Ghosts Lurking from Massive Black Hole

June 4th, 2009 by Bellatrix

We all know that super massive black holes lurk in the center of galaxies. We know that they can have strong impacts on the surroundings; usually we can see how things are being impacted by the outflows of energetic particles being ejected from feeding black holes. However, if a black hole is not active and does not have jets usually we cannot see anything left over, any remnants from its energetic past. Well recently using the Chandra X-ray observatory a ghost of an eruption from a massive black hole has been observed and may have some interesting things to tell us.

The X-ray ghost, so-called because a diffuse X-ray source has remained after other radiation from the outburst has died away, is in the Chandra Deep Field-North, one of the deepest X-ray images ever taken. The source HDF 130 is over 10 billion light-years away a time when galaxies and black holes were forming at a high rate. Scientists think the X-ray glow from HDF 130 is evidence for a powerful outburst from its central black hole in the form of jets of energetic particles traveling at almost the speed of light. When the eruption was ongoing, it produced large amounts of radio and X radiation, but after several million years, the radio signal faded from view as the electrons radiated away their energy.

However, less energetic electrons can still produce X-rays by interacting with the pervasive sea of photons remaining from the cosmic background radiation. Collisions between these electrons and the background photons can impart enough energy to the photons to boost them into the X-ray energy band. This process produces an extended X-ray source that lasts for another 30 million years or so.

This is the first X-ray ghost ever seen after the demise of radio-bright jets. Astronomers have observed extensive X-ray emission with a similar origin, but only from galaxies with radio emission on large scales, signifying continued eruptions. In HDF 130, only a point source is detected in radio images, coinciding with the massive elliptical galaxy seen in its optical image. This radio source indicates the presence of a growing supermassive black hole.

The power contained in the black hole eruption was likely to be considerable, equivalent to about a billion supernovas. The energy is dumped into the surroundings and transports and heats the gas. Because they’re so powerful, these eruptions can have profound effects lasting for billions of years.

The data tells us that there should be many more such ghosts lurking around out there, especially if black hole eruptions are as common as are thought in the distant universe. This is a good discovery as it tells us that we do not have to catch a black hole in the act to witness the big impact they can have. Using Chandra I’m sure searches will begin for other such remnants. Once we have found more of them we can search for patterns in the data, see if there are commonalities in these eruptions or links between the data and other such things such as the mass of the black hole. 

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Old Method Finally Yields Results

June 1st, 2009 by Bellatrix

Modern develops in hunting for planets outside of our own solar system have yielded the discovery of well over a hundred different planets now. These newer methods include very new telescopes with the resolving power of being able to actually see an exoplanet, with which only 1 so far has been confirmed photographed, and other methods include using radial stellar velocity, or the Doppler effect, and the transit method. Now for the first time since its inception 50 years ago the method of astrometry has found an exoplanet.

The method of astrometry was first thought of 50 years ago to search for planets outside our solar system, called exoplanets. It involves measuring the precise motions of a star on the sky as an unseen planet tugs the star back and forth. But the method requires very precise measurements over long periods of time, and until now, has failed to turn up any exoplanets. This method is different from the more commonly used method of using the Doppler Effect or radial velocity of a star. Most exoplanets have been detected by watching for a wobble of a star, a gravitational tug from an orbiting planet due to the Doppler Effect. Astrometry also looks for a wobble but it is different  it measures the displacement the planets cause in their parent star’s apparent position on the sky, due to their mutual orbit around the center of mass of the system.

Two astronomers from NASA’s jet propulsion laboratory in California have been collecting data for the past 12 years from an instrument mounted on a telescope at the Palomar Observatory near San Diego. After looking at data from 30 different stars they have finally found what they were looking for: a planet surrounding the star VB 10. The planet itself is about 6 times the mass of Jupiter and an orbit a bit farther out making a cold Jupiter.  The star itself is quite small, a dwarf, at only 1/12 the mass of the sun. For a long time VB 10 was known as one of the smallest stars and now is the smallest star with a planet around it.  Because the star is so small, its planetary system would be a miniature, scaled-down version of our own. For example, VB 10b is located about as far from its star as Mercury is from the Sun. Any rocky Earth-sized planets that might happen to be in the neighborhood would lie even closer in.

The finding confirms that astrometry could be a powerful planet-hunting technique for both ground- and space-based telescopes. For example, a similar technique would be used by SIM Lite, a NASA concept for a space-based mission that is currently being explored. This is an exciting discovery because it shows that planets can be found around extremely lightweight stars. It seems that nature likes to form planets, even around stars quite different from our Sun. Now that it’s proven that this technique actually works and yields results it seems likely others might take it up, and more exoplanets will be found. One more tool in the planet hunter’s arsenal; one step possibly closer to finding a planet like our own.

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A Theoretical Link Found Between Radio Jets and Gamma Rays

May 6th, 2009 by Bellatrix

Scientists from the Max Plank Institute for Radio Astronomy in Bonn Germany using NASA’s Fermi Gamma Ray Space Telescope and the world’s largest radio telescope array have solidified a theoretical link between radio jets coming from the center of active galaxies and gamma ray bursts. This is a fine demonstration and use of new technology combined with an innovative use of existing technology.

