My Science School

A time capsule in the form of a 12-inch phonograph disc – called the Voyager Golden Record – was sent aboard Voyager 1 and 2. It was intended to communicate the story of our world to extraterrestrials, if any. The disc contains an auditory archive representing Earth’s sounds from greeting in every language to animal grunts. There is an eclectic selection of music including Eastern and Western classic and a variety of ethnic music. The 90 minutes of music was chosen after collaborating with historians, artists and folklorists to create the best first impression of our home planet.

 

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Between them, the two spacecraft have explored all the giant outer planets of our solar system – Jupiter, Saturn, Uranus and Neptune – as well as 49 moons, rings and magnetic fields of the planets.

• Voyager 2 is the first spacecraft to fly by all the four outer planets. It is the only spacecraft to visit Uranus and Neptune. It is the first spacecraft to image the rings of Jupiter, Uranus and Neptune. It discovered Neptune’s Great Dark Spot and its 1,600-km-per-hour wind.


• Voyager 1 found that Jupiter’s Moon 10 has active volcanoes and is the most geologically active place in the Solar System.


• Voyager 1 detected lightning on Jupiter.


• Voyager 1 detected a nitrogen-rich atmosphere on Saturn’s moon Titan, likely having clouds and rain of methane.


• In 1990, Voyager 1 took the first “family portrait” of the Solar System as it looked back toward home before its journey towards interstellar space. The portrait included the iconic image of planet Earth known as the Pale Blue Dot.


• On February 17, 1998, Voyager 1 passed Pioneer 10 to become the most distant human-made object in space.


• Both Voyager 1 and 2 suggested the existence of an ocean on Jupiter’s moon Europa.


• The Voyager spacecraft are the third and fourth human spacecraft to fly beyond all the planets in our solar system, outstripping the gravitational attraction of the Sun. Pioneers 10 and 11 were the first two to do so.

 

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After Voyager 1 departed from Saturn in November 1980, it began its journey towards interstellar space. It crossed over to interstellar space on August 25, 2012, leaving behind the heliosphere – the enormous magnetic bubble encompassing the Sun, the planets and solar wind.

Voyager 2 headed towards interstellar space after departing from Neptune in August 1989. It entered interstellar space on November 5, 2018, six years after its twin did the same.

According to NASA, Voyager 1, the faster of the two probes, is currently over 13.6 billion miles (22 billion km) from the Sun, while Voyager 2 is 11.3 billion miles (18.2 billion km) from the Sun. It takes light about 16.5 hours to travel from Voyager 2 to Earth. By comparison, light travelling from the Sun takes about eight minutes to reach Earth.

Factfile:

The heliosphere is a bubble around the Sun created by the outward flow of the solar wind and the opposing inward flow of the interstellar wind, while the heliopause marks the end of the heliosphere and the beginning of interstellar space.

 

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The spacecraft are powered by nuclear batteries (radioisotope thermoelectric generators) with electricity generated from heat produced by the decay of plutonium. While it is a pretty durable power source, it is not designed to last forever. The spacecraft loses power by roughly 4 watts every year. With power dwindling, some non-essential instruments on the spacecraft had to be shut off over the years to keep the mission going. For instance, in 2019, the primary heater for the cosmic ray subsystem instrument was turned off to reduce power consumption.

Each probe holds 11 instruments to carry out various tasks such as examining atmospheric chemistry, magnetic fields, charged particles, physical properties of the planets, and solar wind.

 

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Voyager 2 was launched on August 20, 1977. Its trajectory was designed to allow flybys of Jupiter, Saturn, Uranus, and Neptune.

Voyager 1 was launched first on a longer trajectory as it had to study the two outermost planets-Uranus and Neptune-in addition to Jupiter and Saturn. Voyager 1 was launched second in such a way that it could overtake Voyager 2, before reaching Jupiter.

