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NASA planet hunter finds Earth-sized world in ‘Goldilocks zone’
WASHINGTON, Jan 7, 2020 (BSSAFP) – NASA said Monday that its planet
hunter satellite TESS had discovered an Earth-sized world within the
habitable range of its star, which could allow the presence of liquid water.
The planet, named “TOI 700 d”, is relatively close to Earth — only 100
light years away, NASA’s Jet Propulsion Laboratory announced during the
annual American Astronomical Society meeting in Honolulu, Hawaii.
“TESS was designed and launched specifically to find Earth-sized planets
orbiting nearby stars,” said Paul Hertz, NASA astrophysics division director.
TESS initially misclassified the star, which meant the planets appeared
larger and hotter than they actually are. But several amateur astronomers,
including high school student Alton Spencer — who works with members of the
TESS team — identified the error.
“When we corrected the star’s parameters, the sizes of its planets
dropped, and we realized the outermost one was about the size of Earth and in
the habitable zone,” said Emily Gilbert, a graduate student at the University
of Chicago.
The discovery was later confirmed by the Spitzer Space Telescope.
A few other similar planets have been discovered before, notably by the
former Kepler Space Telescope, but this is the first discovered by TESS,
which was launched in 2018.
TESS stabilizes on one area of the sky to detect whether objects —
planets — pass in front of stars, which causes a temporary drop in the
stars’ luminosity. This allows TESS to infer the presence of a planet, its
size and orbit.
Star TOI 700 is small, about 40 percent of our Sun’s size and only about
half as hot.
TESS discovered three planets in orbit, named TOI 700 b, c and d. Only “d”
is in the so-called habitable zone, not too far from and not too close to the
star, where the temperature could allow the presence of liquid water.
It is about 20 percent larger than Earth and orbits its star in 37 days.
“d” receives 86 percent of the energy that Earth receives from the Sun.
It remains to be seen what d is made of. Researchers have generated models
based on the size and type of star in order to predict d’s atmospheric
composition and surface temperature.
In one simulation, NASA explained, the planet is covered in oceans with a
“dense, carbon-dioxide-dominated atmosphere similar to what scientists
suspect surrounded Mars when it was young.”
The planet is tidally locked to the star, meaning that one side always
faces the star, as is the case with the Moon and Earth.
This synchronous rotation meant that, in another model, one side of the
planet was constantly covered in clouds.
A third simulation predicted an all-land world, where winds flow from the
planet’s dark side to its light one.
Multiple astronomers will observe the planet with other instruments, in
order to obtain new data that may match one of NASA’s models.
BSS/AFP/BZC/1200HRS