(ORDO NEWS) — In January 1992, two space objects changed our galaxy forever.
For the first time, we have concrete evidence for the existence of extrasolar planets, or exoplanets orbiting an alien star: two rocky worlds orbiting a star 2,300 light-years away.
Now, just over 30 years later, that number has risen. This week, on March 21, an extremely important milestone was marked – more than 5,000 exoplanets have been confirmed. To be precise, NASA’s Exoplanet Archive now has 5,005 exoplanets, each with its own unique characteristics.
Each of these exoplanets has been published in peer-reviewed studies and has been observed using multiple detection methods or analysis methods.
It’s a rich choice for later exploring these worlds with new instruments such as the recently launched James Webb Space Telescope and the upcoming Nancy Grace Roman Space Telescope.
“It’s not just a number,” says astronomer Jesse Christiansen of NASA’s Exoplanet Science Institute at Caltech. “Each of them is a new world, a completely new planet. I rejoice in each of them, because we do not know anything about them.”
The first two confirmed worlds, discovered by astronomers Alexander Volschan and Dale Freil, were exoplanets with masses 4.3 and 3.9 times the mass of the Earth, orbiting a dead star known as a millisecond pulsar that sends out “bangs” or pulses of radio waves in milliseconds. time scale.
A third, much smaller exoplanet, with a mass 0.02 times that of Earth, was discovered orbiting a star named Leach in 1994. The exoplanets were named Poltergeist, Phoebetor and Draugr respectively.
This discovery suggested that the galaxy must have been teeming with these creatures. Pulsars are a type of neutron star: the dead cores of massive stars that have ejected most of their mass and then collapsed under their own gravity. The process of their formation is quite extreme and is often accompanied by colossal explosions.
“If you can find planets around a neutron star, then planets should be pretty much everywhere,” Wolschan says. “The process of planet formation must be very reliable.”
But there is one catch. The technique used to identify these exoplanets was based on the very regular timing of pulses from the star, which vary very little under the gravitational influence of the orbiting bodies.
Alas, this technique is limited to pulsars; it is not suitable for main sequence stars that do not have regular millisecond pulsations.
However, when NASA astronomer William Boruki pioneered the transit method, which allows you to observe faint, regular dips in starlight as an exoplanet passes between us and a host star, exoplanet science exploded.
The Kepler space telescope, launched in 2009, has more than 3,000 confirmed exoplanets on the list, with 3,000 more candidates waiting in the wings.
In addition to the transit method, astronomers can study the gravitational effects of exoplanets on host stars. When objects orbit around their mutual center of gravity, the star “wobbles” slightly in place, changing the wavelengths of its light.
Also, if you know the mass of the star, you can study how much it fluctuates to infer the exoplanet’s mass; and if you know how bright a star is by nature, you can infer the size of an exoplanet.
This is how we know that there are exoplanets in the universe that are very, very different from those in our own system.
Hot Jupiters are huge gas giants in incredibly close orbits around their stars, the closeness of which means that exoplanet temperatures can be even hotter than some stars.
Mini-Neptunes rank between Earth and Neptune in size and mass and could potentially be habitable. There are also super-Earths, rocky like the Earth, but with a mass several times greater.
Because studying exoplanets directly is very difficult—they are small, very dim, very distant, and often very close to a bright star whose light drowns out anything an exoplanet can reflect—there is still a lot we don’t know. In addition, there are many more worlds beyond our current detection thresholds.
But in the coming years, these thresholds will recede in the face of advances in technology and new methods of analysis, and we may find many worlds beyond our wildest dreams. We may even find traces of life outside the solar system.
“I have a real sense of satisfaction and awe of what’s out there,” says Boruki.
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