Category Archives: Space
Not one but two Aussie dishes were used to get the TV signals back from the Apollo 11 moonwalk
NASA
The role Australia played in relaying the first television images of astronaut Neil Armstrong’s historic walk on the Moon 50 years ago this July features in the popular movie The Dish.
But that only tells part of the story (with some fictionalisation as well).
What really happened is just as dramatic as the movie, and needed two Australian dishes. Australia actually played host to more NASA tracking stations than any other country outside the United States.
Read more:
How big is the Moon? Let me compare …
Right place, right time
Our geographical location was ideal as US spacecraft would pass over Australia during their first orbit, soon after launch. Tracking facilities in Australia could confirm and refine their orbits at the earliest possible opportunity for the mission teams.
To maintain continuous coverage of spacecraft in space as the Earth turned, NASA required a network of at least three tracking stations, spaced 120 degrees apart in longitude. Since the first was established in the US at Goldstone, California, Australia was in exactly the right longitude for another tracking station. The third station was near Madrid in Spain.
Australia’s world-leading place in radio astronomy was another factor, having played a key role in founding the science after the second world war. Consequently, Australian engineers and scientists developed great expertise in designing and building sensitive radio receivers and antennas.
While these were great at discovering pulsars and other stars, they also excelled at tracking spacecraft. When the CSIRO Parkes radio telescope opened in 1961 it was the most advanced and sensitive dish in the world. It became the model for NASA’s large tracking antennas.
CSIRO, Author provided
The Commonwealth Rocket Range at Woomera, South Australia, also allowed Australians to gain experience in tracking missiles and other advanced systems.
The dish you need is at Honeysuckle Creek
NASA invested a considerable amount in its Australian tracking facilities, all staffed and operated by Australians under a nation-to-nation treaty signed in February 1960.
For human spaceflight, the main tracking station was at Honeysuckle Creek, near Canberra. Its 26-metre dish was designed as NASA’s prime antenna in Australia for supporting astronauts on the Moon.
Hamish Lindsay, Author provided
NASA’s nearby Deep Space Network station at Tidbinbilla also had a 26-metre antenna but with a more sensitive radio receiver. It was called on to act as a wing station to Honeysuckle Creek, enhancing its capabilities, and ultimately tracked the orbiting command module during Apollo 11.
Over in Western Australia, Carnarvon’s smaller 9-metre antenna was used to track the Apollo spacecraft when initially in Earth orbit, as well as to receive signals from the lunar surface experiments.
To augment the receiving capabilities of these stations, the 64-metre Parkes radio telescope was asked to support Apollo 11 while astronauts were on the lunar surface. The observatory’s director, John Bolton, was prepared to accept a one-line contract:
The Radiophysics Division would agree to support the Apollo 11 mission.
The original plan
The decision to broadcast the first moonwalk was almost an afterthought.
Originally, the tracking stations were to receive only voice communications and spacecraft and biomedical telemetry. What mattered most to mission control was the vital telemetry on the status of the astronauts and the lunar module systems.
Since Parkes was an astronomical telescope, it could only receive the signals, not transmit. It was regarded as a support station to Honeysuckle Creek, which was also tasked with receiving the signals from the lunar module, Eagle.
When the decision was made to broadcast the moonwalk, Parkes came into its own. The large collecting area of its dish provided extra gain in signal strength, making it ideal for receiving a weak TV signal transmitted 384,000km from the Moon, using the same power output as two LED lights today.
One giant leap
On Monday, July 21 1969, at 6.17am (AEST), astronauts Neil Armstrong and Buzz Aldrin landed the Eagle lunar module on the Sea of Tranquillity.
It occurred during the coverage period of the Goldstone station, while the Moon was still almost seven hours from rising in Australia.
The flight plan had the astronauts sleeping for six hours before preparing to exit the lunar module. Parkes was all set to become the prime receiving station for the TV broadcast.
This changed when Armstrong exercised his option for an immediate walk – five hours before the Moon was to rise at Parkes. With this change of plan, it seemed the moonwalk would be over before the Moon even rose in Australia.
But as the hours passed, it became evident that the process of donning the spacesuits took much more time than anticipated. The astronauts were being deliberately careful in their preparations. They also had some difficulty in depressurising the cabin of the lunar module.
Meanwhile, moonrise was creeping closer in Australia. Staff at Honeysuckle Creek and Parkes began to hope they might get to track the moonwalk after all – at least as a backup to Goldstone in the US.
Bad weather hits
The weather at Parkes on the day of the landing was miserable. It was a typical July winter’s day – grey overcast skies with rain and high winds. During the flight to the Moon and the days in lunar orbit, the weather at Parkes had been perfect, but this day, of all days, a violent squall hit the telescope.
CSIRO/David Cooke, Author provided
Still, the giant dish of the Parkes radio telescope was fully tipped down to its 30-degree elevation limit (the telescope’s horizon is 30 degrees above the true horizon), waiting for the Moon to rise in the north-east.
