The above picture may not look that spectacular, just a couple of stars against the backdrop of space – exception the two disks it shows are not stars, they are planets – exoplanets, in fact, orbiting a star 310 light years away. As such, it is the first visible light photograph of multiple planets orbiting a Sun-like star taken from Earth.
Called TYC 8998-760-1, the star in question is of the G2V spectral class, and the closest Sun-like star to the solar system. However, whereas the Sun is some 4.6 billion years old, TYC 8998-760-1 is a mere stripling – just 17 million years old. It lies within the southern hemisphere constellation of Musca – a constellation which though small, contains a number of notable stars including Alpha, Beta, Gamma and Zeta Muscae, part of a group of hot blue-white stars that seem to share a common point of origin and motion within the galaxy, HD 100546, a blue-white Herbig Ae/Be star that is surrounded by a complex debris disk containing a large planet or brown dwarf and possible protoplanet, and Theta Muscae, a triple star system, the brightest member of which is a Wolf–Rayet star.
The image was taken by the European Southern Observatory’s (ESO) Very Large Telescope (VLT) using the Spectro-Polarimetric High-contrast Exoplanet REsearch instrument (SPHERE). This instrument utilises a coronagraph to block out much of the light from a star, allowing the light reflected by any planetary bodies to be visible.
TYC 8998-760-1 is an interesting planetary system for a number of reasons. Given the relative youth of the parent star, it might be said that the system represents a glimpse of the early formation of the solar system. However, it is on a scale far vaster than our own. Both of the planets are gas supergiants, the innermost, called TYC 8998-760-1 b, being some 14 times the mass of Jupiter, whilst the outermost, TYC 8998-760-1 c, is around 6 times Jupiter’s mass. Both also orbit their parent at incredible distances in comparison to the planets of our own system: TYC 8998-760-1 b averages 162 AU (1 AU being the average distance the Earth is from the Sun), and TYC 8998-760-1 c averages some 320 AU. By comparison, Neptune, the most distant of our major planets, averages a “mere” 30 AU from the Sun.
These vast distances make both planets curiosities: exoplanets that are large and orbiting far from their host stars are very difficult to fit into the protoplanetary and accretion disk model(s ) that are generally used to explain planetary formation. Further, both planets appear to occupy relatively stable, circular orbits. Astronomers believe this could indicate that the two planets formed more-or-less where they are now and their near-circular orbits may indicate the presence of a still-to-be discovered third large body orbiting even further from the star (and TYC 8998-760-1 c was unknown prior to SPHERE capturing it) – or that their orbits might indicate their are the result of very specific ejections from an unseen stellar companion to TYC 8998-760-1.
Further study is required to determine exactly how the planets may have formed, but their presence does raise the questions on whether smaller, rocky planets might orbit closer to the star – possibly within its habitable zone. As it is, SPHERE’s ability to gather data on planets has yielded a lot of information on the two gas giants that will keep astronomers busy. And while this is only the third image of exoplanets currently on record, with the upcoming generation of high-powered Earth and space-based telescopes, that number will increase over the coming decades.
Heavenly Questions En-route to Mars
In my previous Space Sunday update I covered the launch of the UAE’s Hope mission to Mars, launched as that article was being written, and the (then) forthcoming launch of China’s ambitious Tianwen-1 (“Quest for Heavenly Truth” or “Questions for Heaven”) orbiter / lander / rover mission.
At that time, it wasn’t clear just when China’s mission would lift-off, but going on past launches of the Long March 5 booster that would be hefting the mission away from Earth have generally been within 6 days of the rocket being delivered to the launch pad, speculation was that the Tianwen-1 launch would come in he week of July 20th through 24th, given its launcher arrived on the pad on July 17th.
Those speculations proved to be correct, because Long March 5 launch Y4 took to the skies from the Wenchang Satellite Launch Centre on Hainan Island in the South China Sea, at 04:41 UTC on the Morning of July 23rd (11:41 local time).
The launch, in pretty much perfect weather conditions, was covered in unprecedented detail by China’s state television. Taking a leaf from the launch book used particularly well by SpaceX, cameras on the ground and on the launch vehicle and transfer bus captured every aspect of the mission’s start from engine ignition, through ascent to orbit and staging, to the jettison of the payload fairing and separation of the orbiter / lander / rover as they started their 7- month, 493 million kilometre trek to intercept Mars in its journey around the Sun, which will happen in February 2021.
The mission – the specifics of which you can also find in my previous Space Sunday update – is the first fully integrated orbiter / lander / rover mission ever undertaken to Mars and it is also China’s first attempt at an independent interplanetary mission; the country had attempted a mission to Mars in 2011 with an orbiter called Yinghuo-1, but that mission was launched in partnership with Russia’s Phobos Grunt mission, during which the upper stage of the Zenit launch vehicle failed, leaving the mission stranded in Earth orbit prior to making an uncontrolled re-entry into the atmosphere in 2012.
With today’s launch, China is on its way to join the community of international scientific explorers at Mars. Safe travels Tianwen-1!
