Extraordinary NASA Animation Shows Time Lapse of Exoplanet Discovery Over Last 28 Years

NASA has released a time lapse video showing the discovery of exoplanets—planets beyond our solar system—since the first in 1992.

The animation, from the space agency's Exoplanet Archive, was picked as NASA's Astronomy Picture of the Day. It shows the entire night sky compressed with the central band of the Milky Way making a U shape. Starting in 1991, the video is initially devoid of any exoplanets. However, as the years move forward, the number of known planets starts to increase.

At first, the rate of exoplanet discovery was slow. In 2000, just 32 had been confirmed by scientists. But numbers started to increase dramatically after 2009, when NASA launched the Kepler space telescope—a craft designed to search for alien planets in our part of the Milky Way.

A decade later, over 4,000 exoplanets have been discovered.

In the video, rings appear to show the location of newly found exoplanets. "Exoplanets detected by slight jiggles in their parents-star's colors (radial velocity) appear in pink, while those detected by slight dips in their parent star's brightness (transit) are shown in purple," a statement from NASA said. "Further, those exoplanets imaged directly appear in orange, while those detected by gravitationally magnifying the light of a background star (microlensing) are shown in green."

Kepler was responsible for discovering about half of the exoplanets. However, the spacecraft was retired in October 2018. In its place, NASA launched the Transiting Exoplanet Survey Satellite (TESS). The aim of this mission is to survey 200,000 stars near the Sun in the search for exoplanets—especially those that could support life.

Over its two-year run, TESS is expected to find around 20,000 exoplanets, including 17,000 that are bigger than Neptune, and dozens that are the same size as Earth.

The very first exoplanets to be discovered were announced in 1992. Alex Wolszczan and Dale Frail announced they had found at least two planets orbiting the pulsar PSR1257 + 12—a rapidly rotating neutron star. Neutron stars are believed to form from the collapsed core of a massive star following a supernova explosion.

NASA estimates there are at least 100 billion stars in the Milky Way. How many planets the galaxy contains is not known, although a 2013 study by Caltech scientists suggested there could be over a billion. "It's a staggering number, if you think about it," Jonathan Swift, lead author of the paper, said in a statement at the time.

milky way
The Milky Way (left) and our neighboring galaxy Andromeda. NASA Goddard