Archive for the 'Astronomy' Category

Aug 25 2016

When Will Life Exist?

Published by under Astronomy

proximabThe Drake Equation is a thought experiment identifying which variables are needed to calculate the number of intelligent civilizations in the universe. Some people criticize the equation because we can only guess at the values of those variables, but that is not the point. The point was to identify the variables. This allows us to take the next step in the thought experiment, to plug in possible values and see what answers we get. Also, over time we will get better and better estimates of those variables.

Recently astronomers Loeb, Batista and Sloan published a paper in which they did a similar thought experiment, but instead of asking how common life and intelligent life is in the universe right now, they asked how common life is likely to be over the lifetime of the universe.

Their conclusion:

We find that unless habitability around low mass stars is suppressed, life is most likely to exist near ~ 0.1M stars ten trillion years from now.

Ten trillion years is a long time, given that the universe is only 13.82 billion years old. What they are saying is that there are many low mass stars, or red dwarfs, in the universe. Further, low mass stars have a very long lifespan, hundreds of billions and even trillions of years. About 76.45% of all the stars out there are red dwarfs, and a star with 0.1 solar masses (a tenth the mass of our sun) could survive for 10 trillion years according to our models of stellar physics.

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24 responses so far

Jul 21 2016

Dark Matter and Dark Energy

Published by under Astronomy


Genuine mysteries in science are fascinating, and there is no shortage of them. Scientists love mysteries because that is where the work is.

Two of the biggest scientific mysteries of our generation have similar names – dark matter and dark energy. Their names imply the unknown. They are, in fact, place-holder concepts that are temporarily representing what we don’t know. However, we are  slowly crawling toward an understanding of what they are.

Dark energy makes up about 70% of the mass/energy of the universe, while dark matter makes up another 25%, leaving just 5% for ordinary matter and energy. This means we currently don’t know what 95% of the universe is made of.

Fritz Zwicky first proposed the existence of dark matter in 1933, but his ideas were not accepted until the 1970s when they were revived by two astronomers, Vera S. Rubin and W. Kent Ford Jr. The hypothesis derives from the observation of how galaxies rotate. Their rate of rotation depends upon the amount of matter they contain – the more mass that exists within the orbit of any particular star, the faster that star will revolve about that galaxy. You can therefore estimate the amount of mass in a galaxy by observing how fast the stars are moving.

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31 responses so far

Apr 01 2016

Should We Hide From Aliens

Published by under Astronomy

transit-352Given the date today, I had to be careful. Is the Royal Institution investigating quantum astrology? No, but those Brits can be quite cheeky.

When I saw this headline, Lasers could ‘cloak Earth from aliens’ on the BBC website, I thought they might be having a laugh. The alternative was a bit of hyperbole in science news reporting, which is a daily occurrence. The paper on which the item is based was officially published on March 30, so I think it’s legit.

What’s going on here is that two astronomers, David M. Kipping, and Alex Teachey, did a thought experiment – what would it take to disguise the Earth from aliens using the transit method to discover the Earth? Continue Reading »

22 responses so far

Feb 02 2016

NASA – Defending Earth

Published by under Astronomy

asteroid-threat-global-action-plan-101109-02NASA recently announced that it has created a Planetary Defense Coordination Office (PDCO). The purpose of this new office is to defend the Earth from alien invasion.

OK, no, but the name does sound like that, doesn’t it?

The purpose of the office is to coordinate efforts to defend the Earth from Near Earth Objects (NEOs) – essentially comets and asteroids on a collision course with the Earth. The director is Lindley Johnson, who is currently the NEO program executive, which is an obvious fit with the new office.

NEOs do pose a threat to our civilization. You don’t have to be Bruce Willis to imagine how devastating it could be for a large rock traveling faster than a bullet to hit the Earth. Of course, the answer is that it could fall anywhere along a spectrum from nothing to wiping out our entire species. Obviously NASA is more concerned with the latter.

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11 responses so far

Oct 02 2015

The Problem of Space Junk

Published by under Astronomy

We have been putting stuff into orbit around the Earth, especially low-Earth orbit, for the last 58 years. Space is a big place, so no one probably worried at first that we would start junking it up, but that is exactly what has happened in this short span of time. This is now a serious issue we have to confront.

It’s disappointing, and I hate having one more thing to worry about, but Earth orbit has become so cluttered with debris that it poses a serious risk to our assets in space. Recently former NASA scientist Donald Kessler said in an interview:

“We’re at what we call a ‘critical density’ — where there are enough large objects in space that they will collide with one another and create small debris faster than it can be removed.”

NASA scientists also fear a scenario similar to that portrayed in the movie, Gravity. There were some scientific problems with the movie, but the core idea is valid – there is so much debris in orbit that a collision of two large objects can start a chain-reaction, they will scatter debris which will collide with other objects causing more debris.

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6 responses so far

Jul 14 2015

Why Pluto is Important

Published by under Astronomy

As I write this post we are just minutes away from the closest approach of the New Horizons probe to Pluto, the farthest world we have thus far explored (24 minutes and counting). It’s an exciting moment, not just for astronomy buffs or science enthusiasts, but for humanity. I’m glad to see an appropriate level of excitement among the media and the general public.

Still, a couple of people have commented to me or in my presence that they don’t understand what the big deal is or why this is important, so allow me a moment to explore why I think this is such a big deal.

