In the show this time, we talk to Dr Federico Urban about bigravity, graviton and dark matter, Beth Jones rounds up the latest news, and we find out what we can see in the October night sky from Ian Morison and Claire Bretherton.
The News
LIGO-VIRGO announcement of a fourth gravitational wave
On the 27th of September came the announcement of a fourth gravitational wave detection from only two weeks after the VIRGO detector in Italy joined forces with the LIGO detectors. Not only is this the first detection of a gravitational wave with VIRGO, but the first using three different instruments, as the previous three events were found using the two LIGO sites. The signal was picked up at nearly the same time on all detectors, recorded at 10:30 UTC on the 14th of August and named GW170814.This detection is the same type of event as the previous three- a merger of two black holes. Again, the signal gives evidence for intermediate black holes, which are not thought to be able to form through the collapse of massive stars. 1.8billion light years away, two black holes of 25 and 31 times the mass of the sun merged to form a single black hole of 53 solar masses. The missing 3 solar masses was converted to energy, and carried away as gravitational waves, luckily for us.
The addition of the VIRGO detector to the two, LIGO detectors which reside in the US is more important than simply confirming the existence of a gravitational wave. Adding a third detector to the team improves efforts to locate the source of the signal in the sky, shrinking the volume of the universe that is likely to contain it by a factor of 20. GW170814 is currently pinned down to 60 square degrees on the sky, a factor of 10 times smaller than any previous detection. Theres Cassini spacecraft took a final dive towards the planet before being torn apart in the clouds on the 15th September. Launched on the 15th October 1997, the spacecraft carried out pioneering work on uncovering the mysteries of the ringed planet and its many moons. In 2005, Cassini dropped ESAs moon Titan, revealing unsettlingly Earth-like landscapes. In the sky above, Cassini discovered complex organic molecules, the building blocks of life on Earth, in the moon thats a moon! Cassini took stunning images of them all, finding 6 new moons to give Saturn a running total of 62.
Towards Saturn itself, Cassini pinned down the properties of the upper atmosphere, finding it to be mostly hydrogen and 7% helium. The disruptive effects of the moons and smaller moonlets on Saturns rings and atmosphere over the course of 5 months. Even during its final descent, Cassini refused to stop sending back data as it plunged into Saturns temperature, magnetic field and atmospheric conditions.
Although this seems like a cruel fate for poor Cassini, it was the only possible use for the last portion of its fuel reserves. Leaving the satellite to orbit aimlessly could one day result in a collision with one of the moons, dropping off any surviving Earth bacteria with it. With prime candidates for life such as Enceladus and Titan, contamination was too great a risk. In the words of ESAwhile it is certainly sad when a mission ends, it is also a time to celebrate this pioneering journey, which leaves a rich scientific and engineering legacy to pave the way for future missions".
Arecibo Observatory suffers from terrestrial interference
Until the recent construction of FAST in China, Arecibo Observatory in Puerto Rico boasted the largest single aperture radio telescope at a whopping 305m diameter. Made of over 38,000 aluminium panels supported by a mesh of steel cables, the telescope has been active in the Search for Extraterrestrial Intelligence (SETI) and sending out messages visible to other civilizations. In day-to-day operations, the telescope is also used study planets, pulsars, asteroids, galaxies and even dark matter. The sinkholes in Puerto Rico have provided a perfect place to nestle a giant radio telescope.
Unfortunately, Puerto Rico fell in the destructive path of Hurricane Maria last week with the whole island losing electricity in the wake. Much of the population still remain without power or communications as gushing rivers, a dam failure and huge amounts of building damage plague the island. After initial radio silence from the observatory, the staff are now remaining optimistic about the to the telescope. Officials reported that a 29metre line-feed antenna (once used to detect mountains on Venus) fell from a platform about 100m above the dish, puncturing it in several places. A smaller 12m dish was also lost to the storm, knocking about 20 surface tiles loose from the main dish on the way down.
Perhaps most importantly, all staff at the site were reported safe after the storm. The telescope remains un-operational for now ahead of a full assessment of the damage and the repairs required.
Interview with Dr Federico Urban
Dr Federico Urban from KFBI in Tallinn talks about massive bigravity, a recent(ish) theory of gravity that has interesting implications for dark matter. We dip into the origins of bigravity, before touching upon how it could be proved (or disproved).
The Night Sky
Northern Hemisphere
Ian Morison tells us what we can see in the northern hemisphere night sky during October 2017.
