Tag: Astronomy

On August 8th, 2019, the International Astronomical Union (IAU) approved the names for 14 more significant features on the surface of Pluto, imaged by the New Horizons space vehicle as it flew past the Pluto-Charon system in 2015.

The IAU claimed the authority to officially name or approve the name of planets, dwarf planets, moons, asteroids and planetary features in our solar system during its inaugural General Assembly, held in Rome in May 1922, 3 years after it had been formed by the founding nations of Belgium, Canada, France, Great Britain, Greece, Japan, and the United States, and by which point its membership had grown to 19 nations around the world (today membership stands at 82 nations).

As the sole authority, it means that any names given to things like planetary surface features  – such as “Mount Sharp” on the surface of Mars are entirely unofficial, hence why they are referred to in quotes in these Space Sunday articles. The IAU may determine names on things like surface features entirely by itself (as is the case with “Mount Sharp”, which is officially designated Aeolis Mons), or they may take recommendations from other organisations or groups.

In the case of the 14 names first assigned to features on Pluto by the IAU in 2017, the organisation ratified the suggestions made by the New Horizons mission team. Keeping with this “tradition”, the August 8th, 2019 announcement of the 14 “new” names for surface features first employed by the mission team.

All 14 represent people and missions that contributed to the understanding of Pluto and the Kuiper Belt, as well as drawing on figures from mythology and aerospace exploration in general. They cover a range of surface features on Pluto images by the New Horizons vehicle as it dashed through the Pluto-Charon system that include entire regions of the planet and items such as mountain ranges, plains, valleys and craters. They comprise (in alphabetically order):

Since its flyby of the Pluto-Charon system, the New Horizons vehicle has continued its voyage out through the Kuiper Belt. Most of this has been with the vehicle in a state of hibernation to conserve power, however, in January 2019, the craft encountered  Kuiper Belt Object (KBO) Ultima Thule, aka 2014 MU₆₉ (see my January 28th 2019 Space Sunday article), and data from that encounter is still being transmitted back to Earth.

Currently, the New Horizons mission is funded until April 2021, and may well be extended beyond that date. The vehicle’s radioisotope thermoelectric generator (RTG), which uses the heat from the radioactive decay of plutonium 238 to provide it with electrical power, is expected to provide sufficient energy for its science instruments until the mid-to-late 2030s. So the science team responsible for the mission at the John Hopkins University Applied Physics Laboratory are currently seeking potential KBO targets the craft could fly by in the mid or late 2020s.

Should the vehicle retain sufficient power for some of its instruments, it may be able to study the outer heliosphere (the “bubble” of space surrounding our solar system and created by the outward flow of energise particles from the Sun) in the late 2030s. If it does, it will add to the data gathered on that distant region of space, 100+ AU from Earth (1 AU = the average distance of the Earth from the Sun) by the Voyager spacecraft.

Parker Solar Probe: One Year In

August 12th, 2019, marked the first anniversary of NASA’s Parker Solar Probe. As I reported in Space Sunday: to touch the face of the Sun, this is an ambitious mission to repeatedly fly through the Sun’s corona – the hazardous region of intense heat and solar radiation in the Sun’s atmosphere that is visible during an eclipse – to gather data that could help answer questions about solar physics that have puzzled scientists for decades.

Named for Eugene Parker, the physicist who first theorised the solar wind, the constant outflow of particles and magnetic fields from the sun, the mission is now into its third orbit of the Sun, and due to make a further close solar approach on September 1st, 2019.

The spacecraft carries four suites of scientific instruments to gather data on the particles, solar wind plasma, electric and magnetic fields, solar radio emission, and structures in the Sun’s corona. This information will help scientists unravel the physics driving the extreme temperatures that make the corona hotter than the “surface” of the Sun – and the mechanisms that drive particles and plasma out into the solar system.

So much information has been gathered by the probe during its first two orbits of the Sun that the mission team on Earth is still analysing it. They hope to have the first results available before the end of the year – not that they are complaining!

