NASA detects 'heartbeat' of pint-sized star-sucker
No this isn't a photo – it's an artist's take on X-ray emissions from a "heartbeat" black hole
Smallest black hole ever found – and maybe ever will be
By Rik Myslewski in San Francisco 16th December 2011 23:11 GMT
In what is turning out to be one of the best months ever for black-hole fanbois, a team of Dutch, Italian, and US space boffins has detected the "heartbeat" of what appears to be teensiest, weensiest black hole ever discovered.
"Just as the heart rate of a mouse is faster than an elephant's, the heartbeat signals from these black holes scale according to their masses," said University of Amsterdam's Diego Altamirano, referring to [ http://www.nasa.gov/topics/universe/features/black-hole-heartbeat.html ] the newly discovered IGR J17091-3624 and a similar object, GRS 1915+105.
While GRS 1915+105 is a black-hole pipsqueak with a mass only 14 times that of our sun, IGR J17091-3624 is tinier still, estimated to be a mere three times as massive as Ol' Sol, a size that is close to the theoretical "mass boundary" at which the formation of a black hole becomes possible.
The "heartbeat" to which Altamirano was referring is the X-ray pattern emitted by the binary system that includes the pint-sized black hole – it gets that nickname because of its resemblance to an electrocardiogram of a heart at work. GR J17091-3624 and GRS 1915+105 are the only such systems yet discovered that evidence this pattern.
The beating of J17091-3624's heart is caused by intermittent X-ray bursts as gas is sucked from its companion star and forms a disc around the black hole, where it's heated by friction to millions of degrees, hot enough to emit X-rays. The variations in these emissions, scientists believe, take place at the black hole's event horizon.
"We think that most of these patterns represent cycles of accumulation and ejection in an unstable disk, and we now see seven of them in IGR J17091," said Tomaso Belloni of the Brera Observatory in Merate, Italy.
The black-hole boffins have identified 12 such variations in GRS 1915+105, which typically last between seconds and hours. "Identifying these signatures in a second black hole system is very exciting," said Belloni.
The system's heartbeat was recorded by the ever-reliable Rossi X-ray Timing Explorer (RXTE [ http://heasarc.nasa.gov/docs/xte/xhp_glance.html ]), a satellite that was launched in December 1995. RXTE was designed to have a lifetime of two years, although the scientists working with it had hoped it would last for for five. Needless to say, they underestimated its durability.
Tod Strohmayer of NASA's Goddard Space Flight Center and RXTE's project scientist is understandably jazzed about his geriatric satellite's discovery. "Until this study," he said, "GRS 1915 was essentially a one-off, and there's only so much we can understand from a single example. Now, with a second system exhibiting similar types of variability, we really can begin to test how well we understand what happens at the brink of a black hole."
Exactly where that brink is remains in doubt, however. While RXTE and other space missions have poinpointed J17091-3624's coordinates – it's in the direction of the constellation Scorpius [ http://www.topastronomer.com/StarCharts/Constellations/Scorpius.php ] – its distance hasn't yet been nailed down, with the best estimates ranging from 16,000 to over 65,000 light-years.
NASA has discovered the tiniest, most pathetic black hole in the universe Dec 18, 2011 * Related Stories Best look yet of Comet Lovejoy’s slingshot around the Sun
F6 .. Science in review: 10 biggest stories for 2011 Thursday, 22 December 2011
by Becky Crew Cosmos Online
Two of the largest black holes currently known to exist have been discovered. This is an artist's conception of stars moving in the central regions of a giant elliptical galaxy that harbors a supermassive black hole.
Credit: Gemini Observatory/AURA artwork by Lynette Cook
SYDNEY: From overachieving neutrinos to Earth-like planets and test tube sperm: here are the top 10 science stories of 2011, as chosen by the editors at COSMOS. Plus, we reveal which stories were particularly popular in the office.
The discovery of an unknown species of bird-like dinosaur from China raised serious questions over the place of Archaeopteryx in the evolutionary tree. Was Archaeopteryx really the earliest and most primitive bird as we've always thought?
All year, South Africa and Australia has been jostling to win the right to build the world's largest radio telescope, the Square Kilometre Array, which will cost A$2 billion and will have 10,000 times the survey speed of current radio telescopes?.
To the dismay of the scientific community, tn the early hours of July 14, Greenpeace protestors gained illegal entry into an experimental CSIRO operated farm near Canberra and destroyed a crop of genetically modified wheat.
We're inching closer and closer to the dream of having wearable invisibility cloaks à la everybody's favourite teenage wizard, with the development of a new cloaking device made from heated up carbon nanotubes that can replicate the 'mirage effect' seen in nature.
The genome of an Aboriginal Australian was sequenced for the first time this year, which revealed the journey taken by early humans out of Africa before they spread across the globe.
Could this be the discovery that renders the male sex obsolete? Mature, functional sperm was created in a laboratory dish for the first time earlier this year - a feat that has eluded reproductive biologists for more than 50 years.
Two of the largest black holes known to exist have been discovered, and we know how much you enjoy how we speak about light years in relative terms, so they're a mere 300 million light years away from Earth.
It was the announcement that had scientists and journalists piling into a tiny lecture room at CERN with the hopes that maybe the existence of the elusive, hypothetical Higgs boson had been confirmed. Not yet, said CERN, but they've come closer than ever to finding it.
