It's back!
Fraser Cain from Universe Today has selected another fine host for this week's Carnival of Space.
Carnival of Space #68 is hosted by Adam Crowl at Crowlspace. Once there, I started reading some of his previous blogs. Great, just what I need, another fascinating blog to keep track of each day!
This week, Phil Plait, the Bad Astronomer, answers why we don't just use telescopes to prove the lunar landings happened. I don't know if the people who keep bringing up this moon landing hoax nonsense are gonna want to hear that even Hubble could barely make out a football stadium on the moon. But Phil does an excellent job of explaining it to the more rational among us.
There is an entry from Dr. Ian O'Neill, whose blog Astroengine is linked here as one of my favorite stops on the blog tour each morning. Another of my first cup o' Joe favorites, Ray Villard, Cosmic Ray, covers the ongoing debate over Pluto. He recently attended the 'great debate' and has a number of great blogs on it. A new addition to my blog favorites, Emily Lakdawalla, puts out a great blog at the Planetary Society Weblog. I read her entry into the Carnival, also about naming planets, a few days ago, and it's very good.
I even managed to get an entry in the Carnival this week. I crawled out from under the mountain of grant research and writing long enough to write up a piece on computer modeling of planetary formation. I confess, I found the story while investigating National Science Foundation grants, but it's nice to be able to mix a little business with pleasure and spread the word when I find new and exciting research like this.
I've read nearly all the Carnival offerings already, and give it a 9.9 on the Simoscale. I would have given it a 10, but I learned there is no such thing any more while watching the Olympics last week.
So what are you still doing here? Get on over to the Carnival -and have a cotton candy on me.
Planets--Good News, Bad News
One fascinating new development in exoplanet research is that we can now create complex models of planetary system evolution using supercomputers. Edward Thommes, Soko Matsumura and Frederic Rasio published their findings, "Gas Disks to Gas Giants: Simulating the Birth of Planetary Systems," in the August 8, issue of Science magazine. The computer simulations were done using a cluster of supercomputers operated by Northwestern's Theoretical Astrophysics Group. Some of what they discovered is a little surprising.
We think we have a pretty good handle on how planetary systems develop, and we have assumed all along that many of them would resemble the solar system. But, with the list of known extra-solar planets now approaching 300, we haven't really found systems like ours. Instead, we've discovered some surprising forms of planets orbiting stars in ways we didn't predict, like 'hot Jupiters', gas giants orbiting in close proximity to their stars.
Is what we are finding what is really out there, or is it merely a selection effect caused by the technology and methods we use to detect extra-solar planets? These are some of the questions the computer simulations might help answer.
Image copyright Edward Thommes, 2008, used with permission.
Apparently, earth-like planets are fairly common, or as Edward Thommes says in the NSF interview, "they're almost like weeds, they'll sprout up under almost any conditions." It's our system's gas giants, Jupiter and Saturn, that seem to be the exception to the rule. Most are not gentle giants, peacefully lumbering around their stars in distant, decades long orbits. Their research suggests that as we look for more planets farther away from their stars we are likely to find Jupiter and Saturn type giants, but these systems may also contain gas giants orbiting as close as Mercury orbits our sun.
It's been argued that having a large planet outside the orbit of Earth has protected us from comets and asteroids hurtling toward the inner solar system from the depths of space. Does having a big brother gas giant orbiting further out help protect smaller planets from bombardment by comets and other bodies, enhancing the chances for life to take hold and thrive? Maybe so, but as Ed points out, "it could also be argued that Jupiter put those comets there (in the Kuiper belt) in the first place."
This leads to some other interesting questions. What happens to the rocky planets in the habitable zone as gas giants migrate in towards their star? Can life exist in systems that only contain small rocky planets and no gas giants at all?
Understanding the connection between the make-up of the planetary system and the habitability of the planets in it is still a ways off. But as computing power increases we will be able to model more of the weird systems we may encounter in our search. As this study shows, our system may actually be the 'weird' one in the bunch.
The good news is, there are plenty of systems out there and we are finding them. The bad news is, if we were expecting to find more solar type planetary systems, earth-like environments, and ultimately extra-terrestrial life, the odds don't look as good today as they did before.
