My Science School

 The Venera program was the name given to a series of space probes developed by the Soviet Union between 1961 and 1984 to gather information about the planet Venus. Ten probes successfully landed on the surface of the planet, including the two Vega program and Venera-Halley probes, while thirteen probes successfully entered the Venusian atmosphere. Due to the extreme surface conditions on Venus, the probes could only survive for a short period on the surface, with times ranging from 23 minutes to two hours.

The first Soviet attempt at a flyby probe to Venus was launched on 4 February 1961, but failed to leave Earth orbit. In keeping with the Soviet policy at that time of not announcing details of failed missions, the launch was announced under the name Tyazhely Sputnik ("Heavy Satellite"). It is also known as Venera 1VA.

As with some of the Soviet Union's other planetary probes, the later versions were launched in pairs with a second vehicle launched soon after the first.

The VeGa probes to Venus and comet 1/P Halley launched in 1984 also used this basic Venera design, including landers but also atmospheric balloons which relayed data for about two days. "VeGa" is an agglutination of the words "Venera" (Venus in Russian) and "Gallei" (Halley in Russian).

 

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Venus is sometimes called Earth's twin because Venus and Earth are almost the same size, have about the same mass (they weigh about the same), and have a very similar composition (are made of the same material). They are also neighboring planets. However, Venus and Earth are also very different. Venus has an atmosphere that is about 100 times thicker than Earth's and has surface temperatures that are extremely hot. Venus does not have life or water oceans like Earth does. Venus also rotates backwards compared to Earth and the other planets.

Venus is shrouded with a thick, dense atmosphere, far thicker than our own. On Earth, our atmosphere is thick enough to produce a significant amount of pressure on the surface, but our planet is not totally cloud-covered. Our Earth-monitoring satellites are regularly able to see the ground from space, without the interference of the clouds. There’s no such break in the clouds on Venus. Venus is permanently clouded over, and its atmosphere is so thick that the surface pressure on Venus is 92 times the pressure here on Earth. An unshielded human would fare very badly in this environment.

There is another similarity between the Earth and Venus, though not one that makes Venus a more hospitable place to go visit: both planets have volcanoes. Because Venus is so hot and the pressures are so great, the volcanoes on Venus’ surface aren’t quite as vertically imposing as they can be on Earth.

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Venus is hotter than Mercury because it has a much thicker atmosphere. The atmosphere, the gaseous layer surrounding a planet, is like a blanket. Think of two people sitting next to a campfire one is much closer to the fire while another is further away. The one that is closer doesn't have a blanket (Mercury), while the other further away has a sleeping bag (Venus). Both persons are getting heat from the fire but the person with the sleeping bag keeps all the heat he or she gets. Mercury is closer but because it has a very thin or no atmosphere at all the heat goes out into space. Venus on the other hand with it's much thicker atmosphere holds all the heat it gets. The heat the atmosphere traps is called the greenhouse effect. If Venus did not have an atmosphere the surface would be -128 degrees Fahrenheit much colder than 333 degrees Fahrenheit, the average temperature of Mercury.

Consider our own planet. When you stand at sea level on Earth, you’re experiencing one atmosphere of pressure. But if you could stand on the surface of Venus – and trust me, you don’t want to – you’d experience ninety-two times as much atmospheric pressure. This is the same kind of pressure as being a kilometer underneath the surface of the ocean.

Venus also shows us what happens when carbon dioxide levels just keep on rising. Radiation from the Sun is absorbed by the planet, and the infrared heat emitted is trapped by the carbon dioxide, which creates a runaway greenhouse effect.

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In late 2020, scientists studying the atmosphere of Venus announced the surprising – and controversial – discovery of phosphine, a chemical that, on Earth, is produced primarily by living organisms. Then – in March 2021 – a study from Rakesh Mogul of Cal Poly Pomona supported the original finding of phosphine and went further. It suggested that other “biologically relevant chemicals” in Venus’ atmosphere appear to be in a state of disequilibrium: another hallmark of life.

Venus, a world with a reputation for being hot and hellish, just became one of the most intriguing—and closest—spots in the universe for investigating the question of whether life exists beyond Earth. A NASA rover is currently on its way to Mars to look for signs of life, but the robot is designed to find long-dead microbes, preserved in the rusty soil for billions of years. The phosphine discovery presents the tantalizing possibility that life might be on Venus right now. If this discovery is confirmed, which will likely require sending a spacecraft, we would know for the first time in human history that the solar system has two planets where life exists. In a cosmic sense, we wouldn’t be alone anymore.

Venus is a notoriously inhospitable planet, where surface temperatures hover around 860 degrees Fahrenheit (460 Celsius). Travel high into the atmosphere, where it’s cooler, and you’ll find more bearable, even comfortable, temperatures, closer to what we experience on Earth. This is where the telescopes detected the signature of phosphine. But Venus’s atmosphere is so acidic, with clouds made of droplets of sulfuric acid, that any phosphine would be quickly zapped. For the gas to stick around, something must replenish the supply.

