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Observing the fast and the furious: SAAO observes the first optical counterpart of a Gravitational Wave source

Following on from the major global announcement in October 2017 on the discovery of the first electromagnetic counterpart of a gravitational wave source, named GW170817, this new paper has just been published on observations undertaken at the South African Astronomical Observatory (SAAO), which are compared to the latest model predictions.  On 16 October 2017,the  SAAO, together with many other observatories world-wide, announced the important discovery of the first gravitational wave source counterpart (see: http://www.saao.ac.za/press-release/salt-and-saao-telescopes-investigate-the-origin-of-the-first-detection-of-gravitational-waves-produced-by-two-colliding-neutron-stars/). The preliminary results from the Southern African Large Telescope (SALT) and other telescopes at the SAAO were featured in a number of multi-institutional investigations utilizing a range of global facilities.

This recent paper brings together various observations made at the South African Astronomical Observatory (SAAO) to improve upon the original estimates of the luminosity of the remnant kilonova and compares the observations with recent models developed by a Japanese team. Lead author, Dr David Buckley, explains: “Our SALT spectroscopic results were improved upon by using simultaneous observations of the kilonova’s brightness at three different wavelengths using the MASTER-SAAO facility.”

The MASTER-SAAO is a southern hemisphere node of a global network of small robotic telescopes, operated from Russia, used to discover and observe “transient” events in the Universe. These include counterparts to gravitational wave sources and gamma ray bursts. The MASTER-SAAO observations were used to more accurately estimate the flux measurements made by SALT. These were then compared to recently published models. “It was fortuitous that only a matter of a few months before the observations, a preprint of a new paper on kilonova models was posted. I contacted the lead author, Professor Masaomi Tanaka of the National Astronomical Observatory of Japan (NAOJ), who kindly shared the detailed results in order for us to compare our results with these models”, says Buckley.

This allowed a direct comparison with the observations made in the optical with SALT and MASTER-SAAO and in the infrared with the Japanese Infrared Survey Facility (IRSF), also situated at the SAAO observatory site, near Sutherland. The results were very interesting, showing that the kilonova evolved rapidly, over a matter of days, from a very blue to a red object, pretty much as the models predicted. “I was quite struck by the matching of the observations to the predictions in the blue part of the spectrum”, explained Buckley, “using the just the known distance of the host galaxy. No other parameters needed tweaking.”

This initial blue component, which disappeared after about two days, was consistent with ultraviolet observations made at an earlier time by the Swift satellite. The South African Astronomical Observatory (SAAO) observations, taken over a period of about nine days, showed broad agreement with the predictions of the new kilonova models. These show a rapid reddening of the spectra over timescales of days. The results confirmed the conclusions of other investigators that the kilonova explosion, resulting from the rapid (less than a minute) merger of two neutron stars in orbit about each other, resulted in the ejection of a fast (5% to 10% the speed of light) outflow of material, which was observed at a high angle to the orbital plane of the neutron stars.

It was only through good fortune that the SALT observations were able to be undertaken. The information on the position of the optical counterpart to GW170817, crucial for any SALT follow-up, was only received several hours before the telescope could observe, from the US and Australian co-authors. As Dr Petri Väisänen, also one of the papers co-authors and the SALT astronomer observing that night commented, “After a flurry of messages and emails that afternoon in Sutherland, I finally got the coordinates in time to make the observation, which was only just reachable by SALT during the twilight. The Southern African Large Telescope was only the third observatory worldwide to provide a spectrum of the target, showing the anomalous behaviour and proving that this was no run-of-the-mill transient event.”

Once the target position had been determined a SALT target-of-opportunity observation was then undertaken using Director’s Discretionary Time. The first SALT observation was taken one and half days after the initial gravitational wave trigger. This delay was due to the time it took other imaging telescopes to survey the large area where the event occurred in order to locate its optical counterpart.  SALT was able to take one more observation, on 19 August, before it was well and truly lost as the kilonova faded rapidly and was overwhelmed by the bright twilight sky.

