"Planet-killing #asteroids impact the earth every 50 million years. The last one impacted 65 million years ago, so we're 15 million years overdue for another one. The scenario of a #comet on a collision course with the earth is utterly probable - indeed, certain."

But she says we just need to "keep calm and don't panic", because #clever people like her are working on it. "This is not a signal to start buying pasta and hoarding toilet rolls " https://www.bbc.co.uk/news/newsbeat-59939577

do not wait to observe #comet #C2025F2SWAN you have to search it in the morning 10-15° above the Eastern horizon around (06:00 in French local time) with binocoloars . Morning sky is preserved from the Moon light for the few next days, so It is possible to make astrophotography with small focal length. But after this sky will be affected by moon light for next week.

#C2025F2SWAN looks to be a dynamically new #comet coming from the Oort Cloud into the inner solar-system for the first time. The orbit is nearly parabolic (e=0.999) and perihelion distance is only q=0.33 UA, It has been discovered after perihelion, probably too faint before, after a probable big out-burst! It absolute magnitude is estimated to H0=9 so near the Bortle Limit 7+6q making its desintegration probablme in the next weeks.

The visibility conditions for comet C/2025 F2 (SWAN) through perihelion and maximum brightness for 51.5° North - see https://www.facebook.com/dan.fischer.393/posts/pfbid023poyxvFZYhxPsT18sxHZejFPYYGiXdeApa3dj78oPqmnw8QRLH22dVFCABnLk93Zl for explanations of the table! In a nutshell, in Central Europe the comet is higher at a given degree of sky darkness in the morning until about 23 April, then in the evening. So expect it at 3 to 5 mag. low at dusk: if the #comet makes it and keeps its fine tail this *may* become a fine nightscape photo opp - but not a significant show for the naked eye.

Here is another outstanding image of comet SWAN25F and its bright bluish-green coma, taken last night by 喜闻乐见小绿人 @xwlj_XLR and posted on twitter -
"Comet SWAN25F
D=203mm f/5​ 60s*44
AstroMamenchi Remote Observatory
2025-04-07

Despite the bad weather, the tail became even longer, extending out of the frame!
4:03 AM · Apr 7, 2025."

Time zone = UTC+8, China.

喜闻乐见小绿人 = Xǐwénlèjiàn xiǎo lǜ rén, The Little Green Man.

Credit: 喜闻乐见小绿人
#Comet
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The green color seen in the coma of many comets such as SWAN25F, but not in their tails, is due to emissions from Diatomic carbon C2 molecules.

Sunlight heats the comet’s ice and organic material to produce quadruple bond C2 molecules, which break apart in ~2 days before they reach the tail. C2 is excited by solar UV radiation and emits mostly in infrared but its triplet state radiates at 518 nm (d3Πg → a3Πu transition below).

https://physicstoday.scitation.org/do/10.1063/pt.6.1.20220110a/full/
https://www.pnas.org/doi/10.1073/pnas.2113315118
#comet
4/n