第1个回答 2024-06-01
NASA's confirmation of over 5,000 exoplanets marks a cosmic milestone
What do exoplanets, or planets outside our solar system, look like? This image shows a variety of exoplanets. Scientists discovered the first exoplanet in the 1990s. NASA has just confirmed a new planet, bringing the total to over 5,000 exoplanets, and this number is still growing.
Over 5,000 Exoplanets
Until recently, humanity only knew a few planets, all orbiting the Sun. However, numerous new discoveries have made scientific exploration reach new heights: On March 21, 2022, scientists confirmed that there are over 5,000 planets in our solar system.
The planetary milestone was reached on March 21st as the latest batch of 65 exoplanets—planets outside our solar family—were added to NASA's Exoplanet Archive. This archive records the discoveries of exoplanets from scientific papers that have undergone peer review and have been confirmed using various exploration methods or analysis techniques.
The more than 5,000 planets discovered so far include small rocky worlds similar to Earth, gas giants much larger than Jupiter, and hot Jupiters orbiting other stars. There are super-Earths, which may be larger than our own rocky world, and mini-Neptunes, smaller versions of the planet Neptune in our solar system. Not to mention the synchronous planets orbiting two stars and the collapsed remnants of dead stars.
Astronomers have discovered over 5,000 exoplanets, or planets outside our solar system. This is just a fraction of the hundreds of potentially discoverable exoplanets in our Milky Way galaxy. The discovery of exoplanets is like the spokes of a wheel radiating out from Earth. More discoveries await us.
The World of Numbers: Over 5,000 Exoplanets and the Unknown
Jessie Christiansen, a research scientist at the California Institute of Technology's NASA Exoplanet Research Institute, who is in charge of the science at the archive, says, "This isn't just a number. Each one is a new world, a whole new world. We're excited because we don't know much about them."
We do know this: Our Milky Way galaxy appears to encompass millions of planets. In 1992, the discovery of a new world orbiting a strange pulsar, a rapidly rotating neutron star emitting millisecond-scale bursts of radiation, opened the doors to exploration. The discovery of three planets orbiting this spinning pulsar hinted at the prevalence of planets.
The author of the paper, which was published three decades ago, announced the first confirmed exoplanet. "If you can find a planet orbiting between a neutron star, you have to wonder if planets are almost everywhere," said Wolszczan, a professor of exoplanet research at Pennsylvania State University. He added that we have entered a new era that is no longer just about adding newly discovered planets to the list. Launched in 2018, TESS, the Transiting Exoplanet Survey Satellite, continues to explore new exoplanets. However, soon after, the next-generation James Webb Space Telescope will be launched, which will capture light emitted from exoplanet systems and identify potential signs of habitability.
More Telescopes Searching
The Nancy Grace Roman Space Telescope, scheduled to launch in 2027, will use various new methods to observe exoplanets. The European Space Agency's ARIEL, scheduled to launch in 2029, will complete the task of observing the atmospheres of exoplanets. NASA's CASE international technology will also help us observe exoplanetary nebulae.
Wolszczan said, "I think we might eventually find some form of life somewhere, it's inevitable." He added that the chemical composition of life on Earth is closely related to certain chemicals found in the universe, and the detection of some widespread organic molecules indicates that finding other life is just a matter of time.
In this video, the exoplanets discovered over the past decade and a half are represented by musical notes. The size and position of the circles represent the orbit and size of the planet, while the color represents different detection methods. Low notes represent long orbits, while high notes represent short-period orbits.
How to Find Other Worlds?
The view is not always so bright. In 1995, the first planet orbiting a solar-like star was confirmed to be a hot Jupiter: a gas giant with about half the mass of Jupiter, with an orbital period of only four days, or one "year" every four days. Since astronomers learned to identify such planets, more and more have been recorded in ground-based telescope data: first dozens, then hundreds. They were discovered using the "transit" method: tracking the slight back-and-forth movement of a star caused by the gravitational pull of an orbiting planet. However, no signs of habitable conditions have been found on these planets.
Finding Earth-like small rocky worlds requires a significant leap in exoplanet search technology called the transit method. Astronomer William Borucki had an idea: connect a highly sensitive light detector to a telescope and then launch it into space. This telescope would gaze at over 170,000 planets for years, looking for the slight decrease in light when a planet passes in front of its star.
This idea was realized with the launch of the Kepler Space Telescope.
Retired Kepler mission principal investigator Borucki said that the launch of the Kepler Space Telescope in 2009 opened a new window on the universe for us.
He said, "I have a real sense of satisfaction and awe for everything in the universe. We didn't expect such a variety of planetary systems and stars. It's amazing!"
5000 Exoplanets: An Infographic
So far, over 5,000 confirmed exoplanets in the Milky Way galaxy include various types of planets: some resemble the planets in our solar system, while most are quite different. Among them are super-Earths, which are larger and more rocky than Earth. The image is from NASA/JPL-Caltech.
Finally, NASA/JPL announced on March 21, 2022, that the number of confirmed exoplanets had just passed 5,000, marking a 30-year journey of exploration.
BY: EarthSky Voices
FY: Astronomical volunteer team
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