What’s in the sky this month
For Noctilucent Clouds (NLC), ISS passes, the Moon, the planets, comets, meteor showers and Sky Charts for this summer see our Sky Notes page.
Astronomy News July 2020 – David Glass, Richard Rae & Ian Bradley
Space X and Dragon launch
SpaceX made history with the launch of NASA astronauts aboard Spacex’s Dragon vehicle for a visit to the ISS.
The last weekend in May marked a turning point in frontier space history. A private company is now providing a “taxi service” to transport astronauts to the International Space Station. SpaceX has successfully delivered 2 astronauts. I hope you were all glued to the live NASA news feeds watching this significant event unfold. Sole dependence on the ageing Russian Soyuz capsules launching from Kazakhstan system is now a thing of the past.
To put this in perspective, the last astronaut to be launched from America was nearly a decade ago in 2011 with the space shuttle. Previously SpaceX has successfully sent un-manned flights to the space station in 2019 using automated docking procedures.
SpaceX transport system for crew and cargo will now be a gamechanger in this rapidly developing industry.
Following on from the spectacular Crew Dragon launch and rendezvous with the ISS, our attention turns back to the Starship project. You’d think that they would have learned something from their high-profile failures – well it seems they might have. Starship SN5 has apparently passed a full cryogenic proof test on 30/6 and is now being fitted with a Raptor engine for further tests.
Earlier, a section of SN7 was tested to destruction. Whether this was intentional wasn’t known at the time. This a classic example of a quasi-instantaneous release of pressurised cryogenic liquid.
Keep an eye out for live coverage of engine testing and any other tests that happen. There are some lively amateur YouTube sites that provide running commentary from their own webcams on nearby apartment blocks trained on the testing site. Here is one with an informative running commentary, local insight and buzzing live chat.
You probably remember the dimming event that affected Betelgeuse last Winter. At the time, everyone thought that the star had coughed out a cloud of dust that caused it to dim at optical wavelengths. It turns out that it was probably giant “starspots” instead. A team used observations at sub-mm wavelengths to investigate what had happened. They found that Betelgeuse dimmed by around 20% at sub-mm wavelengths, which is much more than could be achieved by external dust. The dimming must therefore have been caused by large cooler patches in the star’s photosphere, possibly covering 50 – 70% of the star’s surface.
Here’s a link to the paper describing the results.
The “Missing Link” Between Neutron Stars and Black Holes
It’s been known for a while now that when massive stars end their lives as supernovae, they can leave behind either a neutron star or a black hole. However, no neutron star with mass greater than 2.5 times the mass of the Sun has been found, or no black hole with mass less than 5 Solar masses. There is a gap in mass which nobody understood. However, in August 2019 the LIGO gravitational wave observatory detected an object with a mass of 2.6 Solar masses, as it merged with a more massive black hole. No optical counterpart to the event was detected. here is the paper for this discovery (click on the pdf button).
They conclude “we cannot firmly exclude the possibility that [the less massive object] is a neutron star, nor can we be certain that it is a black hole”.
Pluto and its Sub-Surface Ocean
The spectacular images of Pluto sent back by the New Horizons spacecraft were just the start. Based on the data received, there is now evidence of a liquid water ocean underneath Pluto’s crust. A team examined the images for signs of stretching or compression, which is what would happen if a sub-surface liquid ocean were to freeze because ice expands when it forms. However, nothing was found even in the oldest terrains, implying that sub-surface water is in a liquid state. This and other key findings are explained if Pluto formed hot within a few tens of thousands of years, and maintained its internal heat through collisions. Sub-surface oceans on planets (dwarf or otherwise) and moons are potential locations for extraterrestrial life, and therefore attract a lot of interest. The paper is behind a paywall , but the abstract is worth a read.
Remote Observing with the IRAM 30m Telescope – from Windermere
This worked very well, and I managed to get everything observed for my project during the last week of June. I also invited another postgrad student to join in remotely from Preston, to get the experience of observing with this telescope. I’m very grateful to the folk at IRAM, Granada for getting the telescope operational again after the Covid-19 crisis.
Centaurs – Richard Rae
I am sure we were all intrigued to hear about extra-solar system visitors to our solar system such as the interstellar object Oumuamua that was discovered floating through our patch of space in 2017. However, would it not be quite the discovery to find we have had “visitors” from afar joining our solar system many millions of years ago!
Centaurs are small intriguing objects that have orbits that cross those of the outer planets.
New research examining the past orbits of these Centaur objects focuses on their origin and whether or not they could have been present at the formation period of our solar system. The paper by Fathi Namouni (Observatoire de la Côte d’Azur, France) and Maria Helena Morais (Universidade Estadual Paulista, Brazil) suggest that 19 obects have been captured by our solar system that were previously orbiting other stellar systems.
Who would have believed we had so many interstellar objects within our midst?
For the full MNRAS paper click this link.
Neutrinos from the Sun confirm stellar physics theory – Ian Bradley
For many years, the lack of the expected neutrinos from the Sun puzzled astrophysicists. In the 1960’s, Ray Davis’ huge tank of cleaning fluid detected far fewer neutrinos than expected.
Neutrinos are released by fusion reactions inside the core of stars and provide a direct way to measure those processes. They are extremely difficult to detect despite thousands of millions passing through your fingernail each bsecond. The rate of neutrinos detected from the Sun, indicates the rate of fusion inside the core of the Sun. Davis’s experiment only measured 30% of the expected rate. That problem was solved when it was discovered in the early 2000’s that neutrinos can change in their passage from the Sun to detectors on Earth into ones the detectors couldn’t detect. Detectors have improved enormously, both in efficiency and size, since Ray Davis’s day.
nside the core of the Sun, the main fusion process is 4 protons fuse together (in a multistage process) to produce helium and energy [plus two neutrinos]. This proton-proton chain reaction dominates in low mass stars like our Sun. In higher mass stars, a different process dominates – the carbon-nitrogen (CN or CNO) reaction. The nett result is the same, 4 hydrogen nuclei fuse together releasing helium, energy and two neutrinos. In stars like our Sun, the core is too cool for this process to be dominant and only about 1% of the Sun’s energy is produced by this process.
However, the new detectors have allowed this weak process to be detected despite the high background from p-p chain neutrinos. This detection confirms for the first time the decades- old theoretical predictions that some of the Sun’s energy is made by this process and that our understanding of the fundamental fusion processes is correct. More details in this full article [free].
A simple project: a right-angle polarscope viewer – by David Glass
Some of us at least have had the joy of trying to use a polarscope to align a telescope at our latitude. I don’t know anyone with a sufficiently flexible neck or back to do it properly. The solution – make a right-angle viewer. A good recipe is here.
…and I thought I’d give it a go.
I managed to get an old Pentacon (East German) right-angle camera finder on Ebay – it was grubby but it cleaned up very well. I then cut up an old 35mm film canister and made a shaped slot at the back to fit the adapter – and voilà! No more wet/dented knees and sore neck. The viewer is not that heavy and doesn’t affect the polarscope. The film canister provides a snug fit and can be removed without harming the polarscope.