Earth & Space Science March 2015 Black Holes Earth & Space Science March 2015

Black Holes: A Theoretical Definition (A Review) An area of space-time with a gravitational field so intense that its escape velocity is equal to or exceeds the speed of light.

Types of Black Holes “Normal Sized” Black Holes Microscopic (Primordial) Sized Super-Massive Black Holes (On the order of millions to billions of Solar Masses) Estimated 4.1 million solar masses for Milky Way Black Hole (Sagittarius A)

How Normal Black Holes Come About (A Review) Most Black Holes are believed to come about from the death of massive stars.

When a sun the size of ours dies, it becomes a white dwarf: Image of Sirius A and Sirius B taken by the Hubble Space Telescope. Sirius B, which is a white dwarf, can be seen as a faint pinprick of light to the lower left of the much brighter Sirius A. Located in Canis Major, Sirius is the brightest star in the Earth’s night sky. The distance between A and B varies from 8 to 31 AU.

When a sun 1.5 to 3 times the size of ours dies, it becomes a Neutron Star.

Neutron stars are the densest and smallest stars known to exist in the universe; with a radius of only about 7 mi, they can have a mass of about two times that of the Sun.

Neutron stars have been observed to "pulse" radio and x-ray emissions Neutron stars have been observed to "pulse" radio and x-ray emissions. Through mechanisms not yet entirely understood, these particles produce coherent beams of radio emission. The pulses come at the same rate as the rotation of the neutron star, and thus, appear periodic. Neutron stars which emit such pulses are called pulsars. Neutron star in Crab Nebula. The dot at the very center is the hot pulsar spinning 30 times per second.

A pulsar is short for pulsating radio star First detected in 1967

When a sun 10 times the size of our sun dies, gravity crushes it causing a supernova: SN 1604 Latest observed supernova in our galaxy. Maintained naked-eye visibility for 18 months.

SN 1987A visible to the Naked eye for over 3 months .

When a sun 100 or more times the size of our sun dies it sets off the biggest explosion in the universe, a hypernova, creating a Black Hole.

SN 2006gy occurred in a distant galaxy approximately 238 million light years away. Therefore, due to the time it took light from the supernova to reach Earth, the event occurred about 238 million years ago.

SN 2006gy was an extremely energetic supernova, sometimes referred to as a hypernova or quark-nova discovered on September 18, 2006. Brightest ever recorded supernova. Preliminary indications are that it was an unusually high-energy supernova of a very large star, around 150 solar masses.

Neutron stars and black holes are among the more exotic members of the vast population of stars throughout the universe.

These objects represent the end states of stellar systems, yet despite their bizarre nature they do seem to fit quite well within our models of stellar evolution.

This stunning image is actually a composite of three images taken by telescopes in Earth orbit: optical light (yellow) observed with Hubble, X-ray radiation (blue and green) with Chandra and infrared radiation (red) with Spitzer.

The object is Cassiopeia A, the remnant of a supernova that exploded about 300 years ago: the small turquoise dot at the center may be a neutron star. (NASA)

The Smithsonian's Astrophysical Observatory in Cambridge, MA, hosts the Chandra X-ray Center which operates the satellite, processes the data, and distributes it to scientists around the world for analysis

Where Could Super-Massive Black Holes Exist? The only known places in the Universe where there could be enough mass in one area is in the center of massive galaxies Not believed to be anywhere else

Quasars: What are They? In some places where point sources of radio waves were found, no visible source other than a stellar-looking object was found (it looked like a point of light --- like a star does). These objects were called the "qausi-stellar radio sources", or "quasars" for short. Later, it was found these sources could not be stars in our galaxy, but must be very far away --- as far as any of the distant galaxies seen. We now think these objects are the very bright centers of some distant galaxies, where some sort of energetic action is occurring.

Active Galactic Nuclei In some galaxies, known as "active galactic nuclei" (AGN), the nucleus (or central core) produces more radiation than the entire rest of the galaxy! Quasars are very distant AGN -

The magnetic fields around black holes that are thought to produce the spectacular jets of high-energy particles rushing away from black holes come from the disk of hot gas around the black hole, not the black hole itself. The jets are made by the Magnetic field of the matter before it goes in the Black Hole.

The Chandra X-ray image is of the quasar PKS 1127-145, a highly luminous source of X-rays and visible light about 10 billion light years from Earth. An enormous X-ray jet extends at least a million light years from the quasar.

Observations of Super Massive Black Holes Radio observations by various radio telescopes X-ray observations from the orbital Chandra Observatory Optical Observations from Hubble Space Telescope

Pictures NGC4261

NASA's Chandra X-ray Observatory is a telescope specially designed to detect X-ray emission from very hot regions of the Universe such as exploded stars, clusters of galaxies, and matter around black holes.

Because X-rays are absorbed by Earth's atmosphere, Chandra must orbit above it, up to an altitude of 86,500 miles in space.

Abundance of elements How and where did all the elements form? Were they always present in the universe, or were they created after the universe formed?

Since the 1950s, astronomers have come to realize that the hydrogen and most of the helium in the universe are primordial— that is, these elements date from the very earliest times.

All other elements in our universe result from stellar nucleosynthesis—that is, they were formed by nuclear fusion in the hearts of stars. Therefore, all elements heavier than helium formed by stellar nucleosynthesis.

The End