Wonders of the Sky

Wonders of theDark Sky

Twinkling: Star Scintillation

• Why do stars twinkle? Stars twinkle because their light is distorted as it passes through earth’s atmosphere

• Also termed scintillation

• The steadiness of air is termed seeing

• Seeing is poor if stars appear to twinkle to the unaided eye

Star Scintillation (twinkling)• Images of a single

star

• Ideal star resembles a “bull’s eye” pattern

• Atmospheric Refraction

• Objects low in the sky appear with rainbow tints

• Atmosphere distorts light from objects like a prism into colors

• Mainly views of planets such as Venus in a telescope

Why do Star’s Twinkle?

Turbulent air causes a star’s image to distort

Venus Refraction

Star Colors: Big & Little Dippers

Where is Polaris?

Orion

Betelgeuse

Rigel

•Look for these star colors when you see Orion

Belt

Sword

Orion Nebula in Sword of Orion

Meteors

• Meteors or shooting stars represent the burning (from air friction) in our atmosphere of particles from space

• A particle the size of a grain of sand produces the typical meteor or “shooting star”

• A fireball, a brilliant, shadow casting meteor, is by objects as large as a basketball

• A bolide is a fireball that appears to break apart during flight

• Some bolides have been reported to emit rumbling or booming sounds

Leonid Meteor & Big Dipper

http://www.astropics.com/leonids/l02bd.htm

Leonid Meteor & Pleiades

http://www.astropics.com/leonids/l01ss.jpg

Fireballs

http://www.southdowns.org.uk/images/fireballB.jpg

Peekskill Bolide

http://starchild.gsfc.nasa.gov/Images/StarChild/solar_system_level2/fireball_big.gif

This bolide scattered several meteorites across the northeastern United States

Meteorite 1, Car 0

•A meteorite, a fragment of the Peekskill bolide, penetrated the trunk of this car

•The actual meteorite is displayed below the car

Meteor Showers

• Meteors are visible every night, these are termed sporadics

• Other meteors fall in predictable showers

• Meteor showers are produced when the earth passes through the trail of debris cast off by a comet

• Earth passes through these trails on the same evenings each year

Radiant

• Meteor showers are named for the constellation from which the meteors appear to originate

• For example, Perseid meteors originate from the constellation Perseus

• The exact point of origin is termed the radiant

Shower Origins

• Meteor showers occur on the same evenings each year as the earth passes through the debris shed by comets

Leonid Meteor Shower

“Falling Stars” & Sirius

http://www.astropics.com/leonids/l01nsf.htm

Sirius is the night

sky’s brightest

star

Leonid Radiant

Meteor Videos

• Alberta Meteor 2008

• Peekskill, NY Meteor 1992

Forecast: Meteor Showers

Main Meteor ShowersQuadrantids—Jan 03

Lyrids—Apr 21Eta Aquarids—May 04

S. Delta Aquarids—July 29Perseids—Aug 11-12

Orionids—Oct 20Leonids—Nov 17

Geminids—Dec 13-14

Leonid Meteor Storm• One annual shower,

the Leonids, has the potential to produce immense meteor storms

• During a meteor storm, thousands of meteors per hour occur

• Leonid storms can occur every 33 years, and the last occurred in the late 1990s

http://www.mreclipse.com/Meteors/Leo01/image/Leonid1833-1x.GIF

Dust in the Solar System: Zodiacal Light

• In certain seasons, a faint, pyramid-shaped glow is visible above the horizon which is termed the zodiacal light

• The Zodiacal light is visible along the ecliptic, the region of the zodiacal constellations

• This glow results from sunlight reflected from dust in the solar system’s plane

• Also known as the false dawn

Zodiacal Light

Zodiacal Light & Meteor

http://epod.usra.edu/archive/images/img_3491-1.jpg

Zodiacal Light in Gemini

http://www.allthesky.com/various/preview/zodiacgeminim-p.jpg

The zodiacal light is found along the zodiac or ecliptic

False Dawn

• Note the zodiacal light in the left of this all-sky image

• The Milky Way is visible stretching from upper right to lower left

Night Glows

http://www.arizonaskyvillage.com/assets/images/autogen/a_Copy_of_Zodiacal_Light___milkyway.jpg

Photo from southeast Arizona

Right: Milky Way, Left: Zodiacal Light

Dust in the Solar System: Gegenschein

• The gegenschein is also an effect created by solar system dust

• Gegenschein is German for “counterglow”, it is a brightening of the sky in the direction exactly opposite the sun

• Extremely dim and difficult to observe

http://www.astrosurf.org/lombry/Documents/gegenschein-15mar1980.jpg

•This all-sky image shows the gegenschein, zodiacal light, and Milky Way

Comets

• Comets are icy bodies from the outer solar system

• When near the sun, comets emit tails of particles and gas

• Appear as glowing shapes in the night sky

• Appear to move against stars in background

Dusty Comet (McNaught)

Comet McNaught, January 2007

Comet Lulin (2009)

Comet Holmes (2007)

• Comet Holmes developed a huge gas cloud (coma), that became larger in volume than the sun

Comet Holmes in Perseus

Comet Hyakutake (1996)

Northern Lights

• The northern lights or aurora borealis is one of the most dramatic of the sky wonders

