My Science School

The white dwarf consists of an exotic stew of helium, carbon, and oxygen nuclei swimming in a sea of highly energetic electrons. The combined pressure of the electrons holds up the white dwarf, preventing further collapse towards an even stranger entity like a neutron star or black hole.

The white dwarf now has before it a long, quiet future. As the trapped heat trickles out, it slowly cools and dims. Eventually it will become an inert lump of carbon and oxygen floating invisibly in space: a black dwarf. But the universe isn’t old enough for any black dwarfs to have formed. The first white dwarfs born in the earliest generations of stars are still, 14 billion years later, cooling off. The coolest white dwarfs we know of, with temperature around 4,000 degrees Celsius (7,000 degrees Fahrenheit), may also be some of the oldest relics in the cosmos.

But not all white dwarfs go quietly into the night. White dwarfs that orbit other stars lead to highly explosive phenomena. The white dwarf starts things off by siphoning gas off its companion. Hydrogen is transferred across a gaseous bridge and spilled onto the white dwarf’s surface. As the hydrogen accumulates, its temperature and density reach a flash point where the entire shell of newly acquired fuel violently fuses releasing a tremendous amount of energy. This flash, called a nova, causes the white dwarf to briefly flare with the brilliance of 50,000 suns and then slowly fade back into obscurity.

White dwarfs – the cores left behind after a star has exhausted its fuel supply – are sprinkled throughout every galaxy. Like a stellar graveyard, they are the tombstones of nearly every star that lived and died. Once the sites of stellar furnaces where new atoms were forged, these ancient stars have been repurposed as an astronomer’s tool that have upended our understanding of the evolution of the universe.

Credit : Earth Sky 

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The first woman to travel into space was a Soviet cosmonaut named Valentina Tereshkova. She traveled around Earth 48 times while orbiting in the Vostok 6 spacecraft in 1963. The first American woman to travel into space was Sally Ride who rode onboard the space shuttle Challenger in 1983 and 1984.

Born in the village of Maslennikovo northeast of Moscow, Tereshkova volunteered for the Soviet cosmonaut program after Yuri Gagarin made history as the first man to fly in space on April 12, 1961. She was not a pilot, but had extensive parachuting experience, with 126 jumps under her belt. (Gagarin parachuted to Earth, ejecting from the Vostok capsule during descent as part of the landing sequence.)

Tereshkova was one of four women who received 18 months of training for Vostok 6, and was ultimately selected to pilot the flight. The mission launched from Baikonur Cosmodrome two days after Vostok 5, piloted by cosmonaut Valeriy Bykovsky, with the two spacecraft's coming within 3 miles (5 kilometers) of each other. 

Tereshkova spent 70 hours in space and orbited Earth 48 times during her mission. Though an icon of Soviet space exploration, she never flew in space again and became a test pilot and instructor.

Credit : Space.com

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Yuri Gagarin was the first person to fly in space. His flight, on April 12, 1961, lasted 108 minutes as he circled the Earth for a little more than one orbit in the Soviet Union's Vostok spacecraft. Following the flight, Gagarin became a cultural hero in the Soviet Union. Even today, more than six decades after the historic flight, Gagarin is widely celebrated in Russian space museums, with numerous artifacts, busts and statues displayed in his honor. His remains are buried at the Kremlin in Moscow, and part of his spacecraft is on display at the RKK Energiya museum.

Gagarin's flight came at a time when the United States and the Soviet Union were competing for technological supremacy in space. The Soviet Union had already sent the first artificial satellite, called Sputnik, into space in October 1957.

Before Gagarin's mission, the Soviets sent a test flight into space using a prototype of the Vostok spacecraft. During this flight, they sent a life-size dummy called Ivan Ivanovich and a dog named Zvezdochka into space. After the test flight, the Soviet's considered the vessel fit to take a human into space.

Credit : Space.com

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The Imaging Infrared Spectrometer (IIRS) instrument onboard the Chandrayaan-2 lunar orbiter has confirmed the presence of both hydroxyl ions (OH) and water molecules (H2O) on the surface of the moon.

It has further quantified the amount of water molecules present on the lunar surface regions it imaged, and distinguished parts of the moon that are water-rich from those that are scant in hydration.

Researchers used the data obtained by the Chandrayaan-2 orbiter's imaging infrared spectrometer (IIRS), an instrument that collects information from the Moon's electromagnetic spectrum, to understand the mineral composition of the satellite. They analysed data from three strips on the Chandrayaan-2 IIRS sensor for hydration, which led to "unambiguous detection of OH (hydroxyl) and H2O (water) signatures."

