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Previously, the stars predicted fate, today they find new exoplanets. Astrophysicist Sergei Popov told Trends what is already known about our main star and how much more scientists have to learn.
The stars were originally the main object of study of astronomy, since they are quite easy to observe. Today, interest in them is experiencing a renaissance, only this time the stars become a kind of tool for observing other celestial bodies. So, scientists can detect new exoplanets by unusual changes in the speed of a star or its brightness.
Also, stars play an important role in the study of galaxies, especially ours, because they “record” all the stages of its formation. By examining various parameters of a large number of stars, scientists map the galaxy and get a glimpse into its history. This information also helps to understand how other types of galaxies formed, which, in turn, is necessary for understanding how the Universe evolved.
At the end of 2013, the Gaia Optical Space Telescope was launched. His observation program was designed for five years, until 2019, but he is still working. It is possible that his mission will be extended until 2025. This satellite allows you to determine the exact coordinates, velocities and other physical characteristics of more than a billion stars.
What are stars made of?
A star is a ball of gas, in the central part of which thermonuclear reactions take place. It is thanks to them that a star can shine either powerfully enough or for a long time.
99% of the mass of a star is hydrogen and helium, and the remaining percentage is important “additives” that allow you to determine, for example, when the star was formed.
The fact is that elements heavier than hydrogen and helium were already formed as a result of the life of the first stars. Some of these elements were thrown out – for example, a significant proportion of elements heavier than iron appeared as a result of supernova explosions. The merger of two neutron stars also entails large-scale events with the release of heavy elements.
In fact, all the iron that is on Earth came from the explosion of a white dwarf, a type Ia supernova explosion. Therefore, we can say that even the iron taste of blood is the taste of a white dwarf.
What is the Sun and where does the flare come from?
Of course, the main star for mankind is the Sun, and its study has the most immediate practical significance for us. Until a few decades ago, people were not prepared for very powerful solar flares – just remember the blackout in Quebec in 1989, which was the result of a solar storm.
Flares on the Sun, of course, do not threaten to destroy the Earth, as in the movie “The Omen”, but they may well lead to serious technical disasters. Powerful energy emissions lead to a disturbance of the Earth’s magnetic field, and the currents arising in this case in conducting systems can damage them. Therefore, now they are trying to exclude their impact on power lines, gas pipelines and oil pipelines.
But communication satellites are more difficult to protect. Solar activity also poses a danger to other astronomical instruments, so the same satellites sometimes try to launch when the Sun is calm.
One of the biggest problems with a manned flight to Mars is also that the craft is likely to hit a coronal ejection, a giant cloud of plasma ejected by the Sun during flares. Perhaps it can be solved with additional protection for the apparatus or crew – or it would be more expedient to simply plan the flight for periods of a calm Sun.
The good news is that a powerful outbreak cannot happen all of a sudden. The Sun has an eleven-year period of activity, and if somewhere in the foreseeable future there is a chance of an outbreak dangerous to humanity as a biological species, astronomical observations will allow us to predict this decades before the event.
Children are usually told that in five, six or seven billion years, the Sun will turn into a red giant, and then into a white dwarf, and life on Earth will become impossible. However, this is not true, because the planet will become uninhabitable much earlier.
The power of solar radiation is slowly increasing, this is a trend on a scale of hundreds of millions of years. The climate on Earth is getting hotter due to the influence of the Sun. And if the composition of the earth’s atmosphere remains approximately the same, then due to the increase in solar luminosity, life on the planet will end in a billion years. Considering that few earthlings have plans for such a period, one can not worry about the inevitable prospect for now.
Thanks to the creation of new satellites, ground-based telescopes, including neutrino ones, in the foreseeable future, it may be possible to understand the physics of the Sun in great detail. This is also important for predicting the evolution of the earth’s climate.
From the stars to the sun and back
Due to the detailed study of the Sun with the help of neutrino detectors, we now know for sure that thermonuclear reactions occur in the center of stars. Instruments register particles emitted in the bowels of the Sun a few minutes after their formation. Even at speeds close to the speed of light, particles take more than eight minutes to travel from the center of the Sun to the Earth, and today we have learned how to detect neutrinos from all key thermonuclear reactions.
If neutrino detectors made it possible to look into the very center of the Sun, then it is possible to see what is happening between the center and the surface of a star thanks to helioseismology.
Near the solar surface, acoustic waves arise, which propagate into the interior, are reflected and go outside. The visible surface of the Sun oscillates, “breathes”: there are many different waves, and even the same part of the surface can participate in very different oscillations. This can be observed, however, it is not sound that is recorded, but light – thanks to the Doppler effect. The picture that is obtained in this case is amenable to interpretation and modeling, and as a result, we will learn how the speed of sound changes in the depths of the Sun and how the temperature and pressure change there.
Scientists use the knowledge gained about the Sun to study other stars. Distant luminaries may have a different mass, chemical composition, magnetic fields or rotation speed may change, but the essence remains the same. Thus, without even looking into the depths of other stars, we can be sure that they are arranged in the same way as the Sun.