I love questions from my readers! So far I have received two, and I will answer one in this post. The other will have to wait a bit, it was pretty complicated. (It has to do with the space time continuum, in case you're curious.) But before I go on, I would like to reiterate that I love love love questions from readers. So ask away!
Flem in Santa Barbara, CA asks: "I need to know if it is possible that I saw a comet last weekend or if it was just an amazing shooting star that lasted for a couple of seconds."
Short answer: a meteor, not a comet.
Long answer: Comets are big balls of ice and dust (imagine a dirty snowball a few miles across) that orbit the sun in elliptical (oval-shaped) paths. As they orbit the sun, sometimes they are in a location where we can view them from Earth. When we see a comet in the sky, it looks like a kind of dim star with a faint tail behind it. Comets appear in the sky for weeks or even months, in pretty much the same spot night to night. Meteors are flashes of light created when specks of dust, most around the size of a grain of sand, enter the earth's atmosphere and the friction between air and the dust causes a tunnel of flames. (Contrary to the popular misnomer, meteors are not shooting stars at all; meteors=light from a speck of dust, stars=huge burning balls of gas a million miles across.)
So if you saw something bright flash across the sky and then disappear in a matter of minutes, I'm going to say it was a meteor and not a comet. It may have even been a stray Quadrantid.
Saturday, January 31, 2009
Friday, January 30, 2009
Spotting Venus
Venus is a prominent part of the night sky lately. You may have seen it in the west after sunset, shining brighter than any of the stars. Because it is the closest planet to Earth and is covered in reflective clouds, it is really bright. In fact, in my former life, I used to get voice mails from people claiming they saw a UFO, describing in perfect detail the location, brightness and appearance of the planet Venus. And I was 100% unsuccessful in my endeavors to persuade them to consider they were looking at Venus, not cosmic messengers from another dimension. Oh well.
If you want to make sure you're seeing Venus and spare your poor local astronomer some "I just got another call from a UFO kook" grief, use this chart to go out and find it tonight. Or any other night for the next month or two; it'll be around for the next couple of months. As a special bonus for being timely, if you go out in the next night or two, Venus will be near the crescent moon.
Image and credit: Roen Kelly, Astronomy.com
If you want to make sure you're seeing Venus and spare your poor local astronomer some "I just got another call from a UFO kook" grief, use this chart to go out and find it tonight. Or any other night for the next month or two; it'll be around for the next couple of months. As a special bonus for being timely, if you go out in the next night or two, Venus will be near the crescent moon.
Image and credit: Roen Kelly, Astronomy.comThursday, January 29, 2009
Where Would You Point Hubble?
I remember working in the Space Lab at the Santa Barbara Museum of Natural History as an exhibit interpreter when I was a teenager. We had one exhibit labeled "Where Is Hubble Now?" People would always be really surprised to see that the display was a spherical model of Earth viewed from a bit out in space with a dot labeled "HST" near it. For some reason, far too many people think that the Hubble Space Telescope has actually traveled hundreds, thousands or even billions of lightyears through space to take the images it sends back to Earth. Of course you and I both know that's not true; HST is in low Earth orbit at a distance of 559 km above the earth.
HST takes great images because it's out of Earth's atmosphere. Trying to do astrophotography on the surface of the earth is like taking a picture from the bottom of a swimming pool; our turbulent atmosphere is always moving and flowing, which wreaks havoc on all those photons we're trying to capture. HST doesn't have that problem and, as a result, it takes some of the best images ever recorded of our universe.
If you were in charge of the Hubble Space Telescope for a day, where would you point it? NASA is giving you a chance to decide! In honor of IYA (see, I'm not the only one excited about it!), the folks at HubbleSite are offering us the people the chance to decide on what Hubble will study next. You can vote online here. If you're an educator, you can also register to receive a free Hubble Education Package. I won't tell you what I voted for, but I'll give you a hint: I voted for a "peculiar" target which gravity has distorted.
HST takes great images because it's out of Earth's atmosphere. Trying to do astrophotography on the surface of the earth is like taking a picture from the bottom of a swimming pool; our turbulent atmosphere is always moving and flowing, which wreaks havoc on all those photons we're trying to capture. HST doesn't have that problem and, as a result, it takes some of the best images ever recorded of our universe.
