Back in January — and boy does that seem like another era — I wrote about the plan to look at two nearby stars with the help of the New Horizons spacecraft as well as observations from the general public. If you’d like to get involved, there is still time, but the date is fast approaching. Amateur equipment and digital cameras have reached the point where astronomy at a very high level can be conducted from small observatories and even back yards. Here’s another chance to make the case for the value of such work.
Tha planned observations take advantage of parallax, the apparent shift in position of nearby stars as measured using the radius of the Earth’s orbit. Friedrich Bessel’s groundbreaking work on stellar distances involved taking such measurements to calculate the distance of 61 Cygni, all this back in 1838. The apparent shift of the star against background stars allowed him to peg 61 Cygni’s distance at 10 light years, reasonably close to the modern figure of 11.4.
New Horizons gives us a baseline extending all the way to the Kuiper Belt. By the time we take the upcoming observations of Proxima Centauri and Wolf 359, the spacecraft will be 46 times farther from the Sun than Earth (some 8 billion kilometers out). Combining the New Horizons data with Earth-based images made on April 22 and 23 will yield a record-setting parallax measurement as the two stars seem to shift in position against the background.
“These exciting 3D images, which we’ll release in May, will be as if you had eyes as wide as the solar system and could detect the distance of these stars yourself,” said New Horizons Principal Investigator Alan Stern, of the Southwest Research Institute, Boulder, Colorado. “It’ll be a truly vivid demonstration of the immense distance New Horizons has traveled, and a cool way to take advantage of the spacecraft’s unique vantage point out on the very frontier of our solar system!”
Image: This figure illustrates the phenomenon of stellar parallax. When New Horizons and observers on Earth observe a nearby star at the same time, it appears to be in different places compared to more distant background stars — this is because New Horizons has traveled so far out in space that it has to look in a different direction to see that star. The small images below Earth and New Horizons show each unique view. Note that the farther-away background stars stay in the same place, but the nearby star appears to move between the two vantage points. Credit: Pete Marenfeld, NSF’s National Optical-Infrared Astronomy Research Laboratory.
Those wishing to participate will need a camera equipped telescope with 6-inch aperture or larger. To learn more, click here. Proxima Centauri is 4.244 light years away, a distant companion to the primary Centauri A and B stars. It’s also at quite a large angle in the sky from Wolf 359, making both stars a useful reference as the team explores autonomous interstellar navigation. Robotic missions within the Solar System have used optical imagery for navigation before, but New Horizons takes the technique into interstellar trajectories as it heads out ever deeper into the Kuiper Belt. Thus New Horizons science team member Tod Lauer:
“For all of history, the fixed stars in the night sky have served as navigation markers. As we voyage out of the solar system and into interstellar space, how the nearer stars shift can serve as a new way to navigate. We will see this for the first time with New Horizons.”
Image: This figure, by New Horizons contributing scientist Brian May, shows the parallax as an effect of New Horizons’ travels deeper into the Kuiper Belt. Traditionally, parallax is measured as the Earth orbits around the sun. The two lines at left show the lines of sight from Earth to the star on either side of Earth’s orbit. This causes a small shift in the position of the nearby star compared to more distant stars. New Horizons is so far away that a much larger shift in the line of sight to the star occurs. Credit: Brian May.
As for Wolf 359, it’s a red dwarf 7.9 light years away in Leo. You may recall numerous science fiction references to the star, ranging from “Wolf 359”, an episode on the 60’s TV show The Outer Limits to Harry Harrison’s Captive Universe (1969), a generation ship novel, and a double episode of Star Trek: The Next Generation. More recently, there is the Hugo nominated Ken MacLeod short story “Who’s Afraid of Wolf 359?”
While Proxima Centauri is not visible for most northern hemisphere observers, Wolf 359 should be observable from both hemispheres with telescopes of sufficient aperture. Star charts of the Wolf 359 and Proxima Centauri fields are available at the project site.
