asteroid close encounter

[KerbMav]

http://www.itelescope.net/sky-alerts

http://en.wikipedia.org/wiki/(357439)_2004_BL86

(357439) 2004 BL86, provisionally known as 2004 BL86, is a near-Earth asteroid estimated to be 0.440–1 km (0.3–0.6 mi) in diameter that will pass 3.1 lunar distances (1.2 million km) from Earth on 26 January 2015 at 16:20 UT.[1][5] It was discovered on 30 January 2004 by LINEAR.[2]

[Aethon]

And it's got it's own moon!


http://www.nasa.gov/jpl/asteroid-that-flew-past-earth-today-has-moon/index.html#.VMbBnf7F-Yc Edited January 26, 2015 by Aethon

[rtxoff]

I higly doubt that this roid has enough gravity to have a moon. Please correct me if i am wrong.

[Kryten]

The absolute size of the body doesn't matter, only the relative sizes of body and satellite. You could give a dust grain a moon if you were careful enough.

[Bill Phil]

That's no moon...

It's a dwarf moon.

Dramatic Music!!!!

[Hal]

That's no moon...

It's a dwarf moon.

Dramatic Music!!!!

Hehe.

Seriously though, that moon can't be that stable. You'd think even the force from the light of the sun (that they thought was causing the Pioneer Anomaly, I think) would overpower that feeble gravitational attraction soon enough. Maybe even tiny variations in drag from space dust. Cool though.

[r4pt0r]

more details on the asteroid and its moon

[brdavis]

Hehe.Seriously though, that moon can't be that stable.

Actually, it can be stable for at least millions to tens of millions of years. Gravity… works. Yes, there are perturbing forces photon pressure is way too small, and even the Yarkovsky Effect isn't going to be significant here… let alone dust blasting). There are a significant number of asteroids that are already known to have moons - this one joins a growing list.

[magnemoe]

Hehe.

Seriously though, that moon can't be that stable. You'd think even the force from the light of the sun (that they thought was causing the Pioneer Anomaly, I think) would overpower that feeble gravitational attraction soon enough. Maybe even tiny variations in drag from space dust. Cool though.

In the article above it stand that moons around asteroids are common who indicate that its stable. Solar wind is not enough to disrupt even the asteroid moon, if the asteroids are similar size it would affect two very tiny asteroids equal over time.

[KerbMav]

Could the close encounter with earth influence its orbit?

[brdavis]

The orbit of what? Of the asteroid around the Sun? Yes, and they take that into account in making future predictions. The orbit of the satellite around the asteroid? No, because only the tidal effects of the Earth on the asteroid-satellite system would matter there, and the distance between the asteroid and its satellite is much much much smaller than the distance between the two of them and the Earth.

I wonder if we have the asteroidal mass from this observation (or at least some rough bounds). Satellite stability is roughly based on the Hill Sphere (if you aren't playing KSP anyway), so with the mass of the asteroid you could figure out just how close it would have to get to Earth to disrupt the satellite orbit… or, conversely, you could note that it's never gotten closer to Earth than XXX kilometers based on the observation that the satellite is still there.

[Newt]

The mass can be calculated by the orbit of its moon. Otherwise, I think generally it would be volumexdensity the latter of which is derived from the spectrum, which identifies the asteroid's class.

Also, a Beyond Apollo Article on the subject, if anyone is interested.

[Scotius]

That asteroid is surprisingly circular. I expected something more...potato-like

[LordFerret]

Could the close encounter with earth influence its orbit?

The ephemeris is available at NASA if you wish to plug it into, say, Celestia. It is a tracked object, so any changes will be published. It will be many years before it visits Earth so closely again. The ephemeris was available before the asteroid even passed, as was the knowledge it had a moon. It is not uncommon for asteroids to have such moons, the asteroid belt is full of them.

http://echo.jpl.nasa.gov/asteroids/2004BL86/2004BL86_planning.html

[lajoswinkler]

Using 4 Vesta's density, I've calculated that the force between those two bodies is roughly 10.3 kN, which is a force an object with the mass of 1047 kg would act on the surface of Earth. That's the mass of a very small car. Indeed a small force, but sufficient to overcome any photon pressure, etc.