APOD Astronomy Picture of the Day Write in your blue book Astronomy Calculations Lecture (use your Conversion Chart) Homework: Chapter 1: Read pp. 1-7 and answer the questions p. 8 Review Questions 2, 3, 9, 10 and Problems 1, 2, 3, 5, and 9

APOD “Do Now” APOD (Astronomy Picture of the Day) In your blue book: 3- observations 2- facts (student reader will help decide) 1- Why is this important? ia/dwarf-spiral-collision.html Make a sketch to help you remember. You will use the blue book for any test or quiz questions.

APOD “Do Now” In your blue book: 3- observations 2- facts (student reader will help decide) 1- Why is this important? ia/dwarf-spiral-collision.html

Dwarf Galaxy Caught Ramming Into a Large Spiral Galaxy Observations with NASA’s Chandra X-ray Observatory have revealed a massive cloud of multimillion-degree gas in a galaxy about 60 million light years from Earth. The hot gas cloud is likely caused by a collision between a dwarf galaxy and a much larger galaxy called NGC If confirmed, this discovery would mark the first time such a collision has been detected only in X-rays, and could have implications for understanding how galaxies grow through similar collisions. An image combining X-rays and optical light shows the scene of this collision. The impact between the dwarf galaxy and the spiral galaxy caused a shock wave − akin to a sonic boom on Earth – that generated hot gas with a temperature of about six million degrees. Chandra X-ray data, in purple, show the hot gas has a comet-like appearance, caused by the motion of the dwarf galaxy. Optical data from the European Southern Observatory’s Very Large Telescope reveal the spiral galaxy in blue and white. X-ray point sources have been removed from this image to emphasize the diffuse emission. Near the head of the comet-shaped X-ray emission (mouse over the image for the location) is a region containing several very optically bright stars and enhanced X- ray emission. Star formation may have been triggered by the shock wave, producing bright, massive stars. In that case X-ray emission would be generated by massive star winds and by the remains of supernova explosions as massive stars evolve. The mass of the entire gas cloud is uncertain because it cannot be determined from the two-dimensional image whether the hot gas is concentrated in a thin pancake or distributed over a large, spherical region. If the gas is a pancake, the mass is equivalent to forty thousand Suns. If it is spread out uniformly, the mass could be much larger, about three million times as massive as the Sun. This range agrees with values for dwarf galaxies in the Local Group containing the Milky Way. The hot gas should continue to glow in X-rays for tens to hundreds of millions of years, depending on the geometry of the collision. The collision itself should last for about 50 million years. Therefore, searching for large regions of hot gas in galaxies might be a way to estimate the frequency of collisions with dwarf galaxies and to understand how important such events are to galaxy growth. An alternative explanation of the X-ray emission is that the hot gas cloud could have been produced by supernovas and hot winds from large numbers of massive stars, all located on one side of the galaxy. The lack of evidence of expected radio, infrared, or optical features argues against this possibility. ia/dwarf-spiral-collision.html

Check with Your Neighbor Cosmic Questions What does “universe” mean? How big is the universe? What is the largest thing in the universe? What is the smallest thing in the universe? How old is the universe? These will all be addressed during this course! Here, though, are some quick answers:

Cosmic Answers: There are many definitions to “universe” ◦Earth, visible universe, causally connected, etc. ◦ ◦The Universe is defined as everything that physically exists: the entirety of space and time, all forms of matter, energy and momentum, and the physical laws and constants that govern them. However, the term "universe" may be used in slightly different contextual senses, denoting such concepts as the cosmos, the world or Nature.physicallyexistsspacetimematterenergymomentumphysical lawsconstantscosmosworldNature Size of visible universe: 13.7 billion light years in radius Largest thing: Superclusters (100 million light years across) Smallest thing: electron, photon, neutrino, other fundamental particles Universe Age: 13.7 Billion light years

Learning to Look (3) Of the objects listed here, which would be contained inside the object shown in the photograph? Which would contain the object in the photo? Starts Planets Galaxy clusters Filaments Spiral arms

Answer The object is a galaxy. It contains stars with their planets and spiral arms which are all smaller than the galaxy. The larger, galaxy clusters and filaments are made of galaxies.

Learning to Look (4) In the photograph shown here, which stars are brightest, and which are faintest? How can you tell? Why can’t you tell which stars in this photograph are biggest or which have planets?

Answer Most stars are so far away that their angular diameters, as viewed from Earth, are well below detectable limits. On photographs, the diameter of a stellar image is related to its apparent intensity or apparent brightness of the star. Bright stars will have a larger diameter on the photographic image than fainter stars, regardless of the stars’ physical sizes. Thus you cannot tell which stars are physically larger. Similarly, planets around the star cannot be seen in the photograph.

How are you doing? Label paper #1-5

1. How many centimeters are there in one kilometer? , , ,  10 6

Scientific notation is used in science because 1.it makes it easy to write big or small numbers. 2.all astronomical distances are expressed in metric units. 3.it makes conversions between units easy. 4.all of the above

The speed of light is 3.0*10 5 km/sec, and it takes light 1.3 sec for light to travel from the moon to Earth. From this information, what is the distance to the moon? 1.390,000 km 2.230,000 km km km  10 5 km

2.9  10 7 is the same as thousand 2.29 thousand thousand million 5.29 million

The numbers 9.81*10 5 and 981,000 are equivalent. 1.True 2.False

ANSWERS