Archive for the 'Astronomy' Category

Jan 11 2018

Fast Radio Bursts – Still Not Aliens

Published by under Astronomy

This is a (sort of) follow up to my previous post. Fast Radio Bursts (FRBs) are a legitimate astronomical mystery, and very interesting. They are very brief (30 microseconds to 9 milliseconds) and very powerful bursts of radio waves. To date about 30 FRBs have been detected. Most of these FRBs are one-offs – they occur once and never repeat (at least so far). There is one exception, however, FRB 121102 (more on that below).

What do we know about FRBs so far? They are isotropic, which means they occur all over the sky. They are not concentrated in the galactic disk. This by itself implies they are extragalactic. But also analysis of the radio bursts indicate that they have traveled through intergalactic plasma, for billions of light years. So they must also be incredibly powerful. The radio waves are broadband, so they are spread throughout the radio wavelengths. They are also highly polarized, which means they were aligned at their creation with a strong magnetic field.

Because they are radio bursts, they are studied by radio astronomers, which includes SETI astronomers, whose primary mission is to survey the sky for possible alien communications. In an SGU interview with SETI astronomer Seth Shostak he indicated that SETI does a lot of non-ET-related astronomy. This is a good example of that – they are helping to detect and analyze FRBs, including analysis of FRB 121102.

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Jan 09 2018

Tabby’s Star Mystery Partly Solved

Published by under Astronomy

It’s not aliens.

So far, no astronomical mystery has turned out to be aliens, although this hypothesis seems to come up every time. The first detections of signals from pulsars were named LGMs for “little green men.”

I’m not really criticizing this – part of me wishes the mystery will turn out to be evidence of an alien technological civilization. I always think of how plausible that is for an explanation. But still it should be last on the list. Chances are overwhelming that we are just seeing some new or unusual natural phenomenon. It’s a big complex universe out there.

In this case astronomers found a genuine mystery – a star that dimmed and brightened over time to a degree never seen before. The star has the designation KIC 8462852, and has been nicknamed “Tabby’s Star” after the astronomer who first described it, Tabetha Boyajian (she actually led a team of 200 astronomers involved in the work).

The intensity of the light coming from the star, which is a little bigger and 4.7 times brighter than our sun and is about 1300 light years away, dims at irregular intervals by as much as 22%. This could not be caused by a planet passing in between us – even a Jupiter-sized planet would only block about 1% of the light from the star. And what’s with the irregular period? Dimming from an object in orbit should be very regular.

The best hypothesis was that a swarm or cloud of something was blocking the light. It would have to be a big and dense cloud, however. This hypothesis had problems also, however, because such a cloud should be heated up and glowing in the infrared, but we don’t see it.

The “swarm” idea sparked the notion of a Dyson swarm, which is a hypothesized high-tech structure surrounding a star used to capture the light for energy. An advanced civilization, for example, could power themselves with either a large single structure of solar cells, or a swarm of smaller ones.

No scientists really took the alien megastructure hypothesis seriously, even though it could not be entirely ruled out. It was just way too early to get excited, and it was overwhelmingly likely that a natural explanation was to be found. But scientists love a mystery in any case, and whatever was going on around Tabby’s star was likely to be new and interesting.

What astronomers needed was a lot more data. So Boyajian and others started a kickstarter campaign to fund the telescope time they would need to gather that data. The campaign was successful, exceeding their needed $100,000. Last week they published the result of their analysis and…no aliens.

What they did was look at the different wavelengths of light to see how they were dimmed. If the swarm that is causing the dimming is comprised of solid objects, whether rocks, planetary debris, comets, or solar panels, then all wavelengths should be dimmed equally. That’s not what they found. They found that different wavelengths were dimmed to different degrees at different times.

That is what you would expect to find if the cloud (circumstellar material) blocking the light were comprised of very tiny particles (smaller than a micron), like dust. So that is what they concluded – there is a dense dust cloud around Tabby’s star blocking the light from our perspective. This also makes sense in terms of the variable periods, because different densities in the cloud could cause random fluctuations in the amount of light blocked.

But of course now astronomers just have a new mystery – what caused this massive fine dust cloud around Tabby’s star? Comets are very dusty, and a dust cloud like this could result from a comet – but it’s a lot of dust. It’s also probably close to the star, which means it is also probably a recent phenomenon as a dust cloud would likely not survive long that close to a star that bright. This also still doesn’t explain the lack of an infrared glow from the cloud.

The results also don’t rule out that the star is dimming and brightening on its own, and not just being blocked from view. And of course, some hopefuls have pointed out that it could be a swarm of alien nanobots or similar microscopic technology. Sure.

