Question: What event, considered to be a birders principal meeting in South America, is held every orbital period of the Earth moving in its orbit around the sun?
Context: The South American Birdwatching Fair is an annual event for birdwatchers, held every year in a different country of the continent.  It is described as the birder's principal meeting in South America, with people from all the world. Kepler-1520 (initially published as KIC 12557548) is a K-type main-sequence star located in the constellation Cygnus.  The star is particularly important, as measurements taken by the "Kepler" spacecraft indicate that the variations in the star's light curve cover a range from about 0.2% to 1.3% of the star's light being blocked.  This indicates that there may be a rapidly disintegrating planet, a prediction not yet conclusively confirmed, in orbit around the star, losing mass at a rate of 1 Earth mass every billion years.  The planet itself is about 0.1 Earth masses, or just twice the mass of Mercury, and is expected to disintegrate in about 100-200 million years.  The planet orbits its star in just 15.7 hours, at a distance only two stellar diameters away from the star's surface, and has an estimated effective temperature of about 2255 K.  The orbital period of the planet is one of the shortest ever detected in the history of the extrasolar planet search.  In 2016, the planet was confirmed as part of a data release by the "Kepler" spacecraft. RX J0806.3+1527 or HM Cancri (sometimes shortened to "HM Cnc" or "J0806" after establishing identity) is an X-ray binary star system about 1600 ly away.  It comprises two dense white dwarfs orbiting each other once every 321.5 seconds (in this system the "year" duration is of only 5.4 minutes), at an estimated distance of only 80000 km apart (about 1/5 the distance between the Earth and the Moon).  The two stars orbit each other at speeds in excess of 400 km/s .  The stars are estimated to be about half as massive as the Sun.  Like typical white dwarfs, they are extremely dense, being composed of degenerate matter, and so have radii of order the radius of Earth.  Astronomers believe that the two stars will eventually merge, based on data from many X-ray satellites, such as Chandra X-Ray Observatory, XMM-Newton and the Swift Gamma-Ray Burst Mission.  These data show that the orbital period of the two stars is steadily decreasing at a rate of 1.2 milliseconds per year as they thus are getting closer by approximately 60 cm per day.  At this rate, they can be expected to merge in approximately 340,000 years.  With a revolution period of 5.4 minutes RX J0806 is the shortest orbital period binary system currently known. A geosynchronous orbit (sometimes abbreviated GSO) is an orbit around Earth of a satellite with an orbital period that matches Earth's rotation on its axis, which takes one sidereal day (23 hours, 56 minutes, and 4 seconds).  The synchronization of rotation and orbital period means that, for an observer on Earth's surface, an object in geosynchronous orbit returns to exactly the same position in the sky after a period of one sidereal day.  Over the course of a day, the object's position in the sky traces out a path, typically in a figure-8 form, whose precise characteristics depend on the orbit's inclination and eccentricity.  Satellites are typically launched in an eastward direction.  Those closer to Earth orbit faster than Earth rotates, so from Earth, they appear to move eastward while those that orbit beyond geosynchronous distances appear to move westward. 3753 Cruithne ( or ) is a Q-type, Aten asteroid in orbit around the Sun in 1:1 orbital resonance with Earth, making it a co-orbital object.  It is an asteroid that, relative to Earth, orbits the Sun in a bean-shaped orbit that effectively describes a horseshoe, and that can transition into a quasi-satellite orbit.  Cruithne does not orbit Earth and at times it is on the other side of the Sun, placing Cruithne well outside of Earth's Hill sphere.  Its orbit takes it inside the orbit of Mercury and outside the orbit of Mars.  Cruithne orbits the Sun in about 1 year but it takes 770 years for the series to complete a horseshoe-shaped movement around the Earth. A geostationary orbit, geostationary Earth orbit or geosynchronous equatorial orbit (GEO) is a circular orbit 35786 km above the Earth's equator and following the direction of the Earth's rotation.  An object in such an orbit has an orbital period equal to the Earth's rotational period (one sidereal day) and thus appears motionless, at a fixed position in the sky, to ground observers.  Communications satellites and weather satellites are often placed in geostationary orbits, so that the satellite antennas (located on Earth) that communicate with them do not have to rotate to track them, but can be pointed permanently at the position in the sky where the satellites are located.  Using this characteristic, ocean color satellites with visible and near-infrared light sensors (e.g. the Geostationary Ocean Color Imager (GOCI)) can also be operated in geostationary orbit in order to monitor sensitive changes of ocean environments. A year is the orbital period of the Earth moving in its orbit around the Sun.  Due to the Earth's axial tilt, the course of a year sees the passing of the seasons, marked by changes in weather, the hours of daylight, and, consequently, vegetation and soil fertility.  In temperate and subpolar regions around the globe, four seasons are generally recognized: "spring", "summer", "autumn" and "winter".  In tropical and subtropical regions several geographical sectors do not present defined seasons; but in the seasonal tropics, the annual "wet" and "dry" seasons are recognized and tracked. A Sun-synchronous orbit (SSO, also called a heliosynchronous orbit) is a nearly polar orbit around Earth (also called geocentric orbit) in which the satellite passes over any given point of the planet's surface at the same local solar time.  Such an orbit can place a satellite in constant sunlight and is useful for imaging, spy, and weather satellites.  More technically, it is an orbit arranged in such a way that it precesses once a year.  The surface illumination angle will be nearly the same every time that the satellite is overhead.  This consistent lighting is a useful characteristic for satellites that image the Earth's surface in visible or infrared wavelengths (e.g. weather and spy satellites) and for other remote-sensing satellites (e.g. those carrying ocean and atmospheric remote-sensing instruments that require sunlight).  For example, a satellite in sun-synchronous orbit might ascend across the equator twelve times a day each time at approximately 15:00 mean local time.  This is achieved by having the osculating orbital plane precess (rotate) approximately one degree eastward each day with respect to the celestial sphere to keep pace with the Earth's movement around the Sun. A low Earth orbit (LEO) is an orbit around Earth with an altitude of 2000 km or less, and an orbital period of between about 84 and 127 minutes.  Objects below approximately 160 km will experience very rapid orbital decay and altitude loss due to atmospheric drag. Mira B, also known as VZ Ceti, is the companion star to the variable star Mira.  Suspected as early as 1918, it was visually confirmed in 1923 by Robert Grant Aitken, and has been observed more or less continually since then, most recently by the Chandra X-Ray Observatory.  Its orbit around Mira is poorly known; the most recent estimate listed in the Sixth Orbit Catalog of Visual Binary Stars gives an orbital period of roughly 500 years, with a periastron around the year 2285.  Assuming the distance in the Hipparcos catalog and orbit are correct, Mira A and B are separated by an average of 100 AU.
Answer: South American Birdwatching Fair