Category Exploring the Universe

Membrane mirrors for large space-based telescopes?

Researches create lightweight flexible mirrors that can be rolled up during launch and reshaped precisely after deployment.

Mirrors are a significant part of telescopes. When it comes to space telescopes, which have complicated procedures for launching and deploying, the primary mirrors add considerable heft, contributing to packaging difficulties.

Researchers have now come up with a novel way of producing and shaping large, high-quality mirrors. These mirrors are not only thinner than the primary mirrors usually employed in space-based telescopes, but are also flexible enough to be rolled up and stored inside a launch vehicle.

Parabolic membrane mirror

The successful fabrication of such parabolic membrane mirror prototypes up to 30 cm in diameter have been reported in the Optica Publishing Group journal Applied Optics in April. Researchers not only believe that these mirrors could be scaled up to the sizes required in future space telescopes, but have also developed a heat-based method to correct imperfections that will occur during the unfolding process.

Using a chemical vapour deposition process that is commonly used to apply coatings (like the ones that make electronics water-resistant), a parabolic membrane mirror was created for the first time. The mirror was built with the optical qualities required for use in telescopes. A rotating container with a small amount of liquid was added to the inside of a vacuum chamber in order to create the exact shape necessary for a telescope mirror. The liquid forms a perfect parabolic shape onto which a polymer can grow during chemical vapour deposition, forming the mirror base. A reflective metal layer is applied to the top when the polymer is thick enough, and the liquid is then washed away.

Thermal technique

The researchers tested their technique by building a 30-cm-diameter membrane mirror in a vacuum deposition chamber. While the thin and lightweight mirror thus constructed can be folded during the trip to space, it would be nearly impossible to get it into perfect parabolic shape after unpacking. The researchers were able to show that their thermal radiative adaptive shaping method worked well to reshape the membrane mirror.

Future research is aimed at applying more sophisticated adaptive control to find out not only how well the final surface can be shaped, but also how much distortion can be tolerated initially. Additionally, there are also plans to create a metre-sized deposition chamber that would enable studying the surface structure along with packaging unfolding processes for a large-scale primary mirror.

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Why isn’t there an sound in space?

“In space, no one can hear you scream.” You may have heard this saying. It’s the tag line from the famous 1979 science fiction movie “Alien.” It’s a scary thought, but is it true? The simple answer is yes, no one can hear you scream in space because there is no sound or echo in space. I’m a professor of astronomy, which means I study space and how it works. Space is silent – for the most part.

How sound works

To understand why there’s no sound in space, first consider how sound works. Sound is a wave of energy that moves through a solid, a liquid or a gas. Sound is a compression wave. The energy created when your vocal cords vibrate slightly compresses the air in your throat, and the compressed energy travels outward.

A good analogy for sound is a slinky toy. If you stretch out a Slinky and push hard on one end, a compression wave travels down the Slinky. When you talk, your vocal cords vibrate. They jostle air molecules in your throat above your vocal cords, which in turn jostle or bump into their neighbours, causing a sound to come out of your mouth.

Sound moves through air the same way it moves through your throat. Air molecules near your mouth bump into their neighbours, which in turn bump into their neighbours, and the sound moves through the air. The sound wave travels quickly, about 1,223 kilometres per hour, which is faster than a commercial jet

 Sound in the solar system

Scientists have wondered how human voices would sound on our nearest neighbouring planets. Venus and Mars. This experiment is hypothetical because Mars is usually below freezing, and its atmosphere is thin. unbreathable carbon dioxide. Venus is even worse – its air is hot enough to melt lead, with a thick carbon dioxide atmosphere.

On Mars, your voice would sound tinny and hollow, like the sound of a piccolo On Venus, the pitch of your voice would be much deeper, like the sound of a booming bass guitar.The reason is the thickness of the atmosphere. On mars the thin air creates a high-pitched sound,and on venus the thick air creates a low-pitched sound. The team that worked this out simulated other solar system sounds, like waterfall on saturn’s moon titan.

Deep space sounds

While space is a good enough vacuum that normal sound can’t travel through it, it’s actually not a perfect vacuum, and it does have some particles floating through it. Beyond the Earth and its atmosphere, there are five particles in a typical cubic centimetre – the volume of a sugar cube- that are mostly hydrogen atoms.

By contrast, the air you are breathing is 10 billion billion (1019) times more dense. The density goes down with distance from the Sun, and in the space between stars there are 0.1 particles per cubic centimetre. In vast voids between galaxies, it is a million times lower still fantastically empty.

The voids of space are kept very hot by radiation from stars. The very spread-out matter found there is in a physical state called a plasma. A plasma is a gas in which electrons are separated from protons. In a plasma, the physics of sound waves get complicated. Waves travel much faster in this low-density medium, and their wavelength is much longer.

