Observatories Archives

December 2, 2009December 24, 2015 by Nancy Atkinson

Exploring to the Beat of Pulsars

PULSE@Parkes project. Credit: Andrew Crosling

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An innovative project that provides high school students in Australia the opportunity to work with the famous Parkes radio telescope will soon make the data available to schools around the world. The PULSE@Parkes project allows for hands-on remote observing of pulsars producing real-time data, which then becomes part of a growing database used by professional astronomers. “Students can help monitor pulsars and identify unusual ones or detect sudden glitches in their rotation,” said Rob Hollow from the Australia Telescope National Facility, and coordinator for the PULSE@Parkes project. “They can also help determine the distance to existing pulsars.”

Initially, the project was only available to schools in Australia, but PULSE@Parkes hopes to expand globally, allowing students to collaborate on monitoring pulsar data. The first international session will be held on Dec. 7, 2009 at Cardiff University in the UK.

“We had the challenge to develop and implement simulation radio astronomy activities for high school students, providing the opportunity for them to actually use a radio telescope facility and engage with professional scientists,” said Hollow, speaking at the .Astronomy (dot Astronomy) conference this week in Leiden, The Netherlands. “We also wanted to have students doing science that is appropriate for them and useful for professional astronomers.”

Students in Sydney controlling the Parkes radio telescope. Credit: R. Hollow, CSIRO

Hollow said that even though radio astronomy data consists of squiggly lines, students are still engaged by the results, even without the pretty pictures produced by other astronomical instruments. “It works surprisingly well, and the visuals haven’t been as big an issue and we thought,” Hollow said. “But in looking at pulsars, the students do get the pulse profiles and they get immediate feedback.”

Plus, when the dish actually moves in response to the students’ inputs, they really become engaged. “There’s a real ‘wow’ factor in being able to control the telescope,” Hollow said. “The students pick it up quickly, and they really like that they are contributing to science.”

Recently, the first science paper was published using results obtained by students.

The program is done remotely, and students view webcams of the telescope and control room. They control the telescope directly via the internet, monitor the data in real time, and use Skype to communicate with astronomers at Parkes.

So far, Hollow said, they have done 25 sessions, with 28 schools, working with about 450 students. “This project is not just for gift and talented students,” he said, “and any school can apply.”

The Parkes Radio Telescope. Credit: R. Hollow, CSIRO — The Parkes Radio Antenna. Credit: R. Hollow, CSIRO

Parkes is a 64 m diameter radio antenna that was built in 1961. Hollow said the dish has received regular updates and is still on the cutting edge of science. Most famously, Parkes was to receive video from the Apollo mission to the Moon.

Hollow said he sees PULSE@Parkes as just the beginning of working with students. The Australian Square Kilometre Array Pathfinder (ASKAP) will be coming online in just a couple of years, with thirty-six 12-meter dishes. “This will provide for very fast surveys that will increase the area of coverage and increase the capability for sensitivity,” Hollow said. “From ASKAP, we’ll be getting massive data sets, which will provide more opportunity for student and public involvement.

For more information, including an audio of what a pulsar “sounds” like, as well as info for schools and teachers, requirements, and how to apply visit the PULSE@Parkes website

November 17, 2009December 24, 2015 by Nancy Atkinson

ALMA Telescope Makes First Observations

The ALMA telescope located high in the Chilean Andes made its first measurements on Tuesday using just two of the eventual 66 antennas that will comprise the array. The Atacama Large Millimeter/submillimeter Array took interferometric measurements of radio signals, or “fringes,” from a distant quasar (3C454.3) at sub-millimeter wavelengths. Astronomers said the data from the two 12-meter antennas provided unprecedented sensitivity and resolution, and observations at a wavelength of less than 1mm showed ALMA was now truly a “submillimeter” as well as millimeter-wave telescope.

ALMA is the largest, most ambitious ground-based observatory ever created, with completion slated for 2012. When all 66 antennas are working in synch, researchers believe ALMA will revolutionize the way we see the universe, probing deep into some of the first galaxies to form after the Big Bang and observing planets in mid-formation around young stars.

Interferometry involves linking together arrays of smaller telescopes to make measurements of an object. Sophisticated electronic systems will correlating the signals.

