How majestic, the sight will be when our Moon passes in front of a Red giant whose diameter is 700 times than that of our Sun? As Earthlings, we witness some of the most fascinating celestial events happening around us. One such phenomenon is occulations involving our beloved Moon. A lunar occultation occurs when the Moon passes in front of a celestial object, temporarily obscuring it from our view. One of the most visually striking occultations involves Antares, the brightest star in the constellation Scorpius and one of the largest and most luminous stars visible to the naked eye. Located about 550 light years from Earth, Antares is renowned for its deep reddish hue which makes it a striking celestial object, often mistaken for Mars due to its color and brightness. When the Moon moves across the sky and briefly hides this bright star, observers on Earth can witness a dramatic disappearance and reappearance of Antares, making it a truly mesmerizing event.
When the Moon covers Antares, scientists can analyze how the star’s light behaves which can be used to determine the size and atmospheric composition of Antares, variations in the star’s brightness and structure, and the lunar limb profile which helps us refine our understanding of the Moon’s topography. Lunar occultations are only visible from a limited portion of Earth’s surface. Because the Moon is much closer to Earth than other celestial objects, its apparent position in the sky shifts based on the observer’s location due to parallax. This effect causes the Moon’s position to vary by up to two degrees equivalent to four times the diameter of the full Moon, when viewed from opposite sides of the Earth. As a result, if the Moon aligns to pass in front of a specific object for an observer in one region, it may appear up to two degrees away from that object for someone on the other side of the planet.
To witness a lunar occultation of Antares, observers need clear skies and a location within the occultation path. The event typically unfolds in a few stages. The first stage is the approach, where the Moon slowly moves closer to Antares. And when Antares vanishes behind the Moon’s illuminated or dark edge, the stage of disappearance occurs. The third stage, the Hidden Phase occurs when the star remains obscured for several minutes to over an hour, depending on the observer’s location. And the final stage, the reappearance, happens when Antares suddenly re-emerges from the Moon’s opposite limb, creating a dramatic spectacle.
The occultation will happen on the 21st of February. Unfortunately, the occultation will not be visible for Sri Lankans. It will be only visible for the people who live in Argentina, Chile, Uruguay, Brazil and Bolivia. But let’s not diminish our hopes, as the same occultation will be visible to us on the 22nd of January, 2028.
Some theories argue that the red giant Antares has already gone supernova, meaning that in reality there is no Antares out there as the light emitted from it takes around 550 years to reach the Earth. But scientists say that Antares is a late-stage star with a high likelihood of going supernova within the next few hundred thousand years. While we currently see Antares as it was 550 years ago, it’s unlikely, but not impossible that it has already exploded, and the light just hasn’t reached Earth yet. However, given its estimated remaining lifespan, most astronomers believe it is still in its pre-supernova phase. If Antares does go supernova, it would be an incredibly bright event in our sky, potentially visible even during the day.
Beyond their visual appeal, occultations provide valuable data for various studies. Studying these events helps refine our understanding of celestial mechanics, stellar structures, and lunar features. Additionally, occultations can contribute to tracking the Moon’s orbit with high precision, which is crucial for space missions and astronomical research.
References –
Antares | Red Giant, Supergiant, Binary System – https://www.britannica.com/place/Antares-star
Lunar occultation of Antares – https://in-the-sky.org/news.php?id=20250125_16_100
Occultations – https://www.skyatnightmagazine.com/advice/occultation-astronomy-what
Lunar Occultation – https://www.sciencedirect.com/topics/physics-and-astronomy/lunar-occultation
Written by,
Akitha Lithmal,
1st year, Faculty of Science.
University of Colombo.