In the show this time, we talk to Robert Minchin about how to do astronomy after a hurricane, Emma Alexander rounds up the latest news, and we find out what we can see in the February night sky from Ian Morison and Claire Bretherton.
In the news this month: the extreme magneto-ionic environment associated with the source of the repeating Fast Radio Burst, exposed subsurface ice sheets in the Martian mid-latitudes, and the first definitive interstellar detection of benzonitrile.
First up in the news this month: FRBs. First discovered in 2007, Fast Radio Bursts (or FRBs) are bright radio pulses that last only a few milliseconds. The bursts are highly dispersed in frequency, implying that they are extragalactic in origin, but the exact circumstances of their origins remain uncertain. FRB 121102, possibly the most well known FRB as it is the only one observed so far to repeat, has been the subject of a recent study published last month in Nature. Observations of this repeating FRB taken with the Arecibo and Green Bank radio telescopes were found to show almost 100 per cent linearly polarised emission. The study looked at Faraday rotation of the polarised emission, which is the phenomena describing the rotation of a polarised wave due to the presence of a magnetic field. Faraday rotation measures quantify this rotation of polarisation angle, and are indicative of the strength of magnetic fields and the electron density along the path of the emission. The rotation measures of the repeating FRB bursts were found to be of the order of 10^5 radians per meters squared. To put this into context, such large rotation measures have only previously been seen in the vicinities of massive black holes, ones with masses greater than 10,000 times that of the Sun, and indicate the presence of extremely strong magnetic fields.
The observations by the two telescopes were taken of bursts 6 months apart, allowing for variability in the source to be examined. The dispersion measure, which quantifies the differing arrival times of the signal for different observation frequencies, was found to not change. This means that the electron density along the line of sight to the burst has not changed. However, there was around a 10 per cent difference in the rotation measures, and because changing electron density was able to be ruled out, this means that the magnetic field had changed. So not only is the environment around this FRB likely to be highly magnetised, it also is likely to be constantly evolving and changing. The fact that this source is also responsible for the shortest FRB bust seen so far implies that it's source is small, astronomically speaking, at around 10km. This would be consistent with it being the size of a neutron star.
The study concludes that the observations are consistent with the extreme magneto-ionic environment of a low-luminosity, accreting massive black hole, with the bursts originating from a neutron star within that environment. It could also be due to a young magnetar in a supernova remnant or pulsar wind nebula. With this discovery, we are hopefully one step closer to understanding these mysterious transient radio phenomena.
Next up, we look a bit closer to home - within our own solar system in fact. A study published in the journal Science details the observations by the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter (MRO). Researchers found thick, exposed deposits of ice beneath Mars' surface in faces of eroding slopes at eight sites. These icy deposits of relatively pure water ice can give us insights into the history of the Martian climate, in addition to being more accessible to potential future exploratory missions to Mars. It has been known for some time that shallow ground ice existed on the surface of Mars, and that there are larger icy deposits at its poles. But these newly found thick underground sheets are different to what has been seen before, and offer a new insight into our planetary neighbour.
And finally, also appearing in the journal Science, the detection of benzonitrile in the interstellar medium. For decades, astronomers have been puzzling over the existence of faintly glowing infrared light that is observed throughout the Universe. It was thought that this glow was due to a class of molecules called polycyclic aromatic hydrocarbons, where here aromatic refers to the molecule's ring-like shape. However, until now, there was no evidence that these molecules existed in space. The study used data from the Green Bank telescope to detect tell-tale signs of benzonitrile, a chemical precursor to polycyclic aromatic hydrocarbons. benzonitrile's unique structure gives it a distinct radio signature, which the astronomer found in observations the Taurus Molecular Cloud, which is a star-forming nebula located about 430 light-years from Earth. This cold molecular cloud wouldn't be the first place you'd think you look for benzonitrile however, as it is thought to form around hot, evolved stars. Its abundance was also four times what would be expected from chemical models, so there is still much more to learn about these mysterious molecules.
Interview with Robert Minchin
Tom Scragg sits down with Dr. Robert Minchin from the Arecibo Observatory, discussing the search for neutral hydrogen outside of galaxies in the Virgo cluster and the impact of Hurricane Maria (September 2017) on Arecibo. Robert updates us on the telescope's status as of December 2017, with repairs carried out and science being conducted in the meantime.
The Night Sky
Ian Morison tells us what we can see in the Northern Hemisphere night sky during February 2018.
In her final broadcast for the Jodcast, Claire Bretherton from the Carter Observatory in New Zealand tells us what we can see in the Southern Hemisphere night sky during February 2018.
Kia ora and welcome to the February Jodcast from Space Place at Carter Observatory in Wellington, New Zealand.
Below Canis Minor sits another pair of stars, Castor and Pollux, marking the heads of Gemini, the twins. Pollux, the higher and brighter of the two stars, is the 17th brightest star in our night sky. It is about 35 light years away from us, whilst Castor is in fact a sextuple star system located 52 light years from Earth.
Nearby to Eta Geminorum, at the foot of the twin of Castor, is the open star cluster M35, covering an area almost the size of the full moon. Under good conditions it can be seen with the unaided eye as a hazy star, but binoculars or a wide-field telescope will reveal more detail and are the best ways to view this lovely cluster.
Next to Gemini is the faint zodiac constellation of Cancer, the crab. At the centre of Cancer is a lovely open cluster of stars known as M44, Praesepe (the Manger) or the Beehive. At magnitude 3.7, the cluster is visible to the naked eye as a hazy nebula, and has been know since ancient times. It was one of the first objects Galileo studied when he turned his telescope to the skies in 1609.
