Starship Asterisk*

Interstellar Comet 2I Borisov

Explanation: From somewhere else in the Milky Way galaxy, Comet 2I/Borisov was just visiting the Solar System. Discovered by amateur astronomer Gennady Borisov on August 30, 2019, the first known interstellar comet is seen in these two Hubble Space Telescope images from November and December 2019. On the left, a distant background galaxy near the line-of-sight to Borisov is blurred as Hubble tracked the speeding comet and dust tail about 327 million kilometers from Earth. At right, 2I/Borisov appears shortly after perihelion, its closest approach to Sun. European Southern Observatory observations indicate that this comet may never have passed close to any star before its 2019 perihelion passage. Borisov's closest approach to our fair planet, a distance of about 290 million kilometers, came on December 28, 2019. Even though Hubble's sharp images don't resolve the comet's nucleus, they did lead to estimates of less than 1 kilometer for its diameter.

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Fascinating concept, discovery and imaging !

So is this likely to be other worldly in origin, or something slung off our Solar System and looping back to revisit us ?

APOD Robot wrote:

European Southern Observatory observations indicate that this comet may never have passed close to any star before its 2019 perihelion passage. Borisov's closest approach to our fair planet, a distance of about 290 million kilometers, came on December 28, 2019.

290 million kilometers is pretty close, about 2 AU.

I would love to know more about the galaxy that showed up so fascinatingly in the first Hubble picture of Comet 21 Borisov. But I guess that that galaxy must be very faint in our skies.

Ann

RocketRon wrote: ↑Sat Mar 05, 2022 5:40 am Fascinating concept, discovery and imaging !

So is this likely to be other worldly in origin, or something slung off our Solar System and looping back to revisit us ?

Astronomers say that Comet 2I Borisov did not originate in our Solar System.

Ann

But is it really true that Borisov is the first known extrasolar comet? I always thought 'Oumuamua is the first known extrasolar comet

Neat ! I wonder if it might have been sent on it"s journey by being
knocked out of its orinal stellar orbit from a star gone nova?

RocketRon wrote: ↑Sat Mar 05, 2022 5:40 am Fascinating concept, discovery and imaging !

So is this likely to be other worldly in origin, or something slung off our Solar System and looping back to revisit us ?

If it were looping back it would be in an elliptical orbit. Since its orbit is hyperbolic (meaning it is traveling at greater than solar escape velocity) it is almost certainly interstellar in origin.

RedGargoyle wrote: ↑Sat Mar 05, 2022 11:05 am But is it really true that Borisov is the first known extrasolar comet? I always thought 'Oumuamua is the first known extrasolar comet

Oumuamua was the first observed extrasolar object. It did not show sufficient outgasing activity to be labeled a comet (although it might be the core of an extinct comet).

Ann wrote: ↑Sat Mar 05, 2022 6:06 am
I would love to know more about the galaxy that showed up so fascinatingly in the first Hubble picture of Comet 21 Borisov. But I guess that that galaxy must be very faint in our skies.

Ann

The link in the APOD text, Hubble tracked the speeding comet, gives an identification for the galaxy, 2MASX J10500165-0152029. I found it in SkyTools 4V where it's identified as PGC 32442. Here's a screen snip of the chart with data box for it on 16-Nov-2019 UT, indicating magnitude 16.3. Note that comet 2I/Borisov is also shown with its provisional designation, C/2019 Q4 (Borisov) and the cryptic numbers in the Hubble ID essentially match the RA and Dec shown in the SkyTools info.

Joe

With a statistic of two (2!) interstellar objects now detected by us, surely we can work out what the total mass of such objects likely is, in our Galaxy?

heehaw wrote: ↑Sat Mar 05, 2022 8:10 pm With a statistic of two (2!) interstellar objects now detected by us, surely we can work out what the total mass of such objects likely is, in our Galaxy?

We don't know how many we're missing. So far these have leaned in the direction of being lucky catches. But surveys are getting better and more sensitive. I'd be inclined to wait until we have a few more before taking any statistical analysis too seriously.

Joe Stieber wrote: ↑Sat Mar 05, 2022 6:15 pm

Ann wrote: ↑Sat Mar 05, 2022 6:06 am
I would love to know more about the galaxy that showed up so fascinatingly in the first Hubble picture of Comet 21 Borisov. But I guess that that galaxy must be very faint in our skies.