If you were in charge of the Hubble Space Telescope for a day, where would you point it? NASA is giving you a chance to decide! In honor of IYA (see, I'm not the only one excited about it!), the folks at HubbleSite are offering us the people the chance to decide on what Hubble will study next. You can vote online here. If you're an educator, you can also register to receive a free Hubble Education Package. I won't tell you what I voted for, but I'll give you a hint: I voted for a "peculiar" target which gravity has distorted.
Friday, January 23, 2009
What Good Is a Telescope? Part 3
As we celebrate IYA and Galileo's use of the astronomical telescope, it's time for some clarification. Galileo was not the first person to use a telescope. He wasn't even the first person to use a telescope for astronomical purposes. That honor goes to Thomas Harriot, an English astronomer who drew maps of the moon several months before Galileo. In fact, his very detailed diagrams were some of the best of the period. Unfortunately, he never published those maps or anything else related to his astronomical observations. He was well off and didn't need the income; it seems he pursued astronomy as a hobby and was content to keep his drawings to himself.
So as we honor Galileo for his discoveries and contributions, let's give a shout out to Thomas Harriot, who proved that if you don't publish, you just may perish (historically speaking). To hear more, you can check out this podcast from 365 Days of Astronomy, although it's a bit dry.
Thanks for joining me for this three part series. Check back next week for information on how and where you can see Venus!
So as we honor Galileo for his discoveries and contributions, let's give a shout out to Thomas Harriot, who proved that if you don't publish, you just may perish (historically speaking). To hear more, you can check out this podcast from 365 Days of Astronomy, although it's a bit dry.
Thanks for joining me for this three part series. Check back next week for information on how and where you can see Venus!
Thursday, January 22, 2009
What Good Is a Telescope? Part 2
Yesterday we left off with the geocentric view of our universe (with Earth at the center and everything else orbiting it), as propounded by The Church. Since this model could help predict the future positions of the planets, this meant power.
But of course, this couldn't last forever; absolute power and all that. The guy who changed everything forever was Galileo, and he did it with a telescope.
Galileo was an Italian scientist who became a student of Copernicanism upon reading works of Nicolaus Copernicus, an astronomer who died 21 years before Galileo was born. Copernicus maintained that the sun, not the earth, was the center of the universe (I'm using the term 'universe' as it would have been described at that time, not in our time). This model explained retrograde motion more clearly and simply that the geocentric model did, and thus provided more accurate predictions.
In the early 17th century, Galileo heard of a device called a spyglass and adapted a similar device to study the heavens. It was a simple device, a tube with a concave lens at one end and a convex lens at the other. It wasn't like a telescope you would use today; in fact, its power and quality were probably a bit less than a decent pair of binoculars today. To his credit, Galileo made vast improvements in the design of telescopes, eventually grinding his own mirrors and thereby drastically bettering his view of the universe.
Once he applied this new technology to the study of the stars, Galileo stumbled upon a cosmic quandry that would resolve the geocentric/heliocentric debate: the phases of Venus. If the geocentric view were to be correct, Galileo would never see Venus as more than a crescent in his telescope; if the heliocentric view were correct, Venus would grow from crescent to nearly full as viewed from the earth. Below are two animations demonstrating what each of these models would look like respectively.
Ptolemy's Model
Copernicus' Model
You guessed it; as Galileo studied Venus' phases through his telescope, he saw not just a crescent Venus but as time passed, all the way to a gibbous Venus in his field of view. And as quick as that, thousands of years worth of cosmological thinking were made obsolete.
You probably know the rest of the story. I won't go into details, but The Church wasn't particularly gracious about this new information (remember, astronomical knowledge = power); nor was Galileo gracious in his response. Nonetheless, the Scientific Revolution had begun and our understanding of the universe changed forever.
One last note: if you would like to listen to a fascinating account of all this, I highly recommend you give my fellow former planetarian Davin Flateau a listen. His podcast (part 365 Days of Astronomy podcast series) is available here. It's definitely worth nine minutes of your time. And the theme song is awesome!
