3 minutes ago, Bmpbmp1975 said:

Sorry this article said 4.1 km asteroid 

https://www.google.ca/amp/s/www.express.co.uk/news/science/1249990/Asteroid-warning-NASA-tracks-4KM-killer-asteroid-hit-Earth-end-civilisation-asteroid-news/amp

Yep, exactly what I suggested: "is estimated measure up 2.5 miles (4.1km) across" so exactly the same size as the other sources,

23 minutes ago, Strange said:

Yep, exactly what I suggested: "is estimated measure up 2.5 miles (4.1km) across" so exactly the same size as the other sources,

Ok so it’s 2.5 miles and not 2.1 km

 

Edited March 31, 20205 yr by Bmpbmp1975

6 hours ago, Bmpbmp1975 said:

Sorry this article said 4.1 km asteroid

If language and skills are an issue they could maybe confuse size with period. The period* is approximately 4.1 according to @Strange's sources. 

 

 

*) Rotational period is of course not a measure of size of celestial body, the numerical value just happened match.

8 hours ago, Bmpbmp1975 said:

Ok so it’s 2.5 miles and not 2.1 km

Yes. But that isn't the point.

The radius is 2.1 km. This article says it is 4km across (in other words the diameter is 4 km = twice the radius).

Sorry. I'm wrong. They are all referring to the diameter. So I have no idea why they have the wrong number. 

Maybe you are right and they confused miles and km. Or maybe Ghideon is right and they copied the wrong number.

Or maybe they got the number from an old version of the Wikipedia article:

Quote

(52768) 1998 OR₂, provisional designation 1998 OR₂, is an asteroid on an eccentric orbit, classified as near-Earth object and potentially hazardous asteroid of the Apollo group, approximately 4 kilometers in diameter.

https://en.wikipedia.org/w/index.php?title=(52768)_1998_OR2&oldid=943951338

The size in that paragraph has bounced around all over the place, for no obvious reason. 

1 hour ago, Strange said:

Or maybe they got the number from an old version of the Wikipedia article:

Good find!

Here is the change from "4" to "2-4".

https://en.wikipedia.org/w/index.php?title=(52768)_1998_OR2&oldid=944085138

Quote

diameter of 2–4 kilometers. 

If better estimates if the object diameter was available and caused the update I do not know (yet). Or if there was just an error and a correction in Wikipedia article.

 

Edited April 1, 20205 yr by Ghideon
spelling

On 3/29/2020 at 11:42 PM, Strange said:

The Express is not the worst tabloid in the UK. But I certainly wouldn't use it as a source of reliable information. 

Why not? Because it is a British tabloid.

Factcheck alert:

From Grauniad tabloid: size matters, but not as much as content:

Philippa Clarke said

Quote

My aunt maintains that she buys the Mail because it fits the cat’s litter tray. Now perhaps she will improve her reading habits.

 

"Asteroid (52768) 1998 OR2 will make a close approach to Earth on April 29. The hefty space rock has an estimated diameter of 1.1 to 2.5 miles (1.8 to 4.1 kilometers)"

https://www.space.com/asteroid-1998-or2-earth-flyby-april-2020.html

NASA has that range of values, too

It's possible that the people quoting a diameter are using one of the endpoint values in that range. Some may be choosing the bigger value because that sensationalizes the reporting.

P.S. It wasn't hard to find better sources than The Express.

2 hours ago, Carrock said:

Factcheck alert:

We are going to need a new word to distinguish between "tabloid format" newspapers and "tabloid so-called 'newspapers'" that will print any old populist trash, regardless of the truth, as long as it sells.

5 hours ago, swansont said:

The hefty space rock has an estimated diameter of 1.1 to 2.5 miles (1.8 to 4.1 kilometers)"

Or maybe, it's twice as long in one axis, than the other two...

43 minutes ago, MigL said:

Or maybe, it's twice as long in one axis, than the other two...

AFAIK the size was determined by the amount of light detected, not from resolving an image. If you look at the estimated diameter in the NASA link, all of those asteroids have diameter estimates that are just a bit more than a factor of two from the low end to the high end (it's the square root of 5) which is because they use albedo values of 0.05 to 0.25 (it says so in the hover tag on 'diameter') to estimate the size. So that range is an error bar.

If it had a decidedly non-spherical shape, you'd expect oscillations in the amount of light detected, and one might expect that to be reported.