GALAXIES

WHAT ARE THE DEEP SKY OBJECTS?

•Deep-sky objects are astronomical objects other than individual stars and solar system objects (Sun, Moon, planets, comets).

TYPES OF DEEP SKY OBJECTS

•Nebulae

•Clusters

•Galaxies

CHARLES MESSIER

• Known for the Messier catalogue of galaxies, nebulae and star clusters

M1 to M110

• He was a French astronomer who lived in the 18th century.

• He was a comet hunter and the purpose of the catalogue was to record the sky objects that looked as comets but were not comets because they would not move in the sky.

• A Light-year is the distance that light travels in a year with a speed of approximately 300,000 kilometers per second

UNITS TO MEASURE DISTANCE

• Closest star to the Sun is Proxima Centauri at 4.37 light years.

• A Parsec is the equal to about 3.26 light years

•A galaxy is an enormous collection of gas, dust and billions of stars held together by gravity. One galaxy can have hundreds of billions of stars and be as large as 200,000 light years across.

•Galaxy is derived from the Greek galaxias meaning "milky", a reference to the Milky Way.

• Many galaxies are believed to have black holes at their active center. The Milky Way's central black hole, known as Sagittarius A, has a mass four million times that of our Sun.

GALAXIES

• There are potentially more than 170 billion galaxies in the observable universe. Some, called dwarf galaxies, are very small with about 10 million stars, while others are huge containing an estimated 100 trillion stars.

• Supermassive black holes are believed to sit at the center of most galaxies.

GALAXIES FACTS

TYPES OF GALAXIES

ELLIPTICAL GALAXIES

ELLIPTICAL GALAXIES

• Look like enormous globular clusters.

• Elliptical galaxies are often bigger than spiral galaxies.

• Stars are yellow & red, with very little free dust & gas.

• These galaxies are old & no longer forming new stars.

• Elliptical galaxies may form from the collision of 2 or more spiral galaxies.

SPIRAL GALAXIES

• Like our own Milky Way, all spiral galaxies have a nuclear bulge, and at least 2 spiral or propeller-shaped arms, with a halo of gas, dust, stars, and globular clusters.

• Spiral galaxies are classified as Sa, Sb, or Sc depending on the size of the nucleus & how tightly the arms are wrapped.

M104 – the Sombrero Galaxy, has a

large nucleus & very tight spiral arms.

THE SOMBRERO GALAXY M104

The Sombrero Galaxy (also known as

M104 or NGC 4594) is an unbarred spiral

galaxy in the constellation Virgo. It has a

bright nucleus, an unusually large central

bulge, and a prominent dust lane in its

inclined disk. The dark dust lane and the

bulge give this galaxy the appearance of a

sombrero. The galaxy has an apparent

magnitude of +9.0, making it easily visible

with amateur telescopes. The large bulge,

the central supermassive black hole, and

the dust lane all attract the attention of

professional astronomers.

• The Andromeda Galaxy (M31) is the closest large

galaxy to the Milky Way and is one of only ten

galaxies that can be seen with the naked eye from

the Earth.

• Andromeda is accompanied by at least 10 satellite

galaxies the most notable of which is the

Triangulum Galaxy.

ANDROMEDA GALAXY

ANDROMEDA GALAXY M31

• It is 2.2 million light years away from us and

• approaching the Milky Way at approximately 100

to 140 kilometers per second…

• Five billion years from now it will probably collide

with our Milky Way galaxy.

• While Andromeda is the largest galaxy in the Local

Cluster it is not the most massive as the Milky May

is thought to contain more dark matter making it

the most massive

ANDROMEDA FACTS

HOW TO FIND ANDROMEDA GALAXY

BLACK EYE GALAXY - M64

A spiral galaxy in the Coma Berenices

constellation, Messier 64, the famous

"Black Eye" galaxy or the

"Sleeping Beauty galaxy," has a

spectacular dark band of absorbing dust in

front of the galaxy's bright nucleus. It is

well known among amateur astronomers

because of its appearance in small

telescopes.