The Planets
- Jupiter
Jupiter might just be visible for the first few days of October very low above the west-southwestern horizon after sunset. It passes behind the Sun on October 26th to become visible again in the pre-dawn sky in mid November.
- Saturn
Saturn can be seen low in the southwest during twilight this month dropping down towards the horizon a little more each week. Shining at magnitude +0.5, it sets around 3 hours after the Sun on the 1st but nearer 2 hours by month end. It is moving slowly eastwards in Ophiuchus moving closer to the boundary of Sagittarius which it will reach on the 18th of November. This month, Saturn's rings reach their maximum tilt to the line of sight of 27 degrees and it is a real pity that Saturn is so low in the sky. Sadly, this will not improve for quite a few years as Saturn moves slowly through the lowest part of the ecliptic.
- Mercury
Mercury passes between us and the Sun (Superior conjunction) on October 8th so will not be visible this month.
- Mars
Mars has now become a morning object at the start of its new apparition. Initially lying in Leo, it moves into Virgo on the 12th of the month and is still not easily seen in the pre-dawn sky. During the month, Mars has a magnitude of 1.8 and an angular size of just 3.7 (increasing to 3.9) arc seconds so no details will be seen on its salmon-pink surface. As the month progresses Mars rises higher in the sky before dawn and, as described in the highlights, flirts with Venus at the beginning of the month.
- Venus
Venus, now moving back towards the Sun, is visible in the east before dawn this month, rising around 2 hours before sunrise at the start of the month and close to Mars. Its magnitude remains at -3.9 during the month as its angular diameter shrinks from 11.2 to 10.6 arc seconds. However, at the same time, its illuminated phase increases from 91% to 96% - which explains why its magnitude does not change. By month's end, Venus rises just an hour and a half before the Sun and binoculars might be needed to spot it low above the eastern horizon. But please do not use them after the Sun has risen.
HIGHLIGHTS
- October - a good month to observe Neptune and Uranus with a small telescope.
Neptune came into opposition - when it is nearest the Earth - on the 2nd of September, so will be well placed to spot this month. Its magnitude is +7.9 so Neptune, with a disk just 3.7 arc seconds across, is easily spotted in binoculars lying in the constellation Aquarius as shown on the charts. It rises to an elevation of ~27 degrees when due south. Given a telescope of 8 inches or greater aperture and a dark transparent night it should even be possible to spot its moon Triton. Uranus reaches opposition (when it is nearest the Earth) on October 19th and so is visible all night. It will be highest in the sky in the south around 1 am BST shining at magnitude 5.7 and with a disk 3.7 arc seconds across. It lies in Pisces, one degree and 18 arc minutes up to the right of Omicron Pisces as shown in the accompanying chart. Its turquoise green colour should be seen in a small telescope and it will be easily spotted in binoculars.
- October 5th - before dawn: Venus and Mars close in the East.
Before dawn on the 5th, Venus and Mars will lie just a quarter of a degree apart in the eastern sky.
- October 1st- 14th - evening: Saturn in the Southwest
After dark in the evenings of the first part of the month we will have our last good views of Saturn this apparition. Its rings are at their widest, inclined at 27 degrees to the line of sight.
- October 9th - late evening: The Moon and the Hyades Cluster
Late evening on the 9th, rising in the East will be the Hyades Cluster along with a waning Moon.
- October 17th - before dawn: Venus and Mars below a thin crescent Moon.
Looking Eastwards before dawn on the 17th, a thin crescent Moon will be seen high above Venus and Mars.
- October 24th - after sunset: Saturn below a thin waxing crescent Moon
After sunset on the 24th, Saturn will be seen lying below a thin waxing crescent Moon.
- October 11th: Mons Piton and Cassini
Best seen just before Third Quarter, Mons Piton is an isolated lunar mountain located in the eastern part of Mare Imbrium, south-east of the crater Plato and west of the crater Cassini. It has a diameter of 25 km and a height of 2.3 km. Its height was determined by the length of the shadow it casts. Cassini is a 57km crater that has been flooded with lava. The crater floor has then been impacted many times and holds within its borders two significant craters, Cassini A, the larger and Cassini B.
Claire Bretherton from the Carter Observatory in New Zealand speaks about the southern hemisphere night sky during October 2017.
Kia ora and welcome to the August Jodcast from Space Place at Carter Observatory in Wellington, New Zealand.
The Planets
- Saturn
Saturn is now our best bet for evening planet viewing, sitting midway up the western sky after dark. A little below and to the left of the planet is Antares or Rehua, marking the heart of Scorpius, which we call te Matau a Maui, the fish hook of Maui here in New Zealand.
