November 2017: Under New Skies

... and under new management, but still not on time! In the show this time, we talk to Dr. Premana Premadi, Dr. Hesti Wulandari, Dr. Taufiq Hidayat and Dr. Mahasena Putra about recent highlights in Indonesian astronomy, Josh Hayes rounds up the latest news, and we find out what we can see in the November night sky from Ian Morison and Claire Bretherton.

The News

This month in the news: Cassini; gone but not forgotten, the possible discovery of an exomoon and major results from LIGO.

Not content with being the subject of this year's Nobel Prize for Physics, gravitational waves are once again sending ripples through the scientific community. On the 16th of October, the gravitational wave observatories LIGO and Virgo announced that not only have they detected gravitational waves from two merging neutron stars, but electromagnetic counterparts to the merger were also detected, right across the spectrum. General relativity predicts that gravitational waves are something produced by objects accelerating, and the more massive the object, the bigger the wave. Since neutron stars are so massive, the gravitational waves produced by two of them merging are large enough for us to detect. Gravitational waves were first observed in September 2015, but the detection of EM waves from the same source has caused a huge amount of excitement. The first detection was made by the Fermi Gamma-ray Space Telescope, which detected a gamma ray flash made 2 seconds after the merger. The nature of this burst is incredibly similar to short gamma-ray bursts, which have long been thought to be made by neutron star mergers, but until today we have had no proof of that. Follow up observations are now going to be possible due to the localisation of the burst, made possible by collaboration between LIGO and Virgo, who together are able to localise any gravitational wave detection to about 30 square degrees. This is going to open the door to new tests of GR and the origins and nature of astrophysical phenomena we have long wondered about.

Despite crashing into Saturn on the 17th of September, Cassini is still making waves, of a non-gravitational kind. Scientist examining data from the final few months of the mission have released some of their findings, many of which the community have found surprising. Cassini spent the last 4 months of its 20 year mission repeatedly diving between Saturn and its rings, before being steered onto a collision course with the planet. By plunging into the atmosphere, Cassini was able to collect information on the composition of the planet's atmosphere, as well as its gravitational and magnetic fields. The magnetic fields have been especially surprising. It is thought that in order to generate a magnetic field through rotation of its core, a theory known as dynamo theory, a planet must have a misalignment of around 10 degrees between its rotation and magnetic field axes. Saturn has been found to have a misalignment of less than 0.06 degrees. Current theory suggests that for such good alignment, the magnetic fields should have died away within 100 million years. As this hasn't happened, scientists need to reevaluate their understanding of dynamo theory. Through the measurements of the rotation, we have also been given the best estimate of the length of a day on Saturn, which has been found to be about 10.8 hours.Cassini entered the atmosphere at a higher altitude than expected, as it was discovered that the atmosphere extends almost all the way out to the rings. Within the atmosphere, scientists were expecting to find evidence of ring material falling to the surface. This would have been reflected in high measurements of water, as the rings have a high quantity of ice within them. However, Cassini instead measured high concentrations of methane, a gas which was not at all expected to exist in the rings or upper atmosphere. This has puzzled everyone involved and the jury is still out on what leads to such abundances of a gas that is supposed to not be able to last long in such environments due to its volatility.

