Welcome to the November newsletter.

A pdf version of this member’s newsletter which includes an additional section on EAS business and developments is issued to all current members.

See also our monthly Sky Notes for objects observable in the sky from Kendal during this month.

Well this situation just keeps going on… There doesn’t look like there is much of a chance of having real physical meetings until some indeterminate time in the new year. So, we’ll have to make do with Zoom. As many of you will know, last month we had an excellent talk by Sue Bowler on Finding Black Holes. The committee was pleased that so many attended. It does give a good impression to the speaker and makes them feel their effort was worthwhile. So, thanks to you all.

This month, David Glass and Richard Rae will speak on “Galaxies – an evolving story“. This will be in two parts. First, Richard Rae will do a piece on the “Great Debate” which established galaxies as being very distant and outside of the Milky Way. David will then cover the first attempt at classifying galaxy morphology (Hubble’s tuning fork diagram) and how the relationship between morphology (shape) and galaxy evolution has turned out to be a lot more complex. Look out for the email with the meeting joining instructions. Hopefully you’ll all make it.

Over the next few months, we have Graham Fell’s often hilarious and generally quite challenging annual astronomy quiz in December, and Professor Lionel Wilson in January. Lionel’s talk ‘Volcanism on Venus – not quite our twin planet’ had to be postponed in June. Further ahead, in March, Dr Megan Argo will speak to us about the “The future of radio astronomy – the Square Kilometre Array” deferred from last April. David Glass is working on the programme for 2021 so if you’ve any suggestions, he would be glad to hear from you.

The clouds haven’t played that fair this month so my views of Mars at opposition have been somewhat limited. I hope you all did better.

Clear skies.

Ian Bradley, on behalf of the EAS committee.

Astronomy News – David Glass

Salyut 7

This year sees the 35^th anniversary of a daring mission to salvage a derelict space station, which has all the hallmarks of a good sci-fi film. In fact, it’s been dramatized in a film made in 2017!

The Soviet space program launched 7 Salyut space stations in all, the first (Salyut 1) in 1971 and the last (Salyut 7) in 1982. It’s a shame that their history and achievements of these stations aren’t talked about much! (perhaps someone would like to put together a talk for us on this – yes that is a hint!!).

Salyut 7 was uncrewed in the early part of 1985. On 12^th February, circuit breakers tripped and left the station without power, tumbling and with internal temperature dropping. Because the Mir space station was delayed, a mission was planned to board Salyut 7 and restore it to working order. So, on 6^th June 1985 two cosmonauts (Vladimir Dzhanibekov and Viktor Savinykh) were launched to get on board – which they did. The station was equipped with an automatic docking system, but this was down and the cosmonauts had to dock manually by matching the rotation rate of the station (name a sci-fi movie where that was done!). Luckily this was manageable, and Dzhanibekov had experience of this procedure. Once inside they found that they could repair the station – and spent the next ten days doing so in freezing conditions.

They opened up portholes to let sunlight in, and connected the last operable batteries to the solar panels to energise key systems. They could then use the station’s thrusters to stabilise it and align it properly with the Sun. After that, they could begin restoring lights, communications, and air and water supplies. Conditions were harsh for the cosmonauts, but they did it!

Their journey didn’t end there – with the station in operation again, Dzhanibekov stayed for 110 days, while Savinykh spent a further 168 days on the station (coming back on a different spacecraft).

I’ve just found that the film Salyut 17 is on Amazon Prime Video (N.B. no endorsement implied!) – I’ll let you know what it’s like!

Who could be listening in?

Astronomers have managed to detect exoplanets by watching them transit their host star, sometimes from back yards. The very slight dip in brightness of the star as a planet passes in front of it can sometimes be measured. One team of researchers chose to reverse the question – from what nearby stars could Earth be detected in the same way? This involved choosing stars whose alignment with the Sun meant that Earth would be seen as passing in front of it. The result – 1004 stars within 100 parsecs would be good vantage points, and the view from 508 stars would achieve a transit time of at least 8 hours.

Thanks to data from the Gaia satellite, the properties of these stars are known and the researchers have produced a catalogue which includes the likely orbital properties of exoplanets within the “temperate zone”, where liquid surface water could exist. This will be of use in designing observation programmes to find exoplanets where some other intelligent species could be designing exactly the same study!

Hertzsprung-Russell diagram of the stars within the Earth Transit Zone (ETZ). For comparison, our Sun has an effective temperature (T_eff) of 5,800K. Cooler stars are dwarfs like our Sun, while hotter stars are giants (Kaltenegger & Pepper 2020).

See this paper.

