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Monthly Archives: June 2015

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.


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.

Here is a consolidated list of errors from the text’s first printing. Many of these have already been posted here as separate chapter updates. (Our publisher will make the necessary corrections to the printed book at the earliest opportunity.):

p. 25, Figure It Out 2.3: The last paragraph (about Fraunhofer) shouldn’t be there. Instead, it should be at the end of the caption of Figure 2-4 on p. 26.

p. 64, Q34: 1 Angstrom should be listed as 1010 m, not 108 m.

p. 64, Q41: Ditto

p. 78: There is an error in the equation relating the apparent magnitude and brightness of stars in Figure It Out 4.1.  In this equation, 2.512 should be raised to a power equal to (mB−mA).

p. 92, Q1: We could more clearly say “On the top picture” instead of just “On the picture” – since there are now two pictures on the opening page of the chapter (and the stars are somewhat too dense for individual clarity in the bottom picture).

p. 190: First sentence of Section 7.4d: “a little larger” should be “a little smaller” for the relative sizes of Triton and the Moon.

p. 309, Q53, there is a printing error when going from the bottom of column 1 to the top of column 2. At the top of column 2, the “(e)” should be boldface, there should be a period after “1/16”, and the remainder of the text should be deleted.

p. 363, column 1, second line from the bottom: When referring to the event horizon: “1/3” should be “2/3”, i.e. the sentence should read “Its radius is exactly 2/3 times that of the photon sphere…”

p. 391, column 2, second line from the bottom: for Spitzer, “Section 3.8c, Figure 3-32a).” should say simply “Section 3.8c).”

p. 392, column 1, line 5: At the end, add “(See Section 3.8c, Figure 3-32a.)”

Appendix 3C, column 3 header: “105 km” should be “106 km”

From an article on

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.


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: article; HAWC Observatory home.

From an article on

Mercury has possessed a magnetic field for billions of years, and that field may have once been as strong as the Earth’s.

As NASA’s MESSENGER spacecraft ended its four-year mission at Mercury, it travelled so low over the surface, at altitudes as low as 15 kilometers, that it was able to detect weak magnetism coming from surface rocks in terrain 3.7 to 3.9 billion years old.


Credit: NASA/University of British Columbia

The discovery indicates that Mercury’s magnetic field, generated by liquid rotating in the planet’s core, was that old, helping to constrain scenarios for how Mercury has evolved over time. No trace of magnetism on Earth in rocks older than 3.5 billion years has been found.

Link: article.

From APOD, June 3, 2105:

A new view of Saturn’s moon Hyperion was released by the Cassini team during a recent fly-by.


Credit: NASA/JPL-Caltech/SSI

The images shows numerous unusually-shaped craters with dark material at the bottom. At around 250 km across, its gravitational pull on Cassini reveals that it is mostly empty space. The unusual crater shapes are thought to arise from surface impacts, which compress and eject surface material, unlike the regular circular shock-wave craters seen on other moons and planets.

Link: APOD, June 3, 2015.

From a New Scientist article, May 16, 2015:

The United Arab Emirates has announced details of its uncrewed Mars probe, which it plans to launch in 2020 to monitor the planet’s atmosphere from orbit. The spacecraft, named Hope, will be a big step up from the country’s previous space activities as it attempts to compete with other emerging space powers like India and China.


Credit: © Mohammed bin Rashid Space Centre

The Mars probe will carry spectrometers for analysing infrared and ultraviolet signals, along with a digital camera. These will measure water, dust and other molecules in the planet’s atmosphere, in an attempt to learn how Mars transitioned from a wet, warm world to the dry, dusty one we see today.

The science goals are similar and complementary to those of MAVEN and MOM, two Mars probes launched last year by NASA and the Indian space agency ISRO.

Link: New Scientist article.

From a news report on, April 20, 2015:

The Japan Aerospace Exploration Agency (JAXA) has unveiled the plan for a Moon lander. If successful, Japan will be the fourth country to send an unmanned probe to the moon after Russia, the United States, and China.

JAXA plans to launch the mission as early as 2018, with a development cost estimated at up to 15 billion yen ($126 million). The probe, named SLIM (Smart Lander for Investigating Moon), will be carried by the nation’s solid-fuel “Epsilon” rocket.

Link: article.

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.


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.