The next step in the process will be the addition of a third antenna which will allow the Alma team to obtain “phase closure.” This is an important capability which requires at least three antennas to cancel out errors in the “phase” of the signals caused by the instruments themselves and by the Earth’s atmosphere.

Here’s a video overview of ALMA:

Source: BBC

November 17, 2009December 24, 2015 by Nancy Atkinson

Astronomers Find Type Ia Supernova Just Waiting to Happen

Type Ia supernovae are a mystery because no one can predict when or where one might occur. But astronomers are hedging their bets on V445 Puppis. A so-called “vampire white dwarf” that underwent a nova outburst after gulping down part of its companion’s matter in 2000, now, it appears this double star system is a prime candidate for exploding. “Whether V445 Puppis will eventually explode as a supernova, or if the current nova outburst has pre-empted that pathway by ejecting too much matter back into space is still unclear,” said Patrick Woudt, from the University of Cape Town and lead author of the paper reporting the results. “But we have here a pretty good suspect for a future Type Ia supernova!”

This is the first, and so far only nova showing no evidence at all for hydrogen, and provides the first evidence for an outburst on the surface of a white dwarf dominated by helium. “This is critical, as we know that Type Ia supernovae lack hydrogen,” said Danny Steeghs, from the University of Warwick, UK, “and the companion star in V445 Pup fits this nicely by also lacking hydrogen, instead dumping mainly helium gas onto the white dwarf.”

Click here to watch a movie of the expanding shell of V445 Puppis.

The astronomers have determined the system is about 25,000 light-years from the Sun, and it has an intrinsic brightness of over 10,000 times our Sun. This implies that the vampire white dwarf in this system has a high mass that is near its fatal limit and is still simultaneously being fed by its companion at a high rate.

“One of the major problems in modern astrophysics is the fact that we still do not know exactly what kinds of stellar system explode as a Type Ia supernova,” said Woudt, “As these supernovae play a crucial role in showing that the Universe’s expansion is currently accelerating, pushed by a mysterious dark energy, it is rather embarrassing.”

Shell around V445 Puppis (March 2005). Credit: ESO

Woudt and his team used the ESO’s Very Large Telescope (VLT) to obtain very sharp images of V445 Puppis over a time span of two years. The images show a bipolar shell, initially with a very narrow waist, with lobes on each side. Two knots are also seen at both the extreme ends of the shell, which appear to move at about 30 million kilometers per hour. The shell — unlike any previously observed for a nova — is itself moving at about 24 million kilometers per hour. A thick disc of dust, which must have been produced during the last outburst, obscures the two central stars.

As Steeghs said, one defining characteristic of Type Ia supernovae is the lack of hydrogen in their spectrum. Yet hydrogen is the most common chemical element in the Universe. Such supernovae most likely arise in systems composed of two stars, one of them being the end product of the life of sun-like stars, or white dwarfs. When such white dwarfs, acting as stellar vampires that suck matter from their companion, become heavier than a given limit, they become unstable and explode.

The build-up is not a simple process. As the white dwarf cannibalizes its prey, matter accumulates on its surface. If this layer becomes too dense, it becomes unstable and erupts as a nova. These controlled, mini-explosions eject part of the accumulated matter back into space. The crucial question is thus to know whether the white dwarf can manage to gain weight despite the outburst, that is, if some of the matter taken from the companion stays on the white dwarf, so that it will eventually become heavy enough to explode as a supernova.

Read the team’s paper.

Source: ESO

November 16, 2009December 24, 2015 by Nicholos Wethington

35 Radio Observatories Link to Break Record

Ever wondered what the largest telescope on the Earth is? Well, this coming Wednesday and Thursday of this week, the largest telescope ever assembled here will take observations for a whole day. How big is the telescope? About the size of the whole Earth! 35 radio telescopes on 7 continents will link together for one whole day in an effort to observe distant quasars as part of an initiative to improve the reference frame that scientists use to measure positions in the sky.

Radio telescopes in Asia, Australia, Europe, North America, South America, Antarctica, and in the Pacific will all be linked together to measure the same 243 quasars over a 24-hour period. Quasars are galaxies that have a supermassive black hole at the center, which has strong emissions in the radio spectrum. The quasars being monitored are so far away from the Earth that they appear to be motionless in the sky. This makes them a perfect candidate for setting up a grid in the sky to use as a frame of reference, against which the positions of other objects can be determined.

