Curriculm connections: Astronomy and by extension astrophysics is fascinating to the general public but largely absent from high school curricula. However, it's easy to fit it in. Dark Matter and Black Holes can be measured using Newton's Uuniversal Law of Gravity, his Second Law of Motion and his equations for circular motion. The Schwartzchild radius can be calculated using the conservation of energy, where kinetic energy is changed into gravitational potential energy. The evidence for Hubble's Law comes from the Doppler Effect and using d = vt with the Hubble Law lets the students calculate the age of the universe.
1) Dark Matter
It seems that the majority of mass in the universe (80%!!) cannot be seen. This is not because it is very dim. It is because it is made of a new type of matter that does not interact with light. We don't know what it is, but we have given it a name - dark matter. The evidence for dark matter can be understood and studied by high school students - even those who are just starting high school. This evidence has really strong ties to a standard curriculum that never mentions dark matter.
2) Dark Energy - This is a very difficult topic but you can find some activities dealing with this in the new resource from the Perimeter Institute called The Expanding Universe. However, your best bet is to go to the eleventh unit of Physic for the 21st Century. This has an excellent 30-minute video that looks at two of the lines of evidence. It also has a lesson with activities and a simulation.
3) The Big Bang
It seems that the universe started as a very small, hot place just less than 14 billion years ago. Even more fascinating than this, is understanding how we know this. The main ideas can be explored by students as young as 12 and there are a number of activities that can help them examine the data and explore what it means.
4) Black Holes
Most students have heard of black holes, but most of what they know is confused or really wrong. You can use your students' interest in black holes to motivate using Newton's Laws of gravity and circular motion to measure the mass of a black hole. A beginning understanding of what is a black hole starts with consrevation of energy and the speed limit of light. You can explore how we know what we know and how our models of gravity have changed.