/wion/media/agency_attachments/2024/12/26/2024-12-26t112006978z-wion-white-logo-for-website-2-1.png){kind=logo}
/wion/media/agency_attachments/2024/12/13/2024-12-13t071548098z-wionlogo.webp)
/wion/media/post_attachments/files/2023/09/01/376739-l-1.jpg)
Chennai
Across the United States, Mexico and Canada, observers would get a feel of "day turning into night" during Total Solar eclipse on April 8, 2024. This is an astronomical phenomenon that occurs once in few years and attracts a huge amount of public enthusiasm, as day suddenly turns into night and the temperature dips, owing to sunlight being blocked. People in India would not be able to get a feel of this Total Solar Eclipse, but India's Sun-study mission Aditya-L1 has been witnessing a round-the-clock Total Solar Eclipse, since the craft became operational earlier this year.
WION spoke to experts from the Indian Institute of Astrophysics to explain how Aditya-L1 can see a Total Solar Eclipse, even when there is no Eclipse taking place.
"The way the relatively smaller Moon blocks the Earth's view of the massive Sun, is the same as bringing a thumb in front of the eye and blocking the view of a large building that is in front. The thumb is no way comparable to the size of the building, but it is closer to the eye and blocks the large building that is at a distance" Jayant Murthy (Retd), Senior Professor from the Indian Institute of Astrophysics told WION.
He added that across North America, it would appear as though a disc (Moon) had covered the Sun.
What is Aditya-L1?
Aditya-L1 is India's first dedicated mission to study the Sun and its various phenomena. Launched on September 2, 2023, the craft reached its destination on January 6, 2024. Aditya-L1 has been placed at a vantage point known as 'L1' or 'Lagrange point 1', from here it can have an unobstructed view of the Sun.
This vantage location in interplanetary space is situated 1.5 million (15 lakh) kilometres from earth. For context, the moon is only 4 lakh kilometres away from the earth. The Lagrange point 1 is at one percent of the Earth-Sun distance which is about 150 million kilometres.
Sun is visible from the ground, what is the need for a Space-based study?
Studies related to the Sun can be carried out from ground-based observatories, but on a given point on earth, the sun is visible during the day and is not visible at night, due to the alternating day-night cycle. So, an agency would require multiple stations across the earth to view and study the sun continuously.
Even if there are multiple observatories on the ground, each one of them would record different kinds of observations. The unique characteristics of the equipment, the dust particles that scatter the radiation, the distortion caused by the earth's atmosphere are among the factors that bring in inconsistencies in the sun-study data collected from different ground-based observatories.
The layers of the Sun and what a Solar Eclipse does
The Sun's Photosphere is what emits the strongest light. The Photosphere is then covered by the Chromosphere (which extends 1000s of kms) and finally there is the Corona (Sun's outermost layer).
"The Sun's Corona emits light, but it is million times less intense than that of the Photosphere. Therefore, it is only during a solar eclipse(when moon covers the sun's Photosphere by coming in the path between earth and Sun) that we are able to study the faint light from the Corona" Prof. Ramesh from the Indian Institute of Astrophysics, explained to WION. He added that eclipses are phenomenon that occurred once in few years and that studying the Solar Corona during the few minutes of the eclipse would be insufficient to gather any meaningful data and inferences.
Why is it important to study the Solar Corona?
Professor Ramesh said that the interest in studying the Solar Corona is owing to its dynamic nature and the regular eruptions from the Corona (Coronal Mass Ejections). Coronal Mass Ejection is a phenomenon when charged particles from the sun are ejected at speeds of 3000km/second. At this speed, it can reach the earth in around 15hours, he explained.
Such phenomena can affect the electronics and solar panels of satellites orbiting the earth, it can also cause geomagnetic storms that can temporarily swell up earth's atmosphere and drag satellites that are flying as low as 200km orbit. In recent years, such an incident had damaged a few dozen Starlink satellites.
Also watch | India sun mission Aditya-L1 begins collecting data from distance of 50,000 kms
When such high-speed, charged particles from the Sun reach the earth's atmosphere, the upper layers of the atmosphere act as a barrier and divert the charged particles to earth's poles, thereby causing the Northern Lights (Aurora Borealis) and Southern Lights (Aurora Australis), a dazzling display of vibrant and colorful lights. These are often seen in shades of blue-green-yellow-red in the winter night skies near the earth's north polar and south polar regions.
How does Aditya-L1 create a '24/7 Solar Eclipse'?
We know that the moon blocking the earth's view of the sun helps observe the faint light of the Solar Corona. However, it is possible to use technological advancements and block the bright light from the Sun, while only viewing the faint light emitted from the Corona.
"On the Aditya-L1 craft, we have a device known as Visible Emission Line Coronagraph (VELC), which is capable of artificially blocking the light of the Photosphere and studying the light from the Corona. This is the same as the view during a Solar eclipse" Prof Ramesh added.
The VELC has been contributed by the Indian Institute of Astrophysics and Prof. Ramesh is the Principal Investigator for the VELC.
By using the VELC, Aditya-L1 can view the Solar Corona throughout its multi-year mission at the L1 point.
Also watch | Solar Eclipse 2024: Why Aditya L1 won't catch a glimpse of total solar eclipse
However, it must be noted that the Aditya-L1 craft can never see the naturally-caused Solar Eclipse, like it is visible from Earth. This is because the Aditya craft sits at the L1 points, which offers an unobstructed view of the Sun. Also, it must be remembered that the L1 point is several lakh kilometres beyond the moon and the moon cannot obstruct the Aditya craft's view of the Sun.
From the L1 vantage point, around which the spacecraft will be circling, the VELC instrument will be able to image the sun's corona every single minute and help researchers understand the fast changes in Solar atmosphere.
Using a Polarimeter, we can also measure and predict which sun spots(dark regions with strong magnetic fields, where even light cannot enter) can erupt and lead to Coronal Mass ejections. in future, this could help us predict any danger to satellites around earth, assess which CMEs will reach earth and which won't.