Quasi-periodic oscillations appear to be a common characteristic of accreting systems and have been observed in black hole and neutron star X-ray binaries, alongside active galactic nuclei and even ultraluminous X-ray sources. The focus of this blog post is quasi-periodic oscillations in black hole X-ray binaries. Black hole X-ray binaries are comprised of a stellar mass black hole feeding on a nearby star. Material siphoned off the star by the black hole swirls around the black hole, forming an accretion disk that shines brightly at X-ray frequencies (see Figure 1). Not all of the material in the disk is consumed by the black hole- hydro-magnetic processes in the inner regions…

An eclipse is defined as a total or partial obscuring of one astronomical body by another. For millennia, cultures all over the world have witnessed, marveled at, and feared eclipses. For residents of planet Earth, the two most interesting and important eclipses are of eclipses the Sun (Solar eclipse) and the Moon (Lunar Eclipse). A lunar eclipse occurs when Earth comes between the Sun and the Moon. The Moon shines brightly in the sky primarily because it reflects most of the light receives from the Sun. However, during the lunar eclipse, the Earth obstructs the path of light from the Sun to the Moon, leaving the Moon behind in its…

May 2021 marks a significant milestone in planetary exploration, when China’s spacecraft Tianwen-1 softly landed on the surface of Mars, and deployed the rover Zhurong. The complete success of China’s first interplanetary mission makes China the third country landing on Mars (after the Soviet Union and the United States), the second country releasing a Martian rover (after the US), and the first country that achieved orbiting, landing and roving in the first mission to Mars. “Tianwen (天问)” is the name of China’s upcoming series of planetary missions. The name means “questions to heaven”, taken from the long classical poem written by the ancient Chinese poet Qu Yuan. The poem conveys…

This is the final part of the three part series on Spaghettification where finally black holes come into the picture! Black Holes Black holes are regions of space(time) where gravity becomes is so strong that that not even light can escape. The size of this spherical region is specified by a radius called the Schwarzschild radius (in honor of the German physicist and astronomer Karl Schwarzschild). The radius of a black hole is proportional to it’s mass. For example: a black hole having the same mass as our Sun (what astronomers call 1 solar mass) is like a sphere having a Schwarzschild radius of 2.8 km. In comparison the sun’s…

In China, there is a popular nursery rhyme: Once upon a time there was a mountain, in which there was a temple, in which there was an old monk telling a story to a little monk. The story he was telling is: Once upon a time there was a mountain, in which there was a temple, in which there was an old monk telling a story to a little monk…… It continues endlessly until the child falls asleep. This rhyme is a typical manifestation of the concept of self-similarity. In mathematics, self-similarity describes the property of an object if a part of it resembles the whole object. In the aforementioned…

February 18th 2021, 12:55 PST. A room in California erupts in cheers and applause as mission control watches its robot land on another planet. After years of preparations and almost seven months of space travel, Perseverance arrived safe and sound on the Red Planet, ready to study its environment for a planned duration of two years. It will join NASA’s Mars Exploration Program lineage of four martian rovers, making it the fifth since 1997 to explore this curious planet. But why do we care about Mars so much? Mars has always been an object of wonder, from the idea that a civilization could inhabit it to Elon Musk’s plans for…