February 8 – Big Smalls

Today’s factismal: Most stars aren’t visible because they are too small and too cool.

If you go out at night and look up in the sky, you will probably see lots of stars out there. Though a couple of them are bright enough to look like they have color (e.g., Betelgeuse, Aldebaran) most of them just look like little white dots in the black velvet of night. But what you may not realize is that you are just seeing part of the picture. That’s because when you look at the night sky you can only see those stars that are big enough and bright enough to be seen – and they are just a small fraction of the stars out there!

Most stars are much smaller than the Sun (a.k.a., "Sol").

Most stars are much smaller than the Sun (a.k.a., “Sol”).

How small? Well, astronomers aren’t certain but they agree that at least 70% of all stars out there are “dwarf stars” with less than half the mass of the Sun (known as “Sol” in astronomy circles); some think that it may be as much as 85%! These stars range in size from about ten to five hundred times the mass of Jupiter (to an astronomer “size” always means “mass”). Because they are so small, they burn hydrogen very slowly. Eventually, they will run out of hydrogen and turn into white dwarfs, in a mere 500 billion years or so. In the meantime, these small stars, like Epsilon Indi BB, give off very little visible light and most of their “shining” is done in the infrared (“heat”) portion of the spectrum.

The hotter something is, the "blue-er" its color is. This is true of stars as well as planets.

The hotter something is, the “blue-er” its color is. This is true of stars as well as planets.

The rare big stars, like VY Canis Majoris, have a lot of fuel but they burn through it fast becoming super-hot and glowing a bright blue that slowly changes to red as they lose mass and cool off slightly. (And I do mean “slightly”; at its start, a hypergiant like VY Canis Majoris burns about 500,000 times as brightly as the Sun but it gradually drops to a mere 200,000 times before exploding into a nova.)

Bigger stars are much more massive and much hotter; that makes them brighter and bluer than small stars

Bigger stars are much more massive and much hotter; that makes them brighter and bluer than small stars

So there are a lot of small and dim stars that aren’t visible to the naked eye; they are the candle to the rare big star’s searchlight. But the thing is that there are a lot more candles than there are searchlights. For every star you see at night, there are at least 100 more that are too small to be seen.

A look at the Milky Way using ultraviolet and infrared light (Image courtesy NASA)

A look at the Milky Way using ultraviolet and infrared light
(Image courtesy NRAO)

Big big or small, astronomers study them all. And here’s an image of what those stars look like when we peek at them using ultraviolet and infrared light. “Ordinary” stars that we can see at night glow a greenish white, where newborn and small stars heat up the surrounding dust and make it glow a bright violet for infrared and a startling purple for radio waves. If you’d like to see more pictures like this, and maybe help find hot stars in other galaxies, then point your scope to:
https://www.zooniverse.org/projects/bridgetk/hubbles-hot-stars

February 6 – The Sky’s A Rockin’!

Today’s factismal: Nearly 42,000 meteorites hit the Earth every year.

Odds are, you’ve seen the really cool dashboard video of the meteor that light up the sky in Illinois and Wisconsin last night. Right now, we don’t know much about this particular meteor other than it was big and bright. We don’t know if it landed somewhere on Earth like the 42,000 other meteorites than come to ground each year or if it headed back out into space like the The Great Daylight Fireball of 1972. We’re not even sure where it came from – was it a piece of a comet or a chunk of an asteroid?

The Great Daylight Fireball of 1972 (Image courtesy and copyright James M. Baker)

The Great Daylight Fireball of 1972 (Image courtesy and copyright James M. Baker)

What we do know is that there will be nearly 70 different chunks of rock and ice that speed by the Earth in February alone! They’ll zoom past at distances ranging from just outside the atmosphere to 78 times the distance to the Moon. They range in size from the size of a tiny house (about 36 ft) to the size of a tiny village (about a mile across). These rocks are made up of chunks of comets and asteroids and even bits of Mars and the Moon that have been blasted into space by impacts from other chunks of rock!