Is there a plan to go beyond this first demonstration to make a better measurement of a useful astrophysical object such as a Cepheid variable? The project page doesn’t say. These stars are further distant and a more exact distance measurement could perhaps contribute to refining the cosmic distance scale.
You wondered if this project might attempt to observe parallaxes of Cepheid variables. This is not a project intended to produce real science. It’s just for fun, for public relations. The resolution of the imagers on New Horizons is very low compared even to modern backyard telescopes. While it’s true that the Earth-NH baseline of nearly 50AU will be about 25 times longer than the usual Earth orbit baseline (2AU) for parallax observations, the low resolution completely cancels out that advantage. Compare with the Gaia spacecraft, currently in orbit and reaching the end of its mission. It was designed to observe parallaxes, and it is observing with a resolution something like 10,000x higher than can be achieved using New Horizons images, and it is observing over one billion stars. Parallaxes obtained from New Horizons have nearly zero research value. It’s a nice demo of the earliest parallax observations from the 19th century, now using a very long baseline which can be easily visualized and may provide nice visualizations for students. It’s “play” science, and that’s all.
I feared as much. I know the optics aren’t suited to this task but I thought if they “played” with a bright Cepheid it would inspire substantive interest rather than a brief (more like, non-existent) publicity stunt. Just like the Voyager and Pioneer probes that can be extended to so limited science well beyond their primary missions simply due to where they are. Imagine if even a small and speculative experiment were added to these deep space probes.
I guess that in terms of ultra high precision astrometry – including for extra galactic Cepheid variables – why bother with NH when Gaia is :
1/ Bespoke
2/ Much nearer and more potent and
3/ Cheaper.
Unlike New Horizons and Alan Stern’s best efforts , Gaia also has planets amongst its objectives.
Actually, NH is cheaper ($700M vs $1B for GAIA).
Depends to a degree on the €/$ exchange rate. Which currently favours the dollar. New Horixons is a New Frontiers mission which when allowing for launcher, development and systems engineering /operations costs, tops out at just over a $1 billion. More still for its already substantially extended mission to Arrokoth and beyond.
With a hugely inferior data return. Tens of Gigabytes versus terabytes..
Don’t get new wrong , minor planet / KBO science has an important part to play . But in terms of astrometric capability we are comparing a first day Paduan to Yoda.
The goal is not to measure precise distances, but to demonstrate the concept of parallax vividly in a way that cannot be done otherwise, as well as to demonstrate interstellar navigation, and simply how far NH has gone. No one has ever shown the stars shifting in position because the spacecraft has traveled so far – it would be a shame not to capture that. As superb as Gaia is it takes years to build the data set for analysis, one has to correct for proper motion, and the shifts are vastly too small to visualize by simply showing two images next to each other. Stellar parallax is always demonstrated in diagrams, not real images. We will fix that.
And space missions crucially have always had a public education/adventure component. Plenty of missions from Voyager, Viking, HST, Cassini, the various Mars rovers, Juno, have had demos to do something just for the fun of it. The famed “Pale Blue Dot” of Voyager had nearly zero scientific value, but an immense educational impact.
Well… let’s hope they get lucky and see something transit that wouldn’t be visible from Earth. (But honestly, I have no idea of the star’s rotation axis)
Well actually there could be real value in measuring the parallax for objects whose angular size is bigger than their parallax viewed by Gaia. The parallax to such stars can be screwed up by inhomogeneous atmospheres that move their photocentres, and repeated observations over years cannot really mitigate against this problem. A wider parallax base would give a much more accurate true parallax in these cases. Does anyone know what the positional precision of the New Horizons images are?
Hear, hear! Can we do a TAU-lite mission with NH?
Paradoxically, the current pandemic could aid these amateur observations as the lack of industry and attendant pollution haze is very much diminished allowing for much clearer night skies. It is a pity that this is being offset somewhat by the new swarm satellites like Starlink.
