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Archive for October, 2013

Sagittarius A*: A Glimpse Of The Violent Past Of Milky Way’s Giant Black Hole

October 24, 2013 1 comment

Researchers using NASA’s Chandra X-ray Observatory have found evidence that the normally dim region very close to the supermassive black hole at the center of the Milky Way Galaxy flared up with at least two luminous outbursts in the past few hundred years.

This discovery comes from a new study of rapid variations in the X-ray emission from gas clouds surrounding the supermassive black hole, a.k.a. Sagittarius A*, or Sgr A* for short. The scientists show that the most probable interpretation of these variations is that they are caused by light echoes.

The echoes from Sgr A* were likely produced when large clumps of material, possibly from a disrupted star or planet, fell into the black hole. Some of the X-rays produced by these episodes then bounced off gas clouds about thirty to a hundred light years away from the black hole, similar to how the sound from a person’s voice can bounce off canyon walls. Just as echoes of sound reverberate long after the original noise was created, so too do light echoes in space replay the original event.

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ALMA Reveals Ghostly Shape Of ‘Coldest Place In The Universe’

October 24, 2013 Leave a comment

Credit: Bill Saxton; NRAO/AUI/NSF; NASA/Hubble; Raghvendra Sahai

Credit: Bill Saxton; NRAO/AUI/NSF; NASA/Hubble; Raghvendra Sahai

At a cosmologically crisp one degree Kelvin (minus 458 degrees Fahrenheit), the Boomerang Nebula is the coldest known object in the Universe – colder, in fact, than the faint afterglow of the Big Bang, which is the natural background temperature of space.

Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) telescope have taken a new look at this intriguing object to learn more about its frigid properties and to determine its true shape, which has an eerily ghost-like appearance.

As originally observed with ground-based telescopes, this nebula appeared lopsided, which is how it got its name. Later observations with the Hubble Space Telescope revealed a bow-tie-like structure. The new ALMA data, however, reveal that the Hubble image tells only part of the story, and the twin lobes seen in that image may actually be a trick of the light as seen at visible wavelengths.

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Unique Chemical Composition Surrounding Supermassive Black Hole – A Step Toward Development Of New Black Hole Exploration Method

October 24, 2013 Leave a comment

The Atacama Large Millimeter/submillimeter Array (ALMA) successfully captured a detailed image of high density molecular gas around an active galactic nucleus harboring a supermassive black hole. The observations at the highest ever achieved reveal a unique chemical composition characterized by enhancement of hydrogen cyanide (HCN) around the black hole. An research team thought a high temperature affected by the black hole caused this peculiar chemical properties. The team expect that this unique chemical properties can be used to find black holes hidden behind dust.

The research findings are presented in the article “Submillimeter ALMA Observation of the Dense Gas in the Low-Luminosity Type-1 Active Nucleus of NGC 1097” published in the Publication of the Astronomical Society of Japan, Vol. 65, of October 25, 2013.

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The Galactic Mosh Pit

October 23, 2013 Leave a comment

It is common knowledge that our Galaxy is permanently in motion. Being a barred spiral galaxy it rotates around the Galactic centre. It has now been discovered that our Galaxy, the Milky Way, also makes small wobbling or squishing movements. It acts like a Galactic mosh pit or a huge flag fluttering in the wind, north to south, from the Galactic plane with forces coming from multiple directions, creating a chaotic wave pattern. The source of the forces is still not understood however: possible causes include spiral arms stirring things up or ripples caused by the passage of a smaller galaxy through our own.

In this study, RAVE stars were used to examine the kinematics (velocities) of stars in a large, 3D region around the Sun – the region surveys 6500 light years above and below the Sun’s position as well as inwards and outwards from the Galactic centre, reaching a quarter of the way to the centre. Using a special class of stars, red clump stars, which all have about the same brightness, mean distances to the stars could be determined. This was important as then the velocities measured with RAVE, combined with other survey data, could be used to determine the full 3D velocities (up-down, in-out and rotational). The RAVE red clump giants gave an unprecedented number of stars with which it is possible to study 3D velocities in a large region around the Sun.

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Countdown To Launch Of ESA’S Billion-Star Surveyor

October 21, 2013 Leave a comment

ESA’s billion-star surveyor Gaia will be launched from Europe’s spaceport in Kourou on 20 November to begin a five-year mission to map the stars with unprecedented precision.

Gaia’s main goal is to create a highly accurate 3D map of our Milky Way Galaxy by repeatedly observing a billion stars to determine their positions in space and their movement through it.

Other measurements will assess the vital physical properties of each star, including temperature, luminosity and composition. The resulting census will allow astronomers to determine the origin and the evolution of our Galaxy.

Gaia will map the stars from an orbit around the Sun, near a location some 1.5 million km beyond Earth’s orbit known as the L2 Lagrangian point.

The spacecraft will spin slowly, sweeping its two telescopes across the entire sky and focusing their light simultaneously onto a single digital camera, the largest ever flown in space – it has nearly a billion pixels.

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Las Cumbres Observatory’s Unique Capabilities Help Identify First ProgenItor OF A Stripped-Envelope Supernova

October 18, 2013 Leave a comment

In June of this year, supernova iPTF13bvn, surprised astrophysicists by revealing its parentage. To date, Type Ib supernovae have appeared to come from nowhere. Type Ib supernovae explosions appear in surveys, but a search back through the archived data has so far resulted in no evidence of a progenitor, likely because they are simply too faint. A recently documented search for progenitors on a dozen Type Ib supernovae resulted in a dozen non-detections.

Because this is the first detected progenitor for a stripped envelope supernova (SNe Ib), the research was published in The Astrophysical Journal Letters.

Using radio, optical and spectroscopic sensors, a global team of astrophysicists led by Dr Yi Cao of Caltech began the work of tracking and characterizing the new supernova. The team from Las Cumbres Observatory Global Telescope, organized by D. Andrew Howell, gathered several spectra of the supernova as it evolved using the robotic FLOYDS spectrographs on 2-meter LCOGT telescopes in Hawaii and Australia. The LCOGT 1-meter telescope were activated by Dr. Melissa Graham to observe the SN continuously. Dr. Stefano Valenti reduced the data in real time from both the LCOGT 1-meter telescope network and the FLOYDS spectrograph, and worked with Caltech to analyze and characterize the data. The LCOGT data helped categorize the event as a Type Ib.

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NASA’s Hubble Sees Comet ISON Intact

October 18, 2013 Leave a comment

 

Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)

Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)

A new image of the sunward plunging comet ISON suggests that the comet is intact despite some predictions that the fragile icy nucleus might disintegrate as the sun warms it. The comet will pass closest to the sun on Nov. 28.

In this NASA Hubble Space Telescope image taken on Oct. 9, the comet’s solid nucleus is unresolved because it is so small. If the nucleus broke apart then Hubble would have likely seen evidence for multiple fragments.

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