Check back tomorrow for the exciting conclusion of our telescope tale.
But of course, this couldn't last forever; absolute power and all that. The guy who changed everything forever was Galileo, and he did it with a telescope.
Galileo was an Italian scientist who became a student of Copernicanism upon reading works of Nicolaus Copernicus, an astronomer who died 21 years before Galileo was born. Copernicus maintained that the sun, not the earth, was the center of the universe (I'm using the term 'universe' as it would have been described at that time, not in our time). This model explained retrograde motion more clearly and simply that the geocentric model did, and thus provided more accurate predictions.
In the early 17th century, Galileo heard of a device called a spyglass and adapted a similar device to study the heavens. It was a simple device, a tube with a concave lens at one end and a convex lens at the other. It wasn't like a telescope you would use today; in fact, its power and quality were probably a bit less than a decent pair of binoculars today. To his credit, Galileo made vast improvements in the design of telescopes, eventually grinding his own mirrors and thereby drastically bettering his view of the universe.
Once he applied this new technology to the study of the stars, Galileo stumbled upon a cosmic quandry that would resolve the geocentric/heliocentric debate: the phases of Venus. If the geocentric view were to be correct, Galileo would never see Venus as more than a crescent in his telescope; if the heliocentric view were correct, Venus would grow from crescent to nearly full as viewed from the earth. Below are two animations demonstrating what each of these models would look like respectively.
Ptolemy's Model
Copernicus' Model
You guessed it; as Galileo studied Venus' phases through his telescope, he saw not just a crescent Venus but as time passed, all the way to a gibbous Venus in his field of view. And as quick as that, thousands of years worth of cosmological thinking were made obsolete.
You probably know the rest of the story. I won't go into details, but The Church wasn't particularly gracious about this new information (remember, astronomical knowledge = power); nor was Galileo gracious in his response. Nonetheless, the Scientific Revolution had begun and our understanding of the universe changed forever.
One last note: if you would like to listen to a fascinating account of all this, I highly recommend you give my fellow former planetarian Davin Flateau a listen. His podcast (part 365 Days of Astronomy podcast series) is available here. It's definitely worth nine minutes of your time. And the theme song is awesome!
Check back tomorrow for the exciting conclusion of our telescope tale.
Wednesday, January 21, 2009
What Good Is a Telescope?
This month's IYA theme is telescopes. In fact, the reason this year is IYA is that 2009 marks the 400th anniversary of Galileo's first use of the astronomical telescope. So what? Why should you care?
I'm going to answer that question in three parts, each of which will go live in three consecutive days. So consider this the first part, but by no means the entire story. Check back for more tomorrow and the day after.
The first part of this story centers around the power of astronomy. The power of astronomy is the power to predict the future. That is to say, we all have enough astronomical knowledge to know that the sun will rise and set each day. We can plan around this and it gives us power. If we didn't have that knowledge, we wouldn't have the power to set our own schedules or even know when the best times to sleep or work would be. In earlier times, the power to predict the future was just as important. And that future was laid out in the stars. If you could know where the planet Venus would be 5 months in the future, that meant power. And if you predicted it incorrectly, that was even worse.
To understand the importance of telescopes, let's take a journey back in time to the early 17th century. At that time, the ruling view of the universe was the geocentric model articulated by Ptolemy and Aristotle before him. From this point of view, the sun, the moon, the planets, and the stars all orbited Earth in perfect spheres. This was the "onion" universe: the earth was at the center; the moon orbited in the sphere closest to the earth (like the layer of onion closest the center); Mercury and Venus orbited the earth just past the moon, each in their own layer; the sun was in the next layer out; followed by Mars; Jupiter; Saturn; and then the stars were the outside layer, all being part of one sphere that encircled all other spheres of orbit. In this model, the movement of celestial bodies was perfect and circular.
There was a bit of problem with this model; as all keen sky observers know, the planets don't follow a straight path in a single direction across the sky; occasionally, they seem to go backward in their path and then forward again, making a loop. How could this be explained in a model of spheres? The idea of epicycles sprung forth. Epicycles were orbits within orbits; that is to say, a planet like Mars would be moving in its own circular path while circling Earth.
