{"id":797529,"date":"2025-07-30T07:20:07","date_gmt":"2025-07-30T12:20:07","guid":{"rendered":"https:\/\/spaceweekly.com\/?p=797529"},"modified":"2025-07-30T07:20:07","modified_gmt":"2025-07-30T12:20:07","slug":"meet-apep-a-pair-of-dying-stars-in-a-swirling-nebula","status":"publish","type":"post","link":"https:\/\/spaceweekly.com\/?p=797529","title":{"rendered":"Meet Apep, a pair of dying stars in a swirling nebula"},"content":{"rendered":"
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\nThis is Apep, a multiple star system in the direction of the small, southern constellation Norma. Apep is named for an ancient Egyptian deity (Apep, aka Apophis), the embodiment of chaos and darkness. Image via NASA\/ JWST\/ Judy Schmidt.<\/figcaption><\/figure>\n
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Apep is a multiple star system.<\/strong> Surrounding it, there is an intricate, swirling nebula that has intrigued scientists.<\/li>\n
The James Webb Space Telescope has taken a new image of Apep.<\/strong> The image gives astronomers an even better view of what is happening within this star system.<\/li>\n
Two Wolf-Rayet stars lie at the heart of this system,<\/strong> along with a third companion. And the third star is taking a bite out of their dust shells.<\/li>\n<\/ul>\n
By Benjamin Pope, Macquarie University<\/span><\/p>\n
The twisted world of Apep<\/h3>\n
The day before my thesis examination, my friend and radio astronomer Joe Callingham showed me an image we\u2019d been awaiting for five long years. It was an infrared photo of two dying stars we\u2019d requested from the Very Large Telescope in Chile.<\/p>\n
I gasped. The stars were wreathed in a huge spiral of dust, like a snake eating its own tail. We named it Apep, for the Egyptian serpent god of destruction.<\/p>\n\n The European Space Observatory\u2019s Very Large Telescope captured the coils of Apep. Image via ESO\/ Callingham et al., CC BY. <\/figcaption><\/figure>\n
Now, our team has finally been lucky to use NASA\u2019s James Webb Space Telescope to look at Apep.<\/p>\n
If anything could top the first shock of seeing its beautiful spiral nebula, it\u2019s this breathtaking new image (at the top of this article). The new Webb data are now analyzed in two papers on arXiv. Paper 1 and paper 2.<\/p>\n
Violent star deaths<\/h3>\n
Right before they die as supernovas, the universe\u2019s most massive stars violently shed their outer hydrogen layers, leaving their heavy cores exposed.<\/p>\n
These are Wolf-Rayet stars, named after their discoverers Charles Wolf and Georges Rayet. Wolf and Rayet noticed powerful streams of gas blasting out from these objects, much stronger than the stellar wind from our sun. The Wolf-Rayet stage lasts only millennia \u2013 a blink of the eye in cosmic time scales \u2013 before they violently explode.<\/p>\n
Unlike our sun, many stars in the universe exist in pairs known as binaries. This is especially true of the most massive stars, such as Wolf-Rayets.<\/p>\n
When the fierce gales from a Wolf-Rayet star clash with their weaker companion\u2019s wind, they compress each other. In the eye of this storm forms a dense, cool environment in which the carbon-rich winds can condense into dust. The earliest carbon dust in the cosmos \u2013 the first of the material making up our own bodies \u2013 was made this way. <\/p>\n
The dust from a Wolf-Rayet blows out in almost a straight line. And the orbital motion of the stars wraps it into a spiral-shaped nebula. So it appears exactly like water from a sprinkler when viewed from above.<\/p>\n
We expected Apep to look like one of these elegant pinwheel nebulas, discovered by our colleague and co-author Peter Tuthill. To our surprise, it did not.<\/p>\n\n The \u201cpinwheel\u201d nebula of the triple Wolf-Rayet star system WR104. Image via Peter Tuthill. <\/figcaption><\/figure>\n
Equal rivals<\/h3>\n
Webb\u2019s infrared camera took the new image. The camera is like the thermal cameras that hunters or the military use. The image represents hot material as blue and colder material in green to red. <\/p>\n
It turns out Apep isn\u2019t just one powerful star blasting a weaker companion, but two<\/em> Wolf-Rayet stars. The rivals have near-equal strength winds, and the dust spreads out in a wide cone, wrapping into a wind-sock shape.<\/p>\n
When we originally described Apep in 2018, we noted a third, more distant star, speculating whether it was also part of the system or a chance interloper along the line of sight.<\/p>\n
The dust appeared to be moving much slower than the winds, which was hard to explain. We suggested the dust might be carried on a slow, thick wind from the equator of a fast-spinning star, rare today but common in the early universe.<\/p>\n
The new, much more detailed data from Webb reveal three more dust shells zooming farther out, each cooler and fainter than the last and spaced perfectly evenly, against a background of swirling dust. <\/p>\n\n The Apep nebula in false color, displaying infrared data from Webb\u2019s MIRI camera. Image via Han et al.\/White et al.\/Dholakia; NASA\/ ESA. <\/figcaption><\/figure>\n
New data on Apep, new knowledge<\/h3>\n
Researchers have now published the Webb data, interpreted in a pair of papers. One is led by Caltech astronomer Yinuo Han, and the other by Macquarie University Masters student Ryan White.<\/p>\n
Han\u2019s paper reveals how the nebula\u2019s dust cools, links the background dust to the foreground stars and suggests the stars are farther away from Earth than we thought. This implies they are extraordinarily bright, but weakens our original claim about the slow winds and rapid rotation. <\/p>\n
In White\u2019s paper, he develops a fast computer model for the shape of the nebula and uses this to decode the orbit of the inner stars very precisely.<\/p>\n
He also noticed there\u2019s a \u201cbite\u201d taken out of the dust shells, exactly where the wind of the third star would be chewing into them. This proves the Apep family isn\u2019t just a pair of twins \u2026 they have a third sibling.<\/p>\n\n An illustration of the cavity carved by the 3rd star companion in the Apep system. Image via White et al. (2025). <\/figcaption><\/figure>\n
Understanding systems like Apep tells us more about star deaths and the origins of carbon dust. But these systems also have a fascinating beauty that emerges from their seemingly simple geometry.<\/p>\n
The violence of stellar death carves puzzles that would make sense to Newton and Archimedes, and it is a scientific joy to solve them and share them.<\/p>\n
Benjamin Pope, Associate Professor, School of Mathematical and Physical Sciences, Macquarie University<\/span><\/p>\n
This article is republished from The Conversation under a Creative Commons license. Read the original article.<\/p>\n
Bottom line: The James Webb Space Telescope has captured an image of Apep, which includes the swirling nebula around two dying stars. A scientist explains what we know about it now.<\/p>\n
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EarthSky Voices<\/h4>\n
View Articles\n <\/p><\/div>\n
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About the Author:<\/h6>\n
Members of the EarthSky community – including scientists, as well as science and nature writers from across the globe – weigh in on what’s important to them.<\/p>\n<\/p><\/div>\n<\/p><\/div>\n
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