exoplanets

Over the past few decades, astronomers have discovered thousands of exoplanets, planets that orbit stars outside of our solar system. Among these discoveries, some planets stand out due to their uniqueness. In this paper, we will explore some of the most unique planets that astronomers have found, including hot Jupiters, diamond planets, and water worlds. We will also discuss how these planets challenge our understanding of planetary formation and evolution.

Hot Jupiters

Hot Jupiters are gas giant planets that orbit very close to their parent stars, with orbital periods of just a few days. These planets are hot because they receive a large amount of radiation from their host stars. The first hot Jupiter was discovered in 1995, and since then, astronomers have found hundreds of these planets.

One of the most interesting hot Jupiters is HD 209458 b, located about 150 light-years from Earth. This planet is about the same size as Jupiter but much hotter, with a temperature of around 1,000 degrees Celsius. HD 209458 b is also very close to its host star, with an orbital period of just 3.5 days. This proximity has allowed astronomers to study the planet’s atmosphere, which has revealed the presence of water vapor, carbon dioxide, and other molecules. These observations have challenged our understanding of planetary atmospheres and have raised questions about how hot Jupiters form and evolve [1].

Diamond Planets

Diamonds are known for their hardness and rarity, but did you know that there are planets made of diamonds? In 2012, astronomers discovered two exoplanets that are believed to be composed mostly of diamond. These planets, named PSR J1719-1438 b and PSR J1719-1438 c, are located about 4,000 light-years from Earth and orbit a rapidly spinning neutron star.

The planets are believed to have formed from the remains of a white dwarf star, which had shed its outer layers and left behind a core of mostly carbon. The intense gravity of the neutron star then compressed the carbon into diamond. These planets are estimated to be about five times the size of Earth but much denser, with a mass equivalent to several Jupiters. The surfaces of these planets are believed to be covered in graphite, with diamonds possibly present deep below the surface [2].

Water Worlds

Water worlds are planets that are covered by a deep ocean, with no or very little land. These planets have been a subject of scientific speculation for many years, and in 2019, astronomers discovered one of the most promising candidates for a water world yet. The planet, named K2-18 b, is located about 110 light-years from Earth and is about twice the size of Earth.

K2-18 b is believed to have a thick atmosphere and a temperature that ranges from -73 to 47 degrees Celsius. Astronomers have detected water vapor in the planet’s atmosphere, and the planet is thought to have a rocky core surrounded by a layer of water. This discovery has raised the possibility of life on other planets, as water is a necessary ingredient for life as we know it [3].

Tatooine-like Planets

Tatooine, the fictional planet from the Star Wars movies, is known for its two suns. But did you know that there are real-life planets that orbit two stars? These planets, called circumbinary planets, are rare but have been discovered by astronomers.

One of the most interesting circumbinary planets is Kepler-16b, located about 200 light-years from Earth. This planet is about the size of Saturn and orbits two stars that are about 20 million kilometers apart. Because of the two suns, the planet experiences two sunrises and two sunsets each day. Kepler-16b is also very cold, with a temperature of around -100 degrees Celsius, due to its distance from the stars. The discovery of circumbinary planets challenges our understanding of how planets form, as it was previously thought that planets could not form in such a chaotic environment [4].

Super Earths

Super Earths are planets that are larger than Earth but smaller than Neptune, with sizes ranging from 1.5 to 2 times the size of Earth. These planets have been the focus of much research in recent years, as they are believed to be the most common type of exoplanet.

One of the most interesting super Earths is Kepler-452b, located about 1,400 light-years from Earth. This planet is about 1.6 times the size of Earth and orbits a star that is very similar to our sun. Kepler-452b is also located in the habitable zone of its star, the region where the temperature is just right for liquid water to exist on the surface. This has led to speculation that the planet may have liquid water and could potentially support life [5].

Conclusion

In conclusion, the discovery of exoplanets has led to a wealth of fascinating discoveries, including hot Jupiters, diamond planets, water worlds, Tatooine-like planets, and super Earths. These planets challenge our understanding of planetary formation and evolution and raise questions about the possibility of life on other planets. As astronomers continue to discover new exoplanets, we can expect to learn even more about the diversity of planetary systems in our galaxy and beyond.

Source List:

[1] Charbonneau, D., Brown, T. M., Noyes, R. W., & Gilliland, R. L. (2002). Detection of an extrasolar planet atmosphere. The Astrophysical Journal, 568(1), 377-384.

[2] Bailes, M., Bates, S. D., Bhalerao, V., Bhat, N. D. R., Burgay, M., Burke-Spolaor, S., … & Keith, M. J. (2011). Transformation of a Star into a Planet in a Millisecond Pulsar Binary. Science, 333(6050), 1717-1720.

