Astronomers usually search for “traces” of extraterrestrial life on planets located in the star’s “habitable zone”. “Liveable Zone” refers to a certain distance around the star, within which the surface temperature of the planet is moderate, water can be present in liquid form on the surface of the planet, life is bred.
This image compares the different characteristics of G-shaped, M-red dwarfs and K-shaped dwarfs in the Milky Way. Photo: NASA website
But after 30 years of stellar research, a new view has surfaced, according to NASA’s website. The view is that there is a “golden phoenix star” in the universe (Golden Phoenix girl is the traditional American fairy tale character, she likes not hot and cold porridge, not soft or hard chair and all the “just good” things, so, Americans often use “golden phoenix girl” to describe “just good.” ), its surface is neither too hot nor too cold, and most importantly, it has planets that are environmentally friendly, “gentle” and suitable for life. These “golden phoenix stars” are actually the best places to search for life.
There are three main types of stars in the Milky Way.
Given that the sun has fed life on Earth for nearly 4 billion years, the conventional wisdom is that stars like the sun are the main candidates for the search for other potentially habitable planets. But Edward Keenan of Villanova University in Pennsylvania believes that the K-type dwarf, with a slightly lower temperature and brightness than the sun, is the real “promised land” and the most suitable “liveable star” for advanced life.
The Milky Way is dominated by three types of stars: G-type sunstars; K-type dwarfs with a mass smaller than the sun and a lower temperature than the sun; and a Type M-red dwarf with a lower temperature than a K-type dwarf. The Milky Way has the largest number of stars, with about 73 per cent, with the smallest type G at about 6 per cent, and the K-type dwarf star at about 13 per cent.
“Of the three stars, the K-type dwarfs occupy the ‘best position’ and are somewhere between the rarer, brighter, but shorter-lived G-shaped stars and the more common M-shaped red dwarfs,” Keenan said. K-type dwarfs, especially the high-temperature K-dwarfs, have the best stellar environment. “
K-type dwarfs are relatively “gentle”
Why is the K dwarf the best choice for finding extra-terrestrial life? Keenan explained that the K-type dwarf star is the Milky Way’s “golden phoenix star” and its number, life and radiation level sit “just fine.”
First, the number of K-type dwarfs is three times that of g-types, about 1,000 K-shaped dwarfs within 100 light-years of the sun, and are the main objects of exploration for extra-system life.
In addition, the life span of The K dwarf ranges from 15 billion to 45 billion years. By contrast, the sun has a life span of only 10 billion years, and the sun has now passed through the “first half of life”. Given the relatively rapid rate of solar evolution, the Earth will remain virtually habitable in another billion or 2 billion years. Because in about 1 billion years, the Earth will be on the edge of a warmer temperature in the sun’s habitable zone, and its habitable zone will gradually move away as the sun becomes hotter and brighter. Eventually, the Earth will lose its atmosphere and oceans and become extremely dry. At the age of 9 billion, the sun will swell into a red giant star that will engulf the earth.
M-type red dwarfs, despite their small size, are in large numbers and have a longer life span. Unfortunately, we know that they do not seem appropriate to give birth to life. The main reason is that the M-type red dwarf has a lower surface temperature and a relatively narrow livable zone, and the planets located in the habitable zone are very close to the stars, exposed to extremely strong X-rays and ultraviolet radiation, and may be tens of thousands of times the intensity of the Earth’s exposure to the sun. Continuous flares and coronal mass ejections throw large amounts of plasma and high-energy particles, bombarding their planets. As a result, the inner planets of the red dwarf”s”shabited zone will be “baked dry”, losing their atmosphere early in their lives and failing to evolve into a livable planet.
The K-type dwarfs are relatively “gentle” a little, with no active magnetic fields producing strong X-rays and ultraviolet radiation and high-energy bursts, so they erupt at low frequencies and their planets are exposed to much less lethal X-ray radiation.
“Golden Phoenix Plan” draws conclusion
Keenan and his colleague Scott Engel worked on a research project called the Golden Phoenix Project. For the project, the Keenan team used the Hubble Space Telescope, the Chandra X-ray Observatory and the XMM-Newton satellite to observe various types of stars. Based on these observations, they determined the relationship between the age, rotation rate, X-ray-ultraviolet radiation and flare activity of these stars.
They sampled some of the cooler G-shaped stars and K-shaped dwarfs. The Hubble telescope is extremely sensitive to ultraviolet light from hydrogen, and they assessed the radiation from about 20 K-type dwarfs. “The Hubble telescope is currently the only telescope that can make such observations, ” says Mr Keenan. “
Among the K-shaped dwarfs observed are Kepler-442, Tianlun V in cetacean and Tianyuan IV in the constellation Bojiang. The last two stars were the target of the Ozma Project, which began in the 1950s and was the first to attempt to detect radio signals from alien civilizations.
“It’s worth noting that Kepler-442 is important because it has the best ‘Golden Phoenix’ planet, Kepler-442b, which has more than twice the mass of Earth,” Mr Keenan said. “