Planets Form in Just a Few Hundred Thousand Years

Artist's conceptualization of the dusty TYC 8241 2652 system as it might have appeared several years ago when it was emitting large amounts of excess infrared radiation. Credit: Gemini Observatory/AURA artwork by Lynette Cook. https://www.gemini.edu/node/11836

Astronomers like to observe young planets forming in circumstellar debris disks, the rotating rings of material around young stars. But when they measure the amount of material in those disks, they don’t contain enough material to form large planets. That discrepancy has puzzled astronomers.

The answer might come down to timing.

A new study suggests that planets form much quicker than astronomers think.

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Astronomers Estimate There Are 6 Billion Earth-Like Planets in the Milky Way

Meet Kepler-22b, an exoplanet with an Earth-like radius in the habitable zone of its host star. Unfortunately its mass remains unknown. Image Credit: NASA

Six billion Earth-like planets in the Milky Way? If true, that’s astounding. But the number needs some context.

The Milky Way has up 400 billion stars. So even if there are six billion Earth-like planets, they’re still spread far and wide throughout our vast galaxy.

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Newborn Exoplanets can be Completely Stripped of Their Atmosphere by Stars

Artist's conception of exoplanet systems that could be observed by PLAnetary Transits and Oscillations of stars (PLATO), a European Space Agency telescope. Credit: ESA - C. Carreau

Newborn exoplanets can have a tough life. They may form an atmosphere, but that atmosphere can be doomed. Their stars can emit intense X-ray and UV radiation, stripping away those atmospheres and laying their surfaces bare.

A team of researchers from the Leibniz Institute for Astrophysics looked at a family of four newborn sibling planets, and tried to understand how their star strips away their gaseous envelopes.

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Tiny Cubesat Detects an Exoplanet

Credit: NASA/JPL-Caltech

In the past decade and a half, a total of 4,164 thousand planets have been discovered beyond our Solar System, while another 5220 await confirmation. The majority of these were detected by the venerable Kepler Space Telescope, while the remainder have been observed by the Transitting Exoplanet Survey Satellite (TESS) and a combination of other satellites and ground-based telescopes.

But in what is a new record, a known super-Earth was recently observed by the Arcsecond Space Telescope Enabling Research in Astrophysics (ASTERIA) small satellite – making it the smallest observatory to spot an exoplanet. Led by a team from the Massachusetts Institute of Technology (MIT), this mission has demonstrated that small satellites can perform complex tasks in space normally carried out by large observatories.

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It Should Be Easiest to Search for Young Earth-like Planets When They’re Completely Covered in Magma

Artist's impression of magma ocean planet. Credit: Mark Garlick

How did Earth evolve from an ocean of magma to the vibrant, life-supporting, blue jewel it is now? In its early years, the Earth was a blistering hot ball of magma. Now, 4.5 billion years later, it’s barely recognizable.

Is it possible to find exoplanets out there in the vast expanse, which are young molten globes much like young Earth was? How many of them can we expect to find? Where will we find them?

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Is the Concept of a Habitable Zone Too Wide?

Planetary system comparison
This size and scale of the Kepler-452 system compared alongside our own solar system, plus another planetary system with a habitable-zone planet known as Kepler-186f. The Kepler-186 system has a faint red dwarf star and a planet whose orbit would fit inside the orbit of Mercury.

In our search for exoplanets, we have found more than three dozen potentially habitable worlds. It’s estimated that there are 8 to 20 billion potentially habitable, Earth-like worlds in our galaxy alone. But there is a big difference between potentially habitable and actually habitable, and scientists are starting to narrow their definitions.

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Extremely Hot Exoplanets Can Have Extreme Weather, Like Clouds of Aluminum Oxide and Titanium Rain

Thi illustration of a Hot Jupiter orbiting close to its star. Image Credit: ESA/ATG medialab, CC BY-SA 3.0 IGO

Thanks to the success of the Kepler mission, we know that there are multitudes of exoplanets of a type called “Hot Jupiters.” These are gas giants that orbit so close to their stars that they reach extremely high temperatures. They also have exotic atmospheres, and those atmospheres contain a lot of strangeness, like clouds made of aluminum oxide, and titanium rain.

A team of astronomers has created a cloud atlas for Hot Jupiters, detailing which type of clouds and atmospheres we’ll see when we observe different Hot Jupiters.

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What Are Some Clues to the Climates of Exoplanets?

Credit: Cornell Chronicle

In the past few decades, the number of planets discovered beyond our Solar System has grown exponentially. To date, a total of 4,158 exoplanets have been confirmed in 3,081 systems, with an additional 5,144 candidates awaiting confirmation. Thanks to the abundance of discoveries, astronomers have been transitioning in recent years from the process of discovery to the process of characterization.

In particular, astronomers are developing tools to assess which of these planets could harbor life. Recently, a team of astronomers from the Carl Sagan Institute (CSI) at Cornell University designed an environmental “decoder” based on the color of exoplanet surfaces and their hosts stars. In the future, this tool could be used by astronomers to determine which exoplanets are potentially-habitable and worthy of follow-up studies.

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This is an Actual Image of a Planet-Forming Disc in a Distant Star System

An image of AB Aurigae from the ESO's VLT and its SPHERE instrument, showing what scientists think is a baby planet forming. Image Credit: ESO/Boccaletti et al.

In 2017, astronomers used ALMA (Atacama Large Millimeter/sub-millimeter Array) to look at the star AB Aurigae. It’s a type of young star called a Herbig Ae star, and it’s less then 10 million years old. At that time, they found a dusty protoplanetary disk there, with tell-tale gaps indicating spiral arms.

Now they’ve taken another look, and found a very young planet forming there.

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Ocean Circulation Might Be the Key to Finding Habitable Exoplanets

Artist's depiction of a waterworld. A new study suggests that Earth is in a minority when it comes to planets, and that most habitable planets may be greater than 90% ocean. Credit: David A. Aguilar (CfA)
Artist's depiction of a waterworld. A new study suggests that Earth is in a minority when it comes to planets, and that most habitable planets may be greater than 90% ocean. Credit: David A. Aguilar (CfA)

We’ve found thousands and thousands of exoplanets now. And spacecraft like TESS will likely find thousands and thousands more of them. But most exoplanets are gassy giants, molten hell-holes, or frozen wastes. How can we find those needles-in-the-haystack habitable worlds that may be out there? How can we narrow our search?

Well, first of all, we need to find water. Oceans, preferably, since that’s where life began on Earth. And according to a new study, those oceans need to circulate in particular ways to support life.

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