A meteor streak across the Milky Way (My camera)

A meteor streak across the Milky Way
(My camera)

What is important about these chunks of rock is that they tell us how dynamic our Solar System is. Instead of being a dead old system with an orbit for everything and everything in its orbit, the Solar System is a dynamic, ever-changing system with the planets and comets and asteroids interacting to change orbits and thrown new stuff in new places. And they can provide us with samples from other planets and from the earliest formation of the system. Besides which, they are just plain pretty!

A meteorite as seen from above the atmosphere  (Image courtesy NASA/Ron Garan)

A meteorite as seen from above the atmosphere
(Image courtesy NASA/Ron Garan)

But the best thing about meteor is that you can help scientists learn more about them! If you download NASA’s Meteor Counter App (available for iPad, iPhone, and iWannaMeteor), then you’ll be able to send NASA scientists valuable information on the number of meteors that hit during the shower. They’ll then use that information to help us understand how likely it is that we’ll get hit. To learn more, go to NASA’s web site:
http://science.nasa.gov/science-news/science-at-nasa/2011/13dec_meteorcounter/

January 25 – Hot Topic, Cool Science

Factismal: IRAS was launched on January 25, 1983.

Astronomy entered a new age in 1983, with the launch of the Infrared Astronomy Satellite, or IRAS for short. IRAS wasn’t the first telescope into space, nor was it the first infrared telescope. But it was the first infrared telescope in space. And that is what matters, because it turns out that space is the place to be if you want to see something that is invisible.

The InfraRed Astronomical Satellite (IRAS) discovered the first exoplanet (Image courtesy NASA)

The InfraRed Astronomical Satellite (IRAS) discovered the first exoplanet (Image courtesy NASA)

You see, the part of the spectrum that we see is just a very, very limited part of a much wider whole. The visible spectrum, which covers the colors from blue through red, says a lot about the world. But the invisible spectrum, which covers colors that are cooler than red (the infrared) and hotter than blue (the ultraviolet), tells us a lot more about the universe. Part of that is simply because most of the universe is very, very cool. And the rest is because the parts that aren’t cool can be very hot indeed.

The hotter something is, the

The hotter something is, the “blue-er” its color is

And it turns out that the temperature is the key to the color. Back in 1900, Planck was able to show that the color of an object was intrinsically related to its color. For example, the Sun is yellow because the part of it that we see is about 5000 K (about 8540 F, or “really, really hot”). We now use that principle in a number of ways, from taking the temperature of a star to taking the temperature of a baby.

But not all colors of light make it through to the ground. To understand this, think of a brick wall. You cannot see through a brick wall because the bricks block the visible light while allowing more energetic gamma rays to pass through. Similarly, our atmosphere blocks a substantial part of the infrared light while letting the more energetic visible light through. And, just as you can see what’s on the other side of a brick wall by walking around it, telescopes can see the infrared colors blocked out by our atmosphere by going above it.

And when they did, what an amazing array of interesting things they saw. While looking at over 500,000 light sources, IRAS discovered the source of the Geminid meteor shower. IRAS discovered six new comets. IRAS saw the dust created by asteroid collisions as a giant cloud surrounding the Solar System. And IRAS saw 75,000 different galaxies with huge numbers of new stars being born. Most importantly, IRAS gave us the first picture of planets forming from a cosmic cloud of dust and gas.

And the hits from IRAS keep coming, even though the satellite quit working nearly thirty years ago. That’s because there are lots and lots of images from IRAS and other space telescopes that need people to look through them. People just like you! If you’d like to try your hand at classifying infrared images, then try the Milk Way Project:
http://www.milkywayproject.org/

January 16 – Blowin’ In The (Cosmic) Wind

Today’s Factismal: The Stardust mission returned samples from a comet ten years ago today but the science continues!

