The Sky Above You, July 2024
by Duncan Lunan
The Moon will be New on July 5th, and Full on July 21st. The Moon is near Mars on the mornings of the 1st and 2nd, and near Jupiter and the Pleiades on July 3rd. It’s near Mercury on the 7th, Uranus on the 15th and 16th, and Saturn on the 24th, all of these morning events, as the previous grouping of planets beyond the Sun disperses. After the Moon enters Last Quarter on the 28th, its waning crescent will pass Mars and the Pleiades again on July 30th, and Jupiter again on the 31st.
As predicted, the Chang’e-6 spacecraft delivered its samples from Apollo crater on the lunar Farside to Mongolia on June 25th. I had wondered whether the return trajectory would be a slow working outwards from the Moon, like India’s Chandrayaan-3 vehicle earlier, but it was a single operation – the only doubt seems to be whether the departure burn was on June 20th or 21st. China has issued an invitation for international participation in analysing the samples, which are expected to yield major scientific results.
The planet Mercury is in the northwest sky in early July, south of the Moon on the 7th, setting before Leo, so off our map by 9 p.m., an hour before sunset in Ayrshire, so be very cautious looking for it. It’s furthest from the Sun on July 22nd, disappearing soon after.
Venus is still out of sight beyond the Sun.
Mars, still faint, will rise about 1.50 a.m. on July 1st, rising earlier and passing from Aries into Taurus during the month. Mars passes Uranus on the 15th and 16th, catching up with Jupiter in Taurus at the end of the month. Mars is near the Moon on the 1st and 2nd, again on the 30th.
On Mars, there are two major stories. The Insight lander, which was disabled by dust accumulating on its solar panels in 2022, is now being covered by dust much faster than expected – see ‘Martian Dust Storms’, Orkney News, 23rd June 2024. And the other story is a truly remarkable traverse which has been accomplished by the Perseverance rover.
Perseverance had been making its way up the Neretva Valles, a river which flowed into Jezero crater about 3 billion years ago, when the crater was a lake. The rover was on the south rim of the valley, but headway was becoming difficult due to a field of boulders which were larger than expected. Its AutoNav system was failing to cope with finding a route between them. The target was on the other side of the river, a light-coloured area called ‘Bright Angel’ which might be where a tributary fed into Neretva Valles.
Failing to draw level with Bright Angel, Perseverance’s controllers began looking for an earlier way across, and having found one, they decided to take a run at it. After looking downstream from ‘Overlook Mountain’ on May 27th, the route led down a ramp to the valley floor, cutting through a dune field via ‘Dunraven Pass’ (taking a chance there) but avoiding the main fields of dunes on the river floor.
On the crossing the rover stopped only once, to take a mosaic of a protruding feature called ‘Mount Washburn’. Quite unexpectedly, in the middle of the hillside, not easy to get to, there was a bright, almost shiny rock which has been named ‘Atoka Point’. Spectroscopy suggests that it might be a mixture of pyroxene and feldspar, possibly formed in a volcanic magma chamber. Alternatively, it might be anorthosite, like the ‘Genesis Rock’ found on the Moon by Apollo 15. Either way, it’s not obvious how it got there: washed downstream, presumably, but still in an odd location, as the Genesis Rock was.
After crossing the river, or ‘fording’ it as some journalist put it, although it hasn’t seen water for billions of years, Perseverance found itself in a field of sharp, light-coloured ‘popcorn rocks’, of a type never seen before; and by June 16th, it was on a bed of rock which had clearly been smoothed by water action. The only difficult question is, how many samples to take and leave for future collection, when the sample retrieval programme has run over time and over budget, leading to serious reconsideration. But having reached Bright Angel, the Perseverance controllers are looking to go back over the river bed, because they’ve spotted another tempting target called ‘Serpentine Rapids’ on the south side, where they were to begin with.
Jupiter in Taurus rises at 1.30 a.m., near the crescent Moon on the 3rd, and near Mars, Aldebaran and the Pleiades in the morning sky towards the end of July, near the Moon on the 30th. The following night Jupiter reaches its ‘stationary point’, after which it begins to move eastward as the Earth draws ahead of it.
