Buzz
Exoplanets, also known as 'extrasolar planets,' are worlds located outside our solar system. They are named by adding a lowercase letter, beginning with 'b' and continuing to 'z' depending on the order in which they were discovered, to the Flamsteed designation or catalog number of their parent star.
When PSR1257 + 12 B and PSR1257 + 12 C were first identified in the early 1990s (these were labeled with uppercase letters since the current naming system had not yet been adopted), and later followed by 51 Pegasi b, the first confirmed exoplanets, these discoveries were celebrated as monumental advancements in Astronomy, comparable to the Copernican Revolution. They sparked excitement within the scientific community and reignited the possibility of discovering Earth-like planets and possibly even extraterrestrial life. Prior to these discoveries, the idea of exoplanets was dismissed by most credible astronomers, and discussing them was often seen as pure science fiction. However, these discoveries changed the field dramatically, and the study of exoplanets, known as Exoplanetology, has since flourished, with over 400 exoplanets discovered (30 of which were found in October 2009 alone). However, many of these discoveries were somewhat similar to the initial ones: hot, bloated gas giants orbiting very close to their stars, with orbital periods measured in days, often referred to as 'roasters,' and brown dwarfs – failed stars that can easily be confused with the most massive planets.
The most likely reason for this trend is that the most widely used indirect methods of detecting exoplanets tend to favor large, heavy planets with short orbital periods, making them easier to identify. However, from time to time, thanks to advances in technology, new techniques for improving detection, and a bit of fortune, some surprising findings emerge:
15. Oldest Planet PSR B1620-26 b (discovered: May 30, 1993, confirmed: July 10, 2003)
PSR B1620-26 b, affectionately called 'Methuselah' for its biblical association, is the oldest exoplanet discovered to date, estimated at 13 billion years old. This could make it the oldest known planet, considering the Universe itself is just slightly older, at 13.7 billion years. It was located deep within the heart of a 'globular cluster'—a dense group of ancient stars formed shortly after the Big Bang. Given that planets typically form shortly after their parent star, the advanced age of the star suggests the planet must also be very old. Although confirmed as a planet only in 2003, this discovery is promising for planet hunters because if planets can form so early after the Big Bang, they must be common in the Universe.
14. Nearest to Our Solar System Epsilon Eridani (Epsilon Eridani b discovered August 7, 2000)
Epsilon Eridani, often referred to as a planetary system much like our own, is home to a parent star—its 'sun'—with at least two suspected planets: one confirmed (Epsilon Eridani b) and another (Epsilon Eridani c) still under investigation. This system is located just over 10 light-years away, making it the closest known planetary system to ours. It boasts two asteroid belts—one located between the star and Epsilon Eridani b, and another between b and c—along with a dust ring beyond c’s orbit, thought to be caused by extrasolar comets colliding.
13. Most Suns 91 Aquarii b (November 16, 2003)
While we typically associate planets with stars in single-star systems, a surprising number—about half—of the stars we observe in the night sky are actually part of multiple star systems. These systems consist of two or more stars orbiting a common center of mass, and they appear as a single point of light due to their vast distance from us. The 91 Aquarii system contains five stars, and in November 2003, it was discovered that a gas giant planet orbits the primary star, 91 Aquarii A. As a result, the planet is also known as 91 Aquarii Ab, to differentiate it from the other stars in the system and allow for the potential discovery of additional planets orbiting those stars. This particular gas giant is unique because detecting exoplanets around stars requires great precision, and the presence of nearby stars can often interfere with this process, making it one of the few planets identified in a multi-star system.
12. Most Exoplanets in a Single System 55 Cancri (55 Cancri b discovered April 12, 2006)
This system closely resembles the previous one, as it is a binary star system—two stars orbiting each other, much like Tatooine (which, by the way, has become a term in scientific discussions for planets in multiple star systems after the hypothetical discovery of HD 188753 Ab, believed to be the first 'Tatooine planet' in 2005 but later disproven). In this case, five medium-sized 'Neptune-mass' planets orbit the larger star, 55 Cancri A, in the following order from the star: 55 Cancri e, b, c, f, and d (or 55 Cancri Ae, Ab, Ac, Af, and Ad, to distinguish them from the other star, 55 Cancri B). This makes it the largest number of confirmed planets orbiting a single star, aside from our own Sun, highlighting the possibility that more planets could be found around stars, whether they have known planetary systems or not, suggesting our solar system is not one-of-a-kind.
