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Life can evolve on small planets with 3% of Earth’s mass.

Could a tiny planet with weak gravity harbor life?

A team of scientists from Harvard University say they’ve found the smallest possible mass a planet could be before its lack of gravitational forces would cause it to lose its atmosphere and any liquid water.

They found that the smallest possible planet that could maintain those life-enabling properties would be about 2.7 percent of the mass of Earth. That’s a little more than twice the mass of the Moon and roughly half the mass of Mercury.

An exoplanet is said to be in a star’s habitable zone if it’s at the right distance to be able to support liquid water. If it’s too close, it would receive too much radiation from its sun, making it too hot. Too far, and it’d be too cold for liquid water.

Astronomer Constantin Arnscheidt, lead author of the article describing the research, published in Astrophysical Journal in August told the Astrobiology Magazine:

When people think of the inner and outer edges of the habitable zone, they tend to think only spatially, meaning how close the planet is to the star. But in fact, there are many other habitability variables, including the mass (of a planet).

If exoplanets are big enough, the researchers found there’s enough of a greenhouse effect to keep them at the right temperature, regardless of their positions inside the habitable zone. That’s because the atmosphere of these relatively small planets would expand outwards thanks to relatively low gravity, which in turn would cause it to absorb more radiation from its star and thereby stabilize temperatures on its surface.

Interestingly, the research would rule out tiny ice worlds in Jupiter’s orbit — they’d be too small. These icy moons have had scientists excited about the possibility of life thanks to massive underground oceans.

But the research suggests that there could be plenty of other places we haven’t discovered yet that are just the right size.




It’s a good start: TESS orbiting telescope discovers the first habitable world, with oceans

The TESS Space Telescope has discovered a planet on which oceans may exist. In addition, the exoplanet revolves around a quiet star, and this compares favorably with other candidates for the title of the cradle of extraterrestrial life. This is the first, but certainly not the last potentially inhabited world discovered by the TESS Observatory.

The space telescope was launched in 2018. Its task is to search for exoplanets, including those similar to Earth.

TESS has discovered 17 Earth-like planets orbiting 11 stars so far, according to a press release for the new study. All these luminaries are red dwarfs, which are smaller and colder than the Sun.

The TESS team divided almost the entire sky into sectors, each of which is observed for 27 days. However, these areas partially overlap, so some luminaries remain in the field of view of the device for much longer.

The TOI-700 star (aka TIC 150428135) is one of those “lucky ones”. Thanks to this, astronomers have discovered as many as three exoplanets about the size of the Earth.

The first of them (TOI-700b) has a radius almost equal to that of the Earth and revolves around its sun in 10 Earth days. The next planet, TOI-700c, is much larger than its neighbor (2.7 times the Earth’s radius). It makes a complete revolution in 16 days.

However, the most interesting of all is the third exoplanet from the planet TOI-700d. Its radius is 1.1 terrestrial, and its orbital period is 37 terrestrial days. It is this orbit around the cool local sun that makes the TOI-700d “right to life.” 

According to scientists, the planet receives 86% of the heat that goes to the Earth. This means that the temperature on this celestial body allows for the existence of liquid water and, therefore, the biosphere. According to experts, the exoplanet is in the habitable zone.

Planetary system TOI-700. The habitable zone is shown in green. One astronomical unit (AU) is equal to the distance from the Earth to the Sun. Illustration by Rodriguez et al. / Astronomical Journal (2020).

Three scientific articles published in the Astronomical Journal are devoted to the newly discovered world.

The first describes the discovery of this planet using the TESS telescope.

The second publication is devoted to the observation of an exoplanet using the Spitzer space infrared observatory. The telescope received this data in October 2019 and January 2020, shortly before the termination of its mission.

Finally, the authors of the third research paper simulated the possible climate of TOI-700d.

The researchers examined two dozen scenarios that differ from each other in the composition of the planet’s atmosphere, the amount of water on it, and other characteristics. Their conclusion is optimistic: a climate suitable for life is obtained in a fairly wide range of conditions.

It is important that TOI-700, unlike most other red dwarfs, is a calm star, not prone to catastrophic flares. That is, TOI-700d has every chance of preserving the atmosphere and hydrosphere for billions of years.

Of course, not without a fly in the ointment. TOI-700 is more than a hundred light years from Earth. It’s too far away to directly study the atmosphere of a small planet like TOI-700d, even with the future James Webb telescope .

