In the show this time, we talk to Dr. Chris Gordon about mysterious gamma rays, Ian rounds up the latest news, and we find out what we can see in the September night sky from Ian Morison and Haritina Mogosanu.
In the news this month: scrambled information escapes from Stephen Hawking, sunspot record is recalibrated and names on Pluto generate controversy.
- A stir was created this month by a short talk from Stephen Hawking at the KTH Royal Institute of Technology in Stockholm. In the talk, Hawking claimed to have new insight which may solve a 40 year old problem known as the Black Hole Information Paradox. The Paradox is a consequence of one of modern physics' most knotty and notorious dilemmas -- how to reconcile the two excellent but apparently incompatible theories of Quantum Mechanics and General Relativity. Black Holes are a stiff test for theoretical physicists as they are one of the few systems we can imagine in which both General Relativity (or GR) and the Quantum world become comparatively important, due to black holes combination of both extremely high mass and tiny size. Hawking himself was one of the first to elucidate the problem when, in a 1975 work, he pointed out that a Black Hole, as described by GR, sitting in a space surrounded by Quantum Fields would slowly radiate particles and shrink, eventually evaporating completely. The reason that this situation creates a problem is that it is difficult to decide what happens to the information which describes the system. In Quantum Mechanics, the total amount of information in any system must remain the same, with information neither being created nor destroyed. So, what happens to the information inside the Black Hole when it evaporates? According to Quantum theories it cannot simply disappear, nor can it be carried away by the emitted particles as this would involve copying the information, creating more than was there before, another forbidden process. Something must give: either black holes do not destroy information, meaing modifications to GR are necessary, or information is not conserved and it is Quantum Mechanics which needs its foundations shaking. Hawking was for a long time a supporter of GR in this contest and made a bet with two other prominent physicists -- Kip Thorne (who supported Hawking) and John Preskill -- that it was GR which was right. In 1997 Hawking actually conceded defeat in the bet and provided Preskill with the prize of a baseball encyclopaedia "from which information may be retrieved at will." Hawking conceded due to new work on so-called 'holographic theories', which propose that physical systems which exist in spaces with N dimensions can be equally as well described by sets of equations which exist in only N minus one dimension. In the case of black holes this means the three dimensional interior space of the black hole being described by a two dimensional system on its surface. This holographic idea sounds fanciful, but it was shown by Juan Maldacena, then of Harvard, now of Princeton University, that such theories are correct in at least a limited set of circumstances. And I, for one, am prepared to trust Juan Maldacena. Later work has unfortunately further muddied the waters. For example with the "firewall" problem, which states that half way through a black hole's evaporation the holographic surface can no longer contain enough information to describe the interior. Some theorists believe this could cause a wall of fire to form around the black hole, frying anything else which tries to fall in, and avoiding consuming its information. The air of mystery surrounding the problem and Hawking's celebrity has meant that much interest has been generated by the talk in Stockholm, even if it was very light on actual details on his new work and the problem. Hawking apparently suggested that chaotic mixing of information inside a black hole both scrambles the information falling in and disturbs the black hole's surface, allowing some information to break free. This would mean that black holes were not truly black but merely grey, with some kind of escape possible. Any escapees would still be significantly mangled, however, and unlikley to find much interesting left on the outside, with evaporation of a sun-sized black hole taking some ten to the power of sixty-seven years, far longer than the ten to the power of ten years our Universe has so far been in existence. Response from astronomers and physicists to the news has been cautious, with most wishing to wait for technical details rather than commenting on second hand relaying of a brief presentation. Professor Matt Strassler of Harvard University commented on his blog that he does not expect the puzzle to be resolved "soon" and points out the dangers of weighting scientist's words by their level of celebrity saying that "the resolution will probably come from a young physicist you've never heard of, or from a person not yet even born."
