New Horizons sees stellar parallax
New Horizons is now far enough away from Earth that its perspective of the universe shifts at least two nearby stars into slightly different positions than seen on Earth.
On April 22-23, the spacecraft turned its long-range telescopic camera to a pair of the closest stars, Proxima Centauri and Wolf 359, showing just how they appear in different places than we see from Earth. Scientists have long used this “parallax effect” – how a star appears to shift against its background when seen from different locations — to measure distances to stars.
An easy way to see parallax is to place one finger at arm’s length and watch it jump back and forth when you view it successively with each eye. Similarly, as Earth makes it way around the Sun, the stars shift their positions. But because even the nearest stars are hundreds of thousands of times farther away than the diameter of Earth’s orbit, the parallax shifts are tiny, and can only be measured with precise instrumentation. “No human eye can detect these shifts,” Stern said.
But when New Horizons images are paired with pictures of the same stars taken on the same dates by telescopes on Earth, the parallax shift is instantly visible. The combination yields a 3D view of the stars “floating” in front of their background star fields.
The resulting 3D image, available at the link, is very cool. Both stars clearly appear closer than the surrounding background stars, which of course is true as they are among the closest stars to the Sun.
On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.
The print edition can be purchased at Amazon or from any other book seller. If you want an autographed copy the price is $60 for the hardback and $45 for the paperback, plus $8 shipping for each. Go here for purchasing details. The ebook is available everywhere for $5.99 (before discount) at amazon, or direct from my ebook publisher, ebookit. If you buy it from ebookit you don't support the big tech companies and the author gets a bigger cut much sooner.
The audiobook is also available at all these vendors, and is also free with a 30-day trial membership to Audible.
"Not simply about one mission, [Genesis] is also the history of America's quest for the moon... Zimmerman has done a masterful job of tying disparate events together into a solid account of one of America's greatest human triumphs."--San Antonio Express-News
New Horizons is now far enough away from Earth that its perspective of the universe shifts at least two nearby stars into slightly different positions than seen on Earth.
On April 22-23, the spacecraft turned its long-range telescopic camera to a pair of the closest stars, Proxima Centauri and Wolf 359, showing just how they appear in different places than we see from Earth. Scientists have long used this “parallax effect” – how a star appears to shift against its background when seen from different locations — to measure distances to stars.
An easy way to see parallax is to place one finger at arm’s length and watch it jump back and forth when you view it successively with each eye. Similarly, as Earth makes it way around the Sun, the stars shift their positions. But because even the nearest stars are hundreds of thousands of times farther away than the diameter of Earth’s orbit, the parallax shifts are tiny, and can only be measured with precise instrumentation. “No human eye can detect these shifts,” Stern said.
But when New Horizons images are paired with pictures of the same stars taken on the same dates by telescopes on Earth, the parallax shift is instantly visible. The combination yields a 3D view of the stars “floating” in front of their background star fields.
The resulting 3D image, available at the link, is very cool. Both stars clearly appear closer than the surrounding background stars, which of course is true as they are among the closest stars to the Sun.
On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.
The print edition can be purchased at Amazon or from any other book seller. If you want an autographed copy the price is $60 for the hardback and $45 for the paperback, plus $8 shipping for each. Go here for purchasing details. The ebook is available everywhere for $5.99 (before discount) at amazon, or direct from my ebook publisher, ebookit. If you buy it from ebookit you don't support the big tech companies and the author gets a bigger cut much sooner.
The audiobook is also available at all these vendors, and is also free with a 30-day trial membership to Audible.
"Not simply about one mission, [Genesis] is also the history of America's quest for the moon... Zimmerman has done a masterful job of tying disparate events together into a solid account of one of America's greatest human triumphs."--San Antonio Express-News
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.
What link? It isn’t showing as a link for me.
Ray Van Dune: The link is in the first line of this post, taking you to the press release.
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.
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!
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?
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.