Hubble Space Telescope Images Reveal Neptune’s Moon
This composite Hubble Space Telescope picture shows the location of a newly discovered moon, designated S/2004 N 1, orbiting the giant planet Neptune, 4.8 billion kilometers from Earth. The moon is so small (no more than 12 miles across) and dim, it was missed by NASA’s Voyager 2 spacecraft cameras when the probe flew by Neptune in 1989. Several other moons that were discovered by Voyager appear in this 2009 image, along with a circumplanetary structure known as ring arcs. The black-and-white image was taken in 2009 with Hubble’s Wide Field Camera 3 in visible light. Hubble took the color inset of Neptune on August 19, 2009. Credit: NASA, ESA, and M. Showalter (SETI Institute).
Neptune is the most distant planet in our solar system, which makes its systems of moons and rings a challenge to observe from Earth. These things are small and dim, even in Hubble Space Telescope images and data.
On July 1, Dr. Mark Showalter, a scientist at the SETI Institute in California, spotted something in Hubble images that hadn’t been seen before circling around the giant planet. Or least, it hadn’t been seen by human eyes. It was a small moon orbiting the planet about once every 23 hours. He was actually studying faint arcs (segments) of rings. “The moons and arcs orbit very quickly, so we had to devise a way to follow their motion in order to bring out the details of the system,” he said. “It’s the same reason a sports photographer tracks a running athlete—the athlete stays in focus, but the background blurs.”
It turns out that this little moon, now dubbed S/2004 N1, was in images taken by Hubble between 2004 and 2009, but it’s extremely small and dim. It’s likely no one was looking directly for that moon, so it remained hidden in the data archives, waiting for Dr. Showalter to find it.
This finding is a great example of archival discoveries—that is, findings made as astronomers go back through earlier observations. They do this for a variety of reasons. Sometimes it’s to check and see if the object ever appeared to observers before. Or, as in the case of a supernova explosion, to see what the object that exploded looked like in earlier observations. Or, sometimes, they do it to chart change over time (for example, changes on the surface of Mars).
Prior observations of astronomical objects through the world’s panoply of telescopes (both ground-based, orbiting, and in situ (at planets) give us a good feel for how the planets, moons, rings, and distant objects like stars, nebulae, and galaxies change over time. The universe is a constantly evolving place, and it will always provide us with new objects and events to discover and study.
I do a lot of traveling throughout the year, much of it related to astronomy in some way. Back in 1996, I went to the Big Island of Hawai’i to do a series of comet observations using the University of Hawai’i 2.3-meter telescope. Before that I had traveled the island during planetary science field trips, hiking the slopes of Kileaua and Mauna Loa to sample lava and study volcanic landscapes. It quickly became one of my favorite places to spend some time.
Astronomy and the Big Island of Hawai’i go hand in hand. On the eastern side of the island, high atop towering Mauna Kea, sits a collection of observatories that serve astronomers around the world. Not far away is the volcanically active Kileaua, whose active lava flows are “recarpeting” parts of the island along the southeast rift zone. I once heard someone describe those flows as the last gasp of a giant star’s life. Think about it.
The Galaxy Garden at Paleaku Peace Gardens Sanctuary on the Big Island of Hawai’i. Image copyright 2013 Carolyn Collins Petersen.
Earlier this year I had a chance to visit one of the Big Island’s hidden gems, a place that brings astronomy and the beauty of the island together in a very unique way. It’s called the Galaxy Garden—a place where you can literally walk across the Milky Way Galaxy. It’s a scale model of our galaxy made entirely of tropical plants, a lava walk, secluded benches and other hidden delights. My tour guide was artist Jon Lomberg, whose work I have long admired since I first saw it on the late Carl Sagan’s Cosmos series. The Galaxy Garden was his idea, and he worked on it with Barbara DeFranco, who is the director of the Paleaku Peace Cardens Sanctuary, of which the garden is an integral part.
As we walked through the garden, Jon talked to me about the driving force behind the garden. He was moved to create it by the sheer scale of our own galaxy. “It seemed to me that a garden you could walk though would be the perfect place to let people experience the scale of the Milky Way,” he told me.
Jon Lomberg points out our star and some nearby stars on a leaf of a planet located nearly at the outskirts of the garden. The earrings indicate the relative positions of those stars. The yellow dots on the plant leaves represent stars scattered throughout the galaxy. Image copyright 2013, Carolyn Collins Petersen
The garden is 100 feet wide and is set at a scale of a thousand light-years per foot. It occupies about a quarter acre of lawn in the Peace Garden, surrounded by trees, and not far away, a lovely lawn that is flanked by other gardens, including a Buddhist meditation garden. One of the interesting things that Jon pointed out to me is that the Galaxy Garden is on a slope with a slight swell in it, which echoes the warp that our galaxy has, probably due to interactions with other galaxies in the past.
The plants that make up the Galaxy Garden are all emblematic of objects in our galaxy. For example, the arms are planted with gold dust crotons, which have spotted leaves. Those spots represent the stars, dust and gas in our galaxy. In the regions where stars are born, gorgeous hibiscus flowers stand in for the many nebulae in our galaxy where stars form. In other areas, where stars are dying, vincas flowers represent planetary nebulae and the expanding remnants of supernova explosions. At the center of the garden, where the core of our galaxy is represented, tall-standing dracaena trees and red bromeliads stand in for the globular star clusters that whizz around the core. The core itself is represented by a little fountain that suggests the black hole at our galaxy’s core, plus its event horizon and jet activity. All in all, it’s a very cool experience to stroll the Galaxy Garden.
The core of our galaxy represented in the Galaxy Garden by a fountain. Image copyright 2013, Carolyn Collins Petersen.
To walk through the Galaxy Garden is to explore across 100,000 light-years of space. It’s amazing how much this helped me get a feel for the structure and immensity of our galactic home. When I couldn’t be any more amazed, Jon took me aside to one of the outer spiral arms and pointed to a small crystal earring. “Guess what this is,” he said. I looked at it and said, “The solar system?” It was, and it’s surrounded by small crystal earrings that represent the brightest nearby stars to the Sun. And, all of these are set on a few leaves on a towering plant at least 45 or so feet away from the center of the garden. That was when the scale of the galaxy really popped into reality for me.
I was able to spend about an hour strolling the Galaxy and exploring the rest of the gardens. The Garden is astronomically accurate and I was just totally blown away by the creativity it represents.
My tour guide, artist Jon Lomberg. The Galaxy Garden is his brainchild and creation, made possible by the Peace Garden Sanctuary. Image copyright 2013, Carolyn Collins Petersen
The Galaxy Garden is one of those hidden delights that make a trip really worthwhile. It’s the kind of place that tourists brag about finding. But, its splendors aren’t reserved for off-island visitors. Jon is working to make it more of a focal point for science educational outreach on the Big Island. Not far from the garden is a beautiful meeting room where local students watched the Mars Curiosity landing last year. He said the place was packed, showing him that there’s a LOT of local interest in astronomy.
If you’re headed for the Big Island, you HAVE to check this place out. It’s about 30 minutes south of Kona, and totally well worth the drive and the time you take to stroll the gardens. Check out the Peace Garden web site, and the Galaxy Garden web site for more information on how to get there and what days it’s open. They also have more pictures of the gardens and buildings you’ll be visiting. Jon also has a has a link to a talk he gave about the garden earlier this year. He’s a great speaker and very knowledgeable and it’s well worth watching. I thoroughly enjoyed my visit with him and the chance to see an amazing and beautiful representation of our home galaxy.
Peace out, galactically! And, thanks to Jon and Barbara for making my visit possible.
