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 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

 

 

 

August 11 – Pretty But Deadly

Today’s factismal: Meteor showers are named after the constellation that they appear to come from.

If you go outside tonight or tomorrow night, you’ll be treated to not one but two astronomical amazements. The first is the sight of the Saturn and Mars lying less than a hand’s breath away from the Moon in the sky; if you go out just after sunset you’ll also be able to see Jupiter, Mercury, and Venus down low in the west. And beautiful as that set of planets is, it won’t be the most amazingly beautiful thing in the sky. That’s because tonight and tomorrow are the peak of the annual Perseid meteor shower.

Tonight's astronomical wonder (Image courtesy NASA)

One of tonight’s astronomical wonders
(Image courtesy NASA)

The Perseids happen when the Earth crosses the path of the comet Swift-Tuttle every year. Like a car getting hit by gravel flung off of the truck ahead, the Earth runs into the bits of dust and rock thrown off by Swift-Tuttle on its 130 year long journey around the Sun. The comet last passed by the Earth in 1992 (we’ll see it again in 2026) and left lots and lots of junk on our cosmic road. When that a piece of that junk hits the windscreen that is the Earth’s atmosphere, it heats up and forms the long, glowing trail that we call a “shooting star”. Thanks to the recent close encounter, we expect to see up to 200 meteors each hour in darker places. But even if you live in the city, you can expect to see some of the brighter meteors.

A meteor shower radiating (Image courtesy NASA)

A meteor shower “radiating”
(Image courtesy NASA)

To catch the light show, just go outside and look up. If you’d like a better chance at catching the falling stars, turn to the northeast at about 10 PM. Using your fist at arm’s length, count up two fists. That puts you right in the middle of the constellation of Perseus; if you hit the “W” of Cassiopeia, you are too high. And now just watch. The meteors will appear to radiate out of the center of Perseus which is why they are called the  Perseids.

Where to look tonight and tomorrow night (Image courtesy NASA)

Where to look tonight and tomorrow night
(Image courtesy NASA)

And meteors are more than just pretty; they can tell us a lot about comets and planets. And you can help! 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/

August 5 – Comet Chameleon

Today’s factismal: The word comet means “long-haired”.

Back in the days of the ancient Romans, when a comet would appear in the sky it was always an evil omen; they considered it to be a “bad star” or disaster. Even though the comet signaled death, destruction, and the start of the primary season, the Romans and Greeks kept their sense of humor. Because the comet had two long tails streaming out like hair in a sea breeze, they called it “long haired” or komētēs.

Comet Lovejoy as seen from the ISS (Image courtesy Dan Burbank, NASA)

The two tails of Comet Lovejoy as seen from the ISS
(Image courtesy Dan Burbank, NASA)

Nowadays we don’t think of comets as being evil omens but we are still fascinated by the tails that they trail, starting with the number of tails – two.  A comet has two tails because it is made of two types of stuff. Thanks to spectroscopy, we know that the nucleus is mainly made up of ices (water ice, ammonia ice, and even methane and carbon dioxide ice) with pieces of dust for texture; this mixture of rock and ice is why comets are often called “dirty snowballs”.

The two tails of Hale-Bopp (Image courtesy NASA)

The two tails of Hale-Bopp
(Image courtesy NASA)

As the comet gets closer to the Sun the outermost ice heats up and spews out gasses that form a globe called the coma (which means “hair” – yep, those Greeks had a thing). 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.

Comet Hyakutake passes the Sun (Image from SoHo)

Comet Hyakutake passes the Sun (Image from SoHo)

The interesting thing about the tails is that they do more than expand. Thanks to all that heat from the Sun, they also glow. And scientists can use that glow to tell us what the comet is made of; things like amino acids and phosphorus – the building blocks of life. Scientists have been doing this for an amazingly long time; on August 5, 1864, Giovanni Batista Donati did the first spectroscopic analysis of a comet and discovered that they had carbon in them. The other interesting thing about comet tails is that they can help us know where the comet formed. Because different things turn solid at different temperatures, by looking for these things in a comet’s tail, we can learn how far away from the Sun it was when it was born. But in order to do that, we need more information on comets.