As the Moon slowly crept up to the telescope’s horizon, dust was seen racing across the country from the south. The dish, being fully tipped over, was at its most vulnerable, acting like a huge sail.
The winds picked up and two sharp gusts exceeding 110km/h struck the large surface, slamming it back against the zenith angle drive pinions that controlled the telescope’s up and down motion. The control tower shuddered and swayed from this battering, creating concern in all present.
The atmosphere in the control room was tense, with the wind alarm ringing and the 1,000-ton telescope ominously rumbling overhead.
Parkes had two radio receivers installed in the focus cabin of the telescope. The main receiver was on the focus position and a second, less sensitive receiver was offset a very short distance away, which gave it a view just below the main receiver.
Fortunately, as the winds abated, the Moon rose into the field-of-view of the telescope’s offset receiver, just as Aldrin activated the TV at 12.54pm (AEST). It was a remarkable piece of timing.
CSIRO/David Cooke, Author provided
The 64m antenna at Goldstone, the 26m antenna at Honeysuckle Creek and the 64m dish at Parkes all received the signal simultaneously.
At first, NASA switched between the signals from Goldstone and Honeysuckle Creek, searching for the best-quality TV picture.
After finding Goldstone’s image initially upside down and then of poor quality, Houston selected Honeysuckle’s incoming signal as the one used to broadcast Armstrong’s “one giant leap” to the world.
Eight minutes into the broadcast, at 1.02pm (AEST), the Moon finally rose high enough to be received by Parkes’ main, on-focus receiver. The TV quality improved, so Houston switched to Parkes and stayed with it for the remainder of the two-and-a-half hours of the moonwalk, never switching away.
Honeysuckle continued to concentrate on their main task of communications with the astronauts and receiving that vital telemetry data.
CSIRO/David Cooke, Author provided
Throughout the moonwalk, the weather remained bad at Parkes. The telescope operated well outside safety limits for the entire duration. It even hailed toward the end, but there was no degradation in the TV signal.
It’s hailing on the dish.
CSIRO, Author provided321 KB (download)
CSIRO, Author provided321 KB (download)
The moonwalk lasted a total of 2 hours, 31 minutes and 40 seconds, from the time the Eagle’s hatch opened to the time the hatch closed.
Australians saw it first
In Australia, the Apollo 11 feed was split. One feed was sent to NASA mission control for broadcast around the world. The other went directly to the ABC’s Gore Hill studios, in Sydney, for distribution to Australian TV networks.
As a result Australians watched the moonwalk, and Armstrong’s first step through Honeysuckle, just 300 milliseconds before the rest of the world.
Read more:
We need to protect the heritage of the Apollo missions
An estimated 600 million people, one-sixth of the world’s population at the time, watched the historic Apollo 11 moonwalk live on TV. At the time it was the greatest television audience in history. As a proportion of the world’s population, it has not been exceeded since.
The success of the Apollo 11 mission was due to the combined effort, dedication and professionalism of hundreds of thousands of people in the United States and around the planet.
Australians from Canberra to Parkes, remote Western Australia to central Sydney played a critical role in helping broadcast that historic moment to an awestruck world.
Parkes gives NASA the best TV pictures yet.
NASA/CSIRO, Author provided267 KB (download)
NASA/CSIRO, Author provided267 KB (download)
NASA
You can hear more about the Moon landing in our special podcast series, To the Moon and beyond.
John Sarkissian, Operations Scientist, CSIRO
This article is republished from The Conversation under a Creative Commons license. Read the original article.
We need to protect the heritage of the Apollo missions
NASA
Alice Gorman, Flinders University
It’s 50 years since the two Apollo 11 astronauts – Neil Armstrong and Buzz Aldrin – spent 22 hours collecting samples, deploying experiments and sometimes just playing in the Sea of Tranquillity on the Moon.
In doing so, they created an archaeological site unique in human history.
Now, with what’s been called the New Space Race and plans to return to the Moon, the Apollo 11 and other lunar sites are under threat. We need to protect this heritage for future generations.
Read more:
How big is the Moon? Let me compare …
Apollo 11’s archaeological site
The archaeological site of Tranquillity Base consists of the hardware left behind, as well as the marks made in the lunar surface by the astronauts and instruments.
NASA
The hardware component includes the landing module, the famous flag (no longer standing), experiment packages, cameras, antennas, commemorative objects, space boots and many other discarded objects – more than 106 in total.
Around these objects are the first human footprints on the Moon as well as the tracks the astronauts made walking around, and the places where they dug out samples of rock and dust to take back to Earth for scientific analysis.
The artefacts, traces and the landscape constitute an archaeological site. The relationships between them can be used by archaeologists to study human behaviour in this environment so different to Earth, with one-sixth terrestrial gravity and no atmosphere.
