Which two planets, as seen from Earth, go through phases like the Moon?

Which two planets, as seen from Earth, go through phases like the Moon?

Jupiter and Mars.

Mercury and Mars.

Mercury and Venus.

Venus and Mars.

If a star cluster is in the plane of our galaxy and has lots of very massive "A" type stars, what kind of cluster is it and how old is it?

It is probably a 10 billion year old globular cluster passing through the plane of the galaxy that has picked up some massive, young stars during its repeated passes through the disk.

It is probably a globular cluster that is only about 100 million years old.

It is probably an open cluster that is about 8 billion years old.

It is probably an open cluster about 500 million years old.

What differences would we expect to observe on the Sun if it did NOT rotate differentially?

The corona would be much hotter than it is now.

It would exhibit violent surface activity continually, including flares and sunspots.

It would exhibit very little surface activity, and there would be no sunspot cycles.

X-ray images of the Sun would show more intense X-ray emission than it does now.

Suppose a collapsing interstellar gas cloud had a composition almost entirely of helium and a few percent heavier elements, but no hydrogen.

A planet-like object would form in all cases, regardless of the mass of the cloud.

If the mass is sufficient, a star could form but would take longer than normal because 100 million Kelvins would take longer to achieve.

Formation of a star would be impossible, because the central temperature would never be high enough for fusion to occur.

Before the central temperature could reach the threshold for nuclear fusion, the object would form a black hole.

Which star was the best "North Star" when King Tut ruled Egypt.

Deneb.

Thuban.

Polaris.

Vega.

Suppose you observe a main-sequence 2 solar mass star orbiting an 8 solar mass object too dim to detect. What is the most likely identity of the dim object?

The object is probably a white dwarf.

The object is probably a brown dwarf.

The object is probably a black hole.

The object is probably a neutron star.

Would a planet orbiting a red giant star be the best place be searching for life?

Yes, because cooler stars have a high probability of forming earth-like planets in the life zone.

Yes, because stars like this are in binary pairs, and the companion stars are likely places to find life-bearing planets.

No, because stars like this never live long enough on the main sequence for life to develop and evolve.

No, because this star would have expanded to envelop any planets in the life zone as it nears the end of its life.

What are the two most important abilities of a telescope?

Light gathering and optical quality.

Resolution and light gathering.

Magnification and light gathering.

Magnification and resolution.