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Tag Archives: gamma-ray

From a press release of the European Space Agency:

Over the past week, ESA’s Integral satellite has been observing an exceptional outburst of high-energy light produced by a black hole that is devouring material from its stellar companion.

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Credit and copyright: ESA/ATG medialab

X-rays and gamma rays point to some of the most extreme phenomena in the Universe, such as stellar explosions, powerful outbursts and black holes feasting on their surroundings. In contrast to the peaceful view of the night sky we see with our eyes, the high-energy sky is a dynamic light show, from flickering sources that change their brightness dramatically in a few minutes to others that vary on timescales spanning years or even decades.

On 15 June 2015, a long-time acquaintance of X-ray and gamma ray astronomers made its comeback to the cosmic stage: V404 Cygni, a system comprising a black hole and a star orbiting one another. It is located in our Milky Way galaxy, almost 8000 light-years away in the constellation Cygnus, the Swan. In this type of binary system, material flows from the star towards the black hole and gathers in a disc, where it is heated up, shining brightly at optical, ultraviolet and X-ray wavelengths before spiralling into the black hole.

The V404 Cygni black hole system has not been this bright and active since 1989, when it was observed with the Japanese X-ray satellite Ginga and high-energy instruments on board the Mir space station.

Link: the full ESA press release.

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From an article on Phys.org:

The High Altitude Water Cherenkov (HAWC) Gamma-Ray Observatory, located at 4000 m above sea level on the slopes of Mexico’s Volcán Sierra Negra, is the newest tool available to visualize the most energetic phenomena in the Universe, such as supernovae, neutron star collisions and active galactic nuclei.

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Credit: HAWC Collaboration

In March 2015, construction was completed on HAWC’s 300th and final detector tank (each holding 200,000 liters of water), and the observatory will soon begin collecting data at full capacity.

It is a joint project between U.S. and Mexican scientists, with some participation from Polish and Costa Rican scientists.

Links: Phys.org article; HAWC Observatory home.

The Fermi Gamma-ray Space Telescope celebrates 2000 days of orbiting Earth this week with a new map of the gamma-ray sky, published on APOD on December 6, 2013.

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Credit: International Fermi Large Area Telescope Collaboration, NASA, DOE

For an Earth-orbiting gamma-ray telescope, Earth is actually the brightest source of gamma-rays, the most energetic form of light. Gamma-rays from Earth are produced when high energy particles, cosmic rays from space, crash into the atmosphere. While that interaction blocks harmful radiation from reaching the surface, those gamma-rays dominate in this remarkable Earth and sky view from the orbiting Fermi Gamma-ray Space Telescope’s Large Area Telescope. The image was constructed using only observations made when the center of our Milky Way galaxy was near the zenith, directly above the Fermi satellite. The zenith is mapped to the center of the field. The Earth and points near the nadir, directly below the satellite, are mapped to the edges of the field resulting in an Earth and all-sky projection from Fermi’s orbital perspective. The color scheme shows low intensities of gamma-rays as blue and high intensities as yellowish hues on a logarithmic scale. Our fair planet’s brighter gamma-ray glow floods the edges of field, the high intensity yellow ring tracing Earth’s limb. Gamma-ray sources in the sky along the relatively faint Milky Way stretch diagonally across the middle.