How far is that thing?
What is 6 months?
Spiral Galaxies are often more difficult to peer through than Elliptical Galaxies due to this.
What is gas and dust in the disk of the spiral galaxy?
Hubble's Law needs to be calibrated, usually these very luminous explosions are used.
What are Type 1a Supernovae?
(will accept Supernova if no one gets Type 1a)
The habitable zone is the region around the Sun where liquid water could potentially exist. Mars, which is in the habitable zone, doesn't have liquid water on it surface for this reason.
What is it lacks an atmosphere?
This is a pretty big number:
3413456000000
and this is the same number in scientific notation and rounded to 2 significant figures.
What is 3.4 x 1012?
Determining the distance to a planet in the solar system is easy using Astronomical Units and Kepler's Third Law. But this distance distance determination method allows us to determine what an Astronomical Unit is in the first place.
What is Radar Ranging?
(Would also accept eclipses of Venus)
These kinds of galaxies appear to be made up of only old stars.
What are Elliptical Galaxies?
Measuring the Hubble's Constant is of interest to anyone that wishes to study cosmology. Typically H0 is represented with these unusual units.
What is (km/s) / Mpc?
(would accept km/(s Mpc)
Often considered to be the building blocks of life, these have been found in primordial meteorites that are left over from the solar system's formation.
What are amino acids?
The universe is expanding. In the last 30 years, thanks to long distance Type 1a supernovae observations we also know it is doing this.
What is its expansion is accelerating?
Hubble settled the Great Debate of 1920 by finding one of these in the Andromeda Galaxy.
What is a Cepheid variable star?
The Hubble Tuning Fork diagram is useful for classifying galaxies. S denotes a spiral galaxy, while SB denotes this spiral variant.
What is a Barred-Spiral Galaxy?
By inverting H0 you could measure when this happened.
What is the Big Bang?
(would also accept age of the universe, when the universe was born, etc.)
This common gas might be a life indicator when found in the atmosphere of an exoplanet.
What is Oxygen?
According to the Cosmological Principle, the universe is.
What is isotropic and homogeneous?
Useful for measuring the distance to objects on the other side of the Milky Way; Main-Sequence fitting is possible if you can determine what about a star?
What is it's temperature/color/spectral classification and that it is on the main sequence?
Making up around 95% of the matter in any galaxy, Dark Matter, is a mystery, it doesn't appear to interact with anything except through.
What is the force of gravity?
Rewinding the clock we expect the universe to have once been very dense, hot, and releasing a large amount of light. Much of that light is observable and has been given this name.
What is the Cosmic Microwave Background?
Established in 1984 SETI's main goal is to look for these.
What are signals from extraterrestrial intelligence?
The inverse square law of light allows us to know that the same star at 1 light-year away will look this many times brighter than if it was at 3 light-years away
What is 9 times brighter?
The Tully-Fisher relationship for spiral galaxies can be used to determine their distance. It requires knowing how bright a galaxy appears and this.
What is the galaxy's rotation rate?
An oddity in the universe, lenticular galaxies are what you get if you take a spiral galaxy and do this to it.
The universe seems too uniform, so much so that there needs to be an explanation. Physicists expect this period early in the universe to be the cause.
What is inflation?
It seems inevitable life should fully occupy the Milky Way given enough time, and yet (at least so far) it looks like we are alone. This line of logic is often called this.
What is the Fermi Paradox?
If we had a perfect understanding of all of the variables in the Drake Equation we would have a good estimate of this.
What is the number of civilizations in the Milky Way which can communicate with us right now?