This monitoring session comes out of a meeting of the International Astronomical Union in August, during which it was decided to start using a set of 295 quasars as a celestial reference frame starting January 1st, 2010. This is not a new reference frame to be used by astronomers – the current one was adopted in 1998 – but an important update to the existing reference frame, the International Celestial Reference Frame.

The session, called the Very Large Astrometry Session is coordinated by the International VLBI Service for Geodesy and Astrometry. Several of the participating observatories will have live webcams running during the event (check for the observatory in your language!), and a public outreach page on the event, hosted by the Bordeaux Observatory, can be found here. The public outreach page will post images as they are taken during the session, with information about observation coordinates.

Radio telescopes like the Very Long Base Array in the United States already link together observatories that are far apart to take observations. This technique is called very long baseline radio interferometry (VLBI), and allows for the use of smaller telescopes that are distant from one another to be linked together and have the same angular resolution as if they were one larger telescope. Doing these observations all in one go will reduce some of the errors that occur when disparate observatories take images at different times.

The previous record for radio observatories linked together to create a larger telescope for one monitoring session is 23. That means that this observing session will beat that record by a whopping 12 additional observatories. Even with this unprecedented amount of observatories monitoring the quasars, there will be a few gaps in the sky, mostly in the Southern hemisphere. Only 243 of the total 295 quasars in the reference frame will be observed this week, though that will break another record for the amount of objects observed in one session using this method. The image below depicts the locations of the participating observatories.

By taking data on the 243 selected quasars, astronomers will be able to more accurately pinpoint objects in the sky in all wavelengths, and gather more precise data. For instance, many objects of scientific interest are monitored by separate telescopes operating in the visible, radio, x-ray and infrared wavelengths. Having a more accurate frame of reference to tell these different telescopes where to point in the sky will improve the ability of the different telescopes to gather information from the same place in space.

Source: NRAO, IVS

October 13, 2009March 24, 2012 by Nancy Atkinson

A Very Large 3-D Movie

Quick! Grab a pair of red and green 3-D glasses and slap them on to watch this great time lapse video of the Very Large Telescope at the Paranal Observatory, high in the Atacama Desert in Chile. It shows a complete night at the observatory, and you can see the four 8m telescopes and the four 1.8m telescopes of the VLT working, all in 3-D. The video comes from the handiwork of astrophotographer and head Optics Engineer on the VLT, Stéphane Guisard. If that name sounds familiar, Stéphane has recently been working with ESO and fellow astrophotographer Serge Brunier on the GigaGalaxy Zoom project. Click this link to go directly to GigaGalaxy Zoom, or read one of our previous articles about them here. It was made by using two cameras taking pictures simultaneously, which were combined to create an anaglyph time lapse movie. Two notes about the movie: the telescopes and domes were lit by the moonlight, and the International Space Station crosses the sky during the very first seconds of the movie.
Continue reading “A Very Large 3-D Movie”

September 24, 2009April 26, 2016 by Tammy Plotner

Sky Scouting Out Astronomy Fun!

What happens when you mix a large group of kids with a telescope that talks? Chances are, you’ve got a recipe for loads of astronomy fun. Thanks to a generous donation of a Celestron SkyScout 90 telescope and more, the Outreach Team at Warren Rupp Observatory soon found out what it was like to take on more than 300 guests during a recent public night and just how valuable certain pieces of astronomy education equipment can be. Come on inside where it’s dark and let me show you what we’ve found…

Since the introduction of the Celestron SkyScout Personal Planetarium, amateur astronomers the world over have been delighting in its simple, easy to use format and ability to instantly identify and/or locate any celestial object visible to the unaided eye, providing educational and entertaining information, both in text and audio. Many times when you encounter a large group of people, you’ll find there are some that are just a bit too shy to ask questions, but desperately would like to explore… And handing them a Celestron SkyScout opened up a whole new world to them. But what exactly would happen if you gave them the equally easy ability to see the objects they had found with a telescope? That’s where the Celestron SkyScout Scope 90 came into play and opened up the wonders of the Comos…

