What is the Visible Emission Line Coronagraph (VELC)?

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About Visible Emission Line Coronagraph (VELC):

It is the primary payload of the Aditya-L1 Mission–India’s first mission to observe the Sun from a vantage point 1.5 million kilometres from the earth.
It is an internally occulted solar coronagraph capable of simultaneous imaging, spectroscopy, and spectro-polarimetry close to the solar limb.
It is built by the Indian Institute of Astrophysics (IIA) at its CREST (Centre for Research and Education in Science and Technology) campus at Hosakote, Karnataka.
The VELC consists of a coronagraph, spectrograph, polarimetry module, and detectors, aside from auxiliary optics.
Purpose:
- It will observe the solar corona, which is the tenuous, outermost layer of the solar atmosphere.
- VELC can image the solar corona down to 1.05 times the solar radius, which is the closest any such payload has imaged.
- It will analyze the coronal temperature, plasma velocity, density, etc.
- It will also study Coronal Mass Ejections (CMEs) and the solar wind.

What is a Coronagraph?

It is a specialized instrument designed to block out the light of the sun so that researchers can glimpse the burning star’s hot, thin, outermost layer, called the corona.
The French astronomer Bernard Lyot invented the coronagraph in the 1930s.
The sun’s corona is normally visible only during solar eclipses, when the moon’s shadow covers the bright central layers of our parent star and allows its dimmer corona to appear.
A coronagraph mimics this natural phenomenon with a circular mask that sits inside a telescope and selectively blocks the bulk of the sun’s light.
The specialized coronagraphs act as filters on the central star, allowing the tiny fragments of planetary light to shine through.

Q1: What are Coronal Mass Ejections (CMEs)?

CMEs are large expulsions of plasma and magnetic field from the sun’s atmosphere—the corona, that propagate outward into interplanetary space. During a CME, the sun releases a colossal amount of material, including electrons, protons, and heavier ions, as well as magnetic fields.

News: ‘First significant’ results from payload onboard maiden solar mission Aditya-L1