This time spacefans, we say farewell to two old friends, say hi to a possible exomoon, and arrive at Mercury!
So Long Kepler And Thanks For All The Exoplanets
Launched in 2009 after nine years of operation, the stunningly successful Kepler mission has ended because sadly the craft is out of fuel and will remain forever in silence in its current safe orbit. Despite its demise, the data it has collected will still be analysed for many years to come and will doubtless hold yet more discoveries over and above the 2,600 planets we know of so far. Many of these worlds are small, rocky bodies like our own, some of them within their solar system’s habitable zone. The graphic below puts into perspective just how much more there is to discover.
Credit: NASA
“As NASA’s first planet-hunting mission, Kepler has wildly exceeded all our expectations and paved the way for our exploration and search for life in the solar system and beyond,” said Thomas Zurbuchen, associate administrator of NASA’s Science Mission Directorate in Washington. “Not only did it show us how many planets could be out there, it sparked an entirely new and robust field of research that has taken the science community by storm. Its discoveries have shed a new light on our place in the universe, and illuminated the tantalizing mysteries and possibilities among the stars.”
“When we started conceiving this mission 35 years ago we didn’t know of a single planet outside our solar system,” said the Kepler mission’s founding principal investigator, William Borucki, now retired from NASA’s Ames Research Center in California’s Silicon Valley. “Now that we know planets are everywhere, Kepler has set us on a new course that’s full of promise for future generations to explore our galaxy.”
From the data Kepler has given us, we have discovered that not only are exoplanets everywhere to the point that they’re ubiquitous, but at least one planet revolves around every single star in the galaxy! We have also discovered that our solar system is unusual in not having the most common type of planet, which is a super Earth (hold this space for the elusive planet 9), and is actually poorly populated in comparison to many others.
The Kepler mission was based on a very innovative design. It was an extremely clever approach to doing this kind of science,” said Leslie Livesay, director for astronomy and physics at NASA’s Jet Propulsion Laboratory, who served as Kepler project manager during mission development. “There were definitely challenges, but Kepler had an extremely talented team of scientists and engineers who overcame them.”
Four years into the mission, the craft hit problems with a gyroscope. The mission team was able to devise a fix using solar pressure, switching the spacecraft’s field of view roughly every three months. This enabled an extended mission for the spacecraft, dubbed K2, which lasted as long as the first mission and bumped Kepler’s count of surveyed stars up to more than 500,000.
“We know the spacecraft’s retirement isn’t the end of Kepler’s discoveries,” said Jessie Dotson, Kepler’s project scientist at NASA’s Ames Research Center in California’s Silicon Valley. “I’m excited about the diverse discoveries that are yet to come from our data and how future missions will build upon Kepler’s results.”
I can’t help but feel emotional about its passing, but we have much to look forward to with the launch of TESS (Transiting Exoplanet Survey Satellite) and the long delayed James Webb Space Telescope
Dusk For The Dawn Mission
On the back of the sad news about the end of the Kepler mission due to running out of fuel, the Dawn mission has also come to an abrupt demise for the same reason, it’s out of hydrazine and can no longer communicate with Earth or recharge its solar panels. It has, however, operated for three years longer than its original mission, so we can’t grumble to be honest. It’s given us a wealth of data about Ceres and Vesta over the years.
“Today, we celebrate the end of our Dawn mission – its incredible technical achievements, the vital science it gave us, and the entire team who enabled the spacecraft to make these discoveries,” said Thomas Zurbuchen, associate administrator of NASA’s Science Mission Directorate in Washington. “The astounding images and data that Dawn collected from Vesta and Ceres are critical to understanding the history and evolution of our solar system.”
Dawn launched in 2007 on a journey of 6.9 billion kilometers. Propelled by ion engines, the spacecraft achieved many firsts along the way. Dawn arrived at Vesta in 2011, the second largest object in the main asteroid belt, and the spacecraft became the first to orbit a body in the region between Mars and Jupiter. In 2015, when Dawn went into orbit around Ceres, a dwarf planet that is also the largest world in the asteroid belt, the mission became the first to visit a dwarf planet and go into orbit around two destinations beyond Earth.
