<p>This is more of a recent example than a record.
On 2019-07-25, asteroid <a href="https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=K19O00K" rel="nofollow noreferrer">2019 OK</a> passed about 65000 km from the Earth at a relative speed of 24.5 km/s.
The Minor Planet Center lists <a href="https://minorplanetcenter.net/db_search/show_object?object_id=K19O00K" rel="nofollow noreferrer">multiple
observations</a> from sites in Italy and Armenia an hour before closest approach.
Using pairs of these (streak endpoints?) by the ISON-Castelgrande observatory, I compute motions of 29.8° per hour at 00:23 UT and 31.7° per hour at 00:26 UT.</p>
<p>The MPC <a href="https://minorplanetcenter.net/iau/MPEph/MPEph.html" rel="nofollow noreferrer">ephemeris service</a>
gives sky motions of 30.6°/hr and 32.5°/hr from site L28 at those times.
If someone had observed the asteroid from (25°S, 85°E) in the Indian Ocean at 01:22 UT, they would have seen it move 76° per hour.</p>
<hr />
<p><strong>Update:</strong> On 2020-08-16, tiny (<a href="https://cneos.jpl.nasa.gov/glossary/h.html" rel="nofollow noreferrer">H</a>=29.8) asteroid <a href="https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=K20Q00G" rel="nofollow noreferrer">2020 QG</a> passed by at 12.3 km/s, about 9320 km from the Earth's center or 2950 km from the surface.
A <a href="https://www.nasa.gov/feature/jpl/tiny-asteroid-buzzes-by-earth-the-closest-flyby-on-record" rel="nofollow noreferrer">NASA news article</a> said this was a new record for close approach distance.
An observer in the right place at 04:09 UT would have seen a maximum sky motion of
<span class="math-container">$$\mathrm{\frac{12.3~km/s}{2950~km} = 0.0042~radian/s = 860^\circ/hr}$$</span>
From pairs of <a href="https://minorplanetcenter.net/db_search/show_object?object_id=K20Q00G" rel="nofollow noreferrer">actual observations</a> reported to MPC,
<a href="https://www.ztf.caltech.edu/" rel="nofollow noreferrer">ZTF</a> Palomar (I41) saw a sky motion of  566°/hr at 10:23 UT,
and <a href="https://atlas.fallingstar.com/home.php" rel="nofollow noreferrer">ATLAS</a> Mauna Loa (T08) recorded 439°/hr around 11:46 UT.</p>

CC BY-SA 4.0
2019-10-18T07:15:56.877Z
[smokin](https://i.sstatic.net/iihwv.gif)! But where does 761 arcsec in 24 seconds come from on that page?
uhoh
CC BY-SA 4.0
2019-10-18T14:16:48.163Z
@uhoh, Those seem to be differences derived between the last two observations in the table taken on 2019-07-25....
amateurAstro
CC BY-SA 4.0
2019-10-18T15:42:05.747Z
@amateurAstro got it, thanks!
uhoh
CC BY-SA 4.0
2020-08-19T07:18:38.937Z
2020 QG is probably a new record! https://minorplanetcenter.net/neo/view?date=2459077.65&label=2020%20QG&packed_desig=K20Q00G
uhoh
CC BY-SA 4.0
2020-08-19T10:31:02.187Z
Oh 2020-08-16, yikes! What is H=29.8?
uhoh
CC BY-SA 4.0
2020-08-19T10:35:57.313Z
@uhoh Absolute magnitude based on 1 AU from both Earth and Sun, and opposition phase.
Mike G
CC BY-SA 4.0
2020-09-10T05:32:10.270Z
Thank for the edit, I wish I could upvote twice! SE doesn't generate notifications to the asker when answer posts are updated, but I saw this in the active queue and now see that you've updated.
uhoh
CC BY-SA 4.0
2020-11-16T03:57:13.980Z
[2020 VT4](https://minorplanetcenter.net/db_search/show_object?object_id=K20V04T) is another close one, but I'd rather not keep revising this answer.
Mike G
CC BY-SA 4.0
2019-10-18T06:09:11.013Z
2020-09-10T00:42:37.043Z
2020-09-10T00:42:37.043Z
Mike G
<p>If I've done my maths correctly <a href="https://astronomy.stackexchange.com/a/33695/7982">in this answer</a> comet 2I/Borisov (C/2019 Q4) was seen to move about 0.2 degrees in 7 hours, which is almost 0.7 degrees per day.</p>

