The Japanese Hayabusa-2 spacecraft continues its deployment of remote-control systems onto the asteroid Ryuga (see earlier posting here about deployment of two micro-rovers). On Wednesday the spacecraft released the MASCOT (Mobile Asteroid Surface Scout) lander, which was built by the German Aerospace Center (DLR) and the French Space Agency (CNES).
MicrOmega – a hyperspectral infrared microscope to analyze the mineralogical properties of the surface materials.
MASCAM – “a multispectral wide field camera to provide geological images of the asteroid”.
MARA – a radiometer “to determine the surface temperature and the thermal inertia of the asteroid”.
MASMAG – a magnetometer, which measures magnetic field strength.
This video previewed the MASCOT mission, which lasted about 17 hours before its batteries ran out:
Artist’s view of the deployment of MASCOT:
“Left: Illustration of MASCOT separating from Hayabusa2. Right: Illustration of MASCOT landing on the surface of Ryugu. (Image credit: JAXA)”
The target area for the MASCOT “landing”:
“MASCOT landing site candidate region (light blue area). Since MASCOT is expected to bounce several times after first touching down, a reasonably wide region is selected. (Image credit: JAXA, University of Tokyo, Kochi University, Rikkyo University, Nagoya University, Chiba Institute of Technology, Meiji University, University of Aizu, AIST, CNES, DLR). “
This artist’s impression depicts the exomoon candidate Kepler-1625b-i, the planet it is orbiting and the star in the centre of the star system. Kepler-1625b-i is the first exomoon candidate and, if confirmed, the first moon to be found outside the Solar System. Like many exoplanets, Kepler-1625b-i was discovered using the transit method. Exomoons are difficult to find because they are smaller than their companion planets, so their transit signal is weak, and their position in the system changes with each transit because of their orbit. This requires extensive modelling and data analysis. [Higher-res images] Using the NASA/ESA Hubble Space Telescope and older data from the Kepler Space Telescope two astronomers have found the first compelling evidence for a moon outside our own Solar System. The data indicate an exomoon the size of Neptune, in a stellar system 8000 light-years from Earth. The new results are presented in the journal Science Advances.
The hunt for exoplanets — planets outside our own Solar System — provided its first results only 30 years ago. While astronomers now find these planets on a regular basis, the search for moons orbiting exoplanets wasn’t successful — until today.
This animation demonstrates how the measured light curve from the star Kepler-1625b led to the conclusion that the system may consist of not only a planet, but also at least one moon.
When the planet moves in front of its parent star a tiny portion of its light is blocked by the disc of the planet, so we observe a dimming of the light from the star. Right after the exoplanet has finished its transit the starlight is seen to dim slightly again, suggesting the presence of a moon trailing the planet. Credit: ESA/Hubble, L. Calçada
In 2017 NASA’s Kepler Space Telescope detected hints of an exomoon orbiting the planet Kepler-1625b. Now, two scientists from Columbia University in New York (USA) have used the incomparable capabilities of the NASA/ESA Hubble Space Telescope to study the star Kepler-1625, 8000 light-years away, and its planet in more detail. The new observations made with Hubble show compelling evidence for a large exomoon orbiting the only known planet of Kepler-1625. If confirmed, this would be the first discovery of a moon outside our Solar System.
The candidate moon, with the designation Kepler-1625b-i, is unusual because of its large size; it is comparable in diameter to the planet Neptune. Such gargantuan moons are unknown in our own Solar System.
“This may yield new insights into the development of planetary systems and may cause astronomers to revisit theories of how moons form,”
Alex Teachey, a graduate student who led the study, explained excitedly [1].
Like its moon, Kepler-1625b is also bigger than its counterparts in the Solar System. The exoplanet is a gas giant, several times more massive than Jupiter [2]. It orbits its parent star at a distance similar to the distance between the Sun and Earth, which puts it — and its candidate moon — at the inner edge of the habitable zone of the star system [3].
To find evidence for the existence of the exomoon, the team observed the planet while it was in transit in front of its parent star, causing a dimming of the starlight.
“We saw little deviations and wobbles in the light curve that caught our attention,”
David Kipping, second author of the study, said.