We think we have a pretty good handle on how planetary systems develop, and we have assumed all along that many of them would resemble the solar system. But, with the list of known extra-solar planets now approaching 300, we haven't really found systems like ours. Instead, we've discovered some surprising forms of planets orbiting stars in ways we didn't predict, like 'hot Jupiters', gas giants orbiting in close proximity to their stars.
Is what we are finding what is really out there, or is it merely a selection effect caused by the technology and methods we use to detect extra-solar planets? These are some of the questions the computer simulations might help answer.
"We now know that these other planetary systems don't look like the solar system at all," said Frederic A. Rasio, senior author of the Science paper. "We now better understand the process of planet formation and can explain the properties of the strange exoplanets we've observed. We also know that the solar system is special and understand at some level what makes it special."
What they found is that our solar system represents the rare cases, where gas giants form, but do not migrate to the inner planetary system, and the final orbits of the planets in the system are fairly circular and stable. In many simulations, lots of gas giants formed in chaotic environments with collisions and eccentric orbits. In other simulations, plenty of smaller rocky planets formed, but hardly any gas giants materialized out of the proto-planetary disk. Only under specific, unique conditions do planetary systems like ours evolve.
Image copyright Edward Thommes, 2008, used with permission.Apparently, earth-like planets are fairly common, or as Edward Thommes says in the NSF interview, "they're almost like weeds, they'll sprout up under almost any conditions." It's our system's gas giants, Jupiter and Saturn, that seem to be the exception to the rule. Most are not gentle giants, peacefully lumbering around their stars in distant, decades long orbits. Their research suggests that as we look for more planets farther away from their stars we are likely to find Jupiter and Saturn type giants, but these systems may also contain gas giants orbiting as close as Mercury orbits our sun.
It's been argued that having a large planet outside the orbit of Earth has protected us from comets and asteroids hurtling toward the inner solar system from the depths of space. Does having a big brother gas giant orbiting further out help protect smaller planets from bombardment by comets and other bodies, enhancing the chances for life to take hold and thrive? Maybe so, but as Ed points out, "it could also be argued that Jupiter put those comets there (in the Kuiper belt) in the first place."
This leads to some other interesting questions. What happens to the rocky planets in the habitable zone as gas giants migrate in towards their star? Can life exist in systems that only contain small rocky planets and no gas giants at all?
Understanding the connection between the make-up of the planetary system and the habitability of the planets in it is still a ways off. But as computing power increases we will be able to model more of the weird systems we may encounter in our search. As this study shows, our system may actually be the 'weird' one in the bunch.
The good news is, there are plenty of systems out there and we are finding them. The bad news is, if we were expecting to find more solar type planetary systems, earth-like environments, and ultimately extra-terrestrial life, the odds don't look as good today as they did before.
The Great Planet Debate
It may not be the Scopes Monkey Trial, but this one should be good. A public debate between Dr. Mark Sykes of the Planetary Science Institute and Dr. Neil deGrasse Tyson of the American Museum of Natural History will start at 4:30 pm EDT. The whole thing will be streamed to the web live as it happens. You needed to pre-register to view the public debate live, but if you miss out today, the debate will be posted to the net later for viewing.
This is all part of a three day conference on what we know about planets and, of course, how to define them. A hot topic ever since the IAU made the poor decision to redefine something we all knew the meaning of.
An Amazing Deal!
I checked my email early this morning, as always, and guess what I found? Amazon dot com is offering me a fantastic deal!
"Watch the Perseid Meteor Shower With a Discounted Celestron Telescope!"
The advertisement goes on to tell about how fantastic and reliable this meteor shower is each year, and how in honor of this event I can now purchase telescopes to watch the whole thing at special prices. I even got a special code to enter to get this bargain basement pricing.
Of course, the problem is, you can't watch a meteor shower with a telescope. The field of view, the portion of the sky you can see, is way too small to see meteors. Meteors go streaking across the sky in all kinds of random directions, even though shower members emanate from a particular point in the sky, the radiant. They are gone in the blink of an eye, mostly. There is no time to react and point a telescope.
