Like in Star Wars: is life possible on a planet with two suns?

During detailed observations as part of the WASP planet search program, European astronomers discovered a new brown dwarf while transiting its star. The newly discovered object, cataloged as WASP-128b, has one significant feature: its tidal interactions with the star are constantly changing. The discovery is detailed in a paper published July 19 on arXiv.org.

Brown dwarfs are considered an intermediate stage between planets and stars. Astronomers generally agree that they are subelemental objects, occupying a mass range from 13 to 80 Jupiter masses. To date, most brown dwarfs discovered are alone in space. However, some brown dwarfs do have orbital stars, and, remarkably, 16 percent of these stars have companions more massive than Jupiter, but only 1 percent of these can be classified as brown dwarfs.

Additionally, only a few brown dwarfs were found to orbit G-type stars. Such objects in G-dwarf systems are thought to undergo rapid orbital decay due to subtle tidal dissipation. Expanding the list of known brown dwarfs in such systems could help study different models of evolution.

Recently, a team of astronomers led by Vedad Hodzic from the University of Birmingham, USA, discovered a new brown dwarf. The transit signal in the light curve of the star WASP-128 was identified using the 0.6 m TRAPPIST robotic telescope and the 1.2 m Euler telescope located at ESO's La Silla Observatory in Chile. Subsequent spectroscopic observations of this star confirmed that the signal was caused by a massive circumstellar satellite orbiting its host.

“We report the discovery of WASP-128b, a new transiting brown dwarf discovered by the WASP survey, in close orbit G0V, where the measured rotation rate of the star system allows it to be characterized as a tidally dynamic system, suggesting strong tidal couplings between the pair “,” the researchers write in their article.

WASP-128b is about the size of Jupiter (0.94 Jupiter radii), but 37.5 times larger than our solar system's largest planet. It causes its parent star to orbit around it and make a complete revolution every 2.2 days.

Moreover, the researchers discovered that WASP-128b is gradually expanding and, according to calculations, it has about 267 million years left to live.

Astronomers noted that this value is similar to what is present in some massive “hot Jupiter” exoplanets in short orbits.

Moreover, the host star is located approximately 1375 light years from Earth and is 16 percent larger and more massive than the Sun. It has a constant temperature of 5950K, an estimated age of about 2.3 billion years, and a rotation period of about 2.93 days. As the paper notes, this rotation rate indicates tidal spin-up that occurs due to its massive companion.

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In the fifth edition of his book "" Universe, life and mind’’:
""In other words, if we take into account sufficiently small values ​​of the ratioM2/M1, then it turns out that Almost all solar-type stars are either multiples or surrounded by a family of planets. If we conditionally assume that the largest mass of a planet is equal to 10 -3 masses of the Sun (Jupiter!), then it turns out that ~ 10% of all stars of the Sun type have planetary systems. In our opinion, despite the comparative poverty of the statistical material used, the studies of Abt and Levy are the best of all existing justifications for the multiplicity of planetary systems for solar-type stars.""

In other words, in those days it was believed that the system could consist of either several stars or one star with planets. Modern research has shown that this assumption is wrong - systems of several stars can also have planets. Therefore, in this part I will briefly describe the discoveries in this area.

There are two types of such planetary systems. The first type is when planets orbit each star in the system. For clarity, this can be demonstrated in the following diagram:

LetterP the planet is indicated by lettersA AndB individual stars of a stellar binary. .

An example of such a system is given at the very beginning, like a scene from a science fiction film. It shows the planet (where dramatic events unfold with incomparable Vin Diesel), which is located in a triple star system, which also includes a close pair of stars. Periodically, the planet experiences prolonged eclipses caused by giant planets with rings orbiting in orbits with shorter and longer periods than the habitable planet where the main events in the film take place.

Planetary system diagram from the world Riddick.

Already the first discoveries of exoplanets showed the widespread distribution of such systems. The most notable of these was a planetary system around a star, suspected back in 1988. The latest study from 2011 gives the following system parameters (in error brackets):
The period of the planetary system is 903.3(1.5) days. Orbital eccentricity 0.049(0.034). Minimum possible mass (from the radial velocity method) 1.85(0.16) mass Jupiter. Maximum possible mass (from astrometry Hipparchus) 28 mass Jupiter. Orbital semimajor axis 2.05(0.06) astronomical units.
The orbital period of the stellar binary is 67(1.4) years, eccentricity 0.41, mass of the main star (around which the planet was found) 1.4(0.12) mass Sun, the mass of the second star is 0.41(0.02) mass Sun.
The compactness of this system can be schematically depicted in the following diagram (scale preserved):

Diagram of known partners in the system. Taken from here.

