Institute of Astronomy PUBLIC OPEN EVENING outreach — 19 December 2018 — A

Voyager 2 leaves the TONIGHT’S SPEAKER

An artist’s depiction of the

spacecraft entering interstellar space The talk schedule for can be viewed this term at: to join its twin sister, Voyager 1, more than 18 billion kilometres away from Earth. Credit: NASA/JPL-Caltech Mihkel Kama What can the chemistry of a planet tell us about its origins?

Our weekly welcome ELCOME to our weekly public Wopen evenings for the 2018/19 season. Each night there will be a VOYAGER 2 has crossed the ‘heli- 2 was in perfect working order, and half-hour talk which begins promptly opause’, making it the second hu- was able to measure a sudden drop at 7.15pm. Please note that the talk man-made object to head out into in the on November 5th will be recorded and archived for interstellar space. marking the spacecraft’s transition online streaming. Our Solar System is nestled within into interstellar space. The talk is followed by an oppor- www.ast.cam.ac.uk/public/public_observing/current the ‘’, a protective bub- “We’re not seeing the solar wind tunity to observe if (and only if!) the ble caused by the Solar wind, which any more,” said John Richardson, lead weather is clear. The IoA’s historical shields the Solar System from galactic investigator on one of Voyager’s instru- cosmic rays and the interstellar wind. ments. “That means we must be in the Northumberland and Thorrowgood By examining data from Voyager .” Nicola Fox, di- telescopes, along with our modern 2’s plasma sensors, NASA scientists rector of NASA’s heliophysics division, 16-inch telescope, will be open found that the probe crossed over said “We’ve been waiting with bated for observations. In addition, the the heliosphere’s edge – known as the breath for the last couple of months Cambridge Astronomical Association heliopause – on November 5th 2018. for us to be able to see this”. will provide a floorshow outdoors on The probe reported that the Solar wind Interestingly, many of the readings the Observatory lawns, relaying live strength dropped, the magnetic fields taken by Voyager 2 as it crossed into images from their telescopes and from interstellar space got stronger, interstellar space were different to providing a commentary. If we’re un- and there was a marked increase in those taken by Voyager 1 back in 2012. lucky and it’s cloudy, we’ll offer you a the number of galactic cosmic rays This is likely due to the being at a conciliatory cup of tea after the talk (high-energy particles which originate different phase of its 11-year cycle. (with perhaps some more astro-in- from extreme objects far from our “There is still a lot to learn about Solar System). the region of interstellar space imme- formation in the lecture theatre for Voyager 1 (Voyager 2’s sister diately beyond the heliopause” said Ed those who want to stay on). mission) left the heliosphere back in Stone, a Voyager project scientist at 2012. But unfortunately for mission Caltech. Several planned missions in scientists, Voyager 1 was unable to the coming years will be tasked with measure the strength of the Solar examining the heliopause in more de- If you have any questions, suggestions Wind (one way of measuring the edge tail, including the Interstellar Mapping or comments about the IoA Open of the Solar System) due to a previous and Acceleration Probe (IMAP), due to Evenings please contact Matt Bothwell at instrument failure. Luckily, Voyager launch in 2024. [email protected].

@cambridge_astro facebook.com/InstituteOfAstronomy 2 — IOA PUBLIC OPEN EVENING — 19 December 2018

Most distant Solar System object found

A TEAM of astronomers have discov- ered the most distant Solar System object seen to date. Officially named 2018 VG18, but appropriately known Credit: Scott Sheppard/David Tholen as “Farout” to its discoverers, the new object is situated 120 astronomical An image of the new object, named “Farout”, captured with the Subaru telescope in Hawaii. units (AU) from the Sun. One AU is defined as the distance between the at the Carnegie Institution for Science take a few years to fully determine its Earth and the Sun – around 150 million in Washington DC. orbit,” said Sheppard. “But it was found km. For reference, the outermost planet Many of the small bodies lurking in in a similar location in the sky to the () orbits at around 30 AU, and the distant outskirts of the Solar Sys- other known extreme solar system ’s average distance from the Sun is tem seem to be influenced by a massive objects, suggesting it might have the around 40 AU. yet-unseen planet, nicknamed Planet X. same type of orbit that most of them So, orbiting at a distance of 120 AU, However, it is early days for Farout, and do. The orbital similarities shown by Farout is much, much farther away astronomers haven’t yet measured its many of the known small, distant solar than the familiar planets of the inner orbit with enough accuracy to know if system bodies was the catalyst for our Solar System. All that is known about it too shows signs of being under the original assertion that there is a dis- Farout so far is its size (around 500km influence of a massive missing planet. tant, massive planet at several hundred across) and its colour: pinkish, imply- “2018 VG18 is much more distant astronomical units shepherding these ing that Farout might be covered in ice. and slower moving than any other smaller objects.” The team was led by Scott Sheppard, observed solar system object, so it will Did a nearby supernova cause an ancient extinction?

nearby supernova. A new study, led by Brian Thomas at Washburn University in Kansas, con- ducted computer simulations to work out how such a supernova would affect our planet. “I was expecting there to be very little effect at all,” Melott said. The Simeis 147, a supernova results were therefore surprising! Not remnant estimated to be only would the light from the super- around 40,000 years old. be bright enough to light up the Credit: Rogelio Bernal Andreo night sky for weeks, the team found that radiation and harmful cosmic rays from the explosion could have disrupt- A NEW study has suggested that a that this gas originated in a series of ed Earth’s climate enough to cause an minor mass extinction event on Earth supernovas in the Scorpius-Centaurus extinction event. around 2.6 million years ago (the Plio- cluster of stars around 2-3 million years “There really hasn’t been any good cene-Pleistocene extinction) may have ago (when the cluster was just 130 light explanation for the marine megafaunal had a cosmic culprit: a nearby superno- years from Earth). extinction,” Melott concluded. “This va, which could have bathed the Earth Secondly, the geological record could be one.” in radiation. shows a large deposit of Iron-60 around There are a few lines of evidence 2.6 million years in the past. Being that point to this conclusion. Firstly, radioactive, any Iron-60 that formed the timing lines up. Our Solar System along with the Earth would be long Joke of the Week is in the middle of a cloud of hot gas gone by now. So the 2.6 million year old around 500 light years across, known deposit must have a cosmic origin – What do you get if you cross Santa Claus with as the ‘Local Bubble’. It is thought such as raining down on Earth after a an alien? A U-F-Ho-Ho-Ho!