In the first detection of its kind, the Kepler Space Telescope has possibly found a signal from an exomoon, and now the first explorations of the nature of the moon have been released. In July, David Kipping and Alex Teachey made the announcement that within Kepler data they had discovered the signs of a giant exomoon orbiting the planet Kepler-1625b. The planet is a gas giant, somewhere in size between Saturn and a brown dwarf. At this point, it is important to note that the exomoon has not been confirmed, as the Kepler data on the planet and the exomoon is not of high enough quality, though the Hubble Space Telescope conducted observations on the 29th of October to attempt to confirm its existence. Due to the lack of data, it is difficult to characterise the exomoon, but that hasn't stopped people from trying. In a paper accepted by the Astronomical Journal on the 14th of October (available on the arXiv pre-print server), Rene Heller has published his analysis of what data there is. The bottom line is that whilst the exact mass and size of the moon is unknown, the bounds on these parameters mean that the moon could be anything between an Earth-mass gas planet to a Saturn sized rocky world. Heller's analysis points towards something somewhere in the middle, likely a Neptune-mass exomoon. This is an incredible find, as all current planetary formation theories cannot explain how such a large moon would form. There are currently three understood methods for a planet to acquire a moon. The first is through impact, such as our own moon - our planet was hit by a very large object, throwing out material which collapsed to form our moon. The second method is for the moons to form with the planet out of the protoplanetary disk. This is how Jupiter's Galilean moons formed. And the final method is for the planet to capture a pre-formed body with its gravitational field. This method explains the retrograde orbit of Neptune's moon Triton. None of these theories even come close to explaining how such a large moon has come to be around. To quote Heller: if this can be validated as orbiting a super-Jovian planet, then it will pose an exquisite riddle for formation theorists to solve!

Interview with Dr. Premana Premadi, Dr. Hesti Wulandari, Dr. Taufiq Hidayat and Dr. Mahasena Putra

Tom Scragg interviews not one but four visiting speakers from the Institut Teknologi Bandung in Indonesia with a diverse set of research interests, from estimating cosmological parameters, through probing the atmosphere of Titan to helping religious leaders spot the crescent moon in daytime observing conditions.

The Night Sky

Northern Hemisphere

Ian Morison tells us what we can see in the Northern Hemisphere night sky during November 2017.

The Planets

• Jupiter

  Jupiter passed behind the Sun on October 26th and so will become visible again in the pre-dawn sky after the first week or so November. It will then lie down to the lower left of Venus. However, by the end of November it will rise some two hours before the Sun allowing its 31 arcsecond disk, shining at a magnitude of -1.7, to be observed under clear skies. The low elevation will, of course, hinder our view.

• Saturn

  Saturn can be seen low in the southwest during twilight this month dropping down towards the horizon a little more each week. Shining at magnitude +0.5, it sets around 2 hours after the Sun on the 1st but little more than one hour by month end. It starts the month moving slowly eastwards in Ophiuchus but reaches the boundary of Sagittarius on the 18th. Last month, Saturn's rings reached their maximum tilt to the line of sight of 27 degrees and it is a real pity that Saturn is so low in the sky. Sadly, this will not improve for quite a few years as Saturn moves slowly through the lowest part of the ecliptic. Towards the end of the month Saturn edges closer to Mercury, but with both so low above the horizon after sunset, will be difficult to spot.

• Mercury

  Mercury passed between us and the Sun (Superior conjunction) on October 8th and will become visible again after sunset in the latter part of the month. From around the 17th, it might be glimpsed with binoculars low in the southwest 20 minutes after sunset shining at magnitude -0.4. It reaches greatest elongation, 22 degrees east of the Sun on November 23rd but, due to the shallow angle of the ecliptic to the horizon, never lies far above the horizon. In the last few days of the month its magnitude falls to -0.2 and it only lies ~5 degrees above the horizon 30 minutes after sunset.

• Mars

  Mars, lying in Virgo, has now become a morning object at the start of its new apparition and rises three to four hours earlier than the Sun. During the month, Mars has a magnitude of 1.7 and an angular size of just 3.9 (increasing to 4.2) arc seconds so no details will be seen on its salmon-pink surface. On the 4th, Mars is just three degrees to the upper right of Porrima, Gamma Virginis. This closes to two degrees by the 6th whilst, at the end of the month, it will lie just 3 degrees to the upper left of Spica, Alpha Virginis.

• Venus

  Venus, now moving back towards the Sun, rises some 90 minutes before dawn at the start of the month but this falls to 45 minutes by month's end. Its magnitude remains at -3.9 during the month as its angular diameter shrinks from 10.4 to 10 arc seconds. However, at the same time, its illuminated phase increases from 96% to 99% - which explains why its magnitude does not change. At the beginning of the month, it lies close to Spica, Alpha Virginis, with Venus some 100 times (5 magnitudes) brighter than Spica. By month's end, binoculars might be needed to spot it low above the eastern horizon. But please do not use them after the Sun has risen.

