What type of stars have a very low temperature and a very high absolute magnitudes?

The red giants are very bright and have a relatively low temperature, but they are still red hot, that's why they glow red and not white. Have a look at Betelgeuse or Aldebaran in binoculars, or Antares if you get a chance in the summer, and compare them with a white star like Rigel or Vega.

Of what substance are the inner planets mostly composed of?

The inner planets, including Mercury, Venus, Earth, and Mars, are composed mostly of rock and metal. They have solid surfaces and relatively high densities compared to the outer gas giants.

What is the surface temperature of the star Sadalsuud?

Sadalsuud, also known as Beta Aquarii, has a surface temperature of approximately 6,000 to 6,500 Kelvin. This places it in the category of a spectral type G star, similar to our Sun. Its relatively high temperature contributes to its brightness and distinct yellowish hue in the night sky.

Why does a cool distant supergiant star such as betelgeuse have a high luminosity?

Betelgeuse, a cool distant supergiant star, has a high luminosity primarily due to its large size and surface area. Despite its relatively low temperature, its vast volume allows it to emit a significant amount of energy. The combination of its expansive radius and the Stefan-Boltzmann Law, which states that a star's luminosity increases with the fourth power of its temperature, results in Betelgeuse's impressive brightness. Thus, even with a lower temperature, its sheer size compensates, leading to high luminosity.

What type of stars have high absolute magnitude but low temperatures?

Red giants.