• Usually visible from high latitudes (Link)

• Can be seen rarely from cont. United States

• Results from glowing gases created by the interaction of earth’s atmospheric gases and radiation from the sun (solar wind)

http://www.thisisthelife.com/photos/experiences/large/aurora-borealis.jpg

Appearance of Aurora

• Resemble light shows that ripple and swirl like waving curtains or billowing plumes of colored smoke

• Usually green in color, range from gray, to green, to red

• Each color represents a different gas; oxygen is green, nitrogen is red

Aurora from Norway

Church, Aurora Borealis, 1865

Red Aurora

http://www.livingwilderness.com/patterns/nlights2.html

Wow!

http://www.eielson.af.mil/library/news/05nsvs/feb05/Feb_4/Aurora%20borealis.jpg

Norway, March 08

Aurora from Space Shuttle

Airglow• Airglow is a very

dim glow present all through the atmosphere

• It is created by a process similar to the northern lights

• Airglow can be identified in long-exposure photos of the sky

• The all-sky view at right was taken in Hawaii, the airglow is visible as streaks

Bands of Airglow

Airglow from Space

• Airglow is visible as a green layer in this photo from space

Airglow from ISS

The Best Dark Sky Sight:The Milky Way

• From a dark sky, the Milky Way is a naked eye spectacle

• Appears as a delicate, misty band of light that arches the sky

• Bright glowing clouds and dark lanes are also visible in the Milky Way band

• MW represents the light of thousands of stars too faint to be seen directly

• MW is our view from within our galaxy• Using a telescope, Galileo discovered that the

Milky Way was composed of stars in 1609

Milky Way Starfields

Summer MW

•The Milky Way arches across the entire sky during early evening in summer

•The photo shows a view to the southwest in late summer

Home Galaxy

•How our galaxy would appear from space

Looking straight down on the Milky Way

All-sky MW photo

from Hawaii

Whole Sky

View, Hawaii

•The galaxy’s center lies in the center of this all-sky image

•Note the faint zodiacal band running horizontally through the center of the image

Lund Milky Way Panorama

http://antwrp.gsfc.nasa.gov/apod/ap970517.html

Mellinger Panorama

Naked Eye Wonders of the Sky

• Most celestial objects (galaxies, star clusters, nebulas) require a telescope to be seen

• A few of these objects are bright enough to be seen with the naked eye

• Objects:– Beehive Cluster– Pleiades– Double Cluster– Orion Nebula– Andromeda Galaxy

Beehive Cluster (M44)

• A bright star cluster located in the constellation Cancer

• Resembles a swarm of bees when seen in binoculars

• To the eye, appears as a glowing spot in the sky

• Romans used it as a predictor of weather. If invisible, meant rain was coming

• M44 is an open star cluster containing 200 stars. It is located 515 light years from earth

• Next Slide: Beehive visible to upper right of eclipsed sun

M44 and Eclipse

Cancer Star Map

•Cancer the Crab is a spring season constellation

Pleiades: Seven Sisters

• A bright star cluster located in the constellation Taurus

• Resembles a tiny “little dipper” (real LD is Ursa Minor). About 7 stars visible to naked eye

• Celebrated since ancient times, appears in mythology of many cultures

• Open star cluster containing about 100 stars. Located 407 light years from earth

Seven Sisters

Pleiades Deep Image

Taurus Star Map

•Taurus the Bull is a winter constellation

•The bright star Aldebaran marks the eye of the Bull

“Taurus” Cave Painting

•Cave painting in Lascaux, France

•Thought to represent Taurus with Pleiades at upper right of Bull

•Estimated age of painting, 14,000 BC

Perseus Double Cluster

• Twin open star cluster located in constellation Perseus

• Bright glowing shape in night sky, telescope reveals countless stars

• Located about 7000 light years from earth

Perseus Star Map•Perseus is an autumn constellation

•In mythology, Perseus slew the snake-haired Medusa

•The Double Cluster is labelled “h + x” in upper right

•The Double Cluster is easy to spot between Perseus and the “W” of Cassiopeia

Andromeda Galaxy

• Our nearest large neighbor galaxy

• Similar in size and shape to Milky Way

• Andromeda Galaxy is visible to the naked eye as a glowing spot in the constellation of Andromeda

• Galaxies like Andromeda and our Milky Way are composed of billions of stars

• 2.3 million light years distant (wave!)

Andromeda Constellation

Locate M31 and M33

Andromeda Spiral

Orion Nebula

• Bright nebula (glowing cloud of gas) located below Orion’s Belt

• Represents a place where stars are born

• Nebula located a bit over 1300 light years from earth

Orion’s Sword•Orion is a winter constellation•Note bright stars Betelgeuse (upper left) and Rigel (lower right)

Orion Psychedelic

Light Pollution

• Stargazing is difficult in the city

• Excess artificial light that enters the night sky is termed light pollution

• Observatories are built in remote places away from cities if possible

http://www.apstas.com/astrotas/glow.jpg

Light Pollution: Got Stars?

http://www.spaceweather.com/swpod2003/20aug03/Carlson1.jpg

Light Pollution near Tenerife, Canary Islands

Earth at Night (Click Below)

http://veimages.gsfc.nasa.gov//1438/earth_lights_lrg.jpg