- Also this month, astronomers working at the Royal Observatory of Belgium in Brussels have recalibrated historical sunspot data, casting doubt on the idea that increasing solar activity may have contributed to Earth's warming climate in the past two hundred years. Sunspots, dark looking patches on the Sun's surface at points of concentrated magnetic fields, have long been known to have an 11 year cycle in the numbers observed. Astronomers have also tracked their numbers over longer periods in what is the longest running observation in science, having been started by Galileo in 1610. There were previously two premier records of sunspot activity -- the World or International record and the Group record. Differences in the methods and personnel used for counting spots over the centuries mean that it can sometimes be difficult to determine the true numbers, and the two records previously disagreed in some key aspects, such as the presence of a long-term upward trend in numbers apparently co-inciding with climate change here on Earth and tentatively called the 'Grand Modern Maximum'. The new work by the Belgian astronomers has recalibrated the data sets -- for example taking into account the failing eyesight of one aging nineteenth century Swiss observer -- with their new v2.0 record showing no evidence for the Grand Maximum. Frederic Clette, one of the authors of the work stated "There has been nothing exceptional about the level of solar activity." over the time period. This work has proved controversial, meeting disapproval from the previous maintainers of the International sunspot record. It does however bring the data into line with a third separate record, that of the US National Oceanic and Atmospheric Administration. The change would also be highly significant, requiring climate models used to predict future trends in weather to take into account a much decreased contribution from sunspot activity.
- And finally, disapproving looks have been exchanged this month between the team leading NASA's New Horizons mission to Pluto and the section of theInternational Astronomical Union (or IAU) which deals with naming features on astronomical objects. Many features identified on Pluto and its companion moon Charon by New Horizons had been named by public vote on the ourpluto.org website, run by the New Horizons team. However, formal recognition of some of these names is expected to meet resistance from the IAU, with representative Rosaly Lope commenting "Frankly, we would have preferred that the New Horizons team had approached us before putting all these informal names everywhere." The Principal Investigator of New Horizons, Alan Stern of NASA, has previous with the IAU, having criticised the handling of Pluto's declassification as a planet and also with informal naming of extra-solar planets and regions on Mars. It remains to be seen whether the IAU will allow the names of Cthulu, Spock, Kirk and Vader to sit alongside more sober ones on Pluto and Charon.
Interview with Dr. Chris Gordon
Dr Chris Gordon is a senior lecturer at the University of Canterbury in New Zealand. His research currently focusses on identifying the nature of dark matter using astronomical observations. He talks to Monique about self-annihilating dark matter, which may explain the excess gamma ray signal detected at the centre of our galaxy.
Chris explains how self-interacting dark matter models fit with our current understanding of dark matter. Some supersymmetric models naturally predict weakly interacting particles that would be good candidates for dark matter and these are currently being searched for at the Large Hadron Collider .
Another potential explanation for the observed gamma ray excess is an unresolved population of millisecond pulsars. Chris discusses the evidence for this alternate explanation and mentions how the next generation of telescopes will offer an insight into the source of the observed excess. He concludes with a discussion of future dark matter searches, including observations of dwarf spheroidal galaxies and direct detection experiments.
The Night Sky
Ian Morison tells us what we can see in the northern hemisphere night sky during September 2015.
To the south and moving westward as night progresses you may see the Summer Triangle: the bright stars Deneb (in Cygnus), Vega (in Lyra) and below them Altair (in Aquila). Towards the south later in the evening you may spot the great square of Pegasus - adjacent to Andromeda and M31, the Andromeda Nebula. To the north lies "w" shaped Cassiopeia and Perseus. Between the two, close to the Milky Way, try to spot the Perseus Double Cluster with a goods pair of binoculars. You might also spot M33 may also be visible on a transparent night with a good pair of binoculars.
- Jupiter reached superior conjunction on August 26th, and now rises shortly before the sun. It will be best seen at month's end, 18 degrees above the northeast horizon at sunrise. With a disk increasing to 31 arcsecond disk, you should be able to see its equitorial bands and 4 Galilean moons.
- Saturn can be seen after sunset low in the southwest. It lies in eastern Libra, moving slowly away from the wide double star Alpha Librae as it shines with a magnitude of +0.6. One hour after sunset at the start of the month it will lie just 10 degrees above the horizon with a 16.4 arc second disk. By month's end it will only be a few degrees elevation at this time so early this month is really our last chance to observe it for a month or so as it passes behind the Sun. The ring system, now opened out to 24.3 degrees to the line of sight, should still be visible along with Titan, its largest satellite.
- Mercury can be seen just above the western horizon for the first few days of the month reaching greatest elongation from the Sun on the 4th of September shining at magnitude +0.1. It will be lost in the twilight by mid-month before it passes in front of the Sun (Inferior Conjunction) on the 30th.
- Mars is a pre-dawn object, and lies in Leo not far from Regulus, Alpha Leonis. On the 25th the salmon-pink planet will lie just 47 arc minutes from the blue star making a very nice colour contrast. Shining at magnitude +1.8 its disk is just 3.8 arc seconds across so no details will be seen of its surface. Seen best towards the end of the month, it will then rise around 3 hours before the Sun.