Betelgeuse yet again

Always a star for surprises (see previous newsletters!), Betelgeuse has thrown another curve-ball. This time, researchers have found two dimming events in 2019 – one due to a dust cloud as discussed in previous newsletters, the other (smaller) due to stellar pulsations. Analysis and computer modelling of the pulsations suggests that Betelgeuse is burning helium at its core, and is therefore quite some way off going supernova (maybe 100,000 years off, i.e. not imminent). Also, the results suggest that Betelgeuse is actually smaller than thought (only 2/3 of the distance from the Sun to Jupiter, not all the way out) and is 25% closer to the Sun (548 light years). This is still a good safety distance for a potential supernova! Which of all the recent papers on Betelgeuse and its fate turns out to be correct will only become apparent over time.

See this research paper.

Imaging a giant nearby exoplanet

The list of exoplanets which have been observed directly has increased by one. Beta Pictoris c, an exoplanet about 9 times the mass of Jupiter, has been imaged using four optical telescopes that form the VLT and the GRAVITY instrument. Beta Pictoris b, an exoplanet 11 times the mass of Jupiter, has been imaged previously. Discovery of Beta Pictoris c by the radial velocity method was first announced in 2019.

The newly imaged exoplanet is closer to the star than its companion (2.7 AU compared to 9.8) and completes an orbit every 1,200 days. The system is still relatively young, with a dusty disc still part of it, and the exoplanets within it are thought to be around 10 million years old. The observations also constrain the exoplanet’s properties such as brightness and mass, which are of use to astronomers modelling exoplanet formation processes.

The papers on this can be found here and here

OSIRIS-REx and Bennu

NASA’s OSIRIS-Rex mission to retrieve a sample of nearby asteroid Bennu has received a lot of media coverage recently, after its successful contact with the asteroid surface and sample acquisition. See here.

Therefore, we won’t dwell on it here.

However, one alarming piece of news turned up on the BBC website, stating that a small piece of rock had jammed open the sample chamber door and the sample was leaking out. I sincerely hope that some sample gets back at least!

See here.

SpaceX

No spectacular hops or major releases of cryogenic liquids of late at SpaceX’s Boca Chica site in Texas… but, something interesting is happening at the time of writing. The image below from LabPadre’s NerdleCam on Youtube shows Starship SN8 stacked with its nosecone on. It certainly looks the part! Also visible are cryogenic vapour being vented near a number of very large horizontal vacuum-insulated storage tanks, and what looks like a road tanker for delivering cryogenic liquids in front of the vessels. Venting like this can happen when cooling down vessels and pipework to operating temperature using a slow feed of cold liquid, or by displacement of vapour during filling of vessels. Three hydraulic platforms are in place by SN8, and people appear to be working up there.

It therefore may not be long before SN8 does a “hop”, possibly to a significant altitude, so keep checking the live feeds!

Water on the Moon – Ian Bradley

You will probably have heard about NASA finding water on the Moon. This isn’t a first but a very important discovery. In August 2018, NASA reported finding water ice in the lunar polar regions using NASA’s Moon Mineralogy Mapper (M3) instrument aboard the Indian Chandrayaan-1 spacecraft. At the south pole, this is primarily in craters where the Sun never shines. At the north pole, this is much more sparsely spread.

So what is all the fuss about now? From infra-red spectroscopy measurements from 2009, it was known that there were characteristic absorption features at 3μm possibly from water. However, at this wavelength, there is no way to distinguish molecular water (H2O) from other OH compounds, so it wasn’t clear if there was water outside of the polar region craters.

The new measurements reported in Nature Astronomy, sadly behind a paywall , are measurements at 6μm which unambiguously can identity molecular water. Using the airborne NASA/DLR Stratospheric Observatory for Infrared Astronomy (SOFIA), they observed high southern latitudes near the crater Clavius and a low-latitude portion of Mare Serenitatis. They looked for a difference between the two regions. It is clear that there are distinct absorption features in the Clavius region that indicate there is H2O at the level of 100-400μg/g material. It is expected that the water is trapped in the interior of impact glasses although there have been suggestions it might be in the gaps between grains. The authors also believe this water is a local geology effect and not a global phenomenon.

It needs to be stated that this isn’t a huge quantity of water – no glaciers, streams etc but the observation that there is water outside of the polar craters gives some hope that future astronauts may be able to extract water from the surrounding regolith elsewhere. Paul Hertz, NASA’s Director of Astrophysics, stated

“We had indications that H2O, the familiar water we know, might be present on the sunlit side of the Moon. Now we know it is there. This discovery challenges our understanding of the lunar surface and raises intriguing questions about resources relevant for deep space exploration.”

Rosetta, Philae and Comet 67P/Churyumov-Gerasimenko – Ian Bradley

Remember the fantastic Rosetta Mission to Comet 67P/Churyumov-Gerasimenko? Its lander Philae descended to the surface of the on 12 November 2014 and bounced after its anchoring harpoons failed. After another two-hour flight, Philae bounced again off a cliff, and rolled into a crevice. It was finally found in the Rosetta imagery nearly 2 years later. But where was this bounce?

