In the show this time, we talk to Dr. Teo Munoz Darias about X-ray binaries, Mat rounds up the latest news, and we find out what we can see in the February night sky from Ian Morison and Claire Bretherton.
This month in the news:
On the 26th January, NASA remembered all those who lost their lives to the exciting but extremely dangerous business of space exploration. The annual Day of Remembrance was established in the memory of the fallen crews of Apollo 1 and Space Shuttles Challenger and Columbia. This year was particularly special, as it marked the 50th anniversary of the Apollo 1 tragedy, when an explosive fire claimed the lives of three NASA astronauts: Roger Chaffee, Virgil "Guss" Grissom and Edward White. The first one from the series of missions with the ultimate goal of putting American astronauts on the surface of the Moon. NASA planned to launch the crew on the 21st February 1967 and conducts an around 2 weeks long test flight in the Low Earth Orbit. On 27th January, less than a month before the planned launch, an important "plugs-out" simulation was being carried out, with the capsule mounted on top of the Saturn IB rocket, parked on Pad 34 in Cape Canaveral. The test was meant to determine, whether the spacecraft was capable of running on the internal power only, detached from all the external power sources. The module was filled with pure oxygen at the pressure higher than the atmospheric pressure and the module hatch was closed in order to make the test more realistic. This ultimately sealed the fate of the crew. Fro the very beginning there were problems with the communication between the crew and the team overseeing the test. After numerous complaints from Grissom, the test was put on hold to give engineers time to solve the problems. At around 6:31pm, still during the hold period, fire broke out inside the Command Module. It spread quickly through the capsule, mostly due to the pure oxygen atmosphere, ultimately killing all 3 astronauts inside it. The crew sent to rescue them, was unable to open the hatch to the the large pressure difference between the outside and the inside of the CSM and was only able to reach the already dead astronauts after several minutes. Immediately after the accident, NASA launched the investigation which found numerous errors and omission on both the engineering and managerial side. Bad wiring was found the be the most probable cause of the fire with the pure oxygen atmosphere and the use of extremely flammable materials inside the capsule only increasing the severity of the fire. Flawed hatch design, which could not be quickly removed by the crew in case of emergency, was also identified as a factor contributing to the astronaut's death. A number of recommendations have been made, which increased the scrutiny around the design and test of the subsequent modules and gave astronauts the chance to influence the design and safety of the mission.
This month we also remember, Eugene Cernan, the last astronaut to walk on the surface of the Moon in 1972, during the Apollo 17 mission. He died on the 16th January at the age of 82 in hospital in Houston, Texas.
It seems like every month brings astronomers closer to solving the mystery of Fast Radio Bursts. If one publication is not enough, the first week of 2017 saw the release of three new papers that try to explain the origin of the FRBs. They focus on the FRB 121102, first observed in 2012 with the help of the Arecibo radio telescope. Of the around 20 FRBs discovered to date, it is the only FRBs know to repeat, challenging a number of theories which predict one-off cataclysmic events. An international team of astronomers turned to interferometry with the use of the Very Large Array and was able to obtain a more accurate position of the source of the burst. During the 83 hours of observations distributed over 6 months, the burst was detected 9 times. A persistent radio source has also been discovered, close to the FRB, with a separation of less than 500pc at the distance of less than 1.7Gpc. Three possible explanations we put forward to explain this unlikely coincidence. The source might be two separate, non-interacting objects found in the same host galaxy. Second possibility is that the objects interact, but so far we have not been able to directly observe this interaction. Third theory assumes that that these two sources are in fact one object, most probably involving burst from the active galactic nucleus. At this stage it is however impossible to definitely discard or confirm any of the above interpretations.Second publication focuses on better understanding the properties of the host galaxy. Through to use of spectroscopy, scientists were able to get an independent estimate of the galaxy's redshift. The redshift obtained this way, was almost two times smaller than in the study described above. This discrepancy was mainly caused by the uncertainties in the electron density model which is usually used in the FRB and pular distance estimation when no spectroscopic observations can be taken. The researchers also argue that the properties of the very small host galaxy, with the diameter of less than 4kpc (for comparison, our Milky Way has the estimated diameter of 30-35kpc) makes it very unlikely to contain an active galactic nucleus.
The last study provides better constraints on the separation between the FRB and the persistent radio source, with the largest possible separation of 40pc between the two. Two possible scenarios are considered this time: a neutron star powering a supernova remnant or an active galactic nucleus, but again with not enough evidence that favour one theory over another.
Even though Arecibo is still delivering useful science, including the FRB 121102 mentioned above, its existence is under threat. One of the most famous and most recognisable radio observatories in the world, partially thanks to its appearance in Hollywood blockbusters including Contact and Golden Eye is facing the possibility of being shut down due to the lack of funding. The U.S. National Science Foundation has recently announced it was looking for financial help from partners in order to fund the operation of this 300m diameter giant. The NSF currently funds the majority of the telescope's operation, providing $8 million of the observatory's $12 million annual budget, but says it would be able to provide only $20 million over the course of the next five years. Those interested in effectively running the radio telescope are asked to submit their proposal by the late April this year. However, the NSF has warned that if no suitable candidates are identified, other possibilities will have to be considered. The worst case scenario involves completely shutting the observatory down and stopping all the scientific operations. Introducing a fee for the scientists who wish to use the telescope is also under consideration, but as the times with the access to funding are difficult, not only for the NSF, it is likely to be met with a high dose of skepticism from the scientists, who so far have enjoyed free access to the telescope.
