Astronomers have captured an unprecedented image of a cosmic recycling project in progress — fragments of a dying star being busted up, stripped, and absorbed into interstellar space.
What you need to know
What is the Helix Nebula?
The Helix Nebula, also known as Caldwell 63, is a planetary nebula located 650 light-years from Earth, in the constellation of Aquarius. It is one of the closest planetary nebulae and has about the same apparent size as the full moon in the sky.
What is the MOTHRA Telescope?
MOTHRA (the Modular Optical Telephoto Hyperspectral Robotic Array) combines images from hundreds of telephoto lenses to detect and study diffuse ionized gas located in-between galaxies. It is being constructed at the El Sauce Observatory in Chile’s Rio Hurtado Valley and will have an array of 1,140 telephoto lenses when completed.
A research team led by Yale astronomer Pieter van Dokkum made the discovery while taking images of the Helix Nebula, a much-studied planetary nebulae located about 650 light-years from Earth. The researchers presented their findings in a new study published Aug. 12 in the journal Nature.
“We are seeing material shed near the end of a star’s life being broken apart and returned to the galaxy,” said Pieter van Dokkum, the Sol Goldman Family Professor of Astronomy and professor of physics in Yale’s Faculty of Arts and Sciences and lead author of the study. He is also a member of the Dragonfly Focused Research Organization, a new type of nonprofit group that aims to build high-impact scientific infrastructure at the pace of a tech startup.
“That handoff — from recognizable stellar debris to the diffuse gas between the stars — has been very difficult to observe,” van Dokkum said. “Far in the future, the Sun will go through a similar process, and its material will enter the same cycle.”
This illustration shows how the Helix Nebula formed and how a bow shock forms around a fragment of its outer shells. At the end of the visualization, the MOTHRA image appears. (Animation credit: Alexandre Dizeux and Dragonfly FRO)
The researchers made the discovery quite by accident. They had chosen the Helix Nebula as a good spot to calibrate their new MOTHRA telescope, which combines images from hundreds of telephoto lenses to detect and study diffuse ionized gas located in-between galaxies. MOTHRA (the Modular Optical Telephoto Hyperspectral Robotic Array) is being constructed at the El Sauce Observatory in Chile’s Rio Hurtado Valley and will have an array of 1,140 telephoto lenses when completed.
“We thought we were taking a calibration image of one of the best-known nebulae in the sky,” said study co-author Roberto Abraham, of the Dragonfly Focused Research Organization and the University of Toronto. “Instead, we found this extraordinary network of bow-shaped structures. It was immediately clear that the faint outer Helix was telling us a story that had largely been missed.”
The Helix Nebula is characterized by a bright ring formed from material expelled by a dying white dwarf star in the center. The new observations reach far beyond that bright inner nebula, into an extraordinarily faint, outer halo. There, on the eastern side of the Helix Nebula, the researchers found 22 complete or partial “bow shocks.”
The Helix Nebula and the cosmic recycling of stellar material. The bright central nebula surrounds a white dwarf, the remnant of the star that created it. Farther out, newly revealed bow shocks show fragments of material cast off by that star colliding with surrounding interstellar gas. The fragments become progressively smaller and more disrupted as they are stripped, shredded and mixed into space. The new MOTHRA data is shown in black, with previous data from the Hubble Space Telescope and the Kitt Peak 4m telescope in color.
A bow shock is similar in shape to the wave that forms in front of a boat moving through water. In the Helix Nebula, mostly invisible clumps of stellar debris are moving rapidly through the thin gas between stars. The glowing arcs mark where those clumps collide with the surrounding gas.
The shocks change strikingly with distance from the central star. Those nearer the center are large, thin and sharply defined. Farther out, they become smaller, fuzzier, and increasingly fragmented.
The researchers interpret that progression as evidence that the clumps are being steadily eroded as they travel. They estimate that an individual fragment remains coherent for only about 10,000 years once it is exposed to the surrounding gas. After that, its material is largely shredded and mixed into interstellar space.
“This is only the beginning of what we’ll be able to see with MOTHRA,” van Dokkum said.
MOTHRA stands as a major expansion of concepts that van Dokkum and Abraham first incorporated into their earlier Dragonfly Telescope. That telescope, located in the mountains of New Mexico, combines images from multiple lenses to detect the dim glow of faint stars and galaxies.
MOTHRA will dramatically increase the number of lenses being used, along with new filters and computational power.
The new research was funded and supported by Alex Gerko, the founder and CEO of the algorithmic trading firm XTX Markets.
