Radio galaxies are powered by a central supermassive black hole feeding on surrounding matter. Some of this matter is ejected in opposing directions along the axis of rotation of the black hole in the form of powerful relativistic jets. These jets are launched with velocities close to the speed of light and travel vast distances away from their host galaxies. They emit radiation predominantly at radio frequencies, but also emit across the entire electromagnetic spectrum. Jets have a major impact on their surroundings. They can significantly heat their environments, reduce star formation and limit the growth of galaxies. When observed at radio frequencies jets display a wide range of different appearances.…
Read More >>A young black hole blowing a huge bubble into space
Numerous black holes are hidden in the space. These compact objects are difficult to probe as light cannot escape from the strong gravities from them. Fortunately, some black holes are actively shaping their environment and in such a way, we could “catch” them. SS 443 is one of the most popular and active black hole systems that strongly influence its neighborhood. It is a young binary system that contains a 16 solar mass black hole accreting materials from a massive star orbiting around it (see Figure 1). The black hole was formed in a recent stellar explosion, which we call “supernova”. The recent time here means 20 thousand years ago,…
Read More >>A Glimpse into Supermassive Black Holes from “Observing” JAB Simulations
By Dr. Richard Anantua This past decade has been a landmark in the history of black hole astrophysics— bringing precise experimental confirmation to bear upon revolutionary predictions of Einstein’s general theory of relativity from just over a century ago. LIGO’s 2015 observation of the “chirp” signal characteristic of the merger of two black holes marked a 5.1 sigma detection of gravitational waves predicted by Einstein in 1916, and the first measurement of an astronomical signal outside the electromagnetic spectrum. In 2018, the European Southern Observatory’s GRAVITY (4 very large infrared telescopes) detected gravitational redshift from the passage of the star S2 at a near-relativistic speed of 0.03c near the pericenter…
Read More >>IceCube South Pole Neutrino Observatory
On 18 December 2010, a huge human task was accomplished. 5,160 spherical optical sensors called Digital Optical Modules (DOMs) were transported and placed under the frozen surface of Antarctica. 52 institutions from 12 countries around the globe contributed (and still do) to this collaboration. The DOMs, attached to 86 vertical “strings”, cover a cubic-kilometer area from 1,450 meters to 2,450 meters depth (see Fig. 1) and are designed to indirectly detect neutrinos. Thus the first, and so far the only, cubic-kilometer neutrino telescope was born! This telescope is called the IceCube South Pole Neutrino Observatory. Neutrinos are electrically neutral subatomic particles that interact very rarely with matter. When they do…
Read More >>The beauty of Einstein’s equations: black holes and beyond
There’s no doubt about it: Einstein’s general theory of relativity has changed the way we understand the cosmos, with its crowning glory being the discovery of black holes. Last year (2019), in May, I gave a short talk about the Event Horizon Telescope results on a webinar (link here) hosted by SPACE- India, an organization dedicated to bringing the wonders of space to school children in India. You can see the pdf of the talk here. I had a fun time interacting with them and (hopefully!) answered some of the questions from these curious young minds. I, of course, thank SPACE-India for the opportunity to reach so many kids. It…
Read More >>Fate of Jets in X-ray binaries: jet-wind interaction
Relativistic jets are ubiquitous and we can observe them in a wide range of scales: from stellar-mass objects (e.g., stellar-mass black holes, neutron stars or pulsars) to massive objects (e.g., active galactic nuclei, radio galaxies). In fact, those jets are key players in shaping our universe into what it is now. For example, jets from active galactic nuclei are powerful and capable of reaching very far from the central region of their host galaxy, it is generally accepted that they have provided a huge amount of heating into the universe. Without the heating, most galaxies might have significantly cooled down a long time ago; and had only old stars or…
Read More >>When A Black Hole Devours A Star
Black hole X-ray binaries are systems in which a stellar-mass black hole ‘feeds’ on (accretes) gas from a companion star. Gas from the star swirls around the black hole, forming an accretion disk. The accretion disk shines brightly at X-ray frequencies and black hole X-ray binaries are some of the brightest X-ray emitting sources observed in our galaxy. Black hole X-ray binaries (BHXRBs) have been observed to cycle between different ‘accretion states’. These accretion states are associated with different emission and outflow properties— Some accretion states are associated with very bright X-ray emission, while others display weak X-ray emission. In some accretion states weak outflows are driven from the disk…
Read More >>Astronomy occasionally sounds like a spy movie
Today’s story starts in 1967, at the height of the Cold War. The US Air Force has been using its Vela satellites to monitor any traces of gamma-ray radiation, a dead giveaway of nuclear tests being conducted on Earth. The goal is to make sure that the USSR is complying with the 1963 Nuclear Test Ban Treaty. On July 2nd, 1967, the Vela 3 and 4 satellites detect a gamma-ray flash that doesn’t look like anything observed before. Over time, they start seeing more and more of these events; according to myth, this was a terrifying find which was immediately classified. Nobody knew that such signals can originate from space,…
Read More >>Finding a candidate X-ray binary in another galaxy
Recently, I have been involved in a study looking for potential X-ray binaries in the relatively nearby spiral galaxy M83. And we think we found one! Here we refer to a microquasar as either a black hloe or neutron star X-ray binary. This work was led by Prof. Roberto Soria at the University of the Chinese Academy of Sciences, and was accepted for publication last week. Here is a link to the arXiv pre-print version. Finding a microquasar Jets from microqusars can produce shock-ionised bubbles as they shoot material out into their surroundings. These bubbles can look like peculiar shaped supernova remnants (SNRs, see Ping’s post for more details on…
Read More >>The changing sky monitored by ancient astronomers
Our ancestors have been monitoring the night sky since 5000 years ago, making astronomy the oldest natural science. Most stars seen on the night sky have been there for millions to billions of years, except that they rise and descend along with the Earth’s rotation. But if one is very patient and lucky, one could see that the sky is changing. For astrological purposes and other reasons, the variation of the sky had been recorded by ancient astronomers. In addition to the comets and meteors, many transient events occur outside of our Solar systems. The astronomical term “transient” expresses the phenomena that some celestial objects switch on and off their…
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