In the show this time, we talk to Richard Lake, Dr. Sarah Crowther and Dr. Giles Johnson at the Manchester Museum of Science and Industry, Mateusz Malenta rounds up the latest news, and we find out what we can see in the May night sky from Ian Morison and Haritina Mogosanu.
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This month in the news: Large dwarf galaxies, telescopic tradgedies, and Makemake's Moon.
A team of astronomers from Cambridge University has reported a discovery of a never-before seen dwarf galaxy in the close neighbourhood of our Milky Way. Gabriel Torrealba and his colleagues used VLT Survey Telescope, a European Southern Observatory, 2.6m instrument, to find this new object, named Crater 2, located in the constellation of Crater at the distance of 117.5kpc, that is 383,000 light years from the Earth. It is the second major object recently found in this area, after the discovery of Crater globular cluster in 2013. With its half-light radius, which defines the area that emits half of the total surface brightness, of around 1070 pc, it is currently the fourth largest dwarf galaxy orbiting Milky Way, after Large and Small Magellanic clouds, and Sagittarius Dwarf Spheroidal Galaxy.
Despite its large size, the object was extremely difficult to find, due to its low total luminosity, making it much less luminous than the other Milky Way's companions of comparable size and placing it amongst the dimmest dwarf galaxies ever seen. These unusual properties mean it is currently very difficult to describe the evolution of Crater 2 with certainty. Objects with similarly low surface brightness, known as ultra diffuse galaxies (UDG) have previously been reported. They are extended objects, which is most likely caused by tidal interactions with their host galaxies. In the case of Crater 2 however, this evolutionary scenario can be ruled out, as it appears to be almost perfectly spherical in the images, without any visible signs of disruption from the Milky Way.
The team that made the discovery tried to gain some insight into the origin of this peculiar dwarf galaxy, but running a number of computer simulations. They concluded it was possible that Crater 2 had previously belonged to a larger group of galaxies, which is falling towards the Milky Way. Dwarves Leo II, Leo IV and V, Crater 2 and the Crater globular cluster mentioned above, all seem to be aligned on the sky along a great circle.
With 10 objects further than 100 kpc from the Milky Way, having 5 of them randomly aligned in such way is unlikely, with a probability of less than 0.005. Further simulations of the orbit and velocity distributions, showed it is possible that these objects once formed a much denser association and are currently undergoing disruption, when falling towards the Milky Way. It is possible that this object comes from a previously unseen class that is a part of the general dwarf galaxies family and represents satellites that are relatively young Milky Way companions. However, due to their very low surface brightness, they have managed to escape detection so far, because of the sensitivity limits of instruments currently in use.
The month of April has been quite an unfortunate one for space telescopes operating in our Solar System. First, on the 7th of April, during routine communication, Kepler spacecraft was found in the emergency mode. Previous contact, 3 days earlier, did not show signs of any malfunctions and the spacecraft was assumed to be in a good condition. The telescope was about to begin new phase of observations at the beginning of April, when astronomers were meant to use microlensing, rather than the usual transient method, to look for even smaller planets, than those discovered so far. On Sunday, 10th April, the telescope was successfully recovered from the emergency mode and is currently back to its regular observing schedule, continuing the extended K2 mission. It is however still not known what caused Kepler to enter the emergency mode, and remain in it for approximately 36 hours. This is problematic, as the spacecraft has already suffered significant damage, which severely limited its scientific capabilities. K2 mission, is a result of an effort to make the telescope operational after its second reaction wheel failed in May 2013, making it impossible to accurately point the spacecraft. Scientist hope that that whatever caused Kepler to enter the emergency mode, has not caused any lasting damage to the telescope, which they hope will perform flawlessly for the remainder of its extended mission.
