Starship Asterisk*

by **neufer** » Fri Feb 18, 2011 10:33 pm

Click to play embedded YouTube video.

by **neufer** » Fri Feb 18, 2011 3:03 pm

: Click to view full size image

http://en.wikipedia.org/wiki/Deep_Impact_%28spacecraft%29 wrote:
<<Following its launch on January 12, 2005, the Deep Impact spacecraft traveled 429 million kilometers in 174 days to reach comet 9P/Tempel at a cruising speed of 28.6 km/s. Once the spacecraft reached the vicinity of the comet on July 3, 2005, it separated into two portions, a 370-kilogram copper-core "Smart Impactor" and a flyby probe.

The flyby spacecraft performed one of two divert maneuvers to avoid damage. A 14-minute burn was executed which slowed down the spacecraft. The impactor spacecraft used its thrusters to move into the path of the comet, impacting 24 hours later at a relative speed of 10.3 km/s. (The impactor executed three correction maneuvers in the final two hours before impact.) Scientists believed that the energy of the high-velocity collision would be sufficient to excavate a crater up to 100 m wide (larger than the bowl of the Roman Colosseum).

The impactor's payload, dubbed the "Cratering Mass", was 100% copper to reduce debris interfering with scientific measurements of the impact. Since copper was not expected to be found on a comet, scientists could eliminate copper from the spectrometer reading. Instead of using explosives, it was also cheaper to use copper as the payload.>>

by **Chris Peterson** » Fri Feb 18, 2011 2:48 pm

glaucoramalho wrote:I don't want to duel into that, but the flash light can't be like the same case as in the Moon, because the meteorites that crash into land are very more powerful than the spacecraft launcher, you may imagine that.

Actually, the impact in this case released quite a bit more energy than a typical lunar impact, such as occurs a few hundred times a year.

My question is: this comet is not really so active, but now he is in some of his most active zone, because he is closer to the Sun in its orbit. We just can see the corona and tail at a distance, like on this images:
http://asterisk.apod.com/vie ... 9&start=25. You can't see the nucleus here, just a big coma coma and a little tail.

But in the pictures of the Stardust, closer enough to see the nucleus and inside the coma region, you just can see the rock structure and four or five jets coming out off the contrary side of the Sun. This jets
have no energy enough to create hundreds and hundreds of coma or the tail. They are too faint, even if you have more.

This comet has a very tenuous coma because of its low activity. The jets seen in the recent image (when a lot of contrast stretching is applied) are certainly sufficient to explain the observed coma. They probably represent an outflow of material on the order of hundreds or thousands of kilograms per second, which is certainly enough to explain the observed coma.

I'm not sure what images you think are showing a large, dense coma or tails. These things are not present with this comet, even when it's at perihelion.

Where is the energy?

As previously noted, the Sun provides more than sufficient energy. Comets do not have an internal energy source, and none is required to completely explain their behavior.

by **rstevenson** » Fri Feb 18, 2011 2:03 pm

glaucoramalho wrote:... I don't want to duel into that, but the flash light can't be like the same case as in the Moon, because the meteorites that crash into land are very more powerful than the spacecraft launcher, you may imagine that.

Of course the impactor was only gently nudged away from the spacecraft, but the spacecraft itself was moving very fast, so the impactor was also moving very fast (about 10.2 m/s) and the energy of impact was very large.

Rob

by **glaucoramalho** » Fri Feb 18, 2011 1:43 pm

Chris Peterson wrote:
garry wrote:With the impactor fired from the satellite, there has never been a satisfactory explanation of the bright flash seen in the You Tube video. The impactor was an inert object, so there should only of been a hole and a lot of material thrown up. But a bright flash? The reason there was no crater and no debris thrown up was that he impactor vaporised before hitting the surface.......
There was a thermal flash associated with the energy released in the collision- 4.5 tons of TNT equivalent. These sorts of thermal flashes are seen on the Moon during meteor showers, where similar energies are involved. Immediately after the collision, there were tens of millions of kilograms of water and dust ejected, which were very bright compared with the surface brightness of the comet, which is what the exposures were optimized for.

I don't know why you say there was no crater and no debris... the debris cloud was photographed and analyzed spectroscopically, and the 150 meter crater is quite obvious in these latest images.

