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Astronomer Pushes Science Forward for Planetary Exploration

Astronomer Dr. Heidi Hammel's Washington D.C. office is a shrine of books, globes, photos, and statues to the universe she's devoted her life to studying. As she holds her hands vertically around a model planet to depict how Uranus rotates around its axis, she's illustrating why planetar astronomers only recently began observing dynamism there.

“This is a planet that is tipped over on its side. It spins lying on its side and in its long year that it travels around the sun, there are decades where one pole is pointing at the sun,” Hammel said. “So no matter how much that planet spins, one half is in sunlight and the other half is in darkness.”

Heidi Hammel


Dr. Hammel was on the team that first observed Neptune’s Great Dark Spot in 1989. | Drew Costley

But then, as it goes another 20 years around the orbit, she continues, Uranus gets to a point where its equator is pointing at the sun, kind of like Earth was on the Autumnal Equinox this past month. “So Uranus, when Voyager flew by [in 1986] was at solstice, where its pole was pointing at the sun, in this half lit up, half completely black state,” she said. “But in 2007, Uranus had moved all the way over to its equinox, and in those 20 something years the planet’s atmosphere changed.”

Unsure why it changed, she excitedly relays some of the recent observations about the planet. “Over the last 24 [or] 25 years, Uranus has changed character completely. Now when you look at Uranus, it’s really active and dynamic,” she said. “Early this year, with the Hubble Space Telescope, we saw a dark spot on the planet and this is only the second time that we’ve seen one on the planet. We saw one in 2006. When Voyager flew by, Uranus didn’t have any dark spots. Uranus had a scant handful of clouds that could be seen with the Voyager camera.”

Several years later, in 2004, Hammel and other astronomers began noticing that Uranus was becoming more dynamic. Besides the dark spots, which are usually enormous weather systems being observed on planets like Uranus and Neptune, she says astronomers began seeing atmospheric features, dark spots, bright spots and banded structures on the planet.

Studying other planets in the solar system helps inform us about Earth, Hammel explains: “Let’s say you have a dog. If your dog gets sick, would you want to take your dog to a vet who’s only ever studied one dog?” she asks rhetorically. “Probably not. You’d want a vet who’s studied a lot of different dogs – big dogs, little dogs, young dogs, old dogs; dogs that have all kinds of different conditions. You’d want somebody who has studied a lot of different dogs.

“So let me say, then, that we care about Earth. We really want to study Earth. Should we only study Earth? Wouldn’t it make more sense to also study other 'Earths' or bigger planets or smaller planets and look [at] how those planets change with time or how the sun affects those planets over time…. Every piece of science that we learn from studying other planets is part of our knowledge of the physics and chemistry of planets in general.”

Whether she knew it or not, when Hammel was using the model planet to show how Uranus rotates and the importance of studying other planets, she was also demonstrating the accessible and effective science communication that has made her a world-renowned public science communicator. Hammel’s research and knowledge on the Outer Solar System in general, and Uranus and Neptune specifically, has made her an essential resource when discussing outer space.

She’s done extensive work with the Hubble Space Telescope, W.M. Keck Observatory and Mauna Kea Observatory; was on the team that first observed Neptune’s Great Dark Spot in 1989, and, with Dr. Imke de Pater, discovered that Uranus’ nine rings compose a single layer of particles in 2003. She’s also served as the public face of NASA, during which time she communicated relevant science about outer space to the public, and she won the Carl Sagan Medal for outstanding communication by an active planetary scientist to the public in 2002. But for the last half-decade, even though she remains active in the planetary science research community, she has been working to make planetary exploration possible.

“I made a commitment several years ago to move from the doing of the research to the enabling of the research,” said Hammel, who has been the executive vice president for the Association of Universities for Research in Astronomy since 2010.

“There’s a lot of fabulous young people out there and I want to make sure that those young people have the opportunities, with the new tools that we’re developing right now, to push the boundaries of science beyond…. So that’s why I’ve been working on the James Webb Telescope. That’s why I’ve been working on telescopes in space beyond James Webb, so that not just my kids, but [other future generations] will have opportunities to work with fantastic new tools.”

Hammel is doing this work amid a downward trend in funding for NASA compared to the rest of the federal budget. Over the last 15 years, the percentage of the federal budget that NASA funding makes up has decreased by 33.3 percent. Hammel, who understands the political and financial side of making science possible, said she realized about 15 years into her career as an astronomer that there have to be people in the scientific community enabling and planning for the science of the future as well as those who are doing it.

“I realized that [planetary exploration] missions are magic, we have to make them happen. And if people don’t act on that, then there won’t be missions for them,” she said. “I realized that wow, if we don’t make this happen that it won’t be there.”

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