What does Chandrayaan-3's journey to the Moon look like?

Chandrayaan-3 is the latest Moon mission by the Indian Space Research Organization - ISRO. The main objective of the project is to conduct a soft landing on the lunar surface, which is expected to happen after 40 days voyage.

Earlier in 2019, the lander of Chandrayaan-2 deviated from its original trajectory and suffered a hard landing on the Moon. The orbiter of Chandrayaan-2 is still circling the Moon and keeps sending important data.

The journey

Chandrayaan-3 was successfully launched from Srihari Kota on 14 July, 2023. The distance between Earth and Moon is nearly 384,000 kms which will be covered in 40 days. Choosing July for launch was deliberate as Earth and Moon are the closest this time of the year.

The propulsion module will carry the lander and rover set up to 100 km lunar orbit. Then, the lander and rover configuration will separate and aim for the Moon's surface. If soft landing is achieved, rover will enter the Moon.

Objectives

The main objective is to demonstrate soft landing and loitering capabilities of the rover. The other objective is to study the lunar surface and compile data of its composition. The rover is designed to conduct experiments with soil to understand which mineral resources are available on the Moon.

Apart from that, the rover on Chandrayaan-3 will also seek the presence of water ice on the Moon. Earlier India's Chandrayaan-1 had discovered water molecules at the lunar poles. This time the aim is to further study the history and geology of Moon's surface.

Design

The lander is box shaped with four standing legs. Inside the lander exist the rover and various instruments for experiment. Rover on Chandrayaan-3 is a small six wheeled vehicle that weighs 26 kg. The rover carries a drill, cameras and spectrometer.

Summing up

The chandrayaan-3 mission is expected to complete a soft landing on the south pole region of the Moon. Doing so, it will put behind the failure of Chandrayaan-2 lander in 2019. The rover on Chandrayaan-3 will not only help in understanding lunar surface composition but also know the evolution of solar system as it studies craters at the south pole.

First Images From NASA's Webb Telescope Revealed

First image (credit: NASA, ESA, CSA) by the Webb Telescope is of galaxy cluster SMACS 0723 as it appeared 4.6 billion years ago, the time when our planet Earth just began to form. Surrounding the cluster are tiny unseen objects of the universe as they were 13 billion years ago, shortly after the Big bang.

SMACS 0723, a massive object, is bending the light rays coming from the distant galaxies behind it. The Webb telescope has brought those galaxies into sharp focus. This phenomenon is called gravitational lensing and is based on Einstein's theory of relativity.

The image was taken by Webb's near-infrared camera and took about 12.5 hours to be assembled from a collection of images taken at various wavelengths. When the Hubble Space Telescope took a similar deep field image it took several weeks!

The first deep field was unveiled by the president of the United States Joe Biden during a White House event. “It’s hard to even fathom,” he commented.. “It’s astounding. It’s an historic moment for science and technology, for America and all of humanity.”

Thousands of galaxies that have come into Webb's infrared view for the first time would fit in a single grain of sand held at arm's length by someone on the ground. These images will help astronomers to calculate the compositions of the earliest galaxies.

The telescope, named after the longest serving NASA administrator, took over 30 years for completion and could revolutionize our understanding of the universe. Its infrared capabilities will allow humans to see back in time to the first galaxies and study their evolution.

Webb is the official successor of the Hubble space telescope. Its operations are led by NASA with its partners: ESA (European Space Agency) and CSA (Canadian Space Agency). The camera that took this image was built by the University of Arizona and Lockheed Martin’s Advanced Technology Center.

5 Major Differences Between Sgr A* and M87*

Take a close look at the two black hole images and you can ascertain a few differences by your own. Notice the speed of accretion disk, which is a gas-like flow around the black hole. Or the size of dark spots in the center that give you a faint idea of the black hole event horizon.

The latest image by event horizon telescope is that of Sagittarius A*, a black hole in the center of our Milky Way galaxy. That this is a supermassive black hole was first recognized by physicists Reinhard Genzel and Andrea Ghez, for which they won the Nobel Prize in 2020.

Event horizon telescope or EHT is a worldwide network of radio telescopes that took the first ever picture of a black hole in 2019. It was that of M87*, an enormous supermassive black hole in the heart of Messier 87 galaxy in the constellation Virgo.

While the two black hole pictures look almost similar, for the laws of physics that govern their behavior are the same, the new image is more exciting than before. For one, it is located in our neighborhood; and second, it was way too difficult to catch a glimpse of.

1. Schwarzschild radius: It is the size of the sphere from which even light will fail to escape. For supermassive M87* this is 18 billion km, four times the radius of our solar system! For Sgr A*, Schwarzschild radius is only 12 million km.

2. Relative size: Our black hole is 31 times wider than the Sun, as shown in the figure below. Whereas the black hole in Messier 87 is 27,000 times wider than the Sun. If Sgr A* was the size of a doughnut, then M87* would be the size of a football stadium.

3. Distance: Our neighborhood black hole Sagittarius A* is obviously closer, located 25,000 light years away from the earth. Whereas M87* is 55 million light years away! So if it took 1 hour to get to Sgr A*, then it would take 91 days to reach M87*.