This model of the universe was mostly accurate and allowed early astronomers to predict the positions of the planets más o menos (more or less, as we say in Spanish). Since the Catholic Church was one of the great powers of the day, The Church made sure that this perfect model was the one that people understood. God put Earth at the center of the universe (and by extension, man), and all other celestial bodies orbited in their perfect spheres. The Church could predict the future through this model of the universe and that gave The Church power.
Stay tuned for Part 2 of our telescope talk!
I'm going to answer that question in three parts, each of which will go live in three consecutive days. So consider this the first part, but by no means the entire story. Check back for more tomorrow and the day after.
The first part of this story centers around the power of astronomy. The power of astronomy is the power to predict the future. That is to say, we all have enough astronomical knowledge to know that the sun will rise and set each day. We can plan around this and it gives us power. If we didn't have that knowledge, we wouldn't have the power to set our own schedules or even know when the best times to sleep or work would be. In earlier times, the power to predict the future was just as important. And that future was laid out in the stars. If you could know where the planet Venus would be 5 months in the future, that meant power. And if you predicted it incorrectly, that was even worse.
To understand the importance of telescopes, let's take a journey back in time to the early 17th century. At that time, the ruling view of the universe was the geocentric model articulated by Ptolemy and Aristotle before him. From this point of view, the sun, the moon, the planets, and the stars all orbited Earth in perfect spheres. This was the "onion" universe: the earth was at the center; the moon orbited in the sphere closest to the earth (like the layer of onion closest the center); Mercury and Venus orbited the earth just past the moon, each in their own layer; the sun was in the next layer out; followed by Mars; Jupiter; Saturn; and then the stars were the outside layer, all being part of one sphere that encircled all other spheres of orbit. In this model, the movement of celestial bodies was perfect and circular.
There was a bit of problem with this model; as all keen sky observers know, the planets don't follow a straight path in a single direction across the sky; occasionally, they seem to go backward in their path and then forward again, making a loop. How could this be explained in a model of spheres? The idea of epicycles sprung forth. Epicycles were orbits within orbits; that is to say, a planet like Mars would be moving in its own circular path while circling Earth.
This model of the universe was mostly accurate and allowed early astronomers to predict the positions of the planets más o menos (more or less, as we say in Spanish). Since the Catholic Church was one of the great powers of the day, The Church made sure that this perfect model was the one that people understood. God put Earth at the center of the universe (and by extension, man), and all other celestial bodies orbited in their perfect spheres. The Church could predict the future through this model of the universe and that gave The Church power.Stay tuned for Part 2 of our telescope talk!
Thursday, January 15, 2009
Methane on Mars
Maybe Marvin the Martian is a cow.
NASA held a press conference today to announce that data from orbiting spacecraft picked shows plumes of methane on Mars. Not just a singular event, but various plume events over the last 5 years.
Before you go and get all ALH 84001-style excited about life on Mars, please remember that methane can be produced both biologically and geologically. For example, both bovine digestive processes and volcanic processes create methane on Earth. No one is sure where the methane on Mars is coming from. However, the fact that plumes have been seen over this extended period of time leads planetary geologists to think there is some sort of active process on Mars they had not considered before.
So the long and the short of the story is that there is no direct evidence of life on Mars, no matter what the crazies tell you. Instead, just another answer that just leads to more questions. Oh, how I love science!
Follow this link to a video from NASA about these results.
NASA held a press conference today to announce that data from orbiting spacecraft picked shows plumes of methane on Mars. Not just a singular event, but various plume events over the last 5 years.
Before you go and get all ALH 84001-style excited about life on Mars, please remember that methane can be produced both biologically and geologically. For example, both bovine digestive processes and volcanic processes create methane on Earth. No one is sure where the methane on Mars is coming from. However, the fact that plumes have been seen over this extended period of time leads planetary geologists to think there is some sort of active process on Mars they had not considered before.
So the long and the short of the story is that there is no direct evidence of life on Mars, no matter what the crazies tell you. Instead, just another answer that just leads to more questions. Oh, how I love science!
Follow this link to a video from NASA about these results.
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