Exoplanets are worlds just like our own that are revolving around a star. Here at The Optimist Daily, we’ve commonly reported on the discovery of new exoplanets, like the first time an exoplanet has been spotted outside our galaxy, or this peculiar planet with the shortest orbit around a star ever recorded at just 16 hours.

If you were to add them all up, can you guess how many of these planets scientists have discovered? NASA confirmed this number for us recently when a milestone of 5,000 exoplanets was reached. To be precise, 5,005 are now documented in the NASA Exoplanet Archive in over 30 years of planet hunting.

“It’s not just a number,” says Jessie Christiansen of the NASA Exoplanet Science Institute at Caltech. “Each one of them is a new world, a brand-new planet. I get excited about everyone because we don’t know anything about them.”

Each one of these exoplanets is unique with individual characteristics. Whether that be their mass, distance from their star, elements they are made up of, type of star they revolve around, and many more.

How do you spot an exoplanet?

As they are so far away, exoplanets are extremely hard to study. Scientists have to look to the stars they are revolving around to indirectly identify them.

January 1992 was the first time one of these celestial bodies was spotted for the first time, revolving around a star 2,300 light-years away. Researchers on Earth were able to pick up pulses from a dying star to detect exoplanet presence, as these signals were changing due to gravitational influence from the planets.

This technique restricted scientists to pick up planets only revolving around this type of star. Although, since then the methods in which exoplanets can be spotted have expanded far and wide, using dips in starlight, star “wobble,” mass of the star, and more.

Each potential planet is now confirmed using multiple detection tools to make sure the finding from light years away is what we think it is. For this reason, the newly launched James Webb Space Telescope has a variety of cameras and detectors fitted onboard.

In the future as new techniques are invented, our capability to spot and study exoplanets is highly likely to expand. Who knows, we might discover a world that goes against the laws of physics as we know them, or one which inhabits alien life. The future is bright and exciting.