Archive for the ‘Black holes’ Category

Reader mail: How far do black hole bullets blast out into space?

January 30, 2012 Leave a comment

As I reported on January 10, on or about June 3, 2009, enormous blobs of hot electrically charged matter were ejected from a black hole at about a quarter of the speed of light — roughly 75 million meters per second. Astronomers used a globe-spanning network of telescopes to observe the event, which occurred in a star system called H1743–322, about 28,000 light-years from Earth. A team of scientists reported the observations at the most recent meeting of the American Astronomical Society in Austin, Texas.

Geeked On Goddard reader John Conway contacted us with this excellent question:

“Interesting article. My thought: Do these “bullets” of gas dissipate over distance traveled, or do they keep going into space? If they were to come into contact with another celestial body, star, planet, black hole, whatever, what might be the result?”

I asked one of the astronomers who observed the goings-on at the black hole, James Miller-Jones, to explain.

“As the bullets move away from the black hole, they expand gradually,” Miller-Jones said. “Think of a bullet of material moving down a cone, whose apex is at the black hole.  If you take a slice through the cone to get a circular cross-section, that cross section gets bigger as you move away from the black hole. In the same way, the bullets are expanding as they move outwards.

“However, just because the bullets are too faint to detect doesn’t mean they have dissipated. They keep moving outwards, sweeping up or pushing aside the rarefied interstellar gas that is in the path of the bullets.Once they have swept up an amount of gas with a rest mass energy equal to their own initial energy (kinetic plus rest mass energy), they will slow down.”

And what would happen to a planet or star that got in the path of the bullets? Miller-Jones says it depends how close the object lies. In a binary star system (like H1743–322), the black holes co-orbits a nearby companion star, sucking gas off its surface. If the black-hole bullets hit the nearby star, “they would be expected to blast material off the surface of the donor.”

For more distant objects, the effect of the impact would be correspondingly less.

Then I asked Miller-Jones to estimate how far the bullets travel, and how fast. For example, if a black hole were located at the center of our solar system, how far outward would the bullets travel? Beyond Pluto? Beyond the distant shell of comets (the Kuiper belt) encircling the solar system? Or beyond the boundaries of the solar system to the vast space between our sun and the next star?

“We tracked these bullets way beyond [the distance from our sun to Pluto], and even beyond the Kuiper belt. Our last measurement put them about 120 times the sun-Earth distance from the black hole (120 astronomical units, or AU), whereas the Kuiper belt goes out to about 55 AU.

“In terms of how far the bullets travel before we can no longer detect them, that depends very much on the opening angle of the cone (how “wide” or “narrow” it is), the original energy of the outburst, and on how far away the source was.  With our most sensitive telescopes, and with the brightest bullets from the brightest black hole outbursts, we’ve tracked them out to about 0.1-0.2 light years from the black hole.  But we have no reason to think that they stopped there.”

Miller-Jones said that a blast of black-hole bullets would quickly leave the boundaries of its home solar system and enter interstellar space. For something like the bullets he and his colleagues studied, it would take them just a few days to exit a solar system about the size of ours, moving at about 25 percent of the speed of light.

Thanks to John Conway for his great questions.

OH AND DID I MENTION? All opinions and opinionlike objects in this blog are mine alone and NOT those of NASA or Goddard Space Flight Center. And while we’re at it, links to websites posted on this blog do not imply endorsement of those websites by NASA.



Why did a black hole blast star stuff into space at a quarter of light-speed on June 3, 2009? Here is what happened

January 10, 2012 3 comments

On June 3, 2009, in an X-ray binary star system far, far away. . .

We know the what of the extraordinary event that occurred in May 2009 around a distant black hole; we just don’t know the why of it, although the possibilities are pretty amazing.

At the 2012 American Astronomical Society (AAS) meeting in Austin, Texas, Gregory Sivakoff of the University of Alberta in Canada reported some astounding observations he and his colleagues accomplished using a globe-spanning array of radio telescopes and two NASA satellites.

