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/

January 9 – Miss Demeter

Today’s Factismal: Ceres was first thought to be a comet.

Most astronomy fans know Ceres by reputation if not by name. It is the largest body in the asteroid belt, that loose pile of rubble that never quite coalesced into a real planet back when the Solar System was being built. It is small enough that you could it would take 78 chunks of rubble the size of Ceres to build one Moon. But what most astronomy fans (and other folks) don’t know about Ceres is that it has caused trouble for astronomers from the day it was found – and continues to cause trouble today!

When Giuseppe Piazzi first observed Ceres in 1801, he called it a comet. But Johan Bode decided that it was in the right place to be the “missing planet” he was looking for between Mars and Jupiter, and so he called it a planet and gave it an astronomical symbol. Unfortunately for Ceres, astronomers soon discovered over a hundred more “missing planets” in the same neighborhood, and they took to calling it a minor planet (astronomers get upset whenever there are more than ten planets; nobody knows why) when they didn’t call it an asteroid (astronomy speak for “tiny little star-like thingamabob”). And then, when yet more Pluto-sized objects were found in the outer Solar System, Ceres was reclassified yet again as a dwarf planet (see the previous note about astronomers and numbers bigger than ten).

An image of Ceres, taken by the Hubble Space Telescope

An image of Ceres, taken by the Hubble Space Telescope

Even its name is a subject for debate. In America, it is known as Ceres, for the Roman goddess of the harvest. But the Greeks have never consented to that name; they prefer to call it Demeter (which causes all kinds of confusion as there is another asteroid known as 1108 Demeter). And the Germans prefer to call it Hera for reasons that are inscrutable to anyone but a German.

Ceres as seen by the DAWN probe (Image courtesy NASA)

Ceres as seen by the DAWN probe
(Image courtesy NASA)

What is not in doubt is that Ceres is large enough to be shaped into a ball by its gravity, and that it has an interior that is divided into an icy outer part, a rocky middle section, and a metallic core (i.e., meets the definition of planet for everyone but the IAU). It is also possible that Ceres has an inner ocean between the outer icy part and the rocky middle; this is exciting because it makes Ceres one of the few places in the Solar System where life as we know it could exist. Ceres’ size and shape tell us that it is a relic of the early days of the Solar System, when everything was collapsing into small bodies that then collided to form the planets. So we can add planetismal and protoplanet to Ceres’ list of appellations.

The layers of Ceres, as we now know them. We expect to learn a lot more about Ceres once DAWN arrives there in 2015. (Image courtesy NASA)

The layers of Ceres, as we now know them. We expect to learn a lot more about Ceres once DAWN arrives there in 2015. (Image courtesy NASA)

Right now, the DAWN spacecraft is orbiting Ceres. Planetologists (i.e., the folks who still classify Pluto as a planet) are studying the asteroid in order to learn more about how planets form and develop over time, and to see evidence of the early history of the Solar System. They’ll also compare Ceres, which is the largest asteroid, with Vesta, which is the second largest and was visited by DAWN in 2013. As part of the NASA mission, JPL has launched the Asteroid Mappers website, where you can help to identify features on Ceres and Vesta:
http://dawn.jpl.nasa.gov/DawnCommunity/asteroid_mappers.asp

December 31 – Hairy Situation

Today’s factismal: The New Year will start with not one but two comets!

There is something special about comets in the sky. These “long haired” wanderers do more than just provide a spectacular light show; they also create meteor showers and change the way we think about the world. And for the next couple of weeks there will be not one but two comets visible in the sky!

The first one is a regular visitor. Called Comet 45P/Honda-Mrkos-Pajdušáková (after the three people who discovered it), it is a member of the “Jupiter family” of comets. These are short-period comets that cycle between rushing by the Sun before heading back out toward Jupiter to cool their heels for a bit. 45P has a period of about five years; the last time it fly by the Sun was in 2011 and the next time will be in 2022.  And it will come relatively near Earth on February 11, 2017 – it will be just about eight million miles away! (If that sounds too close, remember that the Moon is about thirty times closer.) If you can’t wait, go out just before dawn and look to the East with binoculars. That faint, fuzzy patch? That’s the comet. It will get bigger and brighter over the next few weeks so you’ll have plenty of opportunities to see it.

Comet 45P as it flies from Jupiter's orbit in toward the Sun and back (Image courtesy NASA)

Comet 45P as it flies from Jupiter’s orbit in toward the Sun and back
(Image courtesy NASA)

But that’s not the only comet we can see tonight! There is also comet C/2016 U1 NEOWISE which was discovered by NASA’s NEOWISE project. Using images from the WISE space telescope, which spent a year surveying the sky in infrared, the folks at JPL have identified this long-period comet. Instead of just sprinting between Jupiter and the Sun, these comets run all the way from out past Pluto; as a result, their journeys can take tens of thousands of years. Right now, we aren’t sure how long this particular comet takes to complete an orbit or even if it will be ejected from the Solar System. What we do know is that it has already passed its closest approach to Earth and is heading in toward the Sun. As it gets closer, it will get brighter and may be visible to the naked eye early in the morning between now and January 14th when it passes the Sun and heads back out again.

