Mark asks,

Dear Astronomer,
Is the amount of matter in the Universe finite or infinite, and why do you think so?

Mark,

I’ll be the first to admit I’m more of an observational astronomer, and not much of a cosmologist or theoretical physicist.

That being said, the answer to your question varies depending on how you look at it. As far as matter you can see, touch, taste, or smell, there is a finite amount of it.

Since we can measure (roughly) the matter in the observable universe, and we know the universe is expanding, we’re actually in an exciting time where the density of matter in the universe is at a balance point.

However….. if you peer deep into the subatomic and “quantum” level – it could be said that there is an infinite amount of matter that pops into and out of existence. Since cosmology and theoretical physics are a bit out of my field, I’ll let ASU professor Lawrence Krauss help explain:

Alex asks:

Dear Astronomer, What are the average high and low temperatures of the planets in our solar
system?

Great question Alex!

Given the different distances and compositions of objects in our Solar System, there is a wide range of temperatures. What is very interesting about the range of temperatures is how a planet’s atmosphere (or lack of) can affect it’s temperature, along with the surface composition.

Keep reading for a full list of high and low temperatures across our Solar System, along with what factors can affect said temperatures.

Continue reading →

Jennifer asks:

“Dear Astronomer,
What type of water is in space? Is it fresh water or salt water?”

Jennifer,
You’ve asked a very interesting question, one I’m happy to answer!

With Hydrogen and Helium being the two most abundant elements in our Universe, it’s no surprise that many gas-filled regions of interstellar space are for the most part, Hydrogen. If a cloud of dust and gas is cool enough to form molecules, we refer to it as a Molecular Cloud. Molecular Clouds are often “enriched” by neighboring supernova explosions which add elements heavier than Hydrogen and Helium to the mix.

Astronomers actually study molecular clouds by looking for the chemical signature of Carbon Monoxide ( CO ) since molecular Hydrogen ( H₂ ) is difficult to detect with radio and infra-red telescopes.

Of course, H₂ and CO aren’t the only molecules found in Molecular Clouds. With Oxygen being the third most common element in our galaxy after Hydrogen and Helium, the chances of H₂ combining with Oxygen to form water ( H₂O ) are pretty reasonable.

Continue reading →

A while back one of my plusketeers (Google+ follower) asked this question:

Do the parameters for the habitable zone change if we consider moons of gas giants?

I’ve been wondering about this (especially with all of the Kepler news the past couple of months), but can’t figure out how to search the all-knowing Google for an answer.

(related, the Drake Equation doesn’t seem to take habitable moons into account – should it?)

Many thanks!

This is actually a very interesting question, especially with the fact that I’m working VERY hard to specialize in Exoplanetary Science.

If you aren’t familiar with the Drake Equation, or how it may actually apply to exomoons, continue reading to learn more about the famous equation.

Additionally, I’ll discuss what conditions could make a habitable moon like “Pandora” as depicted in the blockbuster movie, Avatar, or the forest Moon of Endor as seen in Return of the Jedi
Continue reading →

Markus asks:

“Dear Astronomer, Imagine you are inside the space station, with all fans and air circulation turned off.
The air inside is completely still. You decide to light a cigarette.

How would the smoke from the burning cigarette form? Would it be a perfect sphere?
Would the smoke around the cigarette kill off the oxygen supply and put the cigarette out,
or would the cigarette slowly float away like a small mini rocket?

Interesting question Markus!

NASA actually has been performing experiments on the International Space Station to learn more about how fire behaves in zero-g.

Read more to learn about what the NASA studies have revealed.
Continue reading →

Doug asks,

Dear Astronomer,
What is the size and brightness of the Sun as viewed from the different planets in the Solar System?

Excellent question, Doug!

As the distance increases between a planet and our Sun, not only do planets receive less energy, but the apparent size deceases.

Standing on the surface of Mercury would yield an impressive sight, while standing on Eris, the sun would be much fainter.

Keep reading for a detailed comparison of the Sun’s apparent size through the Solar System.

Continue reading →