Exoplanets - The Worlds Beyond
By Winnie Jiang
Main Article
When you think of the universe, you think of the broad possibilities it contains. Our star, the Sun, is only one in 200 billion stars in our galaxy. And our galaxy is only one in a billion galaxies in the universe. How many planetary systems could be out there? And how many possible lives could the universe contain? People have wondered about the worlds beyond us for hundreds of years. However, it wasn’t until January 9th, 1992, that Aleksander Wolszczan and Dale Frail discovered the first two exoplanets.
These two exoplanets orbit a pulsar (fast-spinning neutron stars that generate regular pulses of electromagnetic radiation), ​​PSR B1257+12, with another exoplanet later discovered in 1994.
The two planets farthest away from its star are Super-Earths. They are more massive than Earth; however, they are lighter than the ice giants Neptune and Uranus, a planet type unlike any planets in our solar system.
The planet nearest its star, PSR B1257+12 b, is a terrestrial planet like our Earth, Mars, Mercury, and Venus. Nevertheless, it is only 0.02 the mass of Earth, which is like the mass of a hamster compared to an adult red kangaroo.
Although all three planets are uninhabitable due to the high radiation they experience from the neutron star they are orbiting, it is a start for astronomers and boosted many’s curiosity to explore more.
Many more exoplanets share the same planet type, like the three planets orbiting PSR B1257+12. But many others are not. They are likely Gas Giants like our Jupiter and Saturn or Neptune-like planets like Uranus and, well, Neptune.
One notable Gas Giant is Kepler-90h. It is a Gas Giant with a mass 1.2 times bigger than Jupiter. And it orbits its star with seven planet companions! Three of its companions, Kepler-90d, Kepler-90e, and Kepler-90f, are Neptune-like planets.
While scientists have found 5014 exoplanets already, they are still discovering more.
The star nearest to us has an exoplanet orbiting around it. It is called Proxima Centauri b, which is 4.25 light-years away from us. Although it is still the nearest exoplanet, it would take approximately 158,100 human years to reach it at the current speed of a space shuttle.
Proxima Centauri b is a Super Earth Exoplanet. It takes only 11.2 Earth days to orbit around its star once. Despite its closeness to its star, it is actually in its star’s habitable zone. Meaning that the area it orbits in is not too hot or too cold, where liquid water, the fundamental element of life, could exist.
However, that does not mean Proxima Centauri b is habitable. Proxima Centauri b experiences ultraviolet radiation hundreds of times greater than what the Earth does from our Sun. Stripping away the lightest molecules, Hydrogen; Over time, the radiation also stripped away heavier elements such as Nitrogen and Oxygen.
A computer model published in Astrophysical Journal Letters that was a part of a NASA study simulated the scenario of what would happen if it was Earth that orbits in Proxima Centauri b’s orbit. The study shows that the radiation Proxima Centauri, the red dwarf star Proxima Centauri b orbits radiates, will not allow our atmosphere to survive.
Although there might be a chance that water could exist on Proxima Centauri b, the absence of an atmosphere, an equally important component to life, made Proxima Centauri b possibly inhabitable.
Although possibly habitable exoplanets are rare, scientists have found dozens of potentially habitable exoplanets. It might still be out of our reach to travel to one of the exoplanets, but with continuous efforts and innovative ideas, those journeys into deep space will come true in the near future. Every second, millions of ideas bloom, and one of them will be a solution to our question; we will have to explore, and what sounds like a dream will soon become a reality.
Vocabulary
Galaxy:
A galaxy is a huge collection of gas, dust, and billions of stars and their solar systems, all held together by gravity. (NASA Space Place)
Exoplanet:
Planets that lie beyond our solar system.
Pulsar:
Fast-spinning neutron stars that generate regular pulses of electromagnetic radiation
Neutron star:
Neutron stars are the collapsed cores of some massive stars. They pack roughly the mass of our Sun into a region the size of a city. (Miller, UMD)
Super-Earth:
A class of planets unlike any in our solar system – are more massive than Earth yet lighter than ice giants like Neptune and Uranus, and can be made of gas, rock or a combination of both. (NASA)
Gas Giants:
A large planet mostly composed of helium and/or hydrogen. (NASA) Such as Jupiter and Saturn.
Neptune-like Planets:
Similar in size to Neptune or Uranus in our solar system […]. (They) typically have hydrogen and helium-dominated atmospheres with cores or rock and heavier metals.
Terrestrial Planets:
AKA rocky planets. They are primarily made of rocks and metals. Within our solar system, the terrestrial planets are: Mercury, Venus, Earth, and Mars. Terrestrial exoplanets are between half of Earth’s radius to twice of Earth’s size.
Orbit:
An orbit is a regular, repeating path that one object in space takes around another one. (NASA)
Habitable zone:
An area around stars where it is not too hot or too cold, where liquid water, the fundamental element of life, could exist.
Red dwarf:
Red dwarfs are the most common star type in the main sequence. Where they are the smallest and the coolest. They also have a long life span.
More Suggested Resources:
Exoplanet Catalog | Discovery – Exoplanet Exploration: Planets Beyond our Solar System
NASA's Eyes (Strongly Recommend)
Exoplanets: Crash Course Astronomy #27
References:
Byrd, D. (2017, August 1). No Earth-like atmosphere for Proxima b | Space. EarthSky. Retrieved May 03, 2022, from https://earthsky.org/space/proxima-b-earth-like-atmosphere-study-2017/
Charbonneau, D., & Brown, T. (n.d.). Historic Timeline | Explore – Exoplanet Exploration: Planets Beyond our Solar System. Exoplanet Exploration. Retrieved June 16, 2022, from https://exoplanets.nasa.gov/alien-worlds/historic-timeline/#first-exoplanets-discovered
ESA. (n.d.). ESA - Stars: Neutron stars, pulsars and magnetars. European Space Agency. Retrieved May 03, 2022, from https://www.esa.int/Science_Exploration/Space_Science/Stars_Neutron_stars_pulsars_and_magnetars
Extreme Planets. (2008, March 23). NASA. Retrieved May 02, 2022, from https://www.nasa.gov/multimedia/imagegallery/image_feature_574.html
How Many Solar Systems Are in Our Galaxy? (n.d.). NASA Space Place. Retrieved May 04, 2022, from https://spaceplace.nasa.gov/other-solar-systems/en/
NASA. (n.d.). Exoplanet-catalog – Exoplanet Exploration: Planets Beyond our Solar System. Exoplanet Exploration. Retrieved May 04, 2022, from https://exoplanets.nasa.gov/exoplanet-catalog/7134/psr-b125712-b/
NASA. (2020, September 21). Proxima b 3D Model – Exoplanet Exploration: Planets Beyond our Solar System. Exoplanet Exploration. Retrieved May 04, 2022, from https://exoplanets.nasa.gov/resources/2211/proxima-b-3d-model/
NASA. (2022, February 1). Overview | Beyond Our Solar System – NASA Solar System Exploration. NASA Solar System Exploration. Retrieved May 03, 2022, from https://solarsystem.nasa.gov/solar-system/beyond/overview/