We’re very happy. We’ve managed to bring down at least twice as much data as we originally suspected we’d get from those first two perihelion passes.

– Nicky Fox, director of NASA’s Heliophysics Division

Nor is that all; the probe’s elliptical 170-188 day orbit means that it has just 11 days per orbit in which to gather data – and these coincide with perihelion, when the craft must withstand temperatures of around 1,370ºC (2,500ºF). To achieve this, the probe is equipped with a 2.3m hexagonal solar shadow-shield that performs three tasks: it absorbs and reflects sunlight away from the vehicle whilst also preventing radiation penetrating its instrument bay and burning-out its circuits and instruments (incident solar radiation at perihelion is approximately 475 times the intensity at low Earth orbit) and also casting a long shadow in which the rest of the vehicle can remain relatively “cool”. Data on the shadow-shield and from within the vehicle as it passes through the corona reveal the shield is working better than anticipated.

So, with another six years of its planned 7-year primary mission, the Parker Solar Probe is set to revolutionise our understanding of the Sun’s corona and the mechanisms powering it.

The data we’re seeing is showing us details about solar structures and processes that we have never seen before. Flying close to the sun—a very dangerous environment—is the only way to obtain this data, and the spacecraft is performing with flying colours.

– Nour Raouafi, Parker Solar Probe project scientist, JHU/APL

Continue reading “Space Sunday: Pluto’s names, Jupiter’s core” →

During the celebrations marking the 50th anniversary of the Apollo 11 mission in July, came a note of sadness: the passing of Chris Kraft.

This is a name that may not be familiar to some, but Christopher C. Kraft, Jr., was one of the most influential figures of NASA’s pioneering early years of America’s human space flight, who joined the agency from its forebear, the National Advisory Committee for Aeronautics (NACA).

Born in Virginia in February 1924, to Bavarian immigrants, Kraft began his studies at Virginia Polytechnic Institute and State University (Virginia Tech) studying aeronautical engineering. During this time he applied to join the US Navy, but was rejected due to an injury to his right hand that occurred during childhood. He graduated in December 1944 with a Bachelor of Science degree.

On graduation, he applied to both the Chance Vought aircraft company and NACA. On arrival at the former on his first day of work, he was told that he could not be hired without his birth certificate, which he had not brought with him. Annoyed, he returned home and accepted the offer from NACA instead.

At NACA he was assigned to the flight research division, working under Robert Gilruth, who was to become his mentor. Most of Kraft’s work was theoretical – although it did lead him to be the original discoverer of wingtip vortices causing the majority of turbulence behind an aircraft. While he enjoyed it, he also found it taxing to the point of considering leaving, when the NACA was subsumed by NASA.

Gilruth then invited Kraft to join a new project he was heading – the Space Task Group – charged with putting a man in orbit. As a result, Kraft became one of the original thirty-five engineers to be assigned to Project Mercury. In his new role, he was assigned to the flight operations division at NASA, charged with determining how the Mercury missions would be managed and operated from the ground. He was reporting in to Chuck Matthews, who essentially passed off the division’s requirements to Kraft in a throwaway comment:

Chris, you come up with a basic mission plan. You know, the bottom-line stuff on how we fly a man from a launch pad into space and back again. It would be good if you kept him alive.

Kraft realised that just like test pilots, whom he had supported through the X-1 flight programmes, astronauts would need a system of communications and support back on Earth during critical phases of the mission. He also knew they would also require a ground-based tracking system and instrumentation for the telemetry of data from the spacecraft. Through this, he came up with the idea of a single control centre to monitor and operate missions in real-time; a concept never before tried.

I saw a team of highly skilled engineers, each one an expert on a different piece of the Mercury capsule. We’d have a flow of accurate telemetry data so the experts could monitor their systems, see and even predict problems, and pass along instructions to the astronaut.

– Chris Kraft, Flight: My Life in Mission Control, 2001

Within this structure, Kraft particularly identified the need for a single individual who would have overall control and coordination over the flight centre engineers, and make the real-time decisions about the conduct of the mission. He called that role the Flight Director, and nominated himself as the man for the role.