The research findings, published in the journal Current Science, state that hydration absorption was observed at all latitudes and surface types in varying degrees. "The initial data analysis from IIRS clearly demonstrates the presence of widespread lunar hydration and unambiguous detection of OH and H2O signatures on the Moon between 29 degrees north and 62 degrees north latitude," researchers said.

It was also observed from the data that the brighter sunlit highland regions at higher latitudes of the Moon were found to have higher hydroxyl or possibly water molecules. Scientists at the Indian Institute of Remote Sensing (IIRS) in Dehradun opine that the formation of hydroxyl and water on the Moon is due to space weathering, a process of interaction of solar winds with the lunar surface. This combined with impact events lead to chemical changes that further triggered the formation of reactive hydroxyl molecules.

Credit : India Today 

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Mars' moons are among the smallest in the solar system. Phobos is a bit larger than Deimos, and orbits only 3,700 miles (6,000 kilometers) above the Martian surface. No known moon orbits closer to its planet. It whips around Mars three times a day, while the more distant Deimos takes 30 hours for each orbit. Phobos is gradually spiraling inward, drawing about six feet (1.8 meters) closer to the planet each century. Within 50 million years, it will either crash into Mars or break up and form a ring around the planet.

To someone standing on the Mars-facing side of Phobos, Mars would take up a large part of the sky. And people may one day do just that. Scientists have discussed the possibility of using one of the Martian moons as a base from which astronauts could observe the Red Planet and launch robots to its surface, while shielded by miles of rock from cosmic rays and solar radiation for nearly two-thirds of every orbit.

Like Earth's Moon, Phobos and Deimos always present the same face to their planet. Both are lumpy, heavily-cratered and covered in dust and loose rocks. They are among the darker objects in the solar system. The moons appear to be made of carbon-rich rock mixed with ice and may be captured asteroids.

Phobos has only 1/1,000th as much gravitational pull as Earth. A 150-pound (68 kilogram) person would weigh two ounces (68 grams) there. Yet NASA's Mars Global Surveyor has shown evidence of landslides, and of boulders and dust that fell back down to the surface after being blasted off the moon by meteorites.

Credit : NASA Science 

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Even though Mercury is the closest planet to the Sun, Venus is the hottest planet in our solar system. This is because Mercury has almost no atmosphere, while Venus has a very thick atmosphere. This causes all the heat to be radiated back into space on Mercury. However, the heat is trapped on Venus, with the average temperature being 462°C.

The degree of hotness of a planet does not depend on as much on closeness to the Sun as on its atmosphere. Carbon dioxide has the tendency to absorb heat which in turn increases the temperature.

Mercury's atmosphere does not contain carbon dioxide (because of which all the heat is returned to space). Venus contains a high percentage of carbon dioxide due to which it is hottest planet.

In ancient times, Venus was often thought to be two different stars, the evening star and the morning star — that is, the ones that first appeared at sunset and sunrise. In Latin, they were respectively known as Vesper and Lucifer. In Christian times, Lucifer, or "light-bringer," became known as the name of Satan before his fall. However, further observations of Venus in the space age show a very hellish environment. This makes Venus a very difficult planet to observe from up close, because spacecraft do not survive long on its surface.

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Planet Mercury actually has no moons. Up first are Mercury and Venus. Neither of them has a moon.

Because Mercury is so close to the Sun and its gravity, it wouldn’t be able to hold on to its own moon. Any moon would most likely crash into Mercury or maybe go into orbit around the Sun and eventually get pulled into it.

If moons are such a common feature in the Solar System, why is it that Mercury has none? Yes, if one were to ask how many satellites the planet closest to our Sun has, that would be the short answer. But answering it more thoroughly requires that we examine the process through which other planets acquired their moons, and seeing how these apply (or fail to apply) to Mercury.

To break it all down, there are three ways in which a body can acquire a natural satellite. These causes have been determined thanks to many decades of astronomers and physicists studying the various moons of the Solar System, and learning about their orbits and compositions. As a result, our scientists have a good idea of where these satellites came from and how they came to orbit their respective planets.

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Mercury, Latin Mercurius, in Roman religion, god of shopkeepers and merchants, travelers and transporters of goods, and thieves and tricksters. He is commonly identified with the Greek Hermes, the fleet-footed messenger of the gods.