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Galaxy morphological classification is a system used by astronomers to divide galaxies into groups based on their visual appearance. There are several schemes in use by which galaxies can be classified according to their morphologies, the most famous being the Hubble sequence, devised by Edwin Hubble and later expanded by Gérard de Vaucouleurs and Allan Sandage. However, galaxy classification and morphology are now largely done using computational methods and physical morphology.

The Hubble sequence is a morphological classification scheme for galaxies invented by Edwin Hubble in 1926. It is often known colloquially as the “Hubble tuning-fork” because of the shape in which it is traditionally represented. Hubble's scheme divides galaxies into three broad classes based on their visual appearance.

The de Vaucouleurs system for classifying galaxies is a widely used extension to the Hubble sequence, first described by Gérard de Vaucouleurs in 1959. De Vaucouleurs argued that Hubble's two-dimensional classification of spiral galaxies—based on the tightness of the spiral arms and the presence or absence of a bar—did not adequately describe the full range of observed galaxy morphologies. In particular, he argued that rings and lenses are important structural components of spiral galaxies.

 

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A galaxy is a large group of stars, gas, and dust bound together by gravity. They come in a variety of shapes and sizes. The Milky Way is a large barred spiral galaxy.

It is very difficult to count the number of stars in the Milky Way from our position inside the galaxy. Our best estimates tell us that the Milky Way is made up of approximately 100 billion stars. These stars form a large disk whose diameter is about 100,000 light years. Our Solar System is about 25,000 light years away from the center of our galaxy – we live in the suburbs of our galaxy. Just as the Earth goes around the Sun, the Sun goes around the center of the Milky Way. It takes 250 million years for our Sun and the solar system to go all the way around the center of the Milky Way.

There are billions of other galaxies in the Universe. Only three galaxies outside our own Milky Way Galaxy can be seen without a telescope, and appear as fuzzy patches in the sky with the naked eye. The closest galaxies that we can see without a telescope are the Large and Small Magellanic Clouds. These satellite galaxies of the Milky Way can be seen from the southern hemisphere. Even they are about 160,000 light years from us. The Andromeda Galaxy is a larger galaxy that can be seen from the northern hemisphere (with good eyesight and a very dark sky). It is about 2.5 million light years away from us, but its getting closer, and researchers predict that in about 4 billion years it will collide with the Milky Way. , i.e., it takes light 2.5 million years to reach us from one of our "nearby" galaxies. The other galaxies are even further away from us and can only be seen through telescopes.

 

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Astronomers classify galaxies into three major categories: elliptical, spiral and irregular. These galaxies span a wide range of sizes, from dwarf galaxies containing as few as 100 million stars to giant galaxies with more than a trillion stars.

Ellipticals, which account for about one-third of all galaxies, vary from nearly circular to very elongated. They possess comparatively little gas and dust, contain older stars and are not actively forming stars anymore. The largest and rarest of these, called giant ellipticals, are about 300,000 light-years across. Astronomers theorize that these are formed by the mergers of smaller galaxies. Much more common are dwarf ellipticals, which are only a few thousand light-years wide.

Spiral galaxies appear as flat, blue-white disks of stars, gas and dust with yellowish bulges in their centers. These galaxies are divided into two groups: normal spirals and barred spirals. In barred spirals, the bar of stars runs through the central bulge. The arms of barred spirals usually start at the end of the bar instead of from the bulge. Spirals are actively forming stars and comprise a large fraction of all the galaxies in the local universe.

Irregular galaxies, which have very little dust, are neither disk-like nor elliptical. Astronomers often see irregular galaxies as they peer deeply into the universe, which is equivalent to looking back in time. These galaxies are abundant in the early universe, before spirals and ellipticals developed.

 Astronomers believe that after the big bang, the explosion which began the universe 10 billion to 20 billion years ago, gravity began to compress masses of free-floating gas. Two main theories, bottom-up and top-down, explain what happened next. According to bottom-up theories, clusters began to form and assembled together into the larger units we know as galaxies. Top-down theories suggest that galaxies formed first, and the stars and other objects within them were subsequently produced.

 

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Since prehistoric times, human beings have looked up at at the night sky and pondered the mystery of the band of light that stretches across the heavens. And while theories have been advanced since the days of Ancient Greece as to what it could be, it was only with the birth of modern astronomy that scholars have come to know precisely what it is – i.e. countless stars at considerable distances from Earth.

The term “Milky Way”, a term which emerged in Classical Antiquity to describe the band of light in the night sky, has since gone on to become the name for our galaxy. Like many others in the known Universe, the Milky Way is a barred, spiral galaxy that is part of the Local Group – a collection of 54 galaxies. Measuring 100,000 – 180,000 light-years in diameter, the Milky Way consists of between 100 and 400 billion stars.

If you could see our galaxy from the side, it would look like a huge, thin disk with a slight bump in the center. This flat shape is caused by the galaxy spinning around. Everything in our spinning galaxy would fly off into space if it weren’t for the force of gravity.

Without a telescope , we can see about 6,000 stars from Earth. That may seem like a lot of stars, but it’s actually only a small part of the whole. If you think of the entire galaxy as a giant pizza, all the stars you can see from Earth fall within about one pepperoni on that pizza. In fact, for every star you can see, there are more than 20 million you cannot see. Most of the stars are too faint, too far away or blocked by clouds of cosmic dust.

