Hungry black hole eats faster than thought possible

Date:

October 8, 2014

Source:

International Centre for Radio Astronomy Research (ICRAR)

Summary:

Astronomers have discovered a black hole that is consuming gas from a nearby star 10 times faster than previously thought possible. The black hole -- known as P13 -- lies on the outskirts of the galaxy NGC7793 about 12 million light years from Earth and is ingesting a weight equivalent to 100 billion billion hot dogs every minute.

 

Primary Image: This is a combined optical/X-ray image of NGC 7793. Inset image: This is a rendering of what P13 would look like close up.

Credit: Primary Credit: X-ray (NASA/CXC/Univ of Strasbourg/M. Pakull et al); Optical (ESO/VLT/Univ of Strasbourg/M. Pakull et al); H-alpha (NOAO/AURA/NSF/CTIO 1.5m); Creative Commons Attribution-No Derivative Works Insert Image credit: created by Tom Russell (ICRAR) using software created by Rob Hynes (Louisiana State University).

 

Astronomers have discovered a black hole that is consuming gas from a nearby star 10 times faster than previously thought possible.

The black hole -- known as P13 -- lies on the outskirts of the galaxy NGC7793 about 12 million light years from Earth and is ingesting a weight equivalent to 100 billion billion hot dogs every minute.

The discovery was published today in the journal Nature.

International Centre for Radio Astronomy Research astronomer Dr Roberto Soria, who is based at ICRAR's Curtin University node, said that as gas falls towards a black hole it gets very hot and bright.

He said scientists first noticed P13 because it was a lot more luminous than other black holes, but it was initially assumed that it was simply bigger.

"It was generally believed the maximum speed at which a black hole could swallow gas and produce light was tightly determined by its size," Dr Soria said.

"So it made sense to assume that P13 was bigger than the ordinary, less bright black holes we see in our own galaxy, the Milky Way."

When Dr Soria and his colleagues from the University of Strasbourg measured the mass of P13 they found it was actually on the small side, despite being at least a million times brighter than the Sun. It was only then that they realised just how much material it was consuming.

"There's not really a strict limit like we thought, black holes can actually consume more gas and produce more light," Dr Soria said.

Dr Soria said P13 rotates around a supergiant 'donor' star 20 times heavier than our own Sun.

He said the scientists saw that one side of the donor star was always brighter than the other because it was illuminated by X-rays coming from near the black hole, so the star appeared brighter or fainter as it went around P13.

"This allowed us to measure the time it takes for the black hole and the donor star to rotate around each other, which is 64 days, and to model the velocity of the two objects and the shape of the orbit," Dr Soria said.

"From this, we worked out that the black hole must be less than 15 times the mass of our Sun."

Dr Soria compared P13 to small Japanese eating champion Takeru Kobayashi.

"As hotdog-eating legend Takeru Kobayashi famously showed us, size does not always matter in the world of competitive eating and even small black holes can sometimes eat gas at an exceptional rate," he said.

Dr Soria said P13 is a member of a select group of black holes known as ultraluminous X-ray sources.

"These are the champions of competitive gas eating in the Universe, capable of swallowing their donor star in less than a million years, which is a very short time on cosmic scales," he said.

---

Story Source:
The above story is based on materials provided by International Centre for Radio Astronomy Research (ICRAR). Note: Materials may be edited for content and length.

 

NASA's SDO watches giant filament on the sun

Date:

October 3, 2014

Source:

NASA/Goddard Space Flight Center

Summary:

A snaking, extended filament of solar material currently lies on the front of the sun -- some 1 million miles across from end to end. Filaments are clouds of solar material suspended above the sun by powerful magnetic forces. Though notoriously unstable, filaments can last for days or even weeks.

A dark snaking line in the upper right of these images on Sept. 30, 2014, show a filament of solar material hovering above the sun's surface. NASA's SDO captured the images in extreme UV light – different colors represent different wavelengths of light and different temperatures of solar material.




Asnaking, extended filament of solar material currently lies on the front of the sun-- some 1 million miles across from end to end. Filaments are clouds of solar material suspended above the sun by powerful magnetic forces. Though notoriously unstable, filaments can last for days or even weeks.

NASA's Solar Dynamics Observatory, or SDO, which watches the sun 24 hours a day, has observed this gigantic filament for several days as it rotated around with the sun. If straightened out, the filament would reach almost across the whole sun, about 1 million miles or 100 times the size of Earth.
SDO captured images of the filament in numerous wavelengths, each of which helps highlight material of different temperatures on the sun. By looking at any solar feature in different wavelengths and temperatures, scientists can learn more about what causes such structures, as well as what catalyzes their occasional giant eruptions out into space.
Look at the images to see how the filament appears in different wavelengths. The brownish combination image was produced by blending two wavelengths of extreme UV light with a wavelength of 193 and 335 Angstroms. The red image shows the 304 Angstrom wavelength of extreme UV light.

---

Story Source:
The above story is based on materials provided by NASA/Goddard Space Flight Center. Note: Materials may be edited for content and length.

NASA's Swift mission observes mega flares from nearby red dwarf star

 

Date:

September 30, 2014

Source:

NASA/Goddard Space Flight Center

Summary:

On April 23, NASA's Swift satellite detected the strongest, hottest, and longest-lasting sequence of stellar flares ever seen from a nearby red dwarf star. The initial blast from this record-setting series of explosions was as much as 10,000 times more powerful than the largest solar flare ever recorded.

