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Constellations & Galaxies
“The Milky Way has gone a little sour”
- Sam Roberts
Constellations
• Groups of stars that form shapes or
patterns
– must be officially recognized
– if not, the pattern is called an asterism
• named after ancient heroes/gods, animals
or everyday objects
Test Your Knowledge
• Q: Is the “Big Dipper” an asterism or
constellation
• A: Asterism
• The big dipper belongs to the constellation
Ursa Major (The Big Bear)
Ursa Major (The Big Bear)
Ursa Minor (The Little Bear)
Polaris
Polaris
Polaris
• Find Polaris in the night sky and you can
always find North
• It is commonly known as “The North Star”
• This is merely a geographical coincidence
• there is no “South Star”
– Sigma Octantis is in the right location but it is so
faint to the naked eye that it is useless
Arcturus & Spica
• Arcturus
– 4th brightest star
– Brightest star in the
constellation Bootes
• Spica
– 15th brightest star
– Brightest star in the
constellation Virgo
• To find them, locate
the Big Dipper and
remember “Arc to
Arcturus, then speed
on to Spica”
Orion
Cassiopeia
Hercules
Zodiac Constellations
• Form a ring that the Sun seems to pass through
each year as the Earth orbits around it.
• perhaps the most famous of all constellations
because of their use in astrology
• There are 13 in total
–
–
–
–
Aries
Taurus
Gemini
Cancer
Leo
Virgo
Libra
Scorpius
Pisces
Sagittarius
Capricornus
Aquarius
Ophiuchus
Cancer (The Crab)
Sagittarius (The Archer)
Gemini (The Twins)
Galaxies
• A galaxy is a large collection of gas, dust
and hundreds of billions of stars
• Earth and the other planets are a part of
the Milky Way Galaxy
– Appears as a hazy white band in the night sky
• Andromeda is the nearest major galaxy
The Milky Way
Andromeda
Types of Galaxies
1. Spiral
– have a spiral shape
- arms of spiral are mainly gas, dust and bright,
young, blue stars
2. Elliptical
– shaped like a football
- composed of old stars
3. Irregular
– no familiar shape
NGC 1232
M81
M51
Spiral Galaxies
Elliptical Galaxies
NGC 5253
M87
Irregular Galaxies
NGC 1705
Star Clusters
• Groups of stars that are close together and travel
together are known as star clusters
• Star clusters are part of galaxies
• Open clusters
– contain about 50 to 1000 stars
– dispersed along the Milky Way’s main band
• Globular clusters
– Contain 100 000 to 1 million stars arranged in spherical
shapes
– Do not lie along the band of the Milky Way
RCW 108
The Pleiades
Open Star Clusters
The Pleiades
• also known as M45 or the Seven Sisters
• located in the constellation of Taurus
• dominated by hot, blue stars, which have formed
within the last 100 million years.
• Of all clusters close to the Earth it is the best
known and most striking to the naked eye
Harry Potter and the Observable Universe
http://astronomyspace.suite101.com/article.cfm/astronomical_names_in_harry_potter