My Science School

À nebula (plural nebulae) is a giant cloud of dust and gas in space. Most nebulae are formed from the gas and dust thrown out by the explosion of a dying star, while some are formed from the gas that is already in the interstellar medium (the matter and radiation that exist in the space between the star systems in a galaxy).

Where are the nebulae?

Nebulae exist in interstellar space. Astronomers use very powerful telescopes to take pictures of faraway nebulae. Many of NASA's space telescopes such as the Spitzer Space Telescope and Hubble Space Telescope have captured many images of faraway nebulae. The closest known nebula to Earth is called the Helix Nebula, the remnant of a dying star, possibly one like the Sun. The Helix Nebula is approximately 700 light years from Earth. This means it will take 700 years to reach this nebula if one travels at the speed of light.

Star nurseries

Some nebulae are regions where new stars are beginning to form. This is why they are called 'star nurseries'. A nebula is made of dust and gases, mostly hydrogen and helium. These dust and gases are very spread out. However, gravity can slowly pull together clumps of these dust and gas. As each clump gets bigger in size, its gravity gets stronger. Eventually, the clump gets so big that it collapses from its own gravity. This collapse causes the material at the centre of the cloud to heat up. It is this hot core that is the beginning of a star.

 

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Sometimes, you may have watched the moon near the horizon and wondered "Why is the moon unusually bigger tonight?" Does the moon grow bigger near the horizon and shrink when it moves high up in the sky? This perception is called Moon illusion: Your brain is playing a trick on you.

Sky watchers have observed this phenomenon for thousands of years. The precise reason for the moon appearing to be expanding and contracting continues to puzzle scientists even today. But in general, our brain is tuned to think that objects near the horizon are (usually) more distant and larger than those overhead. But one thing is for sure - the moon isn't changing size.

Here is an activity to test this: Take a sheet of paper and roll it up into a narrow tube. Point it at the rising moon, look through it and adjust the tube's size until it's slightly larger than the moon. Fix the tube using a tape so its size stays the same and look at the moon again a few hours later when it's higher in the sky. You'll see it fills the same space.

 

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A galaxy is a huge collection of stars, their solar systems, dust and gas. It is held together by gravity.

Earth is a part of the solar system, which is a small part of the Milky Way Galaxy. All those stars you see in the sky at night belong to the Milky Way.

When you are far away from city lights, some place really dark, you can even see the dusty bands of the Milky Way stretch across the sky.

How many are there?

There are countless galaxies out there. Once, when the Hubble-Space Telescope looked at a small patch of space for 12 days. It found nearly 10,000 galaxies of all sizes, shapes and colours.

Some scientists believe there could be as many as one billion galaxies in this universe!

How do they look?

Galaxies came in different shapes. But the two most common types, based on ones discovered so far, are Spiral Galaxy and Elliptical Galaxy.

The Milky Way is a spiral-shaped galaxy. This type of galaxy has curved arms that make it look like a pinwheel.

Elliptical galaxies, on the other hand, are smooth, and oval shaped.

Just like ours, other galaxies too get their light from stars that inhabit them.

On collision course

There are times when two or more galaxies can get too close and smash into each other. For example, the Milky Way galaxy will someday bump into the Andromeda galaxy, its closest neighbour.

However, this won’t happen for another five billion years at least, and even if it were to happen anytime soon, you wouldn’t notice and spread out at the ends that even if they do bump into each other, the planets and solar systems often don’t get close to colliding.

 

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Scientists send spacecraft to probe objects in space. These spacecraft carry instruments that help them take pictures and collect data in space and send them back to Earth. But to do this, the spacecraft needs electricity So what powers it?

Based on the mission it is assigned, and factors such as where the spacecraft is travelling, what it plans to do there and how long it needs to work engineers choose the best way to power a spacecraft.

The Sun

One source of power engineers consider is energy from the Sun, or solar power. Spacecraft that orbit close to Earth are dose enough to the Sun to use solar power. These spacecraft are fitted with solar panels, which convert the Sun's energy into electricity. The electricity from the panels charges a battery in the spacecraft and can be used even when the spacecraft doesn't have direct sunlight

Batteries

Sometimes, when the mission is only for a short duration, such as the Huygens probe that landed on Titan, Saturn's largest moon, and meant to work only for a few hours, engineers may power the spacecraft with batteries. These batteries are designed to be tough since they need to withstand the harsh environment of space.

Atoms

An atom is a tiny building block of matter. Atoms need to store a lot of energy to hold themselves together. However, atoms such as radioisotopes are unstable and begin to fall apart. As they fall apart, they release energy as heat. A radioisotope power system uses the temperature difference between the heat from the unstable atoms and the cold of space to produce electricity. This system produces power for a very long time even in harsh environments. That's why this system has been used to power many of NASA's missions, including the two Voyager spacecraft that continue to send back information after over four decades in space.

