Gravitational Waves: One year on

It’s a year since the LIGO Scientific Collaboration, including the Gravitational Physics group here in Cardiff, announced the very first detection of gravitational waves. I’ve been working with the teams in Cardiff and internationally for a little over a year, and it’s been a rollercoaster.

The announcement day itself was, quite frankly, crazy – but a good kind of crazy (radio interviews, live TV interviews on the roof, videos, podcasts, press conferences etc.). Since then I’ve given a number of interviews, public talks and school workshops about the detection and it’s all still as amazing as it was a year ago.

A lot of that is because the numbers are so earth-shattering, for example:

It says something that to express the power you need not one but two non-standard expressions of magnitude (septillion and yotta) – though since “yotta” and septillion both mean 1024, I can’t help thinking that it might sounds better as a “yotta-yotta-Watt”!

I also took this opportunity to update the Gravitational Wave Catalogue I made a while ago (fullscreen version here). You can change the axes on the graph, and show more information about the detections.

As for the future, LIGO is currently in Observing Run 2 (“O2” for short). Nothing much to say at the moment, but an official announcement by the LIGO Scientific Collaboration on 28th January read:

The second Advanced LIGO run began on November 30, 2016 and is currently in progress. As of January 23 approximately 12 days of Hanford-Livingston coincident science data have been collected, with a scheduled break between December 22, 2016 and January 4, 2017. Average reach of the LIGO network for binary merger events have been around 70 Mpc for 1.4+1.4 Msun, 300 Mpc for 10+10 Msun and 700 Mpc for 30+30 Msun mergers, with relative variations in time of the order of 10%.

So far, 2 event candidates, identified by online analysis using a loose false-alarm-rate threshold of one per month, have been identified and shared with astronomers who have signed memoranda of understanding with LIGO and Virgo for observational followup. A thorough investigation of the data and offline analysis are in progress; results will be shared when available.

The “reach” of the LIGO is defined by its sensitivity – because more distant events are fainter and so harder to detect (meaning that a more sensitive detector network can detect more distant events. The reason for giving three distances for different mass pairings is because more massive binaries produce stronger signals so can be “seen” further away – historically the range of gravitational wave detectors has been stated as the 1.4+1.4 Msun mergers (i.e. two neutron stars).

In terms of scale a Mpc is a “megaparsec” (one million parsecs), which is about 3.26 million light years. The Andromeda Galaxy (our nearest large neighbour) is about 2.5 million light years (0.75 Mpc) away. The Virgo cluster of galaxies, the closest large galaxy cluster, is about 50 million light years (15 Mpc) away, so well within range of LIGO. Though do remember that the previous detections were much further away than that – at around 1 billion light years.

Pythagorean Astronomy: Star Attractions

Star Attractions. Image courtesy of National Museum, Cardiff

Image courtesy of National Museum Cardiff

Join Chris North and Edward Gomez as they discuss the month’s astronomy news. Not only were there two new NASA missions announced this month, but Space-X successfully returned to flight with their Falcon 9 rocket. Further afield, there are predictions of a pair of stars that are set to explode in a few years.

Being January, the National Museum in Cardiff hosted its annual public event celebrating all things space. With exhibits, demonstrations and shows for all ages, several thousand people attended “Star Attractions” and get to learn a bit more about astronomy and space. While we were there with a stand from the School of Physics and Astronomy, Chris spoke to a few people who were there to find out what they got out of it.

Originally broadcast on 30th January 2017 as part of Pythagoras’ Trousers on Radio Cardiff.

Pythagorean Astronomy: Assassin Supernova

artist's impression

Close-up of star near a supermassive black hole (artist’s impression) Image credit: ESO, ESA/Hubble, M. Kornmesser

When is a supernova not a supernova? The brightest supernova on record was discovered in 2015 by the All Sky Automated Survey for Supernovae (ASAS-SN). Named ASASSN-15lh, this remarkable event – what looked like a huge brightening of a star in a distant galaxy – was observed by many other telescopes, including the Hubble Space Telescope and the Las Cumbres Observatory network. With careful study, it became apparent that ASASSN-15lh was not quite what it seemed. Rather than being the explosion of a massive star, it is now thought that it was the final flash as a star was swallowed by a supermassive black hole.

This month, Morgan Fraser, from University College Dublin, and Las Cumbres Observatory’s Edward Gomez explain the story of this discovery – and rediscovery! We finish with a brief recap of 2016, and a look forward to 2017.

Originally broadcast on 19th December 2016 as part of Pythagoras’ Trousers on Radio Cardiff.

Pythagorean Astronomy: the GLEAM Survey


The GLEAM Survey

We’ve got a lot of news items to discuss this month. In the outer Solar System, Edward Gomez and I discuss the Cassini spacecraft, which has made its final major orbital manoeuvre, and the Juno spacecraft, which has had a few issues getting into its main science orbit. Further from home, we’ve got the first “official” star names from the International Astronomical Union, and the discovery of the roundest known star.

Our main guest this month is Dr Natasha Hurley-Walker, based at the International Centre for Radio Astronomy Research (ICRAR) at Curtin University. Natasha works on the Murchison Widefield Array, and has produced GLEAM: an all-sky image of the sky at radio wavelengths at very high resolution and in a wide range of radio “colours”, or wavelengths. This gives us a better understanding of some of the most energetic processed taking place in the centres of nearby galaxies, but the end goal is somewhat further afield. Natasha tells me all about the MWA, the GLEAM project, and even how you can view it – on the interactive GLEAMoscope site (or using the GLEAM Android app)

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

Pythagorean-Astronomy: ExoMars and Galaxies

A lot has happened this month – ESA got a spacecraft into orbit around Mars, but sadly lost the Schiaparelli lander, China launched two new taikonauts to their space station, and the Swarm mission uncovered details from Earth depths. Edward Gomez and I discussed these, and more, this month (though before the full nature of the status of the Schiaparelli lander were available).

In other astronomy news, a scientific paper hit the headlines claiming to have worked out how many galaxies there are in the observable Universe. Cardiff colleague Professor Steve Eales told me quite what he thought of this latest result…

Originally broadcast on 24th October 2016 as part of Pythagoras’ Trousers on Radio Cardiff.

Pythagorean Astronomy: Rosetta and OSIRIS-REx

Rosetta_at_comet_67P_landscape_1280This month sees the start of one mission and the end of another. NASA’s OSIRIS-REx mission launched at the start of the month to go and study asteroid Bennu, and even bring back a sample to Earth.

Meanwhile, the end of the month sees the finale of ESA’s Rosetta mission, which has spent two years studying comet 67P/Churyumov-Gerasimenko. With stunning images accompanied by fascinating results from other instruments, not to mention the plucky little Philae lander, Rossetta has been one of the most exciting missions of recent years.

This month, the Open University’s Professor Monica Grady tells me about comets, asteroids, and these two exciting missions.

Originally broadcast on 26th September 2016 as part of Pythagoras’ Trousers on Radio Cardiff.

[Cross posted from our Cardiff University School of Physics and Astronomy engagement site]

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