Like all non-profit educational organizations, the Observatory simply couldn’t afford new equipment. We never charge for attending public nights – nor do we charge for giving educational programs. As a result? Well, we might always be broke… But that hasn’t stopped us from continuously being #5 in the NASA Night Sky Network Outreach standings and serving thousands of children and adults the very best in educational programming and sharing the night sky. And even as quiet as we try to be in the dark, sometimes our voice gets heard! Just like Celestron heard about UT reader Brian Sheen’s Outreach Expedition in “Canoe Africa” and donated equipment, so our need was also heard and OPT Telescope stepped forward with an equally astounding donation…

With just a few gentle lessons from one of our Outreach Team Members, Bob Kocar, it wasn’t long until the kids soon took over our new Celestron SkyScout Scope 90. The easy to use alt-azimuth mount and tripod allows users of any age to move easily around the sky, but that wasn’t the only treat they had in store! Along with our donation package from OPT came the incredible blessing of the Celestron SkyScout Speakers. This amazing little device only took a few minutes to charge via a USB port and delivered big, big sound to anyone within the waiting circle around the scope! Now, while one child aimed the scope, another could produce the “program” to go along with it! Story after story played, but sky scouting out the astronomy fun didn’t stop there…

With an easy to use telescope, a personal planetarium that worked like their familiar iPods, and a sky full of stars… What more could a huge group of kids and adults ask for? That’s right. More. And OPT had delivered more in the form of the Celestron Sky Scout Expansion Card – International Year of Astronomy. The next thing you know, we were hearing about all the celestial events that would be taking place this month, information on the International Year of Astronomy and highlights of important milestones in astronomy and space history. After a few bright Messier objects, a young man held up two more he had found in our box of astronomy toys and the crowd around the telescope soon grew larger as they explored the Celestron Sky Scout Expansion Card – Astronomy For Beginners and Celestron Sky Scout Expansion Card – All About The Stars.

Does adding a dimension like the Celestron SkyScout Scope 90, the Celestron SkyScout, speakers and expansion cards really have an impact on both personal and public astronomy? You can see the results for yourself, but what you can’t see is the most important of all. For those of us who practice astronomy, we often tease that we never know a face – but we know the voice in the dark. That night the voices in the dark were busy talking about star colors and names, pointing out constellations to each other and talking about distances and facts like young Carl Sagans. For some folks, this type of equipment might not seem right – a recorded voice taking place of a live astronomer – a telescope that utilizes GPS technology and point and shoot simplicity… But for a huge group of kids who embrace new technology?

It was a night of Sky Scouting out astronomy fun!

Our many thanks go once again to Mr. Craig Weatherwax of Oceanside Photo and Telescope for your generous donation to Warren Rupp Observatory and your continued support of our UT readers. It means so very much to all of us…

September 1, 2009April 26, 2016 by Nancy Atkinson

Satellite Images of California Wildfires, Mt. Wilson Update

NASA's Aqua Satellite MODIS Instrument view of the California wildfires. Credit: NAS

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The wildfires near Los Angeles have spread to over 100,000 acres. The Los Angeles Times reported that the fire had burned 74 structures and remained out of control, spreading both west and north. As of 6:30 p.m. Pacific Daylight Time on August 31, some 12,000 homes were threatened. Fire fighters struggled to save the Mt. Wilson Observatory from the encroaching fire. Today, fire fighters set controlled backfires in effort to remove the closest vegetation to the various telescope structures. See below for a labeled image of the structures on Mt. Wilson amid smoke from the fires, courtesy of Emily Lakdawalla of the Planetary Society, along with more satellite, ground and helicopter images from the fires.

Mt. Wilson with labeled names of scopes. Courtesy of Emily Lakdawalla

Imagery from Mt. Wilson’s tower camera, recently went offline, likely due to loss of power. They have a back up site, available here, and staff from the observatory are still posting updates. While it was alarming to see the observatory structures surround and sometimes not visible because of smoke, the Mt. Wilson staff assured that they structures were still safe, and the fires were planned:

The [fire fighter’s] plan, which they would have implemented earlier had they not been withdrawn, was to start these groundlevel fire and literally walk along with them to keep them controlled. This is why we see no flames. The fires will consume the accumulation of needles from the many pine and fir trees as well as other scrub growth that could flame up and ignite lower limbs that would them permit the blossoming of the entire tree into flames. All the smoke we see is entirely consistent with this procedure. Larry and Dave are both delighted to see what’s going on, but I’ve got to say that seeing smoke next to those domes is very unsettling to me. Still, I know what the fire fighters are now doing is necessary to save the Observatory.