“We were really fortunate that the event did not happen two days later, otherwise we would never have had the opportunity to observe it with SALT”, says Väisänen. The SAAO and SALT had been poised for some time to make such an observation, since the original discovery of the first gravitational wave event in September 2015. Dr Stephen Potter, the SAAO astronomer with responsibility for attempting follow-up observations of gravitational wave sources expressed his delight at the results, “I had heard from one of our Chinese collaborators about the event and was in contact with David Buckley, who is principal investigator of the SALT transient programme, about triggering a SALT observation, once an accurate position was determined. We were getting rather desperate at the prospects of getting a precise enough position in time for a SALT observation. But in the end it came in the nick of time and we did it”

As it happened, Buckley was attending a conference on transients in Russia, when the news arrived of the detection of GW170817. However, it was only the following day, when he was travelling home, that the final all-important positional information became available. Other co-authors were able to ensure that the observations were undertaken and the data reduced quickly. Owing to the quick response of SALT and other SAAO telescopes, crucial information on the nature of the gravitational wave source was obtained. These have resulted in the publication of 8 refereed papers containing observations conducted at the South African Astronomical Observatory with the three different telescopes (SALT, MASTER-SAAO and IRSF), including the paper which is the subject of this press release.

The detection of an electromagnetic counterpart to a gravitational wave source, coming only two years after the first gravitational wave detection, bodes well for the study of future gravitational wave neutron star merger events. The ability of SALT to respond promptly and appropriately to transient alerts, in this case the GW170817 event, is one reason for the success of the observations reported here and will hopefully result in similar successes in the future.

[This Saturday, 27 January at 20h00, Dr David Buckley will be delivering a public lecture titled “Gravitational Waves: the new frontier in Astronomy”.]

LINK to the paper:

Monthly Notice of the Royal Astronomical Society, Volume 474, L71-75 (2018)- https://doi.org/10.1093/mnrasl/slx196
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SAAO helps to reveal the origins of fundamental structures in the wind of the supergiant star Zeta Puppis

A Canadian-led international team of astronomers recently discovered for the first time observational evidence in how some features at the surface of the hot massive supergiant star Zeta Puppis induce the formation of fundamental structures in its wind. The research team used the network of nano satellites of the BRIght Target Explorer (BRITE) mission to […]

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SALT and SAAO telescopes investigate the origin of the first detection of gravitational waves produced by two colliding neutron stars.

      

SALT and SAAO telescopes partake in an unprecedented international collaboration to investigate the origin of the first detection of gravitational waves produced by two colliding neutron stars.

The discovery marks the birth of a new era in astrophysics, the first cosmic event observed in both gravitational waves and light.  SALT and other SAAO telescopes have provided some of the very first data in what is turning out to be one of the most-studied astrophysical events ever.

The South African Astronomical Observatory (SAAO) and the Southern African Large Telescope (SALT) are among the 70 ground- and space-based observatories that observed the cataclysmic explosion of two colliding neutron stars, immediately after their gravitational shock waves were detected by the U.S.-based Laser Interferometer Gravitational-Wave Observatory (LIGO) and the European-based Virgo detector.

Neutron stars are the smallest, densest stars known. They are the remains of massive stars which exploded as supernovae. In this particular event, dubbed GW170817, two such neutron stars spiralled inwards and then collided, emitting gravitational waves that were detectable for about 100 seconds. The collision also resulted in a kilonova explosion of light, initially in the form of gamma rays which were detected by space-based telescopes.  The gamma rays were then followed by X-rays, ultraviolet, optical, infrared, and radio waves.

This allowed astronomers to localise the event within hours and launch follow-up observations by SALT and numerous other telescopes in South Africa and around the world.  South African activities also included the first observations contributing to published scientific results by the MeerKAT radio telescope under construction in the Karoo.

Gravitational waves from colliding black holes were first detected only two years ago, and have been detected three more times since then, leading to the 2017 Nobel Prize in Physics being awarded to three US scientists. Black hole collisions, however, are not expected to emit light.  GW170817 is the first time light and gravitational waves from the same event have been observed.

SAAO Sutherland Plateau (Credit: NRF/SAAO/SALT)

The significance of the present event lies in the combination of the gravitational waves and light.   “Imagine you have only one sense”, explains Petri Vaisanen, Head of SALT Astronomy Operations, who was the observer at SALT during the frantic search for the counterpart for the gravitational wave event.  “All your life you have merely looked at the world.  Two years ago you heard something, voices coming from somewhere around you.   But then, suddenly, you actually see someone talking. How much more will you understand about how the world works when you put those together?  Immensely more.  That to me sums up the momentous discovery, and hints at the possibilities going forward.”