The whole episode was a cosmic stroke of luck: The light from an event that happened some 28,000 years ago reached Earth just days before the global collaboration was scheduled to open for business. Goddard astrophysics writer Francis Reddy explains the details of the science today in a web feature story and animation.

Let’s start with the what: On or about June 3, 2009, enormous blobs of hot electrically charged matter were ejected from a black hole at about a quarter of the speed of light — roughly 75 million meters per second.

Next, the where: These black-hole “bullets,” as Reddy calls them in his web feature, were ejected from a binary star system. Called H1743–322, the  system lies about 28,000 light-years from Earth. NASA’s HEAO-1 satellite discovered it in 1977

In H1743–322, a black hole and a star orbit each other at close quarters, every few days. They are close enough that the black hole’s massive gravity draws a steady stream of material off its companion’s wispy surface. The hot electrically charged gas swirls around the edge of the black hole, forming a whirlpool-like “accretion disc.” As the gas accelerates to high speed, it radiates X-rays that satellites at Earth can detect.

“Some of the infalling matter becomes re-directed out of the accretion disk as dual, oppositely directed jets,” Reddy writes. “Most of the time, the jets consist of a steady flow of particles. Occasionally, though, they morph into more powerful outflows that hurl massive gas blobs at significant fractions of the speed of light.”

Years ago, Sivakoff’s colleague James Miller-Jones, currently based at the International Center for Radio Astronomy Research at Curtin University in Perth, Australia, conceived of a plan to mount a “multiwavelength campaign” to study the periodic outbursts that astronomers observe from X-ray binaries like H1743–322. They got their chance on May 22, 2009.

On that date, renewed activity around the black hole triggered the Burst Alert Telescope on NASA’s Swift satellite. Miller-Jones, Sivakoff, and the other members of the international team of observers were able to marshal three radio telescopes: the Very Long Baseline Array, the Very Large Array, and the Australia Telescope Compact Array. The team also drew on data from NASA’s Rossi X-ray Timing Explorer (RXTE) satellite (which was just switched off this week, by the way, after 16 years of meritorious service).

Using information from the telescopes and satellites, the scientists were able to reconstruct the events leading up to and following the ejection of black-hole bullets from the binary system. Sivakoff reported those findings today at the AAS meeting.

Now, finally, what about the “how” of this outburst? That’s not very clear yet.

In similar black hole binaries, Miller-Jones says, astronomers have measured ejections traveling 92 percent of the speed of light!  What process can shoot giant blobs of stuff out of the accretion zone of a black hole at such incredible speeds?

Sivakoff sketches out one possible explanation: Imagine knots of mass in the accretion disc, swirling around, getting closer and closer to the black hole. The disc is looped by powerful magnetic fields, which twist and tangle together as the disc rotates. When magnetic flux lines cross and connect, it could release enough energy to boost the black-hole bullets up and out of the disk.

“I think of a fairly stiff rope that is firmly to attached to the accretion disc,” Sivakoff explains. “As the disc spins, the rope is wound up, forming a sort of helix. Of course, there’s not one but many such ropes in an accretion disc. If two of those ropes touch — what astronomers call magnetic reconnection — lots of energy can be released. I like to envision ‘crossing the streams,’ a la Ghost Busters. This energy can accelerate particles, launching the bullet.”

There is another scenario, Miller-Jones says. Some scientists have proposed that what actually happens is that the inner edge of the accretion disc constricts, edging closer to the black hole’s “event horizon,” beyond which matter cannot escape. The magnetic and gravitational forces at this border region are extremely intense.

The forces could unleash a surge of material into the black hole’s paired jets, with a wavelike shock front ahead of it. “This causes particle acceleration,” Miller-Jones says, “and hence bright radio emission at this shock front.” So the bullets may actually be sudden surges in the jets, not discrete blobs.

But these explanations are just informed speculation at the moment. Additional multi-telescope observations could eventually provide enough clues to untangle the extreme physics that power black-hole bullets.

The team can only hope their recent stroke of luck holds out. Sivakoff says that the H1743–322  system conveniently started to flare up in late May 2009 — just as the team was preparing for the official opening of their observing window.