Why would you think the probe was vaporized before hitting? How do you think that could happen? I hope you don't think there are aliens living on the comet, shooting down probes?

I don't want to duel into that, but the flash light can't be like the same case as in the Moon, because the meteorites that crash into land are very more powerful than the spacecraft launcher, you may imagine that.

My question is: this comet is not really so active, but now he is in some of his most active zone, because he is closer to the Sun in its orbit. We just can see the corona and tail at a distance, like on this images:
http://asterisk.apod.com/vie ... 9&start=25. You can't see the nucleus here, just a big coma coma and a little tail.

But in the pictures of the Stardust, closer enough to see the nucleus and inside the coma region, you just can see the rock structure and four or five jets coming out off the contrary side of the Sun. This jets
have no energy enough to create hundreds and hundreds of coma or the tail. They are too faint, even if you have more.

Before this missions, I remember very well... the astronomers are convinced that they would see a lot of ice kind sheet around the nucleus and a powerful jet structures coming out of the nucleus,
and that would make sense for a so large corona and tails that comets shows. But this is not the reality, there are no kind of ice sheet around the nucleus, and the jets are... too boring to do anything.
This explanation don't fit anymore in my mind anyway, and I'm studding by myself about comets through NASA news since Beakman's World on 90's... don't make sense anymore. Where is the energy?

by **Chris Peterson** » Fri Feb 18, 2011 5:36 am

garry wrote:With the impactor fired from the satellite, there has never been a satisfactory explanation of the bright flash seen in the You Tube video. The impactor was an inert object, so there should only of been a hole and a lot of material thrown up. But a bright flash? The reason there was no crater and no debris thrown up was that he impactor vaporised before hitting the surface.......

There was a thermal flash associated with the energy released in the collision- 4.5 tons of TNT equivalent. These sorts of thermal flashes are seen on the Moon during meteor showers, where similar energies are involved. Immediately after the collision, there were tens of millions of kilograms of water and dust ejected, which were very bright compared with the surface brightness of the comet, which is what the exposures were optimized for.

I don't know why you say there was no crater and no debris... the debris cloud was photographed and analyzed spectroscopically, and the 150 meter crater is quite obvious in these latest images.

Why would you think the probe was vaporized before hitting? How do you think that could happen? I hope you don't think there are aliens living on the comet, shooting down probes?

by **neufer** » Fri Feb 18, 2011 5:29 am

garry wrote:
With the impactor fired from the satellite, there has never been a satisfactory explanation of the bright flash seen in the You Tube video. The impactor was an inert object, so there should only of been a hole and a lot of material thrown up. But a bright flash? The reason there was no crater and no debris thrown up was that the impactor vaporised before hitting the surface.......

You got to see sunlit fresh snow and dry ice with black space and a very dark comet as contrasting background.

http://en.wikipedia.org/wiki/Tempel_1 wrote:
<<Tempel 1 is not a bright comet; its brightest apparent magnitude since discovery has been 11, far below naked-eye visibility. Measurements taken by the Hubble Space Telescope in visible light and the Spitzer Space Telescope in infrared light suggest a low [visible] albedo of only 4%.>>

by **garry** » Fri Feb 18, 2011 5:19 am

With the impactor fired from the satellite, there has never been a satisfactory explanation of the bright flash seen in the You Tube video. The impactor was an inert object, so there should only of been a hole and a lot of material thrown up. But a bright flash? The reason there was no crater and no debris thrown up was that he impactor vaporised before hitting the surface.......

by **NoelC** » Thu Feb 17, 2011 10:42 pm

glaucoramalho wrote:There are something wrong here.

Just for helpful reference...

-Noel

by **BMAONE23** » Thu Feb 17, 2011 10:33 pm

It gets up to 280 F (138 C) on the moon.
At high noon the average temperature of the lunar surface can reach that temperature. But that's not the same thing as saying it was 72 F (22 C) in Los Angeles today. The latter is air temperature. The temperature of various surfaces in Los Angeles might have been as high as 180 F (82 C). Air temperature has no meaning on the moon because there's no air.

