Posts Tagged ‘Radio Telescopes’

Two ‘Super Earths’ Discovered around Nearby Star, Tau Ceti

August 10, 2017

Today’s I newspaper, for Thursday 10th August, has the news that two planets, which may be suitable for human colonization, have been found around Tau Ceti, a nearby star similar to our Sun.

The paper says on page 2

Astronomers have discovered two potentially habitable “super-Earths” orbiting a star 12 light years away. British led experts have identified four rocky planets, similar in size to Earth, in Tau Ceti’s “habitable zone” orbiting the nearest Sun-like solar system, neighbouring ours.

John Von Radowitz’s article, The Climate’s Nice 12 Light Years Away on page 5 also adds that the two ‘super-Earths’ are at the edge of Tau Ceti’s “habitable zone”, and that

British-led astronomers speculate that the system might be a potential candidate for future interstellar colonization. But there is evidence of a massive debris disc circling the star, increasing the chances of the planets being pounded by asteroids and comets.

Dr. Fabo Feng, the lead researcher from the university of Hertfordshire, said: “We’re getting tantalizingly close to observing the correct limits required for detecting Earth-like planets.

“Our detection…is a milestone in the search for Earth analogues and the understanding of the Earth’s habitability.”

The findings are to be published in ‘The Astronomical Journal’.

Philip’s Astronomy Encyclopedia (London: Philips’, 2002) states that Tau Ceti ‘is the most Sun-like of all the nearby single stars’. (‘Cetus’, p. 81), and that it is a G8-type star lying at a distance of 11.9 light years. This means its a yellow dwarf star like our Sun.

Tau Ceti is one of the stars making up the constellation Cetus, and is quite visible, unlike some of the other nearby stars, like Barnard’s Star. It’s so much like Sun that it was one of two stars, the other being Epsilon Eridani, which were the subject of Project Ozma in 1960. This was a program led by Frank Drake, using the 26 metre radio telescope at Green Bank to listen for possible signs of alien civilisations broadcasting messages along the 21 cm band. That wavelength was selected because it’s close to the wavelength occupied by the noise of cold hydrogen in space. Drake and his fellow scientists believed that it would therefore be a natural wavelength for advanced alien civilisations to use to broadcast to each other across the vast gulfs of space.

The search was, however, unsuccessful, and after a couple of months it was discontinued. Frank Drake still remains an influential figure in the Search for Extra-Terrestrial Intelligence (SETI) for his formulation of the Drake Equation, a formula which allows the number of possible alien civilisations in our Galaxy to be calculated.

The Equation has also come under attack. James E. Oberg, a NASA scientist, criticized it over thirty years ago in his article, ‘New Case Against Extraterrestrial Civilisations’ in the 1981 Yearbook of Astronomy. Part of the problem with the equation is that no-one actually knows how common Earthlike planets are, nor how likely the emergence of life is, and how like intelligent, technological life is either. According to the numbers selected, the Equation gives an answer for the number of alien civilisations in our Galaxy as anywhere from several to several million. I have a feeling Carl Sagan, one of the greatest advocates of the search for alien life, believed that there may have been around a thousand or so extraterrestrial civilisations out there in our Galaxy.

Astronomers have since found many tens, if not actually hundreds of extra-solar planets since then, some of which are rocky worlds like our own. This is very encouraging for SETI advocates and researchers, but later projects to search the sky using radio telescopes have still not found any conclusive evidence of alien intelligence.

As for missions to neighbouring stars, the costs of constructing a suitable spaceship that will get there in decades, rather than centuries or millennia, is immense. However, it has been estimated that the global economy should have grown sufficiently to make such a mission affordable by the 22nd Century A.D. Always supposing that Donald Trump and Kim Jong Un haven’t destroyed the world before then.