The cult of Mercury is ancient, and tradition has it that his temple on the Aventine Hill in Rome was dedicated in 495 BCE. There Mercury was associated with Maia, who became identified as his mother through her association with the Greek Maia, one of the Pleiades, who was the mother of Hermes by Zeus; likewise, because of that Greek connection, Mercury was considered the son of Jupiter. Both Mercury and Maia were honoured in the Mercuralia festival on May 15, the dedication day of Mercury’s temple on the Aventine.

Mercury is sometimes represented as holding a purse, symbolic of his business functions. Artists, like followers of Roman religion themselves, freely borrowed the attributes of Hermes and portrayed Mercury also wearing winged sandals or a winged cap and carrying a caduceus (staff).

Credit : Britannica 

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All of the planets in our Solar System have had a lot of craters. This was especially true in the past when there were many more asteroids traveling in our solar system than there are today. On planets like Venus, Earth, and Mars, we do not see as many craters because most of them have been eroded away by wind, rain, volcanic activity, and other forces. On the giant gas planets, Jupiter, Saturn, Uranus, and Neptune, we do not see any craters because there is no visible solid surface for the meteors to hit. On Mercury, where there is no atmosphere, there is no weather to erode away the craters, so most of the craters are still visible.

Craters are the most widespread landforms in the solar system. Craters are found on all of the terrestrial planets—Mercury, Venus, Earth and Mars. The surfaces of asteroids and the rocky, ice covered moons of the outer gas planets are cratered as well. The craters left by impacting objects can reveal information about the age of a planet's surface and the nature and composition of the planet's surface at the time the crater was formed.

Impact craters dominate the surfaces of Mercury and the Earth's Moon. Both bodies lack liquid water on their surfaces that would erode impact craters over time. They also lack an atmosphere which, on planets like the Earth and Venus, could disintegrate meteoroids before they impact the surface. However, old craters can be eroded by new impact events. Mercury and the Moon have very old surfaces. One of the youngest large craters on the Moon is Tycho, which was formed about 109 million years ago.

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The smallest planet in our solar system and nearest to the Sun, Mercury is only slightly larger than Earth's Moon.

From the surface of Mercury, the Sun would appear more than three times as large as it does when viewed from Earth, and the sunlight would be as much as seven times brighter. Despite its proximity to the Sun, Mercury is not the hottest planet in our solar system – that title belongs to nearby Venus, thanks to its dense atmosphere.

Because of Mercury's elliptical – egg-shaped – orbit, and sluggish rotation, the Sun appears to rise briefly, set, and rise again from some parts of the planet's surface. The same thing happens in reverse at sunset.

Credit : NASA Science 

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A European Mars orbiter has found water ice in the heart of the Valles Marineris canyon system- an area about the size of the Netherlands

• Water ice may be lying just centimetres below the Martian surface at one of the planet's most well known sites the Valles Marineris, a huge 3.000-km-long canyon system located along the equator of Mars.
• Ten times longer and five times deeper than the Grand Canyon on Earth, the Valles Marineris is named after NASA's Mariner 9 Mars orbiter, which discovered it in 1971.
• Now, 50 years later, the ESA's ExoMars Trace Gas Orbiter has identified vast amounts of hydrogen in the soil's upper surface layers at the centre of the canyon.
• Alexey Malakhov, a senior scientist at the Space Research Institute of the Russian Academy of Sciences and one of the nine authors of a new paper on the subject, says "We found a central part of Valles Marineris to be packed full of water-far more water than we expected. This is very much like Earth's permafrost regions, where water ice permanently persists under dry soil because of the constant low temperatures"
• Researchers added that if all of the hydrogen they have detected is present in the form of water ice, the compound could make up as much as 40% of near-surface material in the area.

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Elusive cosmic objects with masses comparable to those of planets in our solar system, rogue planets do not orbit a star, but instead roam freely on their own. While not many of these rogue planets were known until recently, a group of astronomers have just discovered at least 70 new rogue planets in our galaxy- the largest group of rogue planets ever discovered.

As rogue planets are far away from any star that can illuminate them, it is nearly impossible to image them. The team of researchers involved in this discovery, which was published in December 2021 in Nature Astronomy, utilised the fact that these planets are hot enough to glow in the few million years after their formation. Using sensitive cameras on super large telescopes, these can thus be detected.

Decades of data

Using two decades of data from a number of telescopes, both ground based and those in space, the team were able to measure the tiny motions, the colours and luminosities of millions of sources in a large area. These measurements then allowed them to identify the faintest objects in the region, thus spotting the rogue planets.