The biggest blow the to astronomical community came on 28th April, when the Japan Aerospace Exploration Agency (JAXA) announced it had lost its Hitomi satellite and would cease any efforts to bring it back to the operational state. This $286m X-ray satellite, was a major project, expected to revolutionise the X-ray astronomy. As reported in the Jodcast news section in April, successfully launched on 27th February, it stopped working unexpectedly, just 39 days later, on 26th March. The next day, US Strategic Command's Joint Space Operations Center, announced it had observed debris in the close vicinity of the spacecraft, most probably coming from solar panels that have broken away from the telescope. The reason for this mishap is still under investigation, but preliminary results put blame on the attitude control system, which incorrectly read the change in attitude as rotation and tried to stop it by activating the on-board reaction wheels, which caused to telescope to actually rotate. The control system could not correct the previous errors and fired a set of thrusters to counteract the rotation. However, an incorrect command was executed, causing the engines to accelerate the rotation even further. All these factors resulted in the spacecraft reportedly rotating once every 5.2 seconds, and caused its disintegration. The research team managed to perform one significant observation, towards the constellation of Perseus, where the telescope observed gas motion within a galaxy cluster. This accident will undoubtedly cause a loss of than the money invested in the development and building of the spacecraft. It is currently estimated, that it would take around 5 years, to developed another set of instruments, similar to those that have flown on-board the destroyed satellite.
And finally, the Hubble Space Telescope, which has just finished its 26th year in space this April, was used to discover the first moon of the distant dwarf planet Makemake. Currently dubbed MK2, the object was first seen in the images captured by the Wide Field Camera 3 instrument in April 2015. The newly-discovered moon has an estimated diameter of 160km and orbits its host dwarf planet at a distance of around 21,000km. Makemake is the second brightest icy dwarf planet (about fifth of the brightness of Pluto), and it is 1300 times brighter than its moon. As previous searches failed to find any evidence of the moon's existence, scientists believe, that its orbit is edge-on as seen from the Earth, meaning that the light coming from MK2 is completely lost as it passes in front of the bright planet. This time however HST was pointed towards Makemake at the right time, and caught a glimpse of MK2. It is currently unknown, why exactly the surface of the moon is so dark. One possible hypothesis is, that unlike Makemake, which is massive enough to hold to its methane crust, MK2's surface is free to escape the moon's gravitational potential when it sublimates. Further observations are needed to provide more information on the shape of the moon's orbit, which will help scientist to answer the question about the origin of this satellite and whether it came to existence as a result of a collision between Makemake and another object or was once a free-floating Kuiper Belt Object, captured by the dwarf planet. It will also provide us with new information about Makemake itself, as astronomers will be able to learn more about its composition, but measuring the variations in the moon's orbit.
Interview with Richard Lake
In our first interview at the Manchester Museum of Science and Industry (MOSI), Ian grabs Richard Lake from Polestar Planetarium between shows to discuss what planetariums are all about, and gets him to reveal some of the trickier questions he has been asked by schoolchildren in the past.
Interview with Dr. Sarah Crowther
In our second interview at MOSI, Ian catches up with Dr. Sarah Crowther for her second Jodcast interview to talk about some exotic goodies she's brought along for outreach purposes, including meteorites, and pieces of the Moon and Mars.
Interview with Dr. Giles Johnson
In our final MOSI interview at the Manchester Light Fantastic Science Festival, Ian talks to biologist Dr. Giles Johnson about how different wavelengths of light impact plant growth, the requirements for healthy extraterrestrial foliage, and some potential problems with terraforming Mars.
The Night Sky
Ian Morison tells us what we can see in the northern hemisphere night sky during May 2016.
Highlights of the month
May 9th - the Transit of Mercury across the face of the Sun
On May the 9th, we will, if clear in the UK, be able to witness the complete passage of Mercury's disc across the face of the Sun. The transit begins soon after 11 hours UT, the midpoint of the transit is at 14:58 UT and Mercury leaves the Sun's disk at 18:42 UT - a total time of 7 and a half hours. This is Mercury's first transit since 2006 and the next will occur on November 11th 2019 but will not be so easily visible from the UK. These are three of the 13 or 14 Mercury transits that occur each century.