 

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In 1977, the U.S. space agency, NASA, launched an ambitious space programme-the Voyager-to study the four outer planets of the Solar System, namely Jupiter, Saturn, Uranus and Neptune. The mission employed two robotic probes, Voyager 1 and Voyager 2, on different trajectories. While the former was tasked to make a close flyby of Jupiter and Saturn, the latter was set to pass these planets on a wider trajectory, and explore Uranus and Neptune in addition. These spacecraft were initially designed to last only five years, but they outlived their expectations and their mission was subsequently extended. They continued their mission was subsequently extended. They continued their cosmic journey beyond the solar system into interstellar space.

It’s been 42 years since launch and both Voyager 1 and 2 are going strong and sending back data from more than 11 billion miles from the Sun. The track record is indeed outstanding, but the Voyager Program cannot go on forever. In 2019, NASA announced that both spacecraft will likely be retired by mid-2020s, as their power has been gradually dropping.

As if it was a sign of things to come, Voyager2 experienced a power glitch last month, which forced the spacecraft to go offline. But the NASA team fixed the problem and the probe’s science instruments resumed work.

In this week’s Five Ws & One H, let’s take a closer look at the Voyager Program and its monumental contributions to the field of astronomy.

 

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For a planet to be habitable for humans, 1) It should be at a safe distance from the Sun – should be neither too hot, nor too cold; 2) It should contain liquid water, and 3) it should have a protective atmosphere that keeps the sun’s radiation out. There is only one planet in the solar system that satisfies all these conditions and that planet is earth. The next best option is mars.

Mars has many advantages. It is very close to earth-humans can reach the Red planet in less than six months from earth. A martian day is just over 24 hours long, roughly equivalent to a day on earth. 4) Mars has an atmosphere (though a thin one) that offers protection from cosmic and the sun’s radiation. Gravity on Mars is 38% that of our Earth, which is believed by many to be sufficient for the human body to adapt to. Evidence suggests that water may exist in the sub surface all over mars. With help from technology, humans can survive on Mars, whereas the survival chances are slim on other planets and their moons.

 

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The Quadrantids

The Quadrantids give off their own New Year’s fireworks show. Compared with most other meteor showers, they are unusual because they are thought to have originated from an asteroid. They tend to be fainter with fewer streaks in the sky than others on this list.

Visibility: Between the end of December and the second week of January

The Lyrids

There are records from ancient Chinese astronomers spotting these bursts of light more than 2,700 years ago. They blaze through the sky at about 107,000 mph and explode about 55 miles up in the planet’s atmosphere. This shower comes from Comet Thatcher, which journeys around the sun about every 415 years. Its last trip was in 1861 and its next rendezvous near the sun will be in 2276.

Visibility: Between April 16 and 26

The Eta Aquariids

The Eta Aquariids are one of two meteor showers from Halley’s comet. Its sister shower, the Orionids, will peak in October. Specks from the Eta Aquariids streak through the sky at about 148,000 mph, making it one of the fastest meteor showers. Its display is better seen from the Southern Hemisphere where people normally enjoy between 20 and 30 meteors per hour during its peak. The Northern Hemisphere tends to see about half as many.

Visibility: Between April 19 and May 28

The Southern Delta Aquariids

They come from Comet 96P Machholz which passes by the sun every five years. Its meteors, which number between 10 and 20 per hour, are most visible predawn, between 2 a.m. and 3 a.m. It tends to be more visible from the Southern Hemisphere.

Visibility: From July 12 to August 23

The Perseids

The Perseids light up the night sky when Earth runs into pieces of cosmic debris left behind by Comet Swift-Tuttle. The dirty snowball is 17 miles wide and takes about 133 years to orbit the sun. Its last go-round was in 1992.

Usually between 160 and 200 meteors dazzle in Earth’s atmosphere every hour during the display’s peak. They zoom through the atmosphere at around 133,000mph and burst about 60 miles overhead.

Visibility: From mid-July to mid-August,

The Orionids

The Orionids are an encore to the Eta Aquariid meteor shower, which peaks in May. Both come from cosmic material spewed from cosmic material spewed from Halley’s comet. Since the celestial celebrity orbits past Earth once every 76 years, the showers this weekend are your chance to view the comet’s leftovers until the real deal next passes by in 2061.