Despite being closer, observing Sgr A* was more challenging than expected. Scientists had to look through the galactic plane and filter out the noise from intermediate stars and dust clouds in their data, collected across continents.

4. Mass: M87* is 6 billion times more massive than the Sun whereas Sgr A* weighs 4 million Suns. Thus, our black hole Sgr A* is 1500 lighter in comparison.

5. Speed: Around the black hole is a bright ring of materials that swirl at great velocities. The material disk of M87* rotates over a course of many days at roughly 1,000 km/s, while it takes only a few minutes for material to move around Sagittarius A* because it is much smaller.

Why is the picture of our black hole kind of blurry? One of the reasons is that we don't have a direct view of the object while sitting on one of the arms of the galaxy and secondly, its accretion disk is spinning very fast compared to M87* so it's like taking a picture of a toddler who cannot stand still.

Why James Webb Telescope Is Better Than Hubble

The James Webb space telescope (JWST) is named after the longest serving NASA administrator and is the official successor to the Hubble space telescope. JWST is the costliest astronomy project having spent nearly three decades in the making.

The largest and the most powerful telescope in the world is scheduled to be launched in December 2021 after many delays since completion. The JWST will be able to look back in time closer to the Big Bang than ever before.

Comparison

JWST was built by NASA in collaboration with European Space Agency and Canadian Space Agency. It will explore the universe in the infrared region, something that Hubble space telescope is incapable of doing. The mirror size is 6.5 meters - three times the size on the Hubble telescope but it weighs half of Hubble.

Protection

To make observations in the infrared part of the electromagnetic spectrum, JWST must be kept under 50K or −223°C which is extremely cold. It uses a cryocooler and a large five-layer sunshield to block light and heat from the Sun, Earth and Moon to maintain a stable temperature.

Mission

The objectives of JWST include detecting clues to the origins of the universe, like observing infant galaxies and their evolution. As well as locating earth like planets outside the solar system and study the origins of life.

Hubble space telescope is capable of observing events that happened in space some 500 million years after the Big Bang, whereas Webb telescope can go back even further to around 100 million years after that event.

Instruments

JWST has a near infrared camera for observation of faint extrasolar planets very close to the bright stars. It also has a near infrared spectrograph capable of measuring spectrum of faint stars and galaxies. A fine guidance sensor helps the telescope stay pointed at whatever it is commanded to look at.

Challenges

It was scheduled to launch before but accidental tears in the delicate sunshield in 2018 delayed the project. Controversy also erupted over naming of the telescope as activists alleged that James Webb had discriminated against LGBTQ scientists during his term.

The mirror in JWST will be folded before launch. It is made up of 18 hexagonal segments - shaped so to join without gaps in between them. The mirror will unfold after the launch and it will take at least two weeks before the telescope becomes operational in orbit.

How it works

When picture of a galaxy is taken we see it the way it was millions of years ago because light takes time to travel. It is like finding a picture of a child dated from 1900 but if that child was still alive, they would be among the oldest people on the planet.

As the light travels, it becomes red-shifted due to expansion of the universe. So, objects at extreme distances are easier to see in the infrared. We can see these objects the way they were millions of years ago, that is, when that galaxy was fairly young.

JWST's infrared capabilities will allow humans to see back in time to the first galaxies for the first time. Infrared astronomy will also help us to learn how stars and galaxies have evolved over time. By overcoming all the challenges, JWST is set to launch in December 2021.

Hawking's black hole theorem confirmed by gravitational waves

A black hole has often been portrayed as the ultimate villain in sci-fi movies due to its mysterious nature. From the death of a large-enough star it emerges with such a strong gravitational field that not even light can escape from within its grasp.

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However, in spite of its wildly mysterious behavior, the black hole obeys certain simple rules. One of those rules, first proposed in 1971 by English physicist Stephen Hawking, has been proven correct by the help of gravitational waves.

The area law, derived from Einstein's general relativity, states that it is impossible for a black hole to decrease in size, at least in the short term. Mathematically:

Recently, a team led by astrophysicist Maximiliano Isi from Massachusetts Institute of Technology studied the gravitational wave data released by the merger of two black holes.

Their calculations show that the total surface area of the resulting black hole is greater than the combined areas of the two smaller black holes. Therefore, Stephen Hawking was right.

However, while black holes cannot shrink according to Einstein's general relativity, they can do so as per the quantum mechanics.

Hawking worked that out too in 1974 – a concept known as Hawking radiation, which is predicted to emit because of strange quantum effects near the black hole's event horizon.

In his 1988 book A Brief History of Time, Hawking thus wrote: Black holes ain't so black. The release of these radiations would cause the black hole to shrink over longer time period and evaporate eventually.

Hence, theoretically speaking, both general relativity and quantum mechanics hold true. Maximiliano Isi said: "I am obsessed with these objects because of how paradoxical they are."

Now that the area law has been established for short to medium time frames, the researchers' next step would be to detect Hawking radiation by observing older black holes; no substantial evidence has been recorded so far.

Isi concludes: Black holes are those phenomena where gravity meets quantum mechanics, which makes them the perfect playgrounds for our understanding of reality.