Fresh starts and fond farewells! In the show this time, we talk to Joe Callingham about his work with colliding wind binaries of massive stars, Michael Wright rounds up the latest news, and we find out what we can see in the March night sky from Ian Morison, Haritina Mogosanu and Samuel Leske.
This month in the news: the Japanese Hayabusa 2 probe, Israel's Beresheeft lunar craft, and a fond farewell to Opportunity.
Firstly, The Japanese Hayabusa2 probe has completed an important stage of its mission.
The spacecraft was designed to return a sample of material from an asteroid (162173 Ryugu) to earth. This was a continuation of the original Hayabusa mission, which, after studying the a nearby asteroid called 25143 Itokawa, decended to its surface and collected tiny grains of material. This material was returned to earth in 2010 and lead to a large amount of interesting science , for example the composition of this material and the effect of weathering in space .
However the original Hayabusa probe had a number of problems, one of the major things being that the sample collecting mechanism was faulty, a small amount of asteroid material was collected simply because it went into the sample horn when the spacecraft landed.
This leads on to Hayabusa2, a second mission to do a similar job to the original spacecraft. The craft was launched in December 2014, reached the asteroid in 2018 and is expected to return to earth at the end of this year. It not only carries the ability to collect samples from the asteroid but also 4 small rovers with a selection of cameras, thermometers, spectrometers and other equipment. The craft also has remote operating equipment for use off the asteroid surface, such as a near infra-red and thermal infra-red camera.
On Thursday 21st February the craft landed on the asteroid and on the 22nd a sample of material from the asteroid was collected. The way it was done was this. On the craft is a sampling horn, which can be used to collect material. When that touched the surface a small projectile (5g of tantalum) was fired into the asteroid and the resulting ejecta was collected. Another projectile will soon be fired and finally around March - April this year a larger copper projectile will be fired.
There are a few interesting things about firing these projectiles compared to the result of the previous Hayabusa mission. Firstly the amount of samples collected should be far larger and hopefully have a greater range of sizes. Secondly the use of a projectile to break material off the asteroid means it is not only surface material being collected. This is especially apparent for the planned larger projectile.
Next up, the Beresheet has lift off. This spacecraft is Israel's first lunar craft, aiming to make them the fourth country to put a lander on the moon. It is designed to be able to take high resolution images of the lunar surface as well as measure the magnetic field. The earth's magnetic field is due to its molten inside, which the moon does not have. However the moon likely was at least partially molten in the distant past, this follows from our best ideas of how stellar systems form. When rocks solidify from this state they retain some trace of the magnetic field which was around at that time. If Beresheet can measure the magnetic fields of a large number of lunar rocks and we combine that with our best ideas of the ages of lunar rocks this should allow scientists to improve our knowledge of the moons history.
The major reason the launch of Beresheet is making the news though is how it is funded . The lander was made by SpaceIL, an Israeli non profit funded by a mixture of philanthropists and the Israel Space Agency. They partnered with Israel Aerospace Industries, owned by the government of Israel. The launching was performed by one of SpaceX's Falcon 9 rockets, with NASA providing support for tracking the craft .
In other words, this lander had a far larger level of private investment than previous moon missions. This project still leaned on the support of government organisations, mainly that of Israel. However the idea, as well as the bulk of the development, were performed by SpaceIL, and the launch was performed by SpaceX. This was a private funded moon lander, made by a private non-profit, that has been built and now successfully launched. Previous to this moon landings have been performed only by the government efforts of powerful countries, the US, the Soviet Union and China, with private groups playing a supporting role in those efforts.
Another interesting thing is the cost of this lander, the lander's estimated cost of around $100,000,000 is very cheap for a lunar craft and this has lead to some interesting compromises in terms of its technology. The lander is not expected to last a long time , largely because of the heat of the lunar day. One of the compromises was the lack of good thermal control on the lander which will likely limit its operation time.
Finally in the news, a farewell to Opportunity. NASA's Mars rover. The rover first transmitted from Mars in 2004 and has far outlived its original goal of 90 days of work. However the rover fell silent after a planet wide dust storm last June and on Wednesday, 13th February NASA declared the mission completed and ended their attempts to communicate.
While this is no doubt a sad moment for astronomy, with the loss of a much loved and very useful rover, it should be remembered just how incredible it is that Opportunity was around for so long. Over its life opportunity has studied the geology and atmosphere of Mars, largely working on characterising the rocks and soils of the Martian surface with a focus on whether there is evidence that water was once on the surface of Mars. In this work, Opportunity was very successful, finding many geological features that support the idea of Mars having surface water in its history. For example patterns in the rocks of the Martian surface that resemble those formed by liquid rather than wind on earth, and the presence of chemicals such as sulphates in Martian rock which on Earth are generally created in areas with standing water . There is a wonderful wiki article explaining the evidence gathered in this mission for further reading.
