A classroom idea results in the invention of a trio of stars that shaped 12 to 13 billion years in the past.
The Milky Way Galaxy holds remnants of ultrafaint dwarf galaxies. Credit score: NASA
To search out the universe’s oldest stars, you have to search for those with low chemical abundances and a retrograde orbit. That’s what a gaggle of scholars in a category of MIT professor of physics and division head for astrophysics Anna Frebel discovered.
Utilizing these strategies, the group found three of essentially the most historic stars within the universe hidden within the Milky Way’s Halo. The trio of stars is assumed to have shaped 12 to 13 billion years in the past; when the primary galaxies had been starting to kind in what we now name ultra-faint dwarf satellite galaxies (UFDs). The research was printed in Monthly Notices of the Royal Astronomical Society. “These oldest stars ought to undoubtedly be there, given what we all know of galaxy formation,” stated Frebel in a press release. “They’re a part of our cosmic household tree. And we now have a brand new method to discover them.”
A stellar course
The trace for locating the galaxies’ most historic stars began in Frebel’s class referred to as Observational Stellar Archeology, the place her college students realized about completely different methods to research historic stars and try to establish their origin. The category used information Frebel had been gathering from the 6.5-meter Magellan-Clay telescope at Las Campanas Observatory. The group discovered these three outsider stars and dubbed them Small Accreted Stellar System stars (SASS).
These SASS stars belonged to a UFD at one level and finally merged with a youthful Milky Way Galaxy. Now, the one proof of the dwarf historic galaxy is the trio of stars. However the group suspects there are extra on the market. Frebel’s group hopes to make use of the three stars as a method to additional perceive galaxy evolution, particularly in UFDs.
Low chemical compounds
The info centered on stars that shaped 13.8 million years in the past, quickly after the Big Bang. At this stage within the universe’s life, essentially the most considerable parts had been hydrogen and helium, however there have been additionally small traces of heavier parts akin to strontium and barium.
It’s extraordinarily helpful to measure a star’s chemical abundance as a result of it reveals the kind of chemical surroundings the star was born in, whether it is a part of a household (a number of stars born from the identical nebula), in addition to offering hints as to what age the star could also be. To measure a star’s chemical abundance, it’s usually relative to that of the Solar. Frebel’s group discovered that one of many stars within the trio had 1/10,000 the quantity of iron to helium in comparison with that of the Solar. However how did these relics get themselves transported into the Milky Way galaxy?
A peculiar orbit
Frebel’s group traced every of the star’s orbits utilizing Gaia astrometric information and located that they had been truly transferring in the wrong way of the opposite stars within the Milky Way — that means that they’ve retrograde orbits. Within the astronomy world, particularly galactic archaeology, this a serious tell-tale signal that the celebs got here from a progenitor system — a UFD. “The one means you possibly can have stars going the flawed means from the remainder of the gang is when you threw them within the flawed means,” stated Frebel.
Frebel took a step additional and analyzed different historic stars within the Milky Way halo that had been beforehand studied and located 65 fast-moving (a whole lot of kilometers per second) retrograde stars that additionally had low strontium and barium abundances. “They’re on the run! We don’t know why that’s the case, however it was the piece to the puzzle that we would have liked, and that, I didn’t fairly anticipate after we began,” stated Frebel in an announcement.
Subsequent, the researchers plan on on the lookout for extra SASS stars and UFDs. From the 400 billion stars within the Milky Way, the scholars are hopeful they’ll discover extra of the universe’s oldest stars.