- Venus, rises in the east-northeast in the pre-dawn sky an hour and a half before the Sun at the start of September but this increases to four hour by month's end as Venus moves further away in angle from the Sun. Shining at a magnitude -4.8 during the third week of the month month it will show a thin crescent, 9% illuminated, 52 arc second disk as the month begins.
On September 4th and 21st you may spot The Alpine Valley, a cleft across the Appenine mountain chain. It is about 7 miles wide and 79 miles long and a thin rill runs along its length which is quite challenging to observe.
- Neptune came into opposition on the 29th of August, so will be seen well this month. Its magnitude is +7.9 so Neptune is easily spotted in binoculars lying in the constellation Aquarius as shown on the chart. It rises to an elevation of ~27 degrees when due south. Given a telescope of 8 inches or greater aperture and a dark transparent night it should even be possible to spot its moon Triton.
- Look east before dawn on 5th September: the magnitude +0.9 star Aldebaran will be occulted by the bright limb of the Moon as it passes in front of the Hyades cluster at around 05:30 BST. Given a mount tracking Aldebaran with a telescope, you may see it reappear from behind the unlit lunar disk at 07:10 in the bright daylight sky. Be warned: the times will vary by a few minutes depending on where you live in the UK so be watching Aldebaran for perhaps 10 minutes before the two stated times.
- All clear before dawn on 10th September given a good low unobstructed horizon towards the northeast you may spot an 8% lit, thin crescent Moon just 2 degrees to the upper left of Venus shining at magnitude -4.6.
- Looking southwest one hour after sunset on 18th September (20:45 BST), Saturn will be seen 4.5 degrees to the lower left of a waxing crescent Moon.
- About one hour before dawn on the morning of the 25th, Mars will be seen less than one degree just to the left of Regulus in Leo. Shining brightly up to their right will lie Venus, dominating the morning sky whilst lying well below Mars will be seen Jupiter - a very nice planetary grouping.
- Before dawn on 28th September, from 01:12 BST until 06:22 BST we will witness a total eclipse of a Harvest Supermoon! It will display the largest apparent angular diameter of the year (33.5 arc minutes) and the eclipse lasts for three hours and twenty minutes with totality starting at 03:11 BST and ending at 04:23. At the mid point of the eclipse at 03:47 BST the Moon will then lie at an elevation of 27 degrees above the southwest horizon. As the Moon leaves the umbral shadow 05:27 BST it will lie some 15 degrees above the horizon in the dawn sky.
Haritina Mogosanu from the Carter Observatory in New Zealand speaks about the southern hemisphere night sky during September 2015.
The Milky Way
At the beginning of springtime here, the Milky Way spans the sky from north to south going through Zenith. From there, the fish hook of Maui slowly starts to drag the Milky Way down from the sky and towards the western horizon, all night long so that night after night the center of the galaxy appears lower and lower in the evening sky. Here, in the Southern Hemisphere, we are very lucky to see the Milky Way in all its brightness and beauty.
Many of the brightest stars are scattered along or near the Milky Way. Starting from North is Albireo, the beautiful orange and blue double star, in the constellation of Cygnus or the Northern Cross. On the left hand side and close to the Milky Way lays Vega, due north at dusk and setting in the late evening. On the right hand side, a celestial dolphin flips from the galactic river, revealing its two famous stars Sualocin and Rotanev- the anagram of the astronomer Nicolaus Venator! Just a few degrees higher up in the sky than the dolphin, the Eagle is flying Altair towards the galactic river. Keep lifting your head up and follow the Milky Way. With a telescope powerful enough, you will find Pluto right there near the Teapot’s handle in Sagittarius, but at 14 magnitude you would need a large aperture telescope (of 10 inches or more) to see it, as well as great star charts to pinpoint it. If Pluto is not an easy target, the fish hook of Maui in Scorpius is home of the bright star red giant Antares or Rehua in Maori. In between Sagittarius and Scorpius there are beautiful deep sky objects and now is a great time in the southern hemisphere to hunt for them. They include the Lagoon Nebula, the Omega Nebula, also known as the Horseshoe Nebula or Swan Nebula; and the Trifid Nebula.