Comet Sealy in the Texas night sky (My camera)

Comet ISON in the Texas night sky
(My camera)

And that’s where you come in. Comet Hunters is looking for comets that have become trapped in the asteroid belt by Jupiter. If you look through the images from Hawai’is Subaru telescope on Mauna Kea, you might spot one hiding in among the rocks. To learn more (and chase some tails), head over to:
https://www.zooniverse.org/projects/mschwamb/comet-hunters

November 6 – No Bull

Today’s factismal: The Taurid meteor shower looks like it is coming from Taurus the bull.

One of the cool things about the Earth is how often it gets hit by a meteorite. On average, 42,000 meteorites hit the Earth every year. That works out to be about 150 strikes each day! But some days are more average than others, and we are having a few of those days right now because we are in the middle of the Taurid meteor shower.

Named for Taurus the bull, which is the constellation just to the right of Orion as you look at it in the sky, this meteor shower happens when the Earth’s orbit takes it through the debris of comet Encke. As comets move closer to the Sun, they heat up and begin to outgas (which means just what it sounds like: they start to give off gas in noxious clouds {like Uncle Joe} and in large jets {like Aunt Sally}). The outgassing also breaks off small chunks of the comet which form a giant debris trail in the sky. Most of these chunks are about the size of a grain of sand, but some can be much larger. When the debris from the comet meets the Earth’s atmosphere, they create the meteor.

These eight images show how much gas is jetted off of a comet in just half an hour! (Image courtesy NASA)

These eight images show how much gas is jetted off of a comet in just half an hour!
(Image courtesy NASA)

Encke is pretty famous in astronomical circles; it was the second periodic comet every discovered (after Halley’s comet). A large reason for it being discovered was the fact that it has a very short period – just 3.3 years! Thanks to that short period, Encke has been shedding tons of dust and rocks into space. And thanks to that shrot period, we are fairly sure that Encke itself is the remains of a larger comet that broke apart some 20,000 years ago. Because it is so new, Encke has created one of the largest and broadest swaths of cosmic debris in the Solar system. Instead of lasting for a few days, the Taurid meteor shower typically lasts for a month!

The best place to watch a meteor shower, ever! (Image courtesy NASA)

The best place to watch a meteor shower, ever!
(Image courtesy NASA)

And if you’d like to do more than just ooh and aah at the pretty meteor as they burn up, why not download NASA’s Meteor Counter App (available for iPad, iPhone, and iWannaMeteor)? You’ll be able to send NASA scientists valuable information on the number of meteors that hit during the shower. To get the app, go to the iTunes store:
https://itunes.apple.com/us/app/meteor-counter/id466896415

June 12 – Wham Bam

Today’s factismal: The Earth gets hit by about 42,000 meteorites each year.

Ask any third grader what killed the dinosaurs and odds are she’ll tell you that an asteroid did it. (That’s not quite correct but it is close enough for now.) And if the third grader is especially clever, she may even know the name of the asteroid: Chicxulub (“Chick-sue-loob” or “the well of the great horns”). Like all major impact structures, the name comes from the closest town and not from the actual asteroid; those are usually given names like 2060 Chiron or 1992 QB1 or 1999 FN53. But what your third grader may not know is that Chicxulub was hardly the only asteroid to every hit the Earth.

Every day, nearly 170 meteorites hit the Earth; that adds up to 42,000 meteorites each year! (For the purposes of this article, we’ll treat asteroids and meteorites and comets as being roughly equivalent simply because they are, planetologically speaking.) Most of these are small pieces of rock and ice about the size of a grain of rice that burn up in the outer atmosphere leaving nothing behind but a little dust and a pretty lightshow. But about 2,800 of those meteorites each year are large enough to actually make it deeper into the atmosphere.

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)

Every year, about 500 meteorites survive their fiery plunge through the atmosphere and make it to the ground. Most of those are small and do little damage, but every once in a while we get something a little larger that causes trouble. In 2013, a meteor that was 60 ft across and weighed more than the Eiffel tower fell above Chelyabinsk, Russia. When it exploded in the sky, it created a shockwave that shattered glass for miles around, injuring more than 1,500 people who had gone to the window to see what the pretty bright light was. When it was all over and done, the Chelyabinsk meteor left behind $33 million in damages, more than 1,500 pounds of fragments, and a 20 ft wide hole known as an “astrobleme” (star wound) in the trade or a “meteor crater” to news reporters.

