TESS Finds its First Rogue Planet

This illustration shows a rogue planet traveling through space. Credit: NASA/JPL-Caltech/R. Hurt (Caltech-IPAC)

Well over 5,000 planets have been found orbiting other star systems. One of the satellites hunting for them is TESS, the Transiting Exoplanet Survey Satellite. Astronomers using TESS think they are made a rather surprising discovery; their first free-floating – or rogue – planet. The planet was discovered using gravitational microlensing where the planet passed in front of a star, distorting its light and revealing its presence.

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TESS Finds Eight More Super-Earths

This artist’s impression shows a Super-Earth orbiting a Sun-like star. Super-Earths are more massive than Earth yet lighter than ice giants like Neptune and Uranus, and can be made of gas, rock or a combination of both. They are between twice the size of Earth and up to 10 times its mass. Image Credit: ESO

NASA’s Kepler spacecraft has discovered most of the confirmed exoplanets that we know of. But its successor, TESS (Transiting Exoplanet Survey Satellite), is catching up. New research announces the validation of eight more TESS candidates, and they’re all Super-Earths.

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TESS Reaches Fifth Anniversary of Extraordinary Mission, but its Work is Far from Over

Artist illustration of NASA’s Transiting Exoplanet Survey Satellite (TESS) observing the heavens. (Credit: NASA's Goddard Space Flight Center)

NASA’s TESS (Transiting Exoplanet Survey Satellite) mission recently reached its fifth anniversary of service to humanity as it continues to tirelessly scan the heavens for worlds beyond. Dubbed as an all-sky mission, TESS was launched on April 18, 2018, aboard a SpaceX Falcon rocket. During its five years in space, TESS’s four 24 degrees by 24 degrees field-of-view CCD cameras have successfully mapped greater than 93% of the cosmos.

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The Planet That Shouldn’t Exist

Artist illustration of TOI-5205b orbiting its parent star. (Artwork Credit: Katherine Cain/Carnegie Institution for Science)

As of this writing, almost 5300 exoplanets spanning approximately 4000 planetary systems have been confirmed to exist in our universe. With each new exoplanet discovery, scientists continue to learn more about planetary formation and evolution that has already shaken our understanding of this process down to its very core. One such example is “Hot Jupiters”, which are Jupiter-sized exoplanets, or larger, that orbit closer to their parents stars than Mercury does to our own. This is in stark contrast to our own Solar System, which has rocky planets closer towards our Sun and the gas giant planets much farther out.

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It's Confirmed. We now Know of More Than 5,000 Exoplanets

An artist view of countless exoplanets. Credit: NASA/JPL-Caltech

This week the official count of known exoplanets crossed 5,000. On the one hand, there isn’t anything special about 5,000 vs 4,900 or 5,100, but on the other hand, crossing this threshold is an indication of how far we’ve come, and how quickly things will change in the future.

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Forget That Planet That Orbits Every 16 Hours. That’s so Last Week. Now Astronomers Have Found a Metal Planet That Orbits its Star EVERY 8 HOURS

Artist view of a hot planet orbiting a red dwarf star. Credit: Patricia Klein

Most exoplanets are found using a technique known as the transit method, where the exoplanet passes in front of its star, causing the star to dim slightly. It takes several transits to confirm an exoplanet, so it’s not surprising that most known exoplanets have a fairly short orbital period. Months or days rather than years. There’s also an observational bias in that most known stars are red dwarfs, so it’s usually not surprising that we’ve found yet another exoplanet closely orbiting a red dwarf star. But sometimes what we find is so extreme, it really is surprising.

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Astronomers Look at Super-Earths That had Their Atmospheres Stripped Away by Their Stars

Figure 1: Artist’s conceptual image showing the sizes of the planets observed in this study. The radius of TOI-1634 is 1.5 times larger than Earth’s radius and TOI-1685 is 1.8 times larger. The planets would appear red, due to the light from the red dwarf stars they orbit. (Credit: Astrobiology Center, NINS)

As the planets of our Solar System demonstrate, understanding the solar dynamics of a system is a crucial aspect of determining habitability. Because of its protective magnetic field, Earth has maintained a fluffy atmosphere for billions of years, ensuring a stable climate for life to evolve. In contrast, other rocky planets that orbit our Sun are either airless, have super-dense (Venus), or have very thin atmospheres (Mars) due to their interactions with the Sun.

In recent years, astronomers have been on the lookout for this same process when studying extrasolar planets. For instance, an international team of astronomers led by the National Astronomical Observatory of Japan (NAOJ) recently conducted follow-up observations of two Super-Earths that orbit very closely to their respective stars. These planets, which have no thick primordial atmospheres, represent a chance to investigate the evolution of atmospheres on hot rocky planets.

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Larger Rocky Planets Might be Rare Because They Shrunk

Researchers at the Flatiron Institute’s Center for Computational Astrophysics published a paper last week that just might explain a mysterious gap in planet sizes beyond our solar system. Planets between 1.5 and 2 times Earth’s radius are strikingly rare. This new research suggests that the reason might be because planets slightly larger than this, called mini-Neptunes, lose their atmospheres over time, shrinking to become ‘super-Earths’ only slightly larger than our home planet. These changing planets only briefly have a radius the right size to fill the gap, quickly shrinking beyond it. The implication for planetary science is exciting, as it affirms that planets are not static objects, but evolving and dynamic worlds.

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What Are Extrasolar Planets?

An exoplanet about ten times Jupiter's mass located some 330 light years from Earth. X-ray: NASA/CXC/SAO/I.Pillitteri et al; Optical: DSS; Illustration: NASA/CXC/M.Weiss

For countless generations, human beings have looked out at the night sky and wondered if they were alone in the Universe. With the discovery of other planets in our Solar System, the true extent of the Milky Way galaxy, and other galaxies beyond our own, this question has only deepened and become more profound.

And whereas astronomers and scientists have long suspected that other star systems in our galaxy and the Universe had orbiting planets of their own, it has only been within the last few decades that any have been observed. Over time, the methods for detecting these “extrasolar planets” have improved, and the list of those whose existence has been confirmed has grown accordingly (over 4000 and counting!)

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One of the Oldest Stars in the Galaxy has a Planet. Rocky Planets Were Forming at Nearly the Beginning of the Universe

Artist's rendition of TOI-561, one of the oldest, most metal-poor planetary systems discovered yet in the Milky Way galaxy. This 10 billion-year-old system has a hot, rocky exoplanet (center) that's one and a half times the size of Earth as well as two gas planets (to the left of the rocky planet) that are about twice as large as Earth. Credit: W. M. Keck Observatory/Adam Makarenko

Would it be surprising to find a rocky planet that dates back to the very early Universe? It should be. The early Universe lacked the heavier elements necessary to form rocky planets.

But astronomers have found one, right here in the Milky Way.

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