On June 26th remarkable new images of Jupiter from the James Webb Space Telescope were released, taken in July 2022, with closeups of the Great Red Spot. Unsurprisingly the Spot itself appeared in blue, because the storm projects above Jupiter’s main cloud deck and is correspondingly colder. But over it there were turbulent features which have been identified as hotter hydrogen gas welling up from below. It’s thought these may be ‘gravity waves’, like those of breaking waves on Earth’s beaches, caused by turbulence as deeper currents encounter the GRS as an obstacle. This strikes a chord with me because I described similar effects in a story called ‘The Galilean Problem’, first published in Galaxy in 1971 and reprinted in The Other Side of the Interface (Other Side Books, 2021). I can’t claim any credit for the prediction because my idea of the GRS was based on a suggestion by the Arran-based astronomer V.A. Firsoff. In his book Strange World of the Moon (Hutchinson, 1957), he suggested in passing that the Spot might be a huge blob of frozen gases, floating in Jupiter’s clouds because it was buoyed up by denser layers below. Noting that the spot is lapped by surrounding airstreams at hundreds of miles per hour, I thought that it might be carved by waves, like the ones now suggested, into huge terraces on the upwind side. At least I wasn’t so far wrong with the physics involved.
As we now know, the Red Spot is a storm which reaches hundreds of miles down into the atmosphere of Jupiter, as well as several miles above it. It was supposedly first observed in 1637, and by Cassini from 1675 to 1713. But after that there were no further sightings until Schwabe’s 118 years later. A new study of its dynamics suggests that Cassini was incorrect to call it the Permanent Red Spot, and the one we have now may be another one. (Evan Gough, ‘The Great Red Spot Probably Formed in the 1800s’, Universe Today, online, June 17th, 2024.) During the 20th century the Spot shrank from three times the size of the Earth to only twice, and faded noticeably in colour; in one of his paintings for my Man and the Planets, 1983, Gavin Roberts assumed that it would have faded still further before human beings got there. Indeed, for the last 20 years Jupiter has had a Little Red Spot which may be destined to replace the GRS, though it lost its colour after the first few years. (The colours are thought to be phosphorus compounds formed by solar ultraviolet radiation at high altitudes.) See ‘Jupiter’, ON, September 5th, 2021.
Saturn in Aquarius rises before midnight in early July, about 10 p.m. by the end, and is close to the waning Moon on July 24th.
Uranus in Taurus rises at 1 a.m., above Mars on the 15th and 16th, near the Moon on the 1st and 29th.
Neptune is in Pisces, rising about 11.p.m., and on July 3rd it is ‘stationary’ as the Earth begins to overtake it. Neptune is near the Moon on the 25th.
The Perseid meteor shower commences on July 17th, peaking in August. It’s also worth watching for noctilucent clouds in the north around midnight, and for aurora borealis, as the Sun gets nearer to the peak of its 11-year cycle of activity.
In March 2024, NASA’s budget for space science was announced and contained a serious threat to Chandra, the X-ray space telescope. Chandra (AXAF) was one of the four ‘Great Observatories’ planned in the 1980s, along with the Hubble Space Telescope, the Spitzer infrared one and the Compton gamma-ray observatory, the last two of which are gone. Chandra was launched in 1999 and is still working perfectly, but processing data from it is becoming increasingly costly as technology and computing moves on. NASA anticipates annual cuts to Chandra’s budget, to 10% of the current value in 2029, and there are no replacements planned until far into the 2030s. Chandra’s not the only programme in danger: for example, a choice may have to be made between two members of the Extremely Large Telescope project, the Giant Magellan Telescope and the Thirty Metre Telescope. (Monisha Ravisetti, ‘The Chandra X-ray spacecraft may soon go dark, threatening a great deal of astronomy’, Space.com online, March 25th 2024.) Even though both are already under way, the Constitutional requirement for annual review of all government spending means that things like this are always liable to happen.
A Chandra image taken 7 years ago accompanies a new article about the mystery object Cygnus X-3, by Keith Cooper, the editor of Astronomy Now. (‘Why is mystery object Cygnus X-3 so bright? Astronomers may now have the answer’, Space.com, 26th June 2024.) Cygnus X-3 was discovered in the 1970s and identified as a binary object emitting high-energy jets, drawing attention from the outset because of its very high emission levels. In the early 1980s it was suggested that it could even be the source of high-energy cosmic rays, which are nuclei of heavy elements. We’re shielded from them by the Earth’s magnetic field and atmosphere, but they have very nasty effects on central nervous tissue – three years of unshielded exposure at the level they have here would produce effects like being punch-drunk – impaired concentration and coordination, slurred speech, memory loss etc.. It was thought then that they originated primarily from supernovae, and were then scattered and distributed by the Galaxy’s magnetic field.