  HIGHLIGHTS

• November - a good month to observe Neptune and Uranus with a small telescope.

  Neptune came into opposition - when it is nearest the Earth - on the 2nd of September, so will be well placed to spot this month. Its magnitude is +7.9 so Neptune, with a disk just 3.7 arc seconds across, is easily spotted in binoculars lying in the constellation Aquarius as shown on the charts. 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. Uranus reached opposition on October 19th and so is visible all night. It will be highest in the sky in the south around 1 am BST shining at magnitude 5.7 and with a disk 3.7 arc seconds across. It lies in Pisces, one degree and 18 arc minutes up to the right of Omicron Pisces as shown in the accompanying chart. Its turquoise green colour should be seen in a small telescope and it will be easily spotted in binoculars.

• Around the 18th of November (with no Moon in the sky): find M31 - The Andromeda Galaxy - and perhaps M33 in Triangulum

  In the evening, the galaxy M31 in Andromeda is visible in the south. The chart provides two ways of finding it:

  1. Find the square of Pegasus. Start at the top left star of the square - Alpha Andromedae - and move two stars to the left and up a bit. Then turn 90 degrees to the right, move up to one reasonably bright star and continue a similar distance in the same direction. You should easily spot M31 with binoculars and, if there is a dark sky, you can even see it with your unaided eye. The photons that are falling on your retina left Andromeda well over two million years ago!
  2. You can also find M31 by following the "arrow" made by the three rightmost bright stars of Cassiopeia down to the lower right as shown on the chart.

  Around new Moon (18th November) - and away from towns and cities - you may also be able to spot M33, the third largest galaxy after M31 and our own galaxy in our Local Group of galaxies. It is a face on spiral and its surface brightness is pretty low so a dark, transparent sky will be needed to spot it using binoculars (8x40 or, preferably, 10x50). Follow the two stars back from M31 and continue in the same direction sweeping slowly as you go. It looks like a piece of tissue paper stuck on the sky just a bit brighter than the sky background. Good Hunting.

• November early mornings: November Meteors.

  In the hours before dawn, November gives us a chance to observe meteors from two showers. The first that it is thought might produce some bright events is the Northern Taurids shower which has a broad peak of around 10 days but normally gives relatively few meteors per hour. The peak is around the 10th of November but then the Moon is close to third quarter so its light will intrude. The meteors arise from comet 2P/Encke. Its tail is especially rich in large particles and, this year, we may pass through a relatively rich band so it is possible that a number of fireballs might be observed!

  The better known November shower is the Leonids which peak on the night of the 17th/18th of the month. Happily, the Moon is new so will not hinder our view. As one might expect, the shower's radiant lies within the sickle of Leo and meteors could be spotted from the 15th to the 20th of the month. The Leonids enter the atmosphere at ~71 km/sec and this makes them somewhat challenging to photograph but it is worth trying as one might just capture a bright fireball. Up to 15 meteors an hour could be observed if near the zenith. The Leonids are famous because every 33 years a meteor storm might be observed when the parent comet, 55P/Temple-Tuttle passes close to the Sun. In 1999, 3,000 meteors were observed per hour but we are now halfway between these impressive events hence with a far lower expected rate.

• November late night: Comet 2107 O1 (ASASSN).

  Throughout November, with binoculars or a small telescope, it should be possible to spot Comet 2107 O1 (ASASSN) as it nears the Pole Star. It was discovered in July by the 'All Sky Automated Survey for Supernovae' and brightened rapidly. Its brightness is now falling but, at magnitude +8 or +9, should be visible near the Pole Star this month.

• November 6th - very early morning: The Moon occults Aldebaran and the Hyades Cluster

  In the early hours of the 6th November, a near full Moon, passing across the Hyades Cluster (at a distance of 153 light years) will occult the red giant star Aldebaran which lies at a distance of 65 light years in front of the Hyades Cluster.

• November 15th - 1 hour before dawn: Mars and a crescent Moon

  In the hour or so before dawn, Mars will be seen to the right of a thin Crescent Moon.