– Jim Bridenstine following the Tianwen-1 launch
Also as reported last time around, the orbiter will spend the first 2-3 months of its time around Mars carrying out observations as it settles into it 265×12,000 km polar orbit of the planet. During this time it will image Utopia Planitia in the Martian northern hemisphere (and last visited by America’s Viking 2 lander in the 1970s, in order to finalise the selection of a landing area for the lander / rover, which are expected to arrive on the surface of Mars in April 2021.
And “Percy” is set to Start Out
Staying with Mars, perhaps the most anticipated mission to the red planet for 2020 will also be the last to depart. Having been pushed back due to a combination of minor final preparation glitches and the SARS-CoV-2 pandemic, NASA’s Mars 2020 mission is set to launch the rover Perseverance (or Percy, as it has already been nicknamed) and its helicopter companion Integrity on their way on Thursday, July 30th, 2020.
The rover is seen as an important evolutionary step for NASA’s robotic exploration of Mars. Whilst the still-operational Curiosity, which arrived on Mars in August 2012, was tasked with identifying conditions and evidence that show that Mars may have once been capable of supporting life on its surface, Perseverance has the capability to look for actual signs of past life, and is able to collect samples of rocks and soil and set their for retrieval by future missions for return to Earth to allow in-depth study.
In terms of overall science mission, Curiosity was tasked with identifying conditions and finding evidence that show that Mars may have once been capable of supporting life on its surface – a primary mission it actually achieved within three months of arriving on Mars. However, it was not actually capable of identifying whether any of that life – and we’re talking microbial life here – may still be present, or of what it might have been. Perseverance will take the next logical step in the process: it will look for actual signs of past life, or biosignatures, capturing samples of rocks and soil that could be retrieved by future missions and returned to Earth for in-depth study.
To achieve this, Perseverance, based on the same overall design as the Mars Science Laboratory (MSL) rover Curiosity, but it is slightly larger and heavier – weighing-in at just over a tonne, allowing it to carry a host of new science instruments and more advanced versions of some of the systems found on Curiosity, together with additional enhancements born of lessons learned in operating the MSL rover on Mars for the past 8 years.
In particular, Perseverance carries a sample capability to leave up to 23 samples in sealed container on the surface of Mars that might be collected by possible future mission, together with a more robust drilling system than used by Curiosity. In addition, the rover will have a total of 23 camera – 5 more than the MSL rover, while an improved navigation system will allow it to guide itself to a safe landing area during descent, should the primary sight prove too hazardous, and which will also allow it to undertaken far more complex self-driving operations than Curiosity can manage.
As well as carrying out its own mission on Mars, the rover will also carry the Integrity proof-of-concept helicopter drone (see Space Sunday: helicopters, craters and a sunny ISS for more), and will – hopefully – allow us to hear Mars for the first time via two on-board microphones. These will carry out a number of functions. The first microphone, mounted on the main body of the rover, will record sounds during the rover’s descent to a (hopefully) safe landing on Mars. This audio will be combined with full-colour video recorded by the rover’s Entry, Descent and Landing (EDL) cameras to produce a complete picture of the “seven minutes of terror” that will mark the rover’s arrival on Mars as it plummets through the thin atmosphere and then winched down to the surface by its “skycrane”.
The second microphone is mounted on the rover’s mast alongside its SuperCam, the next generation of the camera / laser system the rover will use to “zap” rocks and soil and determine the chemical make-up of the vaporised materials to detect the presence of any organic compounds. The microphone will be used to record the sound made as the laser vaporises material, potentially revealing more about the composition of the zapped material. Beyond this, both microphones will allow us to hear the winds of Mars and the sounds of the rover in operation – something that may help engineers understand things like wear and tear on the rover’s moving parts.
Perseverance is due to lift-off from Space Launch Complex 41 (SLC 41) at Cape Canaveral Air Force Station atop a United Launch Alliance Atlas V-541 Rocket on Thursday, July 30th at 11:50 UTC. Both the rover and its launch vehicle are already on the pad, and the final step in preparing it for launch was completed on July 22nd, 2020, when the rover’s nuclear power source was installed.
Called a Multi-Mission Radioisotope Thermoelectric Generator (MMRTG), the power source uses the radioactive decay of plutonium to generate electrical energy. This is in turn used to provide power to the rover’s drive motors, electrical systems and science equipment and to power the heaters that keep the rover and its instruments warm during the cold Martian nights and winters. An updated version of the unit currently powering Curiosity, the unit is expected to provide power for the rover for around 14 years of operations on Mars.
Live coverage and countdown commentary for the launch will start at 07:00 EDT (04:00 PDT, 11:00 UTC) on July 30th on NASA Television and the agency’s website and YouTube channel, as well as across social media platforms. Should the launch fail to go ahead as planned, There will be several more opportunities through until August 15th, 2020.
As with the UAE’s Hope mission, and China’s Tianwen-1, the Mars 2020 mission will reach Mars in mid-February 2021. Unlike the Chinese mission however, it will make an immediate entry into the Martian atmosphere and attempt a landing within the 49km diameter Jezero Crater, some 18º above the Martian equator. When it does so, it will also deliver 10,932,295 names of people who applied to have their carried to Mars by the rover, recorded on three small microchips (my own among them!).