If they came from Cygnus X-3 there were two possible explanations. The object was definitely binary, a red giant star orbited by an ultradense companion which was then thought to be a neutron star. Primary cosmic rays could result either from matter being pulled off the primary on to the companion, or as nuclei of heavy elements knocked off the rim of the giant star by the companion’s radiation, if it was a pulsar and the source of the jets. The first explanation is now known to correct: the red giant is a Wolf-Rayet star, subject to violent outbursts at the end of its life – which may be sooner rather than later. The fierce x-ray emission is generated by matter spiralling via a funnel-shaped cavity into the companion star, which is probably a black hole about five times the mass of the Sun. Back in the early 1980s, it was thought that if accretion was the explanation, the red giant could be pulled apart in as little as a century.
If that were the case, primary cosmic rays could be an intermittent phenomenon. They were first discovered on balloon flights in 1912, and their onset might then have been fairly recent. But it could have a bearing on an anomaly I had spotted in the Drake Equation, the one which allows an estimate of the number of high-technology ‘communicative’ civilisations in the Galaxy. Rearranging the terms, one gets an apparent statement that the average lifetime of civilisations is proportional to the rate of formation of stars, even though one might expect the timescales involved to be hugely different. I raised the point with Carl Sagan during his 1985 Gifford Lectures at Glasgow University, but he wasn’t disposed to accept it, perhaps because he didn’t like the possible implications.
If primary cosmic rays were generated in rare events like Cygnus X-3, with large gaps in between, it would be expected that the majority of civilisations would embark on space travel when there were none. Their development would be like the 1950s visions of spaceflight: unshielded spaceships, space stations, lunar settlements, and Mars colonies, described by Arthur C. Clarke in his first novel, The Sands of Mars. The lunar city of The Exploration of the Moon, by Arthur C. Clarke and R.A. Smith, described in Clarke’s 1955 novel Earthlight, was placed underground to shield it from temperature extremes and meteorites, not radiation, and the majority of settlements would be on the open surface. The effects of primary cosmic rays were first detected when the Apollo astronauts reported flashes in their eyes, as the particles passed through their heads killing every cell in their path. For extraterrestrial spacefarers they might come on too subtly to be noticed, or so intensely that the astronauts couldn’t see the controls. The effects on children and embryos don’t bear thinking about. And the results would be that their space programmes would collapse, with effects on their planets which would depend on how dependent on space technology they had become, particularly for materials and energy supply. We might not be alone in the Galaxy, but we might spend the next 20-30 million years finding them all, telling them what their problem had been and that it was safe to come out. I published the idea as ‘Fermi Paradox – the Final Solution?’ in Analog, May 1986, and that was when a furious reader denounced me for supposedly having made the whole problem up. I did get a grudging apology when I sent him the references.
And now the good news. Continuing study of meteorites and moonrocks established that the tracks of cosmic rays in them are not intermittent, at least not over the last several billion years since the formation of the Solar System. They make space travel less convenient, but there are answers to the problems they present, and they’re not a threat that could sneak up on anyone. It turns out that they originate from star-forming regions, some of them in Cygnus, and from the outer layers of supernova remnants like Cassiopeia A (‘Tycho’s Star’ of 1572), which was the first object to be imaged in x-rays by Chandra. It’s still not obvious why increased star formation should shorten the lifetimes of civilisations; it turns out that the major episodes of star formation in the Milky Way have resulted from collision with dwarf galaxies, and the most recent episode ended only 2 billion or so years back, when life on Earth was doing very nicely, thank you, though not yet multicellular and on the way to civilisation.
When I spoke on ‘The Fermi Paradox’ (Where is everybody?) at the Edinburgh International Science Festival in April 1995, I was able to begin with the cosmic ray hypothesis and rule it out as an explanation. It’s nice to have a definite answer to one of my big ideas, rather than the ‘not proven’ which has happened with so many of them. But I’m not disappointed, either: the thought of all those civilisations coming to tragic ends was one I was very glad to have ruled out. It wasn’t Chandra that ruled it out; but it does demonstrate why we need those eyes in the sky out there. As Sir Arthur Conan Doyle said, at the end of The Poison Belt, “how narrow is the path of our material existence, and what abysses may lie to either side of it”. We need the likes of Chandra to keep watch for us.