Interview with Joe Callingham
Laura Driessen talks to Joe Callingham, a postdoctoral fellow at the Netherlands Institute for Radio Astronomy (ASTRON), about his work on so-called colliding-wind binaries. These systems are seen across the electromagnetic spectrum when outflows of gas ejected by two massive stars interact violently. Joe also tells us about his work using LOFAR to look at stars at very low frequencies.
The Night Sky
Ian Morison tells us what we can see in the northern hemisphere's night sky during March 2019.
- Jupiter, starts the month rising around 2 a.m. and brightens from magnitude -2.0 to -2.3 as the month progresses whilst its angular size increases slightly from 36.2 to 39.7 arc seconds. By month's end it rises by ~1 am BST so will be higher in the sky before dawn. Sadly it is heading towards the southern part of the ecliptic and currently lies in the southern part of Ophiuchus just above Scorpius. By the end of March, it will lie almost due south as the Sun rises but will only have an elevation of ~14 degrees so atmospheric dispersion will blur its image somewhat. The use of an atmospheric dispersion corrector will help to give sharper images.
- Saturn, shining with a magnitude of +0.6, rises two and a half hours before the Sun at the start of the month some 2 hours after Jupiter. Its disk is ~16 arc seconds across and its rings - which are still 24 degrees from the line of sight - spanning 35 arc seconds across. Sadly, Saturn now to the left of the 'teapot' in Sagittarius is now at the lowest point on the ecliptic and so will only have an elevation of ~10 degrees when due south before dawn in a month's time. So, like Jupiter, an atmospheric dispersion corrector could help.
- Mercury, with an angular size of 7.7 arc seconds at the start of March, reached its greatest elongation east on the 26th of February, then 18 degrees away from the Sun. On the first of March, it sets some one and a half hours after the Sun shining at magnitude +0.1. During the month, its angular size increases to 10.9 arc seconds but its brightness rapidly reduces and by March 6th, at magnitude 2, will become very difficult to spot in the twilight. Binoculars could well be needed to reduce the background glare, but please do not use them until after the Sun has set. Mercury passes between us and the Sun (inferior conjunction) on the 15th.
- Mars, though fading from +1.2 to +1.4 magnitudes during the month, remains prominent in the south western sky after sunset at an elevation of ~37 degrees. Mars is moving north-eastwards through Aries and passes into Taurus on the 23rd/24th of the month. (If only it could have been at this elevation when at closest approach last year!) Its angular size falls from 5.3 arc seconds to 4.7 arc seconds during the month so one will not be able to spot any details on its salmon-pink surface.
- Mars, begins March at a magnitude of -4.1. with its angular size reducing from 16 to 13 arc seconds during the month as it moves away from the Earth. However, at the same time, the percentage illuminated disk (its phase) increases from 72% to 81% - which is why the brightness only reduces from -4.1 to -3.9 magnitudes. Venus rises abour 2 hours before the Sun at the beginning of the month with an elevation of ~7 degrees before dawn, but both reduce as the month progresses. We have nearly come to the end of its morning apparition as it moves towards superior conjunction (behind the Sun) in August. It will not then be visible, low in our south-western sky, until late November.
Haritina Mogosanu and Samuel Leske tell us what we can see in the southern hemisphere's night sky during March 2019.
Just look up after sunset - pray that there is clear skies and you will see one of the most amazing night skies in the world. We've also been to a few star parties lately and had the opportunity to observe all night long these amazing features that set the sky of the Southern Hemisphere in a special place in our heart. Right now, the galactic centre is slowly coming back into the picture but there are still amazing views in the Carina-Southern Cross region and the Large Magellanic Cloud. So to get your own star party going, We prepared some instructions for looking up in March.
One is North of Zenith (overhead) and the other one south of Zenith. In the meantime the Southern Cross will be at the nine o'clock position on the South Celestial Circle. The Southern Cross is a circumpolar asterism, it never sets, nor rises from this latitude, only gets washed away by the light from the Sun. High in the sky, Canopus marks the midpoint between the center of our galaxy and its edge.
The brightest stars in the night sky are featuring from North To South - Aldebaran from Taurus, Castor and Pollux in Gemini, Canis Minor, Orion's stars, Canis Major, these are north of overhead then south of overhead Canopus, Carinae stars: The False Cross, the Diamond Cross and the Southern Cross, and last but not least, Alpha and Beta Centauri, the pointer stars.
Staying on the southwest part of the sky and halfway through from the horizon is Achernar. Fomalhaut is now gone, grazing the southern horizon. And on it's way to the Northern Hemisphere, the Large Magellanic Cloud is high.