In 2022, NASA released a spectacular example of sound in space. It used X-ray data to make an audible recording that represents the way a massive black hole stirs up plasma in the Perseus galaxy cluster, 250 million light years from Earth. The black hole itself emits no sound, but the diffuse plasma around it carries very long wavelength sound waves.

The natural sound is far too low a frequency for the human ear to hear, 57 octaves below middle C which is the middle note on a piano middle of the range of sound people can hear. But after raising the frequency to the audible range, the result is chilling – it’s the sound of a black hole growling in deep space.

Space is a vacuum

So what about in space? Space is a vacuum, which means it contains almost no matter. The word vacuum comes from the Latin word for empty. Sound is carried by atoms and molecules, In space, with no atoms or molecules to carry a sound wave, there’s no sound. There’s nothing to get in sound’s way out in space, but there’s nothing to carry it, so it doesn’t travel at all. No sound also means no echo. An echo happens when a sound wave hits a hard, flat surface and bounces back in the direction it came from By the way, if you were caught in space outside your spacecraft with no spacesuit, the fact that no one could hear your cry for help is the least of your problems. Any air you still had in your lungs would expand because it was at higher pressure than the vacuum outside. Your lungs would rupture. In a mere 10 to 15 seconds, you’d be unconscious due to a lack of oxygen.

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What is the mysterious object in the James Webb telescope?

A team of international astrophysicists has discovered many mysterious objects that were hidden in images from the James Webb Space Telescope. These include six potential galaxies that should have emerged so early in the history of the universe and are so massive that they should not be possible under current cosmological theory.

These candidate galaxies may have existed roughly 500 to 700 million years after the Big Bang. That places them at more than 13 billion years ago, close to the dawn of the universe. Containing nearly as many stars as the modern-day Milky Way, they are also gigantic. The results of the study have been published in the journal Nature in February

Not the earliest discovered

 Launched in December 2021, the James Webb Space Telescope is the most powerful telescope ever sent into space by us. The candidate galaxies identified this time from its data, however, aren’t the earliest galaxies observed by Jams Webb. Another group of scientists spotted four galaxies observed that likely formed 350 million years after the Big band. Those galaxies, however, were nowhere as massive as the current findings.

While looking at a stamp-sized section of an image that looked deep into a patch of sky close to the Big Dipper (a constellation, also known as the Plough), a researcher spotted fuzzy dots that were way too bright and red. In astronomy, red light usually equals old light. As the universe expands the light emitted by celestial objects stretches, making it redder to human instruments.

Based on their calculations, the team was also able to suggest that the candidate galaxies they had discovered were also huge. Containing tens to hundreds of billions of sun-sized stars worth of mass, these were akin to our Milky Way.

Might rewrite astronomy books

As current theory suggests that there shouldn't have been enough normal matter at that time to form so many stars so quickly, proving it might rewrite astronomy books. And even if these aren't galaxies, then another possibility is that they are a different kind of celestial object, making them interesting.

For now, the discovery has piqued the interest of the researchers and the astronomical community. More data and information about these mysterious objects from James Webb is what is being sought after to confirm that these candidate galaxies are actually as big as they look, and date as far back in time.

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How about learning a bit about the stellar world?

Every star is a giant, bright ball of hot gas. Ever wondered how the stars form and how they die eventually? How about learning a bit about the stellar world?

One septillion stars, that’s almost the number of stars estimated to exist in our universe, Our Milky Way alone contains more than 100 billion stars. The nearest star to us is our Sun. Every star is a giant ball of hot gas. They are the building block of galaxies. “We are made of star stuff,” said noted astronomer Carl Sagan. It means that whatever we are composed of whatever our physical bodies are made of the raw materials that make up our physical bodies were created from the matter from long-extinguished stars. How about learning a bit about the stellar world?

Stars and their birth

Stars are made of huge balls of hot gas it is largely composed of hydrogen and small parts of helium and a few other elements. The star is held together because of its own gravity.

Every star goes through its own unique life cycle. Stars are born within hinge clouds of dust and gas called molecular clouds and are scattered throughout the galaxies. The gas in the molecular clouds clump together, forming high-density pockets, and often collide with each other. With each collision, more matter gets added to it and its mass grows. The gravitational force becomes stronger. The clumps of gas and dust then collapse under their own gravitational attraction. As this happens, the material heats up because of the friction and leads to the formation of a protostar which is also called the baby star. The set of stars newly formed from molecular clouds are called stellar clusters.

Life of a star

The energy of a protostar is derived from the heat released by its initial collapse. As years pass by, the high pressure and temperature inside the core of the star lead to a nuclear fusion reaction, where the nuclei of hydrogen atoms combine together to form helium. The energy that gets released post-nuclear fusion is enough to prevent it from collapsing under gravity.

At any time, there are two opposing forces acting on a star that prevent it from collapsing. There is the gravity of the star which tries to shrink the star, while the energy released following the nuclear fusion in the stars core leads to outward pressure. This outward push will resist gravity’s inward squeeze.