• November 16th - before dawn: three planets and a crescent Moon

  Just before dawn, Mars, a very thin Crescent Moon, Jupiter and Venus will form a lineup along the ecliptic. In the dawn glare, binoculars and a very low eastern horizon will be needed to spot them all but please do not use the binoculars after the Sun has risen.

Southern Hemisphere

Claire Bretherton from the Carter Observatory in New Zealand speaks about the Southern Hemisphere night sky during November 2017.

Kia ora and welcome to the November Jodcast from Space Place at Carter Observatory in Wellington, New Zealand.

The Planets

Mercury now joins Saturn in our western evening skies. Unfortunately it won't be as easy to spot as its last evening appearance in July-August, as it sets before twilight ends. At the start of the month orange Antares, the brightest star in Scorpius or Te Matau a Maui, will sit between the two planets, but as the stars and Saturn slowly sink closer to the horizon from night to night Mercury climbs higher, sitting level with Antares on the 14th and with Saturn on the 24th, when it also reaches its greatest elongation east.

Constellations

Scorpius/Te Matau a Maui has been dominating our evening skies over the winter months, but is now disappearing from view, ready to reappear in the morning over the coming months. As Scorpius sets in the west, his arch enemy, and our summer constellation, Orion rises towards the east along with Taurus and Canis Major. Antares, which marks the heart of the Scorpion, is also known as Rehua to Maori. It represents one of the four Pou, or pillars, that hold Ranginui, the sky father up in the sky. It sits just above the south western horizon at around 11pm at the beginning of the month. These four pou form the basis of a celestial compass, a map of the night sky that was used to navigate the vast pacific oceans and bring our Polynesian ancestors to Aotearoa/New Zealand.

The other three pou are marked by Matariki (the Pleiades), Tautoru (the belt of Orion) and Takurua (Sirius), which line up along the eastern horizon. Matariki supports one of Rangi's shoulders and marks the rising point of the Sun at the winter solstice. Takurua (Sirius) supports the other shoulder and is the closest bright star to the Sun's rising point at the summer solstice. These two stars represent the extent of the Sun's movement throughout the year. In between, rising directly east, is Tautoru, or the belt of Orion, marking the rising point of the Sun at the time of the equinox.

Stretching from Scorpius around to Orion is Te Waka o Tamareriti, or Tamarereti's canoe, which lines up along the southern horizon in our evening sky. The front of the canoe is marked by the tail of Scorpius, with the sting representing the beautifully carved wood that adorns the prow. The star at the end of the Scorpion's curving tail marks the place where the bow meets the water, whilst Rehua or Antares, marks the crest of a wave as the great waka glides through the waters of the Milky Way.

The Southern cross marks the anchor, Te Punga and the pointers Alpha and Beta Centauri are the anchor line, Te Taura.

Orion marks the stern of the canoe, with the elaborately carved stern post rising all the way up from red Betelgeuse to bluish Rigel. A tall mast rises from the waka all the way to Achernar, high in the south, the brightest star in the southern constellation of Eridanus, the river, which we explored last month. A little below Achernar, the two small fuzzy patches of light that make up the Large and Small Magellanic Clouds mark the waka\92s sails.

• Mythology

  One story tells of Tamarereti sailing across the sky in his waka with all the stars in kete or baskets. He places the key seasonal and navigational stars in their correct positions in the sky, but he finds he has lots of smaller stars left over. So he capsizes his waka spilling all the smaller stars into the sky forming Te Ika Roa, or the Milky Way. Another story tells of Tamareriti scattering bright pebbles in the dark, lightless sky to help guide his way home. The pebbles became the stars and the wake of his waka formed the Milky Way. The sky we see in the mid-evening in October/November each year is, in fact, the same sky we see just before sunrise around June, the time we celebrate Matariki, or Maori New Year. It is said that the bright star Canopus, or Atutahi (the ariki or high chief of the heavens), pulls up the anchor at the start of the year starting the waka in motion. During the year you can track the progress of Tamarereti's waka as it moves across the sky, one day at a time.

