Among the varied locations people have aspired to go to in the photo voltaic system, the solar stays the most foreboding. On December 24, 2024, NASA’s Parker Solar Probe arrived inside 6.1 million km from the star’s floor. This is a brief distance to be from the solar: no spacecraft has ever made such an in depth method. Even the Parker Solar Probe took seven years to get right here.
The probe made one other method to the solar on March 22 and can accomplish that once more on June 19 this 12 months.
Watching the solar
Sunlight is the fundamental supply of power for earthlife. The solar’s core produces this power utilizing nuclear fusion. The star additionally has robust, dynamic magnetic fields crisscrossing its floor, and sudden adjustments in the means they’re organized give rise to intense explosions referred to as photo voltaic flares. Numerous electrons, protons, and heavy nuclei are spit out of the photo voltaic corona — the uppermost layer of the solar’s environment — at about 900 km/s.
These particles carry an infinite quantity of power and typically rush in direction of the earth at super velocity in an occasion referred to as a coronal mass ejection. Their results on the earth represent a photo voltaic storm, together with electrical grid failures, lack of telecommunication channels, and harm to the ozone layer. They also can harm devices onboard satellites.
To perceive the dynamics of the corona over time and their results on the photo voltaic system at massive, scientists want to observe the solar intently. This is additionally why the Indian Space Research Organisation launched and is at present working the Aditya-L1 probe, stationed at about 150 million km from the star.
An in a position warmth protect
Around six many years in the past, a scientist named Eugene Parker predicted the existence of the photo voltaic wind: a stream of charged particles flowing out from the solar in all instructions. NASA named the Parker Solar Probe in his honour.
The probe was launched on board a Delta IV rocket from Cape Canaveral in Florida in August 2018. Once in area, the probe’s most velocity was an astounding 692,000 km/hr.
To shield in opposition to the solar’s intense warmth, the probe has an 8-foot-wide, 4.5-inch thick carbon-carbon composite materials protect that may face up to up to 1,370º C whereas weighing solely 73 kg. This protect was constructed by researchers at the Johns Hopkins Applied Physics Laboratory. It consists of a carbon composite foam sandwiched between two carbon plates. Its sun-facing facet is coated with white ceramic paint to replicate as a lot daylight as attainable as a substitute of absorbing it.
Just a number of metres behind the protect, in its shadow, the ambient temperature drops to 29º C, permitting the probe’s scientific devices to function with out particular provisions to preserve the temperature. The probe additionally has two units of solar energy arrays: one in the protect’s shadow that provides energy to the devices and the different on the sun-facing facet, which makes use of a particular fluid pump to cool itself whereas powering the probe throughout its shut approaches.
Touching the solar
Curiously, the first impediment to the mission’s success wasn’t the solar’s warmth however its gravity. Since the probe flew by area at a really excessive velocity, it had to decelerate considerably because it obtained shut to the solar. If it didn’t, the solar’s gravity would have inspired it to dive proper into the star. This is why Parker’s first mission profile had the probe fly in direction of Jupiter and swing round the fuel large to obtain an optimum velocity to fly in direction of the solar. This concept fell out of favour due to the massive journey distance.
The probe’s closing mission profile was extra direct: to use the mixed gravitational forces of the earth and Venus to slowly spiral nearer to the solar’s floor, in the course of spending greater than 2,000 hours flying by the corona and 24 instances alongside the photo voltaic equator.
The probe has 4 scientific devices: FIELDS, Integrated Science Investigation of the Sun (ISoIS), Wide-Field Imager (WISPR), and Solar Wind Electrons Alphas and Protons (SWEAP). FIELDS measures the electrical and magnetic fields of the solar’s environment; ISoIS observes the energetic particles that trigger photo voltaic storms whereas SWEAP data their properties; and WISPR takes photos because it passes by the corona.
A ‘sun-touching’ occasion occurred in April 2021 when Parker moved nearer to the solar than its Alfvén floor — the top past which the photo voltaic wind can’t have an effect on the star’s floor — as ascertained by the FIELDS and SWEAP devices.
A fifth instrument, referred to as a Faraday cup, lies outdoors the shadow of the warmth protect and measures the density of ions and electrons in the photo voltaic wind. It is product of a molybdenum alloy with a melting level of two,349º C.
Blowin’ in the (photo voltaic) wind
Parker information has already revealed many new particulars about the solar. The photo voltaic system is ceaselessly coated in mud particles created when area rocks climate and scientists believed the mud ought to be all over the place. Yet Parker revealed dust-free pockets close to the solar. The probe additionally detected magnetic switchbacks: components of the photo voltaic wind the place the magnetic discipline (created by the collective of charged particles) abruptly bent again on itself.
An vital open query in photo voltaic astrophysics is why the solar’s floor is solely 6,000º C or so whereas the photo voltaic corona is 200-times hotter. Based on Parker’s information of magnetic switchbacks and different associated phenomena, scientists imagine the reply to the thriller lies in Alfvén waves: an oscillation of ions in the plasma launched by the solar, set in movement by forces in the surrounding magnetic discipline.
During its close-approach on March 22, the Parker Solar Probe as soon as once more tried to get inside round 6 million km of the solar’s floor. What did it discover this time?
Shamim Haque Mondal is a researcher in the Physics Division, State Forensic Science Laboratory, Kolkata.
Published – March 25, 2025 09:00 am IST