- Zodiacal Light
October is a good time to look out for the zodiacal light, a triangular glow visible in the west after sunset in a clear, dark sky, tilting up towards Antares. The zodiacal light is caused by sunlight reflecting off dust along the plane of our solar system. This plane is marked by the ecliptic, the apparent path of the Sun across the sky, which runs through the constellations of the zodiac. At this time of year the ecliptic makes a steep angle with the horizon, making the zodiacal light easier to observe.
- Neptune and Uranus
Whilst not easily seen with the naked eye, Neptune and Uranus are also in our evenings skies, with Neptune in the constellation of Aquarius and Uranus is in neighbouring Pisces. Uranus reaches opposition on the 20th of the month, when it will be directly opposite the Sun in the sky and overhead at around 1am now that we are observing daylight saving. At magnitude 5.7 it is just on the edge of naked eye visibility, but with binoculars should be easy to spot. A small telescope may reveal it as a disk, with a greenish hue.
We're really noticing the lighter mornings and evenings now as the Earth continues its orbit around the Sun and we move closer to our southern hemisphere summer. By the end of October the Sun won't set until around 8pm here in Wellington. As we leave Jupiter behind on its outer orbit it is slowly disappearing from our skies, it still sits low in the west at the beginning of the month, setting as twilight ends, but by mid month will be lost in the sunset.
Constellations
- Magellanic Clouds
Between the southern celestial pole and Achernar, and above Canopus, you may be able to spot two small fuzzy patches of light, easily seen with the naked eye on a dark, moonless night. These are the Large and Small Magellanic Clouds, two small irregular dwarf galaxies that neighbour our own. Whilst these galaxies are much smaller than the Milky Way, they still contain billions of stars. To the top-right of the SMC you may spot a faint fuzzy 'star'. This object is not actually associated with the SMC but is a beautiful globular cluster called 47 Tucanae, or NGC 104 located just a tenth of the distance away on the outskirts of our own galaxy. At around magnitude 4.1 it is the second brightest globular cluster in the sky, after Omega Centauri, and can be easily seen with the naked eye. With a binoculars or a small telescope it is a wonderful sight, revealing a densely packed central core, whilst a larger telescope will start to resolve some of its millions of ancient stars.
- Orion
At the far end of the long winding river of Eridanus is our summer constellation of Orion, the hunter, with bright, blue Rigel the first star to rise after around 11pm mid-month. Below, and following around and hour and a half later is stunning red Betelgeuse, marking the hunter's shoulder or armpit. We'll be exploring this part of the heavens in much more detail over the next few months as it moves into our evening skies, but this month we turn our attention to the constellation in the morning skies, the best time to see the Orionid meteor shower, the radiant of which lies a little below and to the right of Betelgeuse. The Orionids peak on the 21st-22nd of October when the Earth passes through the trail of dust and debris left behind by Comet Halley. The shower can reach rates of 25 meteors per hour, but from the latitude of New Zealand around 10 per hour is more likely with the radiant below the horizon until the early hours of the morning. The best time to look is in the hours before dawn. Try looking around 20 degrees away from the radiant, so the areas from Taurus around through the top of Orion to Canis Major are probably your best bet. Whilst the meteors may be few and far between they also tend to travel quite long distances on the sky and sometimes leave persistent trails of ionized gas behind them that can last for several seconds. With a new moon on the 20th, just before the peak, leaving us with nice dark skies, you should have a good chance of Orionid spotting this year.
Just to the north of Pisces is the constellation of Pegasus, the winged horse, which appears to leap across the northern horizon in our late evening sky. Pegasus is easy to spot by the ''Great Square'' of stars that makes up his body.The brightest star in the constellation is the reddish star Epsilon Pegasi, marking the horse's muzzle. This star is commonly known as Enif, deriving from the Arabic word for nose. Epsilon Pegasi is an orange supergiant, around 12 times the mass of the Sun, and with a radius some 185 times larger.
Nearby, to the bottom left of Enif, (and visible in the same binocular field of view) is the globular cluster M15, one of the oldest and best know star clusters in the sky, with an estimated age of around 12 billion years. The cluster is located around 34,000 light years away and measures 175 light years across. M15 is probably the most densely packed globular cluster in our galaxy, with half of its mass concentrated within 10 light years of the centre. It has been suggested that this massive concentration of stars may be caused by a rare type of supermassive Black Hole in the clusters core.M15 also contains the planetary nebula Pease 1, the first to be found within a globular cluster. At magnitude 15.5, this is a faint object, and a telescope with an aperture of at least 300mm would be needed to observe it.