First, let us not forget what it took to get there. New Horizons is the fastest thing humans ever built. It shot past the moon in 8 hours and 35 minutes, and made a journey of 5 billion kilometers (or 5 terameters, as my friend the Metric Maven would say). On its way it swung around Jupiter to get a gravity assist.

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40 responses so far

Apr 16 2015

Mission to Mars

Published by under Astronomy

Mars is an interesting place. The more we study the surface of the planet with our various robot labs, the more interesting it becomes. This is one of the reasons that it is very enticing to send people to Mars, but there is debate about the feasibility of any mission to Mars over the next few decades.

Life on Mars

Recently the Curiosity rover found evidence that suggests there might be briny liquid water just under the surface of Mars. When the temperature and humidity are just right, salts in the Martian soil could absorb moisture from the air creating a subsurface briny liquid water. This water would then evaporate again when temperatures rise during the day, creating a water cycle.

This would be a harsh environment for life, perhaps not compatible with life as we know it, but extremophiles have surprised us before. It is perhaps more likely that deeper down in the Martian dirt there is more permanent liquid water and more protection from cosmic rays, meaning that life could endure in slightly less extreme conditions.

There are also geological features that suggest recent flowing something, perhaps water bubbling up temporarily from below the ground, and flowing briefly before it evaporates in the thin Martian atmosphere.

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13 responses so far

Apr 02 2015

Lunar Cycle Effects Busted

When I was an intern doing a rotation in the emergency department, on one particularly busy shift a nurse commented (to no one in particular) that it must be a full moon. I habitually look at the moon and generally know what phase it is in (right now it is a waxing gibbous, almost full), and so I knew at the time that in fact there was a crescent moon in the sky. I informed her of this. She gave a disappointed look and then went on with her work without any apparent further thought on the matter.

The episode struck me at the time. It seemed to me that I just witnessed a clear example of confirmation bias – what if it had been near a full moon? That would have confirmed her prior belief in a lunar effect, while this negative correlation was brushed aside and likely did not have any negative effect on her belief. (Although, my interpretation and memory of this event can itself be an example of confirmation bias regarding confirmation bias.)

Belief in the so-called lunar effect, that the phases of the moon exert an influence on human behavior with the most common element being a full-moon inducing extreme behavior, is very common. In my experience it is one of the most common pseudoscientific beliefs I encounter in the general public. One survey indicates that 43% of adults believe in the lunar effect, especially mental health professionals, including nurses.

When someone expresses such a belief to me I often use it as an opening to discuss skeptical principles. While belief in the lunar effect is widespread, it is usually not part of any emotionally held religious or ideological belief. It is therefore an excellent teaching opportunity. One question I like to ask is, “how do you think that works?” The most common answer I receive is probably the least plausible – that the tidal effects of the moon influence the brain because the brain is sitting in water (spinal fluid).

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25 responses so far

Mar 27 2015

Dark Matter Collisions

Published by under Astronomy

The existence of dark matter is one of the coolest science stories of my lifetime. When I was growing up I was in love with pretty much every field of science, but particularly with astronomy, and at that time we had no idea that 85% of the matter in the universe even existed. We now know that the astronomy I was so fascinated with was actually the study of 15% of the matter in the universe. If you count dark energy, which makes up 68% of the universe, then dark matter makes up 27%, and everything that we thought was the entire universe is actually only 5% of the universe.

This story dramatically contradicts every crank and pseudoscientist who tries to tell you that scientists only support the status quo. In my lifetime we discovered 95% of the universe, without any prior theory telling us to expect this result. (Dark matter was hinted at in observations of galaxy rotation, but not generally accepted.) The discoveries were based on unexpected observations, that broke our models of how we thought the universe worked. Scientists met these new ideas with skepticism, but explored them further, and were slowly convinced by mounting evidence. Now dark matter and dark energy are generally accepted – because the evidence convinced the scientists. That is how science works, kids, so don’t believe the cranks.

Dark matter is a powerful idea, even though we currently don’t know what it is, because it not only explains observations that otherwise don’t make sense, it makes predictions. Predictions are the key to scientific progress. They provide the opportunity to test ideas against reality. If an idea does not make any testable predictions, right or wrong it’s just worthless. (Not even wrong.)

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18 responses so far

Mar 20 2015

Titius-Bode Law and Exoplanets

Published by under Astronomy

A recent Washington Post headline reads: Most stars in the galaxy have planets in the habitable zone, according to new research. Some version of this headline was attached to every mainstream media reporting on this story. Not just the headlines were this hyped – most of the time the reporting presented this new research as if this is an accepted conclusion.

I have been following our exoplanet explorations since they began. Like many astronomy enthusiasts, I am particular interested in a few questions – how many planets do stars have on average, what are the typical arrangements of those planets, how typical or atypical is our own system, and how many earth-like planets are out there? We are starting to get a good idea of how many exoplanets are out there – most stars likely have multiple planets.

The other questions are still open at this time. While we are gathering more and more data points, with hundreds of systems now known to have planets, and currently 1,821 confirmed exoplanets. There are a couple thousand more possible exoplanets awaiting confirmation.

This may sound like a lot, but it really isn’t nearly enough data points to answer the remaining questions above. One problem is that we don’t have a thorough survey of each system. We are finding planets that are the easiest to find – those close to their parent stars, and larger planets. Small planets far from their stars would be almost impossible to find given current methods. They would not have a significant gravitational effect on their parent star, and even if they happened to transit their star they would probably have an undetectable effect on the light from that star. Also, with periods of hundreds of years, it would take hundreds of years to confirm them by the transit method.

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12 responses so far

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