by Duncan Lunan

In 1973-75 ASTRA, which was then Scotland’s national spaceflight society, ran the Interplanetary Project, a series of talks and discussions which, after multiple extensions, led to the books New Worlds for Old  (David & Charles, 1979)  and Man and the Planets  (Ashgrove Press, 1983). 

The major speakers were to contribute guest chapters, but that was not a success.  Only one guest  chapter was delivered on time;  I had to write one chapter myself because it was never delivered at all, and another because it went completely off-topic;  another was so out-of-date that the editor and I had to rewrite it between us;  and two were double the required length, needing cuts to which one author strongly objected.  Each change meant a redrafting of the Memorandum of Agreement between the contributors, as things were done in those days, each new version having to be signed and witnessed by all contributors;  the final draft by the late John Mason was a masterful piece of legalese running to four pages in a single grammatical sentence, summarising all the previous versions and alterations, beginning “WHEREAS”, continuing “AND WHEREAS… AND WHEREAS…”, concluding “THEREFORE THIS AGREEMENT WITNESSETH:” and listing what the final distribution would be.  It put me off guest chapters for life and none of my later books have had any.

One last mixed blessing was the contribution by the late A.T.  (Tony)  Lawton, subsequently Chairman of the British Interplanetary Society.  I had asked him for a talk and a chapter on ‘The,  Resources of the Outer Solar System’, expecting a reprise of the articles about Pluto, the possible existence of the Kuiper Belt beyond, and a possible ‘Tenth Planet’ as it was then called, about which he had been writing for the ‘New Frontiers’ issues of the BIS magazine Spaceflight.  Instead his lecture at the Royal Hotel in Hamilton in May 1974 was much more far-reaching and original, which was excellent, but it made the book still longer because it still needed a chapter on Pluto and the Kuiper Belt which I had to write at short notice.

Lawton began by introducing the concept of the ‘isogravisphere’ – valid, as far as I know, though I’ve never seen it elsewhere – the surface around the Solar System where the gravitational pull of the Sun matches those of the surrounding stars. 

His calculations indicated that it was roughly spherical and surprisingly extensive, reaching out to 10 light-years in most directions  (Fig. 1)  but penetrated by deep funnels enclosing Alpha Centauri, Sirius and Procyon  (Fig. 2). 

He thought that dust within that volume might settle into a huge disc in the plane of the Solar System, surrounding the Ecliptic  (see ‘Beginners Astronomy, Part 3:  Coordinate Systems’, ON, April 4^th 2021), with concentrations in the funnels big enough to build new solar systems, using ramscoop fields to gather the material  (see ‘Connecting the Dots’, ON, 18^th May 2025).  He advised against letting them build up into black holes, which might be dangerous so close to the Sun, but that idea was taken up by Adrian Berry of the Daily Telegraph and featured in his book The Iron Sun, Crossing the Universe through Black Holes  (Jonathan Cape, 1978, Fig. 3). 

I agreed with Lawton:  if black holes can be used as ‘star gates’, there must be rules governing where things that fall into them will come out, and the most likely place is the nearest centre of mass, i.e. the Sun.  Berry dismissed the objection as ‘ridiculous’, but never explained why.

As I was drafting the books, a news item in the Journal of the British Interplanetary Society drew my attention to a paper by Prof J.D. Fernie of the Dunlop Observatory in Canada  (‘Interstellar Absorption in the Galactic Neighbourhood of the Sun’, Astronomical Journal, May 1962).  He had synthesised observations around the plane of the Ecliptic, up to 10 degrees above and below it, and concluded that the Sun was driving what could only be described as a ‘Lawton funnel’ into a dust cloud which he attributed to a very large, distant supernova  (Fig. 4). 