• Pegasus

  On the opposite side of the sky is the Great Square of Pegasus, the flying horse, leaping over the northern horizon. Last month we talked a little about this wonderful constellation, its brightest star Enif, marking the horse's muzzle, and the beautiful globular cluster, M15. But we can also use Pegasus to help us find some of our nearest galactic neighbours.

• Alpheratz and M31

  The star at the bottom right of the Great Square of Pegasus is in fact Alpha Andromodae, or Alpheratz, the brightest star in the constellation of Andromeda. Located some 97 light years from Earth it is a spectroscopic binary star whose two components orbit each other in just 100 days. M31 is approaching the Milky Way at 110 km/s and is expected to collide and merge with our own Galaxy in around 4 billion years.

• M33

  A little higher and towards the east, the Triangulum galaxy or M33 is better placed in our skies. At around 3 million light years from Earth and shining at magnitude 5.7 it is just at the limit of naked eye visibility under excellent conditions, making it one of the most distant objects able to be glimpsed unaided. To find M33, head back from Andromeda towards Mirach and then continue a similar distance to the other side. Whilst spotting it with the naked eye is a real challenge, it is easily observable in a pair of binoculars. With the mass of 10s of billions of Suns, M33 is also approaching us, at around 100,000 kilometres per hour. The most striking feature of the Triangulum Galaxy is a massive region of star formation, known as NGC604, which can be seen with a small telescope. NGC604 is 100 times larger than the Orion Nebula and contains over 200 hot, massive blue stars formed just 3 million years ago. In fact, if it were at the same distance as the Orion Nebula, it would be second brightest to only the Moon in the night time sky.

• Leonids Meteor Shower

  Look out for the Leonid meteor shower, which peaks around the 17th -18thof the month, when the Earth passes through the trail of dust and debris left behind by the comet Temple-Tuttle. Whilst normally a reliable but fairly quiet meteor shower, observers have noticed that roughly every 33 years the number of meteors observed during the shower shows a marked increase as the Earth passes through the denser parts of the cometary debris trail. The radiant of the shower, from which the meteors appear to originate, is located in the constellation of Leo, which rises only a couple of hours before the Sun in our morning sky. The best time to observe the Leonids is about 2-3 hours before sunrise on the mornings around the peak. Look around 20 degrees away from the radiant point for the best chance of meteor spotting.

Wishing you clear skies from the team here at Space Place at Carter Observatory.

Odds and Ends

When you see a news article titled "the Universe shouldn't exist, scientists say" (see for example here and here), you might be a little concerned. We talk about the Nature paper that these headlines originated from, which tries to pin down a reason for the matter-antimatter asymmetry that we see in the Universe. Why do we see an excess of matter, when antimatter should have been created in equal amounts in the big bang (leading to the subsequent annihilation of both)? The scientists in question tried to see if the antiproton's magnetic moment was to blame for the asymmetry, but to one part per billion it is consistent with its matter counterpart.

Recent analysis of data from the Cassini probe suggests that Saturn's A ring may be confined by several of its satellites - Pan, Atlas, Prometheus, Pandora, Janus, Epimetheus, and Mimas - rather than Janus alone as previously thought. Planetary rings, like all astrophysical discs, tend to spread out in the radial direction when the inner particles exchange angular momentum with the outer ones. This means the inner particles lose energy and move inwards, whereas the outer particles gain energy and move outwards, causing the disc to spread out. Moons can counteract this effect due to their gravity, neatly sweeping the disc back together by forming density waves in them. These density waves give rise to the appearance of structures similar to the grooves on a vinyl record. The presence of multiple moons mean they maintain resonances (one moon completes X orbits whilst another completes Y), and this causes distinct patterns of grooves in the planetary disc.

News comes in that Stephen Hawking's thesis "Properties of Expanding Universes" has been made available on the CUP. It was so popular that the Cambridge University website crashed as reported in the Guardian. It was written in 1966 and concerned cosmology and also gravitational radiation/waves in an expanding universe. Almost 60,000 downloads were made in 24 hours, leading to the problems in the website. Prof. Hawking is most renowned for his work on black holes and the theory of Hawking radiation.

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