This reminds me of a mystifying news report I ran across, which said that light beams could actually be designed to bend in free space: https://phys.org/news/2019-10-free-space-data-carrying-bendable.html It cites other papers making similar statements. I’m afraid I never got deep enough into the physics to convince myself this was “real” bending as opposed to a “gimmick” only working in an enclosed lab environment.
By which I mean… if this is real, would it be conceivable for an Earth-based laser to be built to produce a “free-space, data-carrying bendable light communication system between arbitrary targets”, which would scan the sky in a circular area around the NH probe, such that all the bent light would veer out for some number of AU in any given direction, then come back into line with the craft and be registered successfully at NH’s detector … unless there were something like Planet Nine exerting enough gravity to disrupt the beam, or of course a small body blocking it directly?
Thanks Paul
Very interesting
You know, this objective could be a quite compelling argument (although probably not just by itself) to design, build, and launch interstellar probes. Such spacecraft, using imagers and astrometry instrumentation (among other instruments for examining their stellar and exoplanetary targets), could–in concert with Earth-based (and satellite-based) observations–provide high-precision data on (relatively) nearby stars’ positions, distances, directions, and velocities through space with respect to the Sun’s. Also:
In the 1960s, a star tracker probe (which would eventually reach and pass through another galaxy, after millions of years) was considered. A picture of a full-scale model of the probe design–with a photograph of the Andromeda galaxy in the space background–was included in a 1964 space encyclopedia book by Erik Bergaust.
I have spread the word about this citizen science project (starting with a link to this article in the notice message, which describes it) to several people I know, and I have also posted the notice message on “Ye Olde Rocket Forum” (see: https://www.oldrocketforum.com/showthread.php?t=18451 ). Hopefully these will attract more participants!
Here’s an extravagant suggestion for a solar system sized baseline parallax mission: Place GAIA next gen class solar orbiters out at Neptune’s L4 and L5 points. Just wishful thinking, but imagine the possibilities…
Better still put your next gen Gaia on steroids at the same locale as Gaia .
A region that can be :
1: Be reached by a relatively small and cheap rocket launcher
2/ Reached by a small , simple and cheap on board satellite bus propulsion system
2/ Reached in just weeks rather than travelling over a decade timeframe twice that of its primary mission
2/ Requires only a straightforward solar array to provide its kilowatt level power supply
Use computers to generate the synthetic large AU baseline images to view the stars in 3D, or create 3D [4D?] models.
There isn’t as much advantage in this as you’d think. Not unless you are only interested in stars at right angles to the velocity of Neptune or are prepared to wait a lifetime for your parallax measurements.
News!
The SOPHIE search for northern extrasolar planets. XVI. HD 158259: A compact planetary system in a near-3:2 mean motion resonance chain.
https://arxiv.org/abs/1911.13296
6 planets in orbit around G0 star, orbiting from 4 to less then 15 million miles!!! Closet a super earth, the 5 others mini Neptunes but I doubt they look anything like Neptune.
https://www.aanda.org/articles/aa/full_html/2020/04/aa37254-19/aa37254-19-fig5.pdf
Paul, I wonder if you can give a write up on this system and how many other G class stars have similar extremely close in planets?
Yes, this one is interesting and on my radar.
A bit of wild speculation: signals from “elsewhere” showing stellar parallax of a star “of interest” with Sol in the background: the sender would be aware of the features of interest in that star, and would have the technology to widen their interpupillary distance.
Hi, I’ve taken images of Proxima Centauri at the requested time but I can’t seem to find a link to upload them. Do you have one?
Try Tod Lauer at lauer@noao.edu. He’s the science team coordinator for the parallax project, and should be able to help.
Yeah, I have the same problem. Where to upload or send the pictures. And in which format?
Very strange that there is not information at all
Brian May? As in THE Brian May?
Yes indeed, THE Brian May.
Where can I find the pictures of Proxima Centauri and Alfa Centauri?