From 9.30pm AEST (12.30pm BST, 1.30pm ASAT, 7.30am EST), I’ll be blogging live as we follow NASA’s coverage of the New Horizons mission. Refresh this page every few minutes for the latest updates.
NASA live stream:
To finish up for the night - have you checked out Pluto time? I was surprised to find just how bright the daylight is at Pluto. See here to calculate the time at your location that matches the lighting conditions of local noon at Pluto.
The next Pluto time for my location in Melbourne is 7:28am tomorrow, but here’s how it looked a few days ago from the Three Sisters in Katoomba, NSW. The solar system is full of amazing worlds.
What happens next? The flyby isn’t all that New Horizons is doing. It will now be moving through the shadows of Pluto and Charon. These occultations will allow New Horizons to probe the atmospheres of the two worlds.
When Pluto is between the spacecraft and the sun, measurements will be made at ultraviolet wavelengths to determine what gases are found in Pluto’s atmosphere. Then when Pluto is between the spacecraft and Earth, the aim is for New Horizons to receive a transmission from the NASA’s Deep Space Network on Earth. By detecting how the signal passes through Pluto’s atmosphere it will provide information on the atmospheric pressure and temperature.
Pluto and Charon are a binary world – no other planet and moon combination have such similar masses to each other. Watch this video captured by New Horizons in January and you can see the two objects orbiting around their common centre of mass. Both objects are wobbling back and forth.
Charon and Pluto are also tidally locked – they both keep the same face pointing towards each other. This is because they each take 6.4 Earth days to spin once on their axis AND it takes 6.4 Earth days for Charon to orbit Pluto.
However, they look very different. It appears that Pluto has a younger surface, while Charon is old and battered. As data comes down, scientists will count the number of craters as a function of their size to work out the ages of different parts of their surfaces. Why is Pluto younger? Possibly due to an internal engine or climate effects due to Pluto having an atmosphere, while Charon doesn’t. More will be known with higher resolution data.
We will get to see the south pole of Pluto, but it’ll be under “Charon-light”. Pluto’s axis is tilted so that the sun set on Pluto’s south pole 20 years ago and it will not rise again for another 80 years. Shortly after New Horizons’ closest approach to Pluto (perhaps happening right now!), the spacecraft will see Pluto’s night-side.
From the surface of Pluto, Charon appears seven times larger than Earth’s full moon, but five times fainter. But that’s enough for Charon to light Pluto so that this southern region will be seen. However, it won’t be as high resolution as the day-time images.
Here’s the image again:
The north pole is towards the top of the image, while the darker regions towards the bottom are the equator. There is clearly strong variations in brightness across the dwarf planet. The scientists report that they can also see a history of impacts and surface activity, perhaps tectonic activity that occurred in the past or maybe the present.
The atmosphere also plays a role in shaping the planet - it’s known to snow on Pluto and changes have been detected as the planet varies its distance from the sun. But no plumes or other signs of Pluto’s atmosphere have been found, yet.
Astronaut and astronomer John Grunsfeld (and a hero of mine!) reveals the first of many rewarding views of Pluto. As shown in the sneak peek below, the resolution is 4km per pixels, which is 1,000 times better than can be done from Earth.
But better is to come. Below is a comparison of what Earth would look like if New Horizons was flying over our planet at the same altitude that it has flown by Pluto. In the satellite image looking down on New York city, you can see Manhattan between the Hudson and East rivers, distinguish ponds in Central Park, count the wharves on the Hudson river and see runways from the airport.
Already Pluto is showing features that make it an interesting world to explore.
Earlier today the New Horizons team provided the best measurement of Pluto’s diameter. At 2,370km, it confirms that Pluto is bigger than the dwarf planet Eris by a mere 34km. When Eris was discovered in 2003, its brightness suggested that it was bigger than Pluto and while the two are now known to be pretty close in size, Eris is certainly more massive by 27%.
Of course the exciting thing about discovering Eris, is that’s opened up a whole new part of the Solar System – a third zone of icy worlds that contain the building blocks of the solar system in deep freeze.
New Horizons makes history - somewhere out there, billions of kilometres from Earth a little spacecraft has flown by a distant world. It’s collecting a treasure trove of data that will come flowing back to us over the next year or so. Congratulations to all the scientists, engineeers and those involved that have made it happen.
New Horizons is all alone, firing off commands that have been pre-programmed. The last signal from the spacecraft was received at 1:17pm today (AEST). Right now the spacecraft is focused on Pluto - if it spent time talking to Earth that would take time away from observing Pluto. The spacecraft is due to send its ‘I’m fine and healthy’ message back to Earth at 10:53am tomorrow (AEST).
Here’s a sneak peek of the latest image, taken 6am this morning (AEST) at a distance of 766,000km. Will be discussed on NASA TV in 20 minutes.
Then and now. Here’s the discovery image of Charon from 1978. See the slight elongation of Pluto in the left image? That gave Charon away, because none of the background stars were found to change in a similar way between the two images.
And this is what New Horizons is giving us now. We see two very different worlds, one large and red, one small and grey.
For most of my childhood, Pluto was closer to the sun than Neptune. Pluto takes 248 years to orbit the sun but for 20 years, between January 1979 and February 1999, Pluto sat inside Neptune’s orbit. Even though their orbits cross paths, the two will never collide. They are in a 3:2 resonance, meaning that for every two orbits of Pluto, Neptune has orbited the sun three times, keeping them apart.
Not asleep now! For about two-thirds of its flight, New Horizons was powered down and in hibernation. Like a real sleepy-head, the spacecraft would briefly wake up two or three times a year, check that all was ok, then return to deep slumber. The spacecraft woke for good on December 6, 2014.
The road ahead for New Horizons - note the timings are given in Australian Eastern Standard Time (AEST).
“It feels like you’ve been walking on an escalator for almost a decade, and then you step upon a supersonic transport” says Alan Stern, principal investigator for the New Horizons mission to Pluto.
It’s been a long wait for these scientists and engineers, following a spacecraft that was launched nine-and-a-half years ago. It’s no wonder this has been dubbed the mission of patience.
But now, the fun is about to begin. This evening (Australian time), New Horizons will whizz past Pluto – the last unexplored world in our solar system. It’s a new realm of discovery, seeing a part of the solar system that we’ve never seen before. This is a fantastic story of exploration and one we can all be a part of.
Until then, enjoy some of the latest images to be beamed back from the edge of the solar system.
Authors: The Conversation