“I need No light up here!”- says India.
Is India developing a vampire land?! No, apparently, we are at an altitude of 14,764 ft! at the Hanle’s Space Observatory. Everything you need to know about the Hanle Observatory.
An article by the collective effort of Aditya Tiwari, Shlok Saxena and Shashwat Yadav, members of the Astronomy Club, IIT BHU.
History
In the late 1980s, a committee chaired by Prof. B. V. Sreekantan recommended that a large national optical telescope be prioritised. The search for the observatory site was taken up in 1992 under the leadership of Prof. Arvind Bhatnagar. The scientists from the IAO found the site at Hanle. The observatory's 2-metre telescope saw the first light on the midnight hour between 26 September and 27 September 2000.
Why Hanle?
The Hanle site is deemed to be excellent for visible, infrared and submillimeter observations throughout the year. Specifically, the observation conditions yield about 255 spectroscopic nights per year and approximately 190 photometric nights per year, and it falls in a rain shadow region. The Hanle region is known for its exceptionally clear skies and low light pollution, making it an excellent location for stargazing and astronomical observations. The absence of significant light sources in the surrounding area contributes to the relatively dark skies in Hanle. There are approximately 270 clear nights annually. The Bortle scale rating of Hanle Sky is 1, which is nearly the best rating possible for a clear night sky!
The high altitude of Hanle is another advantage. At this altitude, the observatory is above a significant portion of Earth’s atmosphere, which tends to blur and distort astronomical observations. This results in sharper and clearer images of celestial objects.
Dark Sky Reserve
A Dark Sky Reserve is a designated area that aims to preserve and protect the quality of its night skies by minimising light pollution. Dark Sky Reserves are typically located in areas with exceptional natural darkness and starry skies. And Hanle is the perfect area with less than 1000 people living in the village. It’s worth noting that the establishment of Dark Sky Reserves is a designation given by the International Dark-Sky Association (IDA).
The Hanle area of Leh preserve has restrictions ranging from indoor lights only, mandatory light-blocking curtains on windows and doors in houses, usage of only warm yellow lights (wavelength does not travel far) on streets, no high beam headlights on vehicles, no vehicle movement at night, etc.
The Hanle dark-sky preserve extends to the six hamlets of Hanle revenue villages — Bhok, Punguk, Dhado, Naga, Khuldo and the Tibetan Refugee area of Hanle that Changthang Wildlife Sanctuary in Changthang plateau. North, south, east and west four extremities of the preserve are between a distance of 19.6 km to 22 km from the observatory. The preserve stands in the North-South direction to a stretch of 19.6 km, and 22km on the perpendicular counterpart.
Home to World-Class Telescopes
The observatory hosts an impressive array of telescopes and instruments catering to various astronomy, astrophysics, and space science domains. One of the most notable telescopes is the Himalayan Chandra Telescope (HCT), which the Indian Institute of Astrophysics operates. The HCT is a 2-meter class optical-infrared telescope that has been instrumental in several groundbreaking discoveries, including studying variable stars, star-forming regions, and distant galaxies.
In addition to the HCT, the Gamma-Ray Astronomy Telescope (GREAT) is another key instrument at Hanle. GREAT contributes significantly to understanding these energetic phenomena and their role in shaping the universe. It unveils the explosive endings of massive stars, known as supernovae, and the dance of particles near black holes and pulsars. GREAT’s observations let us grasp the dynamic, energetic nature of the universe’s most extreme phenomena.
GREAT is actually a setup of total of 7 telescopes! Each telescope has seven mirrors with a total area of 4.4 square meters. The telescopes are deployed on the periphery of a circle of radius 50 meters with one telescope at the centre. The telescope has a 21-meter collector which can detect indirectly using atmospheric Cherenkov technique.
Indian Institute of Astrophysics (IIA) collaborates with the McDonnell Centre for the Space Sciences of Washington University in St. Louis to operate two 0.5 meters Cassegrain telescopes to monitor active galactic nuclei. There are two different observatories, one of them being Hanle. The facilities 180 degrees apart in longitude are together to be called the Antipodal Transient Observatory.
Interestingly, the energy region between the satellite experimentation (~ 10GeV) and the traditional Atmospheric Cerenkov experimentation (~250 GeV) has not yet been explored, apart from the fact that they are gamma rays. The only information that occurs naturally at former energies of 10GeV, is through astrophysical sources like AGNs, pulsars etc. And that of the latter energies of 250GeV is quite rare. Naturally exciting is the fact that the process of photon formation tends to cease, and hence interesting information is thus anticipated about these sources! To study their properties, there are essentially two methods for atmospheric Cerenkov experiments to reach lower energy thresholds, based on the concept of collecting the Cerenkov photons using the telescopes. While the first suggests using very large size telescopes to collect a meagre amount of Cerenkov photons at these energies, whereas the second method is to conduct experiments at very high altitudes where the number of Cerenkov photons is high enough to allow the use of smaller telescopes still.
