Planets are Finally Being Discovered Orbiting Farther From Their Stars

Discovering exoplanets is a difficult job. Given the challenges, it’s amazing that we’ve found any at all. But astronomers are clever, so there are currently more than 4,300 confirmed exoplanets. They range from small Mercury-sized worlds to planets larger than Jupiter, but most of them have one thing in common: they orbit close to their home star.

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Stellar Flares May Not Condemn a Planet’s Habitability

Red dwarf stars are the most common kind of star in our neighbourhood, and probably in the Milky Way. Because of that, many of the Earth-like and potentially life-supporting exoplanets we’ve detected are in orbit around red dwarfs. The problem is that red dwarfs can exhibit intense flaring behaviour, much more energetic than our relatively placid Sun.

So what does that mean for the potential of those exoplanets to actually support life?

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Radio Emissions Have Been Detected from an Exoplanet

Invisible Glow

Finding planets out in the Universe is pretty hard. I say this despite the fact that two planets in Earth’s skies are aligning tomorrow to form one of the brightest objects seen in hundreds of years. But while the brilliant Jupiter and Saturn are always visible to the naked eye, Neptune wasn’t directly observed until 1846 despite being in our own solar system. We didn’t start discovering planets outside the solar system until 150 years after Neptune. Like Neptune, we find them (though indirectly), through visible light. However an international team of researchers may have just made the first detection of an exoplanet through radio emissions created by the planet’s aurora.

A simulation of Gas giant “Hot Jupiter” Tau Boötis Ab which orbits its parent star at one seventh the distance Mercury orbits our Sun. It’s atmosphere and the corona of its star are possibly touching eachother. – c SpaceEngine Pro by Author
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Heard of Mini-Neptunes and gas-Dwarfs? Here's a new one: sub-Earths

The planets in our solar system are broadly divided into two groups: small, rocky worlds like Earth, and large gas giants. Before the discovery of exoplanets, it was thought that our solar system was very typical. The light and heat of a star push the gas to the outer solar system, while heavier dust remains closer to the star. Thus a solar system has close rocky planets and distant gas giants. But we now know that planets and star systems have much more diversity.

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There are Planets So Close to Their Stars That They Have Magma Oceans 100km Deep and Winds that Go 8000 km/h

200 light years away, “super earth” exoplanet K2-141b orbits a star so closely that its “year” is only 7 hours long. Not its day…its YEAR! K2-141b orbits a mere million kilometers from the fiery surface of its star. Earth is 150 million km from our Sun. Even Mercury, the planet closest to our Sun, is never less than 47 million km. Standing on the surface of K2-141b you’d look up at an orange star that filled fifty degrees of the sky appearing a hundred times wider than our Sun appears in Earth’s sky. It would be a giant blazing orb so bright that its light shines two thirds of the way around the entire planet unlike Earth’s two day/night halves. Of course, the surface you’re standing on wouldn’t be much of a surface at all – it would be an ocean of liquid hot magma.

Artist’s impression of a close orbiting exoplanet around a star. c. ESO
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Even older red dwarf stars are pumping out a surprising amount of deadly radiation at their planets

Most of the potentially habitable exoplanets we’ve discovered orbit small red dwarf stars. Red dwarfs make up about 75% of the stars in our galaxy. Only about 7.5% of stars are g-type like our Sun. As we look for life on other worlds, red dwarfs would seem to be their most likely home. But red dwarfs pose a serious problem for habitable worlds.

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The Youngest Stellar Disk Ever Seen, Just 500,000 Years Old

Unless you’re reading this in an aircraft or the International Space Station, then you’re currently residing on the surface of a planet. You’re here because the planet is here. But how did the planet get here? Like a rolling snowball picking up more snow, planets form from loose dust and gas surrounding young stars. As the planets orbit, their gravity draws in more of the lose material and they grow in mass. We’re not certain when the process of planet formation begins in orbit of new stars, but we have incredible new insights from one of the youngest solar systems ever observed called IRS 63.

The Rho Ophiuchi cloud complex is a nebula of gas and dust that is located in the constellation Ophiuchus. It is one of the closest star-forming regions to the Solar System and where the young star system IRS 63 was observed

Primordial Soup

Swirling in orbit of young stars (or protostars) are massive disks of dust and gas called circumstellar disks. These disks are dense enough to be opaque hiding young solar systems from visible light. However, energy emanating from the protostar heats the dust which then glows in infrared radiation which more easily penetrates obstructions than wavelengths of visible light. In fact, the degree to which a newly forming star system is observed in either visible or infrared light determines its classification. Class 0 protostars are completely enshrouded and can only be observed in submillimeter wavelengths corresponding to far-infrared and microwave light. Class I protostars, are observable in the far-infrared, Class II in near-infrared/red, and finally a Class III protostar’s surface and solar system can be observed in visible light as the remaining dust and gas is either blown away by the increasing energy of the star AND/OR has formed into PLANETS! That’s where we came from. That leftover material orbiting newly forming stars is what accumulates to form US. The whole process from Class 0 to Class III, when the solar system leaves its cocoon of dust and joins the galaxy, is about 10 million years. But at what stage does planet formation begin? The youngest circumstellar disks we’d observed are a million years old and had shown evidence that planetary formation had already begun. The recently observed IRS 63 is less than 500,000 years old – Class I – and shows signs of possible planet formation. The excitement? We were surprised to see evidence of planetary formation so early in the life of a solar system.

IRS 63 Circumstellar Disk C. ALMA/ Segura-Cox et al. 2020
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The Color of Habitable Worlds

“This is where we live. On a Blue Dot.” said Carl Sagan when the now famous Pale Blue Dot photo was released. Captured February 14, 1990 by the Voyager 1 Space Probe, Pale Blue Dot remains the most distant photograph of the Earth ever taken at 6 billion kilometers. This past February marked the 30th anniversary of Pale Blue Dot which was reprocessed using modern digital photo techniques creating an even more remarkable image.

This updated version of the iconic “Pale Blue Dot” image taken by the Voyager 1 spacecraft uses modern image-processing software and techniques to revisit the well-known Voyager view while attempting to respect the original data and intent of those who planned the images. Credit: NASA/JPL-Caltech

Whether Pale Blue Dot, or Blue Marble, our planet is associated with the color blue. As Earth is the only inhabited world we know of, it might stand to reason that other habitable planets in space will also be blue. But it’s a little more complicated than that.

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We use the Transit Method to Find other Planets. Which Extraterrestrial Civilizations Could use the Transit Method to Find Earth?

We have discovered more than 4,000 planets orbiting distant stars. They are a diverse group, from hot Jupiters that orbit red dwarf stars in a few days to rocky Earth-like worlds that orbit Sun-like stars. With spacecraft such as Gaia and TESS, that number will rise quickly, perhaps someday leading to the discovery of a world where intelligent life might thrive. But if we can discover alien worlds, life on other planets could find us. Not every nearby star would have a good view of our world, but some of them would. New work in the Monthly Notices of the Royal Astronomical Society tries to determine which ones.

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An Exoplanet So Hot There Are 7 Different Kinds of Gaseous Metals in its Atmosphere

The search for exoplanets has revealed types of planets that are nothing like the worlds in our own Solar System. One such type is the hot-Jupiter. They’re gas giants like Jupiter that orbit their host star very closely. That proximity raises their temperatures to extreme heights.

Hot-Jupiters can be hot enough to vaporize metals, making their atmospheres un-Earthlike. A team of astronomers examining one exoplanet has found 7 different gaseous metals in its atmosphere.

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