Interview with Dr. Teo Munoz Darias
Dr. Teo Munoz Darias is a research fellow at the Instituto de Astrofisica de Canarias in Tenerife, who specializes in X-ray binaries.These stellar systems exhibit violent outburst events, when they outshine most other X-ray sources in the sky. Dr Munoz Darias talks to us about using these systems to study the complex relationship between these outbursts and the accretion of matter onto black holes and neutron stars.
The Night Sky
Ian Morison tells us what we can see in the northern hemisphere night sky during February 2017.
- Jupiter lies in Virgo some 3 and a half degrees above its brightest star, Spica. At the start of February it rises in the east at ~00:30 but by month's end by ~22:45. It will be due south at an elevation of 34 degrees at ~06:00 at the start and at ~04:00 by the end of February. The size of Jupiter's disk increases slightly from 39 to 42 arc seconds as February progresses with its magnitude increasing very slightly from -2.1 to -2.3. On February 6th, Jupiter halts its eastwards movement across the heavens and begins to move westwards in retrograde motion for several months. With a small telescope one should be easily able to see the equatorial bands in the atmosphere, sometimes the Great Red Spot and up to four of the Galilean moons as they weave their way around it.
- Saturn is now a morning object, rising in the south-east at ~08:00 UT as the month begin but by about 06:30 UT at its end. Lying in the southern part of Ophiuchus, its diameter increases from 15.6 to 16.1 arc seconds during the month as it shines at magnitude +0.5. Towards the end of the month it will be high enough in the south-east before dawn to make out the beautiful ring system which, at over 26 degrees to the line of sight, are as open as they ever become. If only it were higher in the ecliptic; its elevation this year will never gets above ~18 degrees in elevation and so the atmosphere will hinder our view of this most beautiful planet. [Note: I have just acquired a ZWO Atmospheric Dispersion Corrector which uses two contra-rotating prisms to combat the dispersion of the atmosphere at low elevations.]
- Mercury lies low in the southeast just before dawn down to the lower left of Saturn. It brightens from -0.2 to -1.2 during the month. It will be best seen around mid-month but no details would be expected to be seen on its disk which spans around 5 arc seconds across.
- Mars is easy to find this month lying in Pisces up and to the left of Venus. They are closest on February 1st with a separation of 5.4 degrees. By month's end, as Mars continues to move eastwards and Venus begins to fall back towards the western horizon, their separation increases to just over 12 degrees. Its brightness falls slightly from magnitude +1.1 to +1.3 whilst its angular diameter falls from 5.1 to 4.6 arc seconds. No details would be expected to be seen on its salmon-pink surface.
- Venus is dominating the western sky this month shining virtually at its brightest with a magnitude -4.8. Its close proximity to a crescent Moon last month was given a lot of attention! It lies due south in mid-afternoon and can even by seen with the unaided eye. After dark in a very dark location it can even form shadows! On the 4th of February it reaches its highest elevation of 33 degrees at sunset. Its angular size increases from 31 to 46 arc seconds during the month but at the same time the phase reduces from 40 percent to 18 percent illuminated. These two effects compensate each other which is why the brightness stays so constant. In visible light no details are seen on its brilliant white surface but cloud details can be seen or imaged in the ultra-violet. In daytime when still high in the sky it can be imaged in the infrared as the blue light from the sky is filtered out. This month's astronomy digest article on imaging the Moon and planets in the infrared shows how Venus looked on the 5th of January 2017.
- 31st January to 5th February - after sunset: Venus approaches within 6 degrees of Mars If clear on the evenings of the 31st of January to the 5th of February and looking southwest one could not fail to spot Venus. But, on these nights Venus comes to within 5 degrees 23 arc seconds of Mars lying up to its left. On the 31st of January and the 1st of February, they will be joined by a thin waxing crescent Moon.
- 5th February - all evening: The first quarter Moon occults stars within the Hyades Cluster. If clear on the evening of the 5th and looking first to the south-southeast, one will see the first quarter Moon passing in front of the Hyades cluster in Taurus. At around 18:42 its dark limb will occult the pair of stars Theta 1 and Theta 2 Tauri and at ~20:32, the magnitude 2.73 star 85 Tauri. Then at 23:27 it will lie very close to magnitude -0.7 star Aldebaran - a red giant star that lies between us and the cluster.
- February 11th - just before dawn: The Full Moon below Regulus in Leo Just before dawn and, given clear skies and a very low horizon towards the west, you should easily see the Full Moon lying below the magnitude 1.35 star, Regulus, Alpha Leonis.