The latest news is that 4 acres of water is going to be dropped on the north side of Mt.W towers on Tuesday afternoon in an effort to save the observatory and communications towers.

A live view from a helicopter from station KTLA is available here. UPDATE: That feed is cutting out frequently due to demand. Try this one instead. (It is from a Fox station from anyone who thinks I have something against Fox….)

View this link to see a map of where the fire has spread. It is a Google map that is updated frequently.

The Los Angeles times blog reports that the “Station” fire, as it is called, in Angeles National Forest has been creeping east, toward the center of the San Gabriel Mountains. But its growth has been slower in the last 24 hours than it was over the weekend, thanks to higher humidity.

The fire’s maximum borders are roughly 25 miles from west to east and 18 miles north to south, covering the entire length of Angeles National Forest.

This image from NASA’s GOES-O satellite shows how far the smoke from the fires has spread.

GOES O image of smoke from the California fires, reaching nearly across Nevada. Credit: NASA

Image from NASA's Terra Satellite, taken August 30, 2009. Credit: NASA

This image was acquired mid-morning on Aug. 30 by the backward (northward)-viewing camera of the Multi-angle Imaging SpectroRadiometer (MISR) instrument on NASA’s Terra satellite. The image is shown in an approximate perspective view at an angle of 46 degrees off of vertical. The area covered by the image is 245 kilometers (152 miles) wide. Several pyrocumulus clouds, created by the Station Fire, are visible above the smoke plumes rising from the San Gabriel Mountains north of Los Angeles in the left-center of the image. Smoke from the Station fire is seen covering the interior valleys along the south side of the San Gabriel Mountains, along with parts of the City of Los Angeles and Orange County, and can be seen drifting for hundreds of kilometers to the east over the Mojave Desert.

This striking time-lapse video of the fires at sunset, taken on August 29 from Mulhulland Drive in Los Angeles, show the fires spreading.

Sources: Mt. Wilson observatory website fire update, Los Angeles Times, New York Times, NASA Earth Observatory

August 31, 2009December 24, 2015 by Brian Ventrudo

Astronomers Find World’s Best Observing Site

Image of the Chinese Kunlun base, near "Ridge A"

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The search for the best observatory site in the world has lead to the discovery of what is thought to be the coldest, driest, calmest place on Earth. No human is thought to have ever been there, but it’s expected to yield images of the heavens three times sharper than any ever taken from the ground.

The joint US-Australian research team combined data from satellites, ground stations and climate models to assess the many factors that affect the quality of an observing site – cloud cover, temperature, sky-brightness, water vapour, wind speeds and atmospheric turbulence.

The researchers pinpointed a site on an Antarctic plateau with the prosaic name “Ridge A”. At an elevation of 4,053 m, the ridge is not only remote but extremely cold and dry. The study revealed that Ridge A has an average winter temperature of -70 °C, and that the water content of the entire atmosphere in a vertical column above the ridge is equivalent to a layer of liquid water less than the thickness of a human hair.

The ridge is also extremely calm, which means that there is very little of the atmospheric turbulence elsewhere that makes stars appear to twinkle. “It’s so calm that there’s almost no wind or weather there at all,” says Dr. Will Saunders of the Anglo-Australian Observatory and visiting professor to the University of New South Wales, who led the study.

“The astronomical images taken at Ridge A should be at least three times sharper than at the best sites currently used by astronomers,” says Dr. Saunders. “Because the sky there is so much darker and drier, it means that a modestly-sized telescope there would be as powerful as the largest telescopes anywhere else on earth.”

They found that the best place in almost all respects was not the highest point on the Plateau – called Dome A – but 150km away along a flat ridge.

“Ridge A looks to be significantly better than elsewhere on the Antarctic plateau and far superior to the best existing observatories on high mountain tops in Hawaii and Chile,” says Dr. Saunders.

Ridge A is located within the Australian Antarctic Territory (81.5 °S 73.5 ºE), the site is 144km from an international robotic observatory and the proposed new Chinese ‘Kunlun’ base at Dome A (80.37 °S 77.53 °E).

