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A supernova (= new star) is a large star, which having reached the end of its life, ends up in blowing itself up. In doing so it becomes briefly becomes very bright. The one that Stuart found was so distant that despite its brightness it only became a 16th magnitude object as seen from the Earth. This is more than 10 000 fainter than the faintest stars which can be seen with the unaided eye.
Stuart made his discovery photographically. He regularly takes pictures of a number of galaxies which he monitors and compares his latest with earlier ones for a new bright object.
Other bright objects in the photo are "foreground" stars in our own Milky Way galaxy. The galaxy NGC 134 is about 56 million light years away, so light from the galaxy has taken this long to reach us. Thus the super nova actually occurred 56 million years ago, but the light from it has only just got here.
Light from the Sun takes just over 8 minutes to reach the Earth. It takes a little over 4 years for light to reach us from the brighter of the two Pointers, which is the nearest star, apart from the Sun. The Milky Way galaxy has a diameter of about 100,000 light years, the time it takes light to cross it. So the star Stuart discovered is more than 500 times further away.
The brightest star in the photo is 12th magnitude, and 2' from the galaxy.
The best guess is that it was a re-entering satellite. It was probably more than 100 km above the ground. Friction with the thin air was making it glow. The train or trail was smoke being lit up by sunshine. (The sun would still have been visible at that altitude.) Presumably the satellite burnt up over the sea east of the South Island.
The object cannot have been a meteor. Most meteors burn up in a second or less. None last more than a few seconds. It was not a comet, as some described it. Comets move very slowly against the background stars. Even a comet very close to the earth takes hours to show any shift against the stars. A low satellite crosses the sky in a few minutes, as this object did.
The accompanying citation reads:
The 41st AAVSO Merit Award was presented to Albert Jones for his dedicated contributions to variable star astronomy for over 60 years, including over 500,000 visual observations of Southern Hemisphere stars, providing decades of uninterrupted coverage; contributions to Southern comparison star sequences; research collaborations with professional astronomers, providing valuable data and insight into target variable star behavior; sharing his meticulous observations with the Royal Astronomical Society of New Zealand, and with the AAVSO for worldwide distribution; mentoring countless new observers, particularly in New Zealand, with good humor, patience, and grace; and inspiring variable star observers worldwide.
Arne Henden writes: "I hope to give Albert his award personally during my next visit to New Zealand. Congratulations on this justly-deserved honor!"
New Zealand astronomers have contributed yet again to the discovery of planets orbiting distant stars in our Milky Way galaxy. There are now about 250 known so-called extrasolar planets (or simply exoplanets), but this new discovery has revealed, for the first time, something similar to our own solar system.
A distant star (a so-called red dwarf) about half the mass of the Sun has been shown to have two orbiting planets, such that the three objects constitute a scaled down version of our own Sun, Jupiter and Saturn. Details of the find are published in the February 15, 2008, issue of the renowned US journal `Science'.
"This is an exciting development", says Victoria University astrophysicist Dr Denis Sullivan and a member of MOA - the Microlensing Observations in Astrophysics group and one of the discovery teams. "In addition to the sheer beauty of the event, it is another step along the way to the possible identification of an Earth-like planet around some distant star, which could be a habitat for life forms."
Most exoplanets have been found by detecting the reflex motion of the star caused by an orbiting planet, but the method used for this latest detection is called gravitational microlensing. Following the predictions of Einstein's theory of general relativity, light paths are curved by the gravitational field of a mass, and this can lead to the brightening of a background star if the light rays pass very close to an intermediate lens mass on their way to the observer.
For almost perfect alignment, very large increases in brightness occur, and if the lensing mass is also a star-planet system, then information about the planet or planets is encoded in the changing brightness of the star with time.
In this particular case, this `light curve' of the background star exhibited five separate brightenings over a period of about 10 days and a maximum increase by a factor of about 600.
Two things are required for success in this work. First, teams of observers distributed around the globe are required to catch all the important changes in the light curve, and second, a large amount of computer modelling is needed to extract from the light curve the key planetary information.
The star brightening was first detected in March 2006 by a Polish group known as OGLE, who use a telescope in Chile. Subsequently it was regularly monitored by OGLE and three other international teams including MOA and two called microFUN and PLANET/Robonet.
The NZ/Japan MOA group (involving astronomers at four NZ universities) used a telescope at Mt John, Lake Tekapo, operated by the University of Canterbury, while the microFUN group had two separate observers in Auckland, Dr Grant Christie and Jenny McCormick.
The two-planet signature in the complex light curve was deciphered and modelled by Professors Scott Gaudi and Andrew Gould of Ohio State University, working with Professor David Bennett of Notre Dame University in the USA. The MOA group also has the appropriate complex modelling capability in NZ, largely as a result of several PhD thesis projects (Dr Aarno Korpela, Wellington and Dr Nick Rattenbury, Auckland), and this capability is being used to confirm the key deductions.
This success is a classic example of many small telescopes and dedicated observers combining in a collaborative way to produce a major scientific discovery. The MOA group would like to specifically mention the vigilance of their Mt John on-site observer, Paul Tristram, for his rapid response to the initial alert.
