The Largest Comet We've Ever Seen Just Delivered a Curious Surprise (sciencealert.com) 18
schwit1 shares a report from ScienceAlert: The comet Bernardinelli-Bernstein (BB) -- the largest our telescopes have ever spotted -- is on a journey from the outer reaches of our Solar System that will see it flying relatively close to Saturn's orbit. Now, a new analysis of the data we've collected on BB has revealed something rather surprising. Digging into readings logged by the Transient Exoplanet Survey Satellite (TESS) between 2018 and 2020, researchers have discovered that BB became active much earlier, and much farther out from the Sun, than was previously thought.
A comet becomes active when light from the Sun heats its icy surface, turning ice to vapor and releasing trapped dust and grit. The resulting haze, called a coma, can be useful for astronomers in working out exactly what a particular comet is made out of. In the case of BB, it's still too far out for water to sublimate. Based on studies of comets at similar distances, it's likely that the emerging fog is driven instead by a slow release of carbon monoxide. Only one active comet has previously been directly observed at a greater distance from the Sun, and it was much smaller than BB. "These observations are pushing the distances for active comets dramatically farther than we have previously known," says astronomer Tony Farnham, from the University of Maryland (UMD). "We make the assumption that comet BB was probably active even farther out, but we just didn't see it before this. What we don't know yet is if there's some cut-off point where we can start to see these things in cold storage before they become active."
The research has been published in the Planetary Science Journal.
A comet becomes active when light from the Sun heats its icy surface, turning ice to vapor and releasing trapped dust and grit. The resulting haze, called a coma, can be useful for astronomers in working out exactly what a particular comet is made out of. In the case of BB, it's still too far out for water to sublimate. Based on studies of comets at similar distances, it's likely that the emerging fog is driven instead by a slow release of carbon monoxide. Only one active comet has previously been directly observed at a greater distance from the Sun, and it was much smaller than BB. "These observations are pushing the distances for active comets dramatically farther than we have previously known," says astronomer Tony Farnham, from the University of Maryland (UMD). "We make the assumption that comet BB was probably active even farther out, but we just didn't see it before this. What we don't know yet is if there's some cut-off point where we can start to see these things in cold storage before they become active."
The research has been published in the Planetary Science Journal.
Ok, so if it's active further out (Score:5, Interesting)
Since we think we know the strength of the solar winds and radiation at that distance, it aught to be possible to infer what exactly "being active" at that distance implies. Is there a layer of gasses frozen on the surface that are a lot more volatile than expected? If so, since we know what it takes for them to boil off, what would they need to be? If, on the other hand, observation suggests that there's nothing unusual or unexpected about what is boiling off, how do we need to change our values for the solar winds?
Re: (Score:2, Interesting)
I'm not a planetary scientist, so hopefully someone with some real facts will be along soon.
The article suggests that CO (carbon monoxide) sublimation could be responsible for the coma at these extreme distances. Unfortunately, with such faint objects it will be difficult to get any meaningful spectrographic information to confirm or deny this.
I'd also consider adsorbed or condensed hydrogen as a possible candidate for offgassing at these extreme distances. With an orbital period of 6.7 million years it has
Re: Ok, so if it's active further out (Score:4, Interesting)
Solar winds is just one mechanism involved here. Thereâ(TM)s also a high particle concentration surrounding each planetary #orbit. Trajectory, speed all matters here.
Saturn and Neptune have rings for a reason.
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The surface temperature of Pluto varies (depending on it's orbital position - it has a highly eccentric orbit, e=0.24, and consequently it's solar irradiation varies by over 50%) between about 40 and 60 Kelvin. The boiling point of hydrogen (under 1 atmosphere pressure) is 20.2K (it's sublimation temperature under essentially zero pressure is a good few Kelvin lower). So any hydrogen on the s
Re:Ok, so if it's active further out (Score:5, Funny)
Re: Ok, so if it's active further out (Score:1)
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I’ve been trying to raise awareness about Galactic Warming (GW) for 4.5 billion years but does anyone listen? NO.
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The solar wind is not involved in heating the comet's surface and releasing volatiles. It's all about solar radiation which is indeed easy to model, although there are some unknowns like the comet's albedo. As mentioned in the article there is an assumption that the current activity is carbon monoxide, based on where it's happening. There have been a few other comets with activity at such distances, but most comets that make regular trips to the inner solar system would have burned off those gasses a long t
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There's also a small, and plausibly variable, from object to object) amount of radiogenic heating, While predominantly "dirty snowballs", there are other components in a typical comet. And at very low temperatures (tens of Kelvin), the amount of energy needed to sustain a modest rise in temperature isn't high - not compared to keeping th
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Nothing to see here, move along (Score:4, Funny)
Re: Nothing to see here, move along (Score:2)
I didn't read the article... (Score:2)