The first iteration of the mission control concept was the Mercury Control Centre at Cape Canaveral. During this time, Kraft continued to define and refine the role of the flight director, gaining the singular title Flight as a mark of respect, although his own stubbornness that could make him something of a controversial figure in the eyes of management – but not enough to prevent him being awarded the NASA Outstanding Leadership Medal on the recommendation of the NASA Administrator, and awarded by President John F. Kennedy.

During Mercury, Kraft selected and trained three engineers to become the first generation of flight directors with him:  Glynn Lunney, John Hodge and man who also grew into a legend as he followed Kraft, Gene Kranz. As the more intensive Gemini missions took place, Kraft took on a new role: head of mission operations, but remained  entirely hands-on with the flight director programme, continuing to select and train other flight directors and continuing a flight director in his own right.

Mid-way through the Gemini programme, Kraft was asked to oversee the design and implementation of the brand-new mission control centre that would form a part of the new Manned Spacecraft Centre, near Houston, Texas (now the Johnson Space Centre), which would become the nerve centre for all of NASA’s human spaceflight operations.

Kraft, Lunney and Kranz worked directly on the requirements for the new mission control centre, located at Building 30 at the new space centre, liaising with contractors and determining the design of the two primary Mission Operations Control Rooms (each referred to as MOCR, or “moe-ker”).

By the mid-1960s, Kraft was made Director of Flight Operations, and closely involved in planning the Apollo programme. He joined with Gilruth, now the head of the Manned Spacecraft Centre and possibly the most powerful man in NASA next to the agency’s administrator, George Low, the manager of the Apollo Spacecraft Programme Office and Donald Kent “Deke” Slayton, the head of the Astronaut Office, to take on an entirely unofficial, but essential role:

The four of us … had become an unofficial committee that got together often in Bob’s [Gilruth’s] office to discuss problems, plans and off-the-wall ideas. Not much happened in Gemini or Apollo that didn’t either originate with us or with our input.

– Chris Kraft, Flight: My Life in Mission Control, 2001

In 1969, Kraft officially became Gilruth’s deputy in running the Manned Spacecraft Centre, and succeeded him as overall facility director in January 1972. He remained in that role past his due retirement in 1980, remaining firmly embedded in the space shuttle programme. However, his stubborn and outspoken nature in matters relating to that programme brought him into conflict with NASA Administrator James M. Beggs and others, and he suddenly announced his belated retirement at the end of 1982.

Kraft indirectly returned to the shuttle programme in 1994, when he was appointed chairman of an independent review committee with the remit to investigate ways in which NASA could make that programme more cost effective. His report, published in February 1995, recommended NASA’s should outsource shuttle operations to a single private contractor.

More contentiously, it was sharply critical of the post-Challenger accident safety regime at NASA, claiming it was “duplicative and expensive”, while claiming the shuttle had become “a mature and reliable system”.

NASA’s own Aerospace Safety Advisory Panel responded that, “the assumption that the Space Shuttle systems are now ‘mature’ smacks of a complacency which may lead to serious mishaps.” Nonetheless, responsibility for shuttle operations was turned over to United Space Alliance.

In 2003, the investigation into the Columbia accident, directly cited the recommendations made by Kraft’s committee as potentially contributing to that accident, by encouraging NASA to view the shuttle as an operational, rather than experimental vehicle and distracting attention from continuing engineering anomalies. In typical form, Kraft  defended his report, insisting the space shuttle was “the safest space vehicle ever built”.

Kraft received numerous awards throughout his career, and in on April 4th, 2011, he was guest of honour at a ceremony at Johnson Space Centre’s Building 30 Mission Control Centre when it was renamed the Christopher C. Kraft, Jr., Mission Control Centre, in recognition of the facility’s 50 years managing US human space flight, and Kraft’s unique place in both NASA’s and the building’s histories.

Christopher Kraft passed away on July 22nd, 2019 at the age of 95 and leaving his wife of 69 years, Betty Anne, and son and daughter Gordon and Kristi-Anne, and their families.

