Interstellar objects and exoplanet hunting.

“Interstellar object ʻOumuamua sped up as it approached the Sun, shooting past at 196,000 mph (315,431 km/h) and then slowing down as it moved away” (Astronomy, Why aren’t free-floating planets captured when they fly past stars?)

Stars could capture a rogue planet. But that is not as common as many people think. When a planet enters another solar system, it must release its kinetic energy. And rogue planets have a massive amount of kinetic energy. If. That object arrives in the solar system too steeply. its fate would be the star in the middle of the solar system. If. The angle is too shallow. That exoplanet travels straight through the solar system. 

The star could capture a rogue planet if it has the right angle and the right speed. This means that the star should travel behind the planet, following its trajectory. The gravitational brake will slow the planet’s speed. And if that planet arrives in the solar system at the precise right angle. It can start to orbit that star. Things. Like 3/Atlas and other interstellar asteroids. They follow the same rules as larger rogue planets. 

"NASA’s Nancy Grace Roman Space Telescope has successfully powered up its 300-megapixel Wide Field Instrument, a massive infrared camera built to scan huge areas of the sky while preserving Hubble-like detail. Credit: NASA’s Goddard Space Flight Center" (ScitechDaily, NASA’s Roman Telescope Opens Its 300-Megapixel Eye on the Universe)

In reality, we can see only large exoplanets. That. Orbit M-type red dwarfs. 

When we ask whether aliens can see Earth. If. They have similar technology. To. That we have. We can rephrase that question. Can we see an Earth-type planet that orbits its star in the habitable zone? The answer is that a G-spectral-class star is so bright. Its shine. It covers an Earth-type planet. Under its brightness. In planet hunting. Astronomers use methods that benefit from the planet's transit. When. A planet comes between Earth and its own sun. That. Affects the star’s brightness. 

If. The star is small enough. The large exoplanet can affect its trajectory. The wobbling trajectory caused suspicions that Barnard’s Star had exoplanets. Most exoplanets that we know are large. They orbit dim and light stars. And we cannot see Earth-like planets that orbit. Bright stars. The case is similar to Betelgeuse. The brightness of the center star. It covers. The. Dimmer companion under it. Betelgeuse is one of the most well-known stars in the sky. The B-type companion star was confirmed in 31.72026. 

Before astronomers can confirm the existence of the exoplanet. They. Must rule out other possibilities, like changes in the star’s own brightness. Another method astronomers can use is looking for holes in planetary nebulae around stars. Large exoplanets form holes in that nebula. But those nebulae surround only young stars. That method is not suitable for long-distance observations. Things like IR telescopes could see planets through dust and ice. The big problem is that stars also warm dust. 

The surface area of the interplanetary nebula is larger than a planet. And the IR telescopes see that dust. But that dust covers the planet under its IR glow. We can get direct images only from the closest exoplanets. And that requires that they orbit a red dwarf. The reason.  For why. We can see Planets like Proxima B. It is that. They orbit red dwarfs. Those dim stars are dim enough that sensors can measure changes in their brightness. The fact is that. We can’t see a planet that orbits Alpha Centauri or a brighter star. When. A star shines through the exoplanet's atmosphere. That. Allows astronomers. to. make a spectral analysis of the planet’s atmosphere and its chemical fingerprint. This works only with dim stars. That don’t outshine those exoplanets with their brightness. 

https://www.astronomy.com/science/could-aliens-detect-earth-with-our-current-planet-hunting-techniques/

https://www.astronomy.com/science/why-arent-free-floating-planets-captured-when-they-fly-past-stars/

https://www.eso.org/public/news/eso2611/

https://scitechdaily.com/i-jumped-from-my-chair-astronomers-discover-a-hidden-star-orbiting-betelgeuse/

The first exoplanet that JWST found has no atmosphere.

Above: Artist's impression of exoplanet LHS 475 b

Even the perfect size of an exoplanet doesn't guarantee that there are lifeforms. The exoplanet LHS 475 b is 99% of Earth. But the problem is that it doesn't have an atmosphere at all. Or an extremely thin atmosphere. In the last case, the planet captures star wind around it. That means the extremely thin atmosphere could be external. And that is a remarkable thing. The LHS 475 b orbits the red dwarf star in the Octans constellation 41 light years from Earth. 