Consider that the moon is (+/-) 1AU from the sun and can maintain a Sun facing surface temperature of up to 280d F. A Comet at 1.5AU could easily maintain a sun facing surface temperature capable of creating outgassing events of it's more volatile materials. The Sun is the source of the IR (heat) energy required to create the outgassing events that light these up

by **Chris Peterson** » Thu Feb 17, 2011 10:06 pm

glaucoramalho wrote:The comet are actually at 1.508AU from the Sun, enough to exhibit comma and tail. You can't see it on Deep Impact photos because the outer parts of the comet are only visible far far away...

Thanks. I clicked on 10P/Tempel, which is what's at 2.5 AU. But it doesn't change the argument: at 1.5 AU, 9P/Temple is simply not a very active comet. Yes, you need to see a large volume of space to detect the coma, but that coma remains very tenuous compared to more active comets.

So, where is the energy input to produce such kind of output? Water and ice don't works, and five or six jets coming from inside to outside the nucleus is yet too faint. No distance enough to warm whatever are inside the nucleus from Sun heat, and yet too distant to reflect Sun light that manner. There are something wrong here.

Nothing is wrong. The comet is absorbing energy from the Sun, heating up, and releasing volatile gases- water, methane, CO2, etc.

by **glaucoramalho** » Thu Feb 17, 2011 9:30 pm

Chris Peterson wrote:
glaucoramalho wrote:Hi people! Good Morning from Brazil!

I was looking for distant pictures of Tempel 1 to see how it looks like at a distance, and what I found was a huge Celestial Dragon across the sky with a big corona and tail, not this dry rock pictures NASA released last Monday.
This is not a very active comet. When it is closest to the Sun (at about 1.5 AU) and outgassing, it shows a small coma, and not much of a tail. It is currently at 2.5 AU, far from its perihelion, and not active at all.

Comparing the photos of Deep Impact mission (with no water or ice in any known form and no jets coming out of the nucleus at all), how is that possible for a so small asteroidal object to exhibit a so well formed tail and corona for at least 144 years from its discovery (maybe thousands and thousands of years), with no known source of energy?
As with all comets, its evaporation is driven by the Sun. Comets have active lifetimes of a few orbits to hundreds of orbits, depending on their composition and how near they get to the Sun. Tempel 1 is a very dry comet- more dust than volatiles. It may, in fact, be late in its life as an active comet.

The comet are actually at 1.508AU (http://aop.astro.umd.edu/where/Tempel1.shtml) from the Sun, enough to exhibit comma and tail. You can't see it on Deep Impact photos because the outer parts of the comet are only visible far far away, like on this picture: http://www.scienceinschool.org/reposito ... _large.jpg. It is not a little comma and tail, it is a HUGE comma and tail, but from distance.
The comet nucleus itself is just a little particle somewhere in the picture and is active.

So, where is the energy input to produce such kind of output? Water and ice don't works, and five or six jets coming from inside to outside the nucleus is yet too faint. No distance enough to warm whatever are inside the nucleus from Sun heat, and yet too distant to reflect Sun light that manner. There are something wrong here.

by **glaucoramalho** » Thu Feb 17, 2011 9:23 pm

NoelC wrote:
glaucoramalho wrote:how is that possible for a so small asteroidal object to exhibit a so well formed tail and corona for at least 144 years from its discovery (maybe thousands and thousands of years), with no known source of energy??
1. I don't think it's from the asteroid belt, so I'm not sure about your use of the term "asteroidal".

2. Regarding your characterizing it as being "so small", consider the barely visible crater we made, yet Chris' description of how much material the impactor caused to be released. This thing is actually quite HUGE! Thanks to this discussion I know I have a better feel for the size in real terms.

3. Don't look now but the Sun is a rather significant source of energy.

4. Further regarding the longevity of comets... Do comets accumulate more ice/snow/dirt when they're WAYYY out at the far ends of their orbits for a long time? Or is the material out in the far reaches of the solar system simply too sparse for that to happen significantly?

I still say we need to nuke one of these things some time, though...

-Noel

1 and 2. I said asteroidal because is not too small and not too large. This is the description of an asteroid, right? I guess not all asteroids come from the asteroid belt.