Assessing the heritage value
Not only this, but the site has heritage value for people on Earth. To assess this, we can look at a number of categories of cultural significance. Those in the Burra Charter are widely used across the world for heritage assessment.
Historic: There is no doubt that, as the first place where humans set foot on another celestial body, this is a very important place in global history. It also represents the ideologies of the Cold War (1947-1992) between the US and the USSR.
NASA
Scientific: What can we learn from the site? More particularly, what questions would we no longer be able to answer if Tranquillity Base was damaged or destroyed?
This is not just about archaeological research into human behaviour on the Moon. Apollo 11 has been exposed to the harsh lunar environment for 50 years. The surfaces of the hardware are accidental experiments in themseves: they carry the record of 50 years of micrometeorite and cosmic ray bombardment. Finding out how well the materials have survived can also provide information about how to design future missions.
Aesthetic: This type of cultural significance is about how we experience a place. While we can’t assess it in person, there are films and photographs that give us a feeling for the place. This includes the light, shadows and colours of the lunar surface from the perspective of the human senses. The aesthetic qualities have inspired many artists and musicians, including astronaut Alan Bean who devoted his post-Apollo 12 life to painting the Moon.
NASA
Social: This is about the value that contemporary communities place on the site. For the 600 million-plus people who watched the television broadcast of the landing, it was a life-changing moment representing the ingenuity of human technology and visions of a space-age future.
But the mission did not mean the same for everyone. Some African-Americans protested against Apollo 11, seeing it as a waste of resources when there was such great economic and social disparity between white and black communities in the US. For them, it was a sign of human failure rather than a triumph.
The larger the community that has an interest in a heritage place, the higher its level of social significance. It could be argued that Apollo 11 has outstanding universal significance, like places on the World Heritage List (unfortunately the World Heritage Convention cannot be applied to space).
What are the threats?
In the past few years we have seen an increase in proposed missions to return to the Moon. Some have stated their intention to revisit the Apollo sites, by human crew or robot – and this could lead to the removal of material, for souvenirs or science.
But the sites are both fragile and unprotected. The two primary risks to their survival are uncontrolled looting, and damage from abrasive and sticky lunar dust.
NASA
Removing material from the sites damages the integrity of the artefacts and the relationships between them. A casual visit could erase the original footprints and astronaut traverses. The corrosive dust disturbed by surface activities could wear away the materials.
Dust was a problem for all the crewed lunar missions. Apollo 16 commander John Young said: “Dust is the number one concern in returning to the Moon.”
The dust can be stirred up by plumes from landing or ascending vehicles, driving vehicles, walking on the surface, or, in the next phase of lunar settlement, by construction and industrial activities, such as mining.
Attempts at protection
The Outer Space Treaty of 1967 forbids making territorial claims in space. Applying any national heritage legislation to a place on the Moon could be interpreted as a territorial claim.
The US states of California and New Mexico have placed the Apollo 11 artefacts left on the Moon on a heritage list. They can do this because, under the treaty, the US legally owns the artefacts. But this does not protect the site itself.
NASA
NASA has established a set of heritage guidelines for its sites on the Moon. The guidelines propose buffer zones around these areas, inside which no-one should enter. They make recommendations for approaching the sites to minimise dust disturbance.
In May 2019, a bill called the One Small Step to Protect Human Heritage in Space Act was introduced to the US Congress. Its purpose is:
To require any Federal agency that issues licences to conduct activities in outer space to include in the requirements for such licences an agreement relating to the preservation and protection of the Apollo 11 landing site, and for other purposes.
But the bill applies only to Apollo 11 and does not have similar requirements for the five other Apollo landing sites. It also applies only to US missions. It’s a step in the right direction, but there is still much more to be done.
NASA
Only in the last decade has the idea of space archaeology gained legitimacy. Until recently, there was no urgency to establish an international framework to manage the cultural values of lunar heritage.
Read more:
Why the Moon is such a cratered place
Now we’re in a new situation. On Earth, it’s common for industrial or urban activities that disturb the environment to be subject to an environmental impact assessment, which includes heritage.
Even when there are no laws to force companies to pay attention to heritage, many consider it important to seek a Social Licence to Operate – support from stakeholder communities to continue their activities.
Everyone on Earth is a stakeholder in the heritage of the Moon. Fifty years from now, what will remain of the Apollo 11 and other sites? What new meanings will people draw from it?
Alice Gorman, Senior Lecturer in Archaeology and Space Studies, Flinders University
This article is republished from The Conversation under a Creative Commons license. Read the original article.
50 years ago: Australia and the Apollo 8 mission that sent a Christmas message from the Moon
Apollo 8: Launch countdown …
NASA387 KB (download)
NASA387 KB (download)
It was on December 21, 1968, that Apollo 8 launched from Cape Kennedy, in Florida, sending US astronauts Frank Borman, James Lovell Jr and William Anders on the world’s first human mission to the Moon.