“Technically our observing was supposed to start in June 2009,” Sivakoff says. “But when this outburst went off a few days before our window was supposed to open up, we actually got permission to start observing earlier.”

So the discovery was the team’s inaugural run. “This was quite a trial by fire,” Sivakoff says.

OH AND DID I MENTION? All opinions and opinionlike objects in this blog are mine alone and NOT those of NASA or Goddard Space Flight Center. And while we’re at it, links to websites posted on this blog do not imply endorsement of those websites by NASA.

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The latest findings on the star-eating black hole

swift star eater

Phil Evans, an X-ray astronomer in England and frequent guest blogger for Geeked On Goddard, sends us this report on some exciting new findings of the NASA Swift observatory.

Back in March this year the Swift satellite detected a massive explosion in space. That in itself is nothing new. Indeed, it’s what Swift was designed to do. But, as I posted back in April, this one was a bit strange. Whereas Gamma Ray Bursts — Swift’s bread-and-butter (how cool, by the way, to be describing the most powerful explosions known in such an off-hand way) — explode and then fade away, this object flared up again, and again and then a fourth time, and even now is a bright source of X-rays.

So what was it? As I noted in that post, just 3 weeks after the event, a consensus has already formed that this was an extremely rare event: a star being torn apart by a black hole. Two papers have today (August 25) been published in the journal Nature, arguing for this interpretation, one of them led by Prof. David Burrows — the head of the X-ray Telescope (XRT) team on the Swift satellite. Here is a University of Leicester press release on the discovery.

The aftermath of such an event has been seen before (occasionally), but only well after the event, where all that can be seen are the last dregs of material being gobbled up: the black hole licking its lips, if you like. With Swift, for the first time, we’ve now seen the process actually starting, the black hole taking its first bite.

And, in doing so, we found something new: the light we saw can’t be explained by the standard models of a star being torn apart by a black hole. Incidentally, the black hole was a few million times more massive than the Sun!

Instead, the process must have resulted in the light coming out along a narrow ‘jet’ of material. Keen followers of Swift will notice that this is also how Gamma Ray Bursts emit their light.

Setting GRBs aside, jets from black holes at the center of a galaxy are a very common phenomenon, seen in Active Galactic Nucleii for example, but we’ve never seen such a jet actually ‘turn on’, until now. This once again highlights how awesome it is to working on Swift. At any moment I could be interrupted by an SMS from the spacecraft. Maybe it will be ‘only’ a huge explosion from the other side of the universe. Or maybe it will be something completely new.

Follow Phil Evans on twitter: @swift_phil

OH AND DID I MENTION? All opinions and opinionlike objects in this blog are mine alone and NOT those of NASA or Goddard Space Flight Center. And while we’re at it, links to websites posted on this blog do not imply endorsement of those websites by NASA.

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Phil Evans' Swift Universe: It's official — NASA's Swift satellite reveals a galaxy eating a star!

April 20, 2011 1 comment

Here is another guest post from Swift X-ray astronomer Phil Evans, “our man in the Midlands.” This time it’s an update about the galaxy that ate a star. — gogblog

Hungry? Fancy a snack? How about eating a star?

That, it seems, is what happened at lunchtime (in the UK) on March 28th. Here is an image of the burst from the Swift X-ray Telescope:


The Swift satellite detected what was at first thought to be a long Gamma Ray Burst (GRB), much like the 90-odd we detect every year although a bit on the long side. But then it “went off” again.

GRBs don’t do that. As it happens, I had just left to play football (alright, soccer if you insist) so I missed this second outburst, and I should point out that, although as your friendly blogger I’m telling this tale, it’s not my tale and I can’t claim any of the credit (alas!).

In fact, the first indication to me that this was a special event came that evening when, as I was replacing the grease filter in my cooker, my mobile phone rang. After degreasing myself enough to answer it I found that Dave Burrows, head of the Swift X-ray telescope team, asking if I could double-check some of the automatic results my code produces, because this object appeared to be weird.

(By the way, my twitter followers @swift_phil were among the first to learn that Swift had found something exciting and new!)

