Comet Lovejoy managed to survive its pass around the Sun - a mere 140,000 kilometers above the Sun's surface - and has reappeared on the other side! Despite the million-degree temperatures of the solar corona, this comet must have been robust enough to have avoided completely melting, although it now seems to lack a tail for the moment. This lack of a tail may be the result of the rapid orbital speed as it was "slung" around the Sun, being basically ripped away from its tail due to its increased velocity. It may also be the case that the Sun's heat melted away much of the ice that was exposed at its approach and there is now a significantly less amount of debris being streamed out behind it - lost in the glare of the Sun and the glowing comet head. We'll see if a tail reappears in the coming hours. For now, check out the videos and images posted by the SOHO space observatory:
SOHO Pick of the Week
Friday, December 16, 2011
Thursday, December 15, 2011
A comet's final day
While we can't see it from Oneonta today because of the clouds, comet C/2011 W3 (Lovejoy) is putting on a remarkable, unexpected show. Discovered last month as a large fragment of a comet that broke up, its orbit is taking it on what appears to be a suicide mission, plunging it deep into the Sun's atmosphere. This close approach will likely lead to the demise of the comet.
Comets are visitors from the outer regions of the solar system and are comprised of mostly ice and dust. Ranging in size from about 100 meters to nearly 50 kilometers, these objects are often referred to as "dirty snowballs." As it approaches the Sun, a comet's surface begins to vaporize, releasing a trail of dust and gas that streams out behind it as it flies through space. Often there exist two such tails, one of dust which basically follows the orbital trajectory traced out by the comet's motion, and another consisting of ionic gas which is pushed radially outward away from the Sun by the solar wind.
As Comet Lovejoy approaches the Sun, its vaporization causes it to grow brighter over time. Current predictions are that it may grow bright enough to see with the naked eye just after sunset today, provided that you have a clear view of the horizon. But look fast! If you miss it today, it'll be gone tomorrow.
For a consistently updated (often hourly) description as the situation changes, follow this blog here: SOHO and STEREO Sungrazing Comets.
Comets are visitors from the outer regions of the solar system and are comprised of mostly ice and dust. Ranging in size from about 100 meters to nearly 50 kilometers, these objects are often referred to as "dirty snowballs." As it approaches the Sun, a comet's surface begins to vaporize, releasing a trail of dust and gas that streams out behind it as it flies through space. Often there exist two such tails, one of dust which basically follows the orbital trajectory traced out by the comet's motion, and another consisting of ionic gas which is pushed radially outward away from the Sun by the solar wind.
As Comet Lovejoy approaches the Sun, its vaporization causes it to grow brighter over time. Current predictions are that it may grow bright enough to see with the naked eye just after sunset today, provided that you have a clear view of the horizon. But look fast! If you miss it today, it'll be gone tomorrow.
For a consistently updated (often hourly) description as the situation changes, follow this blog here: SOHO and STEREO Sungrazing Comets.
Friday, December 9, 2011
Planets galore!
Ah, the end of the semester. Students are frantically studying for finals, and professors are frantically grading and wrapping everything up. These sorts of thing have caused me a delay in posting. However, for the moment I seem to be caught up.
We got snow here a couple nights ago, which means I now need to be thinking of a few things up at the observatory: shoveling a walking path to the dome from the road, anticipating a frozen dome on a clear night, and getting snow tires for the drive up to College Camp. Snowy winter months can often have the clearest nights with the best seeing (little heat circulation means very stable air - limited twinkling). But those nights are often the coldest, which makes for somewhat unpleasant conditions. Nevertheless, let's get those telescopes or binoculars out and see what's visible!
On Saturday, December 10th the full Moon will pass through the Earth's ruddy shadow, resulting what is known as a total lunar eclipse. Anyone witnessing this event will see the Moon slowly begin to disappear, as if a bite was being taken out of it, until it is fully within the Earth's shadow - at which point, it will appear a rusty reddish-orange color. This view can be shocking to anyone who doesn't see it coming. Unfortunately for us Oneonta viewers, we won't see it at all.