Interest in Antarctica as a site for astronomical and space observatories has accelerated since 2004 when astronomers published a paper in the journal Nature confirming that a ground-based telescope at Dome C, another Antarctic plateau site, could take images nearly as good as those from the space-based Hubble telescope. A detailed study by the Anglo-Australian Observatory suggests the cost of building and running the 2.5 m telescope PILOT optical/infrared telescope at Dome C would be US$8.5 million.

The finding is published today in the Publications of the Astronomical Society of the Pacific.

Source: University of New South Wales

July 10, 2009December 24, 2015 by Nancy Atkinson

Herschel Telescope First Light Images Released

SPIRE images of galaxy M74 at three different infrared wavelengths. Credits: ESA and the SPIRE Consortium

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The Herschel telescope has now turned on all its instruments, taking a few “first light” images with each instrument of galaxies, star-forming regions and dying stars. Herschel astronomers said they were “staggered” by the results, saying “these observations show that Herschel’s instruments are working beyond expectations. They promise a mission of rich discoveries for waiting astronomers.” Above are images taken with Herschel’s Spectral and Photometric Imaging Receiver (SPIRE, of two galaxies, M66 and M74. The galaxies showed up prominently, providing astronomers with their best images yet at these wavelengths. And what’s that in the background? Other more distant galaxies!

Here are three images of M74 taken in three different wavelengths, and of special note is the image taken at 250 microns. This is longer than any previous infrared space observatory. Herschel’s primary mirror is 3.5 m in diameter, nearly four times larger than any previous infrared space telescope. So, expect more dazzling imagery and science to come.

Water in Cygnus

DR21 from the HIFI instrument. Credits: ESA and the HIFI Consortium

Scientists used Herschel’s Heterodyne Instrument for the Far-Infrared (HIFI) to look for warm molecular gas heated by newborn massive stars in the DR21 star-forming region in Cygnus. They were able to observe ionized carbon, carbon monoxide, and water in this region.

HIFI provided excellent data in two different observing modes, returning information on the composition of the region with unprecedented accuracy and resolution. It works by ‘zooming in’ on specific wavelengths, revealing different spectral ‘lines’ that represent the fingerprints of atoms and molecules and even the physical conditions of the object observed. This makes it a powerful tool to study the role of gas and dust in the formation of stars and planets and the evolution of galaxies.

PACS stares into the Cat’s Eye

This panel shows an overlay of individual spectra of the nitrogen line, all taken simultaneously with the PACS spectrometer, on the dust continuum as observed with the PACS photometer. Credits: ESA and the PACS Consortium

The first observation with the Photodetector Array Camera and Spectrometer (PACS) instrument shows the Cat’s Eye Nebula; a complex shell of gas thrown off by a dying star. Dying stars create spectacular nebulae, enriching the interstellar medium with heavy chemical elements. But how does an initially spherical star produce such a complex nebula? Further observations with PACS should help answer questions like that. This instrument makes it possible, for the first time, to take images in spectral lines and see how the wind from the star shapes the nebula in three dimensions.
PACS observed the nebula in two spectral lines from ionized nitrogen and oxygen. It also obtained a small map of the Cat’s Eye Nebula in the 70 micron band, revealing the structure of a dust ring with an opening on one side.

The Herschel instruments will now be tested and calibrated, and the official mission should start around the end of November. “These images demonstrate that there is a lot of science to look forward to,” the scientists said.

Sources: ESA, Herschel Twitter

May 27, 2009December 24, 2015 by Nancy Atkinson

A Top-Secret Explosion in M82

M82. The VLA image (top left) clearly shows the supernova (SN 2008iz). Credit: MPIfR

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Supernovae are extremely luminous explosions of stars and cause bursts of radiation that often outshine an entire galaxy. So, when a supernova exploded last year in a nearby galaxy, why didn’t we see it? Was this an undercover supernova; a top-secret, covert event? Well, kind of. The secret is in the dust.

