In the show this time, we talk to Prof. Sterl Phinney about pulsars and gravitational waves, Mat rounds up the latest news, Ian Morison and Haritina Mogusanu take a look at what's happening in the July night sky and Fiona, Minnie and Alex consider the impact of the EU referendum on UK science.
We apolgise for the sound quality in this episode - we were away from our nice comfortable studio for most of this recording and so sounds levels may vary throughout!
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Second confirmed gravitational wave detection
The LIGO team has confirmed another gravitational wave detection. GW151226 was observed on the Boxing Day, the 26th December 2015. Located at the distance of approximately 1.4 billion light years, it is the second such event ever confirmed, alongside GW150924 announced in February and possible, but not confirmed event LVT151012, detected in October last year. The recorded signal was much weaker than in the case of GW150914 making it more difficult to detect. The signal was also more spread out in time and lasted 1 second, as compared with only 0.2 seconds for the previous event. Even though hidden in the data and initially indistinguishable from the noise, the team relied on sophisticated computer algorithms to extract the meaningful data. After a possible candidate was identified, a matched filtering technique was used to obtain a rough estimate of the properties of the system. The derived masses of the black holes just before the collision were 14.2 and 7.5 solar masses, which is considerably less than 36 and 29 masses of Sun that produced the previous event GW150914, this first gravitational wave ever detected. The LIGO team is confident that the less massive object is indeed a black hole, with a 99% probability of its mass begin more than 4.5 solar masses, the highest theoretical mass for a neutron start. The black hole that was created after the collision has an estimated mass of 20.8 solar masses, meaning that the equivalent of the entire mass of the Sun has radiated away in the form of gravitational waves. Additional analysis showed that the more massive pre-collision and the final back holes were both spinning, with the black hole that was formed after the collision, rotating rather rapidly, with its spin at 70% of its maximum value. As was the case for GW150914, the exact position of the new event on the sky is not well know and cannot be localised better than to within 850 square degrees. The detection of GW151226 proved that LIGO is more than capable of detecting gravitational waves and scientists can soon start using it as a tool for probing the Universe never seen before. It also failed to show any deviation from the General Relativity, which still holds strong after 100 years since its first publication.
New glitching pulsar
Pulsars are known as one of the most precise clocks in the Universe. The radiation observed on Earth arrives with unprecedented regularity. Pulsars also slow down in their rotation, meaning that over longer periods of time, the ticks of pulsar radiation will become out of sync with our predictions, but this effect can be easily accounted for and appropriate corrections can be applied. However, some pulsar experience unpredictable changes in their spin frequency or the rate at which they slow down, known as glitches. The exact reason for these rapid changes is currently unknown, with the best possible explanation involving a sudden transfer of the angular momentum from the inner neutron superfluid to the outer crust. Glitches are usually present in relatively young, non-recycled pulsar such as Vela or Crab and have been observed for many years in such environments. They are however extremely rare for the millisecond pulsars, which are believed to be old objects, recycled thanks to the transfer of matter and angular momentum from their nearby companion. Until last month, only one millisecond pulsar has been known to show glitching behaviour – PSR B1821-24A. New glitch, discovered in PSR J0613-0200 was found in the data recorded as a part of the European Pulsar Timing Array and published in the paper led by James McKee from the Jodrell Bank Centre for Astrophysics. First discovered in 1995, it has been timed to a very high precision over the combined time of almost 14 years. The new analysis combines the data from a number of telescopes: Jodrell Bank Lovell Telescope, French Nancay Radio Telescope, 100-m Effelsberg Radio Telescope in Germany and Dutch Westerbork Synthesis Radio Telescope. A sharp deviation from the timing model was found in the combined dataset, indicating the possible glitch. The possibility of the instrumental errors was ruled out, as no similar deviations were found in the timing data obtained over the same period of time for different pulsars. By fitting the different models to the data, astronomers were able to derive the parameters of the glitch. It turned out to be the smallest glitch ever recorded, with the fractional change in frequency of the order of 10-12 and the fractional change in the rate at which the pulsar rotation slows down of the order of 10-4. The previously detected millisecond pulsar glitch had a fractional frequency change more than 3 times larger. The presence of the glitch raised the questions on the reliability of the Pulsar Timing Array, which use millisecond pulsars, to hunt for gravitational waves, and rely on very precise models and measurements of the pulsar radiation arrival times and PSR J0613-0200 is one of the objects used for this purpose. It was shown, that the glitch was small enough not to influence the reliability of the timing data and the glitch could be easily accounted for. By calculating the expected millisecond pulsar glitch rates, the team estimated a 50% probability of a glitch being detected in the next 10 years in the set of pulsars monitored as a part of the International Pulsar Timing Array. Considering how small the glitch was, scientists are confident that any other event, very likely larger, will not be missed.