THE WHIRLPOOL GALAXY - M51A Also known as Messier 51a,

M51a, or NGC 5194, the Whirlpool

Galaxy is an interacting grand-

design spiral galaxy located at a

distance of approximately 23

million light-years in the

constellation Canes Venatici. It is

one of the most famous spiral

galaxies in the sky. The galaxy

and its companion (NGC 5195)

are easily observed by amateur

astronomers, and the two galaxies

may even be seen with binoculars.

The Whirlpool Galaxy is also

a popular target for professional

astronomers, who study it to

further understanding of galaxy

structure (particularly structure

associated with the spiral arms)

and galaxy interactions.

The Whirlpool Galaxy M51

is one of the largest

galaxies visible without

using professional

telescope. Millions of years

ago two galaxies collided to

create this colorful and

dramatic object. To find it,

look about 3.5 degrees

southeast of the last star in

the Big Dipper’s handle.

M81 URSA MAJOR

The big and beautiful spiral galaxy M81, in

the northern constellation Ursa Major, is

one of the brightest galaxies visible in the

skies of planet Earth. This superbly

detailed view reveals its bright nucleus,

grand spiral arms and sweeping cosmic

dust lanes with a scale comparable to the

Milky Way. Hinting at a disorderly past, a

remarkable dust lane runs straight through

the disk, below and right of the galactic

center, contrary to M81's other prominent

spiral features. The errant dust lane may

be the lingering result of a close encounter

between M81 and its smaller companion

galaxy, M82. Scrutiny of variable stars in

M81 (aka NGC 3031) has yielded one of

the best determined distances for an

external galaxy -- 11.8 million light-years.

THE MILKY WAY

Scientists believe that 90% of our galaxy’s mass consists of dark matter, which

gives it a mysterious halo. That means that all of the “luminous matter” – i.e. that

which we can see with the naked eye or a telescopes – makes up less than 10% of

the mass of the Milky Way.

We live in one of the arms

of a large spiral galaxy

called the Milky Way. The

Sun and its planets

(including Earth) lie in this

quiet part of the galaxy,

about half way out from the

centre.

• The Milky Way galaxy is

whirling rapidly, spinning our

sun and all its other stars at

around 100 million km per

hour.

• The Sun travels around the

galaxy once every 200

million years – a journey of

100,000 light years.

• There may be a huge black

hole in the very middle of the

most of the galaxies.

MILKY WAY FACTS

The Milky Way is shaped like a huge whirlpool

that rotates once every 200 million years.

It is made up of at least 100 billion stars, as

well as dust and gas.

It is so big that light takes 100 000 years to

cross from one side to the other.

The centre of the Galaxy is very hard to see

because clouds of gas and dust block our view.

Scientists think that it contains a supermassive

black hole that swallows anything passing too

close.

MILKY WAY FACTS

• The Local Group is the galaxy group that includes

the Milky Way. It comprises more than 54 galaxies,

most of them being dwarf galaxies. Its gravitational

center is located somewhere between the Milky

Way and the Andromeda Galaxy.

• The group is a part of the larger Virgo Supercluster

or the Local Supercluster. At least 100 galaxy

groups and clusters are located within its diameter

of 33 megaparsecs (110 million light-years). It is

one of millions of superclusters in the observable

universe.

LOCAL GALACTIC GROUP

The speed turns out to be an astounding 1.3 million

miles per hour (2.1 million km/hr)! We are moving

roughly in the direction on the sky that is defined by

the constellations of Leo and Virgo. Astronomers

believe that there is a huge concentration of matter in

this direction. Some people call it The Great Attractor,

although we now know that the pull is probably not

due to one group of galaxies but many. Still the extra

gravity in this direction pulls the Milky Way (and many

neighbor galaxies) in that direction.

HOW FAST IS THE MILKY WAY GALAXY MOVING?

RESOURCES

https://www.youtube.com/watch?v=XUbG8jboh4M

http://www.skymaps.com/downloads.html

https://www.youtube.com/watch?v=ac9Cr6bf-mg

https://www.youtube.com/watch?v=UE8yHySiJ4A

https://www.youtube.com/watch?v=xwSQVSlccCg

http://messier.seds.org/m/m031.html

https://en.wikipedia.org/wiki/List_of_Messier_objects