Redness of Neptunian asteroids sheds light on early Solar System

Date:
March 28, 2023
Source:
Royal Astronomical Society
Summary:
Asteroids sharing their orbits with the planet Neptune have been
observed to exist in a broad spectrum of red color, implying the
existence of two populations of asteroids in the region, according
to a new study by an international team of researchers.


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FULL STORY ========================================================================== Asteroids sharing their orbits with the planet Neptune have been observed
to exist in a broad spectrum of red colour, implying the existence of
two populations of asteroids in the region, according to a new study by
an international team of researchers. The research is published in the
journal Monthly Notices of the Royal Astronomical Society: Letters.


==========================================================================
The team of scientists from the USA, California, France, the Netherlands,
Chile and Hawaii observed 18 asteroids sharing the orbit of Neptune,
known as Neptunian Trojans. They are between 50 and 100 km in size and
are located at a distance of around 4.5 billion kilometres from the
Sun. Asteroids orbiting this far away are faint and so are challenging
for astronomers to study. Before the new work, only about a dozen
Neptunian Trojans had been studied, requiring the use of some of the
largest telescopes on Earth.

The new data were gathered over the course of two years using the WASP
wide field camera on the Palomar Observatory telescope in California,
the GMOS cameras on the Gemini North and South telescopes in Hawaii and
Chile, and the LRIS camera on the Keck Telescope in Hawaii.

Of the 18 observed Neptunian Trojans, several were much redder than
most asteroids, and compared with other asteroids in this group looked
at in previous studies. Redder asteroids are expected to have formed
much further from the Sun; one population of these is known as the Cold Classical trans- Neptunian objects found beyond the orbit of Pluto, at
around 6 billion kilometres from the Sun. The newly observed Neptunian
Trojans are also unlike asteroids located in the orbit of Jupiter,
which are typically more neutral in colour.

The redness of the asteroids implies that they contain a higher proportion
of more volatile ices such as ammonia and methanol. These are extremely sensitive to heat, and can rapidly transform into gas if the temperature
rises, so are more stable at large distances from the Sun.

The location of the asteroids at the same orbital distance as Neptune
also implies that they are stable on timescales comparable to the age
of the Solar System. They effectively act as a time-capsule, recording
the initial conditions of the Solar System.

The presence of redder asteroids among the Neptunian Trojans suggests
the existence of a transition zone between more neutral coloured and
redder objects. The redder Neptunian asteroids may have formed beyond this transition boundary before being captured into the orbit of Neptune. The Neptunian Trojans would have been captured into the same orbit as the
planet Neptune as the ice giant planet migrated from the inner solar
system to where it is now, some 4.5 billion kilometres from the Sun.

Lead author Dr Bryce Bolin of the NASA Goddard Space Flight Centre said,
"In our new work we have more than doubled the sample of Neptunian
Trojans studied with large telescopes. It's exciting to find the first
evidence of redder asteroids in this group." "Because we have a larger
sample of Neptunian Trojans with measured colours, we can now start to
see major differences between asteroid groups. Our observations also
show that the Neptunian Trojans are also different in colour compared
to asteroid groups even further from the Sun. A possible explanation
may be that the processing of the surfaces of asteroids by the Sun's
heat may have different effects for asteroids at varying solar distances."
* RELATED_TOPICS
o Space_&_Time
# Solar_System # Sun # Space_Telescopes # Solar_Flare #
Astronomy # Neptune # Space_Exploration # Pluto
* RELATED_TERMS
o Asteroid_belt o Near-Earth_asteroid o Asteroid o Neptune
o Satellite o Neptune's_natural_satellites o Redshift o
Solar_system

========================================================================== Story Source: Materials provided by Royal_Astronomical_Society. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. B T Bolin, C Fremling, A Morbidelli, K S Noll, J van Roestel, E K
Deibert, M Delbo, G Gimeno, J-E Heo, C M Lisse, T Seccull,
H Suh. Keck, gemini, and palomar 200-inch visible photometry
of red and very-red neptunian trojans. Monthly Notices of the
Royal Astronomical Society: Letters, 2023; 521 (1): L29 DOI:
10.1093/mnrasl/slad018 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2023/03/230328145329.htm

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