 

DG CVn, a binary consisting of two red dwarf stars shown here in an artist's rendering, unleashed a series of powerful flares seen by NASA's Swift. At its peak, the initial flare was brighter in X-rays than the combined light from both stars at all wavelengths under typical conditions.



On April 23, NASA's Swift satellite detected the strongest, hottest, and longest-lasting sequence of stellar flares ever seen from a nearby red dwarf star. The initial blast from this record-setting series of explosions was as much as 10,000 times more powerful than the largest solar flare ever recorded.

"We used to think major flaring episodes from red dwarfs lasted no more than a day, but Swift detected at least seven powerful eruptions over a period of about two weeks," said Stephen Drake, an astrophysicist at NASA's Goddard Space Flight Center in Greenbelt, Maryland, who gave a presentation on the "superflare" at the August meeting of the American Astronomical Society's High Energy Astrophysics Division. "This was a very complex event."
At its peak, the flare reached temperatures of 360 million degrees Fahrenheit (200 million Celsius), more than 12 times hotter than the center of the sun.
In April 2014, NASA's Swift mission detected a massive superflare from a red dwarf star in the binary system DG CVn, located about 60 light-years away. Astronomers Rachel Osten of the Space Telescope Science Institute and Stephen Drake of NASA Goddard discuss this remarkable event.
The "superflare" came from one of the stars in a close binary system known as DG Canum Venaticorum, or DG CVn for short, located about 60 light-years away. Both stars are dim red dwarfs with masses and sizes about one-third of our sun's. They orbit each other at about three times Earth's average distance from the sun, which is too close for Swift to determine which star erupted.
"This system is poorly studied because it wasn't on our watch list of stars capable of producing large flares," said Rachel Osten, an astronomer at the Space Telescope Science Institute in Baltimore and a deputy project scientist for NASA's James Webb Space Telescope, now under construction. "We had no idea DG CVn had this in it."
Most of the stars lying within about 100 light-years of the solar system are, like the sun, middle-aged. But a thousand or so young red dwarfs born elsewhere drift through this region, and these stars give astronomers their best opportunity for detailed study of the high-energy activity that typically accompanies stellar youth. Astronomers estimate DG CVn was born about 30 million years ago, which makes it less than 0.7 percent the age of the solar system.
Stars erupt with flares for the same reason the sun does. Around active regions of the star's atmosphere, magnetic fields become twisted and distorted. Much like winding up a rubber band, these allow the fields to accumulate energy. Eventually a process called magnetic reconnection destabilizes the fields, resulting in the explosive release of the stored energy we see as a flare. The outburst emits radiation across the electromagnetic spectrum, from radio waves to visible, ultraviolet and X-ray light.
At 5:07 p.m. EDT on April 23, the rising tide of X-rays from DG CVn's superflare triggered Swift's Burst Alert Telescope (BAT). Within several seconds of detecting a strong burst of radiation, the BAT calculates an initial position, decides whether the activity merits investigation by other instruments and, if so, sends the position to the spacecraft. In this case, Swift turned to observe the source in greater detail, and, at the same time, notified astronomers around the globe that a powerful outburst was in progress.
"For about three minutes after the BAT trigger, the superflare's X-ray brightness was greater than the combined luminosity of both stars at all wavelengths under normal conditions," noted Goddard's Adam Kowalski, who is leading a detailed study on the event. "Flares this large from red dwarfs are exceedingly rare."
The star's brightness in visible and ultraviolet light, measured both by ground-based observatories and Swift's Optical/Ultraviolet Telescope, rose by 10 and 100 times, respectively. The initial flare's X-ray output, as measured by Swift's X-Ray Telescope, puts even the most intense solar activity recorded to shame.
The largest solar explosions are classified as extraordinary, or X class, solar flares based on their X-ray emission. "The biggest flare we've ever seen from the sun occurred in November 2003 and is rated as X 45," explained Drake. "The flare on DG CVn, if viewed from a planet the same distance as Earth is from the sun, would have been roughly 10,000 times greater than this, with a rating of about X 100,000."
But it wasn't over yet. Three hours after the initial outburst, with X-rays on the downswing, the system exploded with another flare nearly as intense as the first. These first two explosions may be an example of "sympathetic" flaring often seen on the sun, where an outburst in one active region triggers a blast in another.
Over the next 11 days, Swift detected a series of successively weaker blasts. Osten compares the dwindling series of flares to the cascade of aftershocks following a major earthquake. All told, the star took a total of 20 days to settle back to its normal level of X-ray emission.
How can a star just a third the size of the sun produce such a giant eruption? The key factor is its rapid spin, a crucial ingredient for amplifying magnetic fields. The flaring star in DG CVn rotates in under a day, about 30 or more times faster than our sun. The sun also rotated much faster in its youth and may well have produced superflares of its own, but, fortunately for us, it no longer appears capable of doing so.
Astronomers are now analyzing data from the DG CVn flares to better understand the event in particular and young stars in general. They suspect the system likely unleashes numerous smaller but more frequent flares and plan to keep tabs on its future eruptions with the help of NASA's Swift.