And that isn’t the worst that could happen. Based on what we know right now, scientists expect to see an impact creating a Chelyabinsk style crater roughly every 250 years, an Odessa style 500 ft crater every 540 years, a Wolfe Creeksized half-mile across crater every 13,000 years, a (Barringer) Meteor Crater mile-wide crater every 21,000 years, a Pingualuit two mile across impact every 50,000 years, and a Chicxulub 110 mile across crater every 100,000,000 years. As you might guess from that big gap at the end, there is still a lot that we don’t know for sure about impact craters.

The Pingualuit impact crater (Image courtesy NASA)

The Pingualuit impact crater (Image courtesy NASA)

But we can learn. And surprisingly on of the best places to learn about impact craters is from the things that make them – asteroids! That’s because unlike the Earth, which has wind and water and plate tectonics to erase old impact craters, the asteroids just have impacts to erase other impacts. So by examining impact craters on asteroids, we can learn more about how they happen on Earth which can help us keep another Chicxulub from knocking on our planet one day. If you’d like to learn more about imact craters on asteroids, why not zoom over to Vesta Mappers at Cosmo Quest? They’ll show you how to identify impact craters on the latest images of Vesta and then let you loose on the newest data we’ve got!

https://cosmoquest.org/?application=vesta_mappers

January 2 – Glowing With Pride

Today’s factismal: Citizen scientist Terry Lovejoy has discovered five comets, one of which can be seen tonight!

If there’s one thing an astronomer likes better than dark nights, it is citizen scientists. That’s because folks like you and Terry Lovejoy who go out and watch the stars are responsible for pretty amazing discoveries. WHo is Terry Lovejoy? He’s a citizen scientist who lives in Australia and searches for comets as a hobby. Thus far, he’s identified five different comets, all of which now carry his name.

Comet Lovejoy as seen from the ISS (Image courtesy Dan Burbank, NASA)

Comet Lovejoy as seen from the ISS
(Image courtesy Dan Burbank, NASA)

The most recent of the comets that he’s discovered is Lovejoy C/20011 W3. This comet comes from far, far out in the Solar System; when it is at its farthest, it is 157 times farther from the Sun than the Earth is. For simplicity’s sake, astronomers call the distance between the Sun and the Earth an Astronomical Unit and abbreviate it AU; so comet Lovejoy goes 157 AU out. For comparison, the most distant man-made object is Voyager 1 which is a mere 130 AU. Over the course of about 166 years, comet Lovejoy goes from its farthest point to a place just 0.00555 AU and back out again. That close approach makes this comet a “sun grazer”. And the cool thing about sun grazers is that they frequently become “great comets” that are so bright they can be seen in the daytime!

Comet Lovejoy as it speeds toward the Sun (Image courtesy US Naval Observatory)

Comet Lovejoy as it speeds toward the Sun
(Image courtesy US Naval Research Laboratory)

Unfortunately for us, comet Lovejoy isn’t likely to be a great comet; it has already passed as close to the Sun as it is going to on this trip and it only got as bright as the planet Venus (which is still pretty darn bright!). Fortunately for us, comet Lovejoy did get bright enough to see with the naked eye (though a pair of binoculars really makes it “pop”!) and is located near the one constellation that everyone knows – Orion! For the next month, comet Lovejoy will appear to move from Rigel, the red star that makes up Orion’s foot, to the Pleiades, the “seven sisters” that dance near Orion. (And, if you are out looking at the comet with your binoculars, spare a little time to look at the middle of Orion’s sword and at the Pleiades through the binoculars. You’ll be amazed at what you find!)

Comet Lovejoy's path through the heavens (Image courtesy Sky and Telescope)

Comet Lovejoy’s path through the heavens
(Image courtesy Sky and Telescope)

Being a sun grazing comet, comet Lovejoy won’t be around forever. There are literally dozens of other comets that dive-bomb the Sun each day, many of which never make it back out to where they were born. If you’d like to learn more about comets (and maybe identify a few yourself), then head over to SOHO’s Comet Hunting page:
http://sungrazer.nrl.navy.mil/index.php?p=guide