The Chandra issue is not the only problem in x-ray astronomy at the moment. On September 6th 2023, along with the SLIM moonprobe, the Japanese space agency launched a joint project with NASA called XRISM, X-Ray Imaging and Spectroscopy Mission. XRISM is intended to fill the gap between the current x-ray telescopes (Chandra and XMM), and the European Space Agency’s ATHENA (Advanced Telescope for High Energy Astrophysics), a successor to Chandra which is planned for 2035. Operating in the ‘soft x-ray’ range, XRISM has two onboard ‘telescopes’, Resolve and Xtend; like all x-ray telescopes these have no lenses, focussing incoming x-rays using ultracold thermal detectors, mirrors and diffraction gratings (For a more detailed explanation, see Jackson Ryan, ‘'Absolutely gutted': How a jammed door is locking astronomers out of the X-ray universe’, Universe Today, online, June 12th 2024). Both Resolve and Xtend were launched with protective doors, like the Hubble Telescope’s, but unfortunately Resolve’s has failed to open, limiting its operation to a much higher energy range than planned. At higher energies the door is no obstacle, but it blocks off the range of lower-energy x-rays to which Chandra has access.
The operators of XRISM are now faced with a dilemma, not unlike the ones which the astronauts faced in the repair of the Solar Maximum Mission and the final refurbishment mission to the Hubble Space Telescope. With three attempts by JAXA’s engineers to free the door having failed, the remaining option is to heat the telescope up again and try to shake the door loose. The track record for such operations is not fantastic. The Galileo Jupiter orbiter had to go through a limited version of its mission because three ribs of its high-gain antenna remained closed; the radar booms on ESA’s Mars Express refused to lock, and to reach the orbit required the spacecraft undertook and survived the risky option of flying its atmosphere correction manoeuvre backwards. One of the high-gain antennae on NASA’s Lucy mission is not fully open, though almost, and it just has to be hoped that it will survive the rocket burns to come without collapsing. Moving parts are always the bane of operations in space. As with the SMM and HST repairs, the controllers now have the difficult choice between operating the XRISM in limited mode for the next eleven years at least, or the risk of breaking the telescope altogether. I can only say, I’m just glad the decision isn’t down to me.
Duncan Lunan’s recent books are available through Amazon. For more information see Duncan’s website, www.duncanlunan.com.
The Sky Above You
By Duncan Lunan
About this Column
I began writing this column in early 1983 at the suggestion of the late Chris Boyce. At that time the Post Office would allow 1000 free mailings to start a new business, just under the number of small press newspapers in the UK at the time. I printed a flyer with the help of John Braithwaite (of Braithwaite Telescopes) offering a three-part column for £5, with the sky this month, a series of articles for beginners, and a monthly news feature. The column ran from May 1983 to May 1993 in various newspapers and magazines, but never in more than five outlets at a time, although every one of those 1000-plus papers would have included an astrology column. Since then it’s appeared sporadically in a range of publications including The Southsider in Glasgow and the Dalyan Courier in Turkey, but most often, normally three times per year, in Jeff Hawke’s Cosmos from the first issue in March 2003 until the last in January 2018, with a last piece in “Jeff Hawke, The Epilogue” (Jeff Hawke Club, 2020). It continues to appear monthly in Troon's Going Out and Orkney News, with an expanded version broadcast monthly on Arransound Radio since August 2023
The monthly maps for the column were drawn for me by Jim Barker, based on similar, uncredited ones in Dr. Leon Hausman’s “Astronomy Handbook” (Fawcett Publications, 1956). Jim had to redraw or elongate several of them because they were drawn for mid-US latitudes, about 40 degrees North, making them usable over most of the northern hemisphere. The biggest change needed was in November when only Dubhe, Merak and Megrez of the Big Dipper, as the US version called it, were visible at that latitude. In the UK, all the stars of the Plough are circumpolar, always above the horizon. We decided to keep an insert in the January map showing the position of M42, the Great Nebula in the Sword of Orion, and for that reason, to stick with the set time of 9 p.m., (10 p.m. BST in summer), although in Scotland the sky isn’t dark then during June and July.
To use the maps in theory you should hold them overhead, aligning the North edge to true north, marked by Polaris and indicated by Dubhe and Merak, the Pointers. It’s more practical to hold the map in front of you when looking south and then rotate it as you face east, south and west. Some readers are confused because east is on the left, opposite to terrestrial maps, but that’s because they’re the other way up. When you’re facing south and looking at the sky, east is on your left.
The star patterns are the same for each month of each year, and only the positions of the planets change. (“Astronomy Handbook” accidentally shows Saturn in Virgo during May, showing that the maps weren’t originally drawn for the Hausman book.) Consequently regular readers for a year will by then have built up a complete set of twelve.
©DuncanLunan2013, updated monthly since then.