Comments on: New Horizons sees stellar parallax

By: Phill O

Phill O — Sat, 13 Jun 2020 02:21:34 +0000

sippin_bourbon

“get a completely accurate measure?”

Basic trigonometry combined with the telescope’s resolution are the important items.

The resolution defines how much of an apparent shift can be measured. Resolution is a function of lens diameter, local “seeing” (outerspace has much less turbulence and better seeing) and the detector. A photographic emulsion tends to have less resolution than state of the art CCDs.

Consider a triangle with a very short base compared to the length. The length is the distance to the object. The base is the distant between where the two measurements were taken. On earth, we can have a maximum of 2au as he base. New Horizons is past Pluto so your 42 au seems about right. The longer the base, the larger the apparent shift and the easier it is to “see” the shift.

Now we come to what one defines as accurate. I like the term precision the best for this discussion. The closer the object the lower the relative error in the system of measurement. Accuracy is how close to the real value. In chemical measurement, we use interlaboratory comparison samples to help define what the true value is. We never know it, but make our est estimate from the results of several measurement systems, personnel and laboratories.

The topic of the propagation of error deals much more in-depth, but I hope this gives a reasonable idea of the problem f accuracy and precision.

By: sippin_bourbon

sippin_bourbon — Sat, 13 Jun 2020 01:07:15 +0000

So If I am doing the math right, over 43 AU difference in perspective was needed for these images.

Someone wanna correct me?

So simply taking coordinated images from different points within the inner solar system is not enough to get a completely accurate measure?

By: Phill O

Phill O — Fri, 12 Jun 2020 14:47:39 +0000

To reach the 10,000 light year limit, enhanced computer data manipulation is required. I think that an obvious shift would require a distance of less than 100 light years, However, MDN, you bring out a great point in that what had been stars which were thought distant, new criteria for distant star will be required. A complete sky survey is required; rather like a recalibration!

By: MDN

MDN — Fri, 12 Jun 2020 14:27:50 +0000

What I find interesting is that there is no obvious parallax shift among any other stars visible, giving a sense of just how big space really is.

By: Robert Zimmerman

Robert Zimmerman — Fri, 12 Jun 2020 05:49:12 +0000

In reply to Ray Van Dune. Ray Van Dune: The link is in the first line of this post, taking you to the press release.

By: Ray Van Dune

Ray Van Dune — Fri, 12 Jun 2020 05:05:07 +0000

What link? It isn’t showing as a link for me.

By: Phill O

Phill O — Fri, 12 Jun 2020 02:09:59 +0000

Prior to space telescopes and/or adaptive optics, I believe that the practical limit for accurate distances with parallax, was about 100 light years. Space telescope and adaptive optics (and CCD with computer technology) pushed this limit to 1000 light years. Pluto at elongation is about 50 au from the sun so the practical limit for accurate measurements should be pushed to about 50,000 light years (ceteris paribus).

Other things are not equal as the mirror (or lens) size on the spacecraft is significantly smaller than say Hubble.

However, this is a big leap forward in distancing stars. If New Horizons was dedicated to just this field, it would be great.