Thanks for the response. I am aware of the various pieces of hardware you mention, and their capabilities and missions. What I was responding to (and apparently misunderstanding) was Phil’s statement in the post that the pixilated image shown was somehow generated with the FGS and that it was resolving at that incredible level. If it was measuring redshift or some other spectrum changes to generate that image, than obviously it wouldn’t work on an object sitting on the moon since the object and the background are moving together. What caught my eye, obviously, was the analogy to a car on the moon, which there actually are several of.

- Jack

PS – Sorry about ending that last sentence with a preposition…

“We still don’t know if there’s a planet around the nearest known star, which is kinda funny:”

There are eight of them, now that Pluto’s been relegated…..

Have you ever played a computer game called Star Control II (Accolade, 1992)? It depicts Alpha Centauri as a red supergiant. It’s astronomy is mostly the Bad variety… However, I still remember myself laughing for gas giants in the game that had temperatures over 1000 kelvins. Such planets were considered impossible–but that was before 51 Pegasi b!

Alpha Centauri is the third brightest star in the sky. The only reason for this is that it is so darn close! Put it at the distance of, say, 20 light years and it wouldn’t be hardly notable: It would be slightly brighter than its analogue Eta Cassiopeiae, a star between the second and third star as counted from right in Cassiopeia’s W.

Jack Hagerty: Could the FGS be used to image them, like the HiRISE images of the rover on Mars last week?

No way. Firstly, FGSs are not cameras. Secondly, Hubble can’t resolve objects smaller than 100 m (IIRC) from the surface of the Moon because it is so distant. The orbital distance of Mars Reconnaissance Orbiter from Mars was less than 300 km when it photographed Opportunity. That is more than 1000 times closer.

A car on the moon? Didn’t we leave three “buggies” up there from Apollos 15, 16 and 17? Could the FGS be used to image them, like the HiRISE images of the rover on Mars last week? The Russian’s have a couple of similar-sized Lunikods as well. The LM descent stages are larger still.

- Jack

I did not know the disk theory didn’t have direct evidence of it.
Well, does now.

At least no creationists have come over to argue their case against this, like last time.

GAry 7

The only reason for this is the mass. Alpha Cen A is slightly more massive than the Sun, which is slightly more massive than Alpha Cen B, which in turn is much more massive than Proxima.

A’s habitable zone (HZ) is larger than Sun’s and B’s HZ smaller; it is interesting that both HZs are stable, so both stars can have habitable planets.

Proxima’s habitable zone is indeed small and very close to the star. Nearby, strong stellar flares and the fact that a closely orbiting planet turns same face towards its star may be problematic in the case of Proxima, but some studies suggest that even these factors don’t necessarily make a planet unhabitable.

The star under discussion is Alpha Centauri B, a type K0 main sequence star slightly smaller, cooler and dimmer than the Sun.

I do not know why B instead of A, but I guess B may be chromospherically quieter.

Since Proxima is likely a member of the system, it has the same metallicity as the two larger stars and therefore is a good candidate for having planets.

Right.

BUT if we build a telescope that stares only Alpha Centauri B and measures its radial velocities for a few years collecting tens of thousands of data points, we could soon know if there is a terrestrial planet with the mass of Mars orbiting in the habitable zone!

For more, see http://oklo.org/?p=117 and some later blog entries.

How much would it cost? Well, the recent discovery of planets in the galactic bulge required seven days of Hubble observations, in other words it cost millions of dollars. A telescope like this could be cheaper.

By the way, Epsilon Eridani is not the only planetary system with a known disk–a few others systems are known to have one. However, it seems to be the only nearby star with a planet in a relatively distant orbit.

incidentally, the FGS data indicate the possible presence of another planet with a 50 – 100 year period that remains otherwise undetected as yet

Actually, the existence of second planet was first (?) infrerred from the shape of the dust disk. Some further evidence comes from the radial velocity measurements. However, its orbital period is far too long to be confirmed with radial velocity measurements.

We still don’t know if there’s a planet around the nearest known star, which is kinda funny: we know a lot about a planet more than twice as far away.

I think the most amazing thing is that we don’t know if Alpha Centauri system has any planets but we know that there is a frozen giant terrestrial planet orbiting a red dwarf star 21,000 light years away!

Especially since, technically, it wouldnt’ be a planet. Woot.