M82 is an irregular galaxy in a nearby galaxy group located 12 million lightyears from Earth. Despite being smaller than the Milky Way, it harbors a vigorous central starburst in the inner few hundred lightyears. In this stellar factory more stars are presently born than in the entire Milky Way. M82 is often called an ‘exploding galaxy’, because it looks as if being torn apart in optical and infrared images as the result of numerous supernova explosions from massive stars. Many remnants from previous supernovae are seen on radio images of M82 and a new supernova explosion was long overdue. For a quarter of century astronomers kept an eye on M82, hoping to catch a supernova in the act, but with no luck. Astronomers were starting to wonder why the galaxy has been so silent in recent years.

However, a recent explosion actually did occur in M82, and it was the closest supernova in the last five years. But the explosion was shrouded by gas and dust, leaving it invisible to our human eyes, and visible only in radio wavelengths. Astronomers say without the obscuration, this explosion would have been visible even with medium-sized amateur telescopes.

On April 9, 2009, Dr. Andreas Brunthaler from the Max Planck Institute for Radio Astronomy noticed something unusual in the data of M82 taken just the previous day with the Very Large Array (VLA) of the National Radio Astronomy Observatory in New Mexico, USA. “I then looked back into older data we had from March and May last year, and there it was as well, outshining the entire galaxy!” he said. Observations taken before 2008 showed neither pronounced radio nor X-ray emission at the position of this supernova.

On the other hand, observations of M82 taken last year with optical telescopes to search for new supernovae showed no signs of this explosion. Furthermore, the supernova is hidden on ultraviolet and X-ray images. The supernova exploded close to the center of the galaxy in a very dense interstellar environment.
Astronomers began to realize they had perhaps found the clue to the mystery about the long silence of M82. Actually, it hasn’t been silent and perhaps many supernova events have occurred, and are something like “underground explosions”, where the bright flash of light is covered under huge clouds of gas and dust and only radio waves can penetrate this dense material. “This cosmic catastrophe shows that using our radio telescopes we have a front-row seat to observe the otherwise hidden universe”, said Prof. Heino Falcke from Radboud University.

Radio emission can be detected only from core collapse supernovae, where the core of a massive star collapses and produces a black hole or a neutron star. It is produced when the shock wave of the explosion propagates into dense material surrounding the star, usually material that was shed from the massive progenitor star before it exploded.

By combining data from the ten telescopes of the Very Long Baseline Array (VLBA), the VLA, the Green Bank Telescope in the USA, and the Effelsberg 100m telescope in Germany, using the technique of Very Long Baseline Interferometry (VLBI), the team was able to produce images that show a ring-like structure expanding at more than 40 million km/h or 4% of the speed of light, typical for supernovae. “By extrapolating this expansion back in time, we can estimate the explosion date. Our current data indicate that the star exploded in late January or early February 2008,” said Brunthaler.

Only three months after the explosion, the ring was already 650 times larger than Earth’s orbit around the Sun. It takes the extremely sharp view of VLBI observations to resolve this structure which is as large as a 1 Euro coin seen from a distance of 13.000 km.

The asymmetric appearance of the supernova on the VLBI images indicates also that either the explosion was highly asymmetric or the surrounding material unevenly distributed. “Using the super sharp vision of VLBI we can follow the supernova expanding into the dense interstellar medium of M82 over the coming years and gain more insight on it and the explosion itself,” said Prof. Karl Menten, director at the MPIfR.

Discoveries like this supernova will be routine with the next generation of radio telescopes, such as the Low Frequency Array (LOFAR) which is currently under construction in Europe, the Allen Telescope Array (ATA) in the USA, or the planned Square Kilometer Array (SKA). These will have the capability to observe large parts of the sky continuously.

Lead image description: Zooming into the center of the galaxy M82, one of the nearest starburst galaxies at a distance of only 12 Million light years. The left image, taken with the Hubble Space Telescope (HST), shows the body of the galaxy in blue and hydrogen gas breaking out from the central starburst in red. The VLA image (top left) clearly shows the supernova (SN 2008iz), taken in May 2008. The high-resolution VLBI images (lower right) shows an expanding shell at the scale of a few light days and proves the transient source as the result of a supernova explosion in M82.
Graphics: Milde Science Communication, HST Image: /NASA, ESA, and The Hubble Heritage Team (STScI/AURA); Radio Images: A. Brunthaler, MPIfR. (Click image for higher resolution).

Read the team’s paper here.

Source: Max Planck Institute for Radio Astronomy