Mercury's black disk will appear only 10 arcseonds across so binoculars or a telescope will be needed to observe the transit. If direct viewing is to be made a suitable solar filter must be placed in front of the objective(s). Filters made using Baader Solar Film are probably best. Alternatively, an image of the Sun can be projected onto white card using a small telescope or half binocular. An all metal eyepiece is needed to prevent heat damage and it's probably best to limit the aperture to ~1 inch across using a cardboard mask. Always take very great care when viewing the Sun - it is the only astronomical object that can harm us!
At first glance Mercury's disk might, at just 1/200th of the Suns width, appear as a sunspot, but it will be precisely round, be even darker, will lack a grey penumbra and - of course - it will be moving across the Sun' disk. It will be interesting to watch the ingress and exit of Mercury's disk taking 3 minutes and 12 seconds to do so. Let's hope for clear skies!
May 22nd to June 8th: Mars at its best for 11 years
Mars reaches opposition - that is when the Earth lies between the Sun and Mars and when it will be approximatly due south at midnight (UT) or 1 am (BST) - on the 22nd of May, so it will be visible for most of the hours of darkness. However, it will actually be closest to the Earth and so have its greatest angular size of 18.6 arc seconds some 8 days later on the 30th of May. The angular size at closet approach varies due to the ellipticity of the orbit of Mars (and to a far lesser extent to that of the Earth)and will reach 26 arc seconds during 25,695 AD. At closest approach in 2003, Mars reached an angular size of 25.1 arc seconds, its largest angular diameter for 60,000 years. In July 2018 it will reach 24.2 arc seconds across but for both this opposition and that in 2018, Mars will be very low in the ecliptic and hence at low elevation so that the atmosphere will limit our views of the red (actually salmon pink) planet. Happily, it will be higher in the sky at the opposition of 2020.
To find what should be visible at any time, one can use the Sky & Telescope application.
May: Look for the Great Red Spot on Jupiter
This list gives some of the best late evening times (in UT) during May to observe the Great Red Spot (which is unusually vivid this year) which should then lie on the central meridian of the planet.
- 3rd - 00:22
- 5th - 21:52
- 10th - 21:01
- 12th - 22:39
- 17th - 21:48
- 19th - 23:27
- 24th - 22:36
- 29th - 21:45
- 31st - 23:24
May 5th and 6th before dawn: The Eta Aquarid Meteor Shower
The Eta Aquarids are one of the finest meteor showers that can be seen from the southern hemisphere, but, in the northern hemisphere, may be glimpsed in the pre-dawn sky in the south-east around 90 minutes before dawn. Pleasingly, this year the peak corresponds to new Moon so there will be no moonlight to hinder our view.
May 7th - one hour before sunrise: Saturn, Mars and Antares
Looking to the South-Southwest in the hours before sunrise, Saturn, above, and Mars, to the upper right, can be seen close to Antares in Scorpius.
May 7th - after sunset: a very thin waxing crescent Moon
If clear at sunset, and given a low horizon in the West-Northwest, you may be able to spot a very thin waxing crescent Moon just 1 percent illuminated. Binoculars may be needed, but please do not use them until after the Sun has set. You may be able to observe the major part of the Moon's surface illuminated by light reflected from Earth - called Earthshine - as seen in the accompanying image taken by the author at the Isle of White Star Party.
May 14th and 27th, evening: The Hyginus Rille
These evenings, should it be clear, are a superb time to view the Hyginus Rill as it will lie close to the terminator. For some time a debate raged as to whether the craters on the Moon were caused by impacts or volcanic activity. We now know that virtually all were caused by impact, but it is thought that the Hyginus crater that lies at the centre of the Hyginus Rille may well be volcanic in origin. It is an 11 km wide rimless pit - in contast to impact craters which have raised rims - and its close association with the rille of the same name associates it with internal lunar events. It can quite easily be seen to be surrounded by dark material. It is thought that an explosive release of dust and gas created a vacant space below so that the overlying surface collapsed into it so forming the crater.
