exoplanets are celestial bodies that orbit a star other than our Sun. They are very difficult to see directly with telescopes because they are hidden by the glow of the stars they orbit.
Rocky or gaseous, hot or cold, they come in the most diverse formats. Some even possess liquid water, and may hold evidence of the answer to one of humanity’s greatest questions: “Are we alone in the universe?”
The universe is filled with planets, each a new world yet to be explored (Source: Pixabay/flflflflfl)Source: Pixabay
planets are more common objects than you think. Astronomers have already confirmed the existence of more than 4,000 of them, in different stars across the galaxy. At least another thousand await confirmation of their identity.
These worlds are very far away from us. The first two were only found in 1992. And, unlike Earth, they orbit a pulsar, a neutron star with a strong magnetic field.
Are there more planets in the universe?
Before that, their existence was only theoretical. At the beginning of the 20th century, scientists even announced the discovery of a exoplanet orbiting Barnard’s Star, but further analysis showed the hypothesis to be wrong.
In addition to distance, there is another problem that has delayed the discovery of these bodies. It’s just that they don’t have their own light. To identify a planet it is necessary to observe the light that reflects on it, and that end up losing the intensity of the glow in the process.
For many years the existence of exoplanets was only theoretical – evidence was lacking (Source: Pixabay/D_Van_Rensburg)Source: Pixabay
Hence they are overshadowed by their own stars. Even today it is very difficult to observe a exoplanet with a telescope. Only in a few cases was it possible to obtain a direct image of these distant worlds.
When they were still theoretical bodies, astronomers thought that it would be possible to find planets very similar to those of the solar system. Which was not the big surprise when they were faced with a myriad of new possibilities.
With different formations and some almost inexplicable orbits, our neighborhood has been found to be the exception rather than the rule when it comes to planets.
The first discovery, from 1992, surprised with the neutron star. These are super-dense remnants of the cores of ancient and already dead stars, which emit beams of radio wave that reach us.
Amidst such a catastrophic environment, no one thought that a planet would be possible, and yet they were discovered there, thanks to the ingenuity of researchers Aleksander Wolszczan and Dale Frail.
The first exoplanets discovered were gas giants. Its size facilitated observations (Source: Pixabay/Elchinator)Source: Pixabay
To understand how this discovery was made, we must know a little better about pulsars. Also known as a neutron star, they rotate at a very constant frequency. So constant that they are considered the most punctual bodies in the entire universe.
These two researchers observed a small, totally unexpected irregularity in the rotation of the body named PSR B1257+12. There was no explanation for the phenomenon except one: the pulsar was being pulled by the gravitational field of two planets.
Each of them has three to four times the mass of the Earth and the discovery was a revolution in its time. Immediately researchers around the globe began looking for irregularities in every known star.
In search of a planet like ours
The most ambitious plan was to find a exoplanet orbiting a Sun-like star. After all, since then humanity has already wondered if we were alone in the universe, and the hunt for other worlds could shed new light on the question.
The objective was achieved in 1995. Didier Queloz discovered a planet with the mass of Jupiter surrounding the F-Type 51 Pegasi star, about 50 light-years from Earth. It was the wobble of that distant sun that provided the clue to the find, which won him the Nobel Prize in Physics in 2019.
The technique used by Queloz was the most popular during the 1990s. Known as the radial velocity method or Doppler spectroscopy, it measures the wavelength of light emitted by the stars of interest.
Scientists want to find planets similar to ours – with conditions to support life (Source: Pixabay/ChadoNihi)
It is that the brightness of these suns reaches us under the influence of the Doppler effect. If the object is further away, the redder it appears. If it is close, its color moves towards blue. With this it is possible, through calculations, to accurately determine their movement.
And motion, in space, is generated by the effect of gravity. If a star is bouncing back and forth, it is possible that it is a consequence of the gravitational field of a star. planet.
The problem with this technique is that gravity is proportional to mass, and only planets very large ones have some effect on their suns, and yet the result is almost imperceptible, especially at great distances.
But science advances, and today the use of transit photometry is more popular. During the translational motion, it is expected that the exoplanets eventually pass in front of the suns they orbit.
During this passage, naturally, the brightness of this star decreases. Very little, it is true, it may even be less than 1%, but enough for researchers to detect.
This method was only possible with the increasing sensitivity of modern measuring devices. There is even a NASA planet-hunting spacecraft in space called the Kepler. She is the record holder for finding new worlds, and makes use of this technique.
The first exoplanets were discovered by the movement of their suns, which revealed their gravitational influence (Source: Pixabay/flflflflfl)Source: Pixabay
Occasionally, a lucky astronomer even gets a direct photo of a exoplanet. This is not the best technique, because the brightness of these worlds is weak and they are almost always overshadowed by the star they orbit. But in some cases it happens – to be precise, 57 times, according to NASA data.
It is also worth remembering that the first celestial body announced as exoplanet to be photographed directly was the Fomalhaut b. It became very famous, but in the end the researchers discovered that it was just a cloud of space dust.
types of exoplanets
Twenty-five years later, astronomers have discovered so many exoplanets that it is already possible to make even a simple classification of them. Below are the main types:
- Hot Jupiter: These are the gas giants of distant space. Because of their size, they were among the first to be discovered. In addition, they tend to orbit very close to their sun, pronouncing the effect of the gravitational field. That’s why they are considered planets super hot.
Hot Jupiters intrigue researchers because planets with that much mass they shouldn’t be so close to stars. The theory is that they formed in more distant places and something, as a phenomenon astronomicalmoved them to where they are today.
- Super-Earth: St. planets rocky, like ours, but with greater mass, reaching the weight of the smallest gas giants in the solar system, Neptune and Uranus.
- Mini-Neptunes: exoplanets with up to ten times the mass of Earth, but that also do not reach the size of Neptune and Uranus. It is very likely that they are gaseous.
- Oceanic Worlds: St. exoplanets that contain a substantial amount of liquid water, either as surface or subsurface oceans.
- Frost Giants: St. planets gases that, unlike Jupiter and Saturn, are made of volatile compounds such as water, methane and ammonia.
- planets Earthlike: It is not enough for a planet be rocky to be similar to ours. It needs to be in the area known as “Goldilocks”: neither too close nor far from the sun, just enough to have liquid water. In these planets researchers devote their efforts to finding life.
Distant worlds could contain ideal conditions for life (Source: Pixabay/flflflflfl)Source: Pixabay
The search for a true Earth twin continues. In June 2019, the discovery of Teegarden b, the closest to ours, was announced. planet seen until today, with 95% similarity.
But with the advancement of technology, exoplanets are discovered daily by researchers. Thus, the dream of finding life beyond Earth is still brighter than ever, and may even come true. Perhaps sooner than we think.