Visibility: From October 2 to November 7

The Leonids

The Leonids are one of the most dazzling meteor showers and every few decades it produces a meteor storm where more than 1,000 meteor can be seen an hour. Cross your fingers for some good luck – the last time the Leonids were that strong was in 2002. Its parent comet is called Comet-Temple/Tuttle and it orbits the sun every 33 years.

Visibility: During mid-November

The Geminids

The Geminids, along with the Quadrantids that peaked in January, are thought to originate not from comets, but from asteroid-like space rocks. The Geminids are thought to have been produced by an object called 3200 Phaethon. If you manage to see them, this meteor shower can brighten the night sky with between 120 and 160 meteors per hour.

Visibility: First two weeks of December

The Ursids

The Ursids tend to illuminate the night sky around the winter solstice in the Northern Hemisphere. They only shoot around 10 to 20 meteors per hour. They appear to radiate from Ursa Minor, and come from Comet 8P/ Tuttle.

Visibility: Between December 17 and 26

 

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If you spot a meteor shower, what you’re really seeing is the leftovers of the icy comets crashing into Earth’s atmosphere. Comets are sort of like dirty snowballs: As they travel through the solar system, they leave behind a dusty trail of rocks and ice that lingers in space long after they leave. When Earth passes through these cascades of comet waste, the bits of debris – which can be as small as grains of sand – pierce the sky at such speeds that they burst, creating a celestial fireworks display.

A general rule of thumb with meteor showers: You are never watching the Earth cross into remnants from a comet’s most recent orbit. Instead, the burning bits come from the previous passes. For example, during the Perseid meteor shower you are seeing meteors ejected from when its parent comet, Comet Swift-Tuttle, visited in 1862 or earlier, not from its most recent pass in 1992.

That’s because it takes time for debris from a comet’s orbit to drift into a position where it intersects with Earth’s orbit, according to Bill Cooke, an astronomer with NASA’s Meteoroid Environment Office.

The name attached to a meteor shower is usually tied to the constellation in the sky from which they seem to originate, known as their radiant. For instance, the Orionid meteor shower can be found in the sky when stargazers have a good view of the Orion constellation.

How to watch?

The best way to see a meteor shower is to get to a location that has a clear view of the entire night sky. Ideally, that would be somewhere with dark skies, away from city lights and traffic. To maximize your chances of catching the show, look for a spot that offers a wide, unobstructed view.

Bits and pieces of meteor showers are visible for a certain period of time, but they really peak visibly from dusk to dawn on a given few days. Those days are when Earth’s orbit crosses through the thickest part of the cosmic stream. Meteor showers can vary in their peak times, with some reaching their maximums for only a few hours and others for several nights. The showers tend to be most visible after midnight and before dawn.

It is best to use your naked eye to spot a meteor shower. Binoculars or telescopes tend to limit your field of view. You might need to spend about half an hour in the dark to let your eyes get used to the reduced light. Stargazers should be warned that moonlight and the weather can obscure the shows. But if that happens, there are usually meteor livestream like the ones hosted by NASA and by Slooh.

 

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People living in the Northern Hemisphere are in the best position to observe these beautiful meteor shows. For example, north America is right below the region of the sky where the January Quadrantids shower appears. Meteor showers can be seen at different times of the year depending on when Earth is going to pass through the comet’s or asteroid’s path. Some meteor showers happen annually; other appear once in a few years. Some of the best shows – meteor storms – happen just once or twice in a lifetime.

The best time to watch them is the pre-dawn hours, when the part of Earth you are standing on is facing the direction of Earth’s orbit. In the late evening hours the meteors are less frequent.

What can go wrong?

A bright moon can dim the light of the meteor show, fading out all but the brightest meteors. Local light pollution can affect our ability to view a shower. To view a meteor shower in all its glory, go to a rural location. Weather can also play spoilsport for a good view of meteor showers. A clear sky is what we need, which is why meteor showers during the summer are more visible than those that happen in the winter months.

