Megan's Blog

In the news this Spring...

In the news this Spring:

• Supernova 1987A three years on;
• the Sudbury Neutrino Observatory gets final approval;
• ESO to begin a major new survey of the northern sky.
  

The 24th February marked the three year anniversary of the supernova 1987A and it continues to evolve as the ejecta expand into the interstellar medium of the surrounding Tarantula Nebula. At a distance of just 168,000 light years, it is the closest supernova since the invention of the telescope (almost 400 years ago) and presents an ideal opportunity to observe the evolution of a remnant as it expands. Since the peak optical brightness was reached in the second half of 1987, the brightness has been decreasing exponentially as the supernova fades. But in an IAU circular, published on December 29th last year, astronomers at the European Southern Observatory present results which show that the decline in the light curve has levelled off. Indications that this were happening had already been observed, but the evidence is now clearer and the results confirmed. The data suggest that a previously undetected energy source is contributing to the total energy output, and the researchers argue that the most likely source is radiation from an as-yet undetected pulsar, absorbed and re-radiated by the dust in the nebula.

As well as optical light and gamma rays, the explosion of supernova 1987A also generated a massive burst of neutrinos. These particles were picked up by a detector at Kamioka in Japan and another located underneath Lake Erie in the USA. Detecting neutrinos is not so easy since they only interact very weakly with other matter. These two detectors both consist of a large tank of water surrounded by photomultiplier tubes that detect the faint light generated when a neutrino interacts with a proton in the water. The larger the tank, the more protons you have, and the more chance you have of an interaction. In January this year, a project to construct a new neutrino detector in Canada was given final approval. The Sudbury Neutrino Observatory will cost fifty two million dollars to construct and will consist of a tank containing 1000 tonnes of heavy water surrounded by two thousand photomultiplier tubes, buried more than a mile underground. Scheduled to be completed within five years, the Sudbury Neutrino Observatory will investigate neutrino emissions from the Sun, investigating why current experiments have only detected one third of the expected number.

On January 26th, the European Southern Observatory announced a collaboration with Palomar Observatory which will produce the first new astronomical atlas of the northern sky in over three decades. The observations will be carried out using the refurbished 48-inch telescope at Mount Palomar and will result in a collection of 2,682 photographic plates showing stars up to seven times fainter than the existing Palomar sky survey. Taking ten years to produce and scheduled to be complete by the year 2000, a full set of glass copies (of which fewer than ten will be produced) will cost DM 460,000 (roughly $270,000) while a full set of film copies will cost a mere DM 60,000.

And finally: The next few years are looking exciting for both planetary exploration and space-based astronomy with several new missions launched recently. The Galileo spacecraft was launched on October 18th last year onboard the space shuttle Atlantis and is now on its way to Jupiter where it will study the planet and its moons, as well as sending a probe plunging into the thick atmosphere of the solar system's largest planet. One month later, the Cosmic Microwave Background Explorer, COBE, was launched aboard a Delta rocket from the Vandenberg Air Force Base in California, with the aim of mapping the faint radiation left over from the Big Bang. This year should also see the launch of the Hubble Space Telescope, one of the most eagerly anticipated space-based observatories. Following many delays, Hubble is scheduled for launch on board the space shuttle during March.

With huge thanks to the Nature archives!

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This blog post is a news story from the Jodcast, aired in the Spring 1990 edition.