[3] Tsiaras, A., Waldmann, I. P., Zingales, T., Rocchetto, M., Morello, G., Damiano, M., … & Tinetti, G. (2019). Water vapour in the atmosphere of the habitable-zone eight-Earth-mass planet K2-18 b. Nature Astronomy, 3(12), 1086-1091.

[4] Doyle, L. R., Carter, J. A., Fabrycky, D. C., Slawson, R. W., Howell, S. B., Winn, J. N., … & Welsh, W. F. (2011). Kepler-16: A transiting circumbinary planet. Science, 333(6049), 1602-1606.

[5] Jenkins, J. M., Caldwell, D. A., Chandrasekaran, H., Twicken, J. D., Bryson, S. T., Quintana, E. V., … & Klaus, T. C. (2015). Discovery and validation of Kepler-452b: a 1.6 R$_{\oplus}$ super Earth exoplanet in the habitable zone of a G2 star. The Astronomical Journal, 150(2), 56.

The exoplanet imager’s first image: not an exoplanet. http://www.space.com/

To date astronomers have discovered well over 1,000 exoplanets, or planets that circle stars outside of our own solar system. According to NASA, there are 3603 objects that are candidates for being an exoplanet, and 1015 confirmed exoplanets (verified by several different observers with several different instruments, reaching a minimum confidence level of 99.9999%).

All of these planets were found by NASA’s Kepler telescope, which also happens to be a solar powered spacecraft. Unfortunately Kepler does not allow us to know the composition of each planet, only that a planet is or isn’t there. Now, due to the creation of a new, high powered observational tool, all that is changing.

A look at how Gemini functions. http://spie.org/

Throughout history hundreds of different observational tools have been created to observe the universe. Even before it was understood that we are part of a galaxy, let alone surrounded by exoplanets, human eyes looked to the stars in wonder and awe. Now we have the power to not only view those stars close up, but to also view the very composition of their planets. The tool that affords us this power is called the Gemini Planet Imager. The imager is an optical enhancement currently being used in the Gemini South telescope in Chile. It was built by a team of U.S. and Canadian institutions, funded by the Gemini Observatory, which is an international partnership comprising the U.S.A., U.K., Canada, Australia, Argentina, Brazil & Chile. Gemini is also partially funded by NSF, NASA, the University of California and the Laboratory Directed Research and Development funding at the Lawrence Livermore National Laboratory.

Humanity already has multiple massive telescopes including the Kepler and Hubble orbiting the Earth, why can’t they just do Gemini’s job? The purpose and function of the Gemini Planet Imager is uniquely different when it comes to exoplanet detection. Kepler locates exoplanets indirectly by focusing on a star and finding the “dark” spot the planet produces on the image when orbiting between the star and the telescope. Gemini on the other hand takes a more direct approach by directly detecting the light an exoplanet gives off. According to the Gemini Planet Imager website,

GPI will detect DIRECTLY the light from an extrasolar planet…Almost 1,000 extrasolar planets are known today, but mostly through indirect Doppler techniques that indicate the planet’s mass and orbit or transit events that measure the planet’s size and orbit. If we can directly pick out a planet from the star’s glare, we can use spectroscopy to measure the planet’s size, temperature, gravity, and even the composition of its atmosphere. By targeting many stars we will understand how common or unusual our own planetary system may be.

The periodic table of exoplanets as of January 2013. http://phl.upr.edu/

The Gemini Planet Imager saw light for the first time in November 2013, and has been working without a hitch ever since. Being eight times more sensitive than any existing imaging device, Gemini is the crowning achievement on an entire year of exoplanet discovery and analyzation in 2013. It can even scan and processes images 100x faster, taking only 60 seconds.

The galaxy is a huge place, and although the Kepler telescope has detected thousands of planets and stars, that doesn’t even scratch the surface of the 300 to 400 billion stars in the Milk Way Galaxy. The Gemini Planet Imager will at least give us a little more quality to the small quantity of planets we have in our planet image menagerie.

Our potential new homes. http://www.bbc.co.uk/

The Kepler telescope and the Gemini Planet imager focus specifically on finding exoplanets similar to Earth. Scientists generally categorize discovered exoplanets by size relative to Earth. In a study published in the Proceedings of the National Academy of Sciences of the United States of America on October 22, 2013, Scientists stated that after observing 42,000 Sun-like stars analyzed by Kepler, they had found,

603 planets, 10 of which are Earth size and orbit in the habitable zone, where conditions permit surface liquid water…22% of Sun-like stars harbor Earth-size planets orbiting in their habitable zones.

Along with Earth-like planets, astronomers have also discovered a solar system that shares a relatively large number of similarities with our own. It’s a good thing there isn’t a precise Earth analogue in the system otherwise there would be no way to prove that the system isn’t just one cosmically gigantic mirror. Our collective sanity has been spared.

Great technology will of course give rise to greater technology ad infinitum. That means a Google Galaxy ‘planet surface view’ is in humanity’s future. Awesome.