Pluto might have geological activityThere is no end to new discoveries coming from the New Horizons mission. The probe provided scientists around the globe with a wealth of information, when it collected the data during its Pluto flyby earlier this year. It was the first time, when we were able to see the surface of this dwarf planet in high resolution, revealing features no one was expecting to find on this cold and distant world. One of the most surprising discoveries was the indication of the relatively recent geological activity. With Pluto being only around 20% the diameter of Earth and just above 0.2% of its mass, it is very unlikely that the dwarf planet was able to sustain the internal heating mechanism to an extent that that allows to any significant changes to occur on the surface. One of the recent studies attempt to solve this mystery. Published at the beginning of June in Nature, it focused on the Sputnik Planum, part of the famous ‘Pluto’s Heart’. With the area of around 900,000 square kilometres, it is one of the biggest and most prominent areas on the Pluto, covering 5% of its total surface. Surprisingly, no impact craters have been found in high-resolution photographs covering the whole area, suggesting that the surface is young, and was formed no longer than 10 million years ago. This means that it must have been a geologically active place, with the surface renewed and all the possible impact crates smoothed out at the timescales of less than ten million years. To find the cause of these surface changes, scientists focused on the unusual cell-like features, irregular polygons, tens of kilometres across, which cover the entire Sputnik Planum. These bulge-like structures rise above the surface of the plain in their centres, and their edges sink in. With the information from the spectroscopic mapping performed by the New Horizons, the abundance of molecular nitrogen, methane and carbon monoxide ice was found, with the nitrogen being the dominant component. Water ice has also been found on the polygons boarders, and is believed to be trapped in the large blocks that float in the sea of nitrogen ice, as the water ice has lower density that the solid nitrogen. It is therefore possible that Pluto is a home to a more exotic version of familiar icebergs. With the nitrogen ice layer few kilometres thick, it is very likely that the convection occurs in that region and the individual polygons are large convection cells. The convection needs a source of power, and it is possible that a small amount of heat is still released from the radioactive decay in the centre of the planet, fuelling the whole process. The amount of the heat released is very small, but the convection would still be possible. Numerical simulations showed that the extent of the polygons could be explained by the convection of the nitrogen ice, several kilometres in thickness, when favourable conditions are met and the surface renewal time of around 500,000 year, much shorter than the required 10 million years. Even though the current state of the Sputnik Planum can be explain, it is still unknown how it came to the existence. The size of the basin, its depth, and the presence of mountains on its edges, suggest it is an impact crater. The reason why such a large amount if nitrogen accumulated in there still remains a mystery, but hopefully with more data mage available every day, we will soon solve it as well.
Interview with Prof. Sterl Phinney
Sterl Phinney is a professor of theoretical astrophysics at the California Institute of Technology. Sterl has a very diverse range of research interests from black holes to condensed matter to star formation to the interstellar medium but he's here to talk to us about transitioning millisecond pulars. These are pulsars which have a still-burning companion star that switch between being radio pulsars and low mass X-ray binaries. He also tells us about the impact of the recent revolution in astronomy - the detection of gravitational waves from coalescing supermassive black holes.
Odds and Ends
In the show today, instead of our usual odds and ends, we discuss the results UK's recent referendum on leaving the European Union, with a particular focus on its ramifications for science and research. While it is too early to form conclusions about how the world of astronomy will be affected by this change, we look at how the EU has been involved in UK science up until now, and, looking forward, ponder the effects that Brexit will have on our increasingly international field.Further information can be found in the statements issued by the RAS and the Royal Society. The Royal Society also provides a useful summary of the EU's role in UK science here.
The Night Sky
Ian Morison tells us what we can see in the northern hemisphere night sky during July 2016.
