Still no sense in signal

Is this a signal from aliens?

By BBC News Online science editor Dr David Whitehouse

A detailed look at the point in space from where an intelligent signal might have come has revealed nothing unusual.

The Ohio Big Ear detected the Wow signal

The observations, using the multiple radio dishes of the Very Large Array (VLA) in New Mexico, US, add to the mystery of what has been called the "Wow" event.

In August 1977, radio astronomers detected what could have been a signal from intelligent life in space. But it happened only once.

Now, two researchers, Robert Grey and Kevin Marvel, have used the VLA to look at the source location with unprecedented sensitivity. They saw nothing strange or anything that could explain the signal.

Narrow band

The Wow signal as it has become known is often described as our best candidate for a signal from an alien intelligence in space.

On 15 August, 1977, a burst of radio waves was detected by the now dismantled Big Ear radio telescope of Ohio State University. The person who spotted it, astronomer Jerry Ehman, was so surprised that he scribbled "Wow" on the print-out.

The event had all the properties that astronomers expected in a signal from an alien intelligence. It was confined to a narrow band of frequencies and it was very close to the "hydrogen line", a natural signpost in the spectrum.

Because the Ohio telescope cannot move, it was only possible to see the signal as it passed across the telescope's field of view. From the way the signal was detected, astronomers were certain it was coming from a point on the sky.

Mystery remains

It only lasted 72 seconds and although researchers later looked at that same patch of sky over a hundred times, they saw nothing. The signal, if it was a signal, was a one-off event.

The VLA was used for a more sensitive search

Some researchers have said it was man-made interference but others pointed to the signal's characteristics and said it definitely came from the sky.

Since 1977, other radio astronomers have looked at that spot on the sky in the hope of a repeat performance, but to no avail.

The latest series of observations, described in the current issue of the Astrophysical Journal, are more than a 100 times more sensitive than the original Ohio observations.

Grey and Marvel see two faint radio sources at the position that Wow came from but both are nothing unusual.

So, the mystery of the Wow signal remains.