The findings are reported in the February 15, 2008, issue of the journal `Science' as the cooperative effort of 4 international teams and some further researchers, comprising in total 69 authors from 11 countries, with Dr Scott Gaudi from Ohio State University (USA) being lead author.
Further details are available of IYA2009 in New Zealand and internationally.
The night sky over Tekapo in the central South Island is renowned for its beauty and clarity and now there are moves afoot to protect that view by creating the world's first.
There's no doubt about it, the Mt John Observatory near Tekapo is star quality.
"The night sky above us is totally unique in the world...it's clear, it's un-cluttered, there's no light pollution at the moment and it's an asset we have to strive to protect," says local businessman Graeme Murray.
And keeping those skies clear means keeping lights to a minimum.
"In the northern hemisphere they've left it too late ... in most centres in Europe and across North America you can't see the stars like we can here," says Murray.
But Tekapo is expanding quickly. Council already encourages the use of lights that point down, and the plan now is to make the sky a world heritage park to protect it even more.
"Obviously local councils - the North Otago and McKenzie District Council - have to accept that this is a good thing for their districts and I'm convinced that it is," says Phil Butler from the Canterbury University Department of Physics.
Good because more and more tourists are coming to Tekapo to enjoy the night sky. The heritage park will ensure the observatory remains world class, which in turn helps the town. Locals hope UNESCO will approve the park in time for astronomy year in 2008.
Cambridge, MA--For the first time, amateur and professional astronomers have teamed up to discover a new planet circling a distant star. The planet was detected by looking for the effect of its gravitational field on light from a more distant star, a technique known as microlensing. It is only the second world to be discovered using the microlensing technique. Gravitational microlensing offers the potential for detecting Earth-mass planets using existing or near-future technologies.
"This discovery is the tip of the iceberg for microlensing searches," said astronomer Scott Gaudi (Harvard-Smithsonian Center for Astrophysics). "With improving technologies and techniques, the first Earth-sized planet may be found by microlensing."
"If an Earth-mass planet was in the same position [as the planet we found], we would have been able to detect it," agreed professor Andrew Gould (Ohio State University), a member of the team who made the discovery.
Microlensing searches scored their first discovery only last year. This second find confirms the power of this planet-hunting technique and heralds the beginning of routine planet detection by microlensing.
"This is the beginning of the age of microlensing. We expect many more discoveries in the coming years," said Gaudi.
The newfound planet weighs approximately 3 times as much as Jupiter and probably orbits a star similar to the sun. At the time of its discovery, it was located about 3 times the earth-sun distance from its host star. Although its orbit is uncertain, the possibility of a "hot Jupiter" that revolves very close to its star was ruled out.
Both the planet and its star are located about 15,000 light-years from the earth, making this world one of the most distant ever discovered. Gravitational microlensing offers unique advantages for astronomers hunting planets: not only can it find more distant worlds than more common techniques such as the radial velocity, or "wobble," method, but microlensing also is more sensitive to smaller worlds.
"Even the signal from an earth-mass planet can be relatively large - tens of percent, which is very detectable," said Gaudi.
Gaudi played a key role in confirming the new planet. Although a microlensing event can last days, the presence of a planet will affect the signal for only a day or so. Therefore, data must be analyzed as quickly as it is gathered to identify the events that merit close watching.
"I was in Korea when we saw that this event was doing something strange and different," said Gaudi. "When I first looked at the deviation, I thought it looked like a planet. As soon as I got home to Cambridge, I downloaded the data and worked on it for 12 hours straight to analyze it. I figured out that there was no other explanation. It had to be a planet."
Detecting the planet's signal required obtaining data from many observatories around the world so that the microlensing event could be monitored around-the-clock. Gaudi is a member of the Microlensing Follow Up Network (MicroFUN), which is headed by Gould.
"There was an old saying that the sun never set on the British Empire. You could say that the sun never rises on our collaboration!" said Gaudi.
Two New Zealand amateur astronomers belong to the MicroFUN collaboration - Grant Christie of Auckland, who used a 14-inch-diameter telescope, and Jennie McCormick of Pakuranga, who used a 10-inch telescope. Data from both telescopes proved crucial in detecting the planet, and both observers share co-authorship on the paper announcing the find.
"These amateur astronomers work all day, then go home and observe all night," said Gaudi. "Their contribution is a testament to how far amateur astronomers have come. It speaks highly of their dedication to the field."
The microlensing event was detected and monitored extensively by the Optical Gravitational Lensing Experiment, or OGLE, headed by Andrzej Udalski of Warsaw University. Two other collaborations-the Probing Lensing Anomalies NETwork (PLANET) and Microlensing Observations in Astrophysics (MOA) - also followed the event and contributed to the journal paper.
Gravitational microlensing occurs when a massive object in space, like a star or even a black hole, crosses in front of a star shining in the background. The object's strong gravitational pull bends the light rays from the more distant star and magnifies them like a lens. On earth, observers see the star get brighter as the lens crosses in front of it, and then fade as the lens gets farther away. The presence of a planet orbiting the nearby star will modify this otherwise smooth process in a predictable way.