The first data has arrived from a new telescope array.
The Condor Array revealed a striking view of a distant dwarf nova; The scene offers astronomers a stunning new, ultra-low-brightness view of the universe.
Condor consists of six refracting telescopes combined by computers to form a giant telescope cluster that can detect and study objects too faint to be seen by a normal human. single telescope. One of Condor’s first missions was to focus on a dwarf nova called Z Camelopardalis. In particular, American Museum of Natural History researcher Michael M. Shara wanted to find out whether this dwarf nova had anything to do with the “new star” recorded by Imperial Chinese astrologers in 77 BC.
The new telescope array not only strengthened this connection, but also discovered intriguing, never-before-seen features of the dwarf nova. The object has been studied in great detail since it was first observed in visible light by astronomer Henry Park Hollis in 1904. Therefore, it is very exciting to find new information about him.
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Shy novas emerging from their shells
Dwarf novae are a separate class of supernova explosions that occur in one of two ways.
The first way involves a white dwarf star remnant slowly pulling matter from its companion star onto its surface. This type of siphoning continues until the process triggers a thermonuclear explosion. On the other hand, the second pathway that can lead to a dwarf nova involves a large amount of material from a companion star being suddenly “dumped” onto the white dwarf, with the same thermonuclear result.
In January 2007, an image of Z Camelopardalis taken with the 4-meter telescope at Kitt Peak National Observatory appeared to show that it was surrounded by a partial shell of gas that may have been emitted during a thermonuclear explosion.
To test this idea, Shara and colleagues imaged Z Camelopardalis with Condor in November 2021 and compared it to the 2007 image. This allowed them to measure how much the crust had expanded over time and therefore the rate at which its gas was moving outward.
This confirmed to the team that the crust was expanding at a rate consistent with an explosion that occurred about 2,000 years ago, and suggested that this explosion may indeed have been the “new star” seen in China in 77 BC.
Shara and the team were amazed to find that Condor could distinguish the entire gas shell around Z Camelopardalis. The new telescope array also spotted a second, larger (but fainter) shell of gas around the dwarf nova. Such a shell is too faint to be seen with conventional telescopes.
“This is the first example ever found of two concentric shells surrounding a dwarf nova, confirming a long-standing hypothesis that concentric shells should surround novae of relatively massive white dwarfs that frequently explode,” Shara said.
But that wasn’t the extent of the nova discoveries revealed in Condor’s first data drop.
Stonybrook University professor Kenneth M. Lanzetta and his team used the telescope to detect an extremely faint shell of gas surrounding a “recurring nova.” This class of novae also results from white dwarfs accumulating matter and becoming unstable, but explosions occur repeatedly over periods of less than 100 years.
M31N 2008-12a, a recurring nova, is located in Andromeda, the closest major galaxy to the Milky Way. It explodes every year and is surrounded by a massive “super-remnant” of dust shells that expands outward for about 44 million light-years. Other recurring novae should also be surrounded by these shells; but so far these have proven difficult to find.
Lanzetta and colleagues detected a crust around the recurring nova KT Eridani (KT Eri) that erupts at its peak every 40 to 50 years. The team says this shell is about 50 times larger than previously observed nova shells and appears to be the result of multiple nova shells crashing into each other over tens of thousands of years.
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There’s more interesting stuff in the first batch of Condor data, too; Lanzetta and his colleagues are also using the telescope to study stellar streams around galaxy NGC 5907, a well-known spiral galaxy located about 50 million light-years from Earth. These stellar streams occur when larger galaxies orbiting satellite galaxies gravitationally pull on the satellites, distorting them and pulling in stars.
Condor followed up two previous images of NGC 5907, located 50 million light-years from Earth. One in 2010 showed streams of stars forming two spiral-like loops around the galaxy, but another in 2019 lacked these features.
Like the second image, the Condor observation of NGC 5907 appeared to lack this spiral-like feature. The team suggested that this was an artifact of the image processing of the 2010 image.
The Condor Array Telescope’s findings are published in a series of four papers published in the journal Monthly Notices of the Royal Astronomical Society.