The first-ever direct image of a black hole was captured in April 2019 by the Event Horizon Telescope (EHT), which is a network of telescopes around the world. Related reading: Interesting facts about black holesĭespite the fact that black holes are a rather stealthy structure in space, scientists still managed to find a way to image one. Black holes are also believed to be responsible for powering some of the hottest and brightest phenomena in the universe, like gamma-ray bursts. There are different types of black holes, depending on their masses: the smallest are called stellar black holes and can be as small as a few suns, while the biggest are called supermassive black holes and can be billions of times more massive than the sun. To spot them, scientists have to investigate and analyse their effects on nearby matter. Several of the brightest stars are identified by name. Along the horizontal axis, we can plot either temperature or spectral type (also sometimes called spectral class). In such diagrams, luminosity is plotted along the vertical axis. These cosmic powerhouses don’t emit any light, so they are invisible to our normal means of detection. Figure 18.14 HR Diagram for a Selected Sample of Stars. Black holes are extremely dense regions in space where gravity is so strong that nothing, not even light, can escape. When stars of masses >3 solar masses die in a supernova explosion, the dead core collapses into a gravitational singularly called a black hole. Some neutron stars, known as pulsars, emit beams of light and radiation that sweep across space like a lighthouse. To add to their super exotic nature, they also spin incredibly fast, with some neutron stars completing a rotation in just a few milliseconds. It is so strong that anything approaching those stars would be ripped apart long before it could reach the surface. This resulted in them having some of the strongest magnetic fields in the universe. Neutron stars have incredibly strong gravitational fields, which can be billions of times stronger than that of Earth. Neutron stars are incredibly dense and compact objects that are made almost entirely of neutrons, which are subatomic particles that make up the nucleus of atoms. Their temperatures are ~600,000K, radii 5-15 km, mass ~1.4-3.2 solar masses and extremely low luminosities. Neutron stars are ~0.7% of the stars in the universe. Neutron stars are produced when the cores of massive stars are compressed past the white dwarf stage during a supernova event.
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