What is an exoplanet? An exoplanet or extrasolar planet, is a planetary body outside our solar system. Most of them are orbiting a star or a star system. However, some do not have a parent star, which we call the ‘rouge planet’. In this post, we’ll delve into exoplanet discovery, and acquaint ourselves with the closest exoplanet, Proxima Centauri b. Ready?

Let’s dive in!

Exoplanet Discovery

The first exoplanet was discovered in 1992 by Aleksander Wolszczan and Dale Frail. It was orbiting a pulsar, a type of neutron star with rapid rotation. This discovery opened the door for further exploration of other planets outside our solar system.

So far, no exoplanet similar to Earth has been found. An “Earth-like exoplanet” is a planet that is similar in size to Earth, possibly with rocky surfaces, and located in the “Goldilocks zone”. However, most of these planets do not have the right temperature or atmospheric composition to support human life, so exploration would require a spacesuit and oxygen support.

Fact!

The Goldilocks zone a.k.a the habitable zone is the sweet spot in an orbital region where conditions may support liquid water. In other words, it should be far enough from the parent star so the planet won’t be scorching hot, but not too far that the planet would be so cold and turned into an icy world.

You may have been wondering how scientists know the characteristics of exoplanets. They are using spectroscopy techniques and simulation. To put it simply, the light we receive from exoplanets or any celestial body through telescopes has its unique spectra. Astronomers can learn about the object, including its chemical composition of the atmosphere, distance, size, and more by analyzing and interpreting the spectra.

Direct Image of Exoplanet

The surface conditions (rocky, gaseous, and hycean) of exoplanets are hypothetical, based on estimates of their size and density. It’s difficult to determine the actual conditions of exoplanets due to the lack of direct images. In September 2022, the James Webb Space Telescope (JWST) captured its first direct image of exoplanet HIP 65426 b, revealing it to be a gas giant without land.

But don’t be disappointed just because it’s not a planet like Earth. This discovery is a big step forward in finding planets outside our solar system. We can expect to see more clear images of other planets outside our solar system, and some of them may be similar to our planet.

Proxima Centauri b – Closest exoplanet

The closest exoplanet to Earth is Proxima Centauri b (or Proxima b). It is located 4.22 light-years or 43 trillion kilometers away from us. It is orbiting its host star, Proxima Centauri, which can be found in the Centauri constellation in the southern sky.

Have you ever wondered why the exoplanet Proxima b has such a name? It’s the way astronomers name the exoplanets. If you applied this rule in naming planets in our solar system, the Sun would be named “Sun” or “Sun a”. Meanwhile, Mercury will be designated as Sun b, Venus as Sun c, and our Earth as Sun d – From now on we can call Earth, Sun d.

Despite being the nearest exoplanet to us, it is still impossible to reach Proxima b. The journey would take about 63,000 years with current spacecraft technology. Furthermore, a lot of studies need to be done to understand more about its condition and determine the feasibility of sending a spacecraft there in the future. 

Proxima Centauri b Details

Scientists reported that Proxima b is within the habitable zone. They also have been contemplating that this planet has the potential to host life. Here is a fun fact about Proxima b:

• Complete one orbiting cycle around the parent star just within 11.186 Earth days!
• Its distance to the parent star is just 0.049 AU or 7.5 million km (20x closer than the distance between Earth and Sun)
• Its radius is slightly larger than Earth with a minimum mass of at least 1.07 of Earth’s mass
• It is tidally locked – one side is permanently facing the star while the other side is in permanent darkness

Referring to the list above, you already know that Proxima b orbits its parent star closer than Earth does to the Sun. However, Proxima Centauri is a red dwarf star, with a temperature of 2 times lower than the Sun’s and 10 times smaller in size. Therefore, Proxima b could be habitable.

Proxima b is tidally locked to its parent star (just like the Moon to Earth), therefore the sunny side is extra hot while the other side is cold. It is still unknown what the composition of Proxima b is. It could be rocky or a waterworld, and the thickness of the atmosphere is also unknown.

Research Finding on Proxima Centauri b

Proxima b was discovered in 2016 through the Radial Velocity Detection Method. Scientists study the exoplanet’s conditions through simulation and use Earth as the model.  It is very important to investigate the conditions of exoplanets in whichever way possible before assuming that they could support life.

A study shows that Proxima b can have strong winds (35 to 70 kmph). This is due to the tidal locking situation of the planet. The planet has a significantly disparate atmospheric pressure between its dark and star-facing sides. Cool, high-pressure air from the dark side flows into the hotter, lower-pressure star-facing hemisphere, resulting in one-way wind flow from the side that is always in darkness to the side that always faces the star. (Navarro et al., 2022).

Summary

The discovery of exoplanets will be continued and the possibility of finding one that is habitable is high. Although the conditions may not be identical to Earth, alien life may have adapted to them. Proxima Centauri b is a potential Earth-like candidate, with the habitable zone possibly located at the terminator. Additionally, it could be an ideal location for harnessing wind energy and flying kites.

Disclaimer:

While we strive to provide accurate and reliable information, please be aware that the content of this blog post is subject to a margin of error. The probability of absolute accuracy is not guaranteed.

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Reference

Navarro, T., Merlis, T. M., Cowan, N. B., & Gomez, N. (2022). Atmospheric gravitational tides of Earth-like planets orbiting low-mass stars. ArXiv. https://doi.org/10.3847/PSJ/ac76cd