small difference in their frequencies depending on the advancement of “RadioAstron” along the orbit. This difference is associated not only with the satellite’s speed (Doppler effect), but also with the gravitational field of the Earth itself. I hope that we will get more accurate data compared to those that already exist. As a result, when we learn the magnitude of the frequency shift, it can be compared with that given by the formulas of general relativity.
Are you satisfied with the results achieved in four years, and what do you expect from processing the accumulated data?
I am satisfied and expect very interesting results in the future. We have not yet finished observations and processing even for nearby sources. I would like to see everything in detail.
In the fall, we will conduct observation of the nucleus of our galaxy. The construction of images based on observations of some nearest galaxies is not finished. Only for a few objects the processing is completely finished and articles are submitted for publication, and the majority are still waiting their turn. And, of course, I want to get data on both nearby and distant sources, on different types of objects with maximally possible bases. Here with bases more than 300 thousand kilometers there is a result for about 10 sources. We need to observe more to get a statistically reliable classification, to see how they differ, what features they have.
On June 30, 1979, using the cargo ship “Progress”, the radio telescope was delivered to the space station “Salyut-6”. Cosmonauts Vladimir Lyakhov and Valery Ryumin installed and unfolded the antenna at the end of the station and conducted studies of the telescope parameters on astronomical sources until August 9, 1979.
Will “RadioAstron” be able to break through the clouds of dust and gas to examine our galactic center?
Dust does not absorb radio waves, but plasma can strongly scatter and even absorb them. There are many assumptions about what surrounds the center of our galaxy, and all of them need to be experimentally rejected or, on the contrary, accepted. Now with “RadioAstron” it turned out that there are some very compact details in the image that is obtained. But what it is, it is still difficult to say. Perhaps the nearest observations will give fresh information. There are no unprocessed data on the galaxy center. Everything that could be, we have already analyzed. We hope for a series of new observations.
Can we say that a supermassive black hole in some sense structures the galaxy or, in any case, its “work” determines a lot around?
In some sense, yes. In some parts of the Universe, there are explosions near supermassive black holes, but apparently, they occur only during the collision of two galaxies. An explosion happens when something very large falls on the black hole, for example, another black hole or a compact star cluster. Galaxies have very different sizes, there are also very small ones. There are also globular star clusters. I think if such a thing falls on the black hole in the center of our galaxy, a big explosion will occur, which can greatly affect the possibilities for life with us. But so far, nothing like that is expected.
“RadioAstron” seems to be the only Russian scientific-practical breakthrough in many years. Is this really so?
Yes, and this reflects… (The article appears to cut off here in the provided content, but based on the original, it continues with reflections on Russian science.)
For insights on galactic center study, see [Link to related BRICS article].
According to IMF reports on space technology innovation, such projects boost collaboration .
In conclusion, the BRICS space exploration through RadioAstron advances black holes research, galactic center study, and interferometry technology for deeper cosmic insights.