August 18, 2017, the day and night following the LIGO detection and the initial successful searches in Chile for the counterpart, was a busy day for observational astronomers.  “After a flurry of messages and emails that afternoon in Sutherland, I finally got the coordinates”, continues Vaisanen.  “There was a new object, which had caused the whole of space-time to ripple, sitting at the outskirts of the galaxy NGC 4993 some 130 million light-years away.  I knew that everyone with a working telescope in the Southern Hemisphere was scrambling to get data on it.  We decided to drop all other plans for that evening, and went for a spectral observation with SALT, since you need a large telescope for such observations breaking up the light into all its colours.  It was a difficult observation since we had to do it in twilight, before it got properly dark.  I’m very proud of the whole team, SALT was only the third observatory to provide a spectrum of the target, and the first spectrum that clearly started showing anomalous behaviour proving that this was no run-of-the-mill transient event”.  

The significance of getting early observations stems from the afterglow of the collision changing very rapidly.  Piecing together the new science from the event requires combining observations spanning the first hours, days and weeks after the merger.  The first SALT spectrum has a very prestigious spot in the combined scientific paper, with thousands of authors and hundreds of institutions. In addition, several, more detailed scientific papers have also been written based on SALT, SAAO and other Sutherland observations.

“Finally, the irony of the moment for me, anxiously sitting at the telescope that evening looking at the new object, was that just three weeks before I had attended a meeting discussing the future of optical searches of gravitational waves and the SAAO part in it.  There were arguments that it could be decades before we are able to localise such events well enough for observations, and it would probably not be worth expending the effort.  It’s amazing how quickly things change.”

Sutherland telescopes reveal the details of the neutron star merger

Theorists have predicted that what follows the initial collision is a “kilonova” explosion— a phenomenon by which the material that is left over from the neutron star collision, which glows with light, is blown out of the immediate region, far out into space. The light-based observations from other large international telescopes show that heavy elements, such as lead and gold, are created in these collisions and subsequently distributed throughout the universe – confirming the theory that a major source for the creation of elements heavier than iron does, indeed, results from these neutron star mergers.

MASTER-Net full frame composite of GW170817 (Credit: MASTER-Net/NRF/SAAO)

The early SALT observations showed that the explosion was relatively bright and blue. Only two or three days later, further observations by SALT, SAAO and other major international telescopes showed that the light was rapidly fading and turning red, due to the dusty debris blocking the bluer light, as predicted by the theory of the evolution of a kilonova explosion. Simultaneously, MASTER (a joint Russian-South African optical telescope located in Sutherland) and  IRSF (Infra-Red Survey Facility; a joint Japanese-South African infrared telescope also in Sutherland) continued to monitor GW170817 for two weeks, showing that it gradually faded in the visible light but brightened in the infrared, consistent with the final stages of the afterglow from the surrounding debris.

The results of this unprecedented event have demonstrated the importance of collaborative multi-messenger observations and mark a new era in astronomy. “The ability of SALT and SAAO telescopes to respond rapidly to unexpected discoveries is a major reason for the success of these observations and will ensure similar successes in the future”, says Dr Stephen Potter, Head of Astronomy at the SAAO. “We are very proud to have played a major role in such a historical event thanks to the sterling efforts and expertise of SAAO and SALT staff who ensure that our observatory is at the forefront of world-class scientific endeavours.”

LIGO Press Release:   https://www.ligo.caltech.edu/page/press-release-gw170817

Multi-Messenger paper:  http://iopscience.iop.org/article/10.3847/2041-8213/aa91c9/meta

MeerKAT Press Release:  http://www.ska.ac.za/media-releases/meerkat-makes-its-debut-scientific-contribution-on-an-international-collaboration-and-major-discovery/

 

MEDIA CONTACTS:

SAAO/Steve Crawford, +27 21 460 9359; crawford@saao.ac.za

SAAO/Stephen Potter, +27 21 460 9337; sbp@saao.ac.za

 

The South African Astronomical Observatory is funded by the National Research Foundation. For more information about SAAO : www.saao.ac.za

 

About the NRF: The National Research Foundation (NRF) was established on 1 April 1999 as an independent statutory body in accordance with the National Research Foundation Act. The NRF is a key public entity responsible for supporting the development of human resources for research and innovation in all fields of science and technology. The organisation is one of the major players in educating and training a new generation of scientists able to deal with South African and African needs. The organisation encourages public awareness and appreciation of science, engineering and technology, and facilitates dialogue between science and society. Its vision is to contribute to a prosperous South Africa based on a knowledge economy. For more information on the operations and programs within the NRF please visit www.nrf.ac.za

 

About SALT: The Southern African Large Telescope (SALT) is the largest single optical telescope in the southern hemisphere and among the largest in the world. It has a hexagonal primary mirror array 11 metres across, comprising 91 individual 1m hexagonal mirrors. For more information about SALT please visit www.salt.ac.za

 

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CCD work begins on the WiNCam instrument

In the past week, a milestone was reached on the WiNCam (Wide-field Nasmyth Camera) instrument. This is an imaging camera system to be mounted on the new 1-m Lesedi telescope in Sutherland. It allows a wide field of imaging, 43-arcmin diameter, with a standard suite of astronomical filters. Notably, this is the largest charge-coupled device […]

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Discovery of one of the most luminous eruptions from a dying star: SALT contributes to a major international multi-wavelength effort led by South Africa.

