Credit: ESO / M. Kornmesser
New research finds that 'Oumuamua, the rocky object identified as the first confirmed interstellar asteroid, very likely came from a binary star system.
A binary star system, unlike our Sun, is one with two stars orbiting a common centre.
For the new study, published in the journal Monthly Notices of the Royal Astronomical Society,
Jackson and his co-authors set about testing how efficient binary star
systems are at ejecting objects. They also looked at how common these
star systems are in the Galaxy.
They found that rocky objects like 'Oumuamua are far more likely to
come from binary than single star systems. They were also able to
determine that rocky objects are ejected from binary systems in
comparable numbers to icy objects.
"It's really odd that the first object we would see from outside our
system would be an asteroid, because a comet would be a lot easier to
spot and the Solar System ejects many more comets than asteroids," says
Jackson, who specializes in planet and solar system formation.
Once they determined that binary systems are very efficient at
ejecting rocky objects, and that a sufficient number of them exist, they
were satisfied that 'Oumuamua very likely came from a binary system.
They also concluded that it probably came from a system with a
relatively hot, high mass star since such a system would have a greater
number of rocky objects closer in.
The team suggest that the asteroid was very likely to have been
ejected from its binary system sometime during the formation of planets.
'Oumuamua, which is Hawaiian for 'scout', was first spotted by the Haleakala Observatory
in Hawaii on 19 October 2017. With a radius of 200 metres and
travelling at a blistering speed of 30 kilometres per second, at its
closest it was about 33,000,000 km from Earth.
When it was first discovered researchers initially assumed the object
was a comet, one of countless icy objects that release gas when they
warm up on approaching the Sun. But it didn't show any comet-like
activity as it neared the Sun, and was quickly reclassified as an
asteroid, meaning it was rocky.
Researchers were also fairly sure it was from outside our Solar
System, based on its trajectory and speed. An eccentricity of 1.2 –
which classifies its path as an open-ended hyperbolic orbit – and such a
high speed meant it was not bound by the gravity of the Sun.
In fact, as Jackson points out, 'Oumuamua's orbit has the highest
eccentricity ever observed in an object passing through our Solar
System.
Major questions about ‘Oumuamua remain. For planetary scientists like
Jackson, being able to observe objects like these may yield important
clues about how planet formation works in other star systems.
“The same way we use comets to better understand planet formation in
our own Solar System, maybe this curious object can tell us more about
how planets form in other systems.”
Media Contact
Dr Robert Massey
Royal Astronomical Society
Tel: +44 (0)20 7292 3979
Mob: +44 (0)7802 877 699
press@ras.ac.uk
Dr Morgan Hollis
Royal Astronomical Society
Tel: +44 (0)20 7292 3977
Mob: +44 (0)7802 877 700
press@ras.ac.uk
Science Contact
Dr Alan Jackson
CPS Postdoctoral Fellow
Centre for Planetary Sciences
University of Toronto
Tel: +1 416 208 5099 (4 hours behind GMT)
ajackson@cita.utoronto.ca
http://www.alanjacksonastronomy.com/
Further Information
The new work appears in: “Ejection of rocky and icy material from
binary star systems: Implications for the origin and composition of
1I/`Oumuamua", A. Jackson, D. Tamayo, N. Hammond, M. Ali-Dib, H. Rein,
Monthly Notices of the Royal Astronomical Society (2018), in press (DOI:
10.1093/mnras/sly033).
A copy of the paper is available here.
Notes for Editors
The Royal Astronomical Society
(RAS), founded in 1820, encourages and promotes the study of astronomy,
solar-system science, geophysics and closely related branches of
science. The RAS organizes scientific meetings, publishes international
research and review journals, recognizes outstanding achievements by the
award of medals and prizes, maintains an extensive library, supports
education through grants and outreach activities and represents UK
astronomy nationally and internationally. Its more than 4,000 members
(Fellows), a third based overseas, include scientific researchers in
universities, observatories and laboratories as well as historians of
astronomy and others.
The RAS accepts papers for its journals based on the principle of
peer review, in which fellow experts on the editorial boards accept the
paper as worth considering. The Society issues press releases based on a
similar principle, but the organisations and scientists concerned have
overall responsibility for their content.
Follow the RAS on Twitter, Facebook and Instagram