NASA
A few days later – on Christmas Eve Houston time, Christmas Day in Canberra – the three astronauts had just passed over the Sea of Tranquility on the Moon and were approaching a lunar sunrise when they sent back a historic Christmas message to the people of Earth.
Read more:
Curious Kids: Why can I sometimes see the Moon in the daytime?
A few hours later, an Australian tracking station took over as prime data and relay receiving site for the mission.
Located among the gum trees and kangaroos just outside Canberra, Honeysuckle Creek Tracking Station listened for the crucial acquisition of signal as the spacecraft emerged from behind the Moon on its final orbit, having fired its engine to return to Earth.
Hamish Lindsay, Author provided
Honeysuckle Creek received and retransmitted astronaut Jim Lovell’s first words to Mission Control on their way back home:
Apollo 8: ‘Santa Claus’
NASA268 KB (download)
NASA268 KB (download)
Houston, Apollo 8, over. Please be informed there is a Santa Claus.
Apollo 8: the mission that ‘saved 1968’
The Apollo 8 mission was just the second crewed outing for the type of spacecraft that would ferry astronauts to the first lunar landing the following year.
Initially the mission was to test the lunar module in the safety of Earth orbit. But with that spacecraft still not ready, NASA took the bold decision to launch a command and service module around the Moon by itself as a precursor to a crewed landing.
NASA
Also spurring the decision was the belief that the Russians were close to launching their own Moon shot.
Apollo 8 was the first manned launch of a massive Saturn V rocket, the first rendezvous with the Moon, and the first time human eyes saw the far side of the Moon.
The six-day mission was a spectacular success. The three astronauts completed ten orbits of the Moon and the spacecraft and ground support were thoroughly tested.
NASA was now one step closer to that “giant leap for mankind”.
NASA
The astronauts also took the now iconic “Earthrise” photograph of the Earth behind a lunar landscape. This was a profound image, containing all of humanity, bar the three astronauts.
Read more:
Earthrise, a photo that changed the world
Although the religious nature of Apollo 8’s Christmas Bible reading caused some controversy after the mission, it was heard by hundreds of millions of people.
That the message was transmitted from further than humans had ever been – the distance led to a delay of one second into all communications – made it all the more remarkable.
One member of the public famously wrote to NASA to credit the mission with having “saved 1968”, a year otherwise plagued by war and protests over Vietnam, civil rights and other issues.
Supporting Apollo down under
The Apollo program that enabled the first humans to leave Earth’s orbit was overwhelmingly an American endeavour, but not exclusively so.
At a time before dedicated spacecraft communication satellites, NASA relied on a chain of tracking and data relay stations around the world to communicate with Earth-orbiting satellites and astronauts. To ensure adequate coverage, these included stations in far off places such as Madagascar, Nigeria and Woomera in South Australia.
For missions further into the solar system, NASA used three principal stations: one near Canberra in Australia which included Honeysuckle Creek, another at Madrid in Spain, and the third at Goldstone in California.
At least one of these three stations would have a dish that would face the spacecraft at any given time, receiving their communications and passing them to Mission Control in Houston, Texas.
Hamish Lindsay, Author provided
This was a global network of instantaneous data and voice communications, at a time when even a single international telephone call had to be booked weeks in advance and was extremely expensive.
For Apollo 8, Honeysuckle Creek received telemetry and voice communications when the spacecraft first went into orbit behind the Moon, when it first emerged back into communication with Earth, and when it began its fiery re-entry into the Earth’s atmosphere on December 27.
Australian technicians were responsible for the vital task of aligning the dishes with the spacecraft and troubleshooting any problems that might arise with the equipment, a not unlikely occurrence with 1960s technology.
National Archives of Australia (A1500, K20417), CC BY
Support for other missions
While only Lovell would fly again, on the ill-fated Apollo 13 mission, all the equipment and procedures tested on Apollo 8 – the spacecraft, the NASA technicians and the global network of tracking stations – would support the remaining Apollo flights.
Honeysuckle Creek was shut down and dismantled in 1981 but its receiving dishes moved not far away to Tidbinbilla.
Read more:
Australia’s part in 50 years of space exploration with NASA
Australia continues to play an important role in space exploration with scientists and technicians still supporting support NASA.
They are involved as part of the Deep Space Network, tracking spacecraft such as the New Horizon’s mission to Pluto and multiple missions to Mars.
As for the two Voyager spacecraft, which have travelled the furthest of any object made by humans, they now only have contact with Earth via Australia.
Even on Christmas Day, Tidbinbilla will be receiving messages from spacecraft around the Solar System.
So when you send a Christmas message this year, spare a thought for those messages from the Moon 50 years ago, and the role Australian scientists played in receiving them.
Tristan Moss, Lecturer, UNSW
This article is republished from The Conversation under a Creative Commons license. Read the original article.
Aboriginal traditions describe the complex motions of planets, the ‘wandering stars’ of the sky
Flickr/Indigo Skies Photography, CC BY-NC-ND
Duane W. Hamacher, Monash University
Aboriginal and Torres Strait Islander readers are advised that this story may contain images and voices of people who have died.
