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This week 50 years ago
This week–
Black hole smashes heavyweight record DAVID SHIGA
A BLACK hole as heavy as almost 16 suns has set a new weight record for black holes that form from collapsing stars. Its discovery suggests that there may be even heavier ones lurking out there, spawned in the death throes of the universe’s most massive stars. When a very massive star ends its life, its outer layers explode outwards, forming a supernova, while its core collapses to form a black hole. There are limits to the size of the so-called stellarmass black holes born this way,
not least because there is only so much matter available from the parent star. Until now, all the black holes formed this way whose mass has been precisely measured turn out to weigh in at 10 suns or less. Some astronomers had proposed that this might be the upper limit via this route. Heavier black holes weighing millions of suns can be found at the centres of galaxies, but these are probably formed in a different, if still mysterious, way. At 15.7 times the sun’s mass, the newly measured object, called M33 X-7, has smashed through that tentative limit. It is also the
Climate change on the living Earth Public lecture Monday 29 October at 6.30pm Professor James Lovelock CH CBE FRS Admission free - no ticket or advance booking required. Royal Society events are frequently broadcast live on the web. Visit the video archive at www.royalsoc.ac.uk/live The Royal Society 6-9 Carlton House Terrace, London SW1Y 5AG Tel: 020 7451 2683 Email: [email protected] Registered Charity No 207043
18 | NewScientist | 20 October 2007
Observations from around the Earth suggest that even the gloomiest predictions of climate change from the 2007 IPCC report may underestimate the seriousness of the changes due this century. Professor James Loveock will discuss the consequences, particularly for the UK and Europe, and how we might respond whilst at the same time seeking a global solution.
first black hole to be discovered in an eclipsing binary: that is, it is orbiting a companion star in such a way that when seen from Earth it sometimes passes in front of the black hole, and vice versa. The companion star is itself a brute, some 70 times the sun’s mass. Jerome Orosz of San Diego State University in California and colleagues used the 8.2-metre Gemini North telescope at Mauna Kea, Hawaii, to work out the orbit precisely and pin down the black hole’s mass (Nature, DOI: 10.1038/ nature06218). For stars with a chemical composition similar to the sun, so much mass is blown away during their lifetime that only a small fraction remains when they die, so even the biggest could barely produce a 16-solarmass black hole. This slimmingdown process would be less efficient for stars made from relatively pure hydrogen and helium, which could explain how M33 X-7 was born so large, says astrophysicist Stanford Woosley of the University of California, Santa Cruz. That explanation is
“Till now, all black holes formed this way turned out to weigh in at 10 suns or less, which was thought to be the upper limit” plausible because the companion star appears to have just 10 per cent of the heavy-element impurities that the sun has. Team member Charles Bailyn of Yale University says purer stars that formed in the early universe may have spawned even larger black holes. “Those things would send most of their mass into a black hole,” he says, producing black holes with as much as 1000 times the sun’s mass. This raises the possibility that the supermassive black holes might have formed from the growth or merger of such massive collapsed stars. “They might make extremely massive black hole remnants that could be the seeds for these much more massive black holes,” he says. ●
THIS WEEK 50 YEARS AGO Home-made diamonds While the rest of the world has been craning its neck to catch a glimpse of Sputnik orbiting the planet, a group of scientists back on the ground have been looking the other way. Withdrawing from the mysteries of space, they have cast their minds down 240 miles into the depths of the Earth. There, the pressure is enormous and the temperatures believed to be higher than 5000 °F. And, in a sealed chamber which duplicates these conditions, this handful of scientists from General Electric’s metallurgical products department have aped nature and made diamonds. Sixty thousand carats were piled up in a tiny heap for sceptical news reporters to touch last week. They looked like grains of grey sand until they were picked up and held. Then they shone with lights of many colours. Although none could approach the size or sparkle of a finecut flawless gem, the man who led the team that created them said: “They are not imitation. They are all nature has produced, except in size.” Other people have tried to create diamonds in the past and failed; the first known attempt was in 1828. Just how the General Electric synthesis of the stones was accomplished cannot be disclosed because of a US federal law passed during the second world war which bans publication of patent information which could be helpful to an enemy nation. Diamonds fit this bill because much of the machining on aircraft, guns, shells, tanks, trucks and automobiles is done with cemented carbide tools sharpened by diamond grinding wheels. But whatever the synthetic process used to create the new diamonds, because the US currently imports as many as 10 million carats of natural stones – chiefly from the Belgian Congo and South Africa – the ability to create diamonds for industrial use makes both economic and strategic sense. From The New Scientist, 24 October 1957
