Earth's transit zone: the best place to search for aliens?

Earth's transit zone: the best place to search for aliens?

How the hell can we find, much less communicate with extraterrestrial intelligence, when there are billions of potentially friendly planets to explore?

Some researchers track broadcasts from nearby stars where the signals are very strong. Others focus on star clusters, following the law of averages, according to which, you can have many potential targets in a narrow visual field. However, a new study allows you to change tactics. It proposes to search for aliens who live in the equivalent solar transit zone of the Earth.

Most of the planets orbiting their stars (an event called “transit”) are seen in a relatively short period of time — perhaps every few dozen days or even shorter. This is partly because we are limited in time by the telescope and can only observe the star target for as long as the treacherous darkening of the light hiding the planet allows.

Someone looks at the Earth from afar, but they must show more patience. The fact is that the Earth crosses the face of the Sun every 365 days, suggesting a narrow field of view of 0.262 degrees when projecting the universe as a whole. In other words, a smart alien in a distant world should be in the right place to see the transit of our planet in relation to the sun. “This research began during a coffee conversation with my former classmate Ph.D. Dimitris Mislis when we were at the Hamburg observatory in Germany,” Rene Heller from the Max Planck Institute for Solar System Research in Göttingen, Germany, e-mailed. .

“It must have been at that time, in 2009, that Dimitris and I both worked on exoplanet transits. He studied the actually observed passage of the TrES-2b exoplanet, from which at that time it was expected to show some strange variants of transit synchronization. ”

Earth's transit zone: the best place to search for aliens?

In this image, taken by the Voyager-1 spacecraft, you can see the Earth, which is represented here as a dim dot to the right. The image was taken from a distance of 6 billion miles.

As part of the discussion, both began speculating on what would be seen by those who are far from the solar system if they look at the planets in the solar system following in transit. They realized that the Earth is visible only from a small area of ​​the sky. Heller made some notes, but hid them away. He stumbled across the notes again, doing a post-doctoral research at the Institute of the Origins of Maxmaster University in Canada. With the support of his manager Ralph Pudritz, Heller began exploring the topic in more depth.

Pale blue dot: our house, as seen from the Voyager 1 spacecraft on February 14, 1990, when the probe departed from Earth at a distance of 6 billion miles. How could aliens in different star systems detect our planet? Heller and Pudritz built a study in which they implemented a “target list” of potential stars close to our own sun (including K and G-type stars). These goals, defined with the help of the well-known Hipparch's catalog, lie in the Earth transit zone (ETZ) and are located within 3260 light years from us. The researchers then created a model of the galactic disk to determine the number of potential stars they could explore. Their estimates show that there are approximately 10 thousand potential K and G dwarf stars that fall into ETZ. But how to find them all?

Fortunately, there is a star review mission right now. It is called Gaia, and the mission of the European Space Agency was to scan the entire sky, starting in 2014. Heller said the first data release will take place this summer.

“Among these stars will be millions of G-type stars like the Sun,” said Heller. - Thus, over the next few years, we will find more and more stars like the Sun in the vicinity of our Galaxy, many of which will be located in ETZ.

For researchers of exoplanets, it is customary to search for planets similar to Earth around M-dwarfs that are faster and smaller than stars, like our Sun. It is much easier to see planets like Earth, as these stars are not so bright. Heller notes that there are about 10,000 M-dwarfs found very close to our Sun (within 326 light-years). This is not so surprising, considering that about 75% of the stars near us are M-dwarfs, but to search for them you need another telescope capable of viewing in the infrared. He suggested using the Sloan Digital Sky Survey, which, using a 2.5-meter telescope in New Mexico, has already managed to find more than 7,000 dwarfs. Heller added that at least there are several hundred M-dwarfs visible on ETZ, but there is no exact count yet.

Heller said there is no reason to drag out the time with detecting sources of radio signals from intelligent civilizations in the ETZ. According to him, radio telescopes that are already available could do this search.

“This can be done now,” he said, “and, given the very limited number of stars like the sun ETZ (limited here means 100000), the full ETZ Network can be implemented throughout a person’s life. In other words, we could very soon find out whether others had found us with the help of our transits, and then made contact. ”

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