It was announced today, October 28th, that after a remarkable detective story, ESA’s Laurence O’Rourke has solved this. The team knew from the data that Philae had dug into the surface and probably exposed clean but primitive (billions-of-years-old) ice. Reanalysing the touchdown data, he found that Philae spent nearly two minutes at the bounce site, creating at least four distinct surface contacts as it ploughed across it.

To cut a long story short, the impact left a bright area of clean ice of about 3.5 square metres and some 30m away from Philae’s final resting place. This scar was really prominent in later imagery of the area being brighter because the impact removed the dark surface caused by space weathering and micro-impacts – you probably remember that the comet nucleus was really dark. Data from its magnetometer boom allowed the team to figure out which direction it was pointing and the timing as it spun, slid and rolled during these few minutes of this second contact. One particularly imprint revealed in the images was created as Philae’s top surface sank 25 cm into the ice on the side of a crevice, leaving identifiable marks of its drill tower and sides.

The lander rolled over a boulder that looks a little bit like a skull wearing a hat. O’Rourke said “The right ‘eye’ of the ‘skull face’ was made by Philae’s top surface compressing the dust while the gap between the boulders is ‘skull-top crevice’, where Philae acted like a windmill to pass between them.”

The impact that created the ‘eye’ also allowed the researchers to determine that the boulder had the constituency of ‘cappuccino froth’ and really porous, consistent with earlier measurements on the nucleus as a whole. These measurements really indicate the mechanical strength and structure of the comet when it formed 4.5 billion years ago.

There are some nice animations here

There is a commentary on the final Nature paper here and also here. The full paper is behind a paywall.

Constellation of the month – Ian Bradley

Sorry, Moira is unavailable so you’ll have to put up with me!

Since Pegasus is due south around 21:00 mid-month, it seems a logical choice. It is also frequently overlooked due to its neighbour Andromeda, especially so given that that contains the M31 galaxy.

Credit: IAU and Sky & Telescope magazine

Pegasus is one of Ptolemy’s original 48 constellations and named after the mythological magical winged horse. Pegasus is one of the offspring of the gorgon Medusa (the other being Chrysaor who I’ve never heard of) and the god Poseidon, both ‘born’ when Perseus chopped off Medusa’s head. Perseus then flew away on Pegasus. During this flight, he spotted Andromeda chained to a rock… and rescued her. The rest they say is ‘history’. Now Pegasus, Andromeda and Perseus line up next to one another…

The most obvious thing about this constellation is the four magnitude 2 stars forming the asterism of the Square of Pegasus. Ironically, the brightest star, Alpheratz, belongs to the constellation of Andromeda! Markab α-Pegasi, Scheat β-Pegasi, and Algenib γ-Pegasi, together with Alpheratz α-Andromedae (also designated δ−Pegasi) form the square and the orange super giant Enif ε-Pegasi marks the muzzle. Enif, which means The Nose in is actually the brightest star in the constellation. Scheat is an irregular variable star similar in behaviour to Betelgeuse. It varies in magnitude from 2.3 to 2.7. Although the diameter changes as the star‘s brightness changes, it is estimated to be about 150 times larger in diameter than our Sun. In other words, it would nearly fill the space inside the Earth’s orbit around the Sun! As its mass is estimated to be only 9 times that of the Sun, it is literally a ball of hot gas. It would make a nice eyeball or binocular measurement project using Markab and Algenib as comparison stars. The AAVSO gives a period of 43.3 days…

Algenib is also variable although the changes are very small (0.04 magnitudes) and very rapidly changing (3.64h). It is a β-Canoris Majoris is type variable, a class of variable stars that exhibit small rapid variations in the variability of Scheat.

The most obvious deep sky object is the globular cluster M15. AT magnitude 6.4 and 12’ in diameter (~1/3^rd that of the Moon) it is relatively easy to find. Just follow the line joining θ to Enif and continue beyond Enif another 4° (about half the field of view of a typical pair of binoculars). My book describes it as ‘a very nice example of a globular cluster that dominates the autumn skies. It has an intense starlike centre…’ (K. Graun: Finding and Viewing the Messier Objects). Most other objects deep sky objects require a telescope. A few degrees north west of Matar, η-Pegasi, lies the Deer Lick Group of galaxies. Dominated by the spiral NGC 7331, y 40 million light years distant, a is group of about 6 galaxies. Just 30’ away lies Stefan’s Quintet, a group of 4 fainter gravitationally tidally disrupted galaxies with another one in the same line of sight. Have a look at the fabulous image on APOD

Imaging this could be quite a challenge.

Recent Photographs

I guess that it is until next year as I might struggle to get the 6 hours of exposure necessary for the 3 frame mosaic. This astrophotography game can be frustrating! Credit: Ian Bradley