3. In this case, 0.5 UA or 1.5 UA is too far to exhibit coloured comma and tail by Sun heat anyway, and that little jets coming out of the nucleus are tooooooo thin to count as a comet structure.

4. Only if the comma tail is not going out from nucleus, but coming in and bringing material to the nucleus. We already saw images where comets lefts lot of material during passages,
but we should consider that this rocks are not big enough to keep materials from gravitational means that comes from outside IF that happens.

by **neufer** » Thu Feb 17, 2011 5:06 pm

http://www.planetary.org/blog/article/00002920/ wrote:
The Planetary Society Blog By Emily Lakdawalla

Guess what? Tempel 1 is a comet! See, it has jets!
I can convince myself that I can see at least four jets;
Stardust investigator Jessica Sunshine told me she's seen five.
Click to view full size image 1 or image 2
Stardust reveal at least four jets rising from the surface.
Credit: NASA / JPL / Cornell / processed by Emily Lakdawalla>>

Chris Peterson wrote:
glaucoramalho wrote:
I was looking for distant pictures of Tempel 1 to see how it looks like at a distance, and what I found was a huge Celestial Dragon across the sky with a big corona and tail, not this dry rock pictures NASA released last Monday. Comparing the photos of Deep Impact mission (with no water or ice in any known form and no jets coming out of the nucleus at all), how is that possible for a so small asteroidal object to exhibit a so well formed tail and corona for at least 144 years from its discovery (maybe thousands and thousands of years), with no known source of energy?
This is not a very active comet. When it is closest to the Sun (at about 1.5 AU) and outgassing, it shows a small coma, and not much of a tail. It is currently at 2.5 AU, far from its perihelion, and not active at all.

As with all comets, its evaporation is driven by the Sun. Comets have active lifetimes of a few orbits to hundreds of orbits, depending on their composition and how near they get to the Sun. Tempel 1 is a very dry comet- more dust than volatiles. It may, in fact, be late in its life as an active comet.

by **Chris Peterson** » Thu Feb 17, 2011 4:12 pm

glaucoramalho wrote:Hi people! Good Morning from Brazil!

I was looking for distant pictures of Tempel 1 to see how it looks like at a distance, and what I found was a huge Celestial Dragon across the sky with a big corona and tail, not this dry rock pictures NASA released last Monday.

This is not a very active comet. When it is closest to the Sun (at about 1.5 AU) and outgassing, it shows a small coma, and not much of a tail. It is currently at 2.5 AU, far from its perihelion, and not active at all.

Comparing the photos of Deep Impact mission (with no water or ice in any known form and no jets coming out of the nucleus at all), how is that possible for a so small asteroidal object to exhibit a so well formed tail and corona for at least 144 years from its discovery (maybe thousands and thousands of years), with no known source of energy?

As with all comets, its evaporation is driven by the Sun. Comets have active lifetimes of a few orbits to hundreds of orbits, depending on their composition and how near they get to the Sun. Tempel 1 is a very dry comet- more dust than volatiles. It may, in fact, be late in its life as an active comet.

by **Beyond** » Thu Feb 17, 2011 3:59 pm

NoelC wrote: I still say we need to nuke one of these things, sometime though...

Hey - Mr. Science Officer, shouldn't that be - hit it with a Photon Torpedo

OH, nevermind. Wrong ship.

by **NoelC** » Thu Feb 17, 2011 3:21 pm

glaucoramalho wrote:how is that possible for a so small asteroidal object to exhibit a so well formed tail and corona for at least 144 years from its discovery (maybe thousands and thousands of years), with no known source of energy??

1. I don't think it's from the asteroid belt, so I'm not sure about your use of the term "asteroidal".

2. Regarding your characterizing it as being "so small", consider the barely visible crater we made, yet Chris' description of how much material the impactor caused to be released. This thing is actually quite HUGE! Thanks to this discussion I know I have a better feel for the size in real terms.

3. Don't look now but the Sun is a rather significant source of energy.

4. Further regarding the longevity of comets... Do comets accumulate more ice/snow/dirt when they're WAYYY out at the far ends of their orbits for a long time? Or is the material out in the far reaches of the solar system simply too sparse for that to happen significantly?

I still say we need to nuke one of these things some time, though...