If you keep your eyes to the night sky, you may eventually notice that not all points of light are stationary. Some move across the sky at fairly rapid rates! If they're not blinking (which would mean they're airplanes) then you can be fairly certain they're actually orbiting objects - either satellites or space junk. Russia just deposited a large piece of space junk into low Earth orbit in the form of a failed spacecraft that was supposed to travel to Mars to sample the surface material of its moon Phobos. Since this spacecraft failed to leave Earth's orbit, it is now expected to plunge into our atmosphere sometime in mid-January. While it isn't unusual for space junk to fall out of the sky, these things typically burn up before they hit the ground. However, there are some notable examples within the last few months (e.g. the ROSAT X-ray telescope and NASA's Upper Atmosphere Research Satellite) of objects so robust that some parts actually make it to the Earth's surface. This Russian craft, called Phobos-Grunt, will likely join that club, though it isn't yet known precisely where its debris may land. For now, you can see it, and many other orbiting satellites, as they pass overhead. Check out Spaceweather.com's Satellite Tracker for information on when certain satellites will pass overhead and where to look.
Venus is easily visible now after sunset as a bright point of light above the orange glow on the southwestern horizon. At the same time, Jupiter is also easily visible toward the east. For those who get up before the sun rises (or who stay up that late!) Saturn is visible rising in the east before the sun. Finally, Mars is also visible after midnight. You can find it by starting at Betelgeuse (the orange-ish star in the constellation of Orion), drawing a line through Procyon (which is due east) and continuing on until you reach another reddish light source in the sky, which is Mars. It's becoming a busy time for planets in our sky, and it will only get better as Mars and Saturn trek more and more into the earlier parts of the night over the coming months.
We got snow here a couple nights ago, which means I now need to be thinking of a few things up at the observatory: shoveling a walking path to the dome from the road, anticipating a frozen dome on a clear night, and getting snow tires for the drive up to College Camp. Snowy winter months can often have the clearest nights with the best seeing (little heat circulation means very stable air - limited twinkling). But those nights are often the coldest, which makes for somewhat unpleasant conditions. Nevertheless, let's get those telescopes or binoculars out and see what's visible!
On Saturday, December 10th the full Moon will pass through the Earth's ruddy shadow, resulting what is known as a total lunar eclipse. Anyone witnessing this event will see the Moon slowly begin to disappear, as if a bite was being taken out of it, until it is fully within the Earth's shadow - at which point, it will appear a rusty reddish-orange color. This view can be shocking to anyone who doesn't see it coming. Unfortunately for us Oneonta viewers, we won't see it at all.
If you keep your eyes to the night sky, you may eventually notice that not all points of light are stationary. Some move across the sky at fairly rapid rates! If they're not blinking (which would mean they're airplanes) then you can be fairly certain they're actually orbiting objects - either satellites or space junk. Russia just deposited a large piece of space junk into low Earth orbit in the form of a failed spacecraft that was supposed to travel to Mars to sample the surface material of its moon Phobos. Since this spacecraft failed to leave Earth's orbit, it is now expected to plunge into our atmosphere sometime in mid-January. While it isn't unusual for space junk to fall out of the sky, these things typically burn up before they hit the ground. However, there are some notable examples within the last few months (e.g. the ROSAT X-ray telescope and NASA's Upper Atmosphere Research Satellite) of objects so robust that some parts actually make it to the Earth's surface. This Russian craft, called Phobos-Grunt, will likely join that club, though it isn't yet known precisely where its debris may land. For now, you can see it, and many other orbiting satellites, as they pass overhead. Check out Spaceweather.com's Satellite Tracker for information on when certain satellites will pass overhead and where to look.
Venus is easily visible now after sunset as a bright point of light above the orange glow on the southwestern horizon. At the same time, Jupiter is also easily visible toward the east. For those who get up before the sun rises (or who stay up that late!) Saturn is visible rising in the east before the sun. Finally, Mars is also visible after midnight. You can find it by starting at Betelgeuse (the orange-ish star in the constellation of Orion), drawing a line through Procyon (which is due east) and continuing on until you reach another reddish light source in the sky, which is Mars. It's becoming a busy time for planets in our sky, and it will only get better as Mars and Saturn trek more and more into the earlier parts of the night over the coming months.
Tuesday, November 29, 2011
Cloudy nights
Oneonta has had some cloudy weather lately, and even during my Thanksgiving trip back home to Michigan the weather was still cloudy. The Sun had a strong outburst of energy and particles into space, called a coronal mass ejection (CME) that arrived at Earth on November 28th. This storm sparked northern lights for viewers in the northern latitudes of Canada, Norway, Finland, etc. Even some people in Wisconsin and Minnesota reported seeing the aurora. Here in New York, we were clouded out.
