Six common questions to ask an Astronomer

Six questions that drive us nuts because we are asked these constantly. So here's our different takes on the possible answers.

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At Milky-Way.kiwi we had a think about the six most commonly asked questions that we have heard over the years doing a variety of astronomy outreach activities. These have been generally from people with limited knowledge of space so the questions are usually quite broad and can be answered in an almost infinite number of ways. We thought it would be helpful to build an understand of the common questions and see how we would answer them.

What do you see when you look at the stars?

Hari: “I’ve seen things you people wouldn’t believe…, attack ships on fire off the shoulder of Orion. I watched C-beams glitter in the dark near the Tannhauser Gate…” goes the line from Blade Runner, one of my favourite movies ever. Now seriously, I see things you people wouldn’t believe, the rings of Saturn for instance is one that never gets old. And everyone whose ever seen them for the first time through the telescope on my watch almost jumped out of the seat when realising they are just like in the pictures.

Sam: When I get asked this question, I invariably say that what I see when I look at the night sky is history happening right in front of our eyes. I say to people that when they see the stars they are looking back, potentially, many thousands of years. Some of the stars they are seeing don’t exist anymore, many of them would no longer be in the positions they appear when they see them. Even the closest visible star to us is still 4.3 light years away, which is a huge distance. At the other end of the scale the Large Magellanic Cloud (LMC) is 160,000 light years away. The entire existence of modern humans has occurred in the time it took the light to leave the LMC and arrive in our eyes, I think that is amazing. Visually near to the Small Magellanic Cloud (SMC) is the globular cluster 47 Tucanae (the picture below was taken by the Hubble Space Telescope) which is visible to the naked eye as a fuzzy looking star. The light from this fuzzy looking star set out on its journey to us at the end of the last ice age, before humans had figured out agriculture about 15,000 years ago. For those in the Northern Hemisphere the most distant sight available to the naked eye is Andromeda Galaxy at more than 2.5 million light years away, sure its hard to see, as it’s a faint smudge and you need a very dark sky but it’s staggering to think that you’re looking back in time 2.5 million years.

47 Tuc, NASA

How do black holes work?

Hari: you might run the risk to get turned into spaghetti if you get into one (really, the process in which one is stretched by the black hole is called spaghettification.)

Sam: I think that black holes are one of the most amazing and frightening objects in the universe. They are so dense and have such a strong gravitational pull that light cannot escape, hence we can’t see them. They are born at the end of a star’s life and that remnant of the star needs to have a mass 3 to 4 times the current mass of the Sun. At that size the gravitational pressure can’t be stopped by the nucleus of the atoms making up the remnant star so it keeps collapsing further and further until it is so dense that it is does some very weird things to the fabric of space time. If you approach a black hole you would speed up faster and faster as you got closer and closer to the event horizon, you would be getting closer and closer to the speed of light, if you were going feet first then your feet would be travelling slightly faster than you head so you would effectively be stretched. At the point of the event horizon you would be at the speed of light. For you, time would stop as you are going at the speed of light and that’s where you would stay, it would seem that you were forever getting closer and closer to the event horizon but never actually get there. For someone watching you they would see you get further and further away until you disappear, roughly. Black holes grow by absorbing the surrounding gases and material and can sometimes even tear stars apart that get caught too close. In the early universe huge stars formed and very quickly went through their lives destroying themselves and forming massive back holes that collided with others and formed the supermassive black holes that are present at the centre of many galaxies.

Do you believe in aliens?

Hari: Well, how shall I put this, I was the one who answered the phone on behalf of the Royal Astronomical Society of New Zealand (read publicity officer) and people did call to report a seeing of a UFO. To be fair, when I was a kid I read everything that I could lay my hands on about “aliens”. Conspiracy theories, ancient astronomy, the stone of Baalbek, strange lights in the sky, you name it. I was like a sponge. Then the older I got the more I got into science and started finding scientific explanations for everything. Now my standard answer is “it’s planet Venus”. And I mean it. I’ve also visited SETI a few times, the featured picture was taken by me there in October 2013, it’s an autographed framed photo of Jodie Foster on a random shelf with the famous Drake equation. And Seth Shostak, the most famous alien hunter there is, came here in June 2018 to talk about aliens at the Astrobiology Australasia Meeting in Rotorua, New Zealand, which we organised.

Sam: In 1961, Frank Drake from the National Radio Astronomy Observatory (NRAO) came up with an equation that tried to encapsulate all of the variables that would ultimately give a number of how many civilisation could be in our galaxy. At the time they ran figures through the equation and came up with a figure of 10 for the number of civilisations that could have evolved and able to conduct interstellar communications at any given time. Given the massive size of the galaxy, if the ten were evenly spread then they would tens of thousands of light years apart so the chances of detecting their existence while they existed would be even more remote, let alone making contact. The Drake equation is a fascinating attempt at giving structure to a difficult question that we are learning more and more about all the time. For example we know a lot more about the probability of the formation of planets than we have done in the past.

N = R x fp x ne x fl x fi x fc x L

N = The number of broadcasting civilizations.
R = Average rate of formation of suitable stars (stars/year) in the Milky Way galaxy
fp = Fraction of stars that form planets
ne = Average number of habitable planets per star
fl = Fraction of habitable planets (ne) where life emerges
fi = Fraction of habitable planets with life where intelligent evolves
fc = Fraction of planets with intelligent life capable of interstellar communication
L = Years a civilization remains detectable

So yes I believe that there is the possibility of an alien civilisation existing in the galaxy at the same time as us. I think it is incredibly unlikely we’d meet though.

Do you think there is life outside of Earth?

Hari: oh, I hope so!

Sam: There is almost certainly life outside of the Earth. With the number of planets identified that could contain liquid water growing all the time we are getting a better understanding on the chances of having all of the right ingredients together to spark single cell life. It’s important to remember that the Earth was around for 3 billion years with just single cell life forms before a few cells stuck together to start the multi-cell evolution that led to us. That 3 billion years was on a very stable planet, in a stable orbit, whizzing around a very stable star and even then there were a few extinction events that nearly ended it all. So yes, there is almost certainly single cell life out there somewhere.

Oh, so you’re an astrologer?

Hari: For the first hundred times I tried to be nice and explain the difference between astrology and astronomy by explaining that astrology is the grandmother of astronomy, it was probably used initially more like a calendar that would tell the position of the Sun in a certain day on the zodiacal belt. This belt is important because it is in the only part of the sky that visibly appears to shift during the twelve months of the year. For example the open cluster of stars, M45, the Pleiades, is also on the zodiacal belt. Many cultures used it to mark the New Year, because once a year it will appear in the same place at the same time such as at Halloween where it will be visible on the horizon just after sunset in November. The zodiacal belt is also the place where we can see the planets as this is the only place that we can observe the planets, they aren’t in any other part of the sky. Those characteristics made it fascinating to early observers of the night sky who, not knowing what was going on, sought explanation for events happening around them. We are very good at recognising patterns, in fact so good, we see patterns when there aren’t any. Our brains will take in any information over no information. With the advance of science and observations of the planets we soon realised what the planets really were. This was when astronomy split from astrology and ever since, astronomy, has relied on scientific method as it’s basis. As for astrology, it still exists as people continue to seek explanations for things in their lives they can’t explain. There is very little astronomy in astrology, for example most astrologists do not take into account precession.

Sam: I think you have the wrong place, there’s a bus leaving soon, it’s safe to wait on the street.

What telescope should I buy for my family member?

Hari: a solar one? Coz astronomy can happen during daytime too, you know.

Sam: There are so many different variables with this question, have a look at this article as we try to cover aspects of this question.