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Hundreds of exoplanets with two suns discovered

Until recently, in search of inhabited exoplanets, binary star systems were completely undeservedly ignored. Exoplanets with two suns have long become familiar places where the events of science fiction novels and films are unfolding.

One of the most striking and well-known examples of this is the desert planet Tatooine, the birthplace of Anakin and Luke Skywalker in the famous Star Wars movie saga. But only in 2011, NASA scientists using the Kepler space telescope were able to provide clear evidence that such exoplanets that revolve around two stars at once really exist. The planet discovered then was called Kepler-16b.

Despite the impressive discovery, scientists continued to believe that such planetary systems are extremely rare due to the complex attraction of two suns at once. But this opinion turned out to be completely wrong, writes astrophysicist Paul M. Sutter in an article for Space.com. This was revealed as a result of a new analysis of millions of stars and the discovery of exoplanets that have been recorded and cataloged by the ESA space telescope since 2013.

In fact, there are only two scenarios in which planets cope with the complex gravitational forces of two stars. If the stars are located very far apart, the planet can rotate around one star – then the other will be visible from the surface of the planet as a brightly shining star in the sky. In another case, both stars are close to each other – then the planet rotates at a safe distance around its double sun, as if it were just one celestial body.
These seemingly unbelievable stellar constellations are likely to occur much more often than might be expected.

Researchers have discovered during their targeted search already 300 exoplanets that could “boast” of double suns. Until now, astronomical science has actually ignored binary stars to search for (inhabited) exoplanets, because scientists considered their occurrence extremely unlikely in principle. In the case of discovered 300 planets, it is most likely a question of constellations, in which binary stars were incorrectly interpreted by the telescope as single stars.

Sutter speaks of decades of scientific confusion and uncertainty: “Since we did not often pay attention to the search for planets in binary solar systems, we had little chance of finding them. We didn’t look for anything like that, therefore we didn’t find it. The researcher believes that the realization that such double suns are very common should definitely be considered when searching for new exoplanets.

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Space

ESPRESSO spectrograph confirms the existence of an earth-like planet near Proxima Centauri

The surface of Proxima b through the eyes of the artist ESO / M. Kornmesser

The ESPRESSO spectrograph confirmed the existence of the earth-like exoplanet Proxima b in the star closest to the Sun. Additional observations made by the tool made it possible to clarify its mass, as well as register a second signal, which theoretically can be explained by the presence of another planet. Accepted for publication at Astronomy & Astrophysics, the preprint is available at arXiv.org.

In 2016, astronomers reported the discovery of the planet at the red dwarf Proxima Centauri, the closest star to Earth, located about 4.2 light-years from Earth. The celestial body revolves around the star with a period of 11.2 days and is in the habitable zone – this means that the conditions on its surface allow the existence of liquid water. 

The discovery of Proxima b was one of the most important milestones in exoplanetary astronomy in recent years, but the limited accuracy of the available measurements of radial velocity and the complexity of the simulation required confirmation of the existence of an earth-like planet.

An international group of astronomers used the new-generation spectrograph ESPRESSO, which is part of the VLT complex, to measure the radial velocity of a star with an accuracy of 30 centimeters per second. The data obtained were three times more accurate than the data of the HARPS spectrograph, an instrument of the same type, but of the previous generation, with the help of which the discovery was made. Combining ESPRESSO observations with past measurements showed that the mass of Proxima b is not less than 1.17 earth masses, which is less than the previous estimate of 1.27 earth masses.

In addition, scientists recorded an additional signal repeating with a period of 5.5 days, which so far they have not been able to explain. Hypothetically, it can come from the second planet: if the assumption is true, then its minimum mass is less than a third of the earth, and it is located at a distance of 0.03 astronomical units from Proxima Centauri (one astronomical unit is equal to the average distance from the Earth to the Sun).

In the past, researchers suspected the existence of another planet in the system – this time the super-earth, on which the year lasts about five years. It is five and a half times more massive than the Earth and may have rings similar to the rings of Saturn, but this discovery has not yet been confirmed.

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It’s time to worry. Planets switched to retrograde motion

© NASA / Tunc Tezel

In May, Venus, Saturn and Jupiter become retrograde – they change the direction of motion in the celestial sphere. Previously, it was considered a bad omen. In fact, in the solar system there is only one real retrograde – Venus. But the discovery of retrograde exoplanets was a complete surprise.

Copernicus explained everything

Even in ancient times, people noticed that planets moving in the heavens sometimes behave strangely, loop. Most of the year they follow from west to east (if they are farther from the Sun than the Earth) and suddenly turn around, back down. The moment when this happens is called standing.In 1514, Nicolaus Copernicus proved that the Earth is not the center of the universe, but together with other planets revolves around the Sun. 

