Immediately at the three nearest stars, similar to the Sun, there were planetary systems of "super-lands" and "Jupiters". The brightest of them is easy to see with the naked eye in the constellation Virgo, it is only 30 light years away
Over the past 15 years, alien planets are getting closer and closer to the solar system. The first planet orbiting a normal star was discovered in 1994, 50 light years away. The mass of the object, which was unofficially nicknamed Bellerophon, is 150 times the mass of the Earth, and it revolves around the barely distinguishable star 51 (read as "fifty-first") Pegasus with the naked eye. Hence, in fact, the name.
400 planets - large and different
Search for extrasolar planets
Exoplanets, that is, planets around stars other than the Sun, astronomers seek in five main ways.
Firstly, you can just see - however, so far it has been possible only for large and young planets that have not cooled down after birth and glow with their own light.
The second and most productive method for today is the radial velocity method, in which planets are searched for by the fluctuations in the speed of the star due to attraction from the planet.
The third method, which many scientists consider one of the most promising, is the transit method. In this case, scientists are closely monitoring the brightness of the star and try to find periodic "winks" associated with the passage of the planet across the disk of the star. The method of searching for additional planets in the already found planetary system by perturbations at the moments of these partial eclipses due to the attraction of other planets of the system is also adjacent to this.
The fourth method is the method of gravitational microlensing, associated with a change in the brightness of distant background stars when a planet passes next to them and bends the rays of light from a distant object by its attraction. Planetary gravity on its own is usually not enough to fix a signal, but when paired with its star, it turns out to be quite noticeable. The planet of minimum mass has been discovered by this method.
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The fifth method is astrometric, associated with a barely noticeable displacement of a star in the sky due to the attraction of planets. In early 2009, the discovery of the first planet by this method was reported, but this work was later called into question.
Bellerophon was followed by hundreds of other planets - now close, now distant, more often large and less often small, in most cases hot, infrequently cold and very rarely - warm enough, but not too hot for life. Now their number has already exceeded four hundred, and scientists know at least five ways to search for extrasolar planets. However, with a few exceptions, which can be counted on the fingers of one hand, we have not seen these planets themselves and made all the conclusions about their characteristics when studying the light of their native stars.
Most of the extrasolar planets found are giants like our Jupiter for the simple reason that these are the planets that are easiest to find. Whichever method you use in your search, a large and massive companion will more strongly influence the movement and light of the star. For the same reason, most of these planets are hot: the influence of a planet on a star is stronger the closer it is to it, and near the planet they get very hot.
Finally, a significant number of stars around which planets have been found are dwarf stars, dim red stars several times weaker than the sun. Again, for the reason that, all other things being equal, the influence of the planet on a small star will be stronger than on a large one.
Hot virgin threesome
The more interesting is the search results of several independent groups at once, published the previous evening. The brightest of them, of course, was the work of a group of astronomers from Australia, Great Britain and the United States, who found a full-fledged planetary system around the bright star 61 Virgo, located only 28 light years from Earth. An article describing it should be published soon in the pages of the Astrophysical Journal, but in the meantime is available in the Archive of Electronic Preprints at Cornell University.
61 Virgo is actually a twin of the Sun; it is only 5% lighter than our star. Three satellites of planetary masses revolve around this star, which can be seen with the naked eye. The mass of one of them is only 5 Earth masses, the second is 18 Earth masses, the third is 24 times more massive than our planet. They orbit around their star in slightly elongated orbits in 4, 38 and 124 days, respectively. If you put them inside the solar system, two of these orbits will be inside the orbit of Mercury, and the third, the outermost, will almost reach the orbit of Venus.
Of course, with such proximity to its luminary, none of these bodies can be called very attractive for life. On the innermost planet, the equilibrium temperature is about 900 degrees Celsius, on the second - 400, on the third - 150; all, of course, with a plus sign.
Deuce on Libra
The second system, a description of which should appear on the pages of the Monthly Notices of the Royal Astronomical Society, revolves around the star HD 134987, aka 23 Libra. It is also a star similar to the Sun, but it is inaccessible to the naked eye, it can only be seen through binoculars. The planetary system is located at a distance of about 100 light years from Earth.
One planet, with an orbital period of about 258 days, has been known here for about ten years. However, understanding the data on the change in the observed speed of the star, scientists found a signal from another object circling in orbit with a period of nearly 14 years. The masses of the objects are 0.8 and 1.6 masses of Jupiter, while the period of the outer (slow) planet is close to the period of the real Jupiter, which rotates in our own planetary family.
Astronomers think this is a good sign - it looks like we are slowly learning to find systems similar to ours. Previously, the sensitivity of astronomical instruments was lacking for this. By the way, conditions on the outer planet may even be suitable for life - if it has satellites; they consider Jupiter's moon Europa with its subglacial ocean a place with the potential to find life.
Whale hybrid
A third system, also prepared for publication in the Astrophysical Journal, also surrounds a Sun-like star, HD 1461, about 75 light-years away in the constellation Cetus, only slightly larger than our star. Its brilliance is also insufficient to see it with the naked eye, but with binoculars, having coordinates, it is not difficult to find it.
Here we are dealing with a system that is similar to both systems described above at the same time. The innermost planet is also a "super-Earth", like that of 61 Virgo, with a mass of about 7.4 Earth masses and a period of only 5.77 days. The conditions on it, despite the name, are also far from terrestrial - the temperature here is under 1000 degrees Celsius on average and even higher on the daytime side.
But the other two planets have a period of 1.5 years and 14 years - about the same as Mars and Jupiter. True, the mass of "Mars" is almost 30 times that of the Earth, and not 10 times less than that of real Mars. But "Jupiter" from the constellation Cetus is 4 times lighter than our Jupiter, and the conditions on its satellites - if they are there - are almost the same as on the satellites of the largest planet in the solar system.
Lower estimates
The Doppler effect is a
change in the frequency of visible light (or any other waveform) from an object that approaches or moves away from the observer. The frequency of the light of the approaching source increases, the frequency of the receding source decreases.
The frequency shift depends (if we do not take into account the effects of the theory of relativity) only on one component of the relative velocity of the source and the observer - along the straight line connecting them. This component is called the radial velocity. To all these discoveries, however, one must add one "but". All the given mass estimates are the lower bounds of the true value. All these planets were discovered by the method of radial velocities, that is, by periodic changes in the speed of a star due to the attraction of the planets circling around it. This method allows you to estimate only the projection of the true speed on the line of sight, and it is almost always less than the full speed. So the value of mass is probably a little underestimated.
The only case when the line-of-sight velocity coincides with the full one is when the plane of the planet's orbit lies exactly along the line of sight. But in this case, the planet should be regularly projected onto the star's disk, slightly eclipsing its brightness for several hours. So far, the magnitude data for 61 Virgo, 23 Libra, and HD 1461 is not enough to confidently record these eclipses.
But how great it would be! After all, such an eclipse allows you to calculate the real geometric size of the planet, which, together with the mass from Doppler measurements, gives its density. And according to these data, scientists can already build a physical model of a celestial body. According to rumors, scientists will soon report on exactly such measurements - however, for another object. We will wait for news of new additions to the exoplanet family.