Longest day of the year on June 21: All about the summer solstice
As the Northern Hemisphere welcomes the arrival of summer, June 21, 2025, brings the year's longest day and shortest night—the summer solstice.This astronomical phenomenon occurs when the Earth's tilt leans most directly toward the Sun, placing it at its highest point in the sky over the Tropic of Cancer.The solstice will officially occur at 8:12 am IST as most countries in the Northern Hemisphere will experience the longest daylight hours on June 21.advertisement
Countries like India, the United States, and much of Europe will enjoy extended sunshine, with the North Pole experiencing 24 hours of daylight.
Photo: Nasa
WHY WILL JUNE 21 BE THE LONGEST DAY OF THE YEAR?The solstice date varies slightly each year due to the fact that Earth's orbit around the Sun takes approximately 365.25 days. Leap years adjust for this, helping to keep our calendar aligned with the planet's position.Scientifically, the summer solstice highlights Earth's 23.5-degree axial tilt, the reason for our seasons.On this day, the Sun's rays strike the Northern Hemisphere more directly and for a longer duration, providing the most sunlight of the year.advertisementIn contrast, the June solstice marks the shortest day of the year in the Southern Hemisphere. The farther a location is from the equator, the more noticeable this effect becomes.Regions within the Antarctic Circle enter a period of polar night, during which the Sun doesn't rise above the horizon at all.
Graphic: Nasa
Beyond science, the solstice holds deep cultural and spiritual meaning. From ancient Egypt to modern England, people have observed this celestial event for thousands of years.Stonehenge remains a focal point, where crowds gather to witness the sunrise through the monument's ancient stones. In India, the solstice is closely followed by International Yoga Day, promoting harmony between body and mind.The summer solstice not only signals the beginning of astronomical summer but also invites reflection. As daylight begins to wane from June 22 onward, it shows nature's rhythms and the Earth's ceaseless orbit.Trending Reel
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Indian Express
13 hours ago
- Indian Express
ISRO readies SpaDeX-2 mission to dock satellites in elliptical orbit
After successfully bringing together two satellites in space, scientists at the Indian Space Research Organisation (ISRO) are drawing up plans for a second SpaDeX mission — this time to dock two satellites in an elliptical orbit. The ability to join two satellites in space, known as docking, is critical for India's upcoming Chandrayaan-4 mission and the proposed Bharatiya Antariksh Station, the country's planned space station. In the first SpaDeX mission, two 220-kg satellites were launched into a 470-km circular orbit. With a small relative velocity introduced between them, the satellites were allowed to drift apart before being progressively brought closer. On January 16, they successfully docked. The experiment also demonstrated power sharing between the satellites and their ability to receive commands as a single composite unit. With this, India became only the fourth country, after the US, Russia, and China, to demonstrate in-space docking capabilities. However, the feat was carried out in a relatively easier circular orbit. 'Docking in a circular orbit is much easier than docking in an elliptical orbit. This is because the trajectory and velocity of the satellites remain constant in a circular orbit, whereas they keep changing on an elliptical orbit. What this essentially means is that calculations done for one point will not be relevant after a few minutes,' said a scientist in the know of the matter. 'This is, however, what the SpaDeX 2 experiment will attempt.' This capability is likely to play a vital role in future missions, such as Chandrayaan-4, where multiple modules may be launched separately, and docking and undocking will be required in both Earth and lunar orbits. For moon missions, ISRO typically launches spacecraft into an elliptical Earth orbit, gradually raising the apogee (farthest point) through engine burns at perigee (closest point) to use minimal fuel. This process sets up a slingshot trajectory toward the Moon, making docking in elliptical orbits a practical requirement for complex missions. The first docking operation took a considerable amount of time, as the agency approached it with extreme caution. 