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October 2020: Worthy Winners

October 2020

In the show this time, we talk to Sofia Wallstrom about Studies of Asymptotic Giant Branch stars with TESS, Michael Wright rounds up the latest news, and we find out what we can see in the October night sky from Ian Morison, Haritina Mogosanu and Samuel Leske.

The News

This month in the news: In the news this month, water under the surface of mars and measurements of radiation on the moon.

Firstly, The announcements have been made for the 2020 Nobel Prize in physics, with both discoveries related to astronomy. Quoting the Nobel Prize summary from their website, the awards were to Roger Penrose "for the discovery that black hole formation is a robust prediction of the general theory of relativity", the other half jointly to Reinhard Genzel and Andrea Ghez "for the discovery of a supermassive compact object at the centre of our galaxy."

A piece of news which which will be discussed in more detail next month is that of the discovery of phosphene on Venus. In brief, A paper has been published finding evidence of large quantities of phosphene in the atmosphere of Venus. Phosphene has for a long time been considered a possible chemical to look for in the search for life on other planets. The levels of phosphene on Venus are not something the authors are able to explain by currently known processes which do not involve life. However the most vital thing to point out is a quote from the paper on the discovery: ‘Even if confirmed, we emphasize that the detection of PH3 is not robust evidence for life, only for anomalous and unexplained chemistry.’

One other interesting piece of news this month is the confirmation of saltwater lakes under the surface of Mars. In 2018, the paper: ‘Radar evidence of subglacial liquid water on Mars’ was published, which used data taken between 2012 and 2015, which suggested that there was a subsurface saltwater lake hidden under the ice at Mars’ south pole. However the finding was made from only 29 observations, which for good reason led to scepticism at the time. Published this month is a follow up using the same Mars Express spacecraft,using an instrument called the ‘Mars Advanced Radar for Subsurface and Ionosphere Sounding’. But now having a much larger dataset, a total of 134 observations.

In the original paper the nature of the body of water could not be defined in detail, however now with far more measurements the paper is able to constrain the spatial distribution of what they refer to as the bright areas. The method used is radio echo sounding, firing radio waves at the surface and measuring the reflected signal. These waves travel through ice and the material underneath that determines their reflection, allowing areas of liquid water to be identified, which is what the paper means by bright areas, areas that indicate liquid water. The reflected signal would be differeent if they were reflected from, say, rock.

The new results identify the previous body of water and lead to the discovery of three other bodies of water around the original one.

This is still not conclusive evidence though, the same instrument is used to perform the detection. So we cannot be entirely sure that the bright spots recorded are evidence of liquid water, however the fact these spots exist is still interesting even if we end up demonstrating a different explanation for their existance.

Another story from the last month is the publishing of the paper ‘First measurements of the radiation dose on the lunar surface’ . The argument for making these sorts of measurements is simple, if we are going to put humans on the moon for long periods of time we need to consider the effect of radiation, and we would expect the radiation dose received by the lunar surface to be far greater than that at earths surface because of the effect of our atmosphere as a radiation shield, with the moon receiving not far off the expected dose in space. During the apollo missions astronauts had dosimiters on them however what is known as ‘time averaged radiation data’ was not acquired. This paper measures that with a specialised dosimetry experiment on the Chang E4 lander.

After processing this data the research results in a dose equivalent rate of 57.1 ± 10.6 microsieverts per hour from charged particles. As a comparison, this is around a couple of hundred times greater than what would be expected in most places on earth. This does create an interesting challenge for long term occupation of the moon.

Interview with Sofia Wallstrom

Dr. Sofia Wallstrom talks about Asymptotic Giant Branch (AGB) stars, a stage that all stars up to 10 solar masses evolve onto late in their lives before dying as white dwarfs. Despite this, there are still many unknowns in how these stars behave. A recent project called the Nearby Evolved Stars Survey (NESS) has been working towards observing 500 AGB stars within 2kpc, and some initial results are now available, which Sofia discusses. She also talks about her recent work with ALMA.

The Night Sky

Northern Hemisphere

Ian Morison tells us what we can see in the Northern Hemisphere night sky during October 2020.

The Planets

Highlights of the Month

Southern Hemisphere

Haritina Mogosanu and Samuel Leske from the Carter Science Centre in New Zealand speaks about the Southern Hemisphere night sky during October 2020.

SEE WITH THE NAKED EYE 

SEE WITH BINOCULARS AND TELESCOPE

IN OCTOBER

Bright Objects

Odds and Ends

Recent research reveals a supernova exploded in Earth's vicinity just 2.5 million years ago! (To put that in context, the asteroid that wiped out the dinosaurs was 65 million years ago, and 2.5 million years ago was also around the time of the rise of homo habilis, an early ancestor of modern humans). It was also possible to put certain constraints on the properties of the supernova - the progenitor star for example is estimated to be between 11 and 25 solar masses. There is ongoing research into what effect this supernova might have had on Earth. Some say it could have been a contributed factor to the Ice Ages that occurred in the years that followed via stimulation of cloud formation. Others believe it could be linked to a partial extinction event, the 'Pliocene marine megafauna extinction', and even crazier, some postulate that the supernova could be linked to humanities conversion to bipedalism (via the earlier connection to homo habilis).

This year’s Nobel Prize in Physics was shared between three people, with the overall theme of black hole physics. Roger Penrose was awarded half the prize, "for the discovery that black hole formation is a robust prediction of the general theory of relativity", and the other half was shared between Reinhard Genzel and Andrea Ghez, "for the discovery of a supermassive compact object at the centre of our galaxy".Despite how widely-accepted the existence of black holes now is, Penrose’s initial prediction of their existence was only made in 1965, and the discovery of Sagittarius A*, our own galaxy’s supermassive black hole, didn’t occur until 1996! The work of all three physicists has been used to test predictions of general relativity, and thus far these predictions have been confirmed, as expected. Black hole physics is an essential tool for a variety of fields of astronomy, and this work has been invaluable to astrophysics as a whole.

Show Credits

News:Michael Wright
Interview:Sofia Wallstrom and Fiona Porter
Night sky:Ian Morison and Haritina Mogosanu
Presenters:Fiona Porter and Kammy Bogue
Editors:Tiaan Bezuidenhout, Lizzy Lee, Hongming Tang and Tom Scragg.
Segment Voice:Tess Jaffe
Website:Michael Wright and Stuart Lowe
Producer:Michael Wright
Cover art:The central parts of our Galaxy, the Milky Way, as observed in the near-infrared with the NACO instrument on ESO's Very Large Telescope. By following the motions of the most central stars over more than 16 years, astronomers were able to determine the mass of the supermassive black hole that lurks there. CREDIT: ESO/S. Gillessen et al.

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