Each celestial body has its own orbit, and the retrograde movement that is visible to us is the result of their superposition. For example, Mars approaches the Earth every two years as closely as possible and, overtaking it, draws an s-shaped loop in the sky.

© NASA / Tunc Tezel

The path of Mars in the celestial sphere in the period from July 2005 to February 2006. It goes from west to east and at the moment of approaching the Earth makes a loop. For a couple of months his movement seems retrograde to us.

Venus and Uranus versus all

All planets in relation to the Earth for a short time move backward, but this is only an appearance. Real retrogrades do not physically rotate like the rest. In the solar system, it is only Venus. If we were above the north pole of Venus, we would see that it rotates clockwise around its axis. Earth and other planets are against.It is believed that planets form together with a star from one protoplanetary disk. In theory, their orbits should lie in the same plane, and the directions of rotation in the orbit and around the axis should coincide. Why Venus is not like this is not yet clear. 

Although scientists note its strong similarity with the Earth – these planets are even called twins. One of the explanations is that the processes occurring in the bowels and atmosphere have slowed the rotation of Venus so much that it stopped at some point, and then began to spin in another direction.

The distant ice giant Uranus also looks like a retrograde. It lies on its side relative to the plane of its orbit, and pecks down the north pole, which makes Uranus seem to rotate clockwise. But if you put it normally, it will become normal. Scientists believe that billions of years ago, Uranus collided with a large cosmic body and turned over in space. Another hypothesis is that in the past the planet had a massive system of rings that caused resonance, rocked it and deployed.

General rules apply to planetary moons. For example, the Earth rotates counterclockwise, and so does the Moon around the Earth. But one of the 13 moons of Neptune – Triton – is “against the coat.” So, scientists conclude, Triton did not belong to Neptune, was an independent small body, until Neptune captured it from the Kuiper belt. By the way, Pluto, similar in composition to Triton, is also retrograde. In part, this contributed to its transfer to the category of dwarf planets.

© Illustration by RIA Novosti. NASA / JPLRetrograde motion of Triton. This is the only major satellite in the solar system that moves in orbit against the course of its planet.

Anomalies of hot jupiters

This is what our system is completely devoid of – planets that would move in orbits against the rotation of the Sun. For a long time, astronomers believed that this should be everywhere. But in 2009, they discovered the first exoplanet with a retrograde orbit at the star WASP-17 in the constellation Scorpio.WASP-17 b is the largest and least dense exoplanet known. Such gas giants are called hot jupiters.

Its retrograde intrigues scientists. Smadar Naoz from the Center for Interdisciplinary Research in Astrophysics at Northwestern University ( USA ) proposed a possible mechanism: the mutual influence of giant planets during migration closer to a star or a brown dwarf. But its implementation requires the coincidence of too many conditions, and this is unlikely. Nevertheless, the astrophysicist put forward a bold hypothesis that such retrograde jupiters are not uncommon – a quarter among those observed. However, the existence of the hot Jupiters themselves is still waiting for its explanation.

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A space object that changes the concept of the Universe is discovered: An unthinkable ancient galaxy

Photo: NRAO / AUI / NSF / S. Dagnello

Scientists at the Institute for Astronomy of the Max Planck Society in the UK announced the discovery of the oldest massive galaxy DLA0817g, which arose just 1.5 billion years after the Big Bang. It has a disk, which can change astronomers’ ideas about the mechanisms of galaxy formation. An article by astronomers is published in the journal Nature.

Researchers discovered the galaxy using the ALMA (Atacama Large Millimeter Array) radio telescope complex. This ancient object was named Wolf Disc – in honor of the astronomer Arthur Wolf. It has become the farthest spinning-disk galaxy of all detected so far, and its cosmological redshift is 4.26. 

The light from it flew 12.2 billion years, but due to the expansion of the Universe, the galaxy is currently at a distance of 24.4 billion light years. The rotation occurs at a speed of 272 kilometers per second, which is comparable to the rotation speed of the Milky Way.

According to modern models, massive galaxies are formed from the mergers of smaller mass galaxies and clusters of hot gas. These collisions prevent the formation of disks characteristic of the Universe of this age. 

Therefore, the existence of the Wolf Disc will force astronomers to reconsider the mechanisms of the appearance of such space objects. DLA0817g probably accumulated cold gas, but the question of how he managed to maintain a stable disk with such a large mass remains open.

Scientists also found that the star formation rate in the Wolf Disk is ten times higher than the star formation rate in the Milky Way. According to astronomers, he was one of the most productive galaxies in the early Universe.

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