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Tag Archives: x-ray

From a press release from the Chandra X-ray Center and NASA’s Marshall Space Flight Center, September 23, 2015:

Three orbiting X-ray space telescopes have detected an increased rate of X-ray flares from the usually quiet giant black hole at the center of our Milky Way galaxy after new long-term monitoring. Scientists are trying to learn whether this is normal behavior that was unnoticed due to limited monitoring, or these flares are triggered by the recent close passage of a mysterious, dusty object.

Credit: NASA/CXC/MPE/G.Ponti et al; Illustration: NASA/CXC/M.Weiss

Credit: NASA/CXC/MPE/G.Ponti et al; Illustration: NASA/CXC/M.Weiss

By combining information from long monitoring campaigns by NASA’s Chandra X-ray Observatory and ESA’s XMM-Newton, with observations by the Swift satellite, astronomers were able to carefully trace the activity of the Milky Way’s supermassive black hole over the last 15 years. The supermassive black hole, Sagittarius A*, weighs in at slightly more than 4 million times the mass of the Sun. X-rays are produced by hot gas flowing toward the black hole.

The new study reveals that Sagittarius A* (Sgr A* for short) has been producing one bright X-ray flare about every ten days. However, within the past year, there has been a ten-fold increase in the rate of bright flares from Sgr A*, at about one every day. This increase happened soon after the close approach to Sgr A* by a mysterious object called G2.

Originally, astronomers thought G2 was an extended cloud of gas and dust. However, after passing close to Sgr A* in late 2013, its appearance did not change much, apart from being slightly stretched by the gravity of the black hole. This led to new theories that G2 was not simply a gas cloud, but instead a star swathed in an extended dusty cocoon.

While the timing of G2’s passage with the surge in X-rays from Sgr A* is intriguing astronomers see other black holes that seem to behave like Sgr A*. Therefore, it’s possible this increased chatter from Sgr A* may be a common trait among black holes and unrelated to G2. For example, the increased X-ray activity could be due to a change in the strength of winds from nearby massive stars that are feeding material to the black hole.

If the G2 explanation is correct, the spike in bright X-ray flares would be the first sign of excess material falling onto the black hole because of the cloud’s close passage. Some gas would likely have been stripped off the cloud, and captured by the gravity of Sgr A*. It then could have started interacting with hot material flowing towards the black hole, funneling more gas toward the black hole that could later be consumed by Sgr A*.

Links: Full Chandra press release; detailed image description; MNRAS paper by G. Ponti et al.

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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.

Black_hole_with_stellar_companion_node_full_image_2

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.

From a NuSTAR mission press release:

A mission designed to set its eyes on black holes and other objects far from our solar system turned its gaze back closer to home, capturing images of the Sun. In December 2014, NASA’s Nuclear Spectroscopic Telescope Array, or NuSTAR, took its first picture of the Sun, producing the most sensitive solar portrait ever taken in high-energy x-rays.

nustar141222_Tn

Credit: NASA/JPL-Caltech

While the sun is too bright for other telescopes such as NASA’s Chandra X-ray Observatory, NuSTAR can safely look at it without the risk of damaging its detectors. The Sun is not as bright in the higher-energy x-rays detected by NuSTAR, a factor that depends on the temperature of the Sun’s atmosphere.

This first solar image from NuSTAR gives insight into questions about the remarkably high temperatures that are found above sunspots. Future images will provide even better data as the Sun winds down in its solar cycle, with the potential to capture hypothesized nanoflares – smaller versions of the Sun’s giant flares that erupt with charged particles and high-energy radiation.

Links: NuSTAR press release, full-view image of the Sun’s disk.

One of the most famous objects in the sky, the Cassiopeia A supernova remnant (see Figure 13-18c) – Cas A, for short – has been rendered for display like never before, thanks to NASA’s Chandra X-ray Observatory and a new project from the Smithsonian Institution. A new three-dimensional viewer allows users to interact with many one-of-a-kind objects from the Smithsonian as part of a large-scale effort to digitize many of the Institutions objects and artifacts.

Scientists have combined data from Chandra, NASA’s Spitzer Space Telescope, and ground-based facilities to construct a unique 3D model of the 300-year old remains of a stellar explosion that blew a massive star apart, sending the stellar debris rushing into space at millions of miles per hour. The collaboration with this new Smithsonian 3D project allows the astronomical data collected on Cas A to be featured and highlighted in an open-access program.

casa_525

Credit: NASA/CSC/SAO

To coincide with Cas A being featured in this new 3D effort, a specially-processed version of Chandra’s data of this supernova remnant has been released. This new image shows with better clarity the appearance of Cas A in different energy bands, which will aid astronomers in their efforts to reconstruct details of the supernova process such as the size of the star, its chemical makeup, and the explosion mechanism. The color scheme used in this image is the following: low-energy X-rays are red, medium-energy ones are green, and the highest-energy X-rays detected by Chandra are colored blue.

Cas A is the only astronomical object to be featured in the new Smithsonian 3D project. This and other objects in the collection – which include the Wright brothers plane, a 1600-year-old stone Buddha, a gunboat from the Revolutionary War, and fossil whales from Chile – were showcased in the Smithsonian X 3D event on November 13th and 14th at the Smithsonian in Washington, DC.

Links: Smithsonian X 3D beta tour; Chandra X-ray Center press release; NASA press release; YouTube movie of a fly-through.