The five planets we can see by naked eye were known to the ancient Greeks as “asteres planetai”, meaning “wandering stars”, due to their wandering journey across the sky relative to the fixed stars. This is where we get the word “planet”.
But knowledge of the planets and their movements goes back much further, being prominent in the traditions of the oldest continuing cultures in the world.
Recent research reveals a wealth of information about the planets and their complex motions in the Knowledge Systems of Indigenous Australians.
The wandering stars
These systems show that Aboriginal and Torres Strait Islander people carefully observe the complex motions of the planets.
Read more:
The stories behind Aboriginal star names now recognised by the world’s astronomical body
In Wardaman traditions, the planets are ancestor spirits who walk across a celestial road. Wardaman Elder Bill Yidumduma Harney calls it the Dreaming Track in the Sky.
Astronomers call this celestial road the zodiac – the region of sky nine degrees on either side of the ecliptic (the path of the Sun). As the planets orbit the Sun in roughly the same plane, they all are visible along this band of the sky.
ESA
Uncle Yidumduma describes the planet-ancestors moving across the sky much like we walk down a busy footpath. We sometimes hurriedly pass each other, or slow down for a chat. Occasionally, we even stop and turn backwards to chat with someone before moving forward again.
Astronomers call this phenomenon retrograde motion. It is an optical effect that occurs as the planets orbit the Sun at different distances and velocities. It means the planets can appear to slow down and move backwards for a time before returning to their normal motion.
ESA
There are five planets visible to the naked eye and right now, and you can see at least four – Venus, Mars, Jupiter and Saturn – in the sky at sunset from most locations across Australia. All of these planets are currently in retrograde motion.
Stellarium.
The (non) twinkling stars
Aboriginal and Torres Strait Islander people recognise that these wandering stars generally do not twinkle – a phenomenon the Meriam people of the eastern Torres Strait call epreki and observe to predict weather and seasonal change.
But sometimes they do twinkle, particularly if they are very low on the horizon. Kamilaroi people of northern New South Wales say Venus occasionally twinkles when it’s low in the sky. They say it’s an old man who told a rude joke and has been laughing ever since.
In the traditions of the Euahlayi people – neighbours of the Kamilaroi – Venus and Mars relate to songlines and trade with Arrernte people of the Central Desert.
During special ceremonies, the Arrernte travel from the MacDonnell Ranges to Quilpie in southwest Queensland, bringing with them a red stone that signifies Mars. The Euahlayi people bring a green and blue stone to the ceremony, representing Venus. They are seen as the different-coloured eyes of the creator spirit Baayami.
Venus – the Morning and Evening Star
Venus is commonly known in many Aboriginal and Torres Strait Islander cultures as both the Morning and Evening Star.
In the Dreaming stories of the Western Arrernte, a celestial baby fell from the Milky Way, striking the ground and creating the giant meteorite crater called Tnorala (Gosses Bluff). The child’s parents – the Morning and Evening Stars – take turns searching for their lost child to this day.
Arrernte mothers warn their children not to look at the Morning or Evening Star, as the celestial parents might mistake them for their lost child and carry them away to the sky.
In Yolngu traditions of Arnhem Land, a special ceremony is held to signify the rising of the Creation ancestor, Banumbirr (Venus), between the mainland and a Burralku – the sacred island of the dead.
The ceremony starts at dusk and continues through the night, reaching a climax when Banumbirr rises a few hours before dawn as Venus transitions from the Evening Star to the Morning Star. Banumbirr communicates with the people through a faint rope that holds her close to the Sun.
Astronomers call this zodiacal light – the glow of dust in the plane of the Solar System.
ESO
The first rising of Venus as the Morning Star, after it transitions from the Evening Star, occurs every 584 days. Astronomers refer to this as Venus’ synodic period.
Read more:
Stars that vary in brightness shine in the oral traditions of Aboriginal Australians
When astronomer Ray Norris asked a Yolngu elder how the people know when to hold the Banumbirr ceremony, the elder responded: “We count the days!”
That’s an achievement not often recognised, and just another example of the detailed understanding of these “wandering stars” in the Knowledge Systems of Indigenous Australians.
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Kirsten Banks, a Wiradjuri woman and astrophysics graduate from the University of New South Wales, contributed to this research and this article. She can be contacted at astronomerkirsten@gmail.com
Duane W. Hamacher, Senior Research Fellow, Monash University
This article was originally published on The Conversation. Read the original article.
How ancient cultures explained comets and meteors
Eve MacDonald, Cardiff University
Comets and meteors have fascinated the human race since they were first spotted in the night sky. But without science and space exploration to aid understanding of what these chunks of rock and ice are, ancient cultures often turned to myth and legend to explain them.