When a star is in the phase of undergoing a nuclear fusion reaction, it is called a main sequence star. This is also the longest phase of the star’s life. It has to be noted that as time passes, that is over millions of years, the size, luminosity and temperature of the star also change. The gas in the star is its fuel and its mass determines how long the star will live. This is because a massive star will end up burning a lot of fuel at a higher rate to generate enough energy to prevent it from collapsing: Meanwhile, lower mass stars will burn longer and shine for longer periods, some trillions of years whilst the massive ones may live for just about a few million years.

How does a star die?

When the star runs out of hydrogen to convert into helium, it marks the beginning of the end of the star’s life. Its core collapses leading to the death of the star. A star’s death is largely dependent on its mass. In the case of a lower-mass star, its atmosphere will keep on expanding until it becomes a giant star and the helium gets converted into carbon in its core. Over time the outer layers of the star will get blown off and the cloud of gas and dust expands. This expanding cloud is called a planetary nebula. All that is left now is the core. This is called a white dwarf star which will cool off over the following billions of years.

But what happens in the case of a high-mass star? The fusion leads to the conversion of carbon into heavier elements which then fuel the core. This process produces enough energy to prevent the core from collapsing. This goes on for a few million years until the star runs out of fuel. This is followed by a supernova explosion. The core either becomes a neutron star or a black hole

The supernova explosion is the biggest explosion that occurs in space. It releases material into the cosmos and this matter will then form part of the future molecular clouds and thereby become part of the stars.

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What has the Cassini spacecraft discovered about Saturn?

Saturn’s moon now satisfies what is usually considered the strictest requirement for life

The search for extraterrestrial life is now more serious than probably ever before. And the search just got more exciting with a team of scientists discovering new evidence that the subsurface ocean of Enceladus – Saturn’s moon- contains a key building block for life phosphorus.

The Cassini spacecraft explored Saturn and its system of rings and moons for more than 13 years. Based on data obtained from this mission, the research team directly found phosphorus in the form of phosphates originating from the ice-covered global ocean on the moon. The results were published in the journal Nature in June.

Our fate and phosphates

In the form of phosphates, phosphorus is necessary for all life on Earth. Be it the creation of DNA and RNA, or the bones and teeth in animals and human beings, life as it is today is impossible without phosphates.

Once the Cassini spacecraft discovered the subsurface liquid water on Saturn’s moon Enceladus, it then analysed samples of ice grains and gases erupting from cracks on Enceladus’ surface. When salt-rich ice grains were analysed by Cassini’s Cosmic Dust Analyzer, it showed the presence of sodium phosphates.

Life beyond Earth

The team’s observational results along with laboratory analogue experiments thus suggest that phosphorus is readily available in Enceladus as phosphates. This makes the discovery a major step forward in the search for life beyond our own Earth.

While worlds like our Earth with surface oceans have to reside in a narrow range of distances from their host stars (to maintain temperatures that support surface water), interior ocean worlds can occur over a large range of distances. This is true within our solar system and beyond. The presence of phosphates in Enceladus thereby increases the number of habitable worlds potentially possible across the galaxy.

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What’s the great Attractor?

In the depths of the cosmic ocean, there is a strange force that keeps pulling our galaxy towards it. And inevitably, whatever is near our Milky Way, including nearby galaxies, are being drawn towards this unknown force.

But for the longest time, we couldn’t understand what was the cause of this force or what lay here as this portion of the universe where the attraction is being felt is hidden from our view all thanks to our own galaxy. The force that is pulling the Milky Way lies in the direction of the constellation Centaurus. And the Milky Way’s disk blocks out our view here.

This region, which we can’t look through (with telescopes) from our galaxy, has been called the Zone of Avoidance. And the Great Attractor sits right here, at this 20% of the universe that’s shielded from us.

The only way to get a glimpse of this area is by using X-rays and infrared light.

It was in the 1970s that the Great Attractor was first discovered. It happened when astronomers made detailed maps of the Cosmic Microwave Background (that is, the light left over from the early universe). It was observed that one side of the Milky Way was warmer than the other.

This indicated that the galaxy was vigorously moving through space. The speed was observed to be about 370 miles per second (600 km/s). While astronomers could measure the high speed at which the galaxy was moving, they couldn’t explain its cause or origin.

The Great Attractor is a region of great mass that exerts an immense gravitational pull on our galaxy and surrounding galaxies. It is estimated to have a diameter of about 300 million light-years. It is estimated to be between 150 and 250 million light years away from Earth.

It sits at the centre of a local Supercluster known as the Laniakea Supercluster.

In short, the Great Attractor is the gravitational centre of the Laniakea Supercluster which consists of our galaxy and 100,000 others.

It is not a celestial body, but rather a point in the universe where everything gets attracted to.

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