A Trip Through the Universe Part II. What are binary stars?

A Trip Through the UniversePart II

What are binary stars?

What are constellations?

What is an asterism?

How do you find Polaris from Ursa Major?

What are circumpolar constellations?

• What are some circumpolar constellations for our area?

Nova• Nova: A star that suddenly increases in

brightness in just a few hours or days.• With a nova, the star may get up to 100 times

brighter.• Novas are believed to be caused when a star in

a binary-star system captures gas from the companion star.

• This gas strikes the surface of the nova star, causing a nuclear explosion.

• After a nova, the star returns to normal.• Many novas are reoccurring.

1In January 2002, this star, now called 838 Monocerotis, became a nova. Its temperature increased to 600,000 its normal temperature, making it temporarily the brightest star in the Milky Way.

It has since returned to its normal brightness.

The explosion that you see is the shell of dust around the star as it is being lit up by the increased light of the eruption.

This is known as a “light echo.”

Supernova• Although this is a similar term, a nova and a supernova

are very different. • A supernova is when a massive star that has a

tremendous increase in its energy output due to a catastrophic explosion of its core.

• Supernovas can light up the sky for many weeks.• The core of the star becomes tremendously hot, fusing

iron atoms into new elements.• Huge clouds of dust, gas, and the new elements explode

into space.• This forms a new nebula.• Once a star supernovas, the core that remains of it will

become either a neutron star or a black hole.

SN 1986 Supernova remnants

The two photos are of the same part of the sky, taken in 1987. The one on the left is after SN 1987A had its supernova. Supernovae are one of the most energetic explosions in nature, making them like 1028 megaton bomb. http://imagine.gsfc.nasa.gov/docs/science/know_l2/supernovae.html

Kepler’s Supernova Remnant—this star supernovaed over 400 years ago.

Star Cluster• Stars that appear to be grouped together

are said to be “clustered” together.

• There are two types of star clusters.

• Open Clusters: Unorganized clusters of stars with hundreds of stars.

• Globular Clusters: Clusters of stars that are grouped in a spherical shape and often contain more than 100,000 stars

Magellanic Open Star Clusters

M80 Globular Cluster

Star Clusters

• Both types of star clusters appear to be a faint, white cloud when viewed from Earth without a telescope.

• When a telescope is used to view them, the different stars begin to be visible.

Nebula

• Nebula: An diffuse area of dust and gas where stars are born.

• Nebulae are best seen with infrared, ultraviolet, Xrays and radio waves.

• These huge clouds of dust and gas between stars glow with heat rays.

Eagle Nebula

Eagle 2 Nebula, M16

Close-up of Eagle Nebula

Orion Nebula

Boomerang and Cat’s Eyes Nebulae

Galaxies• A galaxy is a huge group of stars, gas,

and dust that are gravitationally bound.

• How big is the Milky Way?

• It is 100,000 light years wide…In other words, it would take light 100,000 years to travel across it. Even so, the Milky Way is only one tiny piece of many, many galaxies.

• The Milky Way is a spiral galaxy.

Spiral Galaxy

• Spiral Galaxies are shaped like pinwheels. They have huge arms that twirl around the central core.

• This is Messier 101 galaxy

Barred Spiral NGC 1300

Elliptical Galaxies

• Elliptical galaxies can be almost spherical to flat disks..

• Elliptical galaxies have very little dust and gas.

• These galaxies tend to be much older than other galaxies.

• (Remember that a nebula a huge area of dust and gas where stars are born)

Elliptical Galaxy M87

Anglo-Australian Telescope

Irregular Galaxies

• Irregular Galaxies tend to be in irregular shapes.

• The closest galaxies to the Milky Way are irregular.

• Irregular galaxies are much less common than spiral and elliptical galaxies.

NGC 1705

Irregular Galaxy

The Milky Way

• Our galaxy is a huge pinwheel shaped disk with a bulge in the center.

• Older stars in the Milky Way tend to be in the center of the galaxy.

• Stars in the center of the galaxy are crowded much closer together than those in the spiral arms.

The Milky Way

• Scientists believe the Milky Way is 100,000 light years in diameter and about 15,000 light years thick.

• There are nearly 100 billion stars in the Milky Way. Our sun is one of these.

• Our sun is located on one of the spiral arms, about 30,000 light years from the center.

• Our sun is one of the younger stars in the Milky Way.

• All stars in the Milky Way rotate counter-clockwise about the center.

Big Bang Theory

• The theory that everything in our universe started with one big explosion.