In the show this time, we talk to Dr Alastair Edge about active galaxy cluster centres, Dr Bob Watson tells us about the cosmic microwave background polarisation reults from Planck and BICEP2 in this month's JodBite, and your astronomical questions are answered by Dr Iain McDonald in Ask an Astronomer.
JodBite with Dr Bob Watson
Dr Bob Watson works in the Planck collaboration, analysing the most accurate measurements ever made of the cosmic microwave background (CMB). This radiation provides the best known evidence that the Universe started with the Big Bang, as it seems to have been streaming through the Universe since the time when the first atoms formed. Dr Watson looked at the information contained within the polarised part of the CMB, as measured by both Planck and the BICEP2 telescope. BICEP2 caused great excitement when its polarisation measurements seemed to provide strong evidence for inflation in the early Universe, but, as Dr Watson reveals, the Planck results told a different story. Planck's multi-frequency measurements showed that the special 'B-mode' polarisation pattern could be explained by dust in our own Galaxy that had not been subtracted from the background by the BICEP2 team. This gives future missions the opportunity to remove the effects of the dust, but the signal representing inflation is likely to be hidden deeper than previously suspected - assuming that it exists at all.
Interview with Dr Alastair Edge
Dr Alastair Edge, from the University of Durham, talks to us about galaxy clusters and their central galaxies, which at first glance appear a little 'weird' to astronomers. He explains how the flows of gas from the galaxy to the surrounding cluster and back again give it surprising properties, and induce a variability in the galaxy's brightness on the timescale of tens of years. One of the objects Dr Edge is particularly interested in is the elliptical galaxy NGC 1275 in the Perseus cluster, and he explains the reasons why in this month's interview.
Ask an Astronomer
Dr Iain McDonald answers your astronomical questions:
- Peter Carr writes: "Pulsars are often described as being like lighthouses, producing a beam of radiation that sweeps round as the star rotates. This implies that the beam is produced from a spot on the 'equator' of the star. Is that correct? What mechanism is thought to produce the beam?"
- Rob Peck says: "Professor Paul Crowther mentioned that there was no theoretical limit as to how big a massive star may become. It made me wonder about the environment at the centres of such massive stars. How large would a star need to be before a black hole was created at its core?"
Iain refers to some short movies that simulate a rotating black hole. - John Brooks asks: "Would the top and bottom of a black hole look similar? Or is a black hole not a sphere but maybe coin-shaped?"
- Philip le Riche says: "Since gravitational waves are extremely difficult to detect, I'm wondering just how much energy they might carry. If our eyes were as sensitive to gravitational radiation as they are to light, how bright would be?"
Odds and Ends
You probably know by now that there will be a solar eclipse visible in parts of the northern hemisphere, including all of Europe, on Friday the 20th of March. In the UK it'll be the most notable eclipse since August 1999! You'll only be able to see it in totality if you happen to be on either the Faroe (North Atlantic Ocean) or Svalbard (Arctic Ocean) archipelagos, but elsewhere there'll be some spectacular sights. You can check to see the time and details of the eclipse where you are. Make sure to protect your eyes by wearing eclipse glasses, or make a pinhole projector.
NASA's Dawn spacecraft arrived at the dwarf planet Ceres on the 6th of March, marking humanity's first visit to such an object. After spending 14 months exploring Vesta, Dawn made a two-and-a-half-year trip to the largest of the asteroids. It will now make infra-red observations of Ceres, exploring its composition to learn about the early Solar System.
NASA's Space Launch System (SLS) booster reached a new milestone this month by passing the first of two quality tests. These tests precede the booster being transported to Florida for the first SLS flight. This is the largest and most powerful booster to date and, in its two-minute burn time, it produced approximately 3.6 million pounds of thrust! This was the high-temperature test, where the booster was heated to 90° Fahrenheit before the test. The second test, scheduled for 2016, is the cold-temperature test, in which the booster will be cooled to 40° Fahrenheit before burning.Show Credits
| JodBite: | Dr Bob Watson and Mark Purver |
| Interview: | Dr Alastair Edge and Indy Leclercq |
| Ask An Astronomer: | Dr Iain McDonald and Mark Purver |
| Presenters: | Mark Purver, Christina Smith and Charlie Walker |
| Editors: | Ben Shaw, Mark Purver, Monique Henson and Charlie Walker |
| Segment Voice: | Tess Jaffe |
| Website: | Mark Purver and Stuart Lowe |
| Producer: | Mark Purver |
| Cover art: | The 1999 total solar eclipse, as seen from France. CREDIT: Luc Viatour / www.lucnix.be |