Weird it was. Gamma Ray Bursts get fainter over time. This didn’t, and hasn’t. Swift triggered on outbursts from it 4 times in 48 hours, and in the X-rays it remains bright today. (Back on April 7, NASA issued a press release about the event by science writer Francis Reddy.)

So what is it? Many astronomers have trained their telescopes on it in the past few weeks, taking data and reporting it quickly. Andrew Levan from Warwick University (UK) and collaborators used the Gemini telescope and found that the object was about 5 billion light years away! Further observations with infra-red and radio telescopes showed it to be right at the centre of it’s host galaxy.

Although only three weeks have passed since the event, papers are already appearing online. The consensus which is forming suggests that what Swift saw was a star straying too close to the super-massive black hole at the centre of its galaxy. The unfortunate star was torn apart and the pieces are now being gobbled up by the hungry black hole!

We’ve seen evidence for these events before — after the event — but Swift has captured yet another first: actually catching the black-hole perpetrating its massacre red-handed!

OH AND DID I MENTION? All opinions and opinionlike objects in this blog are mine alone and NOT those of NASA or Goddard Space Flight Center. And while we’re at it, links to websites posted on this blog do not imply endorsement of those websites by NASA.

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Planes, trains, bikes, and automobiles: Goddard engineer Kevin Boyce hits the road to make sure that a space observatory "made in Japan" makes it to space and sends home a pay-off for science

November 15, 2010 Leave a comment

KEVIN BOYCEAn earlier post featured the scary “spacecraft house of horrors” video about the testing torments suffered by our satellites before we send them to orbit. The video was hosted by our own Kevin Boyce, a spacecraft systems engineer. These days, Kevin is part of the international team working on the Japanese Astro-H mission. Here’s an account of his recent trip to Japan to help design an X-ray instrument.

How do you say in Japanese, “If you don’t succeed, try, try again”?

ASTRO-E was to be Japan’s fifth X-ray astronomy mission, but unfortunately the spacecraft was lost during launch on February 10, 2000.

Ok, try again. A follow-on mission, Astro-E2, launched successfully on July 10, 2005 from the Uchinoura Space Center in Japan. Soon after launch, the mission was renamed Suzaku.

The ill-fated Astro-E spaceraft

The ill-fated Astro-E spacecraft

Kevin Boyce can tell you all about it. Recently, as he was landing at Tokyo’s Narita Airport, it (almost) felt like coming home. “I’ve been here almost 40 times now,” he says. That started in the late 90’s with the ill-fated Astro-E project. Then he worked on the Astro E2/Suzaku mission that followed.

Now he’s an instrument systems engineer on one of the instruments on a new spacecraft called Astro-H. As he disembarks from the plane, he wonders if he should take the usual trains to the hotel, or take the bus this time. He decides on the bus option, and gets some cash from the ATM and buys a Matcha Creme Frappuccino from the Starbucks. Yes, America has left its mark here too.

artist concept of astro h

Artist's concept of Astro-H

Astro-H is Kevin’s third go-round with Japan’s space agency, JAXA, and Japan’s 8th space-based astronomy mission. It will launch into low-Earth orbit intending to trace the growth history of the largest structures in the universe, reveal the behavior of matter in extreme gravitational fields, determine the spin of black holes and study neutron stars, trace shock acceleration structures in clusters of galaxies, and investigate the detailed physics of galactic jets.

Um, is THAT all?

To do all that requires a gadget called a Soft X-ray Spectrometer (SXS), and Kevin is here in Japan to help shepherd the design of the instrument through a complex and high-stakes process that is difficult to carry out effectively solely by email or phone. It take as bunch of long plane rides and as many Matcha Creme Frappuccinos.

He’s in Japan for a week to participate in one of the quarterly Astro-H design meetings. “At these meetings all the various instrument teams report on their status, along with the spacecraft systems team,” he explains. “This generally lasts for two days.”

The rest of the time, the scientists and engineers pick apart the various sub-systems of the SXS. The devil is in the details, as the cliché goes. Miss a detail, and possibly buy lots of (expensive) trouble. Space missions take years and years and millions and millions of dollars.

