Regardless of being one of the crucial venerable and distinguished objects within the night time sky, the Andromeda Galaxy (M31) nonetheless has surprises. And a bunch of newbie astronomers have uncovered the newest: a beforehand unknown emission nebula mendacity simply southeast of Andromeda and spanning half the width of the galaxy itself.
The function was found in photos taken final yr with an Oxygen-III (OIII) filter by French astroimager Yann Sainty, who labored with Marcel Drechsler and Xavier Strottner to course of and analzye the information. They’ve designated the function Strottner-Drechsler-Sainty Object 1.
They then labored with a staff {of professional} astronomers and different astroimagers to verify the discover. The staff revealed their ends in Research Notes of the AAS final month — in addition to a surprising, highly-processed picture on the astroimaging web site Astrobin (reproduced above).
A facet mission
The observations of Andromeda started as a facet mission for the trio, who had initially teamed up for one more purpose: Drechsler and Strottner preserve a catalog of planetary nebulae, and had requested Sainty to seize a number of recognized and candidate objects.
Sainty traveled all throughout France searching for the darkest websites he may discover for his cell observing setup, which features a 4.2-inch Takahashi refractor and a CMOS astronomical digital camera from ZWO. After concluding this months-long mission, Sainty “determined to give attention to a soothing and simple mission — the Andromeda Galaxy,” Drechsler mentioned in a press release shared with media, together with Astronomy and ZWO.
“Whereas engaged on the Andromeda mission, Yann Sainty did one thing that few astrophotographers earlier than him have achieved — he used an OIII filter to higher carry out the faint HII areas,” mentioned Drechsler. “Since an OIII filter is comparatively new territory in astrophotography, Yann despatched the information to [me] and Xavier for overview. Yann’s secret hope, maybe, was to have a beforehand unknown planetary nebula or supernova remnant within the information.”
When Drechsler and Strottner appeared on the OIII photos, they seen “an especially faint nebulosity … on the fringe of the picture that appeared to proceed exterior the picture.” At first, the staff thought-about whether or not it was an artifact, like a gradient launched via a defective flat-field calibration picture. However Drechsler “urged Sainty to gather extra OIII information, considering he noticed finer sub-structures within the barely-visible nebula.”
Sainty collected extra photos via the autumn of 2022, ultimately totaling 111 hours of publicity. As he did, the staff started more and more certain they’d discovered one thing actual — and beforehand unreported.
Confirming observations
The staff reached out to skilled astronomers to help in verifying their discovery, together with Robert Fesen of Dartmouth School in Hanover, New Hampshire. In an interview with Astronomy finally month’s assembly of the American Astronomical Society (AAS) in Seattle, Fesen pointed to the arc in a picture and summed up his preliminary response: “What the hell is that?”
“Once they despatched it to me, I mentioned, ‘There’s one thing flawed along with your digital camera, and go repair it and go away me alone,’” he quipped. “[Dreschler] got here again a few weeks later: ‘Rob, it’s actual.’ And I mentioned, ‘Look, you haven’t tried onerous sufficient to kill it.’”
To verify it, different astroimagers joined the hunt: Bray Falls working with two distant telescopes in California, Christophe Vergnes and Nicolas Martino in France, and Sean Walker (affiliate editor at Sky and Telescope journal) observing with a distant telescope in New Mexico. Their outcomes satisfied Fesen: “5 completely different telescopes see stuff there? At completely different ranges of decision, however it’s in the identical spot of the sky off M31? I made a decision it’s actual.”
Remarkably, the nebula had been missed by earlier OIII surveys of M31 on professional-grade telescopes, including one by the three.6-meter Canada-France-Hawaii Telescope (CFHT) on Mauna Kea. That’s as a result of many devices designed for analysis merely aren’t well-suited to identify such a faint and prolonged nebula.
CFHT’s MegaCam instrument has a discipline of view of 1° — large by skilled requirements, however nonetheless not large sufficient to seize the total extent of the brand new object, which spans 1.5°. The MegaCam survey of M31 additionally used a filter that allowed a comparatively big selection of wavelengths to move via — over 10 nanometers. Sainty used an off-the-shelf Antlia filter with a bandwidth of simply 3 nm, which higher remoted the OIII sign from background noise.
Right here or there?
The discover has set the astronomical neighborhood ablaze with hypothesis in regards to the object’s nature, together with whether or not it’s bodily subsequent to Andromeda, which is 2.5 million light-years away. It’s totally attainable that the newfound object is a part of the Milky Way and easily lies alongside our line of sight to our galactic neighbor.
One risk that the staff thought-about was that the function is attributable to Andromeda starting to work together with the Milky Way. However, they wrote, “the arc appears a lot too near M31 to suit that image. Extra possible, it lies inside M31’s halo and is said to the quite a few stellar streams, particularly the Large Stellar Stream whose japanese edge lies near the OIII arc.”
Nonetheless, Fesen tells Astronomy that since then, “I’ve began to suppose it much less more likely to be a function of M31, however, as an alternative, a Milky Way nebula a lot nearer. However who is aware of.”
To settle the difficulty, Fesen and his colleagues hope to acquire a spectrum with a professional-grade observatory. From this, they will measure any Doppler shift within the mild attributable to movement towards or away from the Milky Way — and whether or not it matches the movement of Andromeda itself.
Whether or not or not the arc is in the end related to Andromeda, the invention highlights the function that newbie astronomers and imagers with broadly out there high-quality narrowband filters are taking part in in discovering faint, prolonged emission nebulae.
Fesen expressed admiration for the imagers, who, he notes, are taking information that totals exposures of “fractions of a day or extra.” He pointed to one of many affirmation photos: “That one image’s 86 hours. Are you kidding me? [Sainty’s image] was taken over 22 nights over three months of clear climate. That is insane.”