11. Exoplanet’s Atmospheric Composition Discovered HD 209458 b (November 5, 1999)
HD 209458 b is another unique gas giant in that its orbital plane aligns perfectly with our line of sight, meaning it periodically passes in front of its parent star, as seen from Earth. This 'transit' allows us to better determine the planet's size by observing how much of its star’s light is blocked during each pass, and more crucially, it enables us to analyze the composition of its atmosphere via spectroscopy—the study of radiation-matter interactions, in this case, the interaction between the planet’s atmospheric gases and its sun’s starlight. Through this technique, astronomers have detected sodium vapor, and more recently (October 2009), they identified water vapor, carbon dioxide, and methane in the planet’s atmosphere. It also became the second known planet to contain organic compounds, following HD 189733 b, which was the first on October 5, 2005.
10. Gas Giant in the Habitable Zone Gliese 876 b (June 23, 1998)
The habitable zone refers to the theoretical region around a star where conditions would allow liquid water to exist on a planet similar in size to Earth. Gliese 876 b stands out because it orbits within its sun's habitable zone. Now, you might ask, 'How can it be considered habitable? We can’t live on a gas giant!' While it’s true that humans currently can't live on gas giants, let’s look at the gas giants in our own solar system. They all have substantial icy moons, and it’s possible (though not guaranteed) that Gliese 876 b has similar moons with the potential to support life—think of Pandora and Polyphemus from the movie Avatar. Even if it doesn’t, there’s no reason to dismiss the possibility that life could exist in or around gas giants, as suggested by a study from notable astronomers discussing the potential for life within Jupiter's thick atmosphere.
9. Survivor V391 Pegasi b (March 2007)
This gas giant orbits a white dwarf star, a remnant of a dying star. This suggests that at some point during the star's red giant phase (a large, expanding star before it becomes a white dwarf), the planet likely passed very close to its sun or may have even orbited within the dying star itself! This discovery offers insight into the fate of planets in our solar system, including Earth, as our sun is predicted to enter its red giant phase in about five billion years, potentially engulfing the inner planets and possibly reaching Mars' current orbit. Even if Earth survives the red giant phase, its surface would be completely sterilized by the extreme temperatures of the star.
8. First 'Super-Earth' µ Arae c (August 25, 2004)
Until now, we’ve mostly discussed gas giants in a universe dominated by bloated, hot gas giants, but µ Arae c, the first 'super-Earth,' or large rocky exoplanet, marked a significant step closer to discovering Earth-like planets beyond our solar system. A 'super-Earth' refers to an exoplanet with a mass between Earth’s and the giant planets in our system. These planets are typically rocky because an object the size of Earth, due to its weaker gravitational pull, tends to attract dense, heavy materials like rocks and metals, while lighter materials such as gases are easily blown away by factors like solar radiation or asteroid impacts. However, as the planet grows and approaches the mass of Jupiter, its stronger gravity enables it to retain both heavier and lighter materials, leading it to become a gas giant over time. This discovery highlighted the incredible progress made through technological advancements, achieved by collaboration and continuous innovation in astronomical techniques, which have since allowed us to detect even smaller exoplanets.
7. Possible 'Hot Neptune' Gliese 436 b (August 31, 2004)
It was discovered shortly after the first super-Earth, with similar masses and diameters. However, initial calculations suggested that its density was higher than that of gas giants but not quite as high as that of rocky super-Earths. This led scientists to hypothesize that the planet was primarily composed of the next most abundant compound in the universe: water, which itself is made of two of the most abundant elements—Hydrogen and Oxygen. However, because of the planet’s high mass, small radius, and its close orbit to its star, any water present is thought to exist in exotic forms, such as 'hot ice'—a state where water is compressed into solid form by enormous pressure, much like how carbon atoms become diamonds beneath the Earth’s surface.