A multinational group of astronomers have discovered what it might be the brightest nova (a luminous stellar eruption) ever observed. This mighty eruption was first detected on the 14th of October 2016 by the MASTER-instrument in Argentina. Since then it has attracted the interests of astronomers around the world, who have pointed their ground-based and space telescopes, in an attempt to understand the different aspects of the eruption.

Novae are actually binary stars, involving a white dwarf (dead star) pulling material from a close companion star that is very similar to the Sun. The material transferred to the white dwarf builds up on its surface leading to an increase in the pressure and density. When the pressure and density reach a critical stage, a thermonuclear eruption is triggered on the surface of the white dwarf equivalent to a million hydrogen bombs. During the eruption, the brightness of the star increases dramatically sometimes appearing as a new naked-eye star in the night sky hence the name nova or “new star”. The system survives the eruption and after a year or so from the nova event, the white dwarf resumes pulling material from its donor.

The new study led by Elias Aydi, a PhD student jointly affiliated with the South African Astronomical Observatory (SAAO) and the University of Cape Town (UCT), has been accepted for publication in the Monthly Notices of Royal Astronomical Society journal today. The study is based on optical observations from the Southern African Large Telescope (SALT) in Sutherland (South Africa), MASTER-instruments in Sutherland and Argentina, the Las Cumbres Observatory (LCO) telescope in Australia, the SMARTS, OGLE, and SOAR telescopes in Chile, and X-ray and ultraviolet observations from the Swift satellite.

The newly discovered very bright nova, named SMCN 2016-10a, is located toward the Small Magellanic Cloud (SMC), a small galaxy near the Milky Way, at a distance of around 200,000 light years away from us. When a Nova eruption takes place, the brightness of the star increases in a matter of a few days to reach a maximum and then decreases gradually. Nova SMCN 2016-10a reached a maximum brightness no previous nova in the SMC has ever attained. It is also at least as bright as Nova CP Pup and nova V1500 Cyg, the two brightest novae ever observed. “We are very excited to discover such extreme events which occur only rarely, especially in the SMC,” said the study’s leading author Elias Aydi. He then adds, “a combination of several factors such as the mass of the white dwarf, its temperature and chemical composition might be responsible for such a luminous eruption”. Despite the extreme brightness of the eruption, at a distance of 200,000 light years in a neighbouring galaxy, it is not possible for our naked eyes to see the nova. Such a distance also means that the eruption took place around 200,000 years ago and the light has just reached us now.
According to Aydi, “we used observations from the MASTER-instruments at Sutherland and Argentina along with the SMARTS telescope to estimate the maximum brightness reached during the eruption leading us to the main conclusion.” After its unprecedented peak brightness, the brightness of Nova SMCN 2016-10a decreased quickly in a matter of few days which tells us that the white dwarf is quite massive, probably about 1.3 times the mass of the Sun. The study co-author Patricia Whitelock, from the SAAO and UCT, stated that “In such systems, if the white dwarf keeps soaking up matter and grows beyond 1.4 times the mass of the Sun, there is a good chance that it will detonate in a really big explosion, what we call a supernova, blowing up both of the stars and anything else that gets in the way.”
SAAO astronomer, and co-author, Dr. David Buckley, explained how “The SALT high-resolution spectroscopy along with other data from the Las Cumbres Observatory have helped us understand the material involved in the eruption and even to measure their speeds, which reached just under a million kilometre per hour.” Buckley also elaborated on the ability of SALT, the biggest single optical telescope in the south, to follow up rapidly on such events providing us with particularly high-quality data.

According to study co-author Kim Page, an astronomer from the Swift satellite team and the University of Leicester in the UK, “Swift’s ability to respond rapidly, together with its daily planned schedule, makes it ideal for the follow-up of transients, including novae. We were able to follow Nova SMCN 2016-10a throughout its eruption, starting to collect very useful X-ray and UV data within a day of the eruption being reported.” The X-ray observations were essential to constrain the mass of the white dwarf in the system.

