And then I wrote… in 2011, the planet Neptune had completed one full orbit around the Sun from the time when it was first discovered, and a small magazine called Argentus, edited by a friend of mine, Steve Silver, invited a number of astronomers to submit articles in its honor. You can see the resulting special issue here, on line. My contribution was to conduct an interview with Dr. Heidi Hammel, who is one of the world’s leading experts on the outer planets… and someone I have known since we were at MIT together, a… few... years ago.

Here’s the interview:

Planet Neptune was discovered on September 23, 1846, by the Berlin Observatory astronomers Johann Galle and Heinrich D’Arrest. They had famously been informed by the French astronomer Urbain Le Verrier that calculations of the perturbations in the orbit of Uranus suggested a planet could be found in a particular spot of