'This was the first time ISRO was attempting docking and undocking, so everything had to be meticulously planned and tested. In fact, several of the sensors being used were developed for this mission itself and had to be calibrated to readings in space. Once that was done, the readings were used to conduct several simulations on Earth before the actual docking was attempted. And, even then, the satellites were brought closer very slowly. With all the knowledge gathered during the first docking, the second became easier. It was quicker, without the satellites needing to stop and go as many times as the first time,' the scientist said. During the initial attempt, the SpaDeX satellites were brought progressively closer, halting at designated checkpoints – 5 km, 1.5 km, 500 m, 225 m, 15 m, and 3 m – before finally docking. In the second attempt, post-separation, the process was smoother and faster, with fewer halts en route to redocking. Anonna Dutt is a Principal Correspondent who writes primarily on health at the Indian Express. She reports on myriad topics ranging from the growing burden of non-communicable diseases such as diabetes and hypertension to the problems with pervasive infectious conditions. She reported on the government's management of the Covid-19 pandemic and closely followed the vaccination programme. Her stories have resulted in the city government investing in high-end tests for the poor and acknowledging errors in their official reports. Dutt also takes a keen interest in the country's space programme and has written on key missions like Chandrayaan 2 and 3, Aditya L1, and Gaganyaan. She was among the first batch of eleven media fellows with RBM Partnership to End Malaria. She was also selected to participate in the short-term programme on early childhood reporting at Columbia University's Dart Centre. Dutt has a Bachelor's Degree from the Symbiosis Institute of Media and Communication, Pune and a PG Diploma from the Asian College of Journalism, Chennai. She started her reporting career with the Hindustan Times. When not at work, she tries to appease the Duolingo owl with her French skills and sometimes takes to the dance floor. ... Read More
The Hindu
17 hours ago
- The Hindu
Is it a moon? Is it a dwarf planet? Well, it's Charon, and it could well be both!
Charon's discovery The story of Charon's discovery takes us back to 1978 – a time when even astronomers were still thinking that Pluto was a planet. Little was known about Pluto and its system, but all that was about to change in the decades that followed. On the morning of June 22, American astronomer James Christy already had his head whirling around. If you were under the impression that he was zeroing in on the solution for an astronomical problem, you couldn't be further from the truth. Christy was sharpening his plans to move his house, getting ready for a week's leave from the U.S. Naval Observatory in Flagstaff, Arizona – his workplace. It was under these circumstances that Robert Harrington, his boss, handed him a set of six photographs of Pluto. Christy and Harrington were looking to refine Pluto's orbit around the sun – a journey that takes Pluto 248 Earth years. Pluto's average distance from the sun is 5.9 billion km. The technology available at that time meant that even the best photographs of it hardly revealed anything. What's more, these six images – acquired in pairs over three nights in the month between April 13 and May 12 – were labelled as 'defective.' Odd blobs The reason why these pictures were labelled thus owed to the fact that they revealed Pluto to be oddly elongated. Viewing them under a microscope, Christy noticed that the fuzzy blob that was to be Pluto stretched in a northern direction in two of those pairs, while the final pair showed a southward direction. The defects were attributed either to atmospheric distortion or improper optical alignment in the telescope used for observations. After ruling out an explosion on Pluto as an unlikely explanation – especially as it lasted a month – Christy searched for other plausible reasons. There was a chance that Pluto itself was irregular in shape. Or could there be an unseen moon, even though one of his former professors, celebrated Dutch-American astronomer Gerard Kuiper, had searched for exactly the same decades earlier without any success? When Christy