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ISRO’s ambitious third Moon mission Chandrayaan-3’s Lander Module (LM) is all set to land on the lunar surface on Wednesday evening, as India eyes becoming the first country to reach the uncharted south pole of Earth’s only natural satellite. The LM comprising the lander (Vikram) and the rover (Pragyan), is scheduled to make a soft landing near the south polar region of the Moon at 6:04 pm on Wednesday.

If the Chandrayaan-3 mission succeeds in making a touchdown on the moon and in landing a robotic lunar rover in ISRO’s second attempt in four years, India will become the fourth country to master the technology of soft-landing on the lunar surface after the US, China and the erstwhile Soviet Union.

Chandrayaan-3 is a follow-on mission to Chandrayaan-2 and its objectives are to demonstrate safe and soft-landing on the lunar surface, roving on the Moon, and to conduct in-situ scientific experiments.

Chandrayaan-2 had failed in its lunar phase when its lander ‘Vikram’ crashed into the surface of the Moon following anomalies in the braking system in the lander while attempting a touchdown on September 7, 2019. Chandrayaan’s maiden mission was in 2008.

The Rs 600 crore Chandrayaan-3 mission was launched on July 14 onboard Launch Vehicle Mark-III (LVM-3) rocket, for a 41-day voyage to reach near the lunar south pole.

The soft-landing is being attempted days after Russia’s Luna-25 spacecraft crashed into the Moon after spinning out of control.

After the second and final deboosting operation on August 20, the LM is placed in a 25 km x 134 km orbit around the Moon.

The module would undergo internal checks and await the sun-rise at the designated landing site, ISRO has said, adding that the powered descent — to achieve a soft landing on the Moon’s surface — is expected to be initiated at around 5:45 pm on Wednesday.

The critical process of soft-landing has been dubbed by many including ISRO officials as “17 minutes of terror”, with the entire process being autonomous when the lander has to fire its engines at the right times and altitudes, use the right amount of fuel, and scan of the lunar surface for any obstacles or hills or craters before finally touching down.

After checking all the parameters and deciding to land, ISRO will upload all the required commands from its Indian Deep Space Network (IDSN) at Byalalu near here, to the LM, a couple of hours before the scheduled time touchdown.

According to ISRO officials, for landing, at around 30 km altitude, the lander enters the powered braking phase and begins to use its four thruster engines by “retro firing” them to reach the surface of the moon, by gradually reducing the speed. This is to ensure the lander doesn’t crash, as the Moon’s gravity will also be in play.

Noting that on reaching an altitude of around 6.8 km, only two engines will be used, shutting down the other two, aimed at giving the reverse thrust to the lander as it descends further, they said, then, on reaching an altitude of about 150-100 metres, the lander using its sensors and cameras, would scan the surface to check whether there are any obstacles and then start descending to make a soft-landing.

ISRO Chairman S Somanath had recently said the most critical part of the landing will be the process of reducing the velocity of the lander from 30km height to the final landing, and the ability to reorient the spacecraft from horizontal to vertical direction. “This is the trick we have to play here,” he said.

“The velocity at the starting of the landing process is almost 1.68 km per second, but (at) this speed (the lander) is horizontal to the surface of the Moon. The Chandrayaan-3 here is tilted almost 90 degrees, it has to become vertical. So, this whole process of turning from horizontal to vertical is a very interesting calculation mathematically. We have done a lot of simulations. It is here where we had the problem last time (Chandrayaan-2),” Somanath explained.

After the soft landing, the rover will descend from the lander’s belly, onto the Moon’s surface, using one of its side panels, which will act as a ramp.

The lander and rover will have a mission life of one lunar day (about 14 earth days) to study the surroundings there. However, ISRO officials do not rule out the possibility of them coming to life for another lunar day.

The lander will have the capability to soft-land at a specified lunar site and deploy the rover which will carry out in-situ chemical analysis of the lunar surface during the course of its mobility. The lander and the rover have scientific payloads to carry out experiments on the lunar surface.

“After powered descent onto the landing site, there will be deployment of ramp and rover coming out. After this, all the experiments will take place one after the other — all of which have to be completed in just one day on the moon, which is 14 days,” Somnath had said.

Stating that as long as the sun shines all the systems will have their power, he said, “The moment the sun sets, everything will be in pitch darkness, the temperature will go as down as low as minus 180-degree Celsius; so it is not possible for the systems to survive, and if it survives further, then we should be happy that once again it has come to life and we will be able to work on the system once again, and we hope like that to happen.” Polar regions of the moon are very different terrain due to the environment and the difficulties they present and therefore have remained unexplored. All the previous spacecraft to have reached the Moon landed in the equatorial region, a few degrees latitude north or south of the lunar equator.

The Moon’s south pole region is also being explored because there could be a possibility of the presence of water in permanently shadowed areas around it.