This year, the Perseid shower peaks on the morning of August 12th. Get up around midnight and go outside. The best thing to do is lay on your back in a lawn chair and just look up with your unaided eyes. The Moon will be setting by then, and you should be able to see at least one or two every minute.
Maybe Amazon has a special on lawn chairs for astronomers.
"Watch the Perseid Meteor Shower With a Discounted Celestron Telescope!"
The advertisement goes on to tell about how fantastic and reliable this meteor shower is each year, and how in honor of this event I can now purchase telescopes to watch the whole thing at special prices. I even got a special code to enter to get this bargain basement pricing.
Of course, the problem is, you can't watch a meteor shower with a telescope. The field of view, the portion of the sky you can see, is way too small to see meteors. Meteors go streaking across the sky in all kinds of random directions, even though shower members emanate from a particular point in the sky, the radiant. They are gone in the blink of an eye, mostly. There is no time to react and point a telescope.
This year, the Perseid shower peaks on the morning of August 12th. Get up around midnight and go outside. The best thing to do is lay on your back in a lawn chair and just look up with your unaided eyes. The Moon will be setting by then, and you should be able to see at least one or two every minute.
Maybe Amazon has a special on lawn chairs for astronomers.
Carnival of Space #65
Hey, if you're out surfing the Net today you might want to catch some 21st Century Waves
That's where you'll find this weeks Carnival of Space #65.
That's where you'll find this weeks Carnival of Space #65.
Hubble Sees Toast
Earlier in the week, a question was raised in one of the astronomy discussion forums I monitor.
"Can large ground-based telescopes or the Hubble Space Telescope resolve stars in such distant galaxies that those stars are likely to not exist anymore?"
This is actually several questions lined up in a deceptively simple package. How far away (or back in time) can HST or any large telescope image individual stars in distant galaxies? What kind of stars would we be able to see? In the course of normal stellar evolution, would these stars live, evolve and die in the time it has taken their light to reach us from the galaxy they reside in?
A few people chirped in with the suggestion that supernovae can be seen at great distances, but supernovae is kind of a cheat answer to the question, because we are seeing the results of a catastrophic explosion, not really an individual star. True, we can see supernovae in galaxies billions of light years distant, and obviously they no longer exist in their nascent form since they went supernovae. But, I don't think that is what was being asked.
Cepheid variables have been used to measure distances to galaxies by HST and ground based telescopes. These tend to be yellow giant and super giant stars 40-180 times the radius of the Sun, and thousands of times more luminous, so we can see them from millions of light years away. Before HST we were able to measure Cepheid variables in galaxies out to about 12 million light years. But what about now?
Pamela L. Gay, PhD astronomer at SIUE said, "I'm not sure with it's newest instruments, but the Hubble Key Project observed Cepheids, and they went out as far as 20 million parsecs."
20 million parsecs is about 65 million light years. So Hubble can measure individual Cepheids at least that far.
Above, are 1999 images of a Cepheid variable in M100 at a distance of about 50 million light years. You can see it at minimum, in between and at maximum light.
Luminous Blue Variables (LBVs) are hypergiant stars with masses approaching the theoretical limit for stars (150 solar+). They can shine across vast cosmic distances.
These are short lived stars as stars go, because they are so massive. The more massive a star is, the brighter it will shine, but also the faster it will burn itself out. Faint red dwarfs may live longer then the Universe is old, slowly and miserly burning their interior elements for tens of billions of years. LBVs may only survive a few million years.
Doug Welch, PhD in Physics and Astronomy at McMaster University said, "We can see such stars in the Coma cluster of galaxies which is about a third of a billion light years away, so I'd say the limit is about 1 billion light years with existing technology."
1 billion light years! Certainly, any LBVs we can see a billion light years away no longer exist today. The further back in time we look, the higher the probability the individual stars we CAN see in far off galaxies are no longer there, since they tend to be the "live fast, die young" animals in the stellar zoo.
Al Holm, PhD, Branch Chief for Data Processing and Archival Services at the Space Telescope Science Institute in Baltimore, confirmed what I had learned. Al wrote, "By 1999, Cepheids had been observed to a distance of 65 million light-years. Our instrumentation has improved since then, but I'm not sure what has been done to extend the distance scale to more distant galaxies.
