by Aram Friedman

unprecedented parallax measurement

The folks at New Horizon are going to make an unprecedented parallax measurement on April 22nd & 23rd ⁽¹⁾ as reported in a news article by Applied Physics Laboratory of John’s Hopkins University.

They will compare images taken simultaneously from Earth and New Horizons
(47.31 AU or 4.4 billion miles).

Stellar parallax (triangulation) was first successfully accomplished by Friedrich Bessel in 1838 for the star 61 Cygni.

The observation is made from opposite sides of Earth’s orbit (a distance of 2AU).

The drawback of this technique (the only one available) is that the measurement contains proper motion of the stars over the 6 month period and the distance between observations is relatively short, the diameter of Earth’s orbit. In the case of the New Horizons measurement, the images will be taken simultaneously (eliminating proper motion) and the distance between observations is over 4 billion miles.

The red dwarf Proxima Centauri and surrounding star field. Width of field ~28 arc-min, about the size of the full moon. Alpha Centauri is out of the field ~2 degrees away. Image by RAParker using Skynet/PROMPT5.

Color image of the Wolf 359 star field, obtained in late 2019.
Credit: William Keel/University of Alabama/SARA Observatory.
Published on New Horizons, News Article, ibid – NASA/Johns Hopkins APL/Southwest Research Institute.

There are two target stars, Proxima Centauri and Wolf 359. According to Robert Vanderbie we should be able to see Wolf from NJ.

The article from New Horizons claims that a 6” scope is the minimum to see such a dim star. I have never tried, I suppose it depends on the camera used.

It is unclear if the folks at New Horizons are asking for images from the public (I hope they do).

Regardless it would be fun to try.