There are a lot of things we don’t know in science. But there are a lot of things that we know, too. For example, we know that everything in the Solar System, from the Sun to the Earth to the smallest asteroid, all formed from the same cloud of interstellar dust and gas that collapsed some 4.5 billion years ago. But the Sun is very different from the Earth, which is very different from a comet or an asteroid. So while we know where we came from (as one astronomer used to say “We are all stardust”), how we got here is still something of a mystery. Though we have samples of the rocks on Earth, the Moon, Mars, and several asteroids, all of those have been changed by different geologic processes over the past 4.5 billion years. What we really need to understand how our Solar System formed is a sample of the original material.

The Stardust probe (NASA illustration)

The Stardust probe
(NASA illustration)

And that’s why the NASA Stardust mission happened. In 1999, NASA launched a space probe that was designed to do something that had never been done before: to go to a comet, grab samples of the dust, and return it safely to Earth. The probe looked a little like a five and a half foot long shoe box with a surfboard on either side; the two surfboards were solar panels that supplied the energy to run the instruments. Like other space probes, Stardust included a mass spectrometer to identify the composition of dust and gases it encountered and a camera to provide images. But Stardust’s heart (which was located on the front of the probe) was the sample collector.

Comet dust captured by Stardust (Image courtesy NASA)

Comet dust captured by Stardust
(Image courtesy NASA)

In order to collect samples of comet dust without damaging it or heating it up, NASA used aerogel, a material that is 99.8% empty space. Though aerogel had been invented as a bar bet in 1931, it hadn’t found a practical use until the Stardust mission (since NASA popularized the material, it has become very common in some industrial applications). Because aerogel is so light, it would stop the dust grains gradually with a minimum of breakage. And because aerogel is translucent, the tracks made by dust grains could easily be spotted by scientists.

The Wild 2 comet, as seen by Stardust (Image courtesy NASA)

The Wild 2 comet, as seen by Stardust
(Image courtesy NASA)

Both aerogel and the mission were an unqualified success. Stardust visited the asteroid 5535 Annefrank and discovered that it is larger and more interesting than previously thought. Stardust successfully captured dust both from between the planets and from comet Wild 2 and discovered that comets may not be as pure as we thought. And Stardust took the names of more than a million people (including me!) out between the planets.

During it's twelve year mission, Stardust visited an asteroid and two comets (Image courtesy NASA)

During it’s twelve year mission, Stardust visited an asteroid and two comets
(Image courtesy NASA)

Today, the samples from that mission are being analyzed by people just like you. If you’d like to take a stab at identifying dust grains and helping discover how our Solar System started, then fly on over to:
http://stardustathome.ssl.berkeley.edu/

December 21 – Running, Jumping, Standing Still

Today’s factismal:  Today is the first day of winter – but only if you are an astronomer.

Today is one of the more interesting days in the year. It is the day in which the Sun stops its apparent southward movement through the sky and starts to move northward once more. On this day, the Sun appears to stand still (at least as far as the North/South question is concerned), hence the name “solstice” (Latin for “Sun stand”). Today, astronomers use the change in the Sun’s apparent movement to declare the start of “astronomical winter”. But 10,000 years ago, people used it to mark the middle of winter. So today is both the start and the middle of winter!

The analemma tracked out by the Sun over the year (Image courtesy the Analemma)

The analemma tracked out by the Sun over the year
(Image courtesy the Analemma)

So how did people track the Sun 10,000 years ago? The same way that we do today; they plotted the position of the Sun at noon using a stick and pebbles (teachers: this makes a great class science project!). The pebbles created a figure-eight pattern that the Greeks named after the pedestal of a sundial; they called it an “analemma”. Of course, 10,000 years ago, they sometimes used some pretty big pebbles – Stonehenge is one example of a solstice calculator.

Stonehenge was used (in part) to calculate the winter solstice (Image courtesy English Heritage)

Stonehenge was used (in part) to calculate the winter solstice
(Image courtesy English Heritage)

Today we’ve managed to shrink the size of the stones that we use to do calculations, and we’ve found ways to get more calculations from them. And one of the best way of doing this is by linking your silicon-based calculator (that is, your computer) to others so that researchers can perform calculations that are too big or too complicated for any single computer. (Match that, Stonehenge!) One project that is using this sort of distributed computing is the SkyNet. They want to process radio astronomy data using your spare CPUs. To take part, set your browser to:
http://www.theskynet.org/

November 16 – Home Phone E.T.