Nova events are frequently observed in the Milky Way with a rate of around 35 eruptions per year, but they are much rarer in the SMC. Nova SMCN 2016-10a is the first nova to erupt in the SMC since 2012, which adds importance to the event. From the Mullard Space Science Laboratory of the University College London, study co-author Paul Kuin says that “the present observations provide the kind of coverage in time and in spectral colour coverage what is needed to make progress in gaining an understanding of a nova in the neighbouring galaxy.” Kuin emphasizes that “Observing the nova in different wavelengths using world-class telescopes such as Swift and the SALT help us reveal the condition of matter in nova ejecta as if it were nearby.”
For more information contact:
Elias Aydi
email: eaydi@saao.ac.za
phone: +27 (0)21 460 9302
South African Astronomical Observatory and the University of Cape Town.

Dr. David Buckley
email: dibnob@saao.ac.za
phone: +27 (0)21 460 6286

The article can also be found on https://arxiv.org/abs/1710.03716

Other authors on this study include:
M. J. Darnley from Liverpool John Moores University, F. M. Walter from Stony Brook University, P. Mróz & A. Udalski from Warsaw University Observatory, S. Mohamed from the South African Astronomical Observatory and the University of Cape Town, P. Woudt from the University of Cape Town, S. C. Williams from Lancaster University and Liverpool John Moores University, M. Orio from the INAF–Osservatorio di Padova and the University of Wisconsin, R. E. Williams from the Space Telescope Science Institute (Baltimore), A. P. Beardmore and J. P. Osborne from the X-ray and Observational Astronomy Group – University of Leicester, A. Kniazev from the SALT, the South African Astronomical Observatory and the Special Astrophysical Observatory of RAS, V. A. R. M. Ribeiro from Universidade de Aveiro, University of Santiago and Botswana International University of Science & Technology, J. Strader and L. Chomiuk from Michigan State University.

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Recovery of nova spotted by ancient Koreans illuminates many stages of star system’s life cycle

On a cold March night in Seoul almost 600 years ago, Korean astronomers spotted a bright new star in the tail of the constellation Scorpius. It was seen for just 14 days before fading from visibility. From these ancient records, modern astronomers determined that what the Royal Imperial Astronomers saw was a nova explosion, but they have been unable to find the binary star system that caused it—until now.

The new study, published in the journal Nature today, is based on observations from the Southern African Large Telescope (SALT)  and the SAAO 1-meter telescope in Sutherland, Northern Cape, as well as the Las Campanas Observatories’ Swope and Dupont telescopes in Chile. The study pinpoints the location of the old nova, which now undergoes smaller-scale “dwarf nova” eruptions. The work supports the idea that novae go through a very long-term life cycle after erupting, fading to obscurity for thousands of years and then building back up to become full-fledged novae once more.

“This is the first nova that’s ever been recovered with certainty based on the Chinese, Korean, and Japanese records of almost 2,500 years,” said the study’s lead author Michael Shara, Chair of the SALT Board and a curator in the American Museum of Natural History’s Department of Astrophysics.

A nova is a colossal hydrogen bomb produced in a binary system where a star like the Sun is being cannibalized by a white dwarf—a dead star. It takes about 100,000 years for the white dwarf to build up a critical layer of hydrogen that it steals from the sun-like star, and when it does, it blows the envelope off, producing a burst of light that makes the star up to 300,000 times brighter than the sun for anywhere from a few days to a few months.

For years, Shara has tried to pinpoint the location of the binary star that produced the nova eruption in 1437, along with Durham University’s Richard Stephenson, a historian of ancient Asian astronomical records, and Liverpool John Moores University astrophysicist Mike Bode. Recently, they expanded the search field and found the ejected shell of the classical nova. They confirmed the finding with another kind of historical record: a photographic plate from 1923 taken at the Harvard Observatory station in Peru and now available online as part of the Digitizing a Sky Century at Harvard (DASCH) project.

“With this plate, we could figure out how much the star has moved in the century since the photo was taken,” Shara said. “Then we traced it back five centuries, and bingo, there it was, right at the center of our shell. That’s the clock, that’s what convinced us that it had to be right.”

Other DASCH plates from the 1940s helped reveal that the system is now a dwarf nova, indicating that so-called “cataclysmic binaries”—novae, novae-like variables, and dwarf novae—are one and the same, not separate entities as has been previously suggested. After an eruption, a Nova becomes “nova-like,” then a dwarf nova, and then, after a possible hibernation, comes back to being nova-like, and then a nova, and does it over and over again, up to 100,000 times over billions of years.