Jodrell Bank and Amateur Radio Telescopes

December 18, 2015

BBC 4 a few weeks ago broadcast a documentary on the history of Jodrell Bank, Britain’s pioneering radio telescope. Bernard Lovell, its founder and director, had been one of the scientists working on the development of radar during the War, and the radio telescope was originally built using parts left over from the project that were due to be scrapped. In the early days it was very much an ad hoc operation. The size of the telescope’s dish has the radius it has because that was the distance between the van holding its key components in the early days to the edge of the field. The programme covered the history of the telescope from its very beginnings to today. It described how the telescope came into its own in the late 1950s and 1960s when it was the only instrument that could independently verify the first Soviet space missions and their conquest of space. This also caused additional pressure on Lovell, as there was official demand for him to monitor space missions in the USSR, which detracted from his real interest in exploring the heavens through the radio signals sent out into space from stars, nebulae and galaxies.

The Russians also liked and admired Lovell, so much so that on scientific trip to the Soviet Union, the Russians showed him some of their highly top secret space installations, and hinted that he would be very welcome if he left Britain and joined them. Obviously the great man did not take up the offer. Eventually such pressure proved so great that he was off work suffering from depression, and even considered leaving science altogether. Lovell was a Methodist, and to the surprise of his children, at this point in his career he considered joining the clergy. He didn’t, but went back to charting the heavens.

Other highlights of the telescope’s fifty-odd year history was the discovery, by Jocelyn Bell-Purnell, of pulsars. These are neutron stars, small, highly compact stars at the end of their lives, which broadcast a signal into space. The stars are small, about 40 miles or so in diameter, and spin quickly, so it appears that the signal is being sent in pulses. They’re also regular, so that in the first few days when they were discovered one of the theories about them was that they were a signal deliberately sent out into space from an extraterrestrial civilisation. After more pulsars were discovered in the following days, the scientists were able to give the true explanation of their origins.

Since its heyday, much larger telescopes and arrays have been built. Jodrell Bank nevertheless still remains important, contributing valuable research in this area of astronomy.

Indeed. I remember a few years ago an edition of one of the Beeb’s astronomy programmes in which Dara O’Brien and Brian May were up there. O’Brien is a failed mathematician, having dropped out of a university maths course, while May is a properly accredited astrophysicist. He had, it’s true, a twenty-odd year gap in his career, due to performing with Queen, but he finally handed his thesis in a few years ago. It was duly marked, and he passed. This obviously makes him one of the most rock ‘n’ roll scientists ever. I think in the programme they were supposed to be looking for signals from alien civilisations. They didn’t find any, which probably surprised no one, given that scientists have been looking, off and on, for radio signals from aliens since the days of Project OZMA in the late ’60s and 70s. Despite NASA’s optimistic prediction in 1995 that in five years they would be discovered, no has as yet.

Patrick Moore, one of the greatest science communicators and popularisers, always maintained that astronomy was still one of the very few areas of science where amateurs using modest equipment could make a real contribution. I doubt that there are very many ordinary people outside the big observatories, who have an active interest in radio telescopy. Nevertheless, it is possible to build your own radio telescopes. There’s a piece by Trevor Hill, who was a science teacher at Taunton School in Somerset, about how he built a an array of radio telescopes in the book, Small Astronomical Observatories, edited by Patrick Moore (London: Springer 1986). He did so as part of an attempt to get the pupils interested in astronomy. Naturally, he started off by building a normal, optical observatory for a telescope. He turned to radio astronomy at the suggestion of one of the pupils after the normal astronomy session had been cancelled due to rain. The pupil pointed out that radio waves travel through clouds, and so observation wouldn’t be stopped by bad weather. His article in the book describes the radio telescopes he built. This includes a set of Ham radio aerials set up in an array to receive radio waves from solar flares.

Taunton School Radio Telescope

Trevor Hill’s Solar Flare Radio Telescope at Taunton School

He also provides a schematic of the telescope’s construction. As you can see from the photo, even as a small-scale amateur project it’s still very large. Nevertheless, he states that it was very cheap. With the exception of the computer, it cost about £200 in 1995. Which means it’s almost possible for every man or woman to become their own radio astronomer. Obviously, this was before the boom ended, and Cameron got in to hit everyone with massive debt and advancing poverty.

Here’s Tim O’Brien, professor of astrophysics at Manchester University and the radio telescope’s associate director, talking about the telescope on the 70s anniversary of its establishment. It’s great to hear him say that it remains at the cutting edge of research, and may be so for the next fifty years.