Astronomers have been trying to find evidence that the world exists around stars outside our sun since the 19th century. By the mid-1990s, technology finally caught up with the desire for discovery and led to a planet orbiting another sun-like star, Pegasi 51b. Why does it take so long to discover these distant worlds, and what technologies do astronomers use to find them?
One of the most famous methods of detection of exoplanets is Transit methodused by Kepler and other observations. As the planet passes past its host star, the star's light dips slightly in brightness. Scientists can confirm the planets of their host planet by repeatedly detecting these incredible tiny inclinations using sensitive instruments. If you can imagine trying to detect inclination from a huge searchlight as an ants crossed distances dozens of miles away, you can start to see how difficult it is to find a planet from light years away! Another disadvantage of the transit method is that the distant solar system must be favorable to our viewpoint on Earth - if the distant system has a slightly skewed angle, there will be no transit. Even in our solar system, buses are rare. For example, in this century, we have seen Venus twice from Earth, which is visible in our sun twice. But the next time Venus sees the sun from Earth will be in 2117 - compared to the 2012 transportation, even if Venus will complete nearly 150 orbits around the sun by then, even if it is over a century!
The Doppler offset of the stellar spectrum was found to be used to find Pegasi 51b, the first planet to be detected around a sunny star. This technology is called Radial velocity or "swing" method. Astronomers split the visible light from a star into a rainbow. These spectra, as well as the gap between the normally smooth bands of light, help determine the elements that make up the stars. But if there is a planet orbiting a star, it causes the star to swing back and forth so slightly. This in turn will cause the lines in the spectrum to move slightly towards the blue and red ends of the spectrum as the stars sway slightly, tilting towards us. This is caused by the blue and red offset of the star light. By carefully measuring the amount of variation in the stellar spectrum, astronomers can determine the size of the object pulled on the host star and that the companion is indeed a planet. By tracking changes in this periodic change in the spectrum, they can also determine the time a planet orbits its parent star.
Finally, it can be passed Direct imaging They, for example, images of these four planets, found orbiting the star HR 8799! The use of space telescope is called Coronary artery Cover the bright light of the host star and capture dim light from the planet. The Hubble Space Telescope captures images of giant planets from several nearby systems, while the James Webb Space Telescope improves these observations only by discovering more details, such as the color and spectrum of external atmospheres, such as temperature, temperature, detecting potential exomoons, and even scanning for potential biological atmospheres!
You can find more information and activities on NASA's Exoplanet page, such as the Eyes, Surgical Planets and some of the latest Exoplanet news. Finally, you can find more resources in our News & Resources section, including a clever demonstration about how astronomers use the Wobble method to detect planets!
The future of exoplanet discovery has just begun, which promises to be in human understanding of where we are in the universe, where we come from, and where we live elsewhere in our universe.
Originally published by Dave Prosper: July 2015
Last updated by Kat Troche: April 2025