The LM has payloads including RAMBHA-LP which is to measure the near-surface plasma ions and electrons density and its changes, ChaSTE Chandra’s Surface Thermo Physical Experiment — to carry out the measurements of thermal properties of the lunar surface near-polar region– and ILSA (Instrument for Lunar Seismic Activity) to measure seismicity around the landing site and delineating the structure of the lunar crust and mantle. The rover, after the soft-landing, would ramp down the lander module and study the surface of the moon through its payload APXS – Alpha Particle X-Ray Spectrometer – to derive the chemical composition and infer mineralogical composition to further enhance understanding of the lunar surface.

The rover also has another payload Laser Induced Breakdown Spectroscope (LIBS) to determine the elemental composition of lunar soil and rocks around the lunar landing site.

Ahead of its scheduled landing on the moon, Chandrayaan-3’s LM has established two-way communication with Chandrayaan-2’s orbiter which continues to orbit around the Moon. The two-way contact potentially offers ground controllers (MOX-Mission Operations Complex in Bengaluru) more channels for communication with Chandrayaan-3.

The Chandrayaan-2 spacecraft comprising an orbiter, lander and rover was launched in 2019. The lander with a rover inside crashed into the moon’s surface, failing in its mission to achieve a soft landing. The ISRO had said that due to the precise launch and orbital manoeuvres, the mission life of the Ch-2 orbiter, which had separated from the lander and rover, is increased to seven years.

Somanath has said instead of a success-based design in Chandrayaan-2, the space agency opted for a failure-based design in Chandrayaan-3, focused on what can fail and how to protect it and ensure a successful landing.

“We looked at very many failures – sensor failure, engine failure, algorithm failure, calculation failure. So, whatever the failure we want it to land at the required speed and rate. So, there are different failure scenarios calculated and programmed inside.” The LM of Chandrayaan-3 successfully separated from the Propulsion Module on August 17, which was 35 days after the satellite was launched on July 14.

Meanwhile, the Propulsion Module, whose main function was to carry the Lander Module from launch vehicle injection to lander separation orbit, will continue its journey in the current orbit for months/years, the space agency said.

Apart from this, the Propulsion Module also has one scientific payload as a value addition. The SHAPE (Spectro-polarimetry of Habitable Planet Earth) payload onboard it, whose future discoveries of smaller planets in reflected light would allow us to probe into a variety of Exo-planets which would qualify for habitability (or for the presence of life).

Post its launch on July 14, Chandrayaan-3 entered into the lunar orbit on August 5, following which orbit reduction manoeuvres were carried out on the satellite on August 6, 9, 14 and 16, ahead of the separation of both its modules on August 17, in the run-up to the landing on August 23.

Earlier, over five moves in the three weeks since the July 14 launch, ISRO had lifted the Chandrayaan-3 spacecraft into orbits farther and farther away from the Earth.

Then, on August 1 in a key manoeuvre — a slingshot move — the spacecraft was sent successfully towards the Moon from Earth’s orbit. Following this trans-lunar injection, the Chandrayaan-3 spacecraft escaped from orbiting the Earth and began following a path that would take it to the vicinity of the moon. 


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Hubble finds missing globular cluster in Milky Way’s crowded stellar halo

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Hubble finds missing globular cluster in Milky Way’s crowded stellar halo

A striking new image captured by NASA’s Hubble Space Telescope has shed light on an underexplored gatekeeper of our galactic neighbours’ achievements and tragedies. Adorned with multi-hued stars, the spherical cluster glitters amid the expanse of stars in our Milky Way galaxy. This type of globular cluster is a very dense grouping of stars — about the same mass as 100,000 suns — that orbit all around the centre of their galaxy. Stars in a cluster are typically roughly the same age, as they formed from the same collapsing gas cloud. In this new view, stars show up in temperatures indicated in red and blue colours: red for colder and blue for hotter stars.

Hubble Maps Forgotten Star Cluster ESO 591-12 to Uncover Milky Way’s Ancient Stellar Secrets

As per a report from NASA’s Hubble team, ESO 591-12 was imaged during the Hubble Missing Globular Clusters Survey—an initiative targeting 34 Milky Way globular clusters that had never been observed by the space telescope. The aim is to construct a comprehensive database of the ages, distances, and stellar populations of all the galaxy’s known globular clusters and star formations. However, it has always been tough for telescopes on Earth to pick out individual stars in these densely populated regions, so Hubble’s high resolution has done much to finally be able to track the movements of stars to unlock their histories and formation.

The ESO 591-12 data are part of an ongoing study to improve knowledge of the formation and evolution of globular clusters in the galaxy’s bulge and halo. These star clusters are cosmic fossils that have preserved cosmic conditions from the primordial universe. Their work helps build a fuller narrative of the evolution of the Milky Way and how it has changed over billions of years.

