Space Sunday: Voyager at 45

Voyager: 45 years on. Credit: NASA

August and September 2022 mark the 45th anniversaries of the launches of Voyager 1 and Voyager 2, NASA’s twin interplanetary – and now interstellar – explorers.

Designed to take advantages of a planetary alignment which occurs once every 176 years, allowing the use the gravities of one of the outer planets to “slingshot” a vehicle on to the next, the two Voyager mission vehicles remain in operation today, and continue to stand at the forefront of our understanding of the local space surrounding our solar system.

Voyager 1 continues to set records as the furthest man-made object from Earth – it is now over 23.3 billion kilometres away – whilst Voyager 2 remains famous for giving us our first detailed views of Uranus and Neptune during its 20-year voyage through the outer solar system.

Products of the 1970s, the Voyager craft stand as museum pieces by today’s standards. Each has around 23 million times less memory than a modern cellphone, their communications systems can only transmit and receive data some 38,000 times slower than a modern cellular network, and they record the data they gather on an 8-track tape recorder prior to transmitting it back to Earth. Nevertheless, the amount of knowledge they have gathered and returned to us about the outer reaches of the solar system, the heliosphere (the bubble of space around the Sun in which the solar system resides), the heliopause (the boundary between that Sun-dominated “bubble” and the galaxy at large) and the realm of interstellar space beyond that bubble.

Operated by NASA’s Jet Propulsion Laboratory (JPL), the Voyager craft were launched in reverse order, with Voyager 2 lifting-off on August 20th, 1977 and Voyager 1 following on September 5th, 1977. The reason for this ordering was simple: during the development of the mission, Saturn’s moon Titan, known to have an atmosphere, was identified as a primary target for fly-by investigation, and so was assigned to Voyager 1.

Animation of Voyager 1’s trajectory around Jupiter: Pink – Voyager 1; Light Blue · Jupiter; Red · Io; Dark Blue -Europa; Yellow – Ganymede; Green · Callisto. Credit: Phoenix777

However, in order to reach the moon, the vehicle would have to follow a course that would carry it over Saturn’s northern reaches, and throw it “down” and out of the plane of the ecliptic and away from any chance of reaching the outer planets. Instead, Voyager 2 was tasked with completing the “grand tour” of the major planets – Jupiter, Saturn, Uranus and Neptune, and in order to achieve this, it would have to be launched first.

Even so, thanks to the nature of orbital mechanics requiring Voyager 2 to be thrown out on a more circular, “indirect” path towards Jupiter whilst Voyager 1 could be launched more directly towards Jupiter meant it could reach the gas giant first, arriving in January 1979, having “overtaken” Voyager 2 in December 1977. . Its passage through the Jovian system revolutionised our appreciation of the Galilean moons of the system, after which it travelled on to its November 1980 encounter with Saturn and then Titan.

Voyager 2’s more circular trajectory meant it did not reach Jupiter until July 1979, six months behind Voyager 1, but its route allowed it to make a much closer fly-by of Europa, the ice-covered Galilean moon, giving scientists the first hint of the nature of the mechanisms at work deep within the moon.

A transit of Io across Jupiter as imaged by Voyager 2 in July 2022. Credit: NASA/JPL

From here the vehicle journeyed on to an August 1981 encounter with Saturn and then Uranus in 1986 and then Neptune in August 1989, whilst Voyager 1 continued onwards toward the heliopause, all of which I covered in  Space Sunday: Voyager at 40.

In 2010, Voyager 1 commenced a two-year transition from the space dominated by the Sun and its outward flow of radiation, and the realm of interstellar space. The first indications that it was beyond the influence of the Sun’s radiation came in later 2012 – although it was not until March 2013 that this was empirically confirmed through analysis of multiple data returned by the vehicle.

Voyager 2 commenced its voyage through the heliopause in 2013; however, as it was still travelling within the plane of the ecliptic, it was effectively travelling through a “thicker” part of the “bubble wall” of the heliosphere, so it did not enter interstellar space until November 2018.

Even so, and possibly confusingly, neither craft have actually departed the solar system per se. This is because the “size” of the solar system is measured in two ways: the influence of the Sun’s outward flow of radiation and by the influence of its. Despite having passed through the former, both craft are sill within space affected by the latter, and neither will reach the Oort Cloud – the source region of long-period comets and seen as marking the outer limits of the Sun’s gravitational influence – for another 300 years.

As such, both of the nuclear-powered vehicles are now engaged in a multi-vehicle mission (having been joined in it by the likes of the New Horizons spacecraft, the Parker Solar Probe and others) referred to as the Heliophysics Mission.

The Heliophysics Mission fleet provides invaluable insights into our Sun, from understanding the corona or the outermost part of the sun’s atmosphere, to examining the sun’s impacts throughout the solar system, including here on Earth, in our atmosphere, and on into interstellar space. Over the last 45 years, the Voyager missions have been integral in providing this knowledge and have helped change our understanding of the sun and its influence in ways no other spacecraft can.

