Psyche could reveal secrets about Earth

There is a small minor planet, only 210 kilometres across, that could unlock some of the secrets of our own planet. This is Psyche, which orbits in the asteroid belt between the orbits of Mars and Jupiter. 

There is a lot that we don’t know about the origin and inner structure of Earth. In particular, we do not know exactly how the planet came to be formed or what the composition is of its solid metal core. We cannot examine this directly because it is surrounded by thousands of kilometres of molten metal and magma. 

So where does Psyche come into the picture?

Observations of the asteroid reveal that it is composed almost entirely of solid metal, and there is nothing else in the solar system – as far as we know – of which this can be said. The implication is that Psyche is a remnant of a former planet that was once considerably larger, but was so battered about by collisions with other objects that all the outer layers were knocked off to leave only the solid metal core. Could this therefore be similar to what lies at the heart of Planet Earth?

Astronomers are keen to send a probe to Psyche to find out. A launch date for a mission to Psyche has been set for 2022, with the destination reached in 2026. 

The spacecraft will be equipped with a range of instruments to enable the nature of Psyche’s gravity to be established, which will in turn allow deductions to be made about its composition and structure. There will also be a gamma ray and neutron spectrometer on board, which will be used to discover the exact range of metals of which Psyche is composed. It is thought that the main elements will be iron and nickel, but there is a distinct possibility that silver, gold, palladium, copper and iridium will also be present.

The purpose of the mission is to gain knowledge, from which inferences will be made about Earth’s interior. The assumption is that the early solar system contained many similarly composed lumps of metal, most of which coalesced and ended up as planetary cores.

However, there is also room for speculation about how such a world might be a source of future benefit to mankind in terms of its content. All that metal, just sitting there doing nothing! An estimate has been made of what Psyche might be worth in terms of monetary value, and it is a truly staggering figure,  namely ten quintillion dollars – a one followed by nineteen zeros!

If anyone imagines that all that metal could be transferred to Earth and the value realized, they need to think again. For one thing, the idea is pure fantasy. For another, the value of something like gold depends on its scarcity – make vast quantities of it available and it will no longer be valuable!

© John Welford

The Great Comet of 1680

The comet that appeared in the sky in November 1680 has two main claims to fame. It was the first to be discovered by telescope and the first to have a known orbit. 

It was found by accident by Gottfried Kirch, a German astronomer, when he was actually observing the Moon through his telescope, but as it approached closer to Earth it became clearly visible to everyone as it streaked across the sky. 

The orbit was calculated by Isaac Newton who made use of his new theory of universal gravity, publishing his results in his “Principia Mathematica” in 1687. 

The Great Comet was seen twice – once as a morning phenomenon as it headed towards the Sun and later in the evenings as it made its return journey towards the outer regions of the Solar System. Newton was the first person to appreciate that these appearances were of the same comet. It had previously been assumed that comets travelled in straight lines, passing through only once. Newton’s discovery that comets travelled round the Sun in parabolic curves was what enabled Edmund Halley to predict that the comet named after him would return every 76 years.

Robert Hooke, the English physicist, noticed a stream of light issuing from the comet’s nucleus. This was the first description of the emanation of jets of material from active areas.

The Great Comet will not be seen again in the lifetime of anyone alive today. Its orbit takes it into the outer regions of the Solar System and it will not return for more than 9,000 years!

© John Welford

Planet X and The Goblin

Astronomers have long taken the view that the Solar System has a planet that nobody has seen but which might offer an explanation for some of the phenomena that have been discovered and which present as-yet-unanswered questions. This planet is believed to be of substantial size and therefore unlike any of the dwarf planets that are known to exist in the outer reaches of the Solar System. However, it is the very size and mass of this planet that is believed to cause the phenomena in question, such as the elongated orbits of the dwarf planets and the existence of comets that are sent hurtling towards the inner Solar System from their natural orbits way beyond that of Pluto.

The planet has been given the title Planet X – the X can either be taken to signify “unknown” or the Roman numeral for ten. It would have been the tenth planet when Pluto was still regarded as the ninth. 

In October 2015 a new dwarf planet was discovered that might help in the search for Planet X. The dwarf is about 300 kilometres in diameter and probably consists of a ball of ice. It was nicknamed “The Goblin” thanks to its discovery at around Halloween.

Work done since the initial discovery has shown that the Goblin has an extremely elongated orbit that takes it about 2300 times further away from the Sun than Earth. A complete orbit would take about 40,000 Earth years.

The Goblin would appear to be orbiting as one of a cluster of similar objects, which poses the question of why such a cluster might form. The intriguing thought is that Planet X, if it exists, would have precisely the effect that is being seen, namely providing a gravitational tug that herds objects including the Goblin into their extreme orbits.

This suggests that Planet X has a similarly elongated orbit and might therefore be so far away from the Sun at present that it is unlikely to be seen from Earth any time soon. But at least the discovery of the Goblin gives astronomers hope that they are looking in the right direction.

(The illustration is an artist’s impression of another dwarf planet, namely Sedna)

©John Welford