APOD: 2012 VP113: A New Furthest Known in... (2014 Mar 31)

[who?me?]

[..]
To achieve its mission the spacecraft is spinning slowly, sweeping its two telescopes across the entire celestial sphere to make four complete rotations per day. Gaia’s telescopes point at two different portions of the sky, separated by a constant 106.5°. Therefore, objects arrive in the second field of view 106.5 minutes after they are observed in the first.

[..]

Huh? Wouldn't that be 106'30" * 240 minutes / 360' = 71 minutes?

[Chris Peterson]

[..]
To achieve its mission the spacecraft is spinning slowly, sweeping its two telescopes across the entire celestial sphere to make four complete rotations per day. Gaia’s telescopes point at two different portions of the sky, separated by a constant 106.5°. Therefore, objects arrive in the second field of view 106.5 minutes after they are observed in the first.

[..]

Huh? Wouldn't that be 106'30" * 240 minutes / 360' = 71 minutes?

It makes one complete revolution in 1/4 day. Its rotation rate is 360° x 4 / day, or 1° per minute. If the orientation is such that the two telescopes sweep the same line through the sky (which is the case), a 106.5° separation means a 106.5 minute difference.

[neufer]

[b][color=#0000FF]Census taker visits a Romani family living in a caravan, Netherlands 1925[/color][/b]

---

What will it take to get a reasonably complete census of our Sun’s planetary family?

Gaia (with its magnitude +20 sensitivity)
should do a good senseless census job for:

• 1) Earth sized objects closer than 400 AU
  2) 32⁺ km diameter Centaurs at around 20 AU and
  3) 80⁺ m diameter Apohele asteroids between Earth and the Sun

It will certainly add to the data. But it doesn't come close to allowing a complete statistical census of the Solar System.

<<A census is the procedure of systematically acquiring and recording information about the members of a given population. The word is of Latin origin; during the Roman Republic, the census was a list that kept track of all adult males fit for military service.

A census is often construed as the opposite of a sample as its intent is to count everyone in a population rather than a fraction. However, population censuses relies on a sampling frame to count the population. This is the only way to be sure that everyone has been included as otherwise those not responding would not be followed up on and individuals could be missed. The fundamental premise of a census is that the population is not known and a new estimate is to be made by the analysis of primary data.>>

[Chris Peterson]

<<A census is the procedure of systematically acquiring and recording information about the members of a given population. The word is of Latin origin; during the Roman Republic, the census was a list that kept track of all adult males fit for military service.

A census is often construed as the opposite of a sample as its intent is to count everyone in a population rather than a fraction. However, population censuses relies on a sampling frame to count the population. This is the only way to be sure that everyone has been included as otherwise those not responding would not be followed up on and individuals could be missed. The fundamental premise of a census is that the population is not known and a new estimate is to be made by the analysis of primary data.>>

I think my meaning was clear. But if you'd prefer, I can say that Gaia will not provide an adequate sampling frame to allow us to count the members of the Solar System.

[neufer]

Does the Sun have rings?

Both the Main Asteroid Belt and Kuiper Belt might be viewed as Rings around the Sun with Jupiter and Neptune as shepherding Planets maintaining their respective Outer and Inner boundaries anthough they are more Toroids than Rings

• The Sun can be said to have multiple rings; e.g.:

[img3="The Vesta or Vestian family of asteroids is a large & prominent grouping of mostly V-type asteroids ("vestoids") in the inner asteroid belt in the vicinity of 4 Vesta."]http://upload.wikimedia.org/wikipedia/c ... family.png[/img3]

<<The Vestian asteroids consist of 4 Vesta, the second-most-massive of all asteroids (mean diameter of 530 km), and many small asteroids below 10 km diameter. The brightest of these, 1929 Kollaa and 2045 Peking, have an absolute magnitude of 12.2, which would give them a radius of about 7.5 km assuming the same high albedo as 4 Vesta. The family originated from an impact on asteroid 4 Vesta, with the giant south-polar crater the likely impact site. The family are thought to be the source of the HED meteorites. The Vesta family also includes a few J-type asteroids (related to the V-type), which are thought to have come from the deeper layers of Vesta's crust, and are similar to the diogenite meteorites. In August 2007, a study of zircon crystals in an Antarctic meteorite believed to have originated from 4 Vesta suggested that it, and by extension the rest of the asteroid belt, had formed rather quickly, within ten million years of the Solar System's origin.

The Zappala 1995 analysis found 235 core members. A search of a recent proper-element database (AstDys) for 96944 minor planets in 2005 yielded 6051 objects (about 6% of the total) lying within the Vesta-family region.>>

[Chris Peterson]

The Sun can be said to have multiple rings;

No, it can't. There's no reasonable justification to call the asteroid belt (or components of the asteroid belt) rings. Likewise for the scattered disc, or anything else. Three things characterize ring systems: high density, very high radius-to-thickness ratio, and zero-eccentricity components. Nothing in the Solar System comes close to having those features with respect to the Sun.

[Anthony Barreiro]

The text should make clear that it is the furthest known perihelion.

OK I updated the text again (but not the title). The second sentence now makes "orbit" more clear, in the context of the explanation and title, by starting "In terms of how close it will ever get to the Sun..."

- RJN

That makes sense. It must be difficult to write brief captions that are engaging and accessible to a casual reader without any specialized knowledge or jargon, but that will also stand up to the scrutiny of readers armed with an abundance of both knowledge and jargon.

[neufer]

That makes sense. It must be difficult to write brief captions that are engaging and accessible to a casual reader without any specialized knowledge or jargon, but that will also stand up to the scrutiny of readers armed with an abundance of both knowledge and jargon.

• 
  Which is why the world still has mountain sanatoriums
  (where one can still view the Milky Way from one's own back yard).
  http://asterisk.apod.com/viewtopic.php? ... 56#p222356

[ronherren]

Ok, so if the distance we can see is increasing, all we know for certain is that there are objects at those distances that give off light. Maybe it tells us when we were created, but has no bearing on when the universe became.

[Nitpicker]

Ok, so if the distance we can see is increasing, all we know for certain is that there are objects at those distances that give off light. Maybe it tells us when we were created, but has no bearing on when the universe became.

I was with you right up to the first comma.

[metamorphmuses]

{snip}it's actually for farthest perihelion.{snip}

... a while back, and then it had to be hashed out back and forth anyway...

[neufer]

{snip}it's actually for farthest perihelion.{snip}

... a while back, and then it had to be hashed out back and forth anyway...

There is still the debate on whether it is the farthest perihelion or the furthest perihelion.

[MargaritaMc]

It must be difficult to write brief captions that are engaging and accessible to a casual reader without any specialized knowledge or jargon, but that will also stand up to the scrutiny of readers armed with an abundance of both knowledge and jargon.

RJN has posted recently regarding this in the Handbook
http://asterisk.apod.com/viewtopic.php?f=28&t=33201