A bewilderingly highly effective thriller object present in a close-by galaxy and solely seen thus far in millimeter radio wavelengths might be a model new astrophysical object not like something astronomers have seen earlier than.
The item has been named ‘Punctum,’ derived from the Latin pūnctum which means “level” or
“dot,” by a staff 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 Giant Millimeter/submillimeter Array.
“Outdoors of the realm of supermassive black holes, Punctum is genuinely highly effective,” Shablovinskaia instructed 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.
“Once 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 stated.
Punctum is positioned within the lively galaxy NGC 4945, which is a reasonably shut neighbor of our Milky Manner 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 somewhat solely millimeter radio wavelengths. This has solely deepened the thriller, though the James Webb House Telescope (JWST) has but to try the thing in near- and mid-infrared wavelengths.
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 form of transitory phenomenon. Millimeter-wave radiation sometimes comes from chilly objects resembling younger protoplanetary disks and interstellar molecular clouds. Nonetheless, very energetic phenomena resembling quasars and pulsars also can produce radio waves via synchrotron radiation, whereby charged particles transferring at near the pace of sunshine spiral round magnetic discipline traces 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 sturdy polarization are typically 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 staff believes, which is a extremely magnetic pulsar. Nonetheless, whereas a magnetar’s ordered magnetic discipline matches 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 house of a star that exploded in 1054AD, are shiny at millimeter wavelengths. The difficulty is that supernova remnants are fairly massive — the Crab Nebula itself is about 11 light-years throughout — whereas Punctum is clearly a a lot smaller, compact object.
“In the mean time, Punctum really stands aside — it would not match comfortably into any recognized class,” stated Shablovinskaia. “And actually, nothing like this has appeared in any earlier millimeter surveys, largely as a result of, till not too long ago, we did not have something as delicate and high-resolution as ALMA.”
There may be the caveat that Punctum might simply be an outlier: an excessive model of an in any other case acquainted object, resembling 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 form 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 lively 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 knowledge if it wasn’t for its exceptionally sturdy polarization.
Additional observations with ALMA will definitely assist shed extra gentle on what sort of object Punctum is. The observations that found Punctum have been really targeted on NGC 4945’s shiny lively 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 may be noticed throughout totally 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 would possibly assist reveal whether or not Punctum’s emission is only synchrotron or includes mud or emission traces,” stated 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 thus far left them feeling flummoxed.
“In any case,” concluded Shablovinskaia, “Punctum is displaying us that there’s nonetheless loads 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 offered on astro.ph.
