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Antares will be covered by the Moon in a rare lunar occultation and will transform the night sky of part of Brazil into a showcase for a supergiant star visible between night and dawn.
Antares will be the main attraction in the sky this Sunday, May 3, when the Moon passes in front of the star in a phenomenon known as a lunar occultation. The event can be seen in part of Brazil between 9:47 PM and 2:03 AM on Monday, May 4, Brasília time, and draws attention for involving one of the brightest stars in the night sky, located about 600 light-years from Earth and with about 883 times the radius of the Sun.
The observation of the Antares occultation can be followed throughout the South Region, as well as a large part of São Paulo, Mato Grosso do Sul, Rio de Janeiro, and the extreme south of Minas Gerais. Outside this band, the phenomenon will not be visible. The event stands out because it is not an eclipse in the most common sense of the word, but an exact passage of the Moon in front of the star, something that can only be seen from specific areas of the planet.
What is the lunar occultation of Antares
A lunar occultation happens when the Moon passes in front of a celestial object and temporarily covers it for observers on Earth. In this case, the covered object will be Antares, also called Alpha Scorpii, a star that holds a prominent position in the heart of the constellation Scorpius.
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Although many people use the word eclipse to describe the phenomenon, the correct name in this case is lunar occultation. The difference is important because the event does not involve the darkening of the Sun or the Moon, but rather the temporary disappearance of a star behind the lunar disk.
Why Antares attracts so much attention in the sky
Antares is a red supergiant star of class M and is among the brightest in the celestial sphere. The base text states that it is the 16th brightest star in the night sky, although in some counts it appears as the 15th, depending on how the Capella system is considered.
The numbers help explain the fascination surrounding this star. Antares has between 15 and 18 solar masses and about 883 times the radius of the Sun. If it were at the center of the Solar System, its outermost part would reach a region between the orbits of Mars and Jupiter. Even with this extreme size, its density is very small.
The numbers that explain the size of Antares
Antares is about 600 light-years from Earth and has an apparent magnitude of +1.09, in addition to slow variability. It is also part of the group of brightest stars near the ecliptic, alongside Aldebaran, Spica, and Regulus.
Another curious point is the origin of the name. Antares means the antagonist of Ares, the god of war in Greek mythology, corresponding to Mars for the Romans. The explanation lies in the star’s reddish glow, which causes it to be visually associated with the planet Mars.
Where the lunar occultation of Antares can be seen in Brazil
In Brazil, the visibility band covers the entire South Region and also a large part of São Paulo, Mato Grosso do Sul, Rio de Janeiro, and the extreme south of Minas Gerais. In other areas of the national territory, the lunar occultation of Antares will be outside the field of observation.
This geographical cut-off is decisive because the phenomenon does not appear the same way for all observers. Depending on the exact location of whoever is looking at the sky, the Moon may pass exactly in front of Antares or appear displaced in relation to the star.
Lunar occultation time and example of what will be seen in Porto Alegre
The event is expected to occur between 9:47 PM this Sunday and 2:03 AM on Monday morning, Brasília time. For Porto Alegre, the astronomical guide InTheSky.org provides a more detailed schedule that helps visualize how the phenomenon will happen in practice.
In the capital of Rio Grande do Sul, the disappearance of Antares behind the Moon is predicted for 10:14 PM, in the eastern direction of the sky, at an altitude of 39.3 degrees. The reappearance will occur at 11:09 PM, when the star will be seen again at an altitude of 51.1 degrees. These times show how brief a lunar occultation can be, but still very striking for those in the correct observation band.
Why Only Part of Earth Can See Antares Disappear Behind the Moon
Lunar occultations are visible only from a small fraction of Earth’s surface. This happens because the Moon is much closer to Earth than other celestial objects, which causes its apparent position in the sky to vary depending on the observation location.
The base text explains that this difference occurs due to parallax. Viewed from opposite points on the planet, the Moon’s position can vary by up to two degrees, equivalent to four times the diameter of the full Moon. In practice, this means that one observer may see the Moon pass exactly in front of Antares, while another, in a different region, will see the two celestial bodies separated in the sky.
What the Lunar Occultation Map Shows in Practice
The map cited in the base divides visibility regions into distinct areas for the disappearance and reappearance of Antares. Red contours indicate where the star’s disappearance can be seen, while blue contours show where its return will be observable.
Solid lines represent locations where the occultation should be visible with binoculars and at a good altitude in the sky. Dotted contours show areas where the phenomenon occurs above the horizon but may be hindered by very clear skies or the Moon’s very low position. Outside these contours, the Moon does not cover Antares at any time or is below the horizon during the occultation.
What This Means for Skygazers
For Brazilian observers within the visibility band, Sunday night offers a rare chance to witness a precise alignment between the Moon and a giant, very bright star. It’s a type of event that combines visual impact, a short observation window, and strong appeal for those who follow astronomical phenomena.
Beyond the visual aspect, the lunar occultation of Antares also helps to show in a simple way how position, distance, and perspective change how the sky is viewed from Earth. It is precisely this combination of beauty and practical explanation that transforms the phenomenon into a special attraction for the night and early morning.
Do you intend to try to see Antares disappear behind the Moon this Sunday?
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