The Greeks and Romans believed that the appearance of comets, meteors and meteor showers were portentous. They were signs that something good or bad had happened or was about to happen. The arrival of a comet could herald the birth of a great figure, and some people have even argued that the star in the sky which the Persian Magi followed to Bethlehem to see the newborn Jesus was actually a comet.
In the spring of 44BC, a comet that appeared was interpreted as a sign of the deification of Julius Caesar, following his murder. Caesar’s adopted son Octavian (soon to be the Emperor Augustus) made much of the comet, which burned in the sky during the funerary games held for Caesar. This portentous event was frequently celebrated in the ancient sources. In his epic poem, the Aeneid, Virgil describes how “a star appeared in the daytime, and Augustus persuaded people to believe it was Caesar”.
Wikimedia/Classical Numismatic Group, Inc., CC BY-SA
Augustus celebrated the comet and the deification of his father on coins (it did help to be the son of a god when trying to rule the Roman Empire), and many examples survive today.
Meteor showers
The Roman historian Cassius Dio referred to “comet stars” occurring in August 30BC. These are mentioned as among the portents witnessed after the death of the Egyptian queen Cleopatra. Experts are not entirely sure what it means when Dio uses the plural term “comet stars”, but some have connected this recorded event to the annual Perseid meteor shower.
Though it retains an ancient Greek name, we now know that the arrival of the Perseid meteor shower every August is actually the Earth’s orbit passing through debris from the Swift-Tuttle comet.
British Museum, CC BY-NC-SA
The meteor shower is named for the Perseidai (Περσείδαι), who were the sons of the ancient Greek hero Perseus. Perseus was a legendary figure with a fine family pedigree – he was the mythical son of Zeus and Argive princess Danaë (she of the golden rain). Perseus earned himself a constellation after a number of epic adventures across the Mediterranean and Near East that included the frequently illustrated murder of the Gorgon sister, Medusa.
Another of Perseus’s celebrated acts was the rescue of the princess Andromeda. Abandoned by her parents to placate a sea monster, the princess was found by Perseus on a rock by the ocean. He married her and they went on to have seven sons and two daughters. Sky watchers believed that the constellation Perseus, located just beside Andromeda in the night sky, was the origin of the shooting stars they could see every summer, and so the name Perseid stuck.
Wikimedia, CC BY-SA
Tears and other traditions
In Christian tradition the Perseid meteor shower has long been connected to the martyrdom of St Lawrence. Laurentius was a deacon in the early church at Rome, martyred in the year 258AD, during the persecutions of the Emperor Valerian. The martyrdom supposedly took place on August 10, when the meteor shower was at its height, and so the shooting stars are equated to the saint’s tears.
Detailed records of astronomical events and sky watching can be found in historical texts from the Far East too. Ancient and medieval records from China, Korea and Japan have all been found to contain detailed accounts of meteor showers. Sometimes these different sources can be correlated, which has allowed astronomers to track, for example, the impact of Halley’s comet on ancient societies both east and west. These sources have also been used to find the first recorded observation of the Perseid meteor shower as a specific event, in Han Chinese records of 36AD.
Though the myths and legends may make one think that ancient civilisations had little scientific understanding of what meteors, comets and asteroids could be, this couldn’t be farther from the truth. The early astronomers of the Near East, those who created the Babylonian and Egyptian calendars, and astronomical data were – by far – the most advanced in antiquity. And a recent study of ancient cuneiform texts has proven that the Babylonian ability to track comets, planetary movements and sky events as far back as the first millennium BC involved a much more complex geometry than had been previously believed.
Eve MacDonald, Lecturer in Ancient History, Cardiff University
This article was originally published on The Conversation. Read the original article.
A brief history of Martian exploration – as the InSight Lander prepares to launch
NASA
Helen Maynard-Casely, Australian Nuclear Science and Technology Organisation
Roughly every two years Mars and Earth wander a bit closer to each other, making the leap between these two planets a little easier. In July this year, Mars will only be about 58 million kilometres away – and NASA is set to take advantage by launching their next mission to the red planet in May 2018. The InSight Lander, will be the first Mars mission to investigate the planet’s “inner space”, and will listen for marsquakes to investigate the crust, mantle, and core.
InSight will join two rovers currently exploring the surface of Mars, and 14 spacecraft that are in orbit about it – albeit only six of which are currently sending us data.
Read more:
Ice mined on Mars could provide water for humans exploring space
Why does Mars, the red planet, have such a hold over us?
There are, after all, seven (or eight) other planets to explore – and yet we seem to have such a hang up on this one.
I guess it’s the tantalising nature of Mars. Here is a planet that we could conceivably walk on (unlike the gas giants), without being crushed by atmospheric pressure (like on Venus), having to deal with the radiation of being closer to the sun (Mercury) or just being far too far away (like Pluto). It calls to us through science fiction and fact, a planet that is so like our own Earth, but so unlike it at the same time.
The six current operational missions show that the fascination with Mars isn’t limited to one country, as European, Russian, American and Indian space agencies all have stakes in these crafts.
