Pythagorean Astronomy: Mission Juno


Artist’s Impression of a Juno and Jupiter. Credit: NASA

In July 2016 NASA’s Juno spacecraft completed its five year journey to the planet Jupiter. On board is a suite of instruments and experiments that will provide exquisite insight into the history of our Solar System’s largest planet.

The process of Jupiter’s formation is a long-standing mystery that planetary scientists have been trying to answer for decades. As the University of Leicester’s Dr Leigh Fletcher explains, Juno will make careful measurements of Jupiter’s gravitational field and yield crucial information about its interior.

Originally broadcast on 28th July 2016 as part of Pythagoras’ Trousers on Radio Cardiff.

Pythagorean Astronomy: the Origins of Black Holes

GRO J1655-40 is the second so-called 'microquasar' discovered in our Galaxy. Microquasars are black holes of about the same mass as a star. They behave as scaled-down versions of much more massive black holes that are at the cores of extremely active galaxies, called quasars. Astronomers have known about the existence of stellar-mass black holes since the early 1970s. Their masses can range from 3.5 to approximately 15 times the mass of our Sun. Using Hubble data, astronomers were able to describe the black-hole system. The companion star had apparently survived the original supernova explosion that created the black hole. It is an ageing star that completes an orbit around the black hole every 2.6 days. It is being slowly devoured by the black hole. Blowtorch-like jets (shown in blue) are streaming away from the black-hole system at 90% of the speed of light.

Artist’s Impression of a black hole in a binary star system. Credit: ESA/Hubble

[cross-posted from Cardiff Physics Outreach blog]

On 15th June 2016 the LIGO collaboration released more detections of gravitational waves. As with the first detection, announced back in February, these gravitational waves were emitted by pairs of black holes, spiralling together and merging,

But of course, those black holes need to come from somewhere, and in this case it’s thought to be the deaths of some of the most massive stars in the Universe. To understand more about the deaths of massive stars, and the formation of black holes, I talked to Professor Stephen Smartt, from Queen’s University Belfast, who’s been on the hunt for black holes.

Originally broadcast on 30th June 2016 as part of Pythagoras’ Trousers on Radio Cardiff.

Pythagorean Astronomy: New worlds


Artist’s impression of the Kepler spacecraft

This month’s focus is on two different stories, but both involving the same spacecraft: Kepler. Edward Gomez and I discuss a result from the outer edge of our Solar System, regarding the icy world that goes by the catchy name of “2007 OR10”. By combining information from the Kepler Spacecraft, now in the second phase of its mission with a partially-functioning spacecraft, with results from the Herschel Space Observatory, astronomers have made a new estimate of its size. Continue reading

Breakthrough Starshot

Breakthrough StarshotEarlier this week we heard the announcement of a new project from the “Breakthrough Initiatives”. The group is led by Yuri Milner, a Russian entrepreneur apparently named after Yuri Gagarin, along with Stephen Hawking and Mark Zuckerberg, and with support of an advisory panel of astronomers, theoretical physicists, space scientists, engineers and business leaders. The new initiative, Breakthrough Starshot, has the goal of sending a fleet of tiny spacecraft to the nearest star system. It gathered a fair bit of attention, at least for 24 hours—BBC Radio Wales even asked me to chat to them about it on Good Evening Wales. Continue reading

Pythagorean Astronomy: To Mars – and Beyond!

[Cross-posted from the Cardiff Physics Engagement blog]

March 2016 saw the launch of the first part of Europe’s two-part mission to Mars. The mission, called ExoMars, comprises the “Trace Gas Orbiter” – the part that’s just launched – and a large rover, which launches in 2018. The orbiter will sniff the atmosphere to test for evidence of past  – or maybe even present – life. Elsewhere in the world of astronomy, this month has also seen the discovery a cluster of “monster stars”, and the most distant galaxy ever seen. I chatted to Edward Gomez and Tim Davis, a relatively new arrival here in Cardiff, about these discoveries.

Originally broadcast on 31st March 2016 as part of Pythagoras’ Trousers on Radio Cardiff.

Could we get rid of leap years?

It probably didn’t escape your notice that yesterday was 29th February – a date that comes round but once every 4 years. The reason for having leap years is explained in detail by Phil Plait on his Bad Astronomy blog (which is actually quite good). It’s essentially because the Earth’s rotation and the Earth’s orbit around the Sun aren’t quite in sync. Although a year is usually 365 days long, the Earth actually takes around 365.25 to get to the same place in space around its orbit. (It’s not exactly 365.25, and Phil Plait explains the details so I’ll defer to him.) Continue reading

Pythagorean Astronomy: The Voice of Einstein

[Cross-posted from the Cardiff Physics Engagement site]

Unless you’ve been under a bush for the past month, you can’t have missed what could be described the news of the Century – the first direct detection of gravitational waves. This month, I speak to Edward Gomez about what this discovery means, and catch up with some of the gravitational physicists here in Cardiff, Andrew Williamson, Frank Ohme and Lionel London. They tell me quite how sensitive the LIGO instruments are, and how gravitational waves are the voice of Einstein.

Originally broadcast on 25th February 2016 as part of Pythagoras’ Trousers on Radio Cardiff.

What would a gravitational wave sound like up close?

LIGO Sensitivity

Actual sensitivity of the LIGO detectors (H1 = Hanford, L1 = Livingston) at a range of frequencies. Image credit: LIGO Scientific Collaboration

The gravitational waves detected by LIGO tend to be in the frequency range of a few tens of Hertz to a few hundred Hertz. That’s not just a coincidence – it’s the frequency that LIGO is designed to operate at, and that in turn is because that’s the frequency at which it’s expected that some of the most common relatively powerful gravitational wave sources in the sky occur at. It’s also a feature of the design of the instrument, with higher frequencies limited by the laser power (more photons = more sensitive) and lower frequencies limited by things like the seismic isolation, thermal variations in the mirrors and suspension, and a range of other things. If you are interested in finding out more, you should play Space Time Quest.

Because frequency range to which LIGO is sensitive is is within the human hearing range, it’s possible to convert the gravitational wave signals directly into sound. They’re often a bit low, so it’s common to shift them up in frequency – it can be that’s not really any different from shifting infrared data into the visible to make an image we can actually, well, see! The result, in the case of GW150914 (the first gravitational wave detection) is a sound like the one below. Continue reading

GW150914 – birth of a monster

It can be hard to have missed the news last week of the detection of gravitational waves – an event known as GW150914 [GW = Gravitational Wave, followed by the date of the event in the YYMMDD format]. There was, understandably, an awful lot of excitement – it hit pretty much every major news network, and was even mentioned at the BAFTA award ceremony (which is how we know we’ve made it…)!

In the weeks in the run-up to the detection there was a lot of talk about analogies and comparisons of the event, and the black holes involved. But how is that all calculated, and how does that compare to other things in the Universe? Continue reading