- February 15th - before dawn: The Moon lies close to Jupiter If clear before dawn on the 15th and looking southwest, one will see Jupiter lying between the Moon to its upper right and Spica, Alpha Virginis, down to its lower left.
- February 21st: Saturn near a waning crescent Moon Before dawn on the 21st and looking south-southeast, Saturn will be seen down to the lower right of a thin waning crescent Moon.
- February 26th - after sunset: Uranus close to Mars with both up to the left of Venus This is an excellent chance to find Uranus - perhaps for the first time - shining at magnitude 5.9 just to the lower left of Mars at magnitude 1.3. They will be just 35 arc minutes apart so Uranus will be easily spotted with Binoculars. The turquoise disk with an angular size of just over 3 arc seconds may just be seen as such using a small telescope.
Claire Bretherton from the Carter Observatory in New Zealand speaks about the southern hemisphere night sky during February 2017.Kia ora and welcome to the February Jodcast from Space Place at Carter Observatory in Wellington, New Zealand.
This month we'll start to see some changes in our evening skies. Bright Venus, which has been dominating in the west for some months, is now beginning its journey back towards the Sun. Whilst still visible in the dusk skies, it will be setting as twilight ends, around an hour and a half after the Sun, at the beginning of the February, but by the end of the month it will be dropping below the horizon just 30 minutes after sunset. Fainter red Mars is a little above, holding its position well as it moves through the constellation of Pisces. At the end of the month, Mars will pass within 34 arcminutes of faint Uranus, with both visible in the same binocular field of view, and well worth a look, particularly as this also coincides with the new moon on the 27th, although by the time it gets fully dark from our location the pair will right on the horizon.
On the opposite side of the sky, golden Jupiter is now moving into our evening skies, rising just before midnight at the start of the month and by around 10pm, as twilight ends, at the end.
Orion is now high in the north after dark, with Sirius, or Takurua, the brightest star in our night-time sky, even higher.
Below and to the right, and forming a triangle with Sirius and Betelgeuse, is Procyon, the brighter of the two main stars that form the constellation of Canis Minor, Orion's small hunting dog. Procyon is the eighth brightest star in the night-time sky and, like Sirius (at ~9 ly distant), is one of our Sun's nearest neighbours at just 11 light years away. Also like Sirius, it is in fact a binary system, with a 1.5 solar mass primary and a faint white dwarf companion.
Just over a third of the way between Sirius and Procyon, in the constellation of Monoceros, is M50, a pretty, heart-shaped open cluster of stars, visible in binoculars.
Around a third of the way from Betelgeuse to Procyon is NGC2244, a rectangular cluster of stars that is embedded in a faint nebula called the Rosette. Whilst the cluster is visible in binoculars and small telescopes, the nebula is more of a challenge and is best seen photographically.
Below Canis Minor sit 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 way 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 M 46 or 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.
Whilst NGC 2438 appears to lie within the cluster, it is probably just a chance line of sight effect as the vadial velocities are quite different. NCG 2438 is estimated to lie somewhat closer than M46 at around 2900 ly away.
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. M47 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.
Wishing you clear skies from the team here at Space Place at Carter Observatory.
Odds and Ends
Space debris has the potential to be a real problem in the future as the space around the Earth becomes more and more congested. Dead satellites, old rocket boosters and even nuts and bolts can cause huge damage if they impact another satellite. The Japanese Space agency JAXA is currently testing a new technique for hoovering up scrap material from orbit with a process called Electrodynamic tethering. This involves sending a small satellite up and launching a conducting wire to grab onto a piece of space debris and using the Earth's magnetic field to slow down the debris, thus moving it into a lower orbit where it can safely burn up. JAXA have been testing the launch mechanism for the tether about 400 km overhead. Update: Sadly after this was recorded, the experiment failed due to the tether deployment mechanism failing
Fiona's odd and end concerns a recent tabloid article about a paper co-authored by old classmate of mine. The paper can be found here and is about unexpected changes in the brightness of intermediate polar FO~Aqr. We discuss how the journalists at the (nameless!) tabloid managed to turn a perfectly normal paper about accretion rates into a sensationalized story about alien megastructures. Oh and since recording, we've learned that Astrologists do in fact, exist!
Jason Wang, a graduate student at the University of California, Berkely, has just created a video of four exoplanets, each larger than Jupiter, orbiting the young main-sequence star HR8779, in the constellation of Pegasus. The video was made by interpolating between eight different images taken by the W.M. Keck Observatory over a six-year period, so it doesn't show the full orbits of any planet -- the shortest of which is 40 years. Check it out here, and see here for more of Jason's work.
|Interview:||Dr. Teo Munoz Darias and Monique Henson|
|Night sky:||Ian Morison and Claire Bretherton|
|Presenters:||Charlie Walker, Fiona Healy and Benjamin Shaw|
|Editors:||Damien Trinh, Jake Morgan, Tom Scragg and Charlie Walker|
|Segment Voice:||Tess Jaffe|
|Website:||Charlie Walker and Stuart Lowe|
|Cover art:||The Japanese Kounotori Transport System approaches the International Space Station. CREDIT: wikimedia commons|