In the 21st century, astronomy continues to scrutinize the sky. Scientists are interested in objects around the solar system, including dangerous comets, as well as exoplanets, black holes, dark matter, the Big Bang and the evolution of the universe.
Does astronomy know everything about the sky?
Astronomy is a science born thousands of years ago. Scientists have accumulated knowledge for centuries. Most of the questions people usually ask about what is going on in heaven were answered decades or centuries ago.
But this does not mean that astronomers have nothing to study. Building huge telescopes (such as VLTs), using arrays of antennas like MeerKAT, and launching into orbit such super-sophisticated instruments as James Webb Space Telescope and Gaia — all of that is done to help scientists unravel new mysteries in the universe.
Objects on the outskirts of the solar system
Our own solar system is well studied today. We can confidently say that within the orbit of Neptune, all objects with a radius of more than 50 kilometers are already known to us. And then, behind the eighth planet, there are many mysteries.
It is still unknown whether Neptune is the last planet. The probability that we will find a large celestial body behind its orbit is very small, but enthusiasts continue to search. And even if another gas giant is not found there, the number of Pluto-like ice dwarfs still waiting to be discovered — dozens of them.
What to say about smaller bodies! Every year at least a dozen of comets fly from the far reaches of the solar system to the Sun. And theoretically, any of them could collide with our planet. As for asteroids the size of tens of meters, there are hundreds of them even near the Earth. Tracking these dangerous objects is such an important task that NASA is building new telescopes for it.
Exoplanets and the search for life
Astronomers are searching for rocky bodies outside the solar system. The last two large space telescopes, JWST and TESS, are primarily exoplanet hunters. Now the number of known worlds near other stars has reached 10 thousand. This is the point when one can move from the actual discoveries to the creation and verification of theories about the origin and evolution of these bodies, their climate and satellites.
Scientists are especially interested in exoplanets similar to the Earth. They have already discovered a considerable number of bodies that are similar in size to our world or receive the same amount of heat from their stars. Now it’s time to find out their chemical composition, climatic conditions and possibly find biomarkers. Biomarkers are the substances, the presence of which indicates the existence of earth-like life on a planet.
The evolution of stars, as seen by astronomy
The stars in the sky live their lives. They are born, evolve, change size and luminosity, and die, turning into white dwarfs, neutron stars or black holes. In general, this process is well studied by scientists, but many details were unseen to them. In particular, they are interested in the formation of planetary systems from gas-dust disks. The first images of this process were obtained only in the last decade.
The evolution of binary systems has also turned out to be extremely interesting. Currently, much of the research is devoted to exciting cases where one of the stars has already turned into a white dwarf, neutron star or black hole, and the other one continues to dump matter on it. From time to time, such systems flash like novae and emit X-rays and gamma rays.
Mapping the Universe
In addition to the question of “how”, scientists are still looking for an answer to the question “where”. Over the past ten years, the number of cataloged stars has grown from 2 million to several billion. We now know much more about other galactic objects, such as pulsars or nebulae. This is thanks to the European Space Agency’s Gaia telescope, which operates at the Lagrange point of the Sun-Earth system.
Since 2013, when it was launched into space, it has allowed scientists to determine positions in space, velocity and spectra of more than a billion stars. However, there are more than 400 billion of them in our Galaxy. So now we know less than a percent of their total. As for the rest, we can only guess about their existence itself.
Astronomy studies black holes
The most mysterious objects in the universe, black holes, have long remained purely theoretical. However, over the past 30 years, scientists have managed to find them. At first, watching the movement of the stars in the Milky Way, they learned that one of those holes is located right in the center of our galaxy. Then, thanks to the Horizon Telescope in 2019, we were able to see one of the largest black holes in the center of the distant galaxy M87. And finally, in 2022, our own supermassive central black hole was “photographed”.
Currently, scientists are most interested in the question of how the black holes of stellar mass, resulting from supernova explosions, turn into monsters that live in the centers of galaxies. In order to find the answer, you need to find objects of intermediate mass, which have not yet been observed.
We do not actually see most of the existing matter. And I’m not talking about gas-dust nebulae that hide from the light of the stars. Scientists working on the problems of the evolution of our universe are sure that it is impossible without the presence of some dark matter, which does not react with anything and manifests itself almost exclusively through gravitational interaction.
It is believed that around each galaxy there is a large amount of dark matter which affects the development of the galaxy itself. Now astronomers are coming up with various clever ways to map or at least detect these clouds. After all, so far no direct evidence has been received of the existence of this component of our world.
The big bang and the evolution of the universe
Finally, as for space outside the Milky Way, astronomers continue to study the origins and evolution of our universe as a whole. It is believed that he was born 13.7 billion years ago as a result of the Big Bang. But as an evidence of this we have only relic radiation in the radio range, the study of which remains one of the most important tasks of radio astronomy.
Astronomers continue to discover more and more ancient stars and galaxies, approaching the moment when they can say that one of those objects was among the first to appear in the universe. The study of the epoch of reionization has already begun — it is a faraway time, when the radiation of the first giant luminaries transformed the neutral atoms of hydrogen and helium into ions.
Once upon a time, the study of the motion of celestial bodies gave rise to the understanding that the world does not end with the horizon. People began to ask questions about how our universe is arranged. Astronomy still continues to find answers. And the end of this process, called “science”, will not be seen for a very long time.