NASA confirmed today during a press conference that seven Earth-sized planets are orbiting a single, ultra-cool dwarf star. The star, designated TRAPPIST-1, has about eight percent the mass of our Sun and is about 40 light years away. Six of the exoplanets (worlds that exist outside of our solar system) orbit the star at a close enough range to suggest the presence of liquid water while three of them are in the habitable zone.
This “Goldilocks zone” or “just right” positioning makes these worlds prime candidates for further investigation into each of their atmospheric potentials for harboring extraterrestrial life.
“This discovery could be a significant piece in the puzzle of finding habitable environments, places that are conducive to life,” said Thomas Zurbuchen, associate administrator for NASA’s Science Mission Directorate in a briefing. “Answering the question of ‘are we alone’ is a top science priority and finding so many planets like these for the first time in the habitable zone is a remarkable step forward toward that goal.”
To compare, our Sun is approximately 4.6 billion years old while TRAPPIST-1 is about 500 million, and burning about half as hot. The first three planets discovered had nearly matching orbits measuring 1%, 1.5% and 3% of Earth’s orbit of our Sun. Their “year” ranged between 1.5 days to 73 days which indicates a very close proximity to their young star.
Those planets were initially observed between September to December of 2015 and announced in May of last year. Researchers and Astronomers used the TRAPPIST (Transiting Planets and Planetesimals Small Telescope) at the LA Silla Observatory in Chile to continually observe the small host star.
TRAPPIST, as a transit photometry telescope, originally detected the three orbiting planets around the Jupiter-sized star due to the small, periodic dips in light that indicate a “transiting” or passing of an object. At first, astronomers only saw two transit signals but after further examination of the star with the infrared-equipped Very Large Telescope in the Atacama Desert of northern Chile, they crunched the numbers from a light curve which confirmed a telling eclipse and a third planet.
In February of 2016, just months after the startling discovery, researchers decided to intensify their observations of TRAPPIST-1 using the Spitzer Space Telescope which is equipped with infrared imaging. After the Spitzer observed six transit windows or dips of light, the investigation was ramped up with an international ground effort.
Beginning in May of 2016, the TRAPPIST telescope located high in the Chilean mountains but controlled by the European Southern Observatory in Belgium, once again began observing the star. Researchers also activated the TRAPPIST-North in Morocco and utilized telescopes in Hawaii, Spain, and South Africa. Many potential transit indicators were detected so they needed to dismiss the false positives.
On September 19th, 2016, a 20-day non-stop observation of TRAPPIST-1 began again with NASA’s Spitzer Space Telescope to help narrow the candidates. By examining light curves during the ground operation and further study with Spitzer, they were able to confirm a few possible planets as actually being smaller objects.
By comparing the data sets from various observations, astronomers were able to confidently determine the existence of four more planets orbiting TRAPPIST-1 and published the findings in the journal Nature today.
The confirmation was made with a few factors. TRAPPIST-1’s orbiting planets each displayed a series of unique transits and the shapes of each planet’s transit signal was consistent throughout observation. They also noticed that one of the now-confirmed seven orbiting worlds is “orphaned” from the others due to its outermost location and, its mass has yet to be measured.
So what are these planets like? Five of them are very similar in size to Earth while the other are described by researchers as somewhere between the size of Mars and Earth. Mass estimates tell researchers that the six inner planets may be rocky. If you wanted to visit, it would take about 40 years to get there travelling at the speed of light. The speed of light is 186,000 miles per second.
Researchers theorize that the planets around TRAPPIST-1 may be tidally locked, with one side of their surfaces always facing the star. This feature results in a weather pattern that could be completely different (and far more chaotic) from Earth’s. The planets also experience a constant day or night on each side with winds from one surface creating extreme weather on the other.
NASA will open a new window to observe the known universe when they launch the James Webb Space Telescope in 2018. The telescope will act as the “science successor” to the Hubble and will have extraordinary capabilities in infrared light sensitivity and resolution, which will be used to further examine potentially habitable exoplanets around stars like TRAPPIST-1 for signs of a life-harboring atmosphere and water.
By actually examining how the light changes when a planet is transiting a star, astronomers can begin to determine if any by-products of life exist there.
Exoplanet discoveries are a recent breakthrough in astronomical research and given the 100 billion galaxies (and counting) each with billions of stars spread across an unimaginable distance, the search for potentially habitable worlds has barely begun. Between the very first detection of an exoplanet in 1988 up to now, there have been over 3,500 confirmed worlds announced.