This new image is a further example of how advanced space-based observing facilities are helping astronomers to excavate the contents of the dark and dusty skeleton cloaking the Milky Way and sculpt a better understanding of not only the universe’s evolution but also that of our cosmic home.
Each one tells part of the astronomical story, and Hubble is digging out new chapters to enrich the tale, such as probing data for clusters as much as ESO 591-12, which have been mostly neglected until now. This finding adds to our knowledge of the early universe by shining a spotlight on something that was in plain sight.

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Very Massive Stars Blow Away Outer Layers in Powerful Winds Before Black Hole Collapse

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Massive stars shed extreme mass before collapsing into black holes

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Massive stars shed extreme mass before collapsing into black holes

New research indicates that the most monstrously huge stars — those more than 100 times as massive as the sun — shed at least 20 times more matter before they collapse than previously thought to do so as they cool off to become black holes. These stars blow off a significant portion of their outer layers in quite powerful stellar winds over the brief but intense course of their lives, leaving behind low masses at the end. One benefit of this extreme mass loss is that it can account for observed strangeness in stars such as those in the Tarantula Nebula, providing new information on stellar evolution, black hole formation, and sources of gravitational waves.

Hurricane-like Stellar Winds Explain Extreme Mass Loss in Universe’s Most Massive Stars

As per a report from Space.com, researchers used sophisticated models and observations to learn that very massive stars give off winds so powerful they act more like hurricanes than gentle solar breezes. Their results agree very well with observations of WNh-type Wolf-Rayet stars in the Tarantula Nebula, which are hotter and more compact than would be expected by standard models. The improved models explain the very high temperatures at the surface and the stability of hydrogen, which address previous challenges.

One key subject in this study is R136a1 — the most massive known star — with a mass up to 230 times that of the sun. The researchers suggested that it either formed as a single star of around 200 solar masses or as a binary star system where the two stars had a combined mass of about 200 solar masses. In both such cases, the star must have lost a huge amount of mass early in its life, so the findings would call into question how it is that massive stars can live long enough to leave such a wreckage in the Large Magellanic Cloud.

The implications extend to black hole formation as well. More massive stellar winds erode more mass, resulting in the production of smaller black holes and decreasing the chances of creating elusive intermediate-mass black holes. This revision also enhances the matches of the model with the observed gravitational wave signal of a coalescing black hole binary.

Although the models are restricted to stars in the Tarantula Nebula, the researchers stress that in order for their findings to be considered universal, it is important to understand stars in different chemical environments as well. The results not only reshape predictions of black hole populations but may also adjust our understanding of how the most massive stars in the universe live — and die.

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New Interstellar Comet 3I/ATLAS Speeds Through Solar System

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Astronomers Capture First-Ever Image of a Dead Star That Exploded Twice in Rare Supernova Event

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Astronomers Capture First-Ever Image of a Dead Star That Exploded Twice in Rare Supernova Event

For the first time, a team of astronomers has captured a clear image of a white dwarf star that exploded not just once, but twice, as a Type Ia supernova — a “double-detonation” that scientists hadn’t thought possible until now. The extraordinary observation could revise our long-held notions of how stars die, suggesting that some stars can explode as supernovas without ever crossing the Chandrasekhar limit, the minimum mass normally thought necessary for such an explosion. The astronomers employed the Very Large Telescope’s MUSE instrument to zoom in on the four-century-old supernova remnant SNR 0509-67.5, which sits 60,000 light-years away in the constellation Dorado, revealing evidence of two separate blasting catastrophes in its construction.

First Visual Proof Shows White Dwarfs Can Explode Twice Without Reaching Chandrasekhar Limit

As the researchers report on July 2 in Nature Astronomy, the team found a distinctive “fingerprint” in the debris of SNR 0509-67.5 in the Large Magellanic Cloud that the models predicted. White dwarfs—which are the dead stage of sun-like stars—usually blow up into Type Ia supernovas after they hit the Chandrasekhar limit by stealing matter from a neighbouring star.

However, this finding shows that the detonation can be launched at an earlier time. The explosion is likely to have a two-step origin, the team argues, with the initial blast being generated when an unstable layer of helium that the star had acquired exploded on its surface; the resulting shock wave then drove a second and main detonation.

“This physical proof of a double-detonation not only helps solve a long-standing mystery of what causes these explosions, but it represents the most visually compelling evidence for this origin.” Priyam Das, University of New South Wales, team leader and author.

Something is happening to Type Ia supernovas, the “standard candles” used to measure cosmic distances, because their brightness doesn’t fluctuate. But they have long mystified scientists with how they explode. Until this discovery, an explosion white dwarf that didn’t surpass the Chandrasekhar limit was only considered in theory.

This fresh visual evidence for the double detonation model further informs our knowledge of stellar evolution and also informs how we should interpret light from distant supernovas. More than its scientific implications, its discovery adds a colourful new page to the story of dying stars — stars that, as it now appears, will not go gently into that night but will light up the sky twice over in fantastic fireworks before vanishing from the cosmos.

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