In a new study, researchers have discovered the first Earth-sized planet.
The discovery was by NASA’s Transiting Exoplanets Survey Satellite (TESS).
TESS discovered a nearby system that hosts the planet and a warm sub-Neptune-sized world.
The research was conducted by a team of astronomers that includes Carnegie’s Johanna Teske, Paul Butler, Steve Shectman, Jeff Crane, and Sharon Wang.
TESS uses ground-based telescopes and instruments to survey the sky.
One such tool is the Planet Finder Spectrograph on the Magellan II telescope at Carnegie’s Las Campanas Observatory in Chile. This telescope played a key role in this study.
It helped to confirm the planetary nature of the TESS signal and measure the mass of the newly discovered sub-Neptune.
Currently, measuring the masses of individual planets is very important to determine a planet’s density or its general chemical composition.
This is because a star’s gravity influences the planet orbiting it, and the planet’s gravity also affects the star in turn.
The method can help astronomers detect these tiny wobbles that the planet’s gravity induces in the star’s orbit.
The team found a planet HD 21749b has an orbit that takes about 36 days to complete. It has about 23 times Earth’s mass and a radius of about 2.7 times Earth’s.
Its host star has about 80% of the mass of our Sun and is found about 53 light-years distant from Earth.
The researchers found that the planet has a substantial atmosphere but is not rocky.
It also has a sibling planet, HD 21749c. This planet takes about eight days to orbit the host star and is much smaller—similar in size to Earth.
The researchers suggest that TESS’s observations provide important information about small exoplanets in our galaxy.
With the data, they can learn more about their diversity and about how they compare to the planets in our own Solar System.
The lead author is Diana Dragomir of MIT’s Kavli Institute for Astrophysics and Space Research.
The study is published in the Astrophysical Journal Letters.
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