β¦ A Field Guide to the Universe
A website that shows basic information about the universe. Made by Elvin Pio
Galaxies are vast gravitational systems of stars, stellar remnants, interstellar gas, dust, and dark matter. There are estimated to be between 200 billion and 2 trillion galaxies in the observable universe. Most galaxies span 1,000 to 100,000 parsecs in diameter and are separated by distances in the order of millions of parsecs. They are classified primarily by visual shape into spirals, ellipticals, lenticulars, and irregulars β a scheme devised by Edwin Hubble in 1926 and laid out in what astronomers call the Hubble Tuning Fork diagram.
Source: Wikipedia β Galaxy Β· AstroBackyardApproximately 60% of all galaxies are spiral galaxies, making them home to the majority of stars in the universe. They possess a rotating disc with prominent spiral arms curving out from a dense central bulge. Our own Milky Way is a barred spiral β its central bar was confirmed by the Spitzer Space Telescope in 2005. Spiral arms are not fixed structures; stars pass through them as they travel their own orbits, like traffic on a highway median. The arms are density waves first modeled by C.C. Lin and Frank Shu in 1964.
Source: ESA/Hubble β Spiral Galaxy Β· Wikipedia β Spiral GalaxyRanging from perfectly spherical to highly elongated, elliptical galaxies are thought to represent the mature or elderly phase of galactic evolution. Unlike spirals, their stars orbit the core in random directions with no systematic rotation, making them difficult to analyze for dark matter content. They contain little gas and dust, and star formation is largely extinct within them. Scientists believe most ellipticals originate from collisions and mergers of spiral galaxies. The largest known galaxy of any type β IC 1101 β is an elliptical spanning over 4 million light-years.
Source: NASA Science β Galaxy Types Β· Universe GuideIrregular galaxies defy classification into any neat category β they appear as toothpicks, rings, clumps, or chaotic mashups. Their unusual forms are typically the result of gravitational tidal interactions with neighboring galaxies. They often host intense star formation because of their rich gas and dust content. The Large and Small Magellanic Clouds β the Milky Way's closest dwarf galactic companions, visible in the Southern Hemisphere β are two of the best-known examples. The Milky Way is currently in the process of consuming the Sagittarius Dwarf Elliptical Galaxy.
Source: OpenStax Astronomy 2e Β· NMSU AstronomyThe Milky Way and the Andromeda Galaxy are approaching each other at 100β140 km/s. In approximately 4.3 billion years, the two may collide and ultimately merge over six billion years into a single large elliptical β or perhaps a large disk galaxy. Despite the violence implied, the chance of individual stars colliding is extremely low because of the vast distances between them. The resulting merged galaxy has been nicknamed "Milkdromeda." Our galaxy has collided and merged before β simulations suggest it merged with a large galaxy dubbed the Kraken roughly 11 billion years ago.
Source: Wikipedia β Milky Way Β· AstroBackyardA black hole is the endpoint of a star with more than roughly 20 times the mass of our Sun. When such a star exhausts its nuclear fuel, its iron core collapses catastrophically and rebounds in a supernova explosion, leaving behind an infinitely dense point β a singularity β wrapped in an event horizon from which nothing, not even light, can escape. At the center of most large galaxies, including the Milky Way, sits a supermassive black hole. Ours β Sagittarius A* β contains approximately 4 million solar masses. Gas and dust spiraling into the black hole form an accretion disk that can outshine the entire host galaxy, creating a quasar.
Source: NASA Science β Stars Β· NASA β Galaxy TypesWhen a star between 7 and 19 solar masses dies in a supernova, what remains is a neutron star β arguably the most exotic object we can directly observe. Compressed to a sphere roughly the diameter of a city while retaining up to twice the Sun's mass, neutron star material is so dense that a single sugar cube of it would weigh about 1 trillion kilograms on Earth β approximately the mass of a mountain. Many neutron stars are detected as pulsars, spinning many times per second and sweeping beams of radiation across the sky like cosmic lighthouses. Some neutron stars β magnetars β possess magnetic fields a thousand times stronger still, capable of causing starquakes that send gamma ray flashes thousands of light-years.
Source: NASA Science β Neutron Stars Are WeirdA supernova is one of the most energetic events in the universe. In the core-collapse variety, a massive star runs out of nuclear fuel and its iron core collapses in milliseconds, triggering a shockwave that rips through the star's outer layers. The initial flash can outshine the star's entire host galaxy for weeks. Supernova remnants β the expanding debris clouds β can be studied for millennia and are responsible for seeding the interstellar medium with heavy elements forged in the star's core: carbon, oxygen, iron, gold, uranium. Every atom heavier than iron in your body was forged in such an explosion. We are, in the most literal sense, made of stardust.
Source: NASA/Hubble β Nebulae Β· National Space Centre