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Home , Big Dipper, Star Walk

Names: ______

______

Grade

Exploring the : Wheels and Star Walk

Always old, sometimes new.

Never sad, sometimes blue.

Never empty, sometimes full.

Never pushes, always pulls.

What is it?

______Pre-Lab Quiz

Record your team’s answers as well as your reasonings and explanations.

1.

2.

3.

4. Part 1: Using a Star Wheel

1. Dial up 9 pm on your star wheel by aligning today’s date with 9 pm. Find a that has just risen. Find a constellation that has just set.

Hint: how can one simulate the passage of time throughout the night on a star wheel?

Rise Set

2. The point about which the sky rotates in the northern hemisphere is called the North Celestial Pole (NCP). What star is associated with the NCP and what constellation is it part of?

3. The zenith is defined as the point on the celestial sphere directly above an observer. On the star wheel, the zenith will be at the center of the visible portion of the sky. What constellation will be closest to the zenith at 9 pm tonight?

4. The meridian is a great circle on the celestial sphere that passes through the north and south celestial poles and an observer’s zenith. List some that will be along the meridian at midnight tonight. 5. The word circumpolar is used to denote objects that never set below the horizon, and thus are visible at all times of the year.

a) Using the star wheel, list three circumpolar constellations for Iowa City.

b) Where would one look to find them?

6. Where would one currently look to find (Big Dipper)?

7. The Summer Triangle consists of the three bright Altair, Deneb, and Vega. While it isn’t a constellation, it is one of the most famous "asterisms" (pattern of stars) in the night sky. During which months will it be visible at midnight?

8. The Orion constellation is home to the picturesque Orion , a popular target for amateur astronomers (The Stargazer’s Handbook, pg. 124). Will Orion be visible tonight? If so, during what times? If not, when will it become visible in the early morning (4 am) again? 9. More than half of all stars are thought to be part of a system with two or more stars. Two of the most famous multi-star systems are - and Albireo.

a) Mizar-Alcor (pg. 34) is part of the constellation Ursa Major. What is special about this system?

b) Albireo (pg. 54) is part of the constellation Cygnus. Why is this a popular object for viewing with a small telescope?

10. (Guardian of the ) is the fourth brightest star in the night sky and is located in the constellation Boötes. Draw a diagram of the Big Dipper and illustrate how to find Arcturus and using the Big Dipper as your starting point. Also label Mizar-Alcor. Part 2: Star Walk

Our Milky Way is a spiral galaxy, which means that it is relatively flat with spiral arms protruding from a central bulge. Seen edge-on, it would look something like this:

At the center of our galaxy is a black hole with a mass of about 4 million . The inner part of our galaxy is home to a bright region called the bulge that contains mostly old yellow and red stars.

The disk of our galaxy contains younger stars and has a bluish appearance due to the very luminous (but short-lived) blue stars that exist in star-forming regions, which contain a lot of gas and dust. An is a loosely bound collection of stars that were recently a star-forming region, but have lost their gas and dust.

Our galaxy also contains a halo with globular clusters. A globular cluster is a dense collection of stars that are gravitationally bound together. Using Star Walk

On the left-hand side of the screen is a scroll bar that allows you to set the viewing wavelength. Make sure that it is set to "Visible".

Note that the app doesn’t always get the cardinal directions (N, S, E, W) correct in the lab room or on the roof.

1. Locate the Big Dipper and use it to find Polaris and Arcturus, along with their associated constellations. What objects do these constellations represent?

Constellation Object

Ursa Major

Ursa Minor

Boötes

2. Find the dark and colorful band running across the sky. What does this band represent?

3. Find the dashed yellow line on the app.

a) What does this line represent?

b) What celestial objects are located near this line? 4. Click the menu button at the bottom right and select "Sky Live".

a) What is the current phase of the moon? What side is illuminated?

b) List some that will be visible at midnight tonight.

5. The center of our galaxy is located in the constellation Sagittarius (pg. 152–57).

a) Click the search button at the bottom left and find Sagittarius. Is it currently above the horizon?

b) What is the large bright feature called that is partially obscured by dust?

c) What are three reasons for why astronomers believe that Sagittarius A* is a black hole? 6. Shooting stars (meteors) are not the only fast-moving objects observed in the night sky. Occasionally, pass overhead as well, which can appear quite bright and their passover can last several minutes.

a) Find the International Space Station (ISS), click on it and then click the information button, . When is the next time the ISS will be overhead during the night? ⓘ

b) Click the time menu at the top right. Change the time by selecting what unit you want to change (e.g. the hour) and using the scroll bar on the right to adjust the value. Near what constellations will the first rise and set?

Rise Set

7. Two iconic star clusters are M13 and NGC 3603. The former is found within Hercules, while the latter is found in Carina (the keel), which joins with Vela (the sails) and Puppis (the stern) to form Argo Navis (The Ship Argo).

a) How many stars comprise the globular cluster M13? (pg. 46)

b) Within the star-forming Carina Nebula lies the open cluster NGC 3603. How did this star cluster lose its gas and dust? (pg. 182) 8. The Milky Way is on the outskirts of a large collection of known as the Supercluster, which is dominated by the central Virgo Cluster. The Virgo Supercluster is an appendage to the larger Laniakea Supercluster. a) Using Star Walk, find three examples of spiral and elliptical galaxies in the Virgo Cluster.

Hint: Once you found Virgo, try zooming in to see the galaxies. You can also click to learn more about a galaxy, including its type. ⓘ

Spiral Elliptical

b) The largest galaxy in the Virgo Cluster is Messier 87 (pg. 92). How many Milky Way galaxies could stretch from one end of this galaxy to the other? The diameter of the Milky Way is about 100,000 light years for comparison.

c) The Milky Way is only about ~1000 light years in thickness. How many Milky Way pancakes could one stack from one end of M87 to the other? Part 3: Observing the Night Sky

1. Find the following objects in the night sky and point them out to your TA.

Object Type TA

Arcturus Star

Big Dipper

Mizar-Alcor

Polaris Star

Summer Triangle Asterism

2. Estimate the azimuth, altitude, and angular size (if applicable) of the following objects.

Object Azimuth Altitude Angular Size

Arcturus X

Big Dipper

Mizar-Alcor X

Polaris X

Summer Triangle

3. Measure the angular distances of Arcturus and Polaris from the Big Dipper’s handle and ladle respectively and add the values to your chart in Problem 1.10.