– Nicola Fox, director of the NASA’s Heliophysics Division

Voyager 2 left the heliosphere on November 5, 2018. Credit NASA/JPL
Today, as both Voyagers explore interstellar space, they are providing humanity with observations of uncharted territory. This is the first time we’ve been able to directly study how a star, our sun, interacts with the particles and magnetic fields outside our heliosphere, helping scientists understand the local neighbourhood between the stars, upending some of the theories about this region, and providing key information for future missions.

– Linda Spilker, Voyager’s deputy project scientist at JPL

Continue reading “Space Sunday: Voyager at 45”

This week at Seanchai Library: Evil Under the Sun + more in Second Life

Seanchai Library

It’s time to highlight another week of storytelling in Voice by the staff and volunteers at the Seanchai Library – and this week previews the launch of a very special event.

As always, all times SLT, and events are held at the Library’s home in Nowhereville, unless otherwise indicated. Note that the schedule below may be subject to change during the week, please refer to the Seanchai Library website for the latest information through the week.

Sunday, August 21st, 13:30: Evil Under the Sun

A Seanchai Library special event at SLEA.

The are times when even Belgian ex-pat detective Hercule Poirot needs a break from his chosen vocation; so when the opportunity arises for him to enjoy a holiday in Devon at the Jolly Roger Hotel (inspired by the Burgh Island Hotel) located on a tidal island just off the south Devonshire coast, he looks forward to the chance of a little R&R. 

Evil Under the Sun – a Seanchai Library special event

Whilst at the hotel, he encounters the other guests, notably Arlena Marshall who, desire being at the hotel with her husband Kenneth and step-daughter Linda, spends a lot of her time flirting with Patrick Redfern – much to the anger of Redfern’s wife, Christine and the disgust of her step-daughter. Also among the guests is Rosamund Darnley, who was once sweethearts with Kenneth Marshall.

Trying to keep himself apart from the intrigue, Poirot finds himself drawn into the middle of things and in need of his most particular deductive skills when Arlena Marshall is found dead on the sand of a secluded cove across the little island far from the hotel; a place where she apparently had a secret assignation…

Evil Under the Sun – a Seanchai Library special event

Join David Abbott, Corwyn Allen, Gloriana Maertens, Elrik Merlin, Kayden Oconnell, and Caledonia Skytower as they commence a reading of the 23rd adventure for Agatha’s Christie’s hero, first published in 1941, within the setting of the Jolly Roger Hotel. Should you wish, you can also enjoy the hotel’s grounds and facilities, partake of a little fun – and visit the cove which proved fatal for Arlena Marshall.

Monday, August 22nd, 19:00: More Mark Twain Shorts

Samuel Langhorne Clemens (1835 –1910) known by his pen name Mark Twain, was an American writer, humourist, entrepreneur, publisher, and lecturer. He was lauded as the “greatest humourist the United States has produced”, and William Faulkner called him “the father of American literature.”

Join Caledonia Shytower as she shares more of Twain’s wit and wisdom.

Tuesday, August 23rd

12:00 Noon: Russell Eponym

With music, and poetry in Ceiluradh Glen.

19:00: The Last Cuentista

There lived a girl named Petra Peña, who wanted nothing more than to be a storyteller, like her abuelita.

But Petra’s world is ending. Earth has been destroyed by a comet, and only a few hundred scientists and their children – among them Petra and her family – have been chosen to journey to a new planet. They are the ones who must carry on the human race.

Hundreds of years later, Petra wakes to this new planet – and the discovery that she is the only person who remembers Earth. A sinister Collective has taken over the ship during its journey, bent on erasing the sins of humanity’s past. They have systematically purged the memories of all aboard – or purged them altogether.

Petra alone now carries the stories of our past, and with them, any hope for our future. Can she make them live again?

Caledonia Skytower read Donna Barba Higuera’s 2021 winner of the  Newbery Medal and Pura Belpré Award.

Wednesday, August 25th, 19:00: Seanchai Flicks

A special for Star Wars month as the Seanchai cinema space plays host to videos and throw popcorn around!

Thursday, August 26th

19:00: Calydonian Boar Hunt Part 2

Shandon Loring reads one of the great heroic adventures in Greek legend, which took place a generation before the Trojan War: the hunt of a monstrous boar by a gathering of great heroes (excluding Heracles).

The boar had been sent by the Goddess Artemis to ravage the kingdom of Calydon in Aetolia, in revenge for the region’s king, Oeneus having slighted her when he forgot to name her in annual rites to the gods. The hunt is led by Meleager, and in most accounts is joined by Atalanta, the great huntress, who ultimately won the boar’s hide, leading to tragic results.

21:00 Seanchai Late Night

Contemporary Sci-Fi with Finn Zeddmore.