Voices from the Distant Stars – The Story of a Pulsar
In space no one can hear you scream, or can they? Actually, we hear a lot from space. We just need the right set of ears. And for a long time we have listened to the stars, and every once in a while, we hear something that might just be something special. A regular pattern that suggests an alien intelligence, or shadows on a sun suggesting a giant structure. Here are some of the great space oddities that have given us pause to reconsider our place in the Universe. One such ‘oddity’ is a Pulsar.
Voices of Little Green Men
In 1967, astrophysicist Jocelyn Bell Burnell was astonished to observe regular radio pulses of 1.33 seconds in the Vulpecula constellation. The Cambridge researchers were so taken with the idea that this was some sort of interstellar beacon, a voice from distant stars, that they nicknamed the mysterious source LGM-1; “little green men 1”. In fact, the radio bursts they were receiving came from the first pulsar which was given the much more cumbersome designation ‘PSR B1919+21’. So what is a pulsar, and why do they sound like aliens?
Pulsars are neutron stars, superdense structures which may only be a few miles in diameter but pack enough mass to rival our own sun. As a result of this amount of matter existing in such a compact space, some pretty strange things start to happen. For a start, the entire star is rapidly spinning (sometimes at hundreds of times per second). This combined with its two beams of energy produces its pulse as the spinning beams move in and out of view, like a lighthouse. And we see this information as regular ‘pulses’, enough to trick us into thinking a being is looking to talk to us. But how did we discover them?
Pulsars were discovered through interplanetary scintillation (IPS), a technique in radio astronomy, which was implemented in the sixties to scan the skies for quasars: large interstellar objects emitting vast amounts of energy across a variety of frequencies. As these signals pass through space, they encounter obstacles and diffract. This effect produces a characteristic twinkle, or scintillation which can be analysed and reveal the position of such objects as pulsars. The discovery would lead to the first Nobel Prize in physics to be given to an astronomer. So even though we didn’t find aliens, we learned a lot.
What we know about Pulsars
We now understand that neutron stars are the finished product of dead stars, when all that’s left has burnt out. The end of a star is a hostile environment; these neutron stars are incredibly hot, incredibly radioactive and as I said before, they are incredibly dense. The surface would be hard and smooth, though it is unlikely that any of us would be able to set foot on one. As the dying star collapses, its rotational speed increases. Imagine that you’re spinning on an office chair and you draw in your arms and legs. You speed up, so would the pulsar. The pulses which these star remnants emit are how we’ve discovered most neutron stars.
Since the initial discovery, we’ve found over two thousand pulsars. Merely collecting them isn’t their sole reason of interest. Recently we’ve been able to confirm the existence of another type of cosmic phenomenon; gravitational waves. As the universe expands, it does not does so uniformly. Ripples in space occur as part of this hodgepodge process as well as due to galaxies colliding. As these colossal clusters approach each other, the black holes in the centre release gravitational waves. Pulsars play a part in this, due to their regularity, which is altered by the distortion of merging black holes.
The Future of Pulsars
Pulsars were originally mistaken as the beacons or lighthouses of little green men. This is the reputation which history has afforded them, though that’s not to rule out their being put to a similar use in the future. Although pulsar signals do eventually slow down as they lose spin, this takes a long time and they are relatively stable points. Future deep space travellers will have the potential to navigate via triangulation of the pulsars in 3-D space.
Present space travellers are even able to do this. In 1972, the Pioneer 10 spacecraft was launched to explore Jupiter and beyond. In 1983 it left the solar system to enter deep space. Finally, in 2003 we lost its signal. As well as numerous scientific instruments on board, the spacecraft carried an engraving depicting humans, earth and the solar system. The latter featured as a sort of map, showing its location between the relative periods of 14 pulsars to enable any visitors from beyond the stars to say hello. Alongside the Arecibo message, the Pioneer engraving will give any civilisations out there a clue that there is something else trying to make contact.
We have come full circle, as many pulsars do. From being mistaken for communications beyond the stars, we have come to use them as our own messages to what might be out there. Pulsars are certainly one of most bizarre interstellar objects which we’ve detected. Certainly, we have a lot to learn from their structure and exotic matter. In the matter of aliens versus pulsars, perhaps the truth is stranger than fiction.
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The opinions expressed in this article are those of Dr George Aitch and Dr Janaway alone and may not represent those of their affiliates. Images courtesy of flickr.
- Burnell, S. Jocelyn Bell “Little Green Men, White Dwarfs or Pulsars?” Cosmic Search Magazine. (1977)