Along with the very low eccentricity of the planetary orbit compared to the orbit of the second star, many pay attention to the similarity of this system to the closest stellar binary to us - Alpha Centauri(in which a planetary candidate was also recently found). U Alpha Centauri double parameters are: semi-major axis 23.4 astronomical units, orbital eccentricity 0.52, orbital period 79.4 years, stellar masses 1.1 and 0.93 masses Sun.

Generally speaking, about fifty such systems have now been discovered, mostly radial velocity method. Due to the fact that it is difficult for spectrographs to measure the radial velocities of stars separately in stellar binaries (this method is usually used to search for planets in stars separated by more 2 arcseconds), planetary systems are predominantly discovered in wide binaries with distances between stars of hundreds and thousands astronomical units.

Except radial velocity method, searches have recently become effective transits such planets. For example, a telescope Kepler It was possible to find the first planetary systems in which planets revolve around each star in a binary star system. At the star (or Kepler-132) three transiting planets were discovered with periods of 6.18, 6.42 and 18.0 days. Theoretical calculations have shown that such a planetary system cannot be stable if all three planets orbit the same star. Detailed photography of this star solved the mystery:

The measured angular distance between the stars is 0.9'' arcseconds, which corresponds to a distance between them of 450 astronomical units. In addition, the spectra of individual stars showed that the stars have very close radial velocities, which is additional evidence of their physical connection. So far, astronomers have not been able to establish which star is orbited by two transiting planets with periods of about 6 and 18 days, and which star is orbited by only one planet with a period of about 6 days. The second such system is Kepler-296 (KOI-1422). 5 transiting planets were found in it and similarly theoretical calculations say that this system cannot be stable.

Now let's move on to the second type of planetary systems double stars . It consists of planets that orbit several stars at once. It can be depicted schematically like this:

LetterP the planet is indicated by lettersA AndB The individual stars of the stellar binary are indicated. .

Historically, the first such systems were discovered in eclipsing binaries (systems in which stars eclipse each other in relation to an earthly observer). By observing such systems for many decades, it is possible to accurately measure the periodicity of these eclipses. If an outer planet or planets are also orbiting in the system, then its gravity will cause disturbances to the periodicity of stellar eclipses. The first such system was published in 2008 near the star. Around this close system, consisting of a red dwarf and a white subdwarf (eclipsing each other every 3 hours), evidence of two more planets has been found. Their calculated orbital periods were 9 and 16 years, and their masses were 8 and 19 masses Jupiter.

Artistic representation of the system. .

Then later several more similar systems were published. Stellar binary eclipse timing method has low sensitivity and detects systems of massive planets with long orbital periods. Fortunately, in recent years the space telescope Kepler It was possible to discover several more compact systems of this type. Thanks to the high accuracy of measuring the brightness of stars and the long duration of continuous observations, he was able to discover several systems in which eclipses occur (in relation to the earthly observer) caused simultaneously by both stars and planets.

Systems consisting of transiting stars and planets found by the telescope Kepler. The table shows the periods and eccentricities of stellar and planetary orbits. The last column indicates the ratio of the periods of revolution of the planetary orbit to the instability zone, in which planets cannot have stable orbits. The sizes of the planets in these systems are several radii of the planet Earth. .

As follows from the table, even a large eccentricity of the stellar orbit (as in Kepler-34) does not guarantee the same for a nearby planetary orbit in the system (the planetary orbit has an almost circular orbit). The ratio of the orbital periods of planets and stars even reaches just 1 to 6 or 1 to 7 ( Kepler-35 And Kepler-413).

A preliminary study of these finds allows us to estimate that the occurrence of planets (larger than 6 radii Earth and with an orbital period of up to 300 days) for such close stars is 4%-28% in the case of coplanar orbits (the orbits of planets and stars are close to the same plane). If the orbits are located chaotically, then the occurrence can even reach 47%. In either scenario, these preliminary estimates exceed the occurrence estimates for similar planets around single stars.

In conclusion, it remains to be noted that recent research increasingly proves that the formation of planets in systems of several stars is no less efficient than in single stars. This is also supported by the discovery of protoplanetary disks in double stars.

Image of dust disks orbiting each star in a young star systemSR24 . On the left is an image of a telescope Subaru, on the right is a theoretical interpretation of observations. .