Today’s factismal: The first interstellar message was sent on November 16, 1974. It will arrive in 25,000 years.

Quick! What’s big enough to hold 10,000 gallons of guacamole, deep enough to put a submarine in, precise enough to see supernovae 44 million light years away, and sent the first message to the stars? It is the Arecibo National Astronomy and Ionosphere Center (the Arecibo Observatory, or just Arecibo, for short).

Words (My camera)

The Arecibo “dish”, big enough for a submarine to hide in (My camera)

Back in the late 1950s, scientists were just learning about the ionosphere and wanted to develop a tool that would allow them to probe its secrets. And other scientists were learning about radio emissions from planets and stars, and wanted a tool to learn about those. And when the first group of wonks met the second group of wonks, a new telescope was born.

The idea was simple: because the same energy (radio waves) that is used to probe the ionosphere is also used to learn more about distant planets and stars, instead of building two small instruments, why not build one huge one? They would get better resolution (thanks to the size of the reflecting dish), more power (thanks to the size of the transmitter/receiver), and more funding (thanks to the size of the project). And so they started looking for a place to build what would be the world’s biggest single aperture telescope, a title it would hold until 2016 when the Chinese opened their Five-hundred-meter Aperture Spherical Telescope.

The remains of the very first supernova ever recorded (Image courtesy NASA)

The remains of the very first supernova ever recorded
(Image courtesy NASA)

They had quite a few requirements on the location. It had to be in the US (thanks to the Cold War). It had to be near the equator (so it could see the planets). It had to be in an area with eroded limestone features called karst (so that it would be easy to build). And the spot that best fit was a little place called Arecibo on the island of Puerto Rico. So that’s where they built it and, on November 1, 1963, they started getting signals.

An image of the Crab Nebula at radio frequencies (Image courtesy NASA)

An image of the Crab Nebula at radio frequencies (Image courtesy NASA)

And what amazing things they saw! At the end of six months, they had discovered that Mercury wasn’t tidally-locked to the Sun like the Moon is to Earth; instead, it had a funny 3:2 rotation so that the day on Mercury appears to take two years! Soon they proved the existence of neutron stars, and mapped asteroids, and found complex molecules in outer space. But they weren’t limited to discovering things; they could also help things discover us. On November 16, 1974, Carl Sagan and friends took over Arecibo and used it to send a message to globular cluster M13, letting ET know where to phone.

Globular cluster M13, target of our first message (Image courtesy NASA)

Globular cluster M13, target of our first message
(Image courtesy NASA)

Unfortunately, Sagan was a better showman than he was an astronomer. In sending the message, he forgot about “proper motion” and sent the message to where the cluster appears to be in the sky. Because M13 is some 25,000 light years away, where it appears to be tonight is actually not where it is now – or where it will be when the message arrives! Imagine that you are walking along and tossing out pebbles every so often. The pebbles take a second to so to hit the ground so that you are in a different place when they land than you were when they were thrown. The same thing is happening here; the light from M13 left 25,000 years ago when the globular cluster was in a different place and it will have moved yet more in the 25,000 years it will take for the message to arrive.  As a result, our message will miss M13 almost entirely and instead head out into deep space.

arecibomessage

Arecibo continues its mission of discovery today. One of its most important missions today is the search for black holes – and they need your help! Just go to Radio Galaxy Zoo and help match radio telescope pictures to infrared telescope images. Fun, easy, and really, really cool!
https://radio.galaxyzoo.org

October 5 – Sweet Nothings

Today’s factismal: In 1988, Takaaki Kajita and Arthur McDonald discovered that the Sun wasn’t going to explode.

