Spiral galaxies have three main components: a bulge, disk, and halo (see right). The bulge is a spherical structure found in the center of the galaxy. This feature mostly contains older stars. The disk is made up of dust, gas, and younger stars.

The arms of a spiral galaxy have lots of gas and dust, and they are often areas where new stars are constantly forming. The bulge of a spiral galaxy is composed primarily of old, red stars. Very little star formation goes on in the bulge. The table below shows the abbreviations that are used for spiral galaxy types.

Spiral galaxies are twisted collections of stars and gas that often have beautiful shapes and are made up of hot young stars. Most spiral galaxies contain a central bulge surrounded by a flat, rotating disk of stars.

Why are the arms of spiral galaxies typically blue in color? Stars are forming in the spiral arms so there are high mass, hot, blue stars in the arms. Collisions are much more common in large galaxy clusters. Collisions can build elliptical galaxies that are bigger and bigger.

Answer: Spiral arms are waves of enhanced density of stars and gas in the disk of a galaxy. Such stars do not have time to diffuse out across the galactic disk and therefore trace the location of the spiral arms, which consequently appear blue.

1 Answer. The Globular Clusters found mostly in the halo surrounding the core of any big galaxy are the most ancient structures found within any galaxy, including our own.

about 13.2 billion years

As the oldest visible component of the galaxy, the stellar halo holds important clues to the formation of the Milky Way. Metal-poor subdwarfs in the solar neighborhood have large velocities with respect to the Sun and other disk stars.

The Earth lies close to the center of the Galaxy. Motions of objects near our Galaxy’s core suggest the central black hole is about 3.7 billion solar masses.

From Earth, the Milky Way seems to be a heavenly mist because the stars blur together. Little do most people know, the stars are broken into four main parts. The four main parts are the disk, the nuclear bulge, the halo, and the galactic corona.

125 billion

52 different Earths

Our home galaxy, the Milky Way, contains at least 100 billion stars, and the observable universe contains at least 100 billion galaxies.

IC 1101

Why black holes are the scariest things in the universe. For one, falling into a black hole is easily the worst way to die. Halloween is a time to be haunted by ghosts, goblins and ghouls, but nothing in the universe is scarier than a black hole.

Quasars inhabit the centers of active galaxies and are among the most luminous, powerful, and energetic objects known in the universe, emitting up to a thousand times the energy output of the Milky Way, which contains 200–400 billion stars.

Lockheed SR-71 Blackbird

In special relativity, it is impossible to accelerate an object to the speed of light, or for a massive object to move at the speed of light. However, it might be possible for an object to exist which always moves faster than light.

September 27, 1905. In the fourth paper, Einstein explained the relationship between energy and mass. That is, E=mc2. In other words, energy = mass x the speed of light squared. In their interiors, atoms (mass) fuse together, creating the tremendous energy of the sun as described by Einstein’s famous equation.

Albert Einstein’s special theory of relativity famously dictates that no known object can travel faster than the speed of light in vacuum, which is 299,792 km/s. Unlike objects within space–time, space–time itself can bend, expand or warp at any speed.

Using NASA’s Chandra X-ray Observatory, astronomers have seen that the famous giant black hole in Messier 87 is propelling particles at speeds greater than 99% of the speed of light.

It’s not much since a typical black hole will emit only one particle every year, but it’s not nothing. A good size black hole — say, a few times more massive than the sun — will take about 10^100 years to eventually evaporate through this process, known as Hawking Radiation.

ten million

Kopeikin and Fomalont concluded that the speed of gravity is between 0.8 and 1.2 times the speed of light, which would be fully consistent with the theoretical prediction of general relativity that the speed of gravity is exactly the same as the speed of light.

“Big” G is Newton’s gravitational constant and gives the constant of proportionality in Newton’s Universal law of gravitation which is the basis of our understanding of non-relativistic gravity.

The best results, at the present time, tell us that the speed of gravity is between 2.993 × 10^8 and 3.003 × 10^8 meters per second, which is an amazing confirmation of General Relativity and a terrible difficulty for alternative theories of gravity that don’t reduce to General Relativity! (Sorry, Newton!)

The gravitational field is really a curving of space and time. The stronger the gravity, the more spacetime curves, and the slower time itself proceeds. It is only relative to a reference frame with weaker gravity that his time runs slow.