“The fact that my car’s license plate frame proclaims, ‘My other vehicle is in the main asteroid belt,’ shows how much pride I take in Dawn,” said Mission Director and Chief Engineer Marc Rayman at NASA’s Jet Propulsion Laboratory (JPL). “The demands we put on Dawn were tremendous, but it met the challenge every time. It’s hard to say goodbye to this amazing spaceship, but it’s time.”
The data Dawn beamed back to Earth from its four science experiments enabled scientists to discover that the two objects had different origins in the early Solar system. Among its accomplishments, Dawn showed how important location was to the way objects in the early solar system formed and evolved. Dawn also reinforced the idea that dwarf planets could have hosted oceans over a significant part of their history, and potentially still do, with obvious astrobiological implications, hence the strict planetary protections in place, particularly with regard to Ceres. The craft will continue in its orbit for the foreseeable future.
“In many ways, Dawn’s legacy is just beginning,” said Principal Investigator Carol Raymond at JPL. “Dawn’s data sets will be deeply mined by scientists working on how planets grow and differentiate, and when and where life could have formed in our solar system. Ceres and Vesta are important to the study of distant planetary systems, too, as they provide a glimpse of the conditions that may exist around young stars.”
Evidence of First Exomoon Discovered
After much searching, the first tentative clues to these elusive small bodies may have been uncovered. Moons are, by nature, smaller than the planet they orbit and thus harder to detect. Finding exoplanets is difficult enough after all! This potential moon candidate, which is 8,000 light-years from Earth in the Cygnus constellation, orbits a gas-giant planet that, in turn, orbits a star called Kepler-1625. Researchers caution that the moon hypothesis is currently merely posited and must be confirmed by follow-up observations by the Hubble Space Telescope.
“This intriguing finding shows how NASA’s missions work together to uncover incredible mysteries in our cosmos,” said Thomas Zurbuchen, associate administrator of NASA’s Science Mission Directorate at Headquarters, Washington. “If confirmed, this finding could completely shake up our understanding of how moons are formed and what they can be made of.”
Naturally these moons cannot be imaged directly and due to the fact that as they transit their star whilst orbiting their planet their signal is far weaker and more difficult to detect.
Video Credit: NASA
In search of exomoons, Alex Teachey and David Kipping, astronomers at Columbia University in New York, plowed through data from 284 Kepler-discovered planets that were in comparatively wide orbits, longer than 30 days, around their host star. The researchers found one instance, in planet Kepler-1625b, of a transit signature with intriguing anomalies, suggesting the presence of a moon.
“We saw little deviations and wobbles in the light curve that caught our attention,” Kipping said.
The exoplanet as it transits across the face of its star leads to a dip in the light detected from the star, a light curve as those of you playing Project Discovery will be familiar with. Now for an exomoon, you are looking for a smaller dip in the light curve which was spotted 3.5 hours later plus a wide orbit with an infrequent transit. This may be caused by an as yet unknown secondary planet in the system, however if it’s there Kepler didn’t see it.
“A companion moon is the simplest and most natural explanation for the second dip in the light curve and the orbit-timing deviation,” Kipping explained. “It was definitely a shocking moment to see that Hubble light curve, my heart started beating a little faster as I kept looking at that signature. But we knew our job was to keep a level head and essentially assume it was bogus, testing every conceivable way in which the data could be tricking us.”
As in the early days of planet hunting where finding large hot Jupiters was the norm, this exomoon candidate is also likely to be large, possibly as large as Neptune, with its planet being much bigger than Jupiter. It’s possible that both the planet and moon could be in the habitable zone, but as both are gaseous, they’d be uninhabitable. However that doesn’t rule out the possibility of as yet undetectable moons like Europa.
BepiColumbo Launches To Mercury
The ESA-JAXA BepiColombo mission to Mercury launched successfully on board an Ariane 5 from Europe’s Spaceport in Kourou on October 20th for its exciting new mission to study the mysteries of the small planet closest to our star.