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
Jupiter is now a little past its best, but still stands out high in the South at nightfall. Its brightness falls slightly from magnitude -2.3 to -2.1 whilst its angular size drops from 41 to 37 arc seconds during the month. Jupiter spends the month below the hindquarters of Leo, halting its retrograde motion westwards across the sky on May 9th. Jupiter sets around 4 am as May begins but by 2 am by month's end. 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 Gallilean moons as they weave their way around it.
See highlight above.
Saturn rises in the late evening about 30 minutes after Mars as May begins. Its brightness increases slightly from +0.2 to 0.0 magnitudes during the month whilst its angular size grows to 18.4 arc seconds. Saturn's rings are tilted by 26 degrees from the line of sight - almost as open as they ever get - and span 42 arc seconds. It is moving towards opposition on the night of June 2nd. Saturn forms a triangle with Mars and Antares throughout the month, separated from Mars by 8 degrees as May begins and by 15 degrees at month's end. As Saturn moves slowly across the heavens, it stays at a near constant distance from Antares.
See the highlight above.
Mercury. The top highlight this month is Mercury's transit across the face of the Sun on May the 9th, but otherwise it will be too dim and low above the horizon to be seen.
See highlight above.
See highlight above.
Haritina Mogosanu from the Carter Observatory in New Zealand tells us about the southern hemisphere night sky during May 2016.
- (Atu) Tahi
- (Taku) Rua
- (Tau) Toru
In Maori, tahi, rua, toru means one, two, three.
Three bright planets and the brightest stars share the evening sky this May, and you can see them in three ways when you look at the sky: with the naked eye, with a pair of binoculars and with a telescope. I love each of these methods - they are, each in their own way, very special and each adds a layer of depth to the previous one, which is why I always recommend to people to never buy a telescope unless they have got naked eye stargazing or binocular observing sorted, otherwise it would be too frustrating to look for all these deep sky objects.
So, what can we see with the naked eye in May?
Soon after sunset, circumpolar Atutahi/Canopus, the second brightest star, is southwest of the point directly overhead. Tahi means One in Maori, suggesting that Atutahi is the chief of the stars and visible all night long. Takurua/Sirius, the brightest star, appears northwest of the zenith. Rua means two in Maori and Takurua is one of the two wives of Ra, the Sun. Below Takurua are bluish Puanga/Rigel and reddish Putara/Betelgeuse, the brightest stars in Orion. Between them is a vertical line made of the three stars, Tautoru. Toru means three in Maori and it is the name given to Orion's belt.
The three planets are, in order of appearance, Jupiter, Mars and Saturn.
Midway up the southeast sky are 'The Pointers', Beta and Alpha Centauri. Soon after dusk Arcturus appears in the northeast, often twinkling red and green as the air breaks up its orange light. Golden Jupiter appears in the north. It is the brightest starlike object in May and lights up the night until the early hours of the morning.
Orange Mars comes up in the east just after sunset. It will be at opposition on 22 May, which also means that Mars will be very bright. The term opposition can be a little confusing, but what opposition actually relates to is the way we see Mars from Earth as it sits directly opposite to the Sun with the Earth between them. In May 2016, Mars rises in the east just as the Sun sets in the west. Then, after staying up in the sky the entire night, Mars sets in the west just as the Sun rises in the east. Since Mars and the Sun appear on opposite sides of the sky, we say that Mars is in "opposition". Also, if Earth and Mars followed perfectly circular orbits, opposition would be as close as the two planets could get, but their orbits are neither circular nor coplanar, coplanar meaning in the same plane, so the closest approach between Mars and Earth in almost 60,000 years occurred during 2003.