Cloudy nights make me think about what I'd love to be doing, were the skies clear. Venus and Mercury are both visible after sunset these days, and Jupiter is visible for most of the night. However, the waxing crescent Moon, only 4 days past its new phase, is always fun to look at with binoculars or a telescope. Viewing the Moon along the line separating day and night, called the terminator, provides an excellent view of the surface terrain. Craters come to life through moderate magnification as the shadows stretch out along the landscape. Even better, and unlike most other astronomical targets, the view changes from day to day as the Moon orbits the Earth, resulting in movement of the terminator across the face of the Moon and allowing new craters and mountains to pop out of the darkness.
Thursday night in Oneonta is supposed to be clear, according to the Weather Channel. This may provide for a great opportunity to familiarize yourself with our planet's nearest neighbor. If you're using a telescope, pick a feature and bump up the magnification to take in even greater details. You might even try your hand at sketching what you see in the eyepiece. For some tips, check out how Galileo did it:
We often take the Moon for granted (or, as professional astronomers, we often think of it as a nuisance), so grab some binoculars or a small telescope and have fun exploring!
Cloudy nights make me think about what I'd love to be doing, were the skies clear. Venus and Mercury are both visible after sunset these days, and Jupiter is visible for most of the night. However, the waxing crescent Moon, only 4 days past its new phase, is always fun to look at with binoculars or a telescope. Viewing the Moon along the line separating day and night, called the terminator, provides an excellent view of the surface terrain. Craters come to life through moderate magnification as the shadows stretch out along the landscape. Even better, and unlike most other astronomical targets, the view changes from day to day as the Moon orbits the Earth, resulting in movement of the terminator across the face of the Moon and allowing new craters and mountains to pop out of the darkness.
We often take the Moon for granted (or, as professional astronomers, we often think of it as a nuisance), so grab some binoculars or a small telescope and have fun exploring!
Wednesday, November 16, 2011
Leonid Meteor Shower
As the Earth moves around the Sun in its orbit, we periodically pass through debris trails left behind by comets. As these small bits of dust (many of them only slightly larger than microscopic) get swept up by our planet like a Swiffer sweeper, the particles plummet through our atmosphere toward the ground. During this plunge, they compress the air in front of them, causing it to heat up (and therefore heat up the particle as well) and the result is a glowing streak (a meteor) flying through the air. When we pass through a comet trail and experience a large number of meteors, we call this a meteor shower.
This Thursday night / Friday morning, we are set to experience the peak of the Leonid meteor shower, associated with the comet Tempel-Tuttle. While the performance of this meteor shower from year to year is somewhat inconsistent, the Leonid meteor shower is typically one of the better showers of the year. Predictions of the number of meteors per hour can vary, but seeing at least one meteor per minute is not uncommon for this shower. The particles are moving extremely fast, at roughly 72 km/s, so you'll have to have a sharp eye out for those streaks as they light up the sky!
The shower is called the Leonid meteor shower because the meteors appear to radiate from the constellation Leo. Meteors are best viewed after midnight, as the viewer is on the leading side of the Earth in its rotation (think of a car's front windshield catching more rain drops than the rear windshield), but this year the bright third-quarter moon may wash out all but the brightest meteors. However, while the meteor showers are typically best viewed after midnight, meteors can be seen all night long and so it's worth stepping outside for 5-10 minutes in the evening before the moon rises to see if you can spot them. Face east, and look up.
Happy viewing!
This Thursday night / Friday morning, we are set to experience the peak of the Leonid meteor shower, associated with the comet Tempel-Tuttle. While the performance of this meteor shower from year to year is somewhat inconsistent, the Leonid meteor shower is typically one of the better showers of the year. Predictions of the number of meteors per hour can vary, but seeing at least one meteor per minute is not uncommon for this shower. The particles are moving extremely fast, at roughly 72 km/s, so you'll have to have a sharp eye out for those streaks as they light up the sky!
The shower is called the Leonid meteor shower because the meteors appear to radiate from the constellation Leo. Meteors are best viewed after midnight, as the viewer is on the leading side of the Earth in its rotation (think of a car's front windshield catching more rain drops than the rear windshield), but this year the bright third-quarter moon may wash out all but the brightest meteors. However, while the meteor showers are typically best viewed after midnight, meteors can be seen all night long and so it's worth stepping outside for 5-10 minutes in the evening before the moon rises to see if you can spot them. Face east, and look up.