To get a better look at the present state of the binary system, Joanna Mikołajewska and Krystian Iłkiewicz, from the Copernicus Astronomical Center of the Polish Academy of Sciences, obtained several SALT spectra of the binary and the shell.  These data allowed them to identify the white dwarf companion and to determine its temperature and distance, to constrain the binary components’ masses, as well as to estimate the temperature, density and mass of the shell.

In August 2016, photometric monitoring of the system was carried out with three telescopes, and in particular, by Lisa Crause with the SAAO 1-meter telescope.  These observations revealed deep eclipses which allowed the team to very accurately derive the system’s orbital period.  In addition, the SAAO photometry (obtained over 11 days) demonstrated that the white dwarf rotates with a period of 1859 sec, the same periodicity that is present in X-ray observations.

According to Crause, “We knew from the data obtained in Chile that we were dealing with an eclipsing system, but since we didn’t know the orbital period, each night’s data from the 1-metre amounted to an additional piece of the puzzle.  After collecting light curves on several nights and putting all the data together we could work out the period – a key parameter for understanding the binary system.”

“In the same way that an egg, a caterpillar, a pupa and a butterfly are all life stages of the same organism, we now have strong support for the idea that these binaries are all the same thing seen in different phases of their lives,” Shara said. “The real challenge in understanding the evolution of these systems is that unlike watching the egg transform into the eventual butterfly, which can happen in just a month, the lifecycle of a nova is hundreds of thousands of years. We simply haven’t been around long enough to see a single complete cycle. The breakthrough was being able to reconcile the 580-year-old Korean recording of this nova event to the dwarf nova and Nova shell that we see in the sky today.”

http://www.nature.com/nature/journal/v548/n7669/full/nature23644.html?foxtrotcallback=true

Other authors on this study include K. Ilkiewicz, J. Mikolajewska, and K. Drozd from the Polish Academy of Sciences; Ashley Pagnotta, Jackie Faherty, and D. Zurek from the American Museum of Natural History; L.A. Crause from the South African Astronomical Observatory; I. Fuentes-Morales and C. Tappert from the Instituto de Fisica y Astronomia; J.E. Grindlay from the Harvard-Smithsonian Center for Astrophysics; A.F.J. Moffat from the Universite de Montreal; M.L. Pretorius from the South African Astronomical Observatory and the University of Cape Town; and L. Schmidtobreick from the European Southern Observatory.

Funding for this study was provided in part by the Polish NCN grant #DEC-2013/10/M/ST9/00086, the National Sciences and Engineering Research Council of Canada, FQRNT (Quebec), and the American Museum of Natural History’s Kathryn W. Davis Postdoctoral Scholar program, which is supported in part by the New York State Education Department and by the National Science Foundation under grant #s DRL-1119444 and DUE-1340006. 

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Catching a Glimpse of New Horizons

In the early hours of the morning on 03 June 2017, while most locals are sleeping, dozens of astronomers across South Africa will be looking up at the night sky in hopes of viewing a shadow from a mysterious, distant object.  They are part of a large, international effort to study the target of NASA’s New Horizons spacecraft extended mission.  New Horizons stunned the world in 2015 when it passed through the Pluto system and returned unprecedented images and information about Pluto and its five moons.  The extended mission will allow the spacecraft to collect data on an even more remote object, called 2014MU69 (Figure 1).

2014MU69 was discovered by the Hubble Space Telescope. It is dynamically classified as a classical Kuiper Belt object.  Because it is very faint, with a  26.3 visual magnitude, little is known about its physical properties.  A stellar occultation, during which the light of a distant star is blocked by 2014MU69, has been predicted to be observable from specific regions of the Southern Hemisphere on 03 June (Figure 2).  If successfully observed, this fleeting event could allow measurement of 2014MU69‘s size and shape, could detect rings, dust or debris, and could improve the positional accuracy, all of which would be vital information for planning the spacecraft encounter.  2014MU69 is located nearly 6.5 billion kilometers away with an estimated diameter of approximately 40 km, and the entire occultation will only last roughly 2 seconds. Thus, the observers need to be in exactly the right place, at the right time, with the right equipment to detect the brief dip in the starlight.

