My Science School

The Eta Aquarids are pieces of debris from Halley's Comet, which is a well-known comet that is viewable from Earth approximately every 76 years. Also known as 1P/Halley, this comet was last viewable from Earth in 1986 and won't be visible again until the middle of 2061. The annual Eta Aquarid meteor shower gets its name because the radiant -- or direction of origin -- of the meteors appears to come from the constellation Aquarius.

The comet is named after English astronomer Edmond Halley, who examined reports of a comet approaching Earth in 1531, 1607 and 1682. He concluded that these three comets were actually the same comet returning over and over again, and predicted the comet would come again in 1758.

Halley didn't live to see the comet's return, but his discovery led to the comet being named after him. (The traditional pronunciation of the name usually rhymes with valley.) Halley's calculations showed that at least some comets orbit the sun.

Further, the first Halley's Comet of the space age — in 1986 — saw several spacecraft approach its vicinity to sample its composition. High-powered telescopes also observed the comet as it swung by Earth.

While the comet cannot be studied up close for many decades, scientists continue to perform comet science in the solar system, looking at other small bodies that can be compared to Halley. A notable example was the Rosetta probe, which looked at Comet 67P/Churyumov–Gerasimenko between 2014 and 2016 and concluded that the comet has a different kind of water than Earth's water.

Credit : Space.com

Picture Credit : Google

Ultraviolet light ionizes the neutral gas blown off the comet, and the solar wind carries these ions straight out from the Sun to form the ion tail, which typically glows blue. The dust tail on the other hand is neutral, composed of small dust particles (similar in size to those found in cigarette smoke). Pressure from the Sun's radiation pushes these particles away from the comet’s nucleus. These particles continue to follow the comet’s orbit around the Sun, and form a diffuse, curved tail that typically appears white or pink from Earth.

The plasma tail comprises electrons and ions that are ionized by the sun's ultraviolet radiation. The dust tail consists of micrometer-scale particles. The dust tail is wide and slightly bent because of the pressure of the light from the sun and the orbital action of the comet's nucleus.

Picture Credit : Google

Comets are believed to have two sources. Long-period comets (those which take more than 200 years to complete an orbit around the Sun) originate from the Oort Cloud. Short-period comets (those which take less than 200 years to complete an orbit around the Sun) originate from the Kuiper Belt.

The short-period comets are thought to originate in the Kuiper Belt, an area outside Neptune's orbit (from about 30 to 50 AU) that has many icy comet-like objects. The long-period comets tend to have orbits that are randomly oriented, and not necessarily anywhere near the ecliptic. They are thought to originate in the Oort cloud. The Oort cloud has never been observed, but is believed to have at least 1012 icy objects located between 3000 AU and 100,000 AU in a spherical distribution around the Sun.

As comets travel close to the Sun, the Sun's heat begins to vaporize the ices and causes them to form a fuzzy, luminous area of vaporized gas around the nucleus of the comet known as a coma. Outside the coma is a layer of hydrogen gas called a hydrogen halo which extends up to 1010 meters in diameter.

Credit : Las Cumbres 

Picture Credit : Google

Comets go around the Sun in a highly elliptical orbit. They can spend hundreds and thousands of years out in the depths of the solar system before they return to Sun at their perihelion. Like all orbiting bodies, comets follow Kepler's Laws - the closer they are to the Sun, the faster they move.
While a comet  is at a great distance from the Sun, its exists as a dirty snowball several kilmoeters across. But as it comes closer to the Sun, the warming of its surface causes its materials to melt and vapourise producing the comet's characteristic tail. Comet tails can be as long as the distance between the Earth and the Sun.

According to Kepler's first law, all objects orbit the sun in elliptical paths. The orbits of the planets, except for Pluto, are almost circular, and so are those of asteroids and icy objects in the Kuiper belt, which is just beyond the orbit of Neptune. Comets that originate in the Kuiper belt are known as short period comets and tend to remain in the same narrow band as the planets.

Long period comets, which originate in the Oort cloud, which is beyond the Kuiper belt and on the outskirts of the solar system, are a different matter. Their orbits can be so elliptical that the comets can completely disappear for hundreds of years. Comets from beyond the Oort cloud can even have parabolic orbits, meaning they make a single appearance in the solar system and never come back again.

None of this behavior is mysterious once you understand how planets and comets came to be there in the first place. It all has to do with the birth of the sun.

Credit : Sciencing 

Picture Credit : Google

Comets are frozen leftovers from the formation of the solar system composed of dust, rock, and ices. They range from a few miles to tens of miles wide, but as they orbit closer to the Sun, they heat up and spew gases and dust into a glowing head that can be larger than a planet. This material forms a tail that stretches millions of miles.

As theorized by astronomer Gerard Kuiper in 1951, a disc-like belt of icy bodies exists beyond Neptune, where a population of dark comets orbits the Sun in the realm of Pluto. These icy objects, occasionally pushed by gravity into orbits bringing them closer to the Sun, become the so-called short-period comets. Taking less than 200 years to orbit the Sun, in many cases their appearance is predictable because they have passed by before. Less predictable are long-period comets, many of which arrive from a region called the Oort Cloud about 100,000 astronomical units (that is, about 100,000 times the distance between Earth and the Sun) from the Sun. These Oort Cloud comets can take as long as 30 million years to complete one trip around the Sun.