6. Lava-coated Super-Earth COROT-7b (February 3, 2009)
COROT-7b was a remarkable discovery for the ever-expanding catalog of exoplanets, sparking excitement when scientists determined that its diameter was approximately 1.7 times that of Earth. Its density and inferred composition seemed similar to Earth’s, making it one of the smallest and most Earth-like exoplanets known at the time. However, its extreme proximity to its sun means that the planet is entirely covered by a sea of molten rock and metal, a consequence of its orbital closeness. Despite the harsh surface conditions, COROT-7b is one of the few super-Earths with an atmosphere, although it is incredibly thin and tenuous, containing trace amounts of water vapor and various metals in gaseous form due to the planet’s extreme surface temperatures.
5. First Planets to be Photographed Fomalhaut b and HR 8799 b, c, d (November 13, 2008)
Observing exoplanets directly is often compared to watching a gnat fly across the face of a searchlight on a foggy day from miles away (source: National Geographic). Fomalhaut b and HR 8799 b, c, and d hold the distinction of being the first exoplanets directly imaged in optical wavelengths, or as we colloquially say, photographed. This groundbreaking achievement was made possible by the combined efforts of massive Earth-based telescopes at W.M. Keck and Gemini Observatories in Hawaii, as well as the Hubble Space Telescope. While this was an extraordinary accomplishment, it's worth noting that the next milestone in planet observation is even more remarkable.
4. Farthest planet from parent to be imaged GJ 758 b (November 2009)
GJ 758 b orbits its star at a distance similar to Neptune’s distance from our Sun, meaning it reflects and receives only a small fraction of its star’s light, much like Neptune. However, photographing an object as faint as Neptune from Earth is already a challenge, so imagine the difficulty of capturing such an object from 50 light-years away (about 500 trillion kilometers or 300 trillion miles) in another star system! This feat was achieved by the Hubble Space Telescope in November 2009. What's particularly intriguing is that the Hubble and other existing telescopes are soon to be replaced by more advanced and powerful instruments, some specifically designed for planet-hunting—like the Terrestrial Planet Finder (TPF), set to launch in 2015 with the mission of discovering terrestrial planets. If the aging Hubble could manage such a remarkable achievement, it’s exciting to think of what new, specialized telescopes will uncover.
3. Most Earth-like Exoplanet Yet Gliese 581 d (April 24, 2007)
This planet, with a mass ranging from 7 to 14 times that of Earth, is classified as a super-Earth. What sets it apart is its position within the habitable zone of its star, and its solid surface, which would allow for liquid water to form oceans and even create landmasses, much like the Earth. Although its surface gravity is much stronger than Earth’s, its similarity to our planet is striking. This resemblance has sparked some to send messages to potential intelligent life forms that might have evolved in ways similar to ours.
2. Super-Earth Closest to Solar System GJ 1214 b (December 16, 2009)
This exoplanet shares many similarities with COROT-7b, but is located closer to Earth at 42 light years, allowing for more detailed study. While its surface temperature is still much higher than Earth's, it is not as extreme as COROT-7b’s, which could potentially support a thicker, denser atmosphere, should one exist.
1. Planetary collision HD 172555 (August 2009)
Using infrared sensors, NASA’s Spitzer Space Telescope detected large amounts of vaporized rock and fragments of hardened lava, known as tektites, typically formed by meteorite impacts. The sheer volume of this material, enough to obscure a star’s light, suggests a massive planetary collision that created this debris.
This discovery reveals that catastrophic, planet-scale collisions are not rare in the universe, reinforcing the theory that the Earth’s moon was formed from a similar event in the distant past. Moreover, computer models predict that future collisions may still occur in our solar system billions of years from now, far beyond the exaggerated timelines some pseudo-scientists may claim.
+ Exoplanet Naming Society
Picture yourself at a party discussing exoplanets and casually mentioning the fascinating PSR1257 + 12 B, PSR1257 + 12 C, PSR B1620-26 b, HD 209458 b, µ Arae c, COROT-7b, GJ 758 b, GJ 1214 b, and HD 172555. This is exactly what led to the creation of the Exoplanet Naming Society just over a year ago. The Society’s goal is to replace the complex scientific names of exoplanets with more accessible mythological names, making it easier to reference them—just like the planets in our solar system. Now, you can join in the excitement and contribute to naming distant celestial bodies that future generations will memorize in their schoolbooks.
