Later this month, skywatchers in Africa may see a star blink out of sight thanks to a quirk of celestial arrangements.
The mission of the European Space Agency (ESA) GaiaLaunched in 2013, it has been a powerhouse of observational astronomy and has had a major impact on the way scientists study the sky. From mapping the galaxy in amazing detail to find a star cluster hidden by glare in other telescopes, the spacecraft’s ultra-sensitive instruments have proved invaluable in studying the Milky Way†
But Gaia doesn’t just help us understand the distant stars; it also shapes our view of our neighboring worlds and their moons. In 2017, scientists used data from Gaia to predict for the first time what scientists call a star’s occultation by Jupiter‘s moon Europe†
photos† Europa, mysterious icy moon of Jupiter
An occultation occurs when one object is covered by another as seen from Soil† For example, a total solar eclipse is a type of occultation of the sun by the moon, albeit an occultation that is very obvious to those in the right place to see it.
Conversely, an eclipse of a distant star by an alien satellite would go unnoticed by almost anyone.
Such occultations can only be seen from a narrow path across part of the Earth’s surface, making them a rare treat to look up to the sky. But for astronomers, occultations can be even more special, as these events present rare opportunities to refine the orbit and shape of a distant world.
And scientists now say such an occultation will occur on June 19 (June 18 in the United States, where the event will not be visible), as Europe once again stands poised to occult a star as predicted using Gaia- data. This event will be even more remarkable than the previous one, especially for astronomers at the Paris Observatory, who are helping ESA scientists prepare for a mission to study Europe and neighboring moons.
“What makes Europa’s upcoming occultation special is that this moon will be in Jupiter’s shadow at that time,” agency officials wrote in a statement. pronunciation† “Because Jupiter will block that sunlight during the occultation, observers will only know Europa is there when it temporarily makes the star disappear.”
Immersed in the shadow of Jupiter itself, Europa’s pitch-black disk will obscure the star like the new moon passing in front of the sun, making the distant star appear to go out and on shortly after. For a brief moment, observers on the ground can stand in the shadow of Europa, as cast by the faint light of a star many light-years away. By accurately timing the passage of this shadow, astronomers at ESA can learn more about Europa’s orbit.
ESA plans to launch the Jupiter Icy moons Explorer, or JUICE mission, next year, embarking on a long journey to Jupiter, where the spacecraft will conduct extensive study of both Europa and its larger sibling moon, Ganymede†
Together with NASA’s Europa Clipper mission, JUICE will reveal one of the solar system’s most fascinating worlds in stunning detail. Some scientists believe that Europe could be habitable, but to understand if that is the case, they need to look beneath the icy surface. To get the best results, Europe’s orbit must be tightly constrained, which is why observing this occultation is so important to ESA.
“It will help spacecraft operators navigate more accurately between these icy worlds, and it will help scientists draw conclusions from the flyby data,” ESA officials wrote in the statement. “For example, if you know the exact height of the spacecraft above the surface of a moon, calculations about the moon’s interior become more accurate.”
If you happen to be in the right place, you could observe this event for yourself with just a modest telescope. The occultation will follow a path through southern Africa, with the centerline passing through Namibia, Botswana and Zimbabwe. Further east, the approaching sunrise will make the sky too clear to see the occultation.
In the early morning hours, before sunrise on June 19, skywatchers in southern Africa will see Jupiter rise in the eastern sky, tracking Saturn and the moon with Mars not far behind.
Looking at Jupiter at 5:00 a.m. local time in Namibia, Botswana and Zimbabwe (0300 GMT or 11:00 p.m. EDT on June 18), it will appear that all four Galilean moons (Europa, Ganymede, Callisto and Io) are visible. But right now, Europa will actually be completely in Jupiter’s shadow, and the fourth visible light will actually be a 10th magnitude star in the constellation of Pisces.
Europa is predicted to pass in front of that star at 03:05:57 UTC, but local times vary by longitude, so be sure to get to the telescope early to be safe. Only during the occultation do you see all four moons (one in silhouette) when the star disappears and only three points of light remain on Jupiter’s flank. If Europa slips away again, the star will reappear in your telescope.
If you want to take your observations to the next level, be sure to time the start and end of the transit accurately and send this data along with your observation location to the Paris Observatory (firstname.lastname@example.org). With your help, astronomers can calibrate their own observations and help ESA get more out of the JUICE mission!
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