- 3332 GAIA - exoplanets are discovered. The first exoplanets were discovered in the 1990s and since then astronomers have identified thousands using a variety of detection methods. This ever-rising exoplanet tally comes from only a small sampling of the whole Galaxy, and will certainly increase as new telescopes and observatories come online.
--------------------------- Stars, how many have planets like ours?
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-------------------- 3332 - GAIA - exoplanets are discovered.
- GAIA is a global space astrometry mission. It will make the largest, most precise three-dimensional map of our Galaxy by surveying more than a thousand million stars.
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- Gaia will monitor each of its target stars about 70 times over a five-year period. It will precisely chart their positions, distances, movements, and changes in brightness.
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- It is expected to discover hundreds of thousands of new celestial objects, such as extra-solar planets and brown dwarfs, and observe hundreds of thousands of asteroids within our own Solar System. The mission will also study about 500 000 distant quasars and will provide stringent new tests of Albert Einstein’s General Theory of Relativity.
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- Gaia will create an extraordinarily precise three-dimensional map of more than a thousand million stars throughout our Galaxy and beyond, mapping their motions, luminosity, temperature and composition. This huge stellar census will provide the data needed to tackle an enormous range of important problems related to the origin, structure and evolutionary history of our Galaxy.
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- Gaia will identify which stars are relics from smaller galaxies long ago ‘swallowed’ by the Milky Way. By watching for the large-scale motion of stars in our Galaxy, it will also probe the distribution of dark matter, the invisible substance thought to hold our Galaxy together.
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- Gaia will be measuring the positions of all objects down to magnitude 20
, about 400,000 times fainter than can be seen with the naked eye).
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- For all objects brighter than magnitude 15 (4,000 times fainter than the naked eye limit), Gaia will measure their positions to an accuracy of 24 micro-arcseconds. This is comparable to measuring the diameter of a human hair at a distance of 1,000 kilometers.
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- It will allow the nearest stars to have their distances measured to the extraordinary accuracy of 0.001%. Even stars near the Galactic center, some 30,000 light-years away, will have their distances measured to within an accuracy of 20%.
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- The vast catalogue of celestial objects will not only benefit studies of our own Solar System and Galaxy, but also the fundamental physics that underpins our entire Universe.
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- Gaia contains two optical telescopes that work with three science instruments to precisely determine the location of stars and their velocities, and to split their light into a spectrum for analysis.
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- During its five-year mission, the spacecraft spins slowly, sweeping the two telescopes across the entire celestial sphere. As the detectors repeatedly measure the position of each celestial object, they will detect any changes in the object’s motion through space.
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- Gaia unfolded a ‘skirt’ just over 10 meters in diameter. This acts as both a sunshade to permanently shade the telescopes and allow temperatures to drop to below –100°C, and as a power generator for the spacecraft. The underside of the shield is partially covered with solar panels and will always be facing the Sun, generating electricity to operate the spacecraft and its instruments.
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- Gaia is mapping the stars from an orbit around the Sun, at a distance of 1,500,000 kilometers beyond Earth’s orbit. This special location, known as the “L2 Lagrangian” point, keeps pace with Earth as we orbit the Sun.
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- The L2 Lagrangian point offers a clearer view of the cosmos than an orbit around Earth, which would result in the spacecraft passing in and out of Earth's shadow and causing it to heat up and cool down, distorting its view. Free from this restriction and far away from the heat radiated by Earth, L2 provides a much more stable viewpoint.
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- The ESA’s Hipparcos mission (1989-1993) catalogued more than 100,000 stars to high precision, and more than a million to lesser precision. Now, some 20 years later, Gaia will launch on its mission to catalogue a thousand million stars, measuring each star's position and motion 200 times more accurately than Hipparcos, and producing 10,000 times more data than its predecessor.
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- Most of the exoplanets discovered so far are in a relatively small region of our Milky Way galaxy. By measuring the size and mass of exoplanets, scientist can determine their compositions.
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- These range from very rocky (like Earth and Venus) to very gas-rich (like Jupiter and Saturn). Exoplanets are made up of elements similar to those of the planets in our Solar System, but the mixtures of those elements may differ.
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- Some planets may be dominated by water or ice, while others are dominated by iron or carbon. Astronomers have identified lava worlds covered in molten seas, puffy planets the density lighter than Styrofoam, and dense cores of planets still orbiting their stars.
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- To date, most exoplanets have been found through indirect methods: measuring the dimming of a star that happens to have a planet pass in front of it (called a “transit”), or monitoring the light of a star for minute Doppler shift variations caused by the tug of planet.
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- When scientists are able to use multiple methods together, they can learn the vital statistics of whole planetary systems without ever directly imaging the planets themselves. The best example so far is the TRAPPIST-1 system about 40 light-years away, where seven roughly Earth-sized planets orbit a small, red star.
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- The TRAPPIST-1 planets have been examined with ground and space telescopes. The space-based studies revealed not only their diameters, but the subtle gravitational influence these seven closely packed planets have upon each other; from this, scientists determined each planet’s mass.
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- By combining this information with how much energy the host star the energy, scientists were able to estimate the temperatures on these seven planets’ surfaces. They can even make reasonable estimates of the light level and guess at the color of the sky, if someone were standing on one of them.
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- While much remains unknown about these seven worlds, including whether they possess atmospheres or oceans, ice sheets or glaciers, it’s become the best-known Solar System apart from our own.
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- November 7, 2021 GAIA - exoplanets are discovered. 3332
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