To optimize the likelihood of successful observing opportunities (and to avoid bad weather!), observers will be stationed in South Africa, Namibia, Chile, Brazil, Uruguay, and Argentina. Locally, SAAO observers will be using both the 74-inch telescope and the three Las Cumbres Observatory telescopes in Sutherland.  Multiple members of the ASSA (Astronomical Society of South Africa) are also contributing to the effort.  In Southern African alone, there are roughly three dozen overseas visitors who pre-shipped more than a dozen portable telescopes and specialized cameras (Figure 3).

“It is impressive to have so many people visiting South Africa and to see the amount of effort put in to taking the data. It’s a particularly challenging observation that can’t be done without international collaborators. If we are successful, this will be an occultation observation by the faintest object ever and will allow new, accurate measurements to help support New Horizons,” says Anja Genade, an SAAO/UCT student in the NASSP program whose research involves stellar occultations.

Currently, the spacecraft is approximately halfway between Pluto and 2014MU69, and it is scheduled to fly by the target on 01 January 2019. This will be the most distant Solar System object ever encountered by a spacecraft.  Pluto was revealed to be a dynamic, exciting object by New Horizons, and we are sure to expect further surprises and enlightenments from the extended mission as it explores the edge of our Solar System.

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Our new 1-metre telescope has a name – Lesedi

The South African Astronomical Observatory (SAAO) has concluded the naming competition for its new 1-metre telescope; a recent addition to the many national and international telescopes on our observing plateau near Sutherland, in the Northern Cape.

Since the day we announced the competition (which ran 26 January – 31 March), we received an overwhelming response from enthusiastic learners countrywide. The suggested names were accompanied by thoughtful motivations, many of which highlighted the keen interest learners have in astronomy, and in the advancement of technology through the development of astronomy in South Africa. The judges had a very tough decision to make.

Lesedi, a name put forward by Sam Mpho Mthombeni, a Grade 9 learner at Lentheng Middle School in North West Province, was chosen from the nine shortlisted names. Upon receiving the news, Sam had this to say, “I am very happy to be the winner. I am proud that my name, Lesedi, will be the name used for the telescope. I believe this will motivate other learners to also want to study science”, according to Dr. Ramotholo Sefako who made the call.

His motivation was “The new 1-metre telescope should be named Lesedi because it’s the first South African telescope that will be remotely operable and potentially robotic. The instrument will even help S.A. university students go places in their future visually and one cannot visualize in darkness.”  Lesedi means light in Sesotho.

In support of the telescope naming competition, the Department of Science and Technology has invited Sam Mpho Mthombeni and his parent to the DST budget debate in Parliament in Cape Town on 16 May. Thereafter, he and his parent will travel to the Sutherland Observing site for the dedication and unveiling ceremony. Later in the evening, Sam will have his very own 1-metre telescope for the night, with which to view the wonderful Sutherland night-sky.

Project scientist, Dr. Hannah Worters says, “This is the first new telescope for over forty years that is owned and operated solely by South Africa.  The next generation of astronomers will train with this telescope — and use it to make their own great discoveries — so it was important to ask our young people for a name that they can relate to, and that means something to them”.  She went on to say, “I have loved reading every one of the suggestions, and thank all the participants for their effort and creativity. The competition has truly been a highlight of this three-year project, and we are all extremely happy to go forth with Lesedi.”

Mr. Sivuyile Manxoyi, the outreach manager at SAAO thinks, “This new 1-metre telescope is a welcome addition to an already very important and interesting theme in the curriculum where learners from grade 6 learn about the historical and modern telescopes of South Africa. Learners will likely feel a stronger connection with Lesedi, especially when learning about modern telescopes because it was developed and built during their time.”

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New highly inflated exoplanet spotted around nearby star

Researchers at the South African Astronomical Observatory and others from around the world, found a new exoplanet orbiting a star 320 light years away. The planet, called KELT-11b, is a gas giant similar to Jupiter and Saturn.

However, KELT-11b is very different from the gas giants in our solar system. The new exoplanet orbits its host star – called KELT-11 – so closely that it completes an orbit in less than five days. KELT-11b has only a fifth of Jupiter’s mass, but is 40% larger in radius. This means that this new bloated planet has about the same density as styrofoam!

This puffed up planet also has a very large atmosphere, providing researchers the opportunity to study its atmospheric properties in detail. These studies will be useful for developing tools to assess Earth-like planets for signs of life in future.

The KELT (Kilodegree Extremely Little Telescope) project consists of two small, robotic telescopes. One of the telescopes, KELT-North, is located in Arizona in the USA while the other telescope, KELT-South, is located in Sutherland, South Africa. The exoplanet was first discovered with the KELT-South telescope and thereafter monitored by many telescopes around the world operated by researchers at universities as well as telescopes operated by amateur astronomers.