 

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Meteor showers are named for the constellation from where they appear to emerge. For example, the Orionids meteor shower, which occurs in October every year, appears to be originating near the constellation Orion the Hunter, Perseid meteors seem to be coming from the Perseus constellation.

In some years you see more meteor showers than in others, depending on atmospheric conditions.

Astronomers sometimes find new meteor showers, like the Camelppardalis in 2014. The shower happened after the debris trail of Comet 209P/LINEAR intersected with Earth. Most meteors become visible when they come within 60 miles (96.5 km) of the Earth. On average, meteors can speed through the atmosphere at about 30,000 mph (48,280 kph) and reach temperatures of about 3,000 degrees Fahrenheit (1,648 degrees Celsius).

Let’s look at the popular meteor showers.

Leonids

The Leonids meteor shower is the brightest and most impressive one. It can produce a meteor storm that showers the sky with thousands of meteors per minute at its peak. In fact, the term “meteor shower” was copied after astronomers observed one of Leonids’ most impressive displays in 1833. The Leonids occur every November, but the shower’s most beautiful display happens at intervals of about 33 years. The last one lit up the Earth’s sky in 2002. A Leonid shower is not expected until 2028.

Perseids

Perseid may have been introduced into English from Italian Perseidi, coined by the Italian astronomer Giovanni Schiaparelli (1835-1910). Perseid ultimately comes from Greek Perseids “offspring or daughters of Perseus,” because the meteors looks like they are coming from the constellation Perseus. Perseid entered the English language in the 19th century. The Perseid meteor shower is from the comet Swift-Tuttle and happens in August. It is the most widely watched meteor shower of the year, peaking on 12 August with more than 60 meteors per minute.

Orionids

The Orionid meteor shower produces meteors from Halley’s comet, which orbits the sun every 75 to 76 years. The Orionid shower happens every October and can last for a week. It is a show of 50 to 70 shooting stars per hour at its peak.

Quadrantids

The Quadrantid meteor shower comes from the debris of an asteroid called 2003 EHI1. Astronomers believe this is part of a comet that broke apart centuries ago. The debris enters Earth’s atmosphere in early January. This meteor show is brief but spectacular.

Geminids

Like the Quadrantids, the Geminid meteor shower also came from dust particles of an asteroid called 3200 Phaeton. As the name suggests, the shower emerges from Gemini constellation. Meteor showers are mostly from comets, so having an asteroid as a parent make the Quadrantids and Geminids different from other meteor shows. The Geminids happen in December and spray up to 40 meteors per hour.

The Eta Aquarids

The Eta Aquarids is made up of the remnants of Halley’s coment. The show happens in May.

Lyrids

Lyrids, which has been written about for more than 2000 years, appears in late April.

 

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Astronauts aboard Apollo 16 installed a linear telescope called the Far Ultraviolet Camera/ Spectrograph on the moon in April 1972. The gold-plated 22-kg device mounted on a tripod was the first telescope used to make astronomical observations and take photographs of Earth in ultraviolet light from the surface of another planetary body. The astronauts brought back the film, leaving behind the telescope on the moon.

The Chinese were the next to install a robotic UV telescope on the moon in 2013, which is still functional. Operated remotely from Earth, it has observed stars, galaxies, quasars, novae, etc. Now NASA has plans of planting radio telescopes on the far side of the moon. Scientists believe that the far side of the moon being shielded from the radio signals of Earth is perfect for radio astronomy.

On Earth, there are many obstacles to observing the skies – our atmosphere, light pollution, weather, etc. In contrast, space telescopes like the Hubble and Chandra have given us brilliant images of the universe. So a telescope on the moon seems the most logical step.

An observatory on the moon has the advantage of 14 days of continuous darkness with no atmosphere or light pollution. This ensures uninterrupted and clear observation of astronomical objects.

On the other hand, the lack of atmosphere means that the linear surface experiences extreme temperature differences – the temperature can be as high as 100ºC  during the daytime and -173ºC  at night. The telescope has to be specially engineered to withstand such temperature extremes. The moon also experiences many moonquakes. Lastly, building an observatory on the moon is prohibitively expensive – it can cost more than $1 billion.

 

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