Continue reading “Space Sunday: a legend, TESS and a rocket flight” →

The Indian Space Research Organisation (ISRO) successfully launched its Chandrayaan-2 mission to the lunar south pole on Monday, July 22nd, after suffering a week’s day to the schedule. This is an ambitious mission that aims to be the first to land in the Moon’s South Polar region, comprising three parts: an orbiter, a lander and a rover.

Although launched atop India’s most powerful rocket, the GSLV Mk III, the mass of the mission means it cannot take a direct route to Mars, as the upper stage isn’t powerful enough for the mass. Instead, Chandrayaan-2 was placed into an extended 170km x 39,120 km (105 mi x 24,300 mi) elliptical orbit around the earth. For the next month, the orbiter will gradually raise this obit until it reaches a point where lunar gravity becomes dominant, allowing Chandrayaan-2 to transfer into a similarly extended lunar orbit before easing its way down to a 100 km (60 mi) circular polar orbit around the Moon, which it is scheduled to achieve seen days after translating into its initial lunar orbit.

During this period, and through until September 7th, the combined vehicle will carry out multiple surveys of the Moon’s survey, focusing on the South Pole. Then, on September 7th, the  2.4-tonne Chandrayaan-2 will detach the 1.47-tonne Vikram lander (named for Vikram Sarabhai, regarded as the father of the Indian space programme) which will attempt a soft landing.

The orbiter vehicle is designed to operate for a year in its polar orbit for one year. It carries a science suite of eight systems, including the Terrain Mapping Camera (TMC), which will produce a 3D map for studying lunar mineralogy and geology, an X-ray spectrometer, solar X-ray monitor, imaging spectrometer and a high-resolution camera.

The Vikram lander, with four science payloads, will communicate both directly with Earth and the orbiter. It will also facilitate communications with the Pragyan rover, which will be deployed within hours of the self-guiding lander touching down. Between them, the lander and rover carry 5 further science experiments and both are expected to operate for around 14 days.

Craters in the South Polar region lie in permanent shadow and experience some of the coldest temperatures in the solar system and NASA’s Lunar Reconnaissance Orbiter (LRO) has revealed they contain frozen water within them, water likely unchanged since the early days of the Solar System, and thus could hold clues to the history of the Solar System – hence the interest in visiting the region and learning more. The frozen water is also of interest to engineers as it could be extracted to provide water for lunar base; water that could be used for drinking, or growing plants and could also me split to produce oxygen and hydrogen  – essential fuel stocks.

The Chandrayaan-2 mission marks a significant step forward for India’s space ambitions; assuming the Vikram lander is successful, the country will become only the forth nation to land on the Moon after the United States, Russia and China. As a part of its expanding activities in space, the country hopes to fly it first astronauts into space in 2022 and have an operational space station by the end of the 2020s.

2019 OK

No, I’m not making a statement about the year – that’s the name of a chunk of space rock measuring 57 to 130m (187 to 42ft) across that passed by Earth at a distance of around 73,000 km (45,000 mi), putting it “uncomfortably close” to the planet. What’s more, we barely released it was there: 2019 OK was positively identified by the Southern Observatory for Near Earth Asteroids Research (SONEAR), just a couple of days prior to is passage past Earth, and was confirmed by the ASAS-SN telescope network in Ohio, leaving just hours for an announcement of its passage to be made.

Since then, the asteroid’s orbit has been tracked – forward and back (which revealed it had been previously spotted by observatories, but its small size and low magnitude meant its significance wasn’t realised). These observations confirmed 2019 OK is a reactively short-period object, orbiting the Sun every 2.7 years. It passes well beyond Mars before swinging  back in and round the Sun, crossing the Earth’s orbit as it does so. However, while it may pass close to Earth on occasion, it’s highly unlikely it will ever strike us.

It does, however, remind us that near-Earth objects (NEOs) are common enough to be of concern; 2,000 were added to the list 2017 alone. The size of 2019 OK reminds us that there are more than enough of them to be of a significant enough size to pose a genuine threat.