<p>I'm assuming this is pretty rapid motion for a comet, but I'm wondering if comets (or asteroids) have been observed to move even faster than this relative to the celestial sphere.</p>

<p>Yes I know the speed of apparent motion depends on incidentals like how close the comet happens to pass to the Earth. I'm just wondering if any particular comet stands out as been particularly fast, possibly even difficult to track because perhaps some software didn't allow such a large offset in tracking relative to the stars.</p>

<p><strong>Question:</strong> What is the fastest recorded apparent motion of a comet or asteroid, seen from Earth (degrees/day) relative to the celestial sphere?</p>

<p><strong>note:</strong> @JamesK's <a href="https://astronomy.stackexchange.com/questions/33697/fastest-recorded-apparent-motion-of-a-comet-or-asteroid-seen-from-earth-degrees#comment64065_33697">comment</a> reminds me that I would like to exclude meteor tracks. For the purposes of this question the recorded tracks should be produced reflected light, either of the Sun or of radar illumination, and not be something burning up in our atmosphere.</p>

CC BY-SA 4.0
2019-10-17T12:27:34.283Z
According to Wikipedia, Comet IRAS-Araki-Alcock "swept across the sky at an incredible speed of some 30 degrees per day". I'm not sure if this is the fastest or not.
JohnHoltz
CC BY-SA 4.0
2019-10-17T12:30:54.673Z
@JohnHoltz Wow! In a telescope that might have been noticeable fairly quickly.
uhoh
CC BY-SA 4.0
2019-10-17T21:29:23.277Z
Well there was a very small asteroid visible in Chelyabinsk that covered up to 180 degrees in a few seconds.....
James K
CC BY-SA 4.0
2021-03-24T20:29:14.183Z
In the near future, 99942 Apophis will appear to cover 180 degrees in 1 hour.
WarpPrime
CC BY-SA 4.0
2021-03-24T20:46:21.810Z
@fasterthanlight yes indeed [your answer](https://astronomy.stackexchange.com/a/42084/7982) points this out, and if you're on Stack Exchange in 2029 please post an answer here after it's passage is recorded! I wish SE has a "reminders" feature.
uhoh
<comets><near-earth-object><apparent-motion>
Fastest recorded apparent motion of a comet or asteroid seen from Earth (degrees/day)?
uhoh
# Fastest recorded apparent motion of a comet or asteroid seen from Earth (degrees/day)?

(Asked by: username_0 on 2019-10-17)

If I've done my maths correctly [in this answer](https://astronomy.stackexchange.com/a/33695/7982) comet 2I/Borisov (C/2019 Q4) was seen to move about 0.2 degrees in 7 hours, which is almost 0.7 degrees per day.

I'm assuming this is pretty rapid motion for a comet, but I'm wondering if comets (or asteroids) have been observed to move even faster than this relative to the celestial sphere.

Yes I know the speed of apparent motion depends on incidentals like how close the comet happens to pass to the Earth. I'm just wondering if any particular comet stands out as been particularly fast, possibly even difficult to track because perhaps some software didn't allow such a large offset in tracking relative to the stars.

**Question:** What is the fastest recorded apparent motion of a comet or asteroid, seen from Earth (degrees/day) relative to the celestial sphere?

**note:** @JamesK's [comment](https://astronomy.stackexchange.com/questions/33697/fastest-recorded-apparent-motion-of-a-comet-or-asteroid-seen-from-earth-degrees#comment64065_33697) reminds me that I would like to exclude meteor tracks. For the purposes of this question the recorded tracks should be produced reflected light, either of the Sun or of radar illumination, and not be something burning up in our atmosphere.