A timelapse photo from SOHO showing what happens to a comet as it goes around the Sun (Image courtesy ESA)

A time lapse photo from SOHO showing what happens to a comet as it goes around the Sun
(Image courtesy ESA)

As comets get closer to the Sun the outermost ice heats up and spews out gasses that form a globe called the coma (which means “hair”). The gasses in the coma then become ionized and get dragged out by the solar wind forming the long glowing tail that is characteristic of comets; this gas tail always points straight away from the Sun. Little flakes of rock dust can also be lost. Because the dust is denser than the gas and isn’t ionized, it can form a second tail that curves away from the comet. (So straight tail=gas, curvy tail=dust. Now go impress your friends.) That dust is left behind in orbits that sometimes lead it to fall on Earth as fireballs.

The surface of a comet as seen by ESA's Rosetta probe (Image courtesy ESA)

The surface of a comet as seen by ESA’s Rosetta probe
(Image courtesy ESA)

And you can see the show using a pair of good, inexpensive binoculars. Binoculars are preferred by new astronomers because they gather a lot of light, which helps you see faint things, and because they give enough magnification, so you can see things like the moons of Jupiter, and because they are inexpensive (about $50). Or, if you’d like to spend about $1,000,000,000 you could launch another Solar and Heliospheric Observatory or SOHO for short.

This satellite, which was launched in 1995 and is still active today, was intended to observe the Sun and tell us more about how solar flares and coronal mass ejections affect life on Earth. But what NASA hadn’t expected when they launched SoHo was that they would see comets. But it turned out that SoHo saw a lot of comets that came to be called “Sun-grazers” for their death-defying feat of diving in near the Sun before heading back out into the dark depths of the outer Solar System.

Sometimes the stress of passing near the Sun or a planet causes a comet to break into pieces (Image courtesy ESA)

Sometimes the stress of passing near the Sun or a planet causes a comet to break into pieces
(Image courtesy ESA)

SoHo is still in orbit today, looking at the Sun and looking for comets. If you’d like to join the folks that have found more than 2,400 comets using SoHo images, then head on over to Sungrazing Comets:
http://sungrazer.nrl.navy.mil/index.php?p=guide

 

 

 

November 30 – Map Quest

Today’s factismal: The first map of the Moon was made 407 years ago today.

Back in the 1600’s, there were only two things that everyone was sure of: death and the fact that things in the heavens were perfect. The first was kind of obvious thanks to smallpox, war, famine, and straight party ticket voting, and the second had to be true because Aristotle said it and the Roman Catholic Church believed it. At the time, it was thought that anything on Earth was corrupt thanks to Adam’s sin while anything in the skies was part of Heaven and therefore incorruptible. So you can imagine the furor when Galileo took the telescope he invented and turned it to the Moon – and then told everyone what he saw.

Galileo's telescope revolutionized our view of the Universe - literally!

Galileo’s telescope revolutionized our view of the Universe – literally!

And what he saw was revolutionary. Instead of being a perfect, smooth sphere, the Moon was covered with pockmarks and scars – what we know now to be impact craters and lava flows. While today all of the attention is given to Galileo’s proofs that the Earth was not the center of the Universe, it was his demonstration that the heavens were imperfect that struck the most direct blow at the Roman Catholic Church’s philosophy. As a result, even though anyone could verify the truth of Galileo’s work by simply looking, many preferred not to do so lest they also fall into heresy.

Galileo's map of the Moon (Image courtesy Galileo)

Galileo’s map of the Moon
(Image courtesy Galileo)

If you aren’t afraid of heresy then go out to look a the Moon tonight and take a long gander at the big black splotch that’s looking back at you. That’s Oceanus Procelarum, or the Ocean of Storms. It was named in 1655 (46 years after Galileo published his map) by Giovanni Riccioli, a Catholic priest who liked Galileo’s results but not his methods. To “punish” Galileo and his friends for disproving Church doctrine, he used the names of those who supported the heliocentric universe for the craters nearest Oceanus Procellarum which turns out to be one of the largest outflows of lava anywhere in the Solar System. That big white blotch on the eastern side of the stormy ocean? That’s Copernicus Crater, named for the chief heliocentricist and all-around troublemaker; those long white streaks are bits of lunar rock and dust that were thrown out when the asteroid slammed into the Moon and formed the crater.

