A bewilderingly highly effective thriller object present in a close-by galaxy and solely seen to date in millimeter radio wavelengths may very well be a model new astrophysical object not like something astronomers have seen earlier than.
The article has been named ‘Punctum,’ derived from the Latin pūnctum which means “level” or
“dot,” by a group of astronomers led by Elena Shablovinskaia of the Instituto de Estudios Astrofísicos on the Universidad Diego Portales in Chile. Shablovinskaia found it utilizing ALMA, the Atacama Massive Millimeter/submillimeter Array.
“Outdoors of the realm of supermassive black holes, Punctum is genuinely highly effective,” Shablovinskaia advised House.com.
Astronomers do not know what it’s but — solely that it’s compact, has a surprisingly structured magnetic discipline, and, at its coronary heart, is an object radiating intense quantities of vitality.
“While you put it into context, Punctum is astonishingly shiny — 10,000 to 100,000 occasions extra luminous than typical magnetars, round 100 occasions brighter than microquasars, and 10 to 100 occasions brighter than almost each recognized supernova, with solely the Crab Nebula surpassing it amongst star-related sources in our galaxy,” Shablovinskaia mentioned.
Punctum is positioned within the energetic galaxy NGC 4945, which is a reasonably shut neighbor of our Milky Means galaxy, positioned 11 million light-years away. That is simply past the confines of the Native Group. But, regardless of this proximity, it can’t be seen in optical or X-ray gentle however relatively solely millimeter radio wavelengths. This has solely deepened the thriller, though the James Webb House Telescope (JWST) has but to check out the article in near- and mid-infrared wavelengths.
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What might Punctum be?
Its brightness remained the identical over a number of observations carried out in 2023, which means it’s not a flare or another type of transitory phenomenon. Millimeter-wave radiation usually comes from chilly objects equivalent to younger protoplanetary disks and interstellar molecular clouds. Nevertheless, very energetic phenomena equivalent to quasars and pulsars can even produce radio waves by means of synchrotron radiation, whereby charged particles shifting at near the pace of sunshine spiral round magnetic discipline strains and radiate radio waves.
What we do find out about Punctum is that based mostly on how strongly polarized its millimeter gentle is, it should possess a extremely structured magnetic discipline. And so, Shablovinskaia believes what we’re seeing from Punctum is synchrotron radiation. Objects with robust polarization are usually compact objects, as a result of bigger objects have messy magnetic fields that wash out any polarization.
Maybe that synchrotron radiation is being powered by a magnetar, the group believes, which is a extremely magnetic pulsar. Nevertheless, whereas a magnetar’s ordered magnetic discipline suits the invoice, magnetars (and common pulsars for that matter) are a lot fainter at millimeter wavelengths than Punctum is.
Supernova remnants such because the Crab Nebula, which is the messy innards blasted into area of a star that exploded in 1054AD, are shiny at millimeter wavelengths. The difficulty is that supernova remnants are fairly giant — the Crab Nebula itself is about 11 light-years throughout — whereas Punctum is clearly a a lot smaller, compact object.
“In the meanwhile, Punctum actually stands aside — it does not match comfortably into any recognized class,” mentioned Shablovinskaia. “And truthfully, nothing like this has appeared in any earlier millimeter surveys, largely as a result of, till just lately, we did not have something as delicate and high-resolution as ALMA.”
There’s the caveat that Punctum might simply be an outlier: an excessive model of an in any other case acquainted object, equivalent to a magnetar in an uncommon setting, or a supernova remnant interacting with dense materials. For now, although, these are simply guesses missing supporting proof. It’s fairly potential that Punctum is certainly the primary of a brand new type of astrophysical object that we’ve not seen earlier than just because solely ALMA can detect them.
Within the case of Punctum, it’s 100 occasions fainter than NGC 4945’s energetic nucleus that’s being energized by a supermassive black gap feeding on infalling matter. Punctum most likely would not have been seen in any respect within the ALMA information if it wasn’t for its exceptionally robust polarization.
Additional observations with ALMA will definitely assist shed extra gentle on what sort of object Punctum is. The observations that found Punctum had been really centered on NGC 4945’s shiny energetic core; it was simply happenstance that Punctum was seen within the discipline of view. Future ALMA observations focusing on Punctum as a substitute would be capable to go to a lot decrease noise ranges with out worrying concerning the galaxy’s shiny core being over-exposed, and it is also noticed throughout completely different frequencies.
The best assist might doubtlessly come from the JWST. If it could see an infrared counterpart, then its higher decision might assist establish what Punctum is.
“JWST’s sharp decision and broad spectral vary may assist reveal whether or not Punctum’s emission is solely synchrotron or entails mud or emission strains,” mentioned Shablovinskaia.
For now, it is all ifs and buts, and all we are able to say for positive is that astronomers have a real thriller on their arms that has to date left them feeling flummoxed.
“In any case,” concluded Shablovinskaia, “Punctum is exhibiting us that there’s nonetheless so much to find within the millimeter sky.”
A paper describing the invention of Punctum has been accepted by the journal Astronomy & Astrophysics, and a pre-print is accessible on astro.ph.
