APOD: Approaching Asteroid Ceres (2015 Jan 20)

[APOD Robot]

Approaching Asteroid Ceres

Explanation: It is the largest asteroid in the asteroid belt -- what secrets does it hold? To find out, NASA has sent the robotic Dawn spacecraft to explore and map this cryptic 1,000-kilometer wide world: Ceres. Orbiting between Mars and Jupiter, Ceres is officially categorized as a dwarf planet but has never been imaged in detail. Featured here is a 20-frame video taken a week ago of Dawn's approach that now rivals even the best images of Ceres ever taken by the Hubble Space Telescope. The video shows enough surface definition to discern its 9-hour rotation period. On target to reach Ceres in early March, Dawn will match speeds and attempt to orbit this previously unexplored body, taking images and data that may help humanity better understand not only the nature and history of Ceres but also the early history of our entire Solar System.

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[Boomer12k]

Um....can't wait until it is closer....

:---[===] *

[workgazer]

Any ideas as to what the bright spot is moving across the top left of ceres, The hubble image also shows a white spot, could this be a storm?

[BDanielMayfield]

Any ideas as to what the bright spot is moving across the top left of ceres, The hubble image also shows a white spot, could this be a storm?

I'd guess it's a relatively fresh impact crater. Ceres is too small to have anything but a very tenuous atmosphere.

Bruce

[Joules]

Is it just the phase that makes it look so oblate?
Hubble image doesn't look that squashed: http://phys.org/news/2011-07-minor-plan ... earth.html

[epitalon]

hello,
my post is relatively unrelated to Ceres, rather loosely related to Dawn spacecraft.
I found on Dawn website a simulated view of our inner solar system from Dawn, in which some stars from Orion and Taurus constellations are depicted.
See http://dawn.jpl.nasa.gov/mission/live_shots.asp

In this simulated view, the constellations look as seen from human eye, contrarily to some pictures obtained by photography.
This allows me to point to some idea that I had in mind for a while : constellation names come really from their resemblance with natural objects.
It is not so evident from today's standard partition of the sky in constellations.

The simulated view in question allows me to show you how I see a "bull" in the Taurus constellation. Rather, I can imagine easily a dancing calf, its queue pointed up, its two fore legs streched forward, its two eyes and its two horns, Aldebaran being at the tip of one of it.
In the attached picture, I outline the body, two fore and one hind legs, horns, eyes, nose and queue.

Please, let me know if what I outlined is a standard "explanation" of Taurus or something rather fancyful !

Jean-Marie Epitalon, just an admirer of sky

[Chris Peterson]

In this simulated view, the constellations look as seen from human eye, contrarily to some pictures obtained by photography.
This allows me to point to some idea that I had in mind for a while : constellation names come really from their resemblance with natural objects.
It is not so evident from today's standard partition of the sky in constellations.

The zodiacal constellations, as well as most of the northern ones, are extremely ancient. In most cases, we have no idea exactly how they were imagined by those who created the names. The practice of constructing asterisms with lines between bright stars appears modern. As originally named, the constellations presumably represented some mix of appearance and mythology.

If you do a search on Taurus, you'll find different modern interpretations of a bull asterism within the constellation. About the only thing most have in common is the horns.

[starsurfer]

Wasn't Ceres discovered by Giuseppe Piazzi?

[Chris Peterson]

Any ideas as to what the bright spot is moving across the top left of ceres, The hubble image also shows a white spot, could this be a storm?

It's not a storm, because Ceres has no atmosphere to speak of. It's probably not as white as it looks, either. In this image, the contrast has probably been stretched so that the darkest point is rendered as black and the lightest as white. That brings out the most detail (and is common with astronomical and many other scientific images), but doesn't give a true representation of brightness as our eyes would see things. That white area- a crater perhaps- might be just a smidgen brighter than the surrounding areas.

[Chris Peterson]

Wasn't Ceres discovered by Giuseppe Piazzi?

Yes. Why do you ask?

[JuanAustin]

I was curious to know how thick vertically the asteroid belt was in terms of distance. Do spacecraft have a relatively safe passage through the belt on their way to explore the planets or do they have to hop over or under the belt to avoid a random collision?

[Chris Peterson]

I was curious to know how thick vertically the asteroid belt was in terms of distance. Do spacecraft have a relatively safe passage through the belt on their way to explore the planets or do they have to hop over or under the belt to avoid a random collision?

Billions of years of interactions with planets and other asteroids have created whole populations with different inclinations. What that means is that the asteroid belt can be considered quite "thick" (although that isn't exactly the right word).

But it doesn't matter. There is so little material in it compared with its volume that spacecraft could move back and forth across it for thousands of years without ever even seeing an asteroid, let alone colliding with one. For all practical purposes the asteroid belt is empty space.

[captainwiggins48]

Anticipation! How does this sound: Mercury, Venus, Earth, Mars, Ceres...!

[geckzilla]

Anticipation! How does this sound: Mercury, Venus, Earth, Mars, Ceres...!