The planet was observed by Hubble before and during its 19-hour-long transit. After the transit ended, Hubble detected a second and much smaller decrease in the star’s brightness approximately 3.5 hours later, consistent with the effect of a moon trailing the planet.
“It was definitely a shocking moment to see that light curve — my heart started beating a little faster and I just kept looking at that signature,”
David Kipping described his feelings. Unfortunately, the scheduled Hubble observations ended before the complete transit of the moon could be captured.
In addition to this second dip in the light curve, Hubble provided compelling supporting evidence for the moon hypothesis by detecting the planet’s transit more than an hour earlier than predicted. This is consistent with a model of the system in which the planet and its moon orbit a common centre of gravity, causing the planet to wobble away from its predicted location [4].
In principle this anomaly could also be caused by the gravitational pull of a hypothetical second planet in the system, but the Kepler Space Telescope found no evidence for additional planets around the star during its four year mission. Still, further observations by Hubble are needed to fully confirm the existence of Kepler-1625b-i.
“If confirmed, Kepler-1625b-i will certainly provide an interesting puzzle for theorists to solve,” said Kipping. Teachey concluded: “It is an exciting reminder of how little we really know about distant planetary systems and the great spirit of discovery exoplanetary science embodies.”
Notes
[1] The moons of Jupiter and Saturn likely formed through the agglomeration into a disc of material orbiting the planets, so it is possible that this exomoon also formed in a circumplanetary disc. Another possibility is that a passing object was captured by the planet’s gravity. Tidal forces between the two objects would rob momentum from the less massive companion and eventually pull it into a permanent orbit. There are no indications of tidal capture among our Solar System’s moons. In the case of the Earth–Moon system, an early collision with a larger body is hypothesised to have blasted off material that later coalesced into a moon. However, Kepler-1625b and its candidate moon are gaseous, not rocky, so such a collision would not have led to the condensation of a satellite.
[2] Despite its size, the mass of the candidate moon is estimated to be only 1.5 percent of the mass of its companion planet. This value is close to the mass ratio between Earth and the Moon.
[3] While both the planet and its candidate moon are within the habitable zone, where moderate temperatures allow for the existence of liquid water, both bodies are considered to be gaseous and therefore unsuitable for life as we know it.
[4] A distant observer watching the Earth and Moon transit the Sun would note similar anomalies in the timing of Earth’s transit.
More information
The Hubble Space Telescope is a project of international cooperation between ESA and NASA.
The results were presented in the paper Evidence for a large exomoon orbiting Kepler-1625b in the journal Science Advances.
The team of astronomers in this study consists of Alex Teachey and David M. Kipping (Columbia University, New York, USA).
This week we have an epic panel to talk about the recent #dearMoon announcement including Tim Dodd the Everyday Astronaut, Emory “VaxHeadroom” Stagmer, Dr. Niamh Shaw and Astronaut Nicole Stott. We focus on the impact of the recent announcement by using a trip around the moon and art to inspire humanity in a totally new way.
During the discussion it was mentioned that musician Martin Molin of the Swedish “folktronica” band Wintergatan had released a video making the case for his selection for the flight. Here is that video:
Here is a technical discussion of the BFR lunar mission:
Airbus, Blue Origin, ESA, and some other heavyweight companies and organizations are backing a new technical competition program called The Moon Race:
The Moon Race competition is a global initiative founded by Airbus and international partners, aiming to boost the movement around Moon exploration and enable the demonstration of key technologies required for its sustainable exploration.
Organizers launched their effort at this week’s International Astronautical Congressin Bremen, Germany. They want teams to propose technological challenges for lunar surface operations in time for next year’s IAC meeting.
Suggestions could include constructing the first artifact made from lunar resources, extracting enough water from lunar soil to fill a standard-sized bottle, building a power-generating system capable of lighting up the lunar night, or operating the first lunar greenhouse.
The application period is due to open in early 2019. “Details on monetary prizes will be announced with the opening of the applications period,” the organizers say.
The competition is envisioned as a five year program starting from the 2019 starting line. The teams would be expected to “demonstrate proof-of-concept” in 2020, test the systems in a “lunar environment” in 2021, build working implementations in 2022-2023, and send them to the Moon in 2024.
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