The study, which marks a grand success for the collaboration of ground-based and space-based telescopes, also suggests that there could be more of these nomadic planets that have proved to be elusive so far.

Mystery remains

By studying these starless planets, scientists might be able to figure out how these mysterious rogue planets form. While some believe these planets could have been kicked out from their parent system, and others think they are formed from the collapse of a gas cloud that doesn't lead to the formation of a star, the actual mechanism by which they are formed remains unknown.

Even though our current technology has enabled scientists to find at least 70 new rogue planets with mass comparable to Jupiter, it is found wanting to study them further. Greater advances in technology would certainly be key to unlock the entire mystery of rogue planets.

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At the core of the sun, gravitational attraction produces immense pressure and temperature, which can reach more than 27 million degrees Fahrenheit (15 million degrees Celsius). Hydrogen atoms get compressed and fuse together, creating helium. This process is called nuclear fusion.

Nuclear fusion produces huge amounts of energy. The energy radiates outward to the sun's surface, atmosphere and beyond. From the core, energy moves to the radiative zone, where it bounces around for up to 1 million years before moving up to the convective zone, the upper layer of the sun's interior. The temperature here drops below 3.5 million degrees F (2 million degrees C). Large bubbles of hot plasma form a soup of ionized atoms and move upward to the photosphere.

The temperature in the photosphere is about 10,000 degrees F (5,500 degrees C). It is here that the sun's radiation is detected as visible light. Sunspots on the photosphere are cooler and darker than the surrounding area. At the center of big sunspots the temperature can be as low as 7,300 degrees F (4,000 degrees C).

The chromosphere, the next layer of the sun's atmosphere is a bit cooler — about 7,800 degrees F (4,320 degrees C). According to the National Solar Observatory (NSO), chromosphere literally means "sphere of color." Visible light from the chromosphere is usually too weak to be seen against the brighter photosphere, but during total solar eclipses, when the moon covers the photosphere, the chromosphere can be seen as a red rim around the sun.

Credit : Space.com

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For the first time in history, a spacecraft has touched the Sun. NASA’s Parker Solar Probe has now flown through the Sun’s upper atmosphere – the corona – and sampled particles and magnetic fields there.

The new milestone marks one major step for Parker Solar Probe and one giant leap for solar science. Just as landing on the Moon allowed scientists to understand how it was formed, touching the very stuff the Sun is made of will help scientists uncover critical information about our closest star and its influence on the solar system.

On April 28, 2021, during its eighth flyby of the Sun, Parker Solar Probe encountered the specific magnetic and particle conditions at 18.8 solar radii (8.127 million miles) above the solar surface that told scientists it had crossed the Alfvén critical surface for the first time and finally entered the solar atmosphere.

As it circles closer to the solar surface, Parker is making new discoveries that other spacecraft were too far away to see, including from within the solar wind – the flow of particles from the Sun that can influence us at Earth. In 2019, Parker discovered that magnetic zig-zag structures in the solar wind, called switchbacks, are plentiful close to the Sun. But how and where they form remained a mystery.

Credit : Sci-Tech Daily 

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The Sun doesn’t have a solid surface like Earth and the other rocky planets and moons. The part of the Sun commonly called its surface is the photosphere. The word photosphere means "light sphere" – which is apt because this is the layer that emits the most visible light. It’s what we see from Earth with our eyes. (Hopefully, it goes without saying – but never look directly at the Sun without protecting your eyes.)

Although we call it the surface, the photosphere is actually the first layer of the solar atmosphere. It's about 250 miles thick, with temperatures reaching about 10,000 degrees Fahrenheit (5,500 degrees Celsius). That's much cooler than the blazing core, but it's still hot enough to make carbon – like diamonds and graphite – not just melt, but boil. Most of the Sun's radiation escapes outward from the photosphere into space.

The Sun doesn’t have a solid surface like Earth and the other rocky planets and moons. The part of the Sun commonly called its surface is the photosphere. The word photosphere means "light sphere" – which is apt because this is the layer that emits the most visible light. It’s what we see from Earth with our eyes. (Hopefully, it goes without saying – but never look directly at the Sun without protecting your eyes.)

Although we call it the surface, the photosphere is actually the first layer of the solar atmosphere. It's about 250 miles thick, with temperatures reaching about 10,000 degrees Fahrenheit (5,500 degrees Celsius). That's much cooler than the blazing core, but it's still hot enough to make carbon – like diamonds and graphite – not just melt, but boil. Most of the Sun's radiation escapes outward from the photosphere into space.

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