A leading cosmologist’s face is as red as a planet after his discovery of a brilliant nova turned out to be a false alarm. He had actually observed Mars.

Professor Peter Dunsby, of the University of Cape Town, posted an alert on The Astronomer’s Telegram website, which is followed by scientists around the world.

He reported “the detection of a very bright optical transient in the region between the Lagoon and Trifid Nebulae based on observations obtained from Cape Town on 20 March 2018, between 01:00 and 03:45 UT.”

The mystery object was as bright as the brightest stars – “at least first magnitude” – according to the alert, issued following observations with a small 80mm refracting telescope.

It added: “The object was visible throughout the full duration of the observations and not seen when this field was observed previously (08 March 2018).

“The optical transient is the brightest star in the field. Further observations are strongly encouraged to establish the nature of this very bright optical transient.”

It wasn’t long before the penny dropped about the true nature of the object. It was bright planet Mars which had moved into the starfield during its regular 687-day orbit of the Sun.

Just 40 minutes after the initial alert, Professor Dunsby issued a new “telegram” which read: “The object reported in ATel 11448 has been identified as Mars. Our sincere apologies for the earlier report and the inconvenience caused.”

The Astronomer’s Telegram’s Twitter account made fun of the false alarm by tweeting an elegant “Award for Achievement” certificate to mark Professor Dunsby’s discovery of Mars.

Dunsby took the ribbing in good heart, tweeting:

Lesson learned. Check check and triple check and then check some more!! — peterdunsby (@peterdunsby) March 20, 2018

Professor Dunsby’s slip amused many amateur astronomers who, often unfairly, accuse professional astronomers of lacking a general knowledge of what is in the sky as they focus on particular objects within it. And of course, Mars is but a speck of dust on a cosmological scale.

But he was not the first, and will certainly not be the last to be fooled by the appearance of a bright planet. This writer recalls being phoned many years ago by a breathless amateur stargazer who had found a nova below the Great Square of Pegasus.

It was immediately clear that his nova lay close to the ecliptic – the plane of the Earth’s orbit, along which the planets generally lie – and his nova was the planet Saturn.

If you want help in locating the red planet, take a look at our special guide to finding Mars.

Related: What’s in this month’s night sky

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