Black HolesBlack Holes

Earth & Space Science Earth & Space Science

March 2015March 2015

Black Holes: A Theoretical Black Holes: A Theoretical Definition (A Review)Definition (A Review)

An area of space-time An area of space-time with a gravitational field with a gravitational field so intense that its so intense that its escape velocity is equal escape velocity is equal to or exceeds the speed to or exceeds the speed of light. of light.

Types of Black HolesTypes of Black Holes

““Normal Sized” Black Normal Sized” Black HolesHoles

Microscopic (Primordial) Microscopic (Primordial) SizedSized

Super-Massive Black Super-Massive Black Holes (On the order of Holes (On the order of millions to billions of Solar millions to billions of Solar Masses)Masses)

Estimated 4.1 million Estimated 4.1 million solar masses for Milky solar masses for Milky Way Black Hole Way Black Hole (Sagittarius A)(Sagittarius A)

How Normal Black Holes Come How Normal Black Holes Come About (A Review)About (A Review)

Most Black Holes are Most Black Holes are believed to come believed to come about from the death about from the death of massive stars.of massive stars.

When a sun the size of ours dies, it When a sun the size of ours dies, it becomes a white dwarf:becomes a white dwarf:

Image of Sirius A and Sirius BImage of Sirius A and Sirius B

taken by the Hubble Space Telescope. taken by the Hubble Space Telescope.

Sirius B, which is a white dwarf, can be Sirius B, which is a white dwarf, can be

seen as a faint pinprick of light to the seen as a faint pinprick of light to the

lower left of the much brighter Sirius A.lower left of the much brighter Sirius A.

Located in Canis Major, Sirius is the Located in Canis Major, Sirius is the

brightest star in the Earth’s night sky. brightest star in the Earth’s night sky.

The distance between A andThe distance between A and

B varies from 8 to 31 AU.B varies from 8 to 31 AU.

When a sun When a sun

1.5 to 3 times 1.5 to 3 times

the size of ours the size of ours

dies, it dies, it

becomes abecomes a

Neutron Star.Neutron Star.

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

Neutron stars have been observed to "pulse" radio Neutron stars have been observed to "pulse" radio and x-ray emissions. Through mechanisms not yet and x-ray emissions. Through mechanisms not yet entirely understood, these particles produce entirely understood, these particles produce coherent beams of radio emission. coherent beams of radio emission.

The pulses come at the The pulses come at the

same rate as the rotation same rate as the rotation

of the neutron star, and of the neutron star, and

thus, appear periodic. thus, appear periodic.

Neutron stars which emit Neutron stars which emit

such pulses are called such pulses are called

pulsars.pulsars.

A A pulsarpulsar is short for is short for pulsating radio starpulsating radio star

First detected in 1967First detected in 1967

When a sun 10 times the size of our sun When a sun 10 times the size of our sun dies, gravity crushes it causing a supernova:dies, gravity crushes it causing a supernova:

SN 1604 Latest observedSN 1604 Latest observed

supernova supernova in our galaxyin our galaxy..Maintained naked-eyeMaintained naked-eyevisibility for 18 months.visibility for 18 months.

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

..

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

SN 2006gy occurred in a distant galaxy SN 2006gy occurred in a distant galaxy approximately 238 million light years away. approximately 238 million light years away.

Therefore, due to the time Therefore, due to the time

it took light from the it took light from the

supernova to reach supernova to reach

Earth, the event Earth, the event

occurred about 238occurred about 238

million years ago.million years ago.

SN 2006gy was an extremely energetic SN 2006gy was an extremely energetic supernova, sometimes referred to as a hypernova supernova, sometimes referred to as a hypernova or quark-nova discovered on September 18, 2006.or quark-nova discovered on September 18, 2006.

Brightest ever recorded supernova.Brightest ever recorded supernova.

Preliminary indications are that it was an unusually Preliminary indications are that it was an unusually high-energy supernova of a very large star, around high-energy supernova of a very large star, around 150 solar masses.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 These objects represent the end states of stellar systems, yet despite their bizarre stellar systems, yet despite their bizarre nature they do seem to fit quite well within nature they do seem to fit quite well within our models of stellar evolution. our models of stellar evolution.

This stunning image is This stunning image is

actually a composite of actually a composite of

three images taken by three images taken by

telescopes in Earth orbit: telescopes in Earth orbit:

optical light (yellow) optical light (yellow)

observed with Hubble, observed with Hubble,

X-ray radiation (blue and X-ray radiation (blue and

green) with Chandra and green) with Chandra and

infrared radiation (red) with Spitzer. infrared radiation (red) with Spitzer.

The object is The object is

Cassiopeia A, Cassiopeia A,

the remnant of a the remnant of a

supernova that supernova that

exploded about exploded about

300 years ago: 300 years ago:

the small turquoise the small turquoise

dot at the center dot at the center

may be a neutron may be a neutron

star. (NASA)star. (NASA)

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

Where Could Super-Massive Black Where Could Super-Massive Black Holes Exist?Holes Exist?

The only known The only known places in the Universe places in the Universe where there could be where there could be enough mass in one enough mass in one area is in the center area is in the center of massive galaxiesof massive galaxies

Not believed to be Not believed to be anywhere elseanywhere else

Quasars: What are They?Quasars: What are They? In some places where point sources of radio waves were In some places where point sources of radio waves were

found, no visible source other than a stellar-looking found, no visible source other than a stellar-looking object was found (it looked like a point of light --- like a object was found (it looked like a point of light --- like a star does). These objects were called the "qausi-stellar star does). These objects were called the "qausi-stellar radio sources", or "quasars" for short.radio sources", or "quasars" for short.

Later, it was found these sources could not be stars in Later, it was found these sources could not be stars in our galaxy, but must be very far away --- as far as any of our galaxy, but must be very far away --- as far as any of the distant galaxies seen. We now think these objects the distant galaxies seen. We now think these objects are the very bright centers of some distant galaxies, are the very bright centers of some distant galaxies, where some sort of energetic action is occurring.where some sort of energetic action is occurring.

Active Galactic NucleiActive Galactic Nuclei In some galaxies, known In some galaxies, known

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

The magnetic fields The magnetic fields around black holes that around black holes that are thought to produce are thought to produce the spectacular jets of the spectacular jets of high-energy particles high-energy particles rushing away from black rushing away from black holes come from the disk holes come from the disk of hot gas around the of hot gas around the black hole, not the black black hole, not the black hole itself. hole itself.

The jets are made by the The jets are made by the Magnetic field of the Magnetic field of the matter before it goes in matter before it goes in the Black Hole.the Black Hole.

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

Observations of Super Massive Observations of Super Massive Black HolesBlack Holes

Radio observations Radio observations by various radio by various radio telescopestelescopes

X-ray observations X-ray observations from the orbital from the orbital Chandra ObservatoryChandra Observatory

Optical Observations Optical Observations from Hubble Space from Hubble Space TelescopeTelescope

PicturesPictures

NGC4261

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

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

Abundance of elementsAbundance of elements

How and where did all the elements form? How and where did all the elements form?

Were they always present in the universe, or Were they always present in the universe, or were they created after the universe were they created after the universe formed? formed?

Since the 1950s, astronomers have come to Since the 1950s, astronomers have come to realize that the hydrogen and most of the realize that the hydrogen and most of the helium in the universe are primordial—helium in the universe are primordial—

that is, these elements date from the very that is, these elements date from the very earliest times. earliest times.

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

Therefore, all elements heavier than helium Therefore, all elements heavier than helium formed by stellar nucleosynthesis.formed by stellar nucleosynthesis.

The EndThe End