If you look at the Sun (which you shouldn’t do because it can cause serious damage to your eyes), then odds are you’ll see it as a bright, burning spot in the ten seconds or so that you have before you do serious damage to your eyes (told you so). But when an astronomer looks at the Sun through a telescope with a strong filter that makes it safe to do so, she sees something different. The astronomer sees both the source of all our power and an amazing set of atomic reactions known as the solar phoenix. In this reaction, six protons combine to form a helium nucleus, two spare protons, two gamma rays, and two anti-electrons (aka positrons). But there is something else created in that reaction; something that is so small and slippery that it is almost impossible to catch: the neutrino.

The solar phoenix reaction. The little νs are neutrinos being given off in the first stage.

The solar phoenix reaction. The little νs are neutrinos being given off in the first stage.

The neutrino is special because without it, the solar phoenix reaction simply can’t happen. Even though it is so small that it would take a million of them to have the same mass as a single electron, the neutrino is essential to the solar phoenix and many other nuclear reactions. It is created in nuclear reactors as a byproduct of fission; roughly 4.5% of the energy in a nuclear reactor is lost as neutrinos!

And the neutrino can also be created by particle accelerators. When they smash two tiny protons or electrons together, they make even smaller bits, one of which is the neutrino. Neutrinos are made in so many ways that they are the second most common particle in the Universe (after the photon), and may be responsible for the “missing mass” known popularly as Dark Matter.

Neutrinos are very, very, very, very, very, very small

Neutrinos are very, very, very, very, very, very, very, very, very, very, very, very, very, very small

The neutrino is special in another way, too. It is the only particle that has been the cause of five Nobel Prizes. The first went to Enrico Fermi in 1938, who predicted its existence in 1933 based on a “missing” amount of energy in what physics wonks call slow neutron reactions (this also led to the discovery of the weak force); amusingly, Fermi’s paper was rejected by the leading scientific journal of the day as being “too remote from reality”. The second was given in 1995 to Clyde Cowan, Frederick Reines, F. B. Harrison, H. W. Kruse, and A. D. McGuire who discovered the neutrino in 1956 (take THAT, leading scientific journal). The third went to Leon M. Lederman, Melvin Schwartz and Jack Steinberger in 1988 for their discovery in 1962 that there was more than one type of neutrino; physicists refer to the three types as flavors because whimsy. The fourth Nobel Prize for neutrino-related work was given in 2002 to Raymond Davis, Jr. and Masatoshi Koshiba for their detection of neutrinos from a supernova; today, the field they founded is known as neutrino astronomy. And the fifth prize (thus far) was awarded in 2015 to Takaaki Kajita and Arthur McDonald who proved that neutrinos change flavors as they move.

The Sun generates energy by making big atoms out of little ones (Image courtesy NASA)

The Sun generates energy by making big atoms out of little ones (Image courtesy NASA)

That is important because until 1988, there was serious concern that the Sun might be going out; about half of the astrophysicists thought it would be with a whimper and the other half thought it would be with a bang. That was because we weren’t detecting the right number of neutrinos from the Sun. Even though the neutrino is so small and interacts too weakly with other matter that it is almost impossible to catch, the Sun puts out so many neutrinos (roughly 1.3 x 1018 each second, or 185 million for every person on Earth) that we can still see some of them. Only we weren’t seeing enough of them. Though we knew that neutrinos had different flavors, the Standard Model in physics said that the neutrinos should stay the same flavor; discovering that they changed flavors would mean that the Standard Model was wrong.

The Sudbury Neutrino Observation detector being installed (Image courtesy CoolCosmos)

The Sudbury Neutrino Observation detector being installed
(Image courtesy CoolCosmos)

And in 1988, using neutrinos captured from reactions in the atmosphere and neutrinos from the Sun’s core, two teams led by Takaaki Kajita and Arthur McDonald discovered that neutrinos do indeed change flavor. The Standard Model was wrong (and the Sun was saved). Thanks to their work, we are learning more about how these small but vital particles help the Universe go round. And last year, they were awarded the Nobel Prize for their work.

If you’d like to learn more about particle physics and maybe do a little prize-worthy work of your own, why not head over to LHC@Home? This website, offered by the same folks who invented the internet, has several different ways to get involved in the search more new and even more interesting particles. To learn more, zip on over to:
http://lhcathome.web.cern.ch/