Archive for the 'Astronomy' Category

Sep 15 2017

Cassini’s Dramatic End

Published by under Astronomy

Saturn- CassiniThe Cassini probe to Saturn has been considered one of the most successful space missions in history. Today it will plunge into the upper atmosphere of Saturn. As the atmosphere gets thicker on its way down the probe will begin to tumble from the turbulence, until it is ripped apart by the violent forces and finally melts in the intense heat of the gas giant. (As I am writing this there are just 30 minutes left.)

This is the intended fate of the probe. It was launched in 1997, took seven years to get to Saturn, and has been studying the planet and its moons for 13 years. It has dramatically improved our knowledge of the Saturn system. Cassini was the first probe to orbit Saturn. Prior to that, Pioneer and Voyager had performed flybys, which gave us quick glimpses but did not allow for extended study.

In addition to being a feat of science and engineering, Cassini surpassed expectations. Its original mission profile was for four years. It was able to have two mission extensions, for a total of 13 years. Now it is almost completely out of fuel – its mission is over.

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8 responses so far

Aug 29 2017

40 Years of Voyager

Published by under Astronomy

voyager1_highOn August 20th 1977 Voyager 2 was launched. On September 5th Voyager 1 followed. The reason 2 launched before 1 is because V1 was on a faster trajectory and would arrive at Jupiter several months before V2, and NASA felt it would be easier not to have to explain endlessly to the media why V2 was arriving before V1. At present V1 is 12,959,246,289 miles from Earth, and V2 is 10,657,559,202 miles.

Voyager 1 is the farthest human made object from the Earth. If our civilization collapses tomorrow, the Voyager probes would be the longest surviving artifacts of our existence.

If you do not remember the Voyager missions, then think of what it was like for Horizon to fly by Pluto. Pluto went from a fuzzy blob to a detailed alien world. The Voyager missions were the same, except times four. This was our first closeup look at Jupiter, Saturn, Uranus and Neptune. It was our first closeup look at the large moons of Jupiter – Io, Ganymede, Europa and Callisto. We discovered even more smaller moons of Jupiter and Saturn. We discovered volcanic activity on Io, and that Jupiter has rings of its own.

Our knowledge of the outer solar system exploded, and we were rewarded with seemingly endless gorgeous pictures of these giant worlds and their companions.

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13 responses so far

Aug 21 2017

Solar Eclipse and Coincidence

solar-eclipse-2017Today there will be a total solar eclipse making its way all across the continental US, from Oregon to South Carolina. Unfortunately I could not logistically travel to see it first hand. I’ll have to wait for 2024, when another total solar eclipse will hit America, making a trail from Texas through upstate New York. Here in CT we will get 75% coverage, which will be cool but nothing (from what I hear) like seeing totality.

Eclipses are one of the testaments to the power of science. We can predict them with incredible accuracy, because we have worked out in tiny detail how planetary orbits work. We can make careful observation and combine that with accurate theories about how the universe works and mathematics to make calculations, and predict these celestial events far into the future.

Some people, however, choose to see the eclipse as a testament to the existence of God. I first heard this argument when I was in college – a friend of mine who was also a fundamentalist Christian essentially ridiculed me for thinking that eclipses were just coincidence. The hand of God was clearly at work.

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35 responses so far

Mar 10 2017

Fast Radio Bursts and Alien Life

Published by under Astronomy

frb-alienFast radio bursts (FRBs) are brief, bright, and distant bursts of radio emissions that are of unknown origin. Recently they have been in the news because of a paper which explores the feasibility that FRBs have an alien origin.

“Fast radio bursts are exceedingly bright given their short duration and origin at great distances, and we haven’t identified a possible natural source with any confidence,” said theorist Avi Loeb of the Harvard-Smithsonian Center for Astrophysics. “An artificial origin is worth contemplating and checking.”

Let me first give a little more background on FRBs and then we can discuss the alien hypothesis.

Fast Radio Bursts

The first thing to know about FRBs is that they are, indeed, fast. They typically last only a few milliseconds (thousandths of a second). Recorded FRBs range from 0.05 ms to 9.4 ms. That is extremely brief.

They are broadband radio bursts, meaning that they cover a broad frequency range.

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Mar 06 2017

Terraforming Mars

Published by under Astronomy

MarsTransitionVHow high a priority should we have for sending people to Mars? This seems to be a big question these days. NASA is developing the Space Launch System (SLS) and the Orion capsule specifically to have the capacity to send people to Mars. Elon Musk has stated that the real purpose of SpaceX is to colonize Mars.

The public imagination has also been sparked by movies such as The Martian (which was excellent). I also recommend National Geographics’ series “Mars” which is a combination of interviews with current scientists and engineers about the problems that a Mars colony would face, with a narrative about a future colonization mission.

The one fact that everyone agrees on is that colonizing Mars will be extremely difficult. Mars has an atmosphere about 1% that of Earth. This makes it just thick enough to be a problem but not thick enough to help with breaking while landing on Mars, and not thick enough to make the surface any more livable. A 1% atmosphere is effectively a vacuum, but it is enough to cause planet-wide dust storms that would make life on Mars challenging.

Transfer to Mars would take about 8 months with current rocket technology. Depending on the relative position of the planets and the transfer speed, 130-260 days are the figures most often cited. That means supply lines would be very difficult, and don’t expect any rescue missions.

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12 responses so far

Jan 27 2017

Scientists Create Metallic Hydrogen

jupiter-magnetic-fieldIt was just announced that for the first time scientists were able to create a small amount of metallic hydrogen in the lab. This is a significant breakthrough, and is sure to lead to further discovery, although it remains to be seen what specific practical applications may emerge.

Hydrogen, as most people know, is a gas at familiar temperatures and pressures. The universe is comprised of about 90% hydrogen. There is very little free hydrogen on the Earth, since it is a very light gas, but there is lots of hydrogen bound up in molecules, such as water.

In 1935, physicists Eugene Wigner and Hillard Bell Huntington hypothesized that under extreme pressure hydrogen atoms may form into a metal – metallic hydrogen. The point at which this happens was named the Wigner-Huntington transition, which explains the title of the recent paper. Metallic hydrogen can further be a liquid, in which the electrons and protons are free flowing, or they can form a crystalline structure and be a solid.

Astronomers infer that the core of Jupiter may be hot liquid hydrogen. We know that Jupiter is made mostly of hydrogen, and we can calculate that the pressure deep in Jupiter’s core must have millions of times the pressure on the surface of the Earth. That is sufficient pressure, according to theory, to compress hydrogen into its metallic form.

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19 responses so far

Oct 25 2016

234 Possible Alien Signals

Published by under Astronomy,Skepticism

alien-worldI love reading articles that discuss the same issue and come to essentially opposite conclusions. In this case, Canadian astronomers have recently performed an analysis of 2.5 million stars and found 234 of them producing pulsed signals that they claim may be of alien origin. The scientific community is skeptical.

The Independent declares, “Strange messages coming from the stars are ‘probably’ from aliens, scientists say.” Meanwhile, states, “Why hundreds of aliens probably aren’t trying to contact us.”

When you read deep into both articles you find a more nuanced position. The difference is mostly in the headline writing, but also in the overall emphasis of the article. Skepticism can be marginalized or central.

SETI and Skepticism

I have found the search for extraterrestrial intelligence (SETI) to be an excellent topic of skeptical discussion. It is a great forum for discussing what is legitimate science, and how scientists decide whether something is likely to be true or not. There is nothing supernatural or paranormal about life evolving on exoplanets, intelligence emerging, and developing a technological civilization that might send signals out into space. We have done it.

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71 responses so far

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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32 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

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