Active galaxies are extremely bright galaxies which emitted oppositely directed jets of charged particles from their centers traveling near the speed of light.  Some, called Blazars, are especially bright because their jets are orientated along our line of sight.  These jets glow brightly in the radio part of the spectrum and in the 90’s it was hinted with the Chandra X-ray Observatory that they might emit in the higher energy parts of the spectrum as well. Astronomers believe these jets arise from matter that is falling into the central massive black holes of the galaxies, but the exact processes behind them is not well understood; which makes them the object of much study.

Now the Fermi telescope uses it’s Large Area Telescope, LAT, to scan the entire sky every 3 hours getting snapshots of the gamma ray bursts throughout the sky and monitor flares. Gamma ray bursts are the highest energy form of light below cosmic rays, and the origins of these gamma ray bursts is still undetermined; the objective of Fermi is to help clarify these origins. 

The new study was part of the MOJAVE program, which is a long-term study of the jets form active galaxies using primarily the VLBA. The VLBA is the National Science Foundation’s Very Long Baseline Array, a set of 10 radio telescopes located from Hawaii to the Virgin Islands and operated by the National Radio Astronomy Observatory in New Mexico.  Signals from these 10 different telescopes are combined and the array acts like a single enormous radio dish more than 8,500 kilometers across. The VLBA can resolve details about a million times smaller than Fermi and50 times smaller than any optical telescope.

Astronomers combined data from the VLBA and LAT. Active galaxies detected in the LAT’s first few months of operations generally possess brighter and more compact radio jets than galaxies the LAT did not see. Moreover, an active galaxy’s radio jets tend to be brighter in the months following any gamma-ray flares observed by the LAT.  A correlation was also found between active galaxies with the brightest gamma ray emission and those with the fastest jets.

The scientists were also able to use this data to study a phenomenon known as Doppler boosting. Doppler boosting makes radio-emitting blobs look brighter and appear to move faster than the speed of light due to the angle at which it is viewed and the fact the speed of the particles is close to the speed of light.  The VLBA data shows that the bigger the Doppler boost seen in a radio jet, the more likely it is that Fermi recorded it as a gamma ray source. Also, many objects found by Fermi to be extreme in gamma rays are broadcasting strong bursts of radio emission at the same time. 

All of this data points to the conclusion that the portion of an active galaxy’s radio jet closest to the galaxy’s center is also the source of the gamma rays.  These findings show us a very interesting and before unknown link between two “sides” of one object and possibly one process. This may bring astronomers one-step closer to solving two very large mysteries: the processes behind the jets and the exact processes or origins of gamma ray bursts. It could turn out to be quite nice and convenient if both questions could have the same answer, or an answer that comes from the same place. This new finding is also a demonstration of the use of the new technology of Fermi the space telescope that was designed just to study gamma ray bursts, a first of its kind, and the technology behind the VLBA, using standard radio telescopes in a new way to improve their usefulness

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Herschel/Planck New Launch Date Scheduled

April 15th, 2009 by Bellatrix

The largest mirror ever to be launched into space now has a set launch date.  The European Space Agency’s Herschel Space Observatory and Planck Satellite are set to launch into space May 6th. . Together these two pieces of equipment should be bringing in lots of new and exciting information about our own solar system and distant galaxies.

Sir Frederick William Herschel was a German born British astronomer from the 18th and 19th century. He was most famous for discovering the planet Uranus and discovering infrared radiation.  The Herschel Space Observatory will be the first to cover the full far infrared and sub-millimeter telescope.  The large mirror measures in at 3.5 meters; it’s a novel and advanced concept using 12 silicon carbide petals brazed together into a single piece. It is one of the major technological highlights of the mission.  Herschel will be investigating a large array of astronomical objects including: galaxy formation in the early universe and galaxy evolution, star formation and its interaction with the interstellar medium, chemical composition of atmospheres and surfaces of solar system bodies, and molecular chemistry across the universe.  Sounds like it has it work cut out.

The Planck Satellite will be going up with Herschel Observatory.  The satellite is named after the famous German physicist Max Planck who is considered the founder of quantum theory.  The satellite was designed to observe the anisotropies of the cosmic microwave background radiation, or CMB, over the entire sky using high angular resolution.  The mission is meant to improve upon the data collected from the well-known WMAP mission and will be used to test theories of the early universe and the origin of cosmic structure. 

Herschel and Planck will start their journey in space on board an Ariane 5 departing from Europe’s Spaceport in Kourou, French Guiana. Final preparations for the launch are now being made such as fueling the two satellites and filling Herschel’s cryostat (a vessel used to maintain cryogenic temperatures) with helium.  Once launched the two satellites will separate and be put into separate orbits around the second lagrangian point of the earth-sun system, a distance of about 1.5 million km’s from Earth.  Both satellites are part of the European Space Agency’s Horizons 2000 Scientific Programme, which consisted of about 15 satellite or telescope projects over the last 20 years including such other projects as Cluster, Huygens, XMM-Newton, and others.

The launch of these two satellites/observatories is exciting. They are new and advanced pieces of technology aimed at answering some large questions in astronomy today.  And are a fine example of astronomy goals and projects outside of the US.  So for now we just have to keep our fingers crossed and hold our breath for a successful launch and problem free start up. 

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