Assessment 9: Size of the Universe

Measuring Distance

Scientific Notation: Use powers of 10 to write very large or very small numbers in shorter form

Light Year: Light travels at the speed of 300,000,000 meters per second. That 300,000km a second!

Astronomical Unit: Distance from the Sun to the Earth. Equal to 150,000,000km or 150,000,000,000m What would that be in scientific notation?

Parallax

Apparent change in position of an object when you look at it from different places.

We can find the distance of a star by measuring its parallax.

Compare the movement of the new star to distant stars. The less the star moves, the further away it is.

Parallax at work

This animation by Frog Rock Observatory shows the movement of Barnard's Star across the sky from 1985 to 2005. Barnard's Star is approaching the Sun so rapidly that around 11,700 AD, it will be 3.8 light years from the Sun - and thus the closest star to our own! (Garcia-Sanchez, et al, 2001)

Stars are NOT stationary

Universe, Galaxy, Solar System

The universe consists of all the solar systems and galaxies. There are hundreds of billions of galaxies in the universe.

A galaxy contains hundreds of billions of stars, many of which have planets.

A solar system is a stars(s) that has objects orbiting it within a galaxy.

Start with the small (solar system)

Solar System Characteristics

Our solar system only has one star, the sun. However, many solar systems have a binary star system. This occurs when there are 2 stars in one solar system. This is the case with one of our closest stars, Alpha Centauri.Often, the brighter star is the only one you will be able to see, as the case is with Alpha Centauri. When this is the case, the gravity from the second star will cause the bright star to wobble.

Galaxy

Galaxies aren’t individual objects, but vast groupings of stars.

In fact, “vast” isn’t a big enough word to describe how many stars there are in galaxies.

A dwarf galaxy can have as few as 10 million stars. These dwarf galaxies are constantly being absorbed into larger and larger galaxies.

The Milky Way contains 200 billion stars – 200,000,000,000 stars.

The nearby Andromeda galaxy is much more massive than the Milky Way and contains 1 trillion stars; 5 times as many stars as the Milky Way.

Types of galaxies

Elliptical Galaxy

Irregular Galaxy

Spiral Galaxy

Quasars- A bit of the unknown

Discovered in the 1960’s, these are extremely bright, distance objects that look like stars. These are believed to be active young galaxies with huge black holes in the center, surrounded by gas which heats up and glows.

Quasars are difficult to identify

In the image to the left, taken using the Hubble Space Telescope, the bright blob on the left (surrounded by four diffraction spikes) is a quasar; the bright blob on the right is a star. See any difference? Not really - quasars and stars are both unresolved sources of light. To distinguish between them, we need a spectrum. [Image credit: C. Steidel (Caltech) & NASA]

Where we are located in our galaxy

Our Closest Galaxy to the Milky Way

The Canis Major Dwarf Galaxy is only 25,000 light years from the Sun, and 42,000 light years from the Galactic center. It too, is well-hidden by the dust in the plane of the Milky Way - which is why it wasn't discovered until recently.

To get to the closest galaxy to ours, the Canis Major Dwarf, at Voyager's speed, it would take approximately 749,000,000 years to travel the distance of 25,000 light years! If we could travel at the speed of light, it would still take 25,000 years!

Voyager NASA's Voyager 1 spacecraft

is the most distant human-made object in the universe.

Its twin, Voyager 2, has traveled to more planets than any other in history.

The spacecraft twins, Voyager 1 and Voyager 2, were launched by NASA during the summer of 1977 from Cape Canaveral, Florida.

Barring any fatal equipment failures, the Voyager twins are likely to survive and relay data from beyond the outer planets for many decades into the 21st century.

Voyager 1 is about 8.7 billion miles from the Sun and traveling at a speed of 3.6 AU per year while Voyager 2 is about 6.5 billion miles away and moving at about 3.3 AU per year. Or, less than one light day.

Ultra Deep Field

A tale of 2 stars.

Proxima Centauri Our closest star,

4.22 light years away (3.97 × 1013 km) (Or 271,000 AU.)

Red Dwarf Star

Alpha Centauribrightest naked-eye

(apparent) star to the sun

4.35 light years from the sun

Part of the constellation Centaurus