In 2013, an asteroid measuring just 20m across entered the atmosphere to be ripped apart  at an altitude of around 30 km above the Russian town of Chelyabinsk. The resultant resulting shock wave shattered glass down below and injured more than 1,000 people. 2019 OK is at a minimum 2.5 times larger than the Chelyabinsk object – and possibly as much as 10 times larger, putting it in the same class of object that caused the Tunguska event of 1908, when 2,000 sq km (770 sq mi) of Siberian forest was flattened by an air blast of 30 megatons as a result of a comet fragment breaking up in the atmosphere.

Hence why observatories such as SONEAR, ASAS-SN telescope network, the Catalina Sky Survey, Pan-STARRS, and ATLAS and others attempt to track and catalogue NEOs. The more of them we can located and establish their orbits, the more clearly we can identify real threats  – and have (hopefully) a lead time long enough to take action against them.

Oh, and if you thought 2019 OK was big, consider 99942 Apophis. It’s around 400-450m across, and will swing by Earth at a distance of just 31,000 km on  – wait for it – Friday, April 13th, 2029 (so get ready for a lot of apocalyptic predictions in the months leading up to that date!).

Continue reading “Space Sunday: lunar landers, asteroids and more” →

The Orion test article lifts-off from Space Launch Complex 46 at Cape Canaveral Air Force Station at the start of Ascent Abort-2, July 2nd 2019. Credit: NASA

NASA’s Orion Multi-Purpose Crew Vehicle passed a significant test on its way to its first crewed launch (due in 2022) on July 2nd, 2019, as it completed a flight test of the capsule’s launch abort system (LAS).

The LAS is a system designed to pull a crewed capsule clear of a malfunctioning rocket during an ascent to orbit, hopefully saving their lives in the process. As such, it is a significant system that must be tested and cleared for use before crewed flights can commence with a new launch vehicle.

For the Space Launch System (SLS), NASA is following its traditional approach, with the LAS designed to “pull” a crew capsule clear of launch vehicle. It does this by placing a special fairing over the capsule that has a tower extending from its top, fitted with three motors. This has always been the traditional approach to US LAS systems – by contrast, Russian LAS systems generally sit below the capsule and are design to “push” it away from a malfunctioning rocket.

The July 2nd test – called the Ascent Abort-2 (AA-2) mission – was a critical test flight, designed to test the LAS at the point in an ascent to orbit when the Orion / SLS combination will be subjected to the highest aerodynamic stresses – the so-called period of “Max-Q” – that occurs during a rapid ascent into space.

To achieve this, NASA mounted an Orion structural test article – basically an Orion capsule sans its flight systems – contained within a LAS fairing onto the motor stage of an MX Peacekeeper ICBM, and launched it into the Florida skies in a early morning ascent designed to last some 55 seconds.

In that time, the rocket was expected to reach an altitude of 9.5 kilometres (31,000 ft) and a speed of Mach 1.3, at which point the abort sequence would trigger.

As it turned out, the MX rocket motor ran “hot”, accelerating a little faster than anticipated, so reaching its assigned separation altitude 5 seconds early. Nevertheless, the abort sequence initiated correctly, and the powerful abort motors on the LAS fired, generating 181,400 kg of thrust, hauling the Orion free of the ascent motor unit.

Once a clear separation from the still ascending motor stage had been achieved, the attitude control motors at the very top of the LAS fired, flipping it and Orion over. The middle jettison motor then fired, separating the LAS from the Orion.

During an actual abort sequence, the Orion would then re-orient itself so it would be falling heat shield first, allowing its parachutes to be deployed in preparation for a splashdown. However, for the AA-2 flight, the test article did not carry a parachute system. Instead, and like the LAS, the capsule was allowed to fall back into the Atlantic, hitting it at an estimated 480 km/h (300 mph) and breaking up. Just before it did so, however, it ejected 12 bright orange data recorders not unlike those so-called “black boxes” used by aircraft. These contained critical data recorded during the 3 minute 11 second flight, and which will be assessed post-mission to confirm everything did go an planned.