SXS pushes X-ray observing technology. “Many of the people on both sides of the Pacific who are working on Astro-H, myself included, have been trying to get this technology operating on orbit since 1995,” he explains. “So it’s not just the trains and locations that make it feel like home. Some of my best old friends are here.”

This particular trip included a “hole.” Meeting took up Tuesday and Thursday, but Wednesday was a Japanese holiday, with no meetings scheduled. But you can’t fly home for a day. So what to do?

“Happily, some of our Japanese colleagues scheduled a bike trip into the mountains, and rented me a bike so I could join them,” he says. “We rode 50 kilometers up toward lake Yamanaka, climbing 700 meters in the process. And then back..”

[Read Kevin’s account of the bike trip on the NASA Blueshift blog.]

Snow-capped Mt. Fuji forms part of the background for a bike trip in Japan.

Snow-capped Mt. Fuji forms the background for a bike ride into the mountains.

After that ride, the design meeting was almost anticlimactic. But very important! The reason the X-Ray Spectrometer failed on Astro-E2 was basically due to incomplete communication between Goddard Space Flight Center and the Japanese during the design of the instrument. “This time we’re meeting much more often, and exchanging far more information, so that doesn’t happen again,” Boyce explains. “It’s not enough to exchange drawings and requirements documents. Each side really has to understand the whole instrument, and indeed the whole spacecraft system.”

So this time, Boyce attends the Japanese design meetings and reviews, and they attend the NASA reviews, and they all spend a lot more time on airplanes. But it’s still worth it, because Japan gets an instrument they don’t have the expertise to build at this point, and the US gets access to a whole mission’s worth of scientific data for just the cost of an instrument. Everyone wins.

“But only if we make it work,” Boyce says. “So four, five, six, or more times each year several of us hop on a plane for a week in our other homes here in Japan. Kampai!”

OH AND DID I MENTION? All opinions and opinionlike objects in this blog are mine alone and NOT those of NASA or Goddard Space Flight Center. And while we’re at it, links to websites posted on this blog do not imply endorsement of those websites by NASA.

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Phil Evans Swift Universe: how nature's strongest magnets power some of nature's brightest blasts

November 4, 2010 Leave a comment

A magnetar formed inside a collapsing massive star

A magnetar formed inside a collapsing massive star

Today “Swift Universe” guest blogger Phil Evans brings us some breaking news from the Gamma Ray Bursts 2010 conference in Annapolis, Maryland.

You’re all familiar with magnets. Well, two of my colleagues at the University of Leicester — Professor Paul O’Brien and his graduate students Antonia Rowlinson and Nicola Lyons — have announced evidence that some gamma-ray bursts (GRBs) are powered by stars called magnetars — super-strong magnets in space, if you like.

The idea is that, when the GRB goes off, the core of the dying star may not collapse straight to a black hole but instead could live for a couple of minutes as a rapidly rotating, magnetic neutron star called a magnetar. The magnetic field acts like a brake slowing the magnetar down and pumping its energy into the GRB, until after a few minutes the star has slowed down and collapses into a black hole.

Using data from the Swift satellite, my colleagues found that some GRBs show a period of constant brightness and then suddenly get really faint: just as the magnetar model predicts.

“So what?” you may ask. Well, GRBs are pretty much unique tools to study the early universe, and it’s the deaths of massive stars, some of which die as GRBs, which gives the universe the chemicals that you are I are made from. Getting a handle on the processes by which a star dies, and how it gives off its energy, is fundamental to using GRBs to study these matters. Showing that some GRBs are powered by magnetars is a big step forward.

One note of caution though: this isn’t “the” answer. While it seems to be the only explanation for some GRBS, in this same conference scientists from Berkeley university have shown using data from the Fermi satellite that the brightest GRBs can’t be powered by magnetars, but need a black hole right from the word go. Life’s never straightforward… but it’s often interesting!

Follow Phil as a Swift scientist on Twitter:  @Swift_Phil

Ron Cowen at Science News published a detailed write-up on the research.