Galileo was able to pick out around 40 stars, but today we know that Praesepe contains over 1000 individual members, with a combined mass of between 500 and 600 times that of the Sun. As one of the closest open star clusters to our Solar System, M44 is a great target for binoculars or small telescopes, which will easily reveal a number of individual stars within it.
Higher, and to the east of Canis Major is Puppis, representing the Poop deck of the great ship Argo, which we explored last month. Inside Puppis are two lesser known Messier Objects, M46 and M47.
Messier 46 (also known as NGC 2437) is a rich open cluster at a distance of about 5,500 light-years away. M46 is estimated to contain around 500 stars, of which around 150 of magnitude 10-13. Estimated to be only 300 million years old, this is a young cluster, and a lovely sight in binoculars or a small telescope. Astronomer John Herschel described it in his General Catalogue of Nebulae and Clusters of Stars as “Remarkable, cluster, very bright, very rich, very large, involving a planetary nebula". This planetary nebula, located near the cluster's northern edge, is NGC 2438.
A planetary nebula is formed when a low or intermediate mass star comes to the end of its life, ejecting its outer layers into space as a glowing shell of ionized gas.
Located around 1 degree west is another open cluster, M47. The two fit easily within one binocular field of view, and are often referred to as sisters.
Messier 47 or NGC 2422 has actually been discovered several times. The first was some time before 1654 by Giovanni Batista Hodierna and then independently by Charles Messier on February 19, 1771. William Herschel also independently rediscovered it on February 4, 1785, and it was included as GC 1594 in John Herschel's General Catalogue of Nebulae and Clusters of Stars (the precursor to Dreyer's New General Catalogue) in 1864.
Due to a sign error by Messier, the cluster was considered a 'lost Messier Object' for many years, as no cluster could be found at the position of Messiers original coordinates. It wasn't until 1959 that Canadian astronomer T. F. Morris identified that the cluster was in fact NGC2422, and realized Messier's mistake.
M47 lies at a distance of around 1,600 light-years from Earth with an estimated age of about 78 million years. It is described as a course, bright cluster containing around 50 stars, scattered over an area around the same size as the full moon in the sky. It is bright enough to be glimpsed with the naked eye under good observing conditions, but best viewed with binoculars or a small telescope.
There are a couple of other excellent binocular targets in Puppis, including open cluster NGC2477 - a wonderful, rich cluster of over 300 stars, described by American Astronomer Robert Burnham as "probably the finest of the galactic clusters in Puppis" along with its neighbor NGC 2451, both located close to the second magnitude star Zeta Puppis.
Also known as Naos, this blue supergiant is one of the hottest, most luminous stars visible to the naked eye. It has a bolometric (total) luminosity of at least 500,000 times that of the Sun, but with most of its radiation emitted in the ultraviolet it is visually around 10,000 times brighter. It is also one of the closest stars of its kind to our Sun, at a distance of around 1,080 ly.
Odds and Ends
Is there life on Mars? A team from McGill University in Canada have developed a low-weight and low-cost instrument platform which can detect and analyse microorganisms in extreme environments, akin to those found on Mars.
Ordinarily, on Earth an experiment to test for life in extreme environments requires a sample to be returned to a lab, which is time consuming and increases chances of sample contamination. These issues are exacerbated when you consider a sample returned from another planet (or minor body). Doing such research in-situ on mars has not been done since the 70's, as instrumentation to do so was costly and took up a lot of valuable space on missions since.
Instead, this team at McGill have created a suite of miniature modular instruments called a life detection platform, which can culture mircoorganisms from soil samples, assess any activity in the cultured sample and also sequence the DNA and RNA. The team lead have published their results of tests made in the Candian high Arctic (79*26'N) (900km south from the North Pole) in a paper led by Dr Jacqueline Goordial in the journal 'Frontiers of Microbiology'. They report the successful sequencing culturing, activity detection and DNA sequencing of extremophile microbes in-situ with their low cost, low power system. The Arctic here is a close analogue of the Martian permafrost.
Given this proof of concept the team have high hopes for their system and its uses on Mars, Europa and Enceladus.
If aliens exist, where are they? This question is known as the Fermi paradox and we have a look at a possible answer to it. Perhaps the stereotype of technologically advanced alien civilisations is incorrect and most aliens are in the equivalent of the medieval ages. Perhaps we are one of the most advanced species out there and this is why we have not seen anyone else. We explore this idea and discuss some other explanations of where all the aliens might be (though they probably aren't where the FRBs are...)
Fast radio bursts (FRBs) are really bright, short duration bursts of radio light, usually lasting only a few milliseconds. We know they're really bright and really far away, but we don't yet know what makes them. We are, however, pretty sure that they aren't aliens. Maybe one day we'll catch an alien signal, but FRBs aren't it. For FRB updates on Twitter I'd recommend giving Emily Petroff a follow at @ebpetroff. Information about the latest big paper on FRBs (about the polarisation of the repeater) can be found here and the paper itself can be found on the Nature website (if you have access) or here.
|Interview:||Robert Minchin and Tom Scragg|
|Night sky:||Ian Morison and Claire Bretherton|
|Presenters:||Adam Avison, Laura Driessen and Josh Hayes|
|Editors:||Naomi Asabre Frimpong, Joseph Kwofie, Nialh McCallum and Tom Scragg|
|Segment Voice:||Tess Jaffe|
|Website:||Jake Morgan and Stuart Lowe|
|Cover art:||The dish of the Arecibo Observatory - down, but not out! CREDIT: Xavier Garcia, Bloomberg/Getty Images|