Researchers from Princeton and the California Institute of Technology used a computer model to place an Earth-like planet in the orbit of the binary star Kepler-35(AB). It turned out that the conditions on such a planet could be suitable for the emergence and maintenance of life. Even though such an “Earth” would be subject to the gravitational pull of both stars and would move along a bizarre, curved orbit.

Unfortunately, a potentially habitable planet, in the sky of which two suns shine, like on Tatooine from the Star Wars saga, exists only in a computer. In reality, the Kepler-35(AB) system observes a planet eight times larger than Earth, which completes an orbit around two stars in just 131.5 days.

According to the researchers, the work still yielded an important result. “This means that binary star systems like the one we looked at are perfectly suited for habitable planets, despite significant differences in the amount of sunlight that hypothetical planets in such a system would receive,” explained study co-author Max Popp. , research fellow at Princeton University and the Max Planck Institute for Meteorology in Hamburg.

Hot steam atmosphere

Almost simultaneously with the news about Kepler-35(AB), another interesting piece of news came. John Southworth from Keele University in the UK used the ESO/MPG telescope (located in Chile) to determine for the first time the presence of an atmosphere on a planet that may be similar to Earth. Planet GJ 1132b orbits a fairly cool star, the red dwarf GJ 1132. This rocky celestial body is believed to be 20% larger than Earth in diameter and 60% larger in mass. Such planets are called super-Earths. GJ 1132b is "only" 39 light-years from Earth.

In some images taken with radio telescopes, the planet appeared smaller than in others. Scientists examined these images and came to the conclusion that a certain area near the edge of the celestial body is transparent. This area surrounding the planet is its atmosphere. According to scientists, the gas envelope of GJ 1132b consists mostly of methane or water vapor. The presence of steam was of particular interest to scientists because it means the planet has liquid water that evaporates and forms an atmosphere.

Minus three

Planets like GJ 1132b are similar in size and composition to Earth and are located at such a distance from their stars that they could well have the conditions for the origin of life.

Meanwhile, such planets are increasingly disappointing scientists. So, at least three of the seven planets orbiting the red dwarf TRAPPIST-1 may actually turn out to be dead worlds. Scientists from the Hungarian Konkoy Observatory presented to their colleagues a study of the magnetic field of a star. It turned out that the activity of TRAPPIST-1 is capable of provoking frequent and powerful magnetic storms.

A similar geomagnetic storm on Earth in 1859 disabled telegraph systems in Europe and America. The aurora could be seen from the shores of the Caribbean Sea. Considering that the planets in the TRAPPIST-1 system are closer to the star than the Earth is to the Sun, flares of similar intensity occur there much more often. Judging by the available data, in 80 days their number can reach five, and weaker outbreaks occur four times more often than on Earth. Such activity could make the atmosphere of these planets uninhabitable.

Star vs atmosphere

Another disappointment is the study of the planet Proxima b, orbiting the red dwarf Proxima Centauri. It is the closest exoplanet to Earth, located at a distance of just over four light years.

Scientists from the Harvard-Smithsonian Center for Astrophysics presented their models according to which the origin of life on Proxima b could have been prevented not only by flares on the star, but also by a stellar wind that was much stronger and more heterogeneous than the solar wind. As experts recently reported, it was precisely because of the solar wind that Mars could once have lost its atmosphere: a stream of plasma gradually knocked out more than half of the particles of its gaseous shell into space. Something similar probably happened with Proxima b.

However, scientists will soon have the opportunity to learn much more about whether planets in other systems have an atmosphere and what its composition is. The James Webb Space Telescope, developed by NASA and the European and Canadian Space Agencies, is scheduled to launch in 2018. It will allow you to look at the planets in the infrared spectrum and analyze the composition of their atmospheres.

Planets orbiting two or more stars may be a more common phenomenon in the universe than planets with one star, writes www.site.

Star Wars fans fondly remember the moment from the film when a pensive Luke Skywalker looks at the double sunset on his home planet of Tatooine. It turns out that planets with two suns are more common than scientists thought. They recently discovered ten such systems. Scientists even have evidence that such systems are more common than single planet-star systems.

Scientists have long believed that most stars have one or two neighbors. They were tormented by the question of whether these multi-star systems had their own planets. With the launch of the Kepler telescope in 2009, astronomers finally had a tool to search for exoplanets in multi-star systems—distant worlds beyond the solar system.

The newly minted exoplanet Kepler-453b is located 1,400 light years from Earth. It revolves around two suns, i.e. binary star system. Planets in such systems are called "orbiting a double star" for falling under the influence of two stars.