OH AND DID I MENTION? All opinions and opinionlike objects in this blog are mine alone and NOT those of NASA or Goddard Space Flight Center. And while we’re at it, links to websites posted on this blog do not imply endorsement of those websites by NASA.

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Swift and the Star-Eaters of the Cosmos: A New X-ray Census Reveals Secrets of Supermassive Black Holes Burning, Burning Brightly

May 27, 2010 4 comments
When galaxies merge, the supermassive black holes in their centers can light up as brilliantly bright galactic beacons.

When galaxies merge, the supermassive black holes in their centers can light up as brilliantly bright cosmic beacons.

I once was blind, but now I see. Astronomers who study the supermassive black holes beaming brightly at the centers of galaxies will be singing this line from “Amazing Grace” now.

Researchers using the Swift orbiting observatory demonstrated a way to detect virtually every supermassive black hole actively feeding on gas in nearby galaxies.

These galactic grazers are known in astrogeekspeak as “active galactic nuclei.” Active indeed! Imagine a mob of King Henry the 8ths tearing into railcars full of mutton, spewing gristle and gnawed leg bones in all directions. Active galactic nuclei — let’s just call them AGNs — are messy, voracious eaters, too, but they spew energy instead of table scraps. They can radiate more energy than all the billions of stars in the galaxy combined.


Blogolicious Active Galactic Nuclei facts

  • Large galaxies contain supermassive black holes, with a million to a billion times the sun’s mass.
  • About 1% of the black holes are active galactic nuclei (AGNs), feeding on gas and emitting vast energy.
  • A survey by NASA’s Swift satellite finds that a quarter of AGNs are within merging galaxies or close pairs.
  • This is strong evidence for the theory that mergers trigger active galactic nuclei.


But I digress: back to Swift.

A team of scientists observed the local universe with Swift’s Burst Alert Telescope (BAT), which sees in so-called hard X-rays. Those are the energetic rays that zip through your body during a medical scan. And what the scientists observed is that about a quarter of AGNs are in merging galaxies or close pairs of galaxies grabbing gravitationally at each other.

[Imagine loud “ah hah!” sound emanating collectively from the world’s galactic astronomers.]

Theorists have always said that most AGNs are probably powered by mergers. As the galaxies come together, it stirs up gas, which feeds the black holes. Now we have the “hard” (X-ray) evidence, and 6 years worth.

A sample of mergers-with-AGN found in the Swift hard X-ray census.

A sample of mergers-with-AGN found in the Swift census.

Once upon a time, many astronomers would have said that AGNs were fueled by stars being torn part near the supermassive black hole. This provides years worth of fuel. The shredded star spirals down into the hole to near-light speed, releasing gobs and gobs of energy.

This hypothesis is not off the royal banquet table just yet. Some AGNs may, in fact, be star gobblers. But the Swift result sure makes it look like many — maybe most? — AGNs trace to mergers.

With the Swift survey, astronomers have the cosmic equivalent of a well-done national census. Like good census data, it allows us to spot statistical trends and convince ourselves they are real. In this case, the trend is that many galaxies with AGNs are merging or closely interacting.

In contrast, observing galaxies at energies lower than hard X-rays can throw off a census. That’s because lower-energy light can be absorbed by all the gas and stuff tossed around by a merger. As a result, you may miss some of the AGNs.  Also, the AGNs bright optical emission can get lost in the overall glow of stars in the galaxy.

Look for the findings in the June 20 issue of The Astrophysical Journal Letters, if you care to graze on some real astrophysics.

ROLL THE CREDITS . . . Gogblog gratefully tips his supermassive hat to the study’s lead author, Michael Koss, a graduate student at the University of Maryland in College Park. He explained the science to Gogblog and reviewed the post for accuracy. Other members of the team include Richard Mushotzky and Sylvain Veilleux at the University of Maryland, College Park, and Lisa Winter at the Center for Astrophysics and Space Astronomy at the University of Colorado in Boulder.

OH AND DID I MENTION? All opinions and opinionlike objects in this blog are mine alone and NOT those of NASA or Goddard Space Flight Center.

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