Happy viewing!
Saturday, November 12, 2011
Venus is becoming visible
Venus is becoming more easily visible after sunset. The image above, taken from my apartment's balcony, shows this brilliant planet glittering through the tree limbs. As our sister planet continues to emerge from behind the Sun, it will become increasingly bright and more easily seen. Its elongation (angular separation) from the Sun will increase for several weeks, shining brightly in the post-sunset evening. You can use this Solar System Simulator from NASA to see what relative positions the planets in our solar system are in to cause the changes in Venus' position from night to night.
Wednesday, November 9, 2011
Asteroid Flyover
Headlines were in abundance early this week about the flyover of the asteroid 2005 YU55, whose orbital path around the Sun took it inside the orbit of the Moon on Tuesday night (eg. see this article from Yahoo! News). This asteroid made a close pass by the Earth, being just 201,000 miles away. The asteroid was in no danger of hitting Earth, which NASA officials were quick to point out, but the fact that a 400-meter asteroid might come so close was enough to remind us all that a bad day is just one asteroid away. Having the opportunity to see an asteroid (or anything that's not man-made) move noticeably through the sky was enough to send me up to the observatory for a look.
I went up with two students, and a few folks from the public showed up as well. Using the 16" telescope we were able to identify the asteroid and track its motion across the sky for a couple of hours. Looking through the eyepiece, which had a field of view of about 1/2 a degree, the asteroid was moving quickly. Its motion with respect to the stationary stars was imperceptible until you saw it, at which point you couldn't NOT notice it moving. While it was not particularly bright, everyone present was able to see it. I was quite surprised at how rapidly it moved. I'm accustomed to seeing asteroids on CCD images make small streaks against the stars as they move across the CCD field of view, but seeing an object moving this rapidly (at its fastest it was moving at about 16 Moon-widths per hour) made quite an impression.
We attempted to take some images of it but experienced some trouble with the equipment. The CCD camera we were using was not one I had used before and we had difficulty identifying the field of view on the computer screen - it was smaller than the eyepiece. While we were unable to get any images of the asteroid, some had better luck. You can bet I'll be better prepared the next time something large flies by! By then perhaps we'll have the 1-meter telescope up and running for some real viewing.
For those who are privileged to see a beautiful sunset on the western horizon, keep your eyes peeled in the fading orange for a bright point of light above where the sun fell below the horizon. This bright point of light is Venus, our sister planet finally reappearing from behind the Sun. The eagle-eyed viewer might even see Mercury just next to Venus, although Mercury's brightness is quite a bit dimmer. For the next week, both planets move away from the Sun, being visible for longer and longer after sunset. After November 14, Mercury begins to move back toward the Sun, while Venus continues on in its wider orbit. The next time you have a clear view of the sunset, take a peek and see if you can spot both planets!
I went up with two students, and a few folks from the public showed up as well. Using the 16" telescope we were able to identify the asteroid and track its motion across the sky for a couple of hours. Looking through the eyepiece, which had a field of view of about 1/2 a degree, the asteroid was moving quickly. Its motion with respect to the stationary stars was imperceptible until you saw it, at which point you couldn't NOT notice it moving. While it was not particularly bright, everyone present was able to see it. I was quite surprised at how rapidly it moved. I'm accustomed to seeing asteroids on CCD images make small streaks against the stars as they move across the CCD field of view, but seeing an object moving this rapidly (at its fastest it was moving at about 16 Moon-widths per hour) made quite an impression.
We attempted to take some images of it but experienced some trouble with the equipment. The CCD camera we were using was not one I had used before and we had difficulty identifying the field of view on the computer screen - it was smaller than the eyepiece. While we were unable to get any images of the asteroid, some had better luck. You can bet I'll be better prepared the next time something large flies by! By then perhaps we'll have the 1-meter telescope up and running for some real viewing.
For those who are privileged to see a beautiful sunset on the western horizon, keep your eyes peeled in the fading orange for a bright point of light above where the sun fell below the horizon. This bright point of light is Venus, our sister planet finally reappearing from behind the Sun. The eagle-eyed viewer might even see Mercury just next to Venus, although Mercury's brightness is quite a bit dimmer. For the next week, both planets move away from the Sun, being visible for longer and longer after sunset. After November 14, Mercury begins to move back toward the Sun, while Venus continues on in its wider orbit. The next time you have a clear view of the sunset, take a peek and see if you can spot both planets!
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