went over to the archives to check through older plates from 1965 onwards, there it was... the same elongation. What's more, all these images had also been dismissed as defective on every occasion. Correct conclusions Christy and Harrington, however, realised that they were onto something. By reviewing all the images with the elongations, they were able to state that the bulge occurred with a predictable frequency. This frequency of the unseen moon's orbital period – 6.4 Earth days – matched with what astronomers believed to be Pluto's rotational period, suggesting a synchronously locked binary system. The duo ruled out other possible reasons for the bulge and concluded correctly that Pluto had another companion at a distance of 19,640 km. The discovery of 'S/1978 P1' was announced by them through the International Astronomical Union (IAU) on July 7 and their findings were published in the Astronomical Journal. What started out as reviewing six defective images, served as the seeds for a whole new discovery. As Christy himself once pointed out, 'Discovery is where the scientist touches nature in its least predictable aspect.' What's in a name? As the discoverer, Christy wanted to exercise his rights for naming Pluto's companion. And he had his mind set on naming it after his wife. The Naval Observatory he worked for had suggested the name Persephone, the wife of Hades. Hades, the god of the underworld in Greek mythology, was the equivalent of the Roman god Pluto after which it is named. As luck would have it, Christy came across a reference to Charon, a boatman who ferried the dead across a river in the underworld to Hades. Charon's close mythical association with Hades, or Pluto, made it a great option for the newly discovered astronomical object. It was the perfect option for Christy as his wife's name was Charlene. In addition to sharing the first four letters, 'Char' was the nickname that friends and family used to call his wife. Just like how protons and electrons have the 'on' suffix, Christy saw Charon as 'Char' with the suffix 'on' and submitted his name. Eclipses and occultations By the time this name was accepted by IAU in January 1986, Pluto and Charon had a series of mutual eclipses and occultations. Studying them enabled astronomers in general, and Harrington in particular, to confirm the existence of Charon as he observed the eclipses and occultations to occur as predicted. Observing Pluto and Charon in this manner also enabled astronomers to arrive at Charon's diameter to be about 1,200 km, while also arriving at better estimates of the size and mass of Pluto. From a small dot in a photograph, Charon had become much much more – almost a world in its own right. It definitely meant the world to Christy in more ways than one, as he was also able to gift his wife the moon! Charlene Christy probably summed it the best when she said 'A lot of husbands promise their wives the moon, but Jim actually delivered.' Charon fact sheet Most of what we know about Charon, or even Pluto for that matter, is thanks to NASA's New Horizons mission. Approved in 2001 as the first flyby of Pluto and its largest moon Charon, it was launched in January 2006. This was months before IAU's decision in August the same year to demote Pluto's designation from a planet to a dwarf planet. Despite the fact that Pluto was plutoed, the mission went on, providing us invaluable information. Before New Horizons' closest approach to Pluto on July 14, 2015, the spacecraft captured plenty of images of Charon. While the images revealed a striking reddish north (top) polar region, Charon's colour palette wasn't as diverse as Pluto's. The origins of this red colouration is a mystery for now and no other icy object in the solar system sports a similar feature. Charon is 1,214 km across and is at a distance of 19,640 km from Pluto. As Pluto's equatorial diameter is about 2,377 km, Charon is nearly half the size of Pluto. This makes it the largest known satellite relative to its parent body for most astronomers. It is this same size, however, that forces other astronomers to consider Pluto and Charon as a double dwarf planet system. Charon's orbit takes 6.4 Earth days to go around Pluto. Charon neither rises or sets, however, but instead hovers near the same region on Pluto's surface. The same surfaces of Charon and Pluto always face each other due to a phenomenon called mutual tidal locking.