For comparison: our other nearest neighbour, Venus, only has one spacecraft currently in orbit about it, Akatsuki the spacecraft that wouldn’t quit. In fact, after the dramatic ending of the Cassini spacecraft, the only other planet currently being orbited by an Earth-built satellite is Jupiter, with the Juno mission.
Read more:
Juno mission unveils Jupiter’s complex interior, weather and magnetism
Water on Mars
But, while our progress to walking on Mars has been very slow, our progress in understanding our neighbour has been really quite impressive. When I started my planetary science degree in 2001, the course did not include sedimentology, the branch of geology that investigates how water has shaped rocks. It was deemed there was no point as no water has been seen on any other planet.
By the time I was in third year, the first years students behind me were getting well versed in how water could push around sand, silt and clay on other planets.
Finding water on Mars had been an obsession to many, and thanks to data from Mars rovers Spirit, Opportunity and latterly Curiosity we know that it’s there – just trapped in the rocks. A couple of years ago it was thought that we had even found water flowing on the surface of Mars, but that evidence is (ahem) drying up now.
Read more:
Dear diary: another day in the life on Mars
However, whether the water flows or is trapped in the rocks, the next question is where is the rest of it? If many of the rocks we see on Mars had been laid down by water – where is that water now?
The answer would be tangled up with the fate of Mars’s atmosphere. Though pitifully thin now, it must have been thick enough in the past to support flowing water on the surface. The mission of the spacecraft Maven (along with others) has been investigating this question – and all evidence is pointing to the Sun as the culprit for Mars’ missing atmosphere, with the solar wind gradually stripping it away.
Mars’ surface
It’s often touted that we know more about the surface of Mars than we do the bottom of our own oceans – and in terms of mapping resolution that’s true. Through the efforts of four orbiting missions we know how old most of the surface is, as well as how active it has been.
You can spend a joyful afternoon of procrastination flitting through HiRISE images that show sweeping dunes and pock-marked plains on Mars. With these images we can really apply our understanding of processes on Earth to what makes up the surface of Mars – from the formations of geological features, the movement of dust and sand and how the ice caps change through the seasons.
What’s inside Mars?
So we know there is water on Mars, we know where its atmosphere went and also the shifts of its sands – but there’s a missing piece of the puzzle. What’s on the inside?
To be fair, in this respect the interior of our own Earth is just as much of a mystery – but we have had centuries of seismic studies. From monitoring the passage of earthquakes through our planet we have built a picture of the layers that make up its interior. From that we’ve been able to undertake experiments that recreate the conditions and add more to that picture. At the moment we can only guess at the conditions within the interior of Mars – something that the InSight mission will answer.
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Before we colonise Mars, let’s look to our problems on Earth
After this, the next hurdle will be getting something back from Mars. We have a handful of meteorites that we know came from Mars, but having a sample that’s been collected and returned from a known location will priceless. NASA’s next rover, Mars 2020, will plan to do just this – but the return to Earth bit is still to be worked out.
From sample return to human exploration is still a massive step, and will require a number of innovations to get there. But with the knowledge we’ve built from the missions over the last decade, it’s becoming more of a reality.
Helen Maynard-Casely, Instrument Scientist, Australian Nuclear Science and Technology Organisation
This article was originally published on The Conversation. Read the original article.
The stories behind Aboriginal star names now recognised by the world’s astronomical body
Bill Yidumduma Harney, CC BY
Duane W. Hamacher, Monash University
Four stars in the night sky have been formally recognised by their Australian Aboriginal names.
The names include three from the Wardaman people of the Northern Territory and one from the Boorong people of western Victoria. The Wardaman star names are Larawag, Wurren and Ginan in the Western constellations Scorpius, Phoenix and Crux (the Southern Cross). The Boorong star name is Unurgunite in Canis Majoris (the Great Dog).
They are among 86 new star names drawn from Chinese, Coptic, Hindu, Mayan, Polynesian, South African and Aboriginal Australian cultures.
These names represent a step forward by the International Astronomical Union (IAU) – the global network of the world’s roughly 12,000 professional astronomers – in recognising the importance of traditional language and Indigenous starlore.
What’s that star called?
Many cultures around the world have their own names for the stars scattered across the night sky. But until 2016, the IAU never officially recognised any popular name for any star.
Instead, each star is assigned a Bayer Designation, thanks to a book published in 1603 by German astronomer Johann Bayer. He systematically assigned visible stars a designation: a combination of a Greek letter and the Latin name of the constellation in which it is found.
He gave the brightest star in a constellation the letter Alpha, then the next brightest star Beta, and so on down the list. For example, the brightest star in the Southern Cross is Alpha Crucis.
Flickr/Eddie Yip, CC BY-SA
The IAU recognised that the lack of official star names was a problem. So the Working Group on Star Names (WGSN) was formed in 2016 to officially assign popular names to the hundreds of stars visible in the night sky.