That was a spectacular test we all witnessed this morning. It was really special for the programme; a really big step forward to us. It was a really great day all around – weather and the vehicle. One of the most important parts of the test was to see how the attitude control motor performed. The internal motor pressure was rock solid, straight line and it had excellent control characteristics. Everything we’ve seen so far looks great.

– Mark Kirasich, NASA’s Orion Programme Manager

The Orion test article climbs into the early morning sky over Cape Canaveral Air Force Station at the start of Ascent Abort-2, July 2nd 2019. Credit: NASA

The US has never has to use the LAS on an actual mission. However, there is no guarantee this will always be the case, and circumstances where a LAS must be used are not unkown – as the Soyuz M-10 mission in October 2018 demonstrated (see Space Sunday: of Soyuz aborts and telescopes). Therefore, passing this test was critical if  Orion and SLS are to achieve the flight goals required for NASA’s programme – Project Artemis – to return humans to the surface of the Moon.

Half-Planet, Half-Star

Discovered in 2012, GJ3470b is a “mini-Neptune” planet orbiting a red dwarf star called Gliese 3470, 100 light years from our Sun. Occupying an orbit some 6 million km (3.7 million mi – roughly one-tenth of the distance between the Sun and Mercury) from its parent, the planet has a mass of around 12.6 Earths.

None of this is particularly unusual; as I’ve noted in past Space Sunday articles, M-type stars are the most common type of star in the galaxy, and mini-Neptune type planets account for around 80% of the exoplanets discovered to date. Nevertheless, recent studies have revealed GJ3470b to be a very unique world.

The presence of an atmosphere around the planet was detected fairly soon after its discovery and prompted astronomers to take a prolonged look at it. To do this, they combined the Hubble and Spitzer space telescopes to examine the planet’s atmosphere for a total of 20 transits in front of its parent star.

These observations, using the light of the star passing through the planet’s atmosphere during the transits, allowed the astronomers to gather data on the composition of GJ3470b’s atmosphere. What was discovered came as a huge surprise.

It has been expected that the observations would reveal an atmosphere somewhat similar to Neptune’s, but such was the depth to which they could measure, it quickly became clear that GJ3470b has an almost pristine atmosphere of hydrogen and helium surrounding a large solid core.

The presence of hydrogen and helium may not sound too unusual – after all, the four gas giants of our solar system have atmospheres largely made up of those two gases. However, they also have amounts of other, heavier elements – methane, nitrogen, oxygen, ammonia, acetylene, ethane, propane, phosphine, etc., – none of which showed up in any of the spectral analyses performed by Hubble and Spitzer. This makes GJ3470b’s  atmosphere closer in nature to that of the Sun or a star than it does to a planet, leading to it being dubbed “half-planet / half-star” in some quarters, and making it the most unique exoplanet yet discovered.

Continue reading “Space Sunday: rockets, exoplanets and alien oceans” →

Two Earth-sized planets have been found orbiting a star 12.5 light-years from our own, adding to the catalogue of exoplanets located in our own cosmic back yard.

The star in question is Teegarden’s Star, a M-type red dwarf, the most common type of star in our galaxy, and therefore the most frequent type found to have planets and planetary systems. However, Teegarden’s Star is a little different to other red dwarfs we’ve observed with or without planets. For a start, despite being only a short cosmic stone’s throw from Earth, it is incredibly dim – so dim that we didn’t even notice it until 2003. Not that that in itself is usual, it’s believed that the space around us for a distance of about 20 light years could have many dim red dwarf stars hiding within it, simply because this region of our galaxy seems to have a much lower density of such stars than we see elsewhere.

What makes Teegarden’s Star odd in this respect is that it wasn’t found as a result of a search for such nearby dim red dwarfs, but because astronomers tripped over it whilst reviewing data originally gathered in the 1990s by the Near-Earth Asteroid Tracking (NEAT) project. In fact, the star is actually named for the head of the review team, Bonnard J. Teegarden, an astrophysicist at NASA‘s Goddard Space Flight Centre. The star is also somewhat unusual in that it has a large proper motion (approximately 5 arcseconds per year), marking it as one of seven stars with such large proper motions currently known.

