NASA’s Kepler mission captured headlines late last month after the discovery of Kepler-452b. Jon Jenkins, Kepler data analysis lead at NASA’s Ames Research Center described the exoplanet as an “older, bigger cousin to Earth.”
But, the Kepler spacecraft isn’t the only possible way for astronomers to spot alien worlds. In December 2014, the Nordic Optical Telescope on La Palma made history as it became the first ground-based telescope to observe an exoplanet (55 Cancri e).
More than six months later, history is being made with the discovery of 51 Eridani b. It’s the first exoplanet discovered by the Gemini Planet Imager (GPI), a new instrument on the 8-meter Gemini South Telescope in Chile.
The Gemini South Telescope doesn’t use the transit method like Kepler. Instead, it detects exoplanets via “direct imaging.” Adaptive optics is used to sharpen the image of the target star. Then, its starlight is blocked. Whatever incoming light is left is analyzed with the brightest spots indicating a possible exoplanet.
The image below illustrates this method perfectly.
Discovery image of the exoplanet 51 Eridani b taken in the near-infrared light with the Gemini Planet Imager on Dec. 21, 2014. The bright central star has been mostly removed to enable the detection of the million times fainter planet.
Credits: Gemini Observatory and J. Rameau (UdeM) and C. Marois NRC Herzberg
“This is exactly the kind of planet we envisioned discovering when we designed GPI”, said James Graham, professor and project scientist for GPI, in a press release on Friday.
What’s 51 Eridani b like?
51 Eridani b grabs the record (via direct imaging) for the lowest-mass exoplanet yet imaged. Its mass is about twice that of Jupiter. The average directly-imaged planets have a mass five times of Jupiter or more.
Besides being the smallest exoplanet spotted using direct-imaging, 51 Eridani b is also the coldest. Temperatures are just a balmy 800 degrees Fahrenheit, 400 degrees colder than the other exoplanets like it.
Astronomers also noted the strongest atmospheric methane signal ever seen on an alien planet. Previously discovered Jupiter-like exoplanets had faint traces of methane. 51 Eridani b’s methane signature suggests it’s a lot like what models suggest Jupiter was like in its early years.
“Since the atmosphere of 51 Eri b is also methane rich, it signifies that this planet is well on its way to becoming a cousin of our own familiar Jupiter,” said Mark Marley, an astrophysicist at NASA’s Ames Research Center.
The Gemini Planet Imager was specifically designed to help astronomers understand how solar systems form. With the discovery of this exoplanet, astronomers hope to better understand the formation of gas giants like Jupiter.
“The newly discovered 51 Eri b is the first planet that’s cold enough and close enough to the star that it could have indeed formed right where it is the ‘old-fashioned way,” Bruce Macintosh, a professor of physics at Stanford University, said. “This planet really could have formed the same way Jupiter did – the whole solar system could be a lot like ours.”
The Gemini Observatory
Two nearly identical 8-meter telescopes make up the Gemini Observatory. The Gemini South Telescope calls Cerro Pachón, Chile home. While the Gemini North Telescope sits atop Mauna Kea in Hawaii. The pair of telescopes provides astronomers with almost complete coverage of the skies in both hemispheres.
The two telescopes capture images of our universe through infrared. A special protected silver coating on its massive 8-meter mirrors gives the pair of telescopes an edge when observing through the mid-infrared.
Another advantage of the Gemini Observatory is known as Queue Mode. Observations are prioritized based on viewing conditions. One night of stargazing could see Gemini South Telescope go from hunting exoplanets to viewing gamma-ray bursts. A suite of instruments can be switched at will depending on the type of observations being made.
Here are two additional images captured by the Gemini Observatory.
Watch the video below to learn more about the Gemini Observatory.