However, the capabilities of astronomical instruments are growing rapidly. Perhaps in a few decades, scientists will carefully study the mysterious exoplanet and (who knows?) will find signs of the existence of life on it.

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Apophis: A dangerous phenomenon was noticed on an asteroid threatening Earth

The asteroid Apophis, potentially dangerous for the Earth, experiences the Yarkovsky effect, as a result of which it gains acceleration and shifts to more and more threatening orbits with a collision with the Earth.

The asteroid Apophis, 325 meters in size, was discovered in 2004. The discovery caused a stir – calculations showed that there is a 2.7 percent probability that Apophis, named after the ancient Egyptian god of evil and destruction, will collide with the Earth in 2029. Then scientists ruled out this threat, calculating that on April 13, 2029, the asteroid will fly at a distance of 37.6 thousand kilometers from the center of the Earth.

The report on the detected displacement was presented at the Planetological Section of the Virtual Meeting of the American Astronomical Society in 2020 by a specialist from the Institute of Astronomy, University of Hawaii, Dave Tholen. According to the speaker and his colleagues, the asteroid Apophis is strongly susceptible to the Yarkovsky effect, which consists in a weak force effect on an object moving in space due to the inhomogeneity of thermal radiation.

All asteroids emit in the form of heat the energy of the sunlight they absorb in order to remain in a state of thermal equilibrium – and as a result of this process, the asteroid’s orbit changes weakly. Until now, it was believed that collisions of the asteroid Apophis during its approach to Earth in 2029 and 2068 are impossible. Taking into account the Yarkovsky effect with respect to a 325-meter potentially dangerous asteroid means that the scenario of its collision with the Earth in 2068 is updated again.

Apophis is the most likely candidate for a collision from the aton asteroids passing near the Earth, was discovered in 2004 and received its own name on July 19, 2005 in honor of the ancient Egyptian god Apop (Apophis) – a huge destroyer snake living in the darkness of the underworld and trying to destroy Sun (Ra).

During its approach to Earth on Friday, April 13, 2029, this asteroid will be visible to the naked eye as it passes within the orbits of Earth’s communications satellites.

One of the discoverers of Apophis, David Jay Tolen, in particular, said:

“We already know that the collision of this cosmic stone with our planet is impossible during the approach of 2029. However, the quality of our new observations with the Subaru telescope was high enough to reveal the acceleration resulting from the Yarkovsky effect on this asteroid.

Calculations have shown that the asteroid is annually displaced from a “purely gravitational” orbit by about 170 meters, and this displacement is enough to return the scenario of a collision with the Earth in 2068 among the probable outcomes .”

There are a number of services on Earth that track the potentially dangerous approaches of our planet with asteroids, but significant in body size, such as Apophis, attract the attention of scientists.

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US professor said that the space expansion of earthlings will lead to the spread of totalitarianism

Political scientist Daniel Dodney believes that the foundation for future space conflicts is being laid on Earth today.

Space exploration is one of the main priorities for humanity in the 21st century. But not everyone agrees that the exit of our civilization beyond the boundaries of the globe will do more good than harm. For example, Daniel Dodney, professor of political science at Johns Hopkins University in the United States, believes that we should not attempt space expansion at all.

Dewdney is confident that the emergence of new habitats for people, in addition to the Earth, will lead to the emergence of interplanetary totalitarian empires. And if mankind somehow manages to master at least a few planets of the solar system, then nuclear weapons will become the “gold standard” in all wars (which, according to the professor, will not stop).

Although many colleagues consider Daniel’s arguments too pessimistic, the political scientist himself generally believes that people should abandon the exploration of outer space and search for a new home. 

“The large-scale expansion of human activity into space <…> must be included in the growing list of catastrophic existential threats to humanity,” Dodni insists.

No matter how gloomy the views of the American political scientist may look, they have certain grounds. So, in 2019, the United States announced the creation of a new type of its Armed Forces – space: they are “designed to protect the interests of the United States in space, deter aggression at long distances and conduct operational and consistent space operations.”

Daniel Dodney / The Brown Daily Herald
Daniel Dodney / The Brown Daily Herald

Other countries followed the American example: France, Canada and Japan announced their intentions to create similar troops. According to Dodnya, all this testifies to laying the foundation for future “near-earth conflicts.” According to his forecasts, space special forces will one day be able to control asteroids and comets to destroy settlements on rival planets or change the climate there, causing total extinction.

At the same time, the political scientist notes that he has nothing against “using space in ways that will benefit the Earth.” However, he doubts that this is possible.

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