Highlights of the month
July - Still worth observing Saturn
Saturn reached opposition on the 3rd of June, so is now low (at an elevation of ~ 20 degrees) in the west-southwest as darkness falls lying just over 6 degrees above the orange-red star Antares in Scorpius. Held steady, binoculars should enable you to see Saturn's brightest moon, Titan, at magnitude 8.2. A small telescope will show the rings with magnifications of x25 or more and one of 6-8 inches aperture with a magnification of ~x200 coupled with a night of good "seeing" (when the atmosphere is calm) will show Saturn and its beautiful ring system in its full glory.
As Saturn rotates quickly with a day of just 10 and a half hours, its equator bulges slightly and so it appears a little "squashed". Like Jupiter, it does show belts but their colours are muted in comparison.
July - Find the globular cluster in Hercules and spot the "Double-double" in Lyra
There are two very nice objects to spot with binoculars high in the south-western sky well after dark this month. Two thirds of the way up the right hand side of the 4 stars that make up the "keystone" in the constellation Hercules is M13, the best globular cluster visible in the northern sky.
Just to the left of the bright star Vega in Lyra is the multiple star system Epsilon Lyrae often called the double-double. With binoculars a binary star is seen but, when observed with a telescope, each of these two stars is revealed to be a double star - hence the name!
Early July around midnight: look north to spot Noctilucent clouds.
Noctilucent clouds, also known as polar mesospheric clouds, are most commonly seen in the deep twilight towards the north from our latitude. They are the highest clouds in the atmosphere at heights of around 80 km or 50 miles. Normally too faint to be seen, they are visible when illuminated by sunlight from below the northern horizon whilst the lower parts of the atmosphere are in shadow. They are not fully understood and are increasing in frequency, brightness and extent; some think that this might be due to climate change! So on a clear dark night as light is draining from the north western sky long after sunset take a look towards the north and you might just spot them!
July 1st, 1 hour after sunset: Saturn and Mars make a triangle with Antares
Around one hour after sunset on July 1st, given a clear sky and low southern horizon, you should be able to spot Saturn, above, and Mars, over to the right, or Antares in Scorpius.
July 8th, 1 hour after sunset: A Waning Crescent Moon near Jupiter
Around one hour after sunset on July 8th, given a clear sky and low western horizon, you should be able to spot Jupiter, above and to the left of a thin crescent Moon.
July 16th after sunset: Venus and Mercury half a degree apart
July 29th before dawn: A thin waning crescent Moon close to Aldebaran and the Hyades Cluster.
July 30th after sunset: Mercury very close to Regulus in Leo.
July 13th and 26th: Two Great Lunar Craters
Two great Lunar Craters: Tycho and Copernicus
These are great nights to observe two of the greatest craters on the Moon, Tycho and Copernicus, as the terminator is nearby. Tycho is towards the bottom of Moon in a densely cratered area called the Southern Lunar Highlands. It is a relatively young crater which is about 108 million years old. It is interesting in that it is thought to have been formed by the impact of one of the remnents of an asteroid that gave rise to the asteroid Baptistina. Another asteroid originating from the same breakup may well have caused the Chicxulub crater 65 million years ago. It has a diameter of 85 km and is nearly 5 km deep. At full Moon - seen in the image to the right - the rays of material that were ejected when it was formed can be see arcing across the surface. Copernicus is about 800 million years old and lies in the eastern Oceanus Procellarum beyond the end of the Apennine Mountains. It is 93 km wide and nearly 4 km deep and is a clasic "terraced" crater. Both can be seen with binoculars.
Observe the International Space Station
Use the link below to find when the space station will be visible in the next few days. In general, the space station can be seen either in the hour or so before dawn or the hour or so after sunset - this is because it is dark and yet the Sun is not too far below the horizon so that it can light up the space station. As the orbit only just gets up the the latitude of the UK it will usually be seen to the south, and is only visible for a minute or so at each sighting. Note that as it is in low-earth orbit the sighting details vary quite considerably across the UK. The NASA website linked to below gives details for several cities in the UK. (Across the world too for foreign visitors to this web page.)
Note: I observed the ISS three times recently and was amazed as to how bright it has become.
