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November 2019: Baby Black Holes and Blobs

November 2019

In the show this time, we talk to Connor Smith about searching for blobs in the submillimetre regime, Fiona Porter rounds up the latest news, and we find out what we can see in the November night sky from Ian Morison, Haritina Mogosanu and Samuel Leske.

The News

This month in the news: a historic spacewalk, a water-carrying visitor passes by, and a new method of detecting black holes

To start us off, the first all-female spacewalk has been completed. On the 18th of October, Christina Koch and Jessica Meir, both NASA astronauts, made a spacewalk to perform repairs on the International Space Station. (Note that the audio mistakenly says this took place on the 16th.)

The spacewalk lasted about five and a half hours, and during their excursion the astronauts removed and replaced a faulty battery on the ISS. This is routine maintenance for the space station, and it's hoped that eventually all-female spacewalks will be just as routine. For now, though, it's still very imbalanced – before this, only 14 women had performed spacewalks, compared to 213 men.

It was originally planned that an all-female spacewalk would be completed in March, but this fell through as only one medium-sized spacesuit was available at the time, and it was postponed for safety reasons. Now, however, NASA are working on making their next generation of spacesuits more modular, making them better able to be worn by astronauts of all shapes and sizes. These are being prepared for the Artemis programme, which hopes to put the next man and first women ever on the Moon by 2024.

Next, an interstellar visitor has been passing through our solar system and looks to be carrying water. Comet 2I/Borisov is the second known interstellar object we've spotted in the solar system after ‘Oumuamua, which has been discussed in past episodes. Borisov is of particular interest as the path it's travelling shows it must have originated from deep space, allowing us to see how its properties compare to comets from within the solar system.

Recently it's been noticed that Borisov is showing oxygen in its spectrum, the mostly likely source for which is water breaking down into its constituent hydrogen and oxygen. While this isn't surprising – comets quite frequently carry water – this does make it the first source of interstellar water we've observed, and could provide insight into how water travels in space.

Of particular note is that Borisov also shows cyanide in its spectrum, like solar system comets, and the ratio of water to cyanide has been established to be very similar between the two – it seems despite its far-off origins, so far Borisov isn't that different from the comets we've seen before. Borisov will reach its closest approach to the Sun on around the 8th of December, and is expected to remain visible until at least September 2020, so there's still time yet to find out more.

Finally, a new method of looking for black holes has found its first candidate. Typically, black holes have been identified by observing stars orbiting around them, like the supermassive black hole Sagittarius A*, or more recently, spotting merging with another black hole by LIGO detecting their gravitational waves. This, however, biases the search, as more massive black holes are easier to detect this way than less massive ones.

The new method relies on the fact that it's relatively common for stars to be in binary systems, with two stars orbiting each other. If one of the stars dies and becomes a black hole, it and its companion star still orbit each other, but the black hole no longer emits light. By tracking the change in an apparently single star's emission spectrum, it's possible to identify if it has an invisible black hole companion, as the star's light will be Doppler shifted as it orbits around the black hole.

Recently, this method has identified its first black hole, and in doing so has shown it can find an entirely new class of black hole – low-mass black holes. The detected black hole is only 3.3 solar masses, far less than typical stellar black holes – which tend to be between 10 and 100 solar masses – or those detected by LIGO, which have a typical mass of around 20 solar masses. This is actually quite close to the lower mass limit possible for black holes, which is believed to be between two and three solar masses – any lower than that and a dying star can't collapse into a black hole, and instead becomes a neutron star. Using this method to identify more low-mass black holes will therefore open up an entirely new population to study, and might give us more insight into what happens at the boundary between black hole and neutron star. The paper for this discovery can be found here.

Interview with Connor Smith

We speak to Connor Smith, a PhD student from the University of Cardiff, about his research into "blobs" detected in submillimetre wavelengths by ALMA. These "blobs" are actually individual galaxies existing as part of galaxy clusters, and by studying them over a range of look-back times, their evolutionary history can be traced.

The Night Sky

Northern Hemisphere

Ian Morison tells us what we can see in the Northern Hemisphere night sky during November 2019.

The Planets

Southern Hemisphere

Haritina Mogosanu and Samuel Leske from the Carter Science Centre in New Zealand speaks about the Southern Hemisphere night sky during November 2019.

Odds and Ends

A recent Nature paper announced the detection of strontium produced in the merger of two neutron stars. This is significant because it serves as evidence of the so-called r-process by which many heavy elements are thought to be created. It also proves that neutron star mergers provide suitable conditions for these reactions to take place.

Voyager 2 reached interstellar space on November 5th, joining its twin spacecraft Voyager 1, which crossed this boundary in 2012. They are both 42 years into their flights, and still relay data back to earth daily.

Voyager 2 is now at a distance of 120 astronomical units, or 120 times the distance from the earth to the sun. This marks crossing point to interstellar space, which is defined by where the solar wind and the interstellar wind are in balance. This sharp boundary is also known as the heliopause. The crossing was confirmed by onboard instruments, which measured a change in the plasma density between the hot lower density plasma of the solar wind to the cool, higher-density plasma of interstellar space.

Each Voyager spacecraft was launched in a different direction away from the sun, so scientists can now use the data to measure the shape of the heliopause. So far the data confirms that the heliosphere is strikingly symmetric, at least at the two points where the Voyager spacecraft crossed.

Boeing and SpaceX complete crucial tests on their crew capsules.

Boeing’s CST-100 Starliner completed a pad abort test on Monday, this is where they test the systems to get the crew capsule away from the launchpad if things start to go wrong. Apparently it can accelerate away at up to 650 mph in 5 seconds, which sounds a lot but translates to about 6G.The capsule only deployed two of the 3 parachutes, but according to NASA’s testing standards, this is fine and it passed.

SpaceX did slightly better, on Sunday they ran 13 consecutive successful tests of the upgraded parachutes on the Crew Dragon capsule, of which it needed to pass only 10 to pass. Whilst the capsule has 4 parachutes, these tests were to check that the capsule can still land safely if only 3 deploy, so they intentionally disabled the fourth

Show Credits

News:Fiona Porter
Interview:Connor Smith and Jake Staberg Morgan
Night sky:Ian Morison and Haritina Mogosanu
Presenters:Tiaan Bezuidenhout, Crispin Agar, Roke Cepeda-Arroita
Editors:Joseph Winnicki, Lizzy Lee, Hongming Tang, Tom Scragg
Segment Voice:Tess Jaffe
Website:Michael Wright and Stuart Lowe
Producer:Michael Wright
Cover art:Image of a galaxy cluster (Abell 370) showing lensing CREDIT: NASA, ESA, the Hubble SM4 ERO Team and ST-ECF

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