But when I plotted his graph in the round, on a scale figure of the ‘Galactic Neighbourhood’, I found a distribution which the late Chris Boyce described as ‘obviously not random’  (Fig. 5).  Not just the neighbour stars but the Sun’s motion with respect to them, towards the Apex of the Sun’s Way in the constellation Lyra  (see ”Oumuamua, Part 2′, ON, 24^th December 2023)  looked to be significant, and so did the Galactic Centre-Sun L1 point, which the Soviet astronomer Chebotarev had calculated to lie at 1.02 parsecs  (3.325 light-years)  in that direction.

An explanation for the absorption on that sight-line came up in 1977, in a letter from a correspondent in Venezuela, Dr. Armando Mencia, enclosing cuttings headlined ‘Se Acerca Una Nube Negra!’  (Watch out for a black cloud!’, Memento, Caracas, 26^th September 1977, Fig. 6).  The magazine’s reference was to Sir Fred Hoyle’s first novel, The Black Cloud  (1957), in which a sentient interstellar cloud enters the Solar System, with drastic results  (Fig. 7). 

It was one of a number of Spanish articles which I couldn’t get translated in Troon, at that time, so I don’t know how Memento did it, but their author had an advance copy of the paper by Alfred Vidal-Madjar et al which was published the following year  (‘Is the Solar System Entering a Nearby Interstellar Cloud?’, The Astronomical Journal, July 15^th 1978, Fig. 8).  Their observations led them to suggest that a dust cloud 0.1 to 1.0 parsecs across could be coming our way  (Figs. 9 & 10). 

A news item about it appeared in September that year in Sky & Telescope, and attracted little notice except for a novel by the late Martin Caidin called Exit Earth  (1987, Fig. 11), about which the kindest that can be said is that it wasn’t written on one of his better days.  (I gave readings from it in one of the ‘Turkey Buffets’ organised by the late Bill Morris for Glasgow SF conventions, and all present, including the Guest of Honour C.J. Cherryh, agreed that it was a turkey indeed.)  

My first wife remarked that ‘There ought to be some simple process to account for that  [Fig. 5]’, and after adding the Sun’s velocity vector, my first thought was that the Solar Wind might be generating a shockwave in the interstellar medium, with consequent eddy effects  (Fig. 12). 

Some fast-moving stars do generate such shockwaves, among them Betelgeuse  (Fig. 13)  and Mira Ceti  (Fig. 14).  The idea particularly appealed to the late Andy Nimmo of the Space Settlers Society, who was pushing a concept of his own called ‘Shockwave Cosmology’, which would make all the stars much older than they’re believed to be and justify his disbelief in the Big Bang.  But when I took my version to one of the BIS Interstellar Conferences, I was quite firmly told that the Solar Wind could never exert enough pressure for that.  Indeed, although the ‘heliopause’ where the Solar Wind meets the interstellar medium is much further out than expected  (note that the scale of Fig. 15 is logarithmic), there is no hard boundary  (Fig. 16). 

The anticipated bow shock does not exist, and Voyager 1 experienced a smooth transition from one to the other when it reached it  (Fig. 17).  Voyager 2 has since followed suit, while a satellite called IBEX has been mapping the heliopause from Earth orbit  (Figs. 18-20), and New Horizons is expected to reach it around 2027. 

Both IBEX and New Horizons are now to be switched off, halfway through their missions, because they have nothing to do with putting Americans on the Moon during Donald Trump’s presidency.

My last foray with the dust hypothesis was to suggest that it was all down to eddies  (Fig. 21), except for the feature which I marked ‘to supernova cloud’.  In 1985 I won Honorable Mention with an article called ‘Shadows on the Milky Way’, in the annual Hughes Aircraft/Griffith Observer essay contest.  Integrating Lawton’s ideas about ‘Planet X’ with what we knew by then about volcanism on Io, and integrating it with earlier prediction about it by the Soviet S.K. Vsekhsvyatskiy, I suggested that the last dust feature might mark the position of the tenth planet if it had a large satellite, in retrograde orbit like Neptune’s Triton and with volcanoes like Io’s. 

