However, when Xiaoguang told them about their methods of detecting the earth, Yang Meng was slightly disappointed,

"So it was also detected this way?"

Although the Rutans and the Earthlings seem to be two completely different civilizations,

However, the distance between the two is very similar on the spatial scale of the Milky Way, and the basic physical laws will not change in any way.

Therefore, in the process of detecting planets,

Like humans, planets are generally detected by several commonly used methods.

i.e., radial velocity method, occultation method, astrometric method, direct imaging method, timing method and microgravitational lensing.

However, with Xiaoguang's narration, Yang Meng gradually found some differences,

The earliest method of human discovery of planets was the radial velocity method.

This method uses the velocity generated by the planet as it orbits the star to have a periodic effect on the star's spectrum to determine the existence of the planet.

Although this method is the earliest technology,

However, in the history of human astronomy, the most discovered technology for planets is occultation.

The principle of the so-called occultation is similar to that of a lunar and solar eclipse, that is, the planet occludes the star, causing the star to change its luminosity.

In addition to these two methods, other detection methods have certain limitations in technical conditions.

But after Yang Meng listened to Xiaoguang explain their detection method,

However, it was found that their detection method was a planetary observation method developed by combining microgravitational lensing and direct imaging method.

Direct presentation is easy to understand,

As the name suggests, it is to see the planets directly,

The microgravitational lensing effect is a delicate technique.

In the universe, massive celestial bodies distort the surrounding space,

If you think of the universe as a big pane of glass,

Where the massive object exists, the space will be distorted into a convex lens, magnifying the image behind it.

In the past, humans used this phenomenon to discover a large number of cosmic objects outside the galaxy.

But with micro-lensing, things change.

Microgravitational lensing is magnified by the spatial distortion of a small celestial object to see what is behind it.

The prerequisite for gravitational lensing technology is a massive object, and the greater the mass, the farther you can see and the clearer the magnification.

A yellow dwarf star like the Sun has very limited distortion of the surrounding space.

Therefore, only some weak gravitational lensing effects can be produced.

Extremely sophisticated astronomical instruments are required to make observations.

The Rutans used microgravitational lensing, coupled with optical direct visual method, to detect the situation in the solar system.

"Xiao Yi, according to the method that Xiao Guang said! Is it really possible to see what's going on inside the solar system? ”

"If conditions permit, there is a certain probability that such a detection method can be realized?"

"What kind of conditions?"

"If there had been massive objects in the Rutan star and the solar system at that time, then the technology described by the point of light would have been possible."

Xiao Yi's words made Yang Meng suddenly think of something:

"That is, 560 million years ago, there was to be a very large star between the solar system and Rutan?"

"Yes! However, given the weak gravitational lensing effect of stars, massive stars may need to be close to the observer, or to the side of the observed! ”

"Close! In other words, which solar system or Rutan galaxy needs the star to be close to? ”

"Yes!"

Thinking of the current mass of the nearby stars around the solar system, Yang Meng continued to ask:

"How close do you have to go?"

"According to calculations, if Sirius is used as the base mass unit, the maximum distance cannot exceed 1.372 light years!"

"So close!"

Hearing Xiao Yi's answer, Yang Meng was slightly startled,

You must know that the closest star to the solar system is only 4.3 light-years away.

The distance of 1.37 light years is almost within the range of the sun's gravitational sphere.

Although the Sun is only a yellow dwarf, its gravitational perturbation radius is close to one light-year.

At such a large gravitational perturbation range, a mysterious Oort cloud structure is formed around the outer reaches of the solar system.

And the distance of 1.37 light years, although it is out of the influence of the sun,

But as an unknown massive star,

The resulting gravitational disturbance has been able to interfere with the movement of the Oort cloud within 500 AU to a light-year range of the outer solar system.

And this range, which happens to be the main source of comets in the solar system,

It is conceivable that if a star were so close to the solar system, there would be some instability in the entire solar system.

Thinking of this, Yang Meng continued to ask:

"So, were there any stars that were close to the solar system in the past?"

"Yes!"

"Although it is impossible for humans to speculate what was going on around the solar system 560 million years ago,

However, for stars in millions of years, human beings still have a certain ability to calculate orbits.

In 2013, humanity discovered a red dwarf star called Scholz Star, which is located 22 light-years from the solar system.

"According to orbital simulations, this red dwarf star passed by the solar system 70,000 years ago, when the shortest distance from the solar system was only 0.82 light-years!"

Hearing that it was a red dwarf, Yang Meng shook his head silently:

"A star of this caliber is close to the solar system. The impact is not very big either! ”

But when I think about it, only 70,000 years ago, a star approached the earth,

In the 4.5 billion years of solar system history, we must have encountered a variety of stars.

"By the way, since there have been stars close to the solar system in the past, will there be any stars that will be close to the solar system in the future?"

"Yes! Gliese 710, 63 light-years from Earth, will approach the solar system in 1.4 million years,

At that time, the closest distance between Gliese 710 and the solar system was only 1.1 light-years! ”

"Gliese 710! What grade is that? ”

"Red Dwarf!"

"It's a red dwarf again!"

Although it is a red dwarf again, considering that the red dwarf is suspected to be the most stellar object in the universe,

It's not a surprise that the solar system encounters a large number of red dwarfs as it orbits the Milky Way.

"According to Xiao Yi's analysis, 560 million years ago, the star that the Rutan people used to observe the solar system was definitely not a red dwarf!"

"It's not even a yellow dwarf like the Sun!"

"What kind of star would that be?"

Yang Meng looked at Xiaoguang at this time,

Xiaoguang has already finished telling the planetary exploration technology they discovered the earth, and it is flickering slightly.

As a point of light, it seemed to feel Yang Meng's gaze, and the frequency of the flickering was slightly faster.

"Xiaoguang, what kind of star is that star you use as a gravitational lens?"

"It's a blue-white star, this star flashes at an extremely strange frequency, and we haven't found any remnants of civilization in that star system!"

"It turned out to be a star of this level!"

"What do you mean by flickering strange?"

"The brightness of that star changes very strangely, sometimes bright and sometimes dark, and it is impossible to find a pattern!"