A modern view of the Moon (Image courtesy NASA)

A modern view of the Moon
(Image courtesy NASA)

And while you may not believe it, we are still naming things on the Moon today! Even after four centuries of discoveries, there are still new features to see on the Moon and new things to identify. By mapping every crater and every lava flow and every mountain, we can get a better idea of how the Moon has changed over time and learn more about how the Solar System formed. And the best part is that you can help! Just head over to Cosmo Quest and start clicking on the Moon pictures to tell them what you see. For more information, land at:
https://cosmoquest.org/x/?application=simply_craters

November 28 – Red Headed Menace

Today’s factismal: There have been 55 probes to Mars since the first one launched 52 years ago today.

Back in 1964, the US and the USSR had one thing in common – neither one of them could get a spacecraft to Mars. The two countries were engaged in a space race, trying to show that they could do more and go further than the other but all of their probes to Mars failed. The USSR had launched five different probes to Mars, only one of which had made it out of Earth orbit. The US had launched just one probe but the cover on it had failed to separate, meaning that the probe couldn’t make it to Mars. And then came Mariner IV.

A close-up of a crater on Mars (Image courtesy NASA's HiRISE)

A close-up of a crater on Mars
(Image courtesy NASA’s HiRISE)

Based on the successful Ranger probes that had explored the Moon, the Mariner was designed to take photos of Mars’ surface and send them back to Earth; it also would measure cosmic rays in space, look for changes in solar wind and plasma, and discover how much dust was in the Solar System. All of these things would be important if we were ever to travel to Mars. At 2:27:23 PM UTC on November 28, 1964, atop an Atlas missile with an Agena booster, the Mariner probe headed for the skies and then for Mars. It would fly past the Red Planet 228 days later and send back the first close-up images ever taken of the planet.

The first close-up picture of Mars (Image courtesy NASA)

The first close-up picture of Mars
(Image courtesy NASA)

Today there are eight different probes in orbit around or exploring the surface of Mars. They are telling us about its climate, its atmosphere, its composition, how it has changed over time, and (most importantly) if it has life living below its surface. And the best part of the exploration of Mars is that you can be a part of it. Just fly over to Planet Four: Terrains and tell them what you see in each image (craters, sand dunes, little green men). The scientists will use your classifications to help them understand how Mars has changed over the years. To learn more, land on:
https://www.zooniverse.org/projects/mschwamb/planet-four-terrains/about/research

November 14 – Supermoon!

Today’s factismal: Not all full moons happen when the Moon is closest to the Earth.

There’s a good reason that they call it “rocket science” (OK, actually they call it “astrophysics”); figuring out what is happening in the sky is hard. That’s because things are moving all around and interacting with each other in all sorts of weird ways. Let’s take something simple for example – the Earth-Moon-Sun system. You’d think that with just three bodies orbiting each other there would be an exact mathematical description of how things will move. And you’d be wrong! Though we can solve certain special cases, in general we cannot tell how the motion of the three bodies will change more than a short time into the future (a million years or so).

The Sun, Earth, and Moon, drawn to scale (almost - the Moon is three times as large as it should be)

The Sun, Earth, and Moon, drawn to scale (almost – the Moon is three times as large as it should be)

But we can tell some things for sure. For example, we know that a full moon happens when the Moon and Sun are on the opposite sides of the Earth. And we know that the Moon’s orbit around the Earth is not a perfect circle; instead it is an ellipse that slowly moves around the Earth. Since an ellipse has a part that comes closer to the Earth and a part that is farther away, sometimes the full moon happens farther away from the Earth and sometimes it happens closer. Things being what they are, most of the time the full moon happens farther away. But when it happens close to the Earth (what astronomy wonks call perigee {“close to Earth” in Greek}), we get a Supermoon.

The Earth-Moon system, draw to scale. Notice how the Moon's orbit is slightly elliptic.

The Earth-Moon system, draw to scale. Notice how the Moon’s orbit is slightly elliptic.

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How super is a Supermoon? Not very. Because the Moon’s orbit is an almost perfect ellipse, the Supermoon is only about 14% larger than a normal full moon. Unless you are very, very observant you’ll never notice the difference. You can see the exact difference in the images below. This first image shows a full Moon over China, taken by Expedition 48 Commander Jeff Williams on the ISS. The second image shows what a Supermoon would look like.

A full Moon over China (Image courtesy Expedition 48 Commander Jeff Williams, NASA)

A full Moon over China
(Image courtesy Expedition 48 Commander Jeff Williams, NASA)

What a Supermoon would look like

What a Supermoon would look like (Modified image)

Now even though the Supermoon isn’t spectacular, that doesn’t mean that the Moon isn’t special. It is our nearest neighbor and can tell us a lot about how the Earth and the rest of the Solar System formed. If you’d like to get in on the fun of discovering more about the Moon, then head on over to Moon Mappers where folks just like you are telling scientists what they see on the super-duper Moon!
https://cosmoquest.org/x/science/moon/