Find details of sighting possibilities from your location from: Location Index
See where the space station is now: Current Position
Seen low in the western sky after sunset, Jupiter is shining at magnitude -1.9 at the start of the month and has an angular diameter of 34.3 arc seconds. By month's end, these have reduced slightly to -1.7 magnitudes and 32.1 arc seconds. One hour after sunset it will be about 30 degrees above the horizon. Jupiter passes half a degree below the 4th magnitude star, Sigma Leonis on July 12th and continues to move eastwards, moving towards the Leo-Virgo boarder. Due to the low elevation, the atmosphere will limit our view somewhat but up to four of the Gallilean moons will be visible as well as the dark equatorial bands. The Great Red Spot will be harder to spot unless the seeing and transparency of the atmosphere are good.
Saturn, having been in opposition on June 3rd, lies some 6 degrees north of Antares (in Scorpius) in southern Ophiuchus. It continues its retrograde motion westwards across the sky throughout July, narrowing its gap between Mars (now moving eastwards) from 19 degrees to 11 degrees as the month progresses. At the same time the brightness drops a little, from magnitude +0.1 to magnitude +0.3 whilst its apparent diameter falls from 18.2 to 17.6 arc seconds. Though only at an elevation of 20 degrees when due south at around 11 pm as July begins (and 9pm at month's end) the beautiful ring system, now at an inclination of 26 degrees is still worth observing as is Saturn's brightest Moon, Titan.
Mercury passes behind the Sun (Superior Conjunction) on July 6th, but may become visible in binoculars about mid month when it sets about 45 minutes after sunset as it lies just half a degree above Venus. During July's final week it will be seen to the upper left of Venus and moves closer to Regulus, in Leo, until the two close to just 22 arc minutes on the evening of July 30th.
Venus, having passed behind the Sun on June 6th becomes visible in mid month low in the west-northwest shining at magnitude -3.9 in Gemini. It passes to the lower left of Pollux on the 13th andpasse through the Beehive Cluster, M44,in Cancer on the 20th, ending the month 5 degrees to the west of Regulus in Leo.
Haritina Mogosanu from the Carter Observatory in New Zealand tells us about the southern hemisphere night sky during July 2016.
My name is Haritina Mogosanu and tonight I am your starryteller from the Southern Hemisphere. In this jodcast episode I will talk about flying, since it is something I have always loved the most, besides the stars. This podcast is for Stephen who also likes flying.
I always look up for planes and stars altogether, and I've always been happiest in the air. And many times I forget that whilst I am thinking that I am sitting still here on Earth yearning to be there in the skies, our planet is moving at an incredible speed.
Moving but in relation to what? This is a good question. Well, to start with a point of reference, Earth is hurtling at 30 km per second around the Sun. We could measure these orbits in birthdays. One rotation, one birthday. So it takes Earth a year to go around the Sun once. The Sun also revolves around the Milky Way at 250 km per second. So that means that by the time we blink twice we already covered the distance from Wellington to Rotorua. Since our galaxy is larger than that, it takes roughly 230,000,000 Earth years to go around the Milky Way once... So one galactic year ago the trilobites were swimming in Earth's oceans...
But that's not the fastest speed out there... According to Scientific American, the galaxies in our neighborhood are also rushing at about 1,000 kilometers per second towards a structure called the Great Attractor, a region of space roughly 150 million light-years (one light year is about nine and a half trillion kilometers) away from us.
In terms of starry wings, there are many creatures out there among the asterisms imagined by humans. I will start with my absolute favourite object, which was discovered only a quarter of a century ago, the Milky Way Kiwi.
July is the time when the centre of our galaxy, the Milky Way, is climbing all the way to the Zenith and from there, if there is a truly dark night, you can see the Milky Way Kiwi. Now you do need a very dark sky for that, and you need to know what you are looking for. Best you can see the Milky Way Kiwi in long exposed pictures of the night sky but I have seen it with the naked eye from Lake Tekapo Earth and Sky. Before I came to New Zealand, I had not known it existed, I've always thought that the dark patch I was looking at, if I was lucky enough to see it, was a dark horse. Suspended in the fabric of space, the center of our galaxy only rose about 30 degrees above the horizon, where I am from, near the 45 degrees North parallel. Besides, I did not even know what a kiwi bird was truly, let alone a celestial kiwi bird.