 

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Chinese space probe Chang'e- 5, carrying rocks and soil from the Moon, returned to Earth safely on December 17. The capsule carrying the samples landed in northern China's Inner Mongolia region. This is the first lunar sample return since 1976, when the former Soviet Union's Luna 24 returned with lunar material. What's the current mission all about? What happened to the Moon rocks that were recovered by the U.S. and Russia?

What is Chang'e-5 mission about?

Chang'e-5 is a robotic mission of the Chinese Lunar Exploration Program, launched on November 23, 2020. The Chang'e 5 probe included a lander, an ascender, orbiter and a returner. After it entered the designated circular lunar orbit, the lander-ascender pair separated from the orbiter-returner group and descended and successfully touched down near Mons Rumker, a volcanic mountain in the Moon's huge Oceanus Procellarum ("Ocean of Storms") region on December 1, 2020. The mission spent only two days on the Moon's surface, gathering samples by digging and scooping. The 2kg samples were loaded onto an ascent vehicle that subsequently docked with an Earth return module. The service module of the mission's orbiter then released the return capsule, which eventually landed on Earth with the samples on December 17.

What is the significance of the landing site?

• The landing site is a volcanic plain called Mons Rumker in the Oceanus Procellarum region on the Moon's near side. The places explored by Apollo and Luna were all more than 3 billion years old, whereas Mons Rumker is estimated to be around 1.2 billion years old.


• A young surface is smooth and almost unblemished, while an old surface is heavily cratered With Moon rocks collected by Neil Armstrong and other astronauts, scientists could measure radioactive elements in the rocks and precisely calculate when a volcanic eruption had occurred, and thus the age of the parts of the Moon where the Apollo explorers set foot But none of the previous missions landed on a younger part of the Moon, leaving a large gap of uncertainty.


• Scientists also want to understand the differences in composition of the varying parts of the Moon, and the samples might explain how part of the Moon was still molten some 3 billion years after it formed.

How will the samples help scientists understand the Moon?

The new specimens could provide fresh insights into the geology and early history of Earth's natural satellite. Scientists hope the samples will help them learn about the Moon's origins, formation and volcanic activity on its surface. China will make some of the samples available to scientists in other countries.

Where are the Moon rocks previously collected by the U.S. and Russia now?

In the 1970s, three successful Soviet Luna missions brought back a total of 301 grams of Moon samples. NASA's Apollo astronauts lugged back 842 pounds of Moon rock and soil Scientists are still studying the Apollo and Luna samples.

• The Moon samples collected by Apollo astronauts are stored at the Lunar Sample Laboratory Facility at NASA's Johnson Space Center in Houston, Texas, in nitrogen filled steel cabinets. Some of those collected by Luna missions had been auctioned.


• In 2000, the U.S. decided to give away Moon rocks to 32 Apollo astronauts, on the condition that they should not be sold.


• Moon rocks collected by Apollo 11 and Apollo 17 astronauts were given away to 135 countries around the world and the 50 U.S. states as a token of goodwill.

What are China's other moon missions?

In this century so far, only China has successfully put robotic spacecraft on the surface of the Moon: Chang’e-3 in December 2013, and Chang’e-4 in January 2019 became the first spacecraft to land on the far side of the Moon Chang’e-4 is still roving and studying lunar geology. Chang’e-1 and Chang’e-2 were lunar orbiters, launched in 2007 art 2010 respectively. All the missions have been named after the Chinese Moon goddess, Chang’e.

What are China's upcoming Moon missions?

China plans to launch a spacecraft called Change 6 to return samples from the Moon's South pole. The more advanced Chang'e 7 and Chang'e-8 spacecraft are also slated to land near tire south pole to carry out analysis of the region and test new technologies, including detecting and extracting materials such as water and hydrogen that could be useful to future human explorers, and testing 3D printing on the lunar surface China hopes to launch an international Lunar research station and ultimately a human colony on the Moon by the 2030.

 

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When one object crosses in front of another in space, it is known as transit. For example, when the Moon passes between the Earth and the Sun, the Moon is ‘transiting‘ the Sun.

Why is it important?

Just like objects in our solar system that transit the Sun, there are objects outside our solar system too that transit stars there. These objects include planets known as explants, and their transit help scientists identify these planets.

If the orbit of a planet is lined up right, the planet is lined up right, the planet will transit the star it orbits. When this happens, the light from the star dims by a small amount of time between each transit. This is how scientists discovered seven exoplanets around a star called TRAPPIST-1. There of these planets were discovered in 2015, while four more were identified in 2017.

Bottomline, transits not only help scientists identify new planets but also understand the world beyond our solar system.

The transits we can see

From Earth, there are two main transits that can be seen by people. One is the transit of the Moon, as it passes the Sun. this is when we witness a solar eclipse. The other is the transit of the planet Venus when it passes between the Earth and the Sun during its orbit.

While solar eclipse can be observed often, the transit of Venus cannot be seen frequently because of how he orbits of Venus and Earth are lined up. The last transit of Venus was on June 6, 2012. The next one, however is not until 2117!

 

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