Astronomers discovered Kepler-453b by observing two stars that were orbiting each other. The light coming from each star was a little gray.

“These spots must be formed due to the passage of an object in orbit.”, explains Nader Haghighipour, an astronomer at the University of Hawaii at Manoa. He was one of the authors of a report on the discovery of the planet Kepler-453b in the Astrophysical Journal.

On August 14, the International Astronomical Union, at its General Assembly in Honolulu, Hawaii, published a detailed report on the planet in a binary star system. Scientists have noticed something unusual about a new planet orbiting a double star. Other planets rotate in the same plane as their stars. This means that they pass in front of both stars every time they complete a revolution. But the orbits of the ninth and tenth planets are tilted compared to the orbits of their suns.

"We are very lucky", says Haghighipour. If his team had not looked at the star at the right moment, scientists would have missed the dimming and not identified the planet.

The fact that they found two more planets orbiting a binary star in an unusual orbital plane means that such systems are widespread. Haghighipour added that there must be many similar systems that have not yet been discovered.

After all, if the orbit of a planet occasionally allows it to pass between two stars, the gap in light will not be immediately noticed. The next step for astronomers will be to figure out how to detect such exoplanets. Haghighipour believes this is problematic, but possible. If a planet is large enough, its gravity affects the orbits of its stars. Astronomers intend to look for tiny changes in the light of stars.

"The most famous exoplanets orbit the same star", noted Philippe Theobalt, a planetary scientist at the Paris Observatory in France. He was not involved in the discovery of binary systems. Early research had already found exoplanets in multi-star systems, but scientists were finding double and triple star systems where one planet orbited just one star.

Theobalt argues that the more binary and ternary systems are studied, the more scientists will learn about how they work. According to him, to better understand the laws of the universe, another 50 or 100 systems need to be discovered.

Perhaps right now, on some planet, a young Jedi is admiring a double sunset. This is possible if his home planet is in the Goldilocks zone (a safe habitable zone between the stars). This is the distance from the star that allows water to be in a liquid state without evaporating or freezing. Life on Kepler-453b is unlikely, since this exoplanet is a gas giant. This means that it does not have a hard surface. "But she may have companions", says Haghighipour. Since the satellite is in a safe zone, there may be water there, and with it the conditions for the origin of life.

Planets orbiting two or more stars may be a more common phenomenon in the universe than planets with one star, writes www.site. Star Wars fans fondly remember the moment from the film when a pensive Luke Skywalker looks at the double sunset on his home planet of Tatooine. It turns out that planets with two suns are more common than scientists thought. They recently discovered ten such systems. Scientists even have evidence that such systems are more common than single planet-star systems. Scientists have long believed that most stars have one or two neighbors. They were tormented by the question of whether these multi-star systems have...

Illustration copyright AP Image caption Quantity known to people exoplanets are increasing rapidly

An international team of astronomers has concluded that at least one exoplanet orbits around every star visible in the night sky.

This means that in our galaxy alone there are about 10 billion planets similar in size to Earth.

To observe distant stars, scientists used a phenomenon known as gravitational lensing, which is the bending of a light beam under the influence of the gravity of a massive celestial body.

This gravitational field can act like a magnifying glass and magnify light from more distant stars around which planets may orbit.

A group of astronomers using relatively small telescopes have formed a network to search for new Earth-like planets called Mindstep.

They were trying to detect a rather rare phenomenon when, when observed from Earth, one of the stars appears directly in front of another, more distant star. In this case, the microlensing effect occurs, which makes it possible to find new exoplanets.

As a result, the Mindstep network was able to record 40 such phenomena, and in three cases planets were found orbiting more distant stars.

Although the number of planets found was relatively small, based on these discoveries, the research team was able to calculate the total number of exoplanets.

How the planets "blink"

“In the last 15 years alone, the number of known planets outside the solar system has grown from zero to about 700,” said study co-author Martin Dominic of the University of St. Andrews in Scotland. “But we estimate there are hundreds of billions of them in the Milky Way alone.” planets."

In recent years, most new exoplanets have been discovered using the Kepler telescope, NASA's astronomical satellite designed to search for celestial bodies similar to Earth.

Kepler is trying to find exoplanets by detecting blinking, that is, the change in brightness of a star at the moment when a planet passes between it and the telescope.

This method is more effective when searching for large planets located close to their stars.

The gravitational lensing effect is more difficult to use, but it allows us to find planets of all sizes and at great distances.

The results of the work of a group of astronomers were presented at the 219th meeting of the American Astronomical Society, they were also published in the journal Nature.