New Horizons parallax experiment observes an alien sky
NASA’s New Horizons spacecraft, now over 4.3 billion miles (6.9 billion km) from Earth, successfully imaged two nearby stars displaced from the locations in the sky where they are seen from Earth in its April stellar parallax experiment.
Parallax is the displacement of the apparent position of an object when viewed along two different lines of sight. It is measured by the angle between those two lines. Stars’ positions shift as Earth travels around the Sun, but these shifts cannot be seen with the naked eye because the stars are so far away.
In the experiment, conducted on April 22-23, New Horizons aimed its long range telescopic camera at the two stars closest to the solar system–Proxima Centauri, located 4.2 light years away, and Wolf 359, located 7.9 light years away. At the same time, both professional and amateur astronomers on Earth viewed and imaged the same stars.
Both are low-mass red dwarf stars. Proxima has about one-eighth the mass of our Sun and is approximately 4.85 billion years old. Wolf 359 has 0.09 times the mass of the Sun and is less than one billion years old.
Proxima Centauri was imaged from the Southern Hemisphere while Wolf 359 was imaged in the Northern Hemisphere. When the images taken from the spacecraft and those taken from Earth are combined, the stars’ positions visibly shift.
New Horizons is now so far from the Earth that its images of these two stars show them to be in slightly different locations than those taken at the same time from Earth. This is why the two stars seem to “jump” and “float” in front of the background star field when both sets of images are overlaid on one another.
“It’s fair to say that New Horizons is looking at an alien sky, unlike what we see from Earth. And that has allowed us to do something that had never been accomplished before–to see the nearest stars visibly displaced on the sky from the positions we see them on Earth,” explained New Horizons principal investigator Alan Stern of the Southwest Research Institute (SwRI) in Boulder, Colorado.
New Horizons science team member Tod Lauer of the National Science Foundation‘s (NSF) National Optical-Infrared Astronomy Research Laboratory, noted, “The New Horizons experiment provides the largest parallax baseline ever made–over four billion miles–and is the first demonstration of an easily observed stellar parallax.”
Astrophysicist and Queen lead guitarist Brian May worked with Lauer to create the combined images, including an animation that blinks back and forth between the stars’ two apparent positions, using astro-spectroscopy, which involves creating 3D images of astronomical objects. The spacecraft previously captured 3D images of both Pluto and its second target, KBO Arrokoth.
“These photographs of Proxima Centauri and Wolf 359–stars that are well known to amateur astronomers and science fiction aficionados alike–employ the largest distance between viewpoints ever achieved in 180 years of spectroscopy,” May emphasized.
Proxima Centauri and Wolf 359 were imaged from Earth by one science team via Las Cumbres Observatory‘s remotely operated telescope, located at Australia’s Siding Spring Observatory and by another team who remotely operated a telescope at Arizona’s Mount Lemmon Observatory.
“The professional and amateur astronomy communities had been waiting to try this and were very excited to make a little space exploration history. The images collected on Earth when New Horizons was observing Proxima Centauri and Wolf 359 really exceeded my expectations,” Lauer stated.
The two sets of stellar measurements combined also gave scientists New Horizons‘ exact position in the Kuiper Belt, confirming that stellar positions can be used for interstellar navigation much like they have been used by for thousands of years by navigators to identify their positions on Earth.
Proxima Centauri, the nearest star to the Sun, is orbited by two planets. Two candidate planets apparently orbiting Wolf 359 have yet to be confirmed.
According to Stern, the stellar parallax experiment was conducted largely for the purpose of public outreach and engagement rather than for scientific research.
With the spacecraft in good health, the mission team plans to begin searching this summer for a third flyby target.
Images from the experiment, which anyone can use to create their own view of parallax, are available for viewing and download at the project’s website.
Laurel Kornfeld is an amateur astronomer and freelance writer from Highland Park, NJ, who enjoys writing about astronomy and planetary science. She studied journalism at Douglass College, Rutgers University, and earned a Graduate Certificate of Science from Swinburne University’s Astronomy Online program. Her writings have been published online in The Atlantic, Astronomy magazine’s guest blog section, the UK Space Conference, the 2009 IAU General Assembly newspaper, The Space Reporter, and newsletters of various astronomy clubs. She is a member of the Cranford, NJ-based Amateur Astronomers, Inc. Especially interested in the outer solar system, Laurel gave a brief presentation at the 2008 Great Planet Debate held at the Johns Hopkins University Applied Physics Lab in Laurel, MD.