Science

Could a rogue planet destroy Earth?

The vast universe is filled with strange and mysterious phenomena, from quasars and black holes to the Boötes void. A bizarre element in space is the rogue planets, worlds like ours, not tethered to a star, wandering alone and free across the abyss.

Could one of these lonely planets find their way to our own solar system or even collide with Earth?

The red planets, also known as floating planets, are believed to be the result of gravitational interactions early in the formation of solar systems. Or they could be the result of failed star formation.

“Modern theories of planetary system formation suggest that many planets form around young stars when they are in the short-lived phase of their planetary systems’ growth. But many of them are ejected due to gravitational scattering as planetary systems organize themselves over time,” Michael Zemcov, associate professor of physics at the Rochester Institute of Technology, said Newsweek.

As a solar system forms, many pieces of rock of varying sizes and speeds swirl around each other in chaotic orbits. As these bodies pass each other, they change the orbits of other bodies due to their gravity.

“In the typical three-body interactions characteristic of these ejection events, it’s usually the lowest-mass object that gets ejected,” Zemcov said. “So I think a generic prediction of these ‘cleansing’ episodes during the formation of the planetary system is that the heaviest objects – whether rocky or, more likely, ice or gas giants – survive and that the little ones do not survive.”

An illustration with elements from NASA shows a planet colliding with Earth. NASA/Getty

Rogue planets can also come from another source, which is a star that failed to ignite and instead got stuck as a lone gas giant.

“They may form from clouds of gas in space, much the same way stars do, or they may have formed in a disk around a star and then been ejected due to an encounter with another star or an interaction with another planet in the same system,” said Richard Parker, senior lecturer in astrophysics at the University of Sheffield in the UK. Newsweek.

“In the first case, they are likely to be mostly gas giants like Jupiter. In the second case, they could be rocky like Earth,” he said.

Scientists don’t know how many rogue planets are in our galaxy, the Milky Way, because they are extremely difficult to observe.

“[There are] probably many billions or even more, but they are extremely difficult to see,” Zemcov said. “They would emit very little light on their own, mostly at very long wavelengths which are extremely difficult to distinguish from background emission. As a result, our primary means of detecting them is via gravitational microlensing, where we survey a field of stars and then seek light from a background source temporarily amplified by the mass of a rogue planet as it precisely passes between our telescopes and the background star.

He continued: “We found many objects this way, but without further information lens objects are impossible to weigh. So we don’t have a good idea of ​​demographics except in the general sense that things larger ones should be easier to see just because their temporary magnification is brighter and longer.”

Although we don’t have a precise idea of ​​the number of rogue planets, scientists expect it to be significant.

“We expect a very large population,” said Alberto Fairén, a planetary scientist and astrobiologist at Cornell University. Newsweek. “Think this way: the smaller the object in our galaxy, the greater the number of them we expect.”

According to Dorian Abbot, professor of geophysical sciences at the University of Chicago, it’s likely that most rogue planets are terrestrial because there are likely more terrestrial planets in general.

“It is easier to eject them by interaction with a gas giant because they are less massive. But gas giants can also be ejected. Hot Jupiters detected in [around] 1% of systems suggest a major dynamic evolution of these systems since Jupiters must form where it is cold. This dynamic evolution could be associated with the generation of rogue planets,” Abbot said. Newsweek.

With all these invisible planets circling the galaxy, could we enter our solar system or even collide with Earth?

“Assuming there is a rogue planet for every star in the Milky Way, and we assume the solar system will be in a similar region of the galaxy during its lifetime, then I would estimate that the probability that a rogue planet comes into the solar system within the next 1,000 years to have a 1 in a billion chance,” said Garrett Brown, a celestial mechanics and computational physics researcher at the University of Toronto. Newsweek.

An illustration shows two planets colliding. Getty

“Here I define ‘entering the solar system’ to mean that we could see the rogue planet in such a way that when we look at it with a telescope it would look like Neptune or Pluto,” Brown said. “For a rogue planet that were to come at least that close, there would be a 1 in 2,000 chance that it would directly alter Earth’s orbit.”

He continued: “It’s hard to say how likely a collision with Earth would be without more detailed analysis, but it would be much, much less likely. Thus, I would estimate the probability of a rogue planet approaching than Mars or Venus to be 1 in 2 trillion in the next 1,000 years. If there is one heading our way in the next 1,000 years, it would currently be about 0.2 years- light.

Even if a rogue planet approached Earth, the interaction may not even destroy the planet if there was no direct hit.

“It would have to get close enough to Earth to collide with it or, somewhat less unlikely, alter its orbit. If it does collide, it would be at high speed and likely destroy the Earth. , if it is comparable in mass and density to Earth,” said Jacco van Loon, an astrophysicist at Keele University. Newsweek.

“A planet like Jupiter could even swallow Earth. Or Earth could come out the other way if it’s a grazing encounter, but probably without its atmosphere,” he said.

Rather than destroying Earth, a passing rogue planet could even knock our planet out of orbit and become a rogue planet itself.

“I would say the scariest thing, rather than a direct collision, is for Earth to be scattered by a brief encounter by, say, an exo-Neptune passing through, which would move us to a different orbit or maybe being would kick us out of the solar system altogether,” Zemcov said. “Then we would probably all freeze, or maybe cook, in a few weeks. That said, I’m not losing any sleep over such a possibility.”

It is highly unlikely that the interactions of planets already present in our solar system could suddenly propel Earth into the abyss, thanks to our planet’s orbits having had billions of years to balance.

A file image shows the planets of the solar system and their orbits, not to scale.ISTOCK / GETTY IMAGES MORE

“An open and extremely good question is why our own solar system has remained stable for 4.5 billion years,” Zemcov said. “In many ways, this should not be the case. For example, some models of planet formation suggest that Jupiter formed much closer and then somehow migrated towards the place where it is today, likely exchanging momentum with something that was ejected from our solar system.”

He continued, “How we could retain the four rocky planets in the inner solar system in such a scenario is a complete mystery. And then we look around our solar system and see evidence of massive disturbances, for example, Uranus spinning sideways. And it is clear that on astronomical time scales, the details of these [solar systems] are not very strong.”

One possibility is that there were once more planets in our early solar system, but one was ejected as a rogue planet, leaving the solar system never to return.

“What is possible is that our sun kicked a rogue billions of years ago when Jupiter and Saturn traveled from their original inner orbits to their actual positions. This is a scenario we we can’t rule it out but we can’t confirm it either,” Fairén said.

Could a planet be ejected after life has evolved on its surface, or could life evolve after the planet has left its star?

“Another far more interesting feature, to me, of rogue planets [is] the possibility that they could harbor life,” said Lorenzo Iorio, professor of astronomy and astrophysics at Italy’s Ministry of Education, Universities and Research. Newsweek.

Even without a star, life could be maintained under certain conditions. According to the Planetary Society, if a rogue planet had a large moon in close orbit, it could keep the center of the planet warm enough for life to exist in volcanic vent environments.

So while the collision of a rogue planet would likely mean the end of life on Earth, these planets might be able to host their own unique ecosystems.

Do you have a tip on a science story that Newsweek should cover? Have a question about rogue planets? Let us know via science@newsweek.com.

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