 Even large rocky planets can be without an atmosphere. And that expands our knowledge of planets. The exoplanet LHS 475 b is the first exoplanet found by the JWST telescope. But that planet is extremely hostile to lifeforms. So even a large size doesn't guarantee that the exoplanet has an atmosphere. 

But the reason for the lost atmosphere is also interesting. The lack of atmosphere can be the reason for the lack of a magnetic field. In that case, the solar wind blows the atmosphere away. And if that thing is true, there is a possibility that the planet is a so-called "zombie world" where is no radioactive material left. 

And that thing means that the LHS 475 b could be a very old planet. There is a possibility that this exoplanet is sometimes born near some other star. And then supernova- or nova eruption pushed it away from its orbiter. Then another star could capture that rogue planet. Those kinds of things are making LHS 475 b very interesting. 

https://astrobiology.com/2023/01/webb-discovers-lhs-475-b-an-earth-sized-rocky-planet.html

https://bigthink.com/starts-with-a-bang/no-atmosphere-jwst-exoplanet/

https://webbtelescope.org/contents/media/images/2023/102/01GNVWTAZKPVD1GNC0HZF52YTB

https://astronomyandtechnology.blogspot.com/

There is found two probably habitable planet's near our solar system.

The research team, which operates in the Canary Islands found two earth-mass planets near our solar system. Those planets are orbiting red dwarf GJ or Gliese 1002 in the habitable zone. And that thing is one of the most remarkable things in astronomy. The distance to that star is 15,8 light years. So that star is almost our neighbor. 

The surface temperature of that "M" spectral class star is about  3,024 K or 2,751 °C. That means it's far colder than the sun. Even if those planets are close to their star, the radiation of that star is weaker than the Sun. 

The habitable planets near red dwarfs are possible. If there is lots of water on the planet clouds are cooling their atmosphere. Same way as the night side of the locked planet is very cold. And monsoon winds that formed because of the differences in temperatures are also decreasing the temperature on the planet. 

Super-Earths and habitable zones. 

The term "super-earth" means a rocky planet that is larger than Earth. But the planet's size doesn't mean its gravitation is stronger than Earth's gravitational field. The elements that are forming planets determine the strength of the gravitation. And there are known exoplanets that size is two times Earth, but their gravitation is just over 0,6 times Earth's. So the planet is lighter than Earth. 

There must also be smaller-than Earth, metal-rich planets than Earth. But their gravitational fields are stronger. If a small planet involves lots of heavy metals, its gravitational field can be stronger than Earth's. 

Also, if the sea covers the entire planet, that can cause a situation. That winds travel around the planet. That thing can cause that friction turns the atmosphere's temperature very high. In the case of water planets, the wind can continue even for millions of years. And in that case, the long-term friction. Even if that is weak can have massive consequences. 

In a strong gravitational field, gravitation turns water to ice. Also, even a thin atmosphere is turning very dense. 

Because gravitation pulls gasses to the planet's surface in an extremely strong gravitational field, and in extreme pressure, even gasses are turning solid. That kind of planet where the atmosphere is in solid form cannot host any lifeforms. But in gravitational ice could theoretically live 2D worms. 

There is planet Gliese- or GJ 436 that hot ice is covering. The gravitation of that planet is so strong, that water cannot vaporize. 

But normally, or in most scenarios. Liquid water and a stable atmosphere are a requirement for lifeforms. And the planet must somehow tie gasses around it. So the planet must have a magnetic field that pushes star wind away from its atmosphere. Or those ionized particles will blow the atmosphere away from the planet. 

If the planet's gravitational field is weak, the atmosphere will turn very huge. But for a stable atmosphere planet must also have a magnetic field. That denies star wind blowing the gas away from the planet. And that means the planet must have a nucleus in liquid form. 

If the planet's gravitational field is strong, it causes the water's boiling temperature is turning higher. And if the planet's gravitational field is weak, it decreases the boiling point. So if the planet's gravitational field is weak, the water turns to vapor or its density decreases. That means water in very weak gravitation is not in the same form as it's on Earth. 

https://scitechdaily.com/two-potentially-habitable-earth-like-planets-discovered-around-a-star-near-the-sun/

https://en.wikipedia.org/wiki/Gliese_436_b

https://en.wikipedia.org/wiki/Gliese_1002

Images: https://scitechdaily.com/two-potentially-habitable-earth-like-planets-discovered-around-a-star-near-the-sun/