www.newscientist.com
Black hole smashes heavyweight record DAVID SHIGA
A BLACK hole as heavy as almost 16 suns has set a new weight record for black holes that form from collapsing stars. Its discovery suggests that there may be even heavier ones lurking out there, spawned in the death throes of the universe’s most massive stars. When a very massive star ends its life, its outer layers explode outwards, forming a supernova, while its core collapses to form a black hole. There are limits to the size of the so-called stellarmass black holes born this way,
not least because there is only so much matter available from the parent star. Until now, all the black holes formed this way whose mass has been precisely measured turn out to weigh in at 10 suns or less. Some astronomers had proposed that this might be the upper limit via this route. Heavier black holes weighing millions of suns can be found at the centres of galaxies, but these are probably formed in a different, if still mysterious, way. At 15.7 times the sun’s mass, the newly measured object, called M33 X-7, has smashed through that tentative limit. It is also the
Climate change on the living Earth Public lecture Monday 29 October at 6.30pm Professor James Lovelock CH CBE FRS Admission free - no ticket or advance booking required. Royal Society events are frequently broadcast live on the web. Visit the video archive at www.royalsoc.ac.uk/live The Royal Society 6-9 Carlton House Terrace, London SW1Y 5AG Tel: 020 7451 2683 Email: [email protected] Registered Charity No 207043
18 | NewScientist | 20 October 2007
Observations from around the Earth suggest that even the gloomiest predictions of climate change from the 2007 IPCC report may underestimate the seriousness of the changes due this century. Professor James Loveock will discuss the consequences, particularly for the UK and Europe, and how we might respond whilst at the same time seeking a global solution.
first black hole to be discovered in an eclipsing binary: that is, it is orbiting a companion star in such a way that when seen from Earth it sometimes passes in front of the black hole, and vice versa. The companion star is itself a brute, some 70 times the sun’s mass. Jerome Orosz of San Diego State University in California and colleagues used the 8.2-metre Gemini North telescope at Mauna Kea, Hawaii, to work out the orbit precisely and pin down the black hole’s mass (Nature, DOI: 10.1038/ nature06218). For stars with a chemical composition similar to the sun, so much mass is blown away during their lifetime that only a small fraction remains when they die, so even the biggest could barely produce a 16-solarmass black hole. This slimmingdown process would be less efficient for stars made from relatively pure hydrogen and helium, which could explain how M33 X-7 was born so large, says astrophysicist Stanford Woosley of the University of California, Santa Cruz. That explanation is
“Till now, all black holes formed this way turned out to weigh in at 10 suns or less, which was thought to be the upper limit” plausible because the companion star appears to have just 10 per cent of the heavy-element impurities that the sun has. Team member Charles Bailyn of Yale University says purer stars that formed in the early universe may have spawned even larger black holes. “Those things would send most of their mass into a black hole,” he says, producing black holes with as much as 1000 times the sun’s mass. This raises the possibility that the supermassive black holes might have formed from the growth or merger of such massive collapsed stars. “They might make extremely massive black hole remnants that could be the seeds for these much more massive black holes,” he says. ●
THIS WEEK 50 YEARS AGO Home-made diamonds While the rest of the world has been craning its neck to catch a glimpse of Sputnik orbiting the planet, a group of scientists back on the ground have been looking the other way. Withdrawing from the mysteries of space, they have cast their minds down 240 miles into the depths of the Earth. There, the pressure is enormous and the temperatures believed to be higher than 5000 °F. And, in a sealed chamber which duplicates these conditions, this handful of scientists from General Electric’s metallurgical products department have aped nature and made diamonds. Sixty thousand carats were piled up in a tiny heap for sceptical news reporters to touch last week. They looked like grains of grey sand until they were picked up and held. Then they shone with lights of many colours. Although none could approach the size or sparkle of a finecut flawless gem, the man who led the team that created them said: “They are not imitation. They are all nature has produced, except in size.” Other people have tried to create diamonds in the past and failed; the first known attempt was in 1828. Just how the General Electric synthesis of the stones was accomplished cannot be disclosed because of a US federal law passed during the second world war which bans publication of patent information which could be helpful to an enemy nation. Diamonds fit this bill because much of the machining on aircraft, guns, shells, tanks, trucks and automobiles is done with cemented carbide tools sharpened by diamond grinding wheels. But whatever the synthetic process used to create the new diamonds, because the US currently imports as many as 10 million carats of natural stones – chiefly from the Belgian Congo and South Africa – the ability to create diamonds for industrial use makes both economic and strategic sense. From The New Scientist, 24 October 1957
www.newscientist.com