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NASA confirms 5,000 exoplanets, a cosmic milestone | Science and Technology

NASA confirms 5,000 exoplanets, a cosmic milestone | Science and Technology

Cosmic milestone: NASA confirms 5,000 exoplanets

The count of confirmed exoplanets has just passed the 5,000 mark, representing a 30-year journey of discovery led by NASA's space telescopes.

Not so long ago, we lived in a universe with very few known planets, all orbiting our Sun.  But a new raft of discoveries marks a scientific high point: More than 5,000 planets are now confirmed to exist beyond our solar system.

On March 21 the planetary odometer, along with the latest batch of 65 exoplanets—planets outside our immediate solar family—added to the NASA Exoplanet Archive.  The archive records exoplanet discoveries that appear in peer-reviewed, scientific papers, and which have been confirmed using multiple detection methods or analytical techniques.

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The more than 5,000 planets found so far include small, rocky worlds like Earth, gas giants many times larger than Jupiter, and "hot Jupiters" in scorchingly close orbits around their stars.  There are "super-Earths," which are potentially rocky worlds larger than our own, and "mini-Neptunes," smaller versions of our system's Neptune.  Combine planets orbiting two stars together and planets orbiting the collapsed remnants of dead stars stubbornly. 

"It's not just a number," said Jesse Christiansen, science chief for the collection and a research scientist at the NASA Exoplanet Science Institute at Caltech in Pasadena.  "Each of them is a new world, a new planet. I'm excited about each one because we know nothing about them."

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We do know this: there are likely hundreds of billions of such planets in our galaxy.  The steady drumbeat of discovery in 1992 began with strange new worlds orbiting a stranger star.  It was a type of neutron star known as a pulsar, a rapidly spinning stellar corpse that pulsates with bursts of radiation of milliseconds.  Measuring slight changes in the timing of the pulses allowed scientists to reveal planets in orbit around the pulsar.

Finding just three planets around this spinning star essentially opened the floodgates, said the paper's lead author, Alexander Wolzczyn, who — 30 years ago — unveiled the first planets to be confirmed outside our solar system.

"If you can find planets around a neutron star, then planets should be basically everywhere," Volczn said.  "The planetary production process has to be very robust."

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We're ushering in an era of discovery that will go beyond just adding new planets to the list, says Wolszczn, who still searches for exoplanets as a professor at Penn State.  The Transiting Exoplanet Survey Satellite (TESS), launched in 2018, continues new exoplanet discoveries.  But soon powerful next-generation telescopes and their highly sensitive instruments, starting with the recently launched James Webb Space Telescope, will capture light from exoplanets' atmospheres by reading which gases are likely to reveal signs of habitable conditions.  are available for identification.

The Nancy Grace Roman Space Telescope, expected to launch in 2027, will search for new exoplanets using a variety of methods.  ARIEL, an ESA (European Space Agency) mission to be launched in 2029, will observe exoplanet atmospheres;  A piece of NASA technology, called CASE, will help zero in on exoplanet clouds and haze.

"To my thinking, it's inevitable that we'll find some kind of life somewhere—most likely some primitive kind," said Volszczon.  The chemistry of life on Earth and found throughout the universe, as well as the widespread detection of organic molecules, suggests that detecting life is only a matter of time, he said.

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How to find another world

The picture didn't always look so bright.  The first planet found around a Sun-like star, in 1995, turned out to be a hot Jupiter: a gas giant about half the mass of our own Jupiter in an extremely close, four-day orbit around its star.  A year on this planet, in other words, lasts only four days.

Once astronomers learned to recognize them—first dozens, then hundreds.  They were found using the "wobble" method: tracking the light-wave motions of a star back and forth, caused by the gravity of the planets orbiting it.  But even then, nothing seemed likely to be habitable.

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Finding small, rocky worlds like ours requires the next big leap in exoplanet-hunting technology: the "transit" method.  Astronomer William Borucki came up with the idea of ​​connecting extremely sensitive light detectors to a telescope and then launching it into space.  The telescope will stare for years in a field of more than 170,000 stars, searching for tiny dips in starlight when a planet crosses the face of a star.

That idea was realized at the Kepler Space Telescope. 

Borucki, principal investigator of the now-retired Kepler mission, says its launch in 2009 opened a new window on the universe.

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"I get a real sense of satisfaction, and awe at what's really out there," he said.  "None of us expected this huge variety of planetary systems and stars. It's just amazing."

Source: Jet Propulsion Laboratory, Phys.org, Direct News 99