That year the working group officiated 313 star names, derived mainly from the most commonly used Arabic, Roman and Greek names in astronomy. But the list contained few Indigenous or non-Western names.
That changed last year when the WGSN formally approved the 86 new star names drawn from other cultures. Aboriginal Australian cultures stretch back at least 65,000 years, representing the most ancient star names on the list.
The WGSN is looking to identify even more star names from Australia and other Indigenous cultures around the world. As Indigenous cultures have a rich collection of names for even the faintest stars, many new star names could gain IAU recognition.
So what do we know about these four stars and the origin of their names?
Wardaman star names
The Wardaman people live 145km southwest of Katherine in the Northern Territory. Wardaman star names come from Senior Elder Bill Yidumduma Harney, a well known artist, author and musician.
He worked with Dr Hugh Cairns to publish some of his traditional star knowledge in the books Dark Sparklers (2003) and Four Circles (2015). These books remain the most detailed records of the astronomical knowledge of any Aboriginal group in Australia.
Jayne Nankivell, Author provided
Larawag (Epsilon Scorpii)
The stars of the Western constellation Scorpius feature prominently in Wardaman traditions, which inform the procedures of initiation ceremonies.
Merrerrebena is the wife of the Sky Boss, Nardi. She mandates ceremonial law, which is embodied in the red star Antares (Alpha Scorpii). Each star in the body of Scorpius represents a different person involved in the ceremony.
Larawag is the signal watcher, noting when only legitimate participants are present and in view of the ceremony. He gives the “All clear” signal, allowing the secret part of the ceremony to continue.
Epsilon Scorpii is an orange giant star, lying 63.7 light years away.
International Astronomical Union, CC BY
Wurren (Zeta Phoenicis)
Wurren means “child” in Wardaman. In this context it refers to the “Little Fish”, a child of Dungdung – the life-creating Frog Lady. Wurren gives water to Gawalyan, the echidna (the star Achernar), which they direct Earthly initiates to carry in small bowls. The water came from a great waterfall used to cool the people during ceremony.
Just as the water at the base of the waterfall keeps people cool and rises to the sky as mist, the water in the initiates’ bowls keeps them cool and symbolically transforms into clouds that bring the wet rains of the monsoon season. These ceremonies occur in late December when the weather is hot and these stars are high in the evening sky, signalling the start of the monsoon.
Zeta Phoenicis comprises two blue stars orbiting each other, 300 light years away. From our perspective, these two stars eclipse each other, changing in brightness from magnitude 3.9 to 4.4 every 1.7 days.
International Astronomical Union, CC BY
Ginan (Epsilon Crucis)
Ginan is the fifth-brightest star in the Southern Cross. It represents a red dilly-bag filled with special songs of knowledge.
Ginan was found by Mulugurnden (the crayfish), who brought the red flying foxes from the underworld to the sky. The bats flew up the track of the Milky Way and traded the spiritual song to Guyaru, the Night Owl (the star Sirius). The bats fly through the constellation Scorpius on their way to the Southern Cross, trading songs as they go.
The song informs the people about initiation, which is managed by the stars in Scorpius and related to Larawag (who ensures the appropriate personnel are present for the final stages of the ceremony).
The brownish-red colour of the dilly bag is represented by the colour of Epsilon Crucis, which is an orange giant that lies 228 light years away.
International Astronomical Union, CC BY
Boorong star name
Unurgunite (Sigma Canis Majoris)
The Boorong people of the Wergaia language group near Lake Tyrell in northwestern Victoria pride themselves on their detailed astronomical knowledge. In the 1840s, they imparted more than 40 star and planet names and their associated stories to the Englishman William Stanbridge, which he published in 1857.
In Boorong astronomy, Unurgunite is an ancestral figure with two wives. The Moon is called Mityan, the quoll. Mityan fell in love with one of the wives of Unurgunite and tried to lure her away.
Unurgunite discovered Mityan’s trickery and attacked him, leading to a great fight in which Mityan was defeated. The Moon has been wandering the heavens ever since, the scars of the battle still visible on his face.
Wikimedia/Michael J Fromholtz, CC BY-SA
Unurgunite can be seen as the star Sigma Canis Majoris (the Great Dog), with the two brighter stars on either side representing his wives.
One of the wives (Delta Canis Majoris) lies further away from Unurgunite and is closer to the Moon than the other wife (Epsilon Canis Majoris). This is the wife Mityan tried to lure away.
On rare occasions, the Moon passes directly over the wife of his desires, symbolising his attempts to draw her away. He also passes over Unurgunite, representing their battle in the sky. But Mityan, and Moon, never passes over the other wife (with the Arabic name Adhara).
Delta Canis Majoris is an orange-red supergiant that lies 1,120 light years away.
International Astronomical Union, CC BY
Duane W. Hamacher, Senior Research Fellow, Monash University
This article was originally published on The Conversation. Read the original article.
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