The experiment took everyone by surprise - physicists reported that neutrinos can travel faster than light which, if true, would blast a hole in Einstein's theory of relativity. Additional tests are being carried out before anything can be said for sure.
A rocky world called Gliese 581g orbiting a nearby star was said to be the first planet outside our Solar System to meet key requirements for sustaining life, which is just as well, because in 2009, COSMOS teamed up with the Australian government, NASA and the CSIRO to run a 13-day campaign called Hello From Earth .. http://www.hellofromearth.net/ .. to send messages from the public to this very planet.
What an incredible find - fossilised compound eyes in half-a-billion-year-old rocks in South Australia. This was the first time scientists realised that vision evolved rapidly with the arrival of early modern animals.
In what could be the cutest experiment of the year, rats gave up a treat of chocolate chips in order to set their cage mate free. Those rats deserve all the chocolate chips in the world.
Another Kepler milestone: Astronomers find two Earth-sized planets orbiting the same star!
Astronomers have achieved a big milestone in the search for another Earth: the two smallest confirmed planets ever found orbiting another star… and they’re both about the size of Earth!
Artist’s illustration of the Kepler-20 planets with Earth and Venus for size comparison.
The planets are called Kepler-20e and Kepler-20f, .. http://www.nasa.gov/mission_pages/kepler/news/kepler-20-system.html .. and as you can see by the illustration above they are very close to the same size as our home world: 20e is about 11,100 km (6900 miles) in diameter, and 20f about 13,200 km (8200 miles) across. For comparison, Earth has a diameter of 12,760 km (7930 miles). This makes them the smallest confirmed exoplanets seen orbiting another star! The previous record holder was Kepler-10b, .. http://kepler.nasa.gov/Mission/discoveries/kepler10b/ .. which has a diameter about 40% bigger than Earth’s.
To be clear: while these planets are the size of Earth, they are nowhere near Earth-like. The star, Kepler-20, is very much like the Sun, though a bit smaller and cooler (and 950 light years away). However, both planets orbit the star much closer than Earth does; 7.6 million km (4.7 million miles) and 16.6 million km (10.3 million miles), respectively. This is so much closer that both planets must have surface temperatures far hotter than ours, 760°C and 430°C (1400°F and 800°F). Even on the "cooler" planet Kepler-20f, it’s hot enough to melt tin and zinc.
So don’t start packing your bags to visit, even if you could spare a few million years to get there via rocket (950 light years is a bit of a hike). I’ll note that we don’t know the masses of these planets either. I’ll explain that in a moment, but given their sizes it’s expected they’ll have masses similar to Earth’s.
So this is very exciting! For one thing, it shows that Kepler can indeed find planets the size of Earth orbiting distant stars. That right away is fantastic; that’s the main goal of Kepler in the first place.
For another, it shows that our solar system is not entirely unique. We do know of several other stars hosting solar systems of their own, but those planets tend to be very massive; they’re easier for us to find. Since Kepler-20e and f are so close to Earth-sized, this is a big achievement.
And we’re still not done: there are three other planets in the Kepler-20 system! The others are much larger than the Earth: named Kepler-20b, c, and d, they have diameters of 24,000, 40,000, and 35,000 km (15,000, 24,600, and 22,000 miles); smaller than Uranus and Neptune, but still pretty hefty. We do have the masses for them: 8.7, 16.1, and about 20 times the mass of the Earth. Call them "super-Earths" if you like.
All these planets huddle pretty closely to their star; the orbit of Kepler-20f, the farthest from the star, would still fit comfortably inside the orbit of Mercury! Oddly, the configuration is very different than our own solar system. While ours has the lower-mass planets close in and the bigger ones farther out, in the Kepler-20 system they alternate, going big-little-big-little-big.
So how do we know all this? The Kepler observatory .. http://kepler.nasa.gov/ .. is in space, staring at one patch of sky all the time. There are 100,000 stars in its field of view, including Kepler-20. If there are planets orbiting a star, and we see the orbit of that planet edge-on, then once per orbit the planet directly passes between us and the star, blocking its light a little bit. This is called a transit, and the bigger the planet, the more light it blocks. That’s how the sizes of the five planets were found.
As these planets orbit their star their gravity tugs on it, and that can be measured by carefully observing the star’s light. As a planet pulls it one way and then another, there is a very small Doppler shift in the starlight, .. http://blogs.discovermagazine.com/badastronomy/2011/05/05/dense-exoplanet-gets-the-lead-out-and-in/ .. and the amount of that shift tells us how hard the planet is tugging on the star, and that in turn depends on the mass of the planet. Only the three bigger planets in the Kepler-20 system pull hard enough for us to measure, which is why we don’t have the masses of 20e and 20f; they’re too small to measure.
Also, to be clear, we don’t have direct images of these planets (those pictures above are drawings). They were found indirectly by how they affected their star. But these methods are now tried-and-true, and the existence of these five planets has been confirmed. They’re real.
This is a fantastic discovery for so many reasons: the smallest planets found orbiting another star, the first Earth-sized planets seen by Kepler, both in the same solar system, and in such an oddly-configured and compact system at that. This means we need to think more about how such planets can form, of course, since it’s so weird… but no matter what, it means we’re that much closer to finding the ultimate goal: an Earth-sized planet orbiting a Sun-like star in that star’s habitable zone, where liquid water can exist.
Every time I hear news like this, I wonder how much longer we’ll be waiting to hear that news… and I strongly suspect it won’t be too much longer.
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