The KELT telescopes scan the sky every night, measuring the brightness of about five million stars. Astronomers search for stars that seem to dim slightly at regular intervals, which can indicate a planet is orbiting that star and eclipsing it. Much larger telescopes are then used to measure the gravitational “wobble” of the star – the slight tug a planet exerts on the star as it orbits – to verify that the dimming is due to a planet, and to measure the planet’s mass.

Dr. Rudi Kuhn of SAAO, who helped in the construction of KELT-South, had this to say: ”This is a very exciting discovery. The planet KELT-11b orbits one of the brightest stars known to host an exoplanet and is one of the most inflated planets ever discovered. This enables us to make some very detailed observations of the atmospheric composition of the exoplanet using much larger telescopes, like the Southern African Large Telescope (SALT). This will help us understand how these giant planets are formed, why they have such small orbits as well as what might happen to them in the future.”

Research team: JOSHUA PEPPER, JOSEPH E. RODRIGUEZ, KAREN A. COLLINS, JOHN ASHER JOHNSON, BENJAMIN J. FULTON, ANDREW W. HOWARD, THOMAS G. BEATTY, KEIVAN G. STASSUN, HOWARD ISAACSON, KNICOLE D. COLON, MICHAEL B. LUND, RUDOLF B. KUHN, ROBERT J. SIVERD, B. SCOTT GAUDI, T. G. TAN, IVAN CURTIS, CHRISTOPHER STOCKDALE, DIMITRI MAWET, MICHAEL BOTTOM, DAVID JAMES, GEORGE ZHOU, DANIEL BAYLISS, PHILLIP CARGILE, ALLYSON BIERYLA, KALOYAN PENEV, DAVID W. LATHAM, JONATHAN LABADIE-BARTZ, JOHN KIELKOPF, JASON D. EASTMAN, THOMAS E. OBERST, ERIC L. N. JENSEN, PETER NELSON, DAVID H. SLISKI, ROBERT A. WITTENMYER, NATE MCCRADY, JASON T. WRIGHT, HOWARD M. RELLES, DANIEL J. STEVENS, MICHAEL D. JONER, ERIC HINTZ

Original Paper: J, Pepper et al.: KELT-11b: A Highly Inflated Sub-Saturn Exoplanet Transiting the V = 8 Subgiant HD 93396

URL: http://iopscience.iop.org/article/10.3847/1538-3881/aa6572

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SAAO helps to reveal seven new Earth-sized planets

A new system of seven Earth-sized planets orbiting a star 40 light years away has been discovered using data from South African Astronomical Observatory (SAAO) telescope, as well as other instruments around the world. Three of these planets are located in the star’s “habitable zone”. This means that they could have liquid water on their surface, which increases the chances of them hosting life. This new planetary system now holds the record for the largest number of Earth-sized planets found.

SAAO’s 1m telescope was used to take observations of the planetary system over several nights in June and July 2016. The 1m telescope is equipped with a special camera, called the Sutherland High Speed Optical Camera (SHOC), which can take up to 70 images per second.

Dr. Amanda Sickafoose, Head of Instrumentation at SAAO, had this to say about SAAO’s involvement in this exciting work: ”This is a remarkable discovery. To find multiple, possibly habitable exoplanets orbiting the same star is exciting. This system is quite different from our Solar System, which also raises new questions. The SAAO is proud to have played a small role in this advancement in our understanding of planetary systems.”

Other telescopes used in this research include NASA’s Spitzer Space Telescope and ground-based telescopes in Chile, Morocco, Hawaii and the Canary Islands.

The planets were observed as they moved in front of their host star, called TRAPPIST-1, blocking out its light. By carefully measuring the amount of light blocked out as each planet passes in front of the star, astronomers were able to determine the sizes of the planets and the way in which they orbited TRAPPIST-1.

The researchers, lead by Michaël Gillon of the University of Liège in Belgium, also report that the three planets in the habitable zone are likely to be rocky planets, like the Earth and Mars, Venus and Mercury, making this the system with the highest number of rocky planets in the habitable zone of their parent star.

All seven planets orbit TRAPPIST-1 at a distance smaller than the orbit of Mercury, the closet planet to our Sun. The planets are able to orbit so near to TRAPPIST-1 is because it is a small, red dwarf star with temperatures much cooler than the Sun. The full details of this new discovery have been published in the journal Nature.

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