**Tags:** comets, near-earth-object, apparent-motion
> **Comments:**
> **username_1**: According to Wikipedia, Comet IRAS-Araki-Alcock "swept across the sky at an incredible speed of some 30 degrees per day". I'm not sure if this is the fastest or not.  
> **username_0**: @JohnHoltz Wow! In a telescope that might have been noticeable fairly quickly.  
> **username_2**: Well there was a very small asteroid visible in Chelyabinsk that covered up to 180 degrees in a few seconds.....  
> **username_3**: In the near future, 99942 Apophis will appear to cover 180 degrees in 1 hour.  
> **username_0**: @fasterthanlight yes indeed [your answer](https://astronomy.stackexchange.com/a/42084/7982) points this out, and if you're on Stack Exchange in 2029 please post an answer here after it's passage is recorded! I wish SE has a "reminders" feature.  

---

## 1 answers

### Answer by username_4 on 2019-10-18. Score: 5 | Accepted answer

This is more of a recent example than a record.
On 2019-07-25, asteroid [2019 OK](https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=K19O00K) passed about 65000 km from the Earth at a relative speed of 24.5 km/s.
The Minor Planet Center lists [multiple
observations](https://minorplanetcenter.net/db_search/show_object?object_id=K19O00K) from sites in Italy and Armenia an hour before closest approach.
Using pairs of these (streak endpoints?) by the ISON-Castelgrande observatory, I compute motions of 29.8° per hour at 00:23 UT and 31.7° per hour at 00:26 UT.

The MPC [ephemeris service](https://minorplanetcenter.net/iau/MPEph/MPEph.html)
gives sky motions of 30.6°/hr and 32.5°/hr from site L28 at those times.
If someone had observed the asteroid from (25°S, 85°E) in the Indian Ocean at 01:22 UT, they would have seen it move 76° per hour.

---

**Update:** On 2020-08-16, tiny ([H](https://cneos.jpl.nasa.gov/glossary/h.html)=29.8) asteroid [2020 QG](https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=K20Q00G) passed by at 12.3 km/s, about 9320 km from the Earth's center or 2950 km from the surface.
A [NASA news article](https://www.nasa.gov/feature/jpl/tiny-asteroid-buzzes-by-earth-the-closest-flyby-on-record) said this was a new record for close approach distance.
An observer in the right place at 04:09 UT would have seen a maximum sky motion of
$$\mathrm{\frac{12.3~km/s}{2950~km} = 0.0042~radian/s = 860^\circ/hr}$$
From pairs of [actual observations](https://minorplanetcenter.net/db_search/show_object?object_id=K20Q00G) reported to MPC,
[ZTF](https://www.ztf.caltech.edu/) Palomar (I41) saw a sky motion of 566°/hr at 10:23 UT,
and [ATLAS](https://atlas.fallingstar.com/home.php) Mauna Loa (T08) recorded 439°/hr around 11:46 UT.

> **Comments:**
> **username_0**: [smokin](https://i.sstatic.net/iihwv.gif)! But where does 761 arcsec in 24 seconds come from on that page?  
> **username_5**: @uhoh, Those seem to be differences derived between the last two observations in the table taken on 2019-07-25....  
> **username_0**: @amateurAstro got it, thanks!  
> **username_0**: 2020 QG is probably a new record! https://minorplanetcenter.net/neo/view?date=2459077.65&label=2020%20QG&packed_desig=K20Q00G  
> **username_0**: Oh 2020-08-16, yikes! What is H=29.8?  
> **username_4**: @uhoh Absolute magnitude based on 1 AU from both Earth and Sun, and opposition phase.  
> **username_0**: Thank for the edit, I wish I could upvote twice! SE doesn't generate notifications to the asker when answer posts are updated, but I saw this in the active queue and now see that you've updated.  
> **username_4**: [2020 VT4](https://minorplanetcenter.net/db_search/show_object?object_id=K20V04T) is another close one, but I'd rather not keep revising this answer.  

---