On the opposite side of the sky, the Southern Cross, or Te Punga sits low in the south south west, its long arm pointing up across the sky to Achernar in the south east. Achernar is at the tip of the constellation of Eridanus, the river, and is also known as Alpha Eridani. It is the brightest star in the constellation, and the 9th brightest in the night sky. It is a hot, blue main sequence star around 7 times the mass and over 3000 times the luminosity of the Sun. The traditional name, Achernar, derives from the Arabic phrase ''Al Ahir al Nahr'' meaning the end of the river, although interestingly this name was once given to Theta Eridani, now known as Acamar, which was the brightest star in the constellation visible from Ancient Greece.Achernar spins on its axis extremely quickly, completing one rotation in just over 2 days. This high rotation speed gives the star a flattened shape, with the diameter of its equator over 50% greater than that of its poles. Infrared observations from the Very Large Telescope in Chile have also identified a smaller companion star, with around twice the mass of the Sun. The two are extremely close, with a separation of just over 12 AU, slightly larger than the distance from the Sun to Saturn, and orbit once every 14-15 years, although the highly distorted shape of the primary makes these numbers hard to determine.
Below Achernar, just above the south south east horizon, our second brightest night time star, Canopus, twinkles colourfully. The two make an almost equilateral triangle with the southern celestial pole, the point in the sky directly above the south pole of the Earth, about which the whole sky appears to rotate. Another easy way to find this is to but one hand an Achernar and a second hand on Gamma Crucis at the top of the Southern Cross and clap them together in the middle.
Wishing you clear skies from the team here at Space Place at Carter Observatory.
Odds and Ends
A study has come out in arxiv looking at the visibility of the solar system planets through transits. This has implications on SETI investigations as it opens up the possibility of focussing our searches on detected habitable planets which would be able to see us. Unfortunately, no such planets have yet been discovered, but the study estimates that there may be as many as 15 such planets around Sun-like and smaller stars.
Tim Peake is the first British ESA astronaut, the second astronaut to bear a British flag patch, the first of course being Helen Sharman. He was launched to the International Space Station, on 15th December 2015 spending 6 months there performing a variety of tasks ranging from scientific experiments, to space walks, even running a marathon! One experiment involved taking some seeds of Rocket up to space (it appears someone had a sense of humour!) which were later brought down to be grown by children at 8600 schools around the UK. It was discovered by growing them alongside seeds that had been left on earth that the impact on growth due to having been in Space for 6 months was minimal, suggesting that vibrations during launch, temperature fluctuations, cosmic rays and microgravity do not prevent seeds from germinating and growing. The Soyuz TMA-19M descent module that Tim Peake made his return to Earth in will now be touring the UK, giving members of the public across the country the chance to see this historic spacecraft. Additionally, Samsung have developed a Virtual Reality experience allowing the public to experience what it is like to be inside a Soyuz descent module as plummets towards Earth at high speed. It certainly sounds like it will be worth a visit, the dates are listed below if you fancy it. Full tour dates are listed below:
- 27 September to 19 November 2017 Locomotion, Shildon (County Durham)
- 17 January to 8 March 2018 Museum of Science + Industry, Manchester
- Mid-May to mid-August 2018 TBC (competition slot)
- Mid-November 2018 to January 2019 National Museums Northern Ireland: Ulster Museum, Belfast
The Apollo 14 mission, launched on January 31st 1971, didns personal kit were 400-500 seeds of various tree types, which were subsequently planted back here on Earth (mostly around the southern and western states of the USA). Since then, many ''half Moon'' trees have been grown from cuttings or seeds from these trees. The trees weren't studied scientifically, but it was noticed that they had no discernible differences with how their non lunar counterparts grew. Sadly, the Moon trees have been in the news recently due to a loss of one of the originals at Kennedy Space Center Visitor Complex, during Hurricane Irma. However, there are still many Moon trees standing (you can find out where here), and probably many still undocumented - if you know where one might be, you can read how to report one here.
Show Credits
News: Beth Jones Interview: Dr Federico Urban and Monique Henson Night sky: Ian Morison and Claire Bretherton Presenters: Emma Alexander, Josh Hayes, Nialh McCallum Editors: Damien Trinh, George Bendo, Tom Hillier, Tom Scragg Segment Voice: Iain McDonald Website: Naomi Asabre Frimpong and Stuart Lowe Producer: Naomi Asabre Frimpong Cover art: CREDIT: NASA Jet Propulsion Laboratory
- Saturn