Observations of the star made in 2010 by the Red Optical Planet Survey (ROPS) suggested the star might have at least one planet orbiting it, but the data was insufficient to draw a definitive conclusion. However, in June 2019, and after three years of verifying their data, scientists conducting the CARMENES survey at the Calar Alto Observatory announced evidence of two Earth-mass exoplanets orbiting the star within its habitable zone.

The planets were detected using the radial velocity method (aka Doppler spectroscopy), also informally referred to as the “wobble method”. Putting it simply, a star with planets doesn’t simply spin on its axis with the planets whizzing around it. Rather, the mass of the planet(s) works against the mass of the star, creating a common centre of mass which, although still inside the star, is sufficiently removed from its own centre to cause the star to effectively rolls around it (see the image on the right).

This means that when seen from Earth, there are times when the star can seem as if it is moving “away” from our telescopes, signified by its light shifting to the red end of the spectrum. Equally, there are other times when it appears to be moving “towards” us, signified by its light shifting to the blue end of the spectrum. It is by observing and measuring this visible Doppler shift that tells us there are planets present. In all, this method of stellar observation has accounted for almost one-third of all exoplanets found to date.

The key point with this method of observation is not only does it allow astronomers to locate planets orbiting other stars, it actually allows maths to be applied, allowing the number of potential planets to be discerned, their distance from their parent star and important factors such as their probable mass, which in turn allows their likely size and composition to be estimated.

In the case of Teegarden’s Star, the data indicates the two planets orbiting the star – called Teegarden’s b and Teegarden’s c respectively – have a mass of around 1.05 and 1.1 that of Earth each, suggesting they are probably around the same size as one another and comparable to Earth in size. Teegarden’s b, the innermost planet, orbits its parent every 4.9 terrestrial days, and Teegarden’s c every 11.4 terrestrial days.

The combined mass of these planets, coupled with the amount of Doppler shift exhibited by Teegarden’s Star has led to some speculation there may be other, larger planets orbiting much further out from the star. Such planets would be hard to locate because Teegarden’s Star is so dim when observed from Earth, astronomers cannot rely on the transit method  – where large planets passing in front of their parent star can cause regular dips in its apparent brightness – to identify their existence.

However, what is particularly interesting about Teegarden’s b and c is their location relative to their parent, and the nature of Teegarden’s Star itself. The latter is a particularly cool and low-mass red dwarf, with just one-tenth of the Sun’s mass and a surface temperature of 2,700°C (4890°F). This means that at their respective distances, both planets are within the star’s habitable zone – and may well have atmospheres.

The two planets resemble the inner planets of our solar system. They are only slightly heavier than Earth and are located in the so-called habitable zone, where water can be present in liquid form.

– Mathias Zechmeister, University of Göttingen, Teegarden planetary team lead

This latter point  – the existence of atmospheres around both planets – has yet to be proven. As noted previously in these articles, M-type stars are actually not nice places; when active (and Teegarden does seem to be well past its active stage) in their youth, they can be prone to violent irradiative outbursts which could both strip away the atmospheres of any planets orbiting them over time and irradiate the planets’ surfaces. And even if  the planets do have atmospheres, their close proximity to their parent likely means they are both tidally locked with their same face towards it. This is liable to make them pretty inhospitable places and potentially prone to extremes of weather.

But there is one other interesting point to note here. While Teegarden’s Star may well be dim to the point of being practically invisible when viewed from Earth, the same isn’t true the other way around: our Sun would be a bright star in the skies over Teegarden’s b and c. What’s more, the angle of our solar system to those worlds (practically edge-on) means that if we were to imagine one of them having an intelligent, scientific race, they could easily detect the planets orbiting our Sun using the transit method of observation, and could probably deduce up to three of the innermost planets might be capable of supporting life.

Continue reading “Space Sunday: alien worlds, telescopes and lightsails” →