, 2017, Jupiter's moon passed Europe in front of a background star – a rare event that was first captured by ground-based telescopes thanks to data from the ESA spacecraft Gaia.
So far, observatories could observe only two of Jupiter's other moons during such an event – Io and Ganymed.
Gaia has been active in space since the end of 2013. The mission's mission is to create a three-dimensional map of our galaxy and characterize the myriad stars that call the Milky Way home. So far, it has been extremely successful, revealing the locations and movements of over a billion stars.
When we know the exact locations of the stars we see in the sky, scientists can predict when different bodies will pass in the solar system in front of a background star from a certain point of view: an event known as star-covering.
Gaia is not unaware of such events – the spaceship helped astronomers uniquely observe Neptune's moon Triton passing in front of a distant star in 2017, revealing more about the atmosphere and properties of the moon.
Coverings are extremely valuable; They allow measurements of the properties of the foreground body (size, shape, position, etc.) and can reveal structures such as rings, jets, and atmospheres. Such measurements can be made from the ground – something that Bruno Morgado from the Brazilian National Observatory and LIneA, Brazil, and colleagues have exploited to explore Jupiter's Moon Europa.
"We used data from Gaia's first data release to predict that, from our point of view, South America would pass in front of a bright background star in March 2017 – and to predict the best observation this coverage," said Bruno, senior executive Researcher of a new publication that reported the results of the 2017 coverage. Gaia's first data release was in September 2016.
"This provided us with a wonderful opportunity to explore Europe, as the technique offers an accuracy comparable to that obtained from space probes."
The Gaia data showed that the event would be visible from a thick strip that runs from northwest to southeast through South America. Three observatories in Brazil and Chile were able to collect data – a total of eight sites tried, but many experienced poor weather conditions.
Consistent with earlier measurements, the observations refined the radius of Europe to 1561.2 km and thus accurately determined the position of Europe in space and in relation to its host planet, Jupiter, and characterized the shape of the moon. Europe is not exactly spherical, but rather an ellipsoid. The observations show that the moon measures 1562 km when measured in one direction (the so-called semi-major axis) and 1560.4 km when measured transverse to the other axis (the apparent & # 39; semi-minor & # 39; -axis).  Astronomers spy on Europe and block the distant star – thanks to Gaia ” title=”Upcoming stellar occultations by Jupiter’s four largest moons. Credit: ESA/Gaia/DPAC; Bruno Morgado (Brazilian National Observatory/LIneA, Brazil) et al. (2019)”/>
Coming star coverings through Jupiter's four largest moons. Credit: ESA / Gaia / DPAC; Bruno Morgado (Brazilian National Observatory / LIneA, Brazil) et al. (2019)
"It is likely that we can observe much more such coverages in Jupiter's moons in 2019 and 2020," adds Bruno. "Jupiter traverses a piece of sky with the galactic center in the background, which dramatically increases the likelihood of its moons passing in front of bright background stars, which would really help us determine their three-dimensional shapes and positions – not just for Jupiter's four largest moons, but even for smaller, irregularly shaped ones. "
With Gaia's second data release of April 2018, the scientists predict the data for further coverings of bright stars across Europe. Io, Ganymede and Callisto in the coming years and lead a total of 10 events to 2019 and 2021 on. Future events include star coverings from Europe (22 June 2020), Callisto (20 June 2020, 4 May 2021), Io (9 and 21 May 2020) September 2019, 2 April 2021) and Ganymede (25 April 2021).
Three of them have already taken place in 2019, two of them – star coverings through Europe (June 4) and Callisto (June 5) – were also observed by the researchers, and for which the data is still unanalysed.
The upcoming occultations will also be seen with 20 cm small amateur telescopes from different regions of the world. The favorable position of Jupiter with the galactic plain in the background will not reappear until 2031.
"Stargazing studies enable us to learn from a distance about moons in the solar system and are also relevant to future missions that will visit these worlds," says Timo Prusti, ESA Gaia Project Scientist. "As this result shows, Gaia is an extremely versatile mission: it not only extends our knowledge of stars, but also of the solar system."
Accurate knowledge of Europe's orbit will help prepare space missions targeting Jupiter systems such as ESA's JUpiter ICy Moons Explorer (JUICE) and NASA's Europa Clipper, both of which are due to be launched in the next decade.
"Such observations are extremely exciting," says Olivier Witasse, JUICE Project Scientist at ESA. "JUICE will reach Jupiter in 2029. The best possible knowledge of the positions of the moons of the system will help us prepare for mission navigation and future data analysis, and to plan the entire science we intend."
"Science depends on it that we know things like the exact trajectory of the moon and how close a spaceship will be to a particular body. The better our knowledge, the better this planning – and the subsequent data analysis.
Introduction of JUICE – the Jupiter Icy Moons Explorer
Morgado et al. First stellar occultation by the Galilean Moon Europe and upcoming events between 2019 and 2021, Astronomy & Astrophysics (2019). DOI: 10.1051 / 0004-6361 / 201935500
European Space Agency
Thank you, Gaia: Astronomers are spying on Europe and blocking distant star (2019, July 25)
retrieved on July 25, 2019
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