BepiColombo is a joint endeavor between ESA and the Japan Aerospace Exploration Agency, JAXA. It is the first European mission to Mercury, the smallest and least explored planet in the inner solar system, and the first to send two spacecraft to looking at different aspects of the planet at the same time.
“Launching BepiColombo is a huge milestone for ESA and JAXA, and there will be many great successes to come,” said Jan Wörner, ESA Director General. “Beyond completing the challenging journey, this mission will return a huge bounty of science. It is thanks to the international collaboration and the decades of efforts and expertise of everyone involved in the design and building of this incredible machine, that we are now on our way to investigating planet Mercury’s mysteries.”
“Congratulations on the successful launch of Ariane 5 carrying BepiColombo, ESA-JAXA joint Mercury exploration mission,” said Hiroshi Yamakawa, JAXA President. “I would like to express my gratitude for the excellent achievement of launch operations. JAXA has high expectations that the ensuing detailed observations on the surface and interior of Mercury will help us better understand the environment of the planet, and ultimately, the origin of the Solar System including that of Earth.”
BepiColombo comprises two science orbiters: ESA’s Mercury Planetary Orbiter (MPO) and JAXA’s Mercury Magnetospheric Orbiter (MMO, or ‘Mio’). The ESA-built Mercury Transfer Module (MTM) will carry the orbiters to Mercury using a combination of solar electric propulsion and gravity assist flybys, with one flyby of Earth, two at Venus, and six at Mercury, before entering orbit at Mercury in late 2025. Venus has had very few missions aimed at it as it has a notoriously thick, dense atmosphere. The Russian Venera missions have previously landed on the surface and have given valuable data before being crushed after just a few hours, so any additional information about this hot hostile world is very welcome.
“There is a long and exciting road ahead of us before BepiColombo starts collecting data for the science community,” said Günther Hasinger, ESA Director of Science. “Endeavours like the Rosetta mission and their ground-breaking discoveries even years after their completion have already shown us that complex science exploration missions are well worth the wait.”
Credit: ESA
“BepiColombo is one of the most complex interplanetary missions we have ever flown,” said Andrea Accomazzo, ESA Flight Director for BepiColombo. “One of the biggest challenges is the Sun’s enormous gravity, which makes it difficult to place a spacecraft into a stable orbit around Mercury. We have to constantly brake to ensure a controlled fall towards the Sun, with the ion thrusters providing the low thrust needed over long durations of the cruise phase.”
Due to the close proximity to the Sun, the spacecraft will be exposed to extreme radiation and heat which will range from -180ºC to over 450ºC – hotter than a pizza oven. Many of the spacecraft mechanisms and outer coatings had not previously been tested in such conditions so it will be interesting to see how they perform. The overall design of the three spacecraft modules also reflects the intense conditions they will face. The large solar arrays of the transfer module have to be tilted at the right angle to avoid radiation damage, while still providing enough energy to the spacecraft. On the MPO, the wide radiator means the spacecraft can efficiently remove heat from its subsystems, as well as reflect heat and fly over the planet at lower altitudes than ever achieved before. Eight-sided Mio will spin 15 times a minute to evenly distribute the Sun’s heat over its solar panels to avoid overheating.
“Seeing our spacecraft blast off into space is a moment we have all been waiting for,” said Ulrich Reininghaus, ESA’s BepiColombo project manager. “We have overcome many hurdles over the years, and the teams are delighted to see BepiColombo now on the road to intriguing planet Mercury.”
“A unique aspect of this mission is having two spacecraft monitoring the planet from two different locations at the same time: this is really key to understanding processes linked to the impact of the solar wind on Mercury’s surface and its magnetic environment,” added ESA’s BepiColombo project scientist Johannes Benkhoff. “BepiColombo will build on the discoveries and questions raised by NASA’s Messenger mission to provide the best understanding of Mercury and Solar System evolution to date, which in turn will be essential for understanding how planets orbiting close to their stars in exoplanet systems form and evolve, too.”
We wish the mission well and see you soon space fans.
