Cosmic milestone: NASA confirms 5,000 exoplanets | Weather Blog


Article published with the kind permission of NASA

What do the planets outside our solar system, or exoplanets, look like? A variety of possibilities are shown in this illustration. Scientists discovered the first exoplanets in the 1990s. By 2022, the count rises to just over 5,000 confirmed exoplanets.

Credits: NASA/JPL-Caltech

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

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

The planetary odometer turned on March 21, with the final batch of 65 exoplanets — planets outside our immediate solar family — added to NASA’s exoplanet archive. The archive records discoveries of exoplanets that appear in peer-reviewed scientific papers and that have been confirmed using multiple detection methods or by analytical techniques.

The more than 5,000 planets discovered so far include small rocky worlds like Earth, gas giants several times larger than Jupiter, and “hot Jupiters” in extremely close orbits around their stars. There are “super-Earths”, which are rocky worlds larger than our own, and “mini-Neptunes”, smaller versions of Neptune in our system. Add to the mix planets orbiting two stars at once and planets stubbornly orbiting the collapsed remnants of dead stars.

“It’s not just a number,” said Jessie Christiansen, archival scientist and researcher at the NASA Exoplanet Science Institute at Caltech in Pasadena. “Each of them is a new world, a whole new planet. I’m excited about each one because we don’t know anything about them.

We know this: our galaxy probably contains hundreds of billions of these planets. The steady drumbeat of discovery began in 1992 with strange new worlds orbiting an even stranger star. It was a type of neutron star known as a pulsar, a rapidly rotating stellar corpse that pulsates with millisecond bursts of searing radiation. Measuring slight changes in the timing of the pulses allowed scientists to reveal planets orbiting the pulsar.

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

“If you can find planets around a neutron star, the planets must be pretty much everywhere,” Wolszczan said. “The planet’s production process must be very robust.”

Wolszczan, who is still researching exoplanets as a professor at Penn State, says we’re ushering in an era of discovery that will go beyond just adding new planets to the list. The Transiting Exoplanet Survey Satellite (TESS), launched in 2018, continues to make new exoplanet discoveries. But soon, powerful next-generation telescopes and their highly sensitive instruments, starting with the recently launched James Webb Space Telescope, will be picking up light from exoplanet atmospheres, reading what gases are present to potentially identify telltale signs of habitable conditions.

The Nancy Grace Roman Space Telescope, slated for launch in 2027, will make new discoveries of exoplanets using a variety of methods. The ESA (European Space Agency) ARIEL mission, launched in 2029, will observe the atmospheres of exoplanets; onboard NASA technology called CASE will help focus on exoplanetary clouds and haze.

“In my view, it’s inevitable that we’ll find some kind of life somewhere – most likely of a primitive kind,” Wolszczan said. The close connection between the chemistry of life on Earth and the chemistry found throughout the universe, as well as the detection of widespread organic molecules, suggests that the detection of life itself is only a matter of time, he added.

How to find other worlds

The picture doesn’t always look so bright. The first planet detected 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 his star. In other words, a year on this planet lasts only four days.

More such planets appeared in data from ground-based telescopes once astronomers learned to recognize them – first dozens, then hundreds. They were found using the “wobble” method: tracking slight back-and-forth motions of a star, caused by gravitational tugs from orbiting planets. But still, nothing seemed likely to be habitable.

Finding small, rocky worlds more like our own required the next big step forward in exoplanet-hunting technology: the “transit” method. Astronomer William Borucki came up with the idea of ​​attaching extremely sensitive light detectors to a telescope and then launching it into space. The telescope would stare for years at a field of more than 170,000 stars, looking for tiny dips in starlight when a planet crossed a star’s face.

This idea was realized in the Kepler space telescope.

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

“I feel a real sense of satisfaction and really awe of what’s happening,” he said. “None of us expected this huge variety of planetary systems and stars. It’s just amazing.

Exoplanet infographic

The more than 5,000 exoplanets confirmed in our galaxy so far include a variety of types – some that are similar to planets in our solar system, others quite different. Among these are a mysterious variety known as “super-Earths” because they are larger than our world and possibly rocky.

Credits: NASA/JPL-Caltech


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