During opposition, Earth passes between the Mars and the Sun. This only occurs once every 26 months because Earth makes two trips around the Sun in about the same amount of time that Mars takes to make one trip. Sometimes (like now) we will be on the same side of the Sun as Mars (at opposition). Some other time will be on the opposite side. Go figure! And when Mars is on the opposite of opposition it will actually be hidden behind the Sun as it comes between us and Mars, which is the time when communications with Mars are avoided as there is a lot of interference from the Sun.
As the sky darkens, Saturn appears below Mars.
Mercury is very close to the Sun in May so not visible from anywhere in the world with one exception. This is why I will only just mention a spectacular event, which enchants the clear skies viewers from everywhere else but East Asia, Japan, Indonesia, Australia and New Zealand. On Monday, 9 May 2016 starting at 11:15:00 p.m. NZST, most of the world will be able to see the planet Mercury transiting across the disc of the Sun. From Earth, we can only see Mercury and Venus transiting the Sun as these two planets are in between Earth and the Sun. There are about 13 to 14 transits of Mercury in a century and they all occur within a few days from 8 May and 10 November. We will not be able to see this one for the simple reason that it happens during our night time. We can, however still watch it online from New Zealand, as several different webcasts will cover the transit. The event will last for seven hours.
Crux, the Southern Cross, is visible southeast of the zenith, to the right of 'The Pointers', Alpha and Beta Centauri. Zenith refers to an imaginary point directly "above" a particular location, on the imaginary celestial sphere.
Orange Antares, right of Mars, marks the body of Scorpius, the Scorpion. Antares means 'rival to Mars' in Greek for the planet and star are often similar in colour and brightness, but not at this time of year.
The Milky Way, our edgewise view of the galaxy, is brightest in the southeast toward Scorpius and Sagittarius where its centre lies, and it can be traced up the sky past the Pointers and Crux, fading toward Sirius. Its nearby outer edge is by Orion, where the Milky Way is faintest.
The Clouds of Magellan, LMC and SMC, are two small galaxies midway down the southern sky, easily seen by eye on a dark moonless night. If you use your peripheral vision, which means using the edge of your vision out of the corner of your eye instead of looking directly at them, it will reveal more detail. It’s a trick we use in stargazing, and has to do with how our eyes are constructed. Night vision is mostly based on our rod cells (the ones responsible with detecting movement, which is also something we see very well with on the edge of our vision).
Once you've mastered the naked eye observing, it's time to try the next level, binoculars.
What can we see with a pair of binoculars?
Binoculars come in many shapes and forms - a great size for stargazing is 7 x 50 or 10 x 50. The first number is a measure of power, it means how much these binoculars magnify, in this case the 7 and the 10. The second number is the diameter of the objective (the big lenses at the front) in millimeters, in this case the 50. I love binoculars, they are my favourite aids to observing the night sky because they are light, you can take them easily with you on trips and they don't really require assembly or polar alignment. With a tripod attached they are truly magnificent. We have two eyes, so binocular views are more spectacular in many regards than telescopic, because binoculars give depth of view as they engage both eyes in the process.
There are a few great objects that you could admire with binoculars. For instance Jupiter and its four moons. Also on the ecliptic, M44 - the Praesepe in Cancer. Known as the beehive, the open cluster swarms with stars. It is as far as 577 light years away and estimated to be 730 million years old with an average magnitude of 3.5. Also in Cancer, M37 is another open cluster, one of the oldest known, almost 3.2 billion years.
Another good target for binoculars is Leo, marked by the bright Jupiter. Jupiter is 750 million km away, so it is always worth a look. Its four big "Galilean" moons look like faint stars near the planet. One or two can be seen through binoculars. All four are easily seen in any telescope magnifying 20x or more. Sometimes one or more of the moons will be invisible as they pass in front of, or behind, Jupiter. The Moon will be near Jupiter on 15 May. Close to the area south of the triangle that marks Leo's hips, M65, M66 and NGC 3628 will be visible depending on the size of your binoculars. They are also known as the "Leo Trio". Also in Leo, M105 is an elliptical galaxy. Last but not least M96, another galaxy in Leo, lies about 35 million light years away. At the beginning of May Jupiter sets around 2am, reducing to around midnight by the month's end so you might want to look for these objects in the first part of the night.