News18
a day ago
- News18
What's Holding Up Axiom Mission-4 As Launch Window Closes & Crew Waits? Explained
Last Updated: With a tight timeline, further delays in lift-off could disrupt pre-scheduled July missions carrying cargo and critical supplies to the ISS, pushing back AX-4 by months The launch window for the much-anticipated Axiom Mission-4 is rapidly closing as the crew remains on standby in Florida, while National Aeronautics and Space Administration (NASA) scrambles to complete the last-minute troubleshooting on the International Space Station (ISS). The lift-off – now postponed for the fifth time in three weeks – remains without a confirmed new date. Two days before the scheduled lift-off, NASA announced that it has again decided to stand down from a launch on June 22, and target a new launch date in the coming days. While the initial air leak in the ISS's Zvezda module has already been halted by the crew on-board, NASA said it needed 'additional time to evaluate the station after recent repair work". The space station currently has seven people on board as part of Expedition 73, with four docked spacecraft — two crew and two cargo. NASA's SpaceX Crew 11 mission is also in waiting as it also planned to dock into the ISS in July. However, NASA highlighted that the AX-4 crew including Group Captain Shubhanshu Shukla remains on standby and 'ready to launch when the station is ready to receive them", and it continues to review the launch opportunities along with Axiom Space and SpaceX. Axiom Mission-4 has faced a string of delays – from initial weather concerns to a last-minute liquid oxygen leak in the Falcon-9 booster that scrubbed the June 11 launch. While SpaceX has since resolved the issue, the latest setback stems from the ongoing repairs to the ISS's Zvezda module, which NASA and Roscosmos are currently addressing. The ISS was built like a Lego set, with each piece built in various countries around the world, then launched and assembled in space. Five partner agencies, Canada, Europe, Japan, NASA in the US and Russia's Roscosmos operate the ISS with each partner responsible for managing and controlling the hardware it provides. They continue to monitor it to ensure safe habitation for astronauts, carry out repairs and replacements. Over the last 25 years, ISS has hosted astronauts from multiple countries who live and work aboard it. Last week, cosmonauts aboard the ISS detected some air leaks in the back segment of ISS's Zvezda module during regular inspections. It is a core component of the Russian orbital segment, which acts as a primary living space, and provides life support. The air leak in the pressurised module was sealed immediately, but NASA said that it needs additional time to evaluate the ISS after recent repair work. 'Because of the space station's interconnected and interdependent systems, NASA wants to ensure that the station is ready for additional crew members, and it is taking that time to review data," it highlighted. The issue needs to be resolved and validated before any new spacecraft can dock with the ISS. CAN AXIOM MISSION-4 STILL MAKE IT TO ISS NOW? The tension is mounting on the space agencies, as the current launch window is available only till June 30. The lift-off possibilities are narrowing with each passing day, as it was originally designed to be a 14-day mission. There is limited time, considering further delay jeopardises the subsequent missions in July, including some carrying cargo or other essential supplies — a timeline for which is locked in months in advance. Also, ISS has limited docking ports which need to be available, especially for a private spaceflight lasting 14 days. Four ports are already occupied by spacecraft – two crew and two cargo. NASA's SpaceX Crew 11 mission is also in waiting as it also planned to dock into the ISS in July. The launch is also subject to the weather conditions at the launch site near Florida coast, as well as the ascent path of the rocket. Moreover, the four astronauts have been in quarantine for nearly three weeks, and the delay affects their mission readiness. Compounding the urgency are also the 60 carefully chosen science experiments for the 14-day mission, including the seven shortlisted by ISRO—all of which have a limited viability window. On the ground are additional challenges—technical, logistics, financial—which continue to put added strain on all space agencies involved. top videos View all ISRO, which has invested almost Rs 550 crore in this private spaceflight collaboration, has made it clear that it does not intend to take any chances. Riding on it are hopes and dreams of billions, as Gaganyaan astronaut-designate Group Captain Shubhanshu Shukla prepares to become the first Indian astronaut to enter the International Space Station. The commercial collaboration was designed so that it could provide him the necessary training and exposure in space, before India's Rs 20,000 crore Gaganyaan – maiden human spaceflight mission. ISRO Chairman Dr. V Narayanan remains stationed in Florida with his team to oversee mission readiness, and emphasised that 'safety and mission integrity remain India's top priorities". Get Latest Updates on Movies, Breaking News On India, World, Live Cricket Scores, And Stock Market Updates. Also Download the News18 App to stay updated! tags : Axiom Space nasa news18 specials Location : New Delhi, India, India First Published: June 21, 2025, 08:00 IST News explainers What's Holding Up Axiom Mission-4 As Launch Window Closes & Crew Waits? Explained