The Beehive Cluster in Cancer is another amazing object, very bright, and we are lucky to share that with the Northern Hemisphere. Then there is of course, M42 in Orion, which we also share with the Northern Hemispherians.
Also reasonably high in the sky, well high enough to see ok is 'The Leo Triplet', made up of M65, M66 and NGC 3628 galaxies. The majestic globular cluster of M3 is at 20 degrees above the horizon in the Northern part of the sky. Also down in the lower part of the sky is the stunning Black Eye galaxy at 23 degrees above the horizon. Unfortunately the Virgo cluster is only 15 degrees above the horizon, so not really clearly visible.
The bottom star of the big dipper, Alkaid grazes the northern horizon early in the morning just before sunrise, precisely marking north. If we could only see it..., but there's no chance, yet we know it's there. And same goes for the Whirlpool galaxy - that gets nearly two degrees above the horizon.
The morning sky is however popular with the planets, as Jupiter rises around 1AM on the beginning of the month, (and at 11PM at the end of the month) followed by Saturn two hours later at 3AM and Venus at 4:00AM. Jupiter and Saturn are flanking the center of the Milky Way this time of the year.
If the Galaxy stretches almost from North to South in the evening sky, in the morning, it would almost have rotated to appear as if it's lined up from East to West, with Jupiter and Saturn at the Eastern end and Sirius setting in the West.
As they prepare for their journey to the underworld at the fringe of our milky city of stars, on the north-western horizon, the Pleiades, the Shining Ones (Te Tawhiti) leave behind a doppelganger here in the Southern Hemisphere, the look alike, fake twin that never leaves the sky. Higher up than the Southern Cross, the Diamond Cross carries this mirror image of the Pleiades called unsurprisingly the Southern Pleiades.
Circumpolar to Wellington, the Diamond Cross can also be found by climbing up the milky river, two thirds from the side and one third from the center this is where you will find the optical asterism (pattern of stars) of the diamond cross. At the eastern end of it, a pair of binoculars will reveal 'the Southern Pleiades', which at first sight look like the letter M to me.
Theta Carinae cluster, also called the 'Southern Pleiades' has an astronomical resemblance to the famed northern star cluster M45 in Taurus. Even though the cluster is NOT dipper-shaped like the Pleiades, is also easily visible with the naked eye, (but best in binoculars), quite young about 30 million years old and at almost the same distance from Earth (500 light years away). And just like M45, the Southern Pleiades is 15 light years across.
Odds and Ends
Josh looks back over the saga of the potential discovery of an exomoon around Kepler 1625b. Is this discovery real, or is it so reliant on very specific conditions being met that it is statistically unlikely? We pour over the various publications on the exomoon and give our thoughts along with a story of science being done right.
The LOFAR Two-metre Sky Survey (LoTSS) has recently been the subject of a special issue of the Astronomy & Astrophysics journal. The international team of over 200 astronomers (including some of our own from Jodrell Bank!) report the results of only the first two percent of the survey, yet they've discovered over three hundred thousand new objects in the radio sky. We discuss what it takes to undertake such a survey and some of its many interesting results, including probing intergalactic magnetism and the physics of black holes.
A team of astronomers at Maynooth University, led by Professor Peter Coles and including Prof. Chris Lintott, have established the Open Journal of Astrophysics, an overlay journal to provide peer-review to open-access publishing. We take a look at a recent guest post at Prof. Coles' blog, In The Dark, in which Dr. Syksy Räsänen of the University of Helsinki (one of the first to publish via OJA) lays out the reasoning behind overlay journals. With scientific publishing having become a multi-billion pound industry selling to a captive market, this could offer a chance to break the existing model, in conjunction with open access routes like the arXiv, and save more money for science. STOP PRESS: As this episode was being released, the University of California have announced that they are cutting ties with the publishing giant Elsevier after negotiations fell through (in part on the issue of open access), saving the institution $11 million USD per year.
|Interview:||Joe Callingham and Laura Driessen|
|Night sky:||Ian Morison, Haritina Mogosanu, and Samuel Leske|
|Presenters:||Emma Alexander, Josh Hayes, and Jake Staberg Morgan|
|Editors:||Beth Jones, Adam Avison, Tom Scragg, and Hongming Tang|
|Segment Voice:||Tess Jaffe|
|Website:||Tiaan Bezuidenhout, Naomi Asabre Frimpong, and Stuart Lowe|
|Producer:||Tiaan Bezuidenhout and Naomi Asabre Frimpong|
|Cover art:||NASA's Opportunity Rover Logs 15 Years on Mars CREDIT: NASA/JPL/Cornell University|