Looking at the question in another way, Tom Brown recently used the ACS to take deep exposures of stars in the halo of M31. His plots show stars down to about 31.5 mag. In theory, at that apparent magnitude you might be able to see Eta Carina in its bright phase out to a couple billion light-years. The problem would be blending of images at that distance. To be seen, the star would have to be well away from any neighbors, but LBVs are young and embedded in clusters so they would fail that criterion. "
We've come full circle in our investigation at this point. Eta Carina is expected to go supernova in a million years or less. So not only can we image supernovae in distant galaxies, we may be able to see LBV supernovae progenitors like Eta Car at great distances!
No matter what instrument is used, the star needs to be in an uncrowded region of the galaxy in order to be imaged cleanly, and it can't be embedded in nebulosity or be a member of a cluster.
The answer then is, given the best possible conditions, with Hubble's modern equipment, we can see individual massive bright stars out to a billion light years or more. Since these massive stars tend to live for millions of years, not billions of years, massive stars visible at great distances have probably lived and died in the time it took their light to get here from there. Or, as Doug said, "ANY stars bright enough to be seen at 100's of millions of years distance are "currently" toast."
"Can large ground-based telescopes or the Hubble Space Telescope resolve stars in such distant galaxies that those stars are likely to not exist anymore?"
This is actually several questions lined up in a deceptively simple package. How far away (or back in time) can HST or any large telescope image individual stars in distant galaxies? What kind of stars would we be able to see? In the course of normal stellar evolution, would these stars live, evolve and die in the time it has taken their light to reach us from the galaxy they reside in?
A few people chirped in with the suggestion that supernovae can be seen at great distances, but supernovae is kind of a cheat answer to the question, because we are seeing the results of a catastrophic explosion, not really an individual star. True, we can see supernovae in galaxies billions of light years distant, and obviously they no longer exist in their nascent form since they went supernovae. But, I don't think that is what was being asked.
Cepheid variables have been used to measure distances to galaxies by HST and ground based telescopes. These tend to be yellow giant and super giant stars 40-180 times the radius of the Sun, and thousands of times more luminous, so we can see them from millions of light years away. Before HST we were able to measure Cepheid variables in galaxies out to about 12 million light years. But what about now?
Pamela L. Gay, PhD astronomer at SIUE said, "I'm not sure with it's newest instruments, but the Hubble Key Project observed Cepheids, and they went out as far as 20 million parsecs."
20 million parsecs is about 65 million light years. So Hubble can measure individual Cepheids at least that far.Above, are 1999 images of a Cepheid variable in M100 at a distance of about 50 million light years. You can see it at minimum, in between and at maximum light.
Luminous Blue Variables (LBVs) are hypergiant stars with masses approaching the theoretical limit for stars (150 solar+). They can shine across vast cosmic distances.
These are short lived stars as stars go, because they are so massive. The more massive a star is, the brighter it will shine, but also the faster it will burn itself out. Faint red dwarfs may live longer then the Universe is old, slowly and miserly burning their interior elements for tens of billions of years. LBVs may only survive a few million years.
Doug Welch, PhD in Physics and Astronomy at McMaster University said, "We can see such stars in the Coma cluster of galaxies which is about a third of a billion light years away, so I'd say the limit is about 1 billion light years with existing technology."
1 billion light years! Certainly, any LBVs we can see a billion light years away no longer exist today. The further back in time we look, the higher the probability the individual stars we CAN see in far off galaxies are no longer there, since they tend to be the "live fast, die young" animals in the stellar zoo.
Al Holm, PhD, Branch Chief for Data Processing and Archival Services at the Space Telescope Science Institute in Baltimore, confirmed what I had learned. Al wrote, "By 1999, Cepheids had been observed to a distance of 65 million light-years. Our instrumentation has improved since then, but I'm not sure what has been done to extend the distance scale to more distant galaxies.
