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Earth-sized exoplanet discovered is only 55-light years away

The universe is vast, filled with countless stars and planets, many of which remain hidden from our view. But thanks to dedicated astronomers and advanced telescopes, we’re slowly uncovering the secrets of our cosmic neighborhood. One such project, SPECULOOS (Search for Planets EClipsing ULtra-cOOl Stars), has just announced a thrilling discovery: an Earth-sized exoplanet orbiting a nearby “ultracool dwarf” star.

SPECULOOS-3b: The Earth-sized exoplanet

This newfound world, named SPECULOOS-3b, is about the same size as our Earth but orbits a star vastly different from our Sun. SPECULOOS-3 is a star classified as an ultracool dwarf – meaning it’s smaller, cooler, and dimmer than our own star. In fact, it’s about the size of Jupiter and twice as cold as our Sun.

What makes SPECULOOS-3b even more fascinating is its incredibly tight orbit. It zips around its star in just 17 hours, a year that’s shorter than a day on Earth.

Because of this proximity, one side of the planet is always facing the star, locked in a perpetual day, while the other side remains in eternal darkness. This phenomenon, known as tidal locking, results in extreme temperature differences between the two sides.


The SPECULOOS project, led by astronomer Michaël Gillon from the University of Liège, focuses on hunting for planets around ultracool dwarf stars. These stars are faint and scattered across the sky, making their planets difficult to find. Patience and specialized telescopes are essential for this search.

SPECULOOS employs a network of robotic telescopes strategically placed around the world. These telescopes continuously monitor ultracool dwarf stars.

By observing tiny dips in a star’s brightness, astronomers can detect the presence of a planet passing in front of it. This method, known as the transit method, allows scientists to identify and study distant exoplanets.

Earth-sized exoplanet lacks atmosphere

While SPECULOOS-3b’s size is similar to Earth, the similarities end there. The planet orbits extremely close to its star, which results in it being bombarded with intense radiation. SPECULOOS-3b receives sixteen times more energy per second than Earth does from the Sun. This immense amount of radiation creates a harsh environment on the planet’s surface.

The intense radiation likely makes it impossible for the planet to hold onto an atmosphere. “In such an environment, the presence of an atmosphere around the planet is highly unlikely,” said study co-author Julien de Wit, associate professor of planetary sciences at MIT.

Any atmosphere that SPECULOOS-3b might have had would have been stripped away by the star’s relentless energy. Without an atmosphere, the planet cannot retain heat or support conditions necessary for life as we know it.

Temperature of SPECULOOS-3b

This lack of atmosphere also exposes the planet’s surface directly to the star’s radiation, leading to extreme temperature fluctuations. On one side of the planet, which is always facing the star due to tidal locking, temperatures are scorching. Meanwhile, the other side, perpetually in darkness, experiences frigid conditions.

“If there’s no atmosphere, there would be no blue sky or clouds – it would just be dark, like on the surface of the moon,” noted MIT research scientist Benjamin Rackham. “And the ‘sun’ would be a big, purplish-red, spotted, and flaring star that would look about 18 times as big as the sun looks to us in the sky.”

“We think that the planet is nearly as hot as Venus, so not habitable,” said Rackham. “It’s not hot enough to have a lava surface. It should be solid rock. But depending on how bright that rock is, it could be recently resurfaced due to plate tectonics or volcanic activity, or it could be a planet that’s been eroded by space weathering and has a much darker surface. Going forward, we should be able to distinguish between some interesting scenarios for the surface of the planet.” 

Advantages of the unique exoplanet

This lack of atmosphere might seem like a disappointment, but it actually presents a unique opportunity. Without an atmosphere to obscure our view, scientists believe that we may be able to study the planet’s surface in unprecedented detail.

This unique environment on SPECULOOS-3b offers scientists a rare opportunity to study a planet’s surface without atmospheric interference.

“SPECULOOS-3b is the first planet for which we can consider moving toward constraining surface properties of planets beyond the solar system,” said de Wit. “With this world, we could basically start doing exoplanetary geology. How cool is that?” 

“The fact that this planet has no atmosphere could be a plus in several respects. For example, it could enable us to learn a great deal about ultra-cool dwarf stars, which in turn will make possible more in-depth studies of their potentially habitable planets.”

Future research on Earth-sized exoplanet

The upcoming launch of the James Webb Space Telescope (JWST) is set to revolutionize our understanding of exoplanets. This powerful telescope will be able to analyze the light from distant worlds, revealing details about their atmospheres and surfaces.

Researchers are particularly excited about the potential of JWST to study SPECULOOS-3b. “With the JWST, we could even study the mineralogy of the planet’s surface!” said Elsa Ducrot, a researcher at the Paris Observatory.

The discovery of SPECULOOS-3b is a testament to the ingenuity and dedication of astronomers around the world. By developing specialized telescopes and innovative techniques, they are opening our eyes to the incredible diversity of planets that exist beyond our solar system.

As the SPECULOOS project continues to scan the skies, and the James Webb Space Telescope begins its mission, we can look forward to even more exciting discoveries in the years to come.

The study is published in the journal Nature Astronomy.


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