To find directions in the Southern Hemisphere all we need to do is to follow the arch of the Milky Way. On it, midway down the southwest sky almost opposite Altair, are ' The Pointers ', Beta and Alpha Centauri. They point down to Crux the Southern Cross. There are about 27 ways to find South here and most of them involve the Southern Cross. As a circumpolar constellation, at the beginning of the spring's evening sky, Crux appears almost in the 3 o'clock position on the 60 degrees declination circle. Inside it, the brilliant Jewel Box, discovered by Nicolas Louis de La Caille and baptised so by John Herschel, or NGC 4755, is an open cluster of stars. At the center of it, a blue giant, a red giant, and another blue giant star align to make the more modern asterism of the 'traffic light'. But of course you will need a telescope to see this.
- Omega centauri, the largest globular cluster in the Milky Way can be seen as a fuzzy star roughly near the Southern Cross. In telescopes it appears like very delicate lace and it takes skill to use peripheral vision to see it but it's worth the effort.
- The 47 Tucanae globular cluster hides in the constellation of the exotic bird the Toucan. But once again the Southern Cross can help. Imagine that Crux could as a giant arrowhead, you will see it pointing left to a star, Achenar, on the other side of its declination circle. Following the arrow head, takes us between two fuzzy clouds, two thirds from Crux towards Achenar. These are the Magellanic Clouds and 47 Tucanae is located beside the Small Magellanic Cloud. In ideal conditions it should look almost the size of the full Moon.
The Moon and Planets
In Maori the Moon is called Marama which literarily can mean the white (ma) light (ma) coming from the sun Ra. The harbinger of this spring is a supermoon. A supermoon happens when the full moon coincides with when the Moon is closest to Earth, also known as perigee. Supermoons occur every fourteenth full Moon.
Mercury Whiro and Saturn Pare -a -Rao are bright planets in the evening sky. At the beginning of the month Mercury is making its best evening sky appearance of the year, low in the west. Cream-coloured Saturn is northwest of the zenith at dusk and midway down the western sky by late evening. Brilliant Venus, 'Kopu Rere Ata' is the 'morning star' for Maori, rises in the east two hours before the Sun. A telescope shows Earth-sized Venus shining as a thin crescent from 60 million km away. On 21 of September Venus displays its greatest illuminated extent as the morning "star" This means that for the next several mornings, our morning star Venus will be shining at or near its greatest brilliancy.
Odds and Ends
The closest collisional ring galaxy to the Milky Way has been discovered, at a distance seven times closer than the previous known nearest galaxy of this type. Galaxies of this type arise when two galaxies interact in a near 'bulls-eye' collision. The resultant shockwaves from the collision compress the gas within the colliding pair and kick off a new epoch of star formation, forming a ring of bright emission in the merge galaxy making it look like a Catherine Wheel. The discovery of this new object was made whilst the astronomers involved were actually searching the Southern Hemisphere sky for Planetary Nebula. The proximity of this new discovery suggests that these rare phenomenon may be a bit more common than was previously thought.
NASA's beloved Cassini mission is drawing to a close. The spacecraft, which has brought us scientific insight as well as countless magnificent images of the Saturnian system, is set to end in 2017 with a terminal dive into the atmosphere of Saturn. Dione, Saturn's 4th largest satellite (by surface area), has just been visited for the last time by Cassini and has returned a wealth of beautiful images to Earth. Flying as low as 474 km, the surface is resolved to roughly 10 metres per pixel, showing some of the finer crustal features of the moon such as small craters, crater ridges and cliff edges. Other images, taken from a range altitudes show, within its barren icy terrain, its biggest impact sites illuminated by the Sun and the soft glow of Saturn. From the approach and recession of Cassini, Dione has Saturn and its wafer-thin rings as a beautiful backdrop. The raw, unprocessed images are available here. Cassini is now en-route to Titan and will spend the rest of this year bouncing between it and Enceladus before starting its final full year of science before its 2017 final descent through Saturn's cloud tops.
|Interview:||Dr. Chris Gordon and Monique Henson|
|Night sky:||Ian Morison and Haritina Mogosanu|
|Presenters:||Adam Avison, George Bendo, Benjamin Shaw|
|Editors:||Benjamin Shaw, George Bendo and Charlie Walker|
|Segment Voice:||Iain McDonald|
|Website:||Indy Leclercq and Stuart Lowe|
|Cover art:||Saturn's moon Dione set against Saturn itself, with rings visible CREDIT: NASA/JPL-Caltech/SSI|