Ann

The link in the APOD text, Hubble tracked the speeding comet, gives an identification for the galaxy, 2MASX J10500165-0152029. I found it in SkyTools 4V where it's identified as PGC 32442. Here's a screen snip of the chart with data box for it on 16-Nov-2019 UT, indicating magnitude 16.3. Note that comet 2I/Borisov is also shown with its provisional designation, C/2019 Q4 (Borisov) and the cryptic numbers in the Hubble ID essentially match the RA and Dec shown in the SkyTools info.

Joe

Thanks, Joe!

Ann

My question is more about the image itself. Joe cited that that the galaxy is ~500mly away. Then why is it so blurred in the pic? IIRC, Hubble has snapped pictures of mid-range galaxies that are far crisper.

longtry wrote: ↑Mon Aug 22, 2022 12:46 am My question is more about the image itself. Joe cited that that the galaxy is ~500mly away. Then why is it so blurred in the pic? IIRC, Hubble has snapped pictures of mid-range galaxies that are far crisper.

APOD Robot wrote:

On the left, a distant background galaxy near the line-of-sight to Borisov is blurred as Hubble tracked the speeding comet and dust tail about 327 million kilometers from Earth.

Hubble was focusing on the comet, not the galaxy, and it was tracking a moving target.

Ann

Ann wrote: ↑Mon Aug 22, 2022 4:07 am

longtry wrote: ↑Mon Aug 22, 2022 12:46 am My question is more about the image itself. Joe cited that that the galaxy is ~500mly away. Then why is it so blurred in the pic? IIRC, Hubble has snapped pictures of mid-range galaxies that are far crisper.

APOD Robot wrote:

On the left, a distant background galaxy near the line-of-sight to Borisov is blurred as Hubble tracked the speeding comet and dust tail about 327 million kilometers from Earth.

Hubble was focusing on the comet, not the galaxy, and it was tracking a moving target.

Ann

And indeed, looking closely at the galaxy we can see that it is not blurred, but motion streaked.

Chris Peterson wrote: ↑Mon Aug 22, 2022 4:47 am

Ann wrote: ↑Mon Aug 22, 2022 4:07 am

longtry wrote: ↑Mon Aug 22, 2022 12:46 am My question is more about the image itself. Joe cited that that the galaxy is ~500mly away. Then why is it so blurred in the pic? IIRC, Hubble has snapped pictures of mid-range galaxies that are far crisper.

APOD Robot wrote:

On the left, a distant background galaxy near the line-of-sight to Borisov is blurred as Hubble tracked the speeding comet and dust tail about 327 million kilometers from Earth.

Hubble was focusing on the comet, not the galaxy, and it was tracking a moving target.

Ann

And indeed, looking closely at the galaxy we can see that it is not blurred, but motion streaked.

What in particular indicates that it is not out of focus but instead blurred by motion? (It looks too "blurry" to me to be able to see much of anything!)

johnnydeep wrote: ↑Mon Aug 22, 2022 1:52 pm

Chris Peterson wrote: ↑Mon Aug 22, 2022 4:47 am

Ann wrote: ↑Mon Aug 22, 2022 4:07 am




Hubble was focusing on the comet, not the galaxy, and it was tracking a moving target.

Ann

And indeed, looking closely at the galaxy we can see that it is not blurred, but motion streaked.

What in particular indicates that it is not out of focus but instead blurred by motion? (It looks too "blurry" to me to be able to see much of anything!)

Chris Peterson wrote: ↑Mon Aug 22, 2022 2:06 pm

johnnydeep wrote: ↑Mon Aug 22, 2022 1:52 pm

Chris Peterson wrote: ↑Mon Aug 22, 2022 4:47 am

And indeed, looking closely at the galaxy we can see that it is not blurred, but motion streaked.

What in particular indicates that it is not out of focus but instead blurred by motion? (It looks too "blurry" to me to be able to see much of anything!)

borisovStsci1826_drift.jpg

Ok, I did see those possible directional indications, but wasn't sure it was enough to prove anything definitive. I guess it is! And probably a more detailed analysis of the pixels would provide more certainty.