Another favourite of mine is Cygnus the Swan. It's my home zenith constellation back in the Northern Hemisphere where it is also known as the Northern Cross. Cygnus is juxtaposed on the Milky Way. Very low on the Northern horizon here, it's main star Deneb is barely grazing the earth looking as if it's a slow moving flame that brazes the land with the galaxy. It rises one hour after midnight, as seen from Wellington New Zealand. A tad higher than Deneb, my favourite star, double star, - well actually triple, Albireo, is resolved in telescopes as one aqua blue and one orange star. That's a sight worth seeing at least every night when Albireo is in the sky. Cygnus rises around midnight.
Aquila, the Eagle is another beautiful bird that flies in the Northern part of the sky, is low on the horizon rising, just after 8pm. Right at its tail, there is NGC 6751, a planetary nebula that looks just like an iris. Altair is the brightest star in Aquila and it's on the Milky Way.
Opposite Deneb and Altair, on the south western part of the evening sky, Sirius is setting whilst Canopus is descending from heavens. In between Sirius, and Canopus, is the constellation Columba. The cat and the dog are chasing the Dove, which is what Columba means. For deep sky observing, near Phaet, the alpha star, brightest star from Columba, there is a beautiful spiral galaxy, NGC1808.
Delicate and rich in optical double stars that we can seen with the naked eye, Grus the Crane is another bird-constellation laying now on the South Eastern Horizon. From Capricornus, that looks like a golf flag from here, hop two more blocks, passing another favourite star of mine, Fomalhaut, the loneliest star, in Piscis Austrinus and next stop south is Grus. I remember seeing Grus in a picture for the first time whilst Comet McNaught was here in New Zealand in 2006 and getting very excited about being able to recognise it by the multiple double stars in it.
Since we are at the southern side of the sky, to be fair, as much as I don't like them, Musca, the Fly also qualifies for a flying creature. Near the southern cross, Musca looks like a patrulater. A small one, peering inside the coalsack. At the end of its abdomen, NGC4833 is a rather nice globular cluster. Near Musca, Apus, the bird of paradise's name literally means "no feet" in Greek, as it was once wrongly believed that the birds of paradise lack feet. Apus is pointing straight at Pavo the peacock, that is flaunting with feathers all over the south celestial circle. Next to Pavo, is Toucana, near the Small Magellanic Cloud (NGC 292). Some spectacular deep sky objects near it are the famous NGC104 also known as 47 Tucanae, but also NGC362, another globular cluster, NGC346 Open Cluster, NGC 290, open cluster and NGC265 Open Cluster. Toucana is neighbouring Grus on one side and the Phoenix, on the other side. Since Herodotus, the Greek historian, the bird of Phoenix was associated with the Sun, a phoenix obtains new life by arising from the ashes of its predecessor and it can live for 1400 years at the time. Inside the constellation, NGC55 is an irregular galaxy and NGC 300 is a spiral galaxy. The main star in Phoenix, Ankaa is almost halfway through Achernar and Fomalhaut.
But a dark patch that looks just like a kiwibird, that is something that perhaps not too many people saw coming. Not too many people from New Zealand, I mean, because as i have discovered, being shown a kiwi bird, very few foreigners (I'm not counting the tourists here tho) can guess what that is.
So the Milky Way Kiwi does carry all the weight of our stars. Not surprising, given what its equivalent on Earth, the kiwibird did. There is a beautiful Maori legend telling how the kiwibird lost its wings.
Thank you for listening to the July 2016 podcast, until next time Kia Ora and Kia Kaha from Space Place at Carter Observatory in the Southern Hemisphere.
|Interview:||Prof. Sterl Phinney with Benjamin Shaw and Charlie Walker|
|Night sky:||Ian Morison and Haritina Mogusanu|
|Presenters:||Fiona Healy, Alex Clarke and Minnie Mao|
|Editors:||Benjamin Shaw, Monique Henson, Haritina Mogusanu and Charlie Walker|
|Night Sky Music:||Rhian Sheehan|
|Website:||Benjamin Shaw, Saarah Nakhuda and Stuart Lowe|
|Cover art:||A binary millisecond pulsar. CREDIT: European Space Agency|