Looking at the question in another way, Tom Brown recently used the ACS to take deep exposures of stars in the halo of M31. His plots show stars down to about 31.5 mag. In theory, at that apparent magnitude you might be able to see Eta Carina in its bright phase out to a couple billion light-years. The problem would be blending of images at that distance. To be seen, the star would have to be well away from any neighbors, but LBVs are young and embedded in clusters so they would fail that criterion. "
We've come full circle in our investigation at this point. Eta Carina is expected to go supernova in a million years or less. So not only can we image supernovae in distant galaxies, we may be able to see LBV supernovae progenitors like Eta Car at great distances!
No matter what instrument is used, the star needs to be in an uncrowded region of the galaxy in order to be imaged cleanly, and it can't be embedded in nebulosity or be a member of a cluster.
The answer then is, given the best possible conditions, with Hubble's modern equipment, we can see individual massive bright stars out to a billion light years or more. Since these massive stars tend to live for millions of years, not billions of years, massive stars visible at great distances have probably lived and died in the time it took their light to get here from there. Or, as Doug said, "ANY stars bright enough to be seen at 100's of millions of years distance are "currently" toast."
Like A Bad Penny
My friends and neighbors all know I usually don't look at planets. I study variable stars, and that's about all I have time for these days.
At least a couple times a summer, someone who has seen the observatory or knows me through someone who knows me asks, " So are you ready for the fantastic view of Mars this August? I hear it's the closest it's going to be in a hundred years, and will probably be as big as the full moon!"
Today, the guy who sprays my trees asked me. He was all excited. He told me he'd marked his calendar and everything. He was probably working up the nerve to ask if I'd show him Mars through one of the telescopes. People are always nervous about asking. Perhaps it's the welcome mat at the door of the dome that says, "Go Away!"
He seemed truly disappointed when I told him the email he got, full of useless mis-information was about four years too late. "Yea, we had a great star party that year in September. I had people with 20 inch telescopes showing everyone Mars. It was awesome."
We still needed telescopes to see it. Newsflash: Mars will never appear as large as the full moon to the unaided eye. It's too far away and too small! Through a very good telescope on an excellent night of seeing, with high magnification, your impression of Mars might be similar to your view of the Moon with the unaided eye. But that's where the comparison ends, really, trust me. This is what Mars has always looked like to me-
Then I had to explain to him that Mars isn't even visible this summer because it is too close to the Sun. It's lost in the glare of daytime somewhere between Leo and Virgo right now. We talked about the solar eclipse, phases of the Moon, motion of the planets and stars, and I invited him to the StarBQ in September. I think that makes us even for the free advice he gave me on how to save a prized specimen tree that had a split.
It will happen again. That stupid email keeps turning up each summer like a bad penny. But that's okay. Any time we can kill some bad astronomical perception and replace it with good information, that's a small step in a long journey we must take.
At least a couple times a summer, someone who has seen the observatory or knows me through someone who knows me asks, " So are you ready for the fantastic view of Mars this August? I hear it's the closest it's going to be in a hundred years, and will probably be as big as the full moon!"
Today, the guy who sprays my trees asked me. He was all excited. He told me he'd marked his calendar and everything. He was probably working up the nerve to ask if I'd show him Mars through one of the telescopes. People are always nervous about asking. Perhaps it's the welcome mat at the door of the dome that says, "Go Away!"
He seemed truly disappointed when I told him the email he got, full of useless mis-information was about four years too late. "Yea, we had a great star party that year in September. I had people with 20 inch telescopes showing everyone Mars. It was awesome."
We still needed telescopes to see it. Newsflash: Mars will never appear as large as the full moon to the unaided eye. It's too far away and too small! Through a very good telescope on an excellent night of seeing, with high magnification, your impression of Mars might be similar to your view of the Moon with the unaided eye. But that's where the comparison ends, really, trust me. This is what Mars has always looked like to me-
Then I had to explain to him that Mars isn't even visible this summer because it is too close to the Sun. It's lost in the glare of daytime somewhere between Leo and Virgo right now. We talked about the solar eclipse, phases of the Moon, motion of the planets and stars, and I invited him to the StarBQ in September. I think that makes us even for the free advice he gave me on how to save a prized specimen tree that had a split.It will happen again. That stupid email keeps turning up each summer like a bad penny. But that's okay. Any time we can kill some bad astronomical perception and replace it with good information, that's a small step in a long journey we must take.
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