A white dwarf is the remnant of a medium-mass star, but to scale, it is much larger than the two possible remnants of a massive star--a neutron star, and a black hole, which actually has zero size (but is surrounded by an event horizon, which we'll discuss later).
However, while the white dwarf is the largest of these stellar remnants, it is not the most massive--a neutron star is more massive, and a black hole is more massive still.
All of these stellar remnants are incredibly dense, but which stellar remnant is densest? Least dense?
Note the space-time depressions around stars, but also the funnel-shaped distortion caused by something that doesn't seem to be there at all--this is the effect of a black hole on space-time. Remember that black holes can't be seen, but its effects on space-time--its gravitational field--can definitely be felt. And like the Lake Berryessa water outlet, you can get near it and get back out to safety provided you can move quickly enough, but there is an imaginary boundary around it at which you could not escape, no matter how fast you can move--this boundary, or point-of-no-return, for everything including light is the black hole's "event horizon." (Video link: "Black hole deforms space.")
Here's that same funnel shape representing distorted space-time caused by a black hole. We'll throw in some marbles, taking care to throw them in a tight clump. At first, the clump of marbles will begin slowly spread out, but after circling the "black hole" the marbles will spread out from each other, forming a long line--spaghettification--due to this funnel shaped distortion of space-time!. Although we can't really show the effect of time dilation, there is a crude analog to this from the nature of this funnel-shaped distortion of space-time, as it seems like it takes longer and longer for the marbles to get down further and further into the throat of the funnel. (Video link: " Gravity Well (Reuben H. Fleet Science Center, San Diego, CA).")
So next time you see a charity donation funnel, try this for yourself--don't just roll in one coin, toss in several very closely bunched together, and watch the tidal effects stretch them out, and think about time dilation effects as they seem to take longer and longer to get further and further down the "throat" of curved space-time!
In the subsequent in-class activity you will distinguish between companion stars with compact objects--whether white dwarfs, neutron stars, or black holes.