If all else fails, simply take your binoculars and swipe the milky way from one edge to the other. You might not figure out exactly which objects you are looking at but you will definitely find amazing sights, especially in the region close to Carina. You will find there IC2602, NGC3114, NGC353, NGC2516, that are all open clusters, then in Crux NGC4755 which is another open cluster, NGC2451 in Puppiz, and IC2391 in Vela.
Lower down, Omega Centauri is a globular cluster in Centaurus and in Scorpius, there are the Butterfly Cluster, M7 open cluster and NGC6231 open cluster.
Saturn is a great sight even with a pair of binoculars and this time its rings are near maximum tilt. It is 1,360 million km away. Titan, its biggest moon, orbits four ring diameters from the planet. You might also be able to see Titan with binoculars.
One of my bibles in terms of what to see in the night sky is Philips's Night Sky Atlas, by Robin Scagell and with maps by Will Tirion. Every time someone asks me what telescope to buy, I ask them if they do have a pair of binoculars. If the answer is no, then I always say don't buy a telescope if you have not looked at the sky with binoculars. Even if you only used them to locate objects that are too faint for the naked eye or hidden by light pollution. Some of the best views of the larger star clusters, bright nebulae and comets are best seen with binoculars.
This concludes our Jodcast for May 2016 at Space Place at Carter Observatory. As the Maori say, E whiti ana nga whetu o te Rangi (the stars are shining in the sky) Ko takoto ake nei ko Papatuanuku (whilst Mother Earth lays beneath)
May you enjoy clear and dark skies so that you can see the stars and remember that we are made of the same star dust as they are! Kia Kaha and clear skies from the Space Place at Carter Observatory in Aotearoa New Zealand.
Odds and Ends
You might have spotted some of our Jodcasters at recent event the University of Manchester ran at the Trafford Centre on 23rd and 24th April. We were there as part of ScienceX, with a thermal camera, an Oculus rift and various hands-on physics demos. Since Manchester is the European City of Science this year, there are lots of science-themed activities going on around the city this summer. You can find out more on the website, which lists upcoming events. We discuss some of these in the show, including:
- Bluedot festival, 22nd-24th July, Jodrell Bank Observatory
- Pint of Science, 23rd-25th May
- Bright Club
A weekend of performances, DJ sets, comedy, talks, workshops and live experiments at the Jodrell Bank Observatory.
Three evenings of talks from researchers taking place in pubs across the city. Speakers include our very own Tim O'Brien, Sarah Bridle and Mitch Mickaliger.
Researchers do stand-up comedy! Check their website for details of upcoming events.
Our snarky tearoom whiteboard makes a return in response to listener Ben Harding's question: 'What would you most like to find using the Lovell Telescope? What are you most hoping to learn?'
|Interview:||Richard Lake and Ian Harrison|
|Interview:||Dr. Sarah Crowther and Ian Harrison|
|Interview:||Dr. Giles Johnson and Ian Harrison|
|Night sky:||Ian Morison and Haritina Mogosanu|
|Presenters:||Fiona Healy, Ian Harrison, and Monique Henson|
|Night Sky Music:||Rhian Sheehan|
|Editors:||Adam Avison, James Bamber, Alex Clarke, Nialh McCallum, Haritina Mogosanu, Benjamin Shaw, and Charlie Walker|
|Segment Voice:||Kerry Hebden|
|Website:||Charlie Walker, Saarah Nakhuda and Stuart Lowe|
|Cover art:||Mount Taranaki, New Zealand. CREDIT: Mat Sheldon (@TravellingMat72)|