Each comet has a tiny frozen part, called a nucleus, often no larger than a few kilometers across. The nucleus contains icy chunks, frozen gases with bits of embedded dust. A comet warms up as it nears the Sun and develops an atmosphere, or coma. The Sun's heat causes the comet's ices to change to gases so the coma gets larger. The coma may extend hundreds of thousands of kilometers. The pressure of sunlight and high-speed solar particles (solar wind) can blow the coma dust and gas away from the Sun, sometimes forming a long, bright tail. Comets actually have two tails?a dust tail and an ion (gas) tail.

Most comets travel a safe distance from the Sun?comet Halley comes no closer than 89 million kilometers (55 million miles). However, some comets, called sungrazers, crash straight into the Sun or get so close that they break up and evaporate.

Credit : NASA Science 

Picture Credit : Google

Many parts of the cardiovascular system (including the heart) are influenced by gravity. On Earth, for example, the veins in our legs work against gravity to get blood back to the heart. Without gravity, however, the heart and blood vessels change – and the longer the flight, the more severe the changes.

The size and shape of the heart, for example, changes with microgravity and the right and left ventricles decrease in mass. This may be because of a decrease in fluid volume (blood) and changes in myocardial mass. A human heart rate (number of beats per minute) is lower in space than on Earth, too. In fact, it has been found that the heart rate of individuals standing upright on the ISS is similar to their rate while lying down pre-flight on Earth. Blood pressure is also lower in space than on Earth.

The cardiac output of the heart – the amount of blood pumped out of the heart each minute – decreases in space, too. Without gravity, there is also a redistribution of the blood – more blood stays in the legs and less blood is returned to the heart, which leads to less blood being pumped out of the heart. Muscle atrophy also contributes to reduced blood flow to the lower limbs.

This reduced blood flow to the muscles, combined with the loss of muscle mass, impacts aerobic capacity. 

Credit : The Conversation 

Picture Credit : Google

Before we can understand weight, we must first understand gravity and mass. Gravity is a natural force that attracts objects to each other.

On Earth, gravity is the constant force pulling us toward Earth and preventing us from flying off into space like a balloon. When you step on a scale, it shows your weight as a number. This number is actually a measurement of the gravitational pull Earth has on you.

Mass is how much “stuff" you are made of. Unlike weight, your mass is the same whether you are on Earth, on Mars, on the moon, sitting in your living room, swimming in the ocean, or floating somewhere in outer space.

Someone who weighs 200 pounds has more mass than someone who weighs 100 pounds. The more mass a person has, the greater the pull of gravity on them. This is why a scale shows a higher number for a larger person.

Small celestial bodies have weaker gravitational pulls than Earth. Larger planets, such as Jupiter and Saturn, have stronger gravitational pulls, which means you'd weigh more if you visited those planets.

Since the Moon is smaller than Earth, it has a weaker gravitational pull. In fact, the Moon only has 1/6 the gravity that Earth does. This means you weigh six times less on the Moon than you do on Earth!

When the astronauts landed on the Moon in 1969, they wore space suits and carried heavy packs of equipment. Since gravity is much weaker on the Moon, everything weighed only 1/6 of its Earth-weight, and the astronauts were able to move around the Moon very easily.

Credit : Wonderopolis 

Picture Credit : Google

One of the major obstacles to long-term space missions in the threat of severe bone loss in astronauts. In the microgravity environment of space, astronauts lose on average 1% to 2% of their bone mineral density every month. For a short-duration flight, bone loss is a fairly minor consequence.

On a long-duration space flight, such as those planned for missions to Mars and beyond, bone loss can be a serious impediment. This loss may not hinder astronauts while they are in orbit, but upon return to Earth, their weakened bones will be fragile and at an increased risk of fractures. At this time, it is unknown whether this bone loss will eventually reach a plateau, or whether it will continue indefinitely.

Bones are not unchanging calcium structures; they constantly reshape themselves in relation to the stress that is put on them. Just like muscles, if you don't use your bones, they will weaken. Bone loss occurs in the weightless environment of space because bones no longer have to support the body against gravity. On Earth, gravity applies a constant mechanical load to the skeletal system, that causes healthy bones to maintain a certain density so that they are able to support the body.

The best way to build bone mass is by doing weight-bearing exercises such as walking, jogging, volleyball, and basketball. However, it is very difficult to duplicate weight-bearing exercise in a weightless environment. Astronauts must use restraints to strap themselves to a treadmill in order to create the necessary weight-bearing environment. Although this countermeasure slows the rate of bone loss, it does not eliminate the problem altogether.

Astronauts are not the only ones who must worry about bone loss. One and a half million Canadians suffer from osteoporosis, a disease that causes bones to lose density and strength. One in four women and one in eight men over the age of 50 have osteoporosis. Researchers hope that solving the problem of bone loss in space will also help to prevent and cure the disease on Earth.

Credit : Canada.ca

Picture Credit : Google