 

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Earth is the fourth smallest of the planets—though in terms of the rocky planets, it's the largest—but it's the most dense. Jupiter is the largest planet in the solar system, but it's Saturn—the solar system's second largest planet—that takes the prize for least dense. It's less dense than water, which has led many people to postulate that it would float. However, even if it somehow found its way to a body of water large and deep enough to contain it, Saturn would break apart and its rocky core would sink.

A planet's density tells astronomers important things about its inner structure. For example, Mercury is almost as dense as Earth, even though it's much smaller. Since a small planet experiences less gravitational compression than a larger planet—that is, the effects of gravity don't squish it down as much—astronomers need to look for another reason for its density. That's why they believe that it has a large, iron-rich core. Uranus, on the other hand, is the second-least dense of the gas giants, right behind Saturn. Like Saturn, it has a gaseous outer layer and rocky core, but where it differs is in an icy mantle between those layers made up of water, ammonia, and methane.

 

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The European Space Agency in 1975 and headquartered in Paris, ESA has a worldwide staff of about 2,200 in 2018 and an annual budget of about €6.68 billion in 2020.

ESA's space flight programme includes human spaceflight (mainly through participation in the International Space Station program); the launch and operation of unmanned exploration missions to other planets and the Moon; Earth observation, science and telecommunication; designing launch vehicles; and maintaining a major spaceport, the Guiana Space Centre at Kourou, French Guiana. The main European launch vehicle Ariane 5 is operated through Arianespace with ESA sharing in the costs of launching and further developing this launch vehicle. The agency is also working with NASA to manufacture the Orion Spacecraft service module that will fly on the Space Launch System.

 

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NASA's next big space observatory came one step closer to completion last week, as engineers placed the final segment of the James Webb Space Telescope’s primary mirror.

The careful construction of the segmented mirror began in November 2015 at the Goddard Space Flight Center in Greenbelt, Maryland. Each hexagonal segment is 4.2 feet (1.3 meters) across, coated with gold and beryllium, and weighs 88 pounds. There are 18 mirror segments in all. Now fully assembled, the primary mirror is 21.3 feet (6.5 meters) in diameter, making JWST the largest telescope ever fielded in space.

Often touted as the Hubble Space Telescope’s successor, the James Webb Space Telescope (JWST) will actually work at longer wavelengths than its famous cousin: from the long-wavelength end of the visual spectrum into the infrared regime. In that sense, it’s more of a follow-on to the Spitzer Space Telescope. JWST’s primary is also much larger than Hubble’s, which spanned only 2.4 meters, yet JWST’s overall observatory is actually lighter in mass.

 

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The Starship system is a fully reusable, two?stage?to?orbit super heavy?lift launch vehicle under development by SpaceX. The system is composed of a booster stage named Super Heavy and a second stage, also called "Starship". Unusual for a traditional launch vehicle second stage, the Starship second stage is being designed to be a long?duration cargo and passenger?carrying spacecraft.

The Starship prototype descended under active aerodynamic control, accomplished by independent movement of two forward and two aft flaps on the vehicle. All four flaps were actuated by an onboard flight computer to control Starship’s attitude during flight and enabled precise landing at the intended location. SN15’s Raptor engines reignited as the vehicle performed the landing flip maneuver immediately before touching down for a nominal landing on the pad.

These test flights of Starship are all about improving our understanding and development of a fully reusable transportation system designed to carry both crew and cargo on long-duration interplanetary flights, and help humanity return to the Moon, and travel to Mars and beyond.

 

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Valles Marineris, or Mariner Valley, is a vast canyon system that runs along the Martian equator just east of the Tharsis region. Valles Marineris is 4000 km (2500 mi) long and reaches depths of up to 7 km (4 mi)! For comparison, the Grand Canyon in Arizona is about 800 km (500 mi) long and 1.6 km (1 mi) deep. In fact, the extent of Valles Marineris is as long as the United States and it spans about 20 percent (1/5) of the entire distance around Mars! The canyon extends from the Noctis Labyrinthus region in the west to the chaotic terrain in the east. Most researchers agree that Valles Marineris is a large tectonic "crack" in the Martian crust, forming as the planet cooled, affected by the rising crust in the Tharsis region to the west, and subsequently widened by erosional forces. However, near the eastern flanks of the rift there appear to be some channels that may have been formed by water.

The canyon system contains a number of different features that give clues to its formation. Collapse pits created by rushing water eating away at the land, massive floods, and seeping along canyon walls all point to water just at or beneath the surface at some point in the Martian history. Cracks in the crust, cliffs and walls, and landslides also exist along the expanse of Valles Marineris.

The vast canyon can be seen from Earth through a telescope as a dark scarring on the planet's surface. Features known as chasmata, steep depressions that resemble canyons on Earth, dominate the canyon.

The canyon begins in the Noctis Labyrinthus on the western edge, a region of material thought to have volcanic origins. Two parallel chasmata, Ius and Tithonium, stretch eastward, and contain lava flows and faults from the Tharsis Bulge.

 

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