I featured that model of it in my last story for Sydney Jordan’s Lance McLane strip  (‘Out of the Ecliptic’, Daily Record, 1987-88, Figs. 22-23).  I haven’t completely given up hope for it:  Lawton suggested ‘Odin’ for the 10^th planet, to the delight of the Glasgow Viking Re-enactment Society, and if it’s adopted and my model is correct, the satellite should be called ‘Frigg’.  I know some people who would think that all too apt.

Intriguingly, I found a mysterious feature in the right place on the data from the Infra-Red Astronomy Satellite IRAS in 1973, and when I checked it against the WISE data in the 2010s, it wasn’t there any more.  Although it’s now thought that Planet 9 is much larger and further out than Lawton and I thought, if it exists, that has just happened again with another disappearing IRAS object  (Mark Thompson, ‘Is This the First Hint of Planet 9?’, Universe Today, online, 26^th April 2025), and a new analysis suggests it could have been the first planet to form and been expelled to the outer reaches  (EarthSky Voices, ‘Wide-Orbit Planets Support the Possibility of Planet 9’, online, 11^th June 2025), which is pretty much what I suggested  (‘Shadows on the Milky Way’, Griffith Observer,  December 1986), though I imagined its birth in another solar system.  I shall be watching to see how close the i-r sources are, if at all.

Meanwhile, mapping of clouds around the Solar System has moved on.  Recent charts show a general similarity to the figures I derived from Prof. Fernie’s absorption curves, but the clouds are more ragged and a great deal further out, extending to the limits of the isogravisphere  (Fig. 24), and their motions are less systematic than I suggested, though the overall drift is similar  (Fig. 25). 

Interestingly, the Vidal-Madjar cloud is still there, now called ‘Cloud G’, though it’s more diffuse and going past us.  These features contain gas as well as dust, and were thought to be remnants of supernovae in a cluster which the Solar System entered 5-10 million years ago, now responsible for an expanding bubble of gas about 300 light-years across. 

(Fig. 26;  Evan Gough, ‘New Estimate Puts the Supernova Killzone within 50 Light-years of Earth’, Universe Today, 15^th May 2017.)  But more recent data from the GAIA telescope  (see ‘The Sky Above You, February 2025′, 1^st February 2025), indicate that the events formed the Local Bubble  (Figs. 27-29), now 1000 light-years across and expanding at 4 kilometres per second, generating star-forming regions in Taurus, Ophiucus, Lupus, Corona Australis, Musca and Chameleon, all on the surface of the Bubble at approximately 500 l.y..  (Deborah Byrd, ‘1,000-light-year-wide Local Bubble drives star formation near our sun’, EarthSky, January 14^th, 2022;  Catherine Zucker et al, ‘Star formation near the Sun is driven by expansion of the Local Bubble’, Nature, 12^th January 2022.)  

The Bubble is depleted in hydrogen, relative to interstellar space as a whole, which is good news for Daedalus starships and Gerry Nordley’s concept  (see review, Around Alien Stars, ON, 25^th May 2025, less so for ramscoops  (see ‘Connecting the Dots’, above).  But what makes all this topical is the discovery of a new and unexplained feature on the inside of the Local Bubble  (Paul Scott Anderson, ‘Eos: Huge nearby cloud in space was invisible … until now’, EarthSky, 1^st May 2025, Figs. 29-32).  

The Eos Cloud of molecular hydrogen, rich in dust, is 300 light-years away at its inner edge;  it contains about 3,400 solar masses, and would be 40 times the size of the Full Moon if we could see it  (Fig. 33), but because it contains less hydrogen than most interstellar clouds, it’s detectable only in the ultraviolet, where it has been ‘hiding’ till now.  It’s not stable and is liable to disperse in about 6 million years, so if you have a Lawton ramscoop to hand, make the most of it, ‘dust around the Solar System’ and sweep it up while it’s here.