A swirl discovered in the turbulent slab of dust surrounding a young star named AB Aurigae was revealed last week in high resolution and too much fanfare in the astronomical community. Such a distinct disorder, researchers suggested, could be a baby poplan’s signature in shape.
Although this baby’s exoplanet was widely reported by many stores as a doubtful interpretation of the information, “it” is important. Now a new paper nicely shows why: a separate team of researchers has found that the swirling pond can be caused by another object – a forming star, a binary companion to AB Aurigae.
The new interpretation has been described in a paper submitted to Monthly announcements from the Royal Astronomical Society, and waiting for the last peer review.
“AB Aurigae is a compendium of interesting functions,”
“We have a huge central cavity, spirals, dusty lumps, among others. The planet scenario has been proposed to explain some of these features.
“It is true that a planet can explain the dusty clumps, but not the huge cavity, and it is also true that it can explain spirals, but not the spirals that we observe in AB Aurigae,” Poblete added. “However, a stellar scenario can easily explain all these features.”
AB Aurigae is one of the closest stars of its kind. It is very young, only about 4 million years old (the Sun is about 4.6 billion years old), and it is still surrounded by a thick, complex protoplanetary disk – the material left over from star formation.
Such stars are of great interest and importance, as we believe they can reveal how exoplanets are formed by remaining stardust. And AB Aurigae is particularly interesting. In 2017, Atacama Large Millimeter / Sub-Millimeter Array (ALMA) in Chile revealed a gap in dust clouds, containing what appeared to be curling, spiraling properties.
“AB Aurigae belongs to a class of discs labeled” transitional discs, “which are” discs with holes in the middle, “Monash University astronomer Daniel Price, co-author of the latest magazine, told ScienceAlert.
“It’s been one pulp of speculation about what creates these central cavities (or ‘holes’) – whether binary stars, planets or dust clearing of any other mechanism. “
Exoplanets were the explanation in last week’s magazine, led by astronomer Anthony Boccaletti of the Observatoire de Paris in France. His team’s modeling suggested that the swirling spirals in AB Aurigae’s cloud could have been produced by a forming exoplanet between four and 13 times the mass of Jupiter.
But not everyone agrees. “A planet alone would not be massive enough to create the strong spiral arms and the cleaned central cavity seen in AB Aurigae,” Price told ScienceAlert.
A binary companion, on the other hand, could fit the observed functions. And that’s not a wild idea. Binary stars are extremely common – up to 85 percent of all stars can be in multi-star systems, and there is evidence to suggest that all stars are born in pairs, with some losing their comrades later (like the sun’s long-lost twin).
In a model of binary formation, it forms the circumstellar disk around a young star fragment, and a portion of it gravitationally collapses onto itself to form a second star, drawing the surrounding material around itself into a second, smaller disk within the larger disc.
In the model proposed by Poblete and his team, the spiral observed in AB Aurigae’s dust holes could have been produced by a small star, about half the mass of the sun, to AB Aurigae’s two solar masses – if the binary companion is on a very high inclined path between 60 and 90 degrees, around AB Aurigae’s posts, and with a high orbital eccentricity.
It’s not as strange as it may sound. As price notes, star formation is a dirty process, which can lead to difficulties in the cycle.
“We expect to find a” weird “configuration in the early stages of binary star formation,” Poblete said.
“We know that stars are formed in a giant gas cloud. This cloud is a factory of stars. When stars are born, they always interact with others, and in some cases two or more stars [become] bound in a plurality of systems. “
“All this happens when the stars are still absorbing gas from an accretion disk; for that reason you can get [secondary] discs eccentric and prone to such discs, “added Poblete.” A binary system will also have an unstable stable configuration; As time goes on, the binary will become more and more stable. “
The observed spiral arms on AB Aurigae’s record, the team notes in the magazine, are similar to those observed in other forming binary systems, which [BHB2007] 11 and FS Tau A, where the latter has a circuit between 35 and 60 degrees.
But since we cannot see the object – which is actually not so strange, given the brightness of AB Aurigae and the amount of material that swirls around – the presence of a binary companion is still hypothetical.
So the exoplanet cannot be excluded. As Boccaletti explained to ScienceAlert, although Poblete’s team model is more complex than his own team, his team had access to more information.
“We have new data from SPHERE,” Boccaletti told ScienceAlert, referring to the adaptive optics system connected to the Very Large Telescope in Chile.
“ALMA and SPHERE do not observe the same light and are not sensitive to the same component. SPHERE is sensitive to the scattered light of the dust from the star. It is also very sensitive to the stars themselves.”
“Even if we used different information,” he added, “there’s a good chance that if a star companion was responsible for the spiral, it would have been an obvious signal in the SPHERE image, unless the eclipse of gas and dust is huge.”
None of the law claims a discovery at this point. We simply do not have enough data. There is no detection of either an exoplanet or a protostar – only ripples in the gas, depending on which model and data set you use, can be interpreted as one or the other.
“We can’t claim discovery based on a modeling paper,” Price said. “What we can say is that the alleged protoplanet is incredible based on our modeling, because we believe there is something much bigger there (and not in the proposed site). That doesn’t mean our claims are correct either, it’s just a healthy debate. “
This is how science works best. Observations are made. Researchers interpret the data and propose explanations. That’s right now. The next step is further observations, which can shed more light on the phenomenon and help to reach a firmer conclusion.
Both teams work towards this goal. According to Price, a binary companion would shift AB Aurigae slightly in the sky. If so, that move should be detectable in the next issue of data from the Gaia satellite, which maps the Milky Way.
At the same time, Boccaletti’s team is requesting more information from SPHERE to see if closer observations of the system can solve AB Aurigae’s identity crisis.
“AB Aurigae is definitely a very interesting system for understanding planet formation and a lot of work remains to be done,” Boccaletti said.
The new research has been submitted to Monthly announcements from the Royal Astronomical Society and is available on arXiv.