There is still more science to be done here, but this latest result does add a significant piece to the puzzle. It’s also cool that the research was crowd-funded. That’s a great way to get private citizens involved in science, and to fund more science. That may, in fact, be the bigger story here. Yeah for crowdfunding cool science.

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Dec 15 2017

Saturn’s Rings Are Younger Than Previously Thought

Published by under Astronomy

The gorgeous rings of Saturn are one of the most dramatic features of our solar system, and certainly a favorite of any backyard astronomer. Are they, however, a fixture that have been present for the majority of the life of our solar system, or are they a recent addition?

Of course we have no observations from millions or billions of years ago, so we can only infer their probable age. Up until recently astronomers believed they were probably ancient because the large collisions that likely produced them would have been far more likely in the early crowded solar system. However – recent evidence from Cassini has changed that conclusion.

The Cassini probe made detailed observations of Saturn and its rings for years, until it plummeted into the planet this September. Scientists are still analyzing all the data it sent back home. Two lines of evidence suggest that the rings of Saturn are far younger than previously suspected.

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Oct 20 2017

Making Oxygen on Mars

Published by under Astronomy,Technology

Mars baseAt some point humans will travel to Mars. It seems inevitable, the only question being when that will happen. Optimists like Musk think it will happen before mid-century, but that may not be realistic. There are significant logistical hurdles without clear solutions.

Some argue, and I agree with this strategy, that we should focus first on a moon base. The moon is a lot closer, which solves many problems right there. But otherwise it would have many of the same challenges as Mars, and so if we develop a base on the moon we can use what we learn to be better able to tackle Mars. Further the moon can be a literal launching pad for Mars.

While Mars has some extra challenges, it may have some advantages as well over the moon. NASA experts have observed that Mars has just enough of an atmosphere to be a problem. It has 1% of the pressure of Earth, which means for astronauts it is functionally the same as a hard vacuum. You still need pressure suits, pressurized living spaces, and you need a supply of air to breath.

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Oct 19 2017

More Gravitational Waves

Published by under Astronomy

neutronStar_drupal_withNOcaptionThe winner of the Nobel prize for physics was the detection of gravitational waves. These are extremely subtle ripples in spacetime caused by massive cataclysmic events, such as black holes colliding. These ripples were predicted by Einstein, who thought we may never be able to detect them because they would be so unbelievably tiny.

How tiny?  LIGO (Laser Interferometer Gravitational-Wave Observatory), the device used to detect the waves, can detect changes as small at 10 -22 meters. Graviational waves detected so far have had an amplitude of 10 -18 meters, smaller than the radius of a proton.

How is that possible? That is where the interferometry comes in. LIGO uses a laser split into two beams that will travel for 8 Km and then reflect off mirrors and come back to the same detector. The two beams have traveled the exact same distance so that they are in phase, or at least they can be calibrated to be exactly in phase, meaning that the peaks of the waves line up. When a ripple in spacetime comes through, the length of the two arms (which are at 90 degree angles to each other) will change slightly, bringing the two beams out of phase. That slight phase shift can be detected and measured.

Prior to winning the Nobel prize LIGO had detected four gravitational waves wash over it. This was considered enough of a confirmation of the technology and science to award the prize.

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Oct 10 2017

Half the Matter in the Universe Just Found

Published by under Astronomy

filamentsBy now most people are familiar with dark matter – that mysterious substance which has gravity but otherwise does not seem to interact with the normal matter with which we are most familiar. About 27% of the stuff (matter and energy) in the known universe is dark matter, 68% is dark energy, and only about 5% is made of known particles (baryons – protons, neutrons; leptons – electron; and more exotic particles).

We currently don’t know what dark matter is. We know it’s there because we can see its gravitational effect, first noticed because galaxies spin faster than they should. Based just on the gravity from stuff we can see, galaxies should be flying apart. They stick together because there is significantly more gravity than we can account for. There must be additional matter we can’t see, or dark matter.

It is perhaps less well-known that we also haven’t found about half of the normal matter that should exist in the universe. Even if we just consider that 5% that is made of standard particles, about half of it is missing. That is – until now, if recent reports are accurate.

This really wasn’t much of a mystery (not like dark matter) – astronomers suspected that the missing matter was present in the form of diffuse gas between galaxies. There is a lot of space out there, and even a wispy vapor could contain a lot of particles, as much as is contained in all the visible galaxies. The problem is, this thin gas is too wispy to see with conventional means.

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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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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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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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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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