-Noel

by **biddie67** » Thu Feb 17, 2011 12:32 pm

Thanks Ann -

by **glaucoramalho** » Thu Feb 17, 2011 11:48 am

Hi people! Good Morning from Brazil!

I was looking for distant pictures of Tempel 1 to see how it looks like at a distance, and what I found was a huge Celestial Dragon across the sky with a big corona and tail, not this dry rock pictures NASA released last Monday.

Comparing the photos of Deep Impact mission (with no water or ice in any known form and no jets coming out of the nucleus at all), how is that possible for a so small asteroidal object to exhibit a so well formed tail and corona for at least 144 years from its discovery (maybe thousands and thousands of years), with no known source of energy??

I'm sending my sources for your review and comments:

http://www.nasa.gov/mission_pages/stard ... index.html
http://www.nasa.gov/mission_pages/deepi ... tures.html
http://www.scienceinschool.org/reposito ... _large.jpg

Cheers!

by **Ann** » Thu Feb 17, 2011 4:53 am

biddie67 wrote:
APOD Robot wrote: ...... over the next few years astronomers who specialize in comets and the understanding the early Solar System ....
I've seen references to comets holding clues to the early Solar System several times in the past but I don't seem to get why that might be so. To me if something is in our "vicinity", it must have originated in the same general time span as the planets themselves.

Why do astronomers think that comets might hold clues that the Sun or planets don't also have?

Well... if I understand it correctly, comets are believed to have formed in the outer parts of the solar system and mostly stayed there, too, where they might be relatively unchanged since the time they were formed. Objects closer to the Sun are supposed to have changed, mostly because of ultraviolet irradiation from the Sun.

Ann

by **biddie67** » Thu Feb 17, 2011 4:35 am

APOD Robot wrote: ...... over the next few years astronomers who specialize in comets and the understanding the early Solar System ....

I've seen references to comets holding clues to the early Solar System several times in the past but I don't seem to get why that might be so. To me if something is in our "vicinity", it must have originated in the same general time span as the planets themselves.

Why do astronomers think that comets might hold clues that the Sun or planets don't also have?

by **Ann** » Thu Feb 17, 2011 4:20 am

neufer wrote:
NoelC wrote:
Why not send a powerful bomb and make an actual sizable hole in it?

Maybe hit it with a whole bunch of 'em and carve a message in it.

WE CAME IN PEACE FOR ALL MANKIND

And then, you know, a sizable fragment of the poor comet could ricochet our way and hit us.

That would be a peaceful inter-solar system body exchange, for sure!

Ann

by **neufer** » Thu Feb 17, 2011 3:41 am

NoelC wrote:
Why not send a powerful bomb and make an actual sizable hole in it?

Maybe hit it with a whole bunch of 'em and carve a message in it.

WE CAME IN PEACE FOR ALL MANKIND

by **owlice** » Thu Feb 17, 2011 2:34 am

NoelC wrote: Maybe hit it with a whole bunch of 'em and carve a message in it.

Kilroy was here, perhaps?

Maybe better: Property of the Hells Angels

by **Chris Peterson** » Wed Feb 16, 2011 11:40 pm

NoelC wrote:We impact the thing with a high speed collision, and there's nothing significant to show for it?

What's "significant"? There is a visible crater; I think that's significant.

Why not send a powerful bomb and make an actual sizable hole in it? Concern over contaminating the ejecta? Okay, maybe nuking the thing might be a bit extreme, but c'mon already!

The concern with contamination is very real. But aside from that, there's the simple question of practicality. Deep Impact hit the comet with a 370 kg probe traveling 10.2 m/s. That means it released 1.9e10 J, or the equivalent of 4.5 tons of TNT. So the kinetic energy of the probe was twelve times greater than the equivalent mass of TNT. What kind of explosive should they send? How much would it add to the cost of the mission to transport all that mass? Is there any explosive that would come close to releasing the energy of the kinetic collision alone? Realistically, probably not.

The Deep Impact probe resulted in something on the order of 20 million kg of water and dust being ejected. It made a crater 150 meters across. That's pretty significant.

Starship Asterisk*

APOD: Comet Tempel 1 from Stardust NeXT... (2011 Feb 16)

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