Yup, I see that you have guessed where this is going!
IIA, in collaboration with TIFR, has taken the second approach and has started work on a gamma ray experiment, the high energy gamma-ray telescope (HAGAR), to be conducted at Hanle, which will address this exciting energy range.
Pioneering Discoveries
The Hanle Observatory has etched its name in the annals of scientific history. It has contributed significantly to our understanding of the universe’s building blocks, such as the cosmic microwave background radiation-a faint echo of the Big Bang that birthed our cosmos. This observatory has been a cradle for insights into the interstellar medium, the clouds of gas and dust that birth stars, and exoplanets — worlds beyond our solar system that may harbour the secrets of life.
Challenges
Operating an observatory at such a high altitude and remote location presents its own set of challenges. Blizzards, freezing temperatures, and logistical challenges test the mettle of the teams that keep the instruments running. Yet, their determination and ingenuity persist, underscoring the human spirit’s ceaseless quest for knowledge.
Future aspects
The Hanle Observatory’s future is set to amplify its impact on astronomical exploration. It will expand its capabilities by embracing multi-wavelength observations, including radio, X-ray, and neutrino instruments. With a focus on exoplanet research, specialized tools will decipher distant worlds' atmospheres and potential habitability. The observatory’s potential for dark matter investigations will emerge through hosting experiments and collaboration with global detectors. Further collaborations with gravitational wave observatories will provide insights into cosmic events. Public engagement, advanced data processing techniques, and international partnerships will enhance Hanle’s role as a frontier of innovation and discovery.
How can I visit?
The Hanle’s space observatory, formally called the Indian Astronomy Observatory (IAO) stands on Mt. Saraswati, Digpa-ratsa Ri, Hanle, in south-eastern Ladakh Union territory of India. It is a high-altitude astronomical station operated by the Indian Institute of Astrophysics (IAO). It is India’s first dark sky preserve! Accessing the observatory near the Chinese border (Line of Actual Control) requires a 250 km long ten-hour drive from Leh City. Hanle is a protected area, so you must get the Inner Line Permit from Leh's Deputy Commissioner’s Office. There are impositions on outdoor lighting and high beam vehicle headlights, for minimizing light pollution.
Astro tourism in Hanle
Astro tourism in Hanle has become a captivating destination for stargazing and celestial observations. As it boasts high altitudes and minimal light pollution, creating an ideal environment for astrophotography and stargazing enthusiasts. The observatory adds to the appeal, allowing visitors to engage in celestial observations under pristine skies. Travellers are drawn to Hanle to witness breathtaking views of the Milky Way, constellations, and other celestial phenomena that are often obscured in urban settings. The village’s remoteness and elevation contribute to its clear, unpolluted skies, providing an immersive experience of the universe's wonders. As Astro tourism gains momentum, efforts are being made to promote sustainable practices that minimize environmental impact and preserve natural nightscapes. Hanle has become a unique destination that marries astronomy, cultural experiences, and natural beauty, offering visitors a chance to connect with the cosmos in an unparalleled setting.
A Cosmic Inspiration
Beyond its contributions to scientific advancement, the Hanle Observatory inspires wonder and awe. Its location paints the perfect backdrop for contemplating our place in the cosmos. It encourages us to look beyond the mundane and peer into the vastness of space, inviting us to question, dream, and seek answers.
Concluding it we can say that the Hanle observatory stands as a beacon of human curiosity and ingenuity, nestled in the serene yet challenging landscape of the Himalayas. From its high-altitude perch, it peers into the mysteries of the universe, unveiling secrets hidden among the stars. As technology advances and our thirst for knowledge continues to grow, the observatory’s role in unravelling the cosmos will remain undiminished, inspiring generations to gaze upward and ponder the infinite expanse that lies beyond our world.
Conclusion
Hanle’s Observatory is finally its people’s observatory. India’s space ambitions rely on its people. There are many other observatories in India, like Udaipur Solar Observatory, Madras Observatory, and Chennai; but Hanle is special due to its unique location and altitude, and hence sits back in Kashmir like the Crown of the space industry of India. All that is required is for genius minds like you to visit Hanle and see the future beyond with your open eyes! Do tell us in the comments what ambitions you see in your life, and how you like our own Hanle’s observatory!!
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