Click to view full size image

[Ron-Astro Pharmacist]

The explanation says "..and attempt to orbit.." Is this, in the scheme of efforts, a fairly difficult undertaking? It's easy to take for granted our abilities with respect to our capabilities. Landing on a comet was difficult for many reasons but easy to understand in difficulty from a lay persons viewpoint but navigation to, far off, smaller targets may seem a bit easier from the standpoint we've done it more frequently.

Has anyone forecast the odds of Dawn not rising to its objective and "Cere-ously" not obtaining a stable orbit (if I might pun)?

[Chris Peterson]

The explanation says "..and attempt to orbit.." Is this, in the scheme of efforts, a fairly difficult undertaking? It's easy to take for granted our abilities with respect to our capabilities. Landing on a comet was difficult for many reasons but easy to understand in difficulty from a lay persons viewpoint but navigation to, far off, smaller targets may seem a bit easier from the standpoint we've done it more frequently.

Getting to the right place isn't that hard. But trying to enter orbit around a fairly low mass body is problematic, because you typically have to shed a lot of the velocity that was used to get there in the first place. That's why we're doing a Pluto flyby and not going into orbit. At Pluto's distance, we needed to build up such a high velocity just to get there in a reasonable time that there's no practical way to get rid of it once we're there. It's not quite so bad with asteroids, because they're closer and we can utilize more reasonable transit velocities. But it's still a tricky problem. I think all the math has been worked out and the engineering is solid, so there's no reason Dawn shouldn't be able to enter orbit. But it depends on rocket motors working correctly, and there is always a risk associated with that. Most mission failures seem to involve the rockets.

[Ron-Astro Pharmacist]

The explanation says "..and attempt to orbit.." Is this, in the scheme of efforts, a fairly difficult undertaking? It's easy to take for granted our abilities with respect to our capabilities. Landing on a comet was difficult for many reasons but easy to understand in difficulty from a lay persons viewpoint but navigation to, far off, smaller targets may seem a bit easier from the standpoint we've done it more frequently.

Getting to the right place isn't that hard. But trying to enter orbit around a fairly low mass body is problematic, because you typically have to shed a lot of the velocity that was used to get there in the first place. That's why we're doing a Pluto flyby and not going into orbit. At Pluto's distance, we needed to build up such a high velocity just to get there in a reasonable time that there's no practical way to get rid of it once we're there. It's not quite so bad with asteroids, because they're closer and we can utilize more reasonable transit velocities. But it's still a tricky problem. I think all the math has been worked out and the engineering is solid, so there's no reason Dawn shouldn't be able to enter orbit. But it depends on rocket motors working correctly, and there is always a risk associated with that. Most mission failures seem to involve the rockets.

Thank you. I was wondering why we didn't attempt to orbit Pluto with New Horizons. Ron

[Joules]

Jan. 22, 2014: Scientists using the Herschel space observatory have made the first definitive detection of water vapor on the largest and roundest object in the asteroid belt, dwarf planet Ceres.

http://science.nasa.gov/science-news/sc ... jan_ceres/

January 20, 2015 ... First Hubble and Now Dawn Have Seen This White Spot on Ceres. What is it?

http://www.universetoday.com/118358/fir ... hat-is-it/

Ice and snow are often white.

[MarkBour]

The explanation says "..and attempt to orbit.." Is this, in the scheme of efforts, a fairly difficult undertaking? . . .

Getting to the right place isn't that hard. But trying to enter orbit around a fairly low mass body is problematic, because you typically have to shed a lot of the velocity that was used to get there in the first place. That's why we're doing a Pluto flyby and not going into orbit. . . . But it depends on rocket motors working correctly, and there is always a risk associated with that. Most mission failures seem to involve the rockets.

I suppose the use of the ion-propulsion thrusters, which are new tech and have a limited maximum power output, make this more challenging. On the other hand, Dawn is the only spacecraft that is about to attempt to orbit a celestial body who can say: "I'm experienced. I've done this before." So, perhaps it actually has a lower likelihood of failure than most.

[Chris Peterson]

I suppose the use of the ion-propulsion thrusters, which are new tech and have a limited maximum power output, make this more challenging. On the other hand, Dawn is the only spacecraft that is about to attempt to orbit a celestial body who can say: "I'm experienced. I've done this before." So, perhaps it actually has a lower likelihood of failure than most.

Ion thrusters might make it easier, since they require so little reaction mass compared with conventional rockets. Still, the low thrust means long deceleration times.

[Indigo_Sunrise]

All your questions about the White Spot on Ceres have been answered.

[DavidLeodis]

It is interesting to read in the Wikipedia entry about Dawn that "When the last of its hydrazine fuel is used up, Dawn will become a perpetual satellite of Ceres; its orbit is predicted to be very stable".

[MarkBour]

Unless the Ceresians do us a favor and refuel it and send it back.

[DavidLeodis]

I will be grateful if somebody could please state what PSI stands for in the credit as I have not been able to definitely find out despite doing a lot of searching. It seemed best now to ask the forum.

[Donnageddon]

I have a hunch this is what you seek http://www.psi.edu/