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On Tuesday, I blogged about the theoretical work done in the early 1970s by Martin Rees, and others, which proposed that there may be a supermassive black hole at the centre of our Galaxy and most spiral galaxies.

What about the observational evidence?

In the early 1980s two teams set about observing the orbits of stars near Sgr A*. The two teams, working separately, were at UCLA and The Max Planck Institute For Extra-terrestrial Physics (MPE). The team at UCLA is known as the UCLA Galactic Center Group, the team at the MPE doesn’t have a snazzy name, but their website can be found here. Gradually, over many years, each of the two teams has determined the orbits of several dozens of stars, and hence have been able to use the laws of gravity to determine the mass of the enclosed mass which the stars are orbiting.

Below is an image of Sgr A* taken by the MPE team using the NACO near-infrared camera on the VLT with adaptive optics. The entire image is only 30 arc seconds across.

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A combined H, K and L-band near infrared image of the Galactic Centre obtained by the NACO camera on the VLT using adaptive optics. This image is from the MPE website.

Here is a paper, published in 2009, entitled “Monitoring Stellar Orbits Around the Massive Black Hole in the Galactic Center”, published by the MPE group in The Astrophysical Journal. Here is a link to the paper.

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This paper, published in The Astrophysical Journal in 2009, is one of several showing overwhelming evidence for a supermassive blackhole at the centre of the Milky Way galaxy.

In this paper, entitled “The Galactic Center massive black hole and nuclear star cluster”, Reinhard Genzel (the director of the MPE) and colleagues summarise the evidence from their studies of their being a supermassive blackhole at the centre of the Milky Way, with a calculated mass of about 4.4 million solar masses. Here is a link to the paper.

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In a paper entitled “The Galactic Center massive black hole and nuclear star cluster”, Genzel etal. summarise their finding that the Galaxy harbours a massive black hole with a mass of about 4.4 million solar masses.

The UCLA group published this paper “Measuring Distance and Properties of the Milky Way’s Central Supermassive Black Hole With Stellar Orbits”, in 2008 in The Astrophysical Journal (here is a link to the paper). In it,they calculate the mass of the supermassive black hole to be 4.5 million solar masses, with an error of plus or minus 0.4 million solar masses.

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Ghez etal. (2008) find the  mass of the supermassive black hole to be 4.5 million solar masses, slightly higher than the MPE group, but well within the errors of the two groups’ measurements.

The mass of this black hole is about 4.45 million times the mass of the Sun (the two groups calculate different masses, with the UCLA group calculating about 4.5 million solar masses, the MPE group about 4.4 million solar masses). Let us assume it is 4.5 million solar masses, just to round up to the nearest half a million solar masses.

As some of you may know, blackholes are observable in certain ways. They clearly affect the orbit of nearby objects (this is how the UCLA and MPE teams have garnered the evidence for the supermassive blackhole), but also the accretion disk which usually surrounds a blackhole has very hot gas spiralling into the blackhole. This very hot gas emits radiation as a blackbody, so most of it comes out in the X-ray part of the spectrum due to the very high temperature of several millions of Kelvin.

But, a blackbody will also radiate at other wavelengths (see my blog here to remind yourself of the shape of a blackbody curve), so such accretion disks will also radiate visible light, infrared light, and even radio emission. The question then arises, is it possible to observe the accretion disk way in towards the event horizon of the Galaxy’s supermassive blackhole?

I will answer that question next week.

There is now overwhelming evidence that our Galaxy harbours a supermassive black hole at its centre. Not only that, but the Hubble Space Telescope has discovered that all spiral galaxies harbour supermassive black holes at their centres, and the mass of that black hole is directly proportional to the mass of the galaxy in which it resides. The reasons for this are still unclear.

The idea of supermassive black holes driving the prodigious energy output at the centre of some galaxies was first proposed by Edwin Salpeter in a 1964 paper. Salpeter is probably better known for his work on the initial mass function of star formation, but in this paper (follow this link to read it), Salpeter proposed that supermassive black holes may be the energy source behind the then newly discovered quasars.

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In a 1964 paper, Edwin Salpeter (possibly more famous for his work on the initial mass function of star-formation) was the first to propose supermassive black holes as the energy source of the newly-discovered quasars (or QSOs).

In 1971, Donald Lynden-Bell and Martin Rees wrote an important paper entitled “On quasars, dust and the galactic centre”, (follow this link to the paper). It was the first paper to suggest that our own Galaxy, the Milky Way, may harbour a supermassive black hole at its centre.

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The possibility that our Milky Way harboured a supermassive blackhole at its centre was first proposed by Donald Lynden-Bell and Martin Rees in 1971.

Another important paper entitled “Accretion onto Massive Black Holes” was written in 1973 by Pringle, Rees and Pacholczyk (follow this link), who considered the observable effects that matter accreting onto a (super)massive black hole would have.

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In a 1973 paper, Pringle, Rees and Packolczyk considered the observable effects of the accretion of matter onto a supermassive black hole.

Pringle etal. draw two main conclusions, the second of which is possibly the more important; that material falling onto a (super)massive black hole will emit a huge amount of radiation.

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The two main conclusions of the Pringle etal. (1973) paper.

In a 1974 review article in The Observatory entitled “Black Holes”, Martin Rees further stated the arguments for supermassive black holes at the centres of galaxies.

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In a 1974 review article in The Observatory, Martin Rees wrote that “a black hole might lurk in the centres of most galaxies.”. 35-40 years later, he was shown to be correct.

He stated (my highlight)

If we regard quasars as hyperactive galactic nuclei, then a black hole might lurk in the centres of most normal galaxies.

How prescient were these words!

Later in the same year, radio astronomers Bruce Balick and Robert Brown discovered a compact radio source in the constellation Sagittarius. They announced their result in a paper entitled “Intense Sub-Arcsecond Structure in the Galactic Center” (here is a link to the paper).

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In 1974, Bruce Balick and Robert Brown used the Very Large Array of radio telescopes in New Mexico to discover a compact radio source at the centre of the Milky Way. We now call this source Sagittarius A*

Using the Very Large Array of radio telescopes in New Mexico, Balick and Brown found a sub-arcsecond radio source at both 2695 MHz (11cm) and 8085 MHz (3.7cm). We now call this source Sagittarius A*, and it is believed to be where the Galaxy’s supermassive black hole resides. Here is their image obtained at 2695 MHz (at right, the image at left is the base-line coverage in the u-v plane, the interferometry plane of the array).

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Bruce Balick and Robert Brown discovered a sub-arcsecond radio source in the constellation Sagittarius. We now call this source Sagittarius A*. Their discovery was made at 2695 MHz (which corresponds to a wavelength of 11 centimetres)

Since these discovery observations, Sagittarius A* (or Sgr A* as it is often known) has been observed at many other wavelengths (but not in visible light, the dust extinction is too great). For example, here is a combined infrared and X-ray image.

The supermassive black hole located 26,000 light years from Earth in the center of the Milky Way.

A composite infrared and X-ray image of Sagittarius A*

And, here are some images taken by the SPIRE camera on the Herschel Space Observatory at 250, 350 and 500 microns.

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Images of Sagittarius A* taken by the SPIRE camera on the Herschel Space Telescope. The observations are at (from left to right) 250, 350 and 500 microns.

Later this week I will blog about the observational evidence for this compact object being a supermassive black hole.

The second weekend of the 2017 6 Nations is over, and I think it is fair to say that this year is on course to be one of the most exciting 6 Nations in history. After Ireland running rampant in Italy, England narrowly beat Wales in Cardiff by scoring a converted try in the last 4 minutes, and France narrowly beat Scotland in Paris. It seems that 5 of the 6 nations are pretty evenly matched, so most of the games look like they could be very close.

Italy v Ireland

Ireland went to Rome seeking to make amends for their loss last week to Scotland. They won comfortably by 63 points to 10, running in 9 tries. Italy were woeful, not to take anything away from Ireland, and it has re-opened the debate as to whether Italy deserve to be in the 6 Nations at all. An idea which has been floating around for a while is that there should be relegation from the 6 Nations, with the second tier European countries like Romania and Georgia in a play-off against the bottom placed country in the 6 Nations table to see who should make up the sixth place the following year.

But, one needs to bear in mind that, when France joined the then 4 Nations to make the 5 Nations (back in 1910) they barely won any matches for well over a decade. Their initial record in the 5 Nations was worse that Italy’s current record in the 6 Nations, but they went on to be one of the best teams in the world. So, in my opinion we should give Italy more time to bring their rugby up to speed, not expel them yet.

Wales v England

This was, for most people, the big game of the weekend. Wales and England have been playing each other since 1881, and had played each other a total of 129 times prior to this weekend. With the record at 60 wins to England, 57 to Wales and 12 drawn matches, long-term they could not be more evenly matched.

It was a cracking match; at no point were the two sides more than 5 points apart, and the ferocity and competitiveness on display was something to behold. This was the best Welsh performance since beating England in the world cup in September 2014. And, it is a match that Wales could have won and should have won. At half time we were 13-8 up, and between 50 and 75 minutes we were, in my opinion, by far the better side. England looked rattled, and at 74 minutes the score was 16-14 to Wales.

With England threatening the Welsh try line, Dan Biggar made a superb interception and broke up field. Isolated, he kicked ahead and a desparate English defence kicked it into touch, giving Wales an attacking line-out in the English 22. But, we fluffed it, and this for me was the incident which lost us the match. With only 5 minutes on the clock, we could have won the line-out, and played out the remaining 5 minutes in England’s 22, or even gone for a drop goal.

But, instead, we found ourselves back under pressure near our own try line. The ball came back to centre Jonathan Davies, who kicked up-field. But, rather than kicking into touch, he kicked in-field, something the Welsh team had been doing all afternoon. It was a crazy decision; he should have belted it into the stands and given the Welsh forwards as much time as possible to slow the game down and regain their breath for the line-out. Instead, George Ford caught Davies’ in-field kick, passed it to Owen Farrell who spun a long pass to winger Elliot Daly. Daly outclassed a poor Alex Cuthbert to score in the corner, and Farrell slotted the conversion to rub salt into the wound.

We went from being in control and 16-14 ahead to losing 21-16.

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Wales lost to England 21-16 in Cardiff, with England snatching a try with only 4 minutes left on the clock to break Welsh hearts.

As I say, in my opinion not only were Wales the better team, but it is a match that we lost rather than England winning it. Poor decision making, particularly in the last 5 minutes, cost us what would have been a memorable win over a very good England team. On the plus side, it was the closest this England team under Eddie Jones has been pushed during his 14 months in charge. And, Wales are finally beginning to develop their game beyond the Warren-ball of the last too many years. I hope we can back it up by winning in Scotland in two weeks’ time.

France v Scotland

This was another close fought match, with France sneaking it 22-16. Scotland had their chances, and they are a much improved side. They have so many good back-line players that they look dangerous from anywhere on the field, and it is great to see them so competitive again. They are going to be a tough prospect for Wales in what is our next game.

Round 3 of the 6 Nations

The 6 Nations now takes a slight hiatus; the next round of matches are in a fortnight’s time rather than this coming weekend. On Saturday 25th February, Wales head up to Murrayfield to take on Scotland, with the KO at 14:25. The second match of the day is Ireland at home to France, KO is 16:50. On Sunday 26th, England host Italy at Twickenham, with the KO at 15:00. I will preview these matches closer to the time.

Later today Wales take on England in the 2017 6 Nations. Unfortunately for Wales, this is only our second game of the championships, and I don’t think we are up to speed yet. Yes, we won convincingly in Italy last Sunday, but our first half display showed many of our weaknesses. England, on the other hand, battled to a win against France, and with only 10 minutes to go they looked like they would lose. So, which side will be better prepared for today’s clash?

Wales have two injury worries to deal with. Both Dan Biggar (outside-half) and George North (wing) suffered injuries against Italy. They have been named in the starting 15, but Rob Howley may find that they fail final fitness tests and do not play. Should Dan Biggar not start, then Sam Davies will start in his place. Davies is a more attacking outside-half than Biggar, and personally I think that he gets the backline moving better. But, if Biggar is fit I would prefer to see him start, with Davies coming on at about 60 minutes as the game opens up for the last quarter.

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Both Dan Biggar and George North are doubts for today’s clash with England. They have been named in the starting 15, but both suffered injuries against Italy last Sunday.

The other impact player which Wales will hope to bring on during the last quarter is our outstanding number 8 Taulupe Faletau. He has been injured, so has not played much rugby in the last few months. But, I am sure that he has kept himself fit enough to put in a barn-storming 20 minutes and I’m in no doubt that he will be brought on as impact replacement.

England have only won two of their last seven visits to Cardiff, so their coach Eddie Jones will be doing all he can to tell his players that they should not fear the Millennium Stadium. But, if you have ever been to this cathedral of rugby you will know that it is intimidating. England have opted to leave the roof open, which does reduce the noise in the stadium somewhat. But, with 74,500 supporters, most of them shouting for Wales, do not underestimate how intimidating that will be for England. And, with England unbeaten under Eddie Jones, there is nothing Wales would like more than to be the first country to break this winning streak. Beating England is not the be-all and end-all of Welsh rugby, but it is very sweet when we do beat our larger, noisier neighbour.

The head-to-head between Wales and England is almost tied. They have played each other 129 times. England have won 60, Wales 57, with 12 matches being drawn. Will it be 61 to 57, or 60 to 58 after today? We will know in a few hours……

DERE ‘MLAEN CYMRU!!!! / COME ON WALES!!!!

On Monday (6th February) the sad news was announced that the great South African scrum-half Joost van der Westhuizen (JVD) had died at the age of 45. In 2011 JVD was diagnosed with motor neurone disease. Over the next few years he did much to raise awareness of and money to conduct research into this cruel disease; showing the same fighting spirit which led to his being one of the true greats of rugby of any era.

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Joost van der Westhuizen was one of the greats of world rugby. In 2011 he was diagnosed with motor neurone disease. He died on Monday (6th February) at the age of 45.

 

I heard it said this week that JVD was the first muscular scrum  half and the first large scrum half (a position traditionally played by smaller men). I would disagree with both of these statements. I grew up watching Gareth Edwards, often considered the greatest Welsh rugby player, who was a strong, muscular and dynamic scrum half. The only thing he lacked was height, but in the early 1980s Terry Holmes played for Wales, and he was 1m87, the same height as JVD. So, I would not agree that JVD was the first muscular scrum half or the first scrum half who was as large as a back-row forward.

It is sometimes easy when someone has died far too early to overstate their greatness. But, JVD was a great scrum half, there is no denying that. He was an inspiration to his team, and someone that other teams feared. In the 1995 World Cup, he was the first player to successfully tackle Jona Lomu, who had run rampant through every team against which the All Blacks had played.

But, JVD showed his true greatness in the way with which he dealt with his motor neurone disease (MND). He took it as an another challenge, and spent the rest of his life raising awareness of MND and raising money for researching in to it. In the video below is an excerpt from an interview which JVD did with the BBC in late 2014 or early 2015. It was replayed on Monday evening, the day of his death. Listen to his final words, when he is asked whether his MND may be considered a “blessing”

In a way I am glad I had MND. I now know what life is about

RIP Joost van der Westhuizen.

The first weekend of the 2017 6 Nations is over, and it threw up a few surprises. On Saturday, Scotland beat Ireland in Edinburgh, and England came close to being beaten by France at Twickenham. Yesterday (Sunday), Wales won comfortably in Rome, but not before Italy gave Wales a bit of a scare in the first half.

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Wales beat Italy in Rome by 33-7 to get their 2017 6 Nations campaign off to a positive start.

Scotland v Ireland

The biggest upset of the first weekend was Scotland’s surprise win over Ireland. Ireland had gone into this 6 Nations being tipped by many pundits as the favourites to win the tournament. They were not favourites with the bookmakers, but that is because few of them can see beyond England. But, with many (most?) rugby experts, Ireland were felt to be the team most likely to win the title this year.

Scotland, however, had different ideas. In a blistering first half they went 14-0 up with two wonderful tries. They then scored a third try, and were 21-5 up before Ireland slotted a penalty to bring the half-time score to 21-8. The second half saw Ireland surge back to go into the lead 22-21. Scotland teams of the last few years would have folded at this point, but this Scotland team showed glimpses in the autumn of having reached a level not seen by any Scotland team since the 1990s. They scored two more penalties and deservedly won a stunning match 27-22.

England v France

It has, of course, become a total cliché that you never know which France will turn up, and this match against England was a perfect example of why that cliché is so true. France came out with all guns blazing, and were by far the better team for most of this match. It was 9-9 at half-time, but England were lucky that France didn’t didn’t go into half-time with a comfortable lead. France then went up 16-12 in the second half, and I believe a more experienced and better composed French team would have closed out the match. But, inexperience combined with some astute substitutions by England saw them score a converted try to snatch the game 19-16. Their unbeaten run under Eddie Jones continues.

Italy v Wales

Wales usually start each run of games poorly, so having Italy as the first match was a bit of relief as they are still the easiest side in the 6 Nations to beat. However, Wales have lost in Italy, twice I think since Italy joined the annual tournament. And, during the first half Wales could not convert their possession and territory into points. I was a little baffled that, so early in the match, we turned down kickable penalties to go for touch with the aim of scoring a try. I think this was a mistake so early in the match, and Italy went into half time with a 7-3 lead, even though Wales had dominated.

The second half was much better for Wales. At 50 minutes Rob Howley replaced both props, and suddenly Wales were in the ascendancy. One of the Italian props was sin-binned for dropping to his knee in a scrum, and Wales ran in two tries during the time that Italy were down to 14 men. With some 5 minutes to go George North ran from his own 22 to score Wales’ third try, and the possibility was on to score a fourth try and win a bonus point. Liam Williams came very close in the dying seconds, but failed to ground the ball so the match ended 33-7. It was a comfortable win, but I would not say that Wales were that impressive. We should have cut loose in the second half as Italy became more and more disorganised.

Next weekend

I will preview next weekend’s matches properly on Friday, but it sees Ireland go to Italy, Scotland go to France, and England come to Wales. For me, the question is whether England’s relatively poor performance against France is a good or a bad thing for Wales. Some times sides come back stronger after a defeat, and I am sure had England lost against France they would be coming down to Cardiff all fired up to make amends for their defeat. As it is, they scraped a win without deserving it and putting in their worst performance under Eddie Jones. Does this mean that they will come down to Cardiff with their confidence dented, or with a feeling that they can win in Cardiff without playing that well?

As for Wales, we won comfortably in Rome but it was a stuttering performance. We looked very good in the last 20 minutes, and were the better team in the first quarter and the third quarter of the match, but during the second quarter Italy were better than us. We failed to convert lots of chances in the first half, but during the second half we did a lot better in this regard. As even Jeremy Guscott, the ex-England centre, said on TV last night, if the best players in Wales’ side play the kind of game which they are capable of playing we should beat England. Unfortunately, they have not shown that kind of consistency of play for over 3 years now. It will be a fascinating encounter.

 

Tomorrow (Saturday 4th of February) sees the start of the annual 6 Nations rugby competition. Despite the attempts of the southern hemisphere’s Rugby Championship to increase its appeal, there are few who would disagree that the 6 Nations is the greatest and most intensely contested tournament in World rugby. The 2017 6 Nations sees England start as both defending champions and favourites, and this despite Ireland’s autumn test series which saw them beat New Zealand, Australia and South Africa. Wales, quite deservedly, start as third favourites behind England and Ireland, which is where I would place them too.

England are not only defending champions, but also they won the 2106 6 Nations with a Grand Slam. Very few sides have won back-to-back Grand Slams, so England will be hoping that they can achieve this rare feat. They are also unbeaten since Eddie Jones took over after their disastrous showing in the 2015 World Cup; so each of the other 5 nations will be looking to get that first win under his leadership. England’s opening match is a home one against France. France used to be perennial contenders for the 6 Nations crown, but have fallen badly behind Wales, England and Ireland in the last few years. Few expect them to cause an upset at Twickenham tomorrow.

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The 2017 6 Nations starts tomorrow (Saturday 4th of February). Wales’ first match is an away match to Italy on Sunday, followed the following Saturday (11th) by a home match against England.

Wales start their 6 Nations campaign on Sunday with an away match against Italy. No away match is easy in the 6 Nations anymore, and Wales have lost a few times in Italy. But, of all the away matches to start with, one against Italy is probably the most favourable. We have gone to Italy before and racked up points, and if we manage to do that on Sunday it will be a great start for us. Sadly, we usually start any campaign poorly, so I suspect that we will scrape a win against Italy, but it will not be a convincing one.

Our second match is against England in Cardiff on Saturday 11th of February. It would be a fairytale if we could be the first country to beat England under Eddie Jones’ leadership, and if this match were third of fourth or fifth in the campaign I would fancy our chances. But, I am not sure that we will be firing on all cylinders by the second match, and although I hope that we will win I fear a home defeat could well be on the cards.

Wales are, of course, going into this 6 Nations under the leadership of interim manager Rob Howley, as Warren Gatland is on leave to prepare for the summer’s Lions’ tour to New Zealand. We also won three of our four autumn tests under Howley, something that we had not done since 2004. But, we did not win any one of those three matches in a convincing fashion, and England and Ireland currently look streets ahead of us. But, at this level the margins are very very fine.

The Welsh squad certainly have the talent to be as good or better than England. In my opinion we have better players than England, but we are not functioning at the same level as they are as a team. The question is, can Howley iron out those little problems which were so apparent in the autumn series and see us get back to the level of play we showed under him in the 2013 6 Nations? Remember, that is the season when England came to Cardiff chasing a Grand Slam in the last game of the 6 Nations, and we annihilated them 30-3.

In some 8 days’ time, the game against England will be over and we will know if we are back to anything like that kind of form again.

Here is Wales’ schedule for the 2017 6 Nations. All times are GMT, not the local time (in Rome or Paris, which are one hour ahead of GMT).

  • Sunday 5th February – Italy v Wales (KO 14:00 GMT)
  • Saturday 11th February – Wales v England (KO 16:50 GMT)
  • Saturday 25th February – Scotland v Wales (KO 14:25 GMT)
  • Friday 10th March – Wales v Ireland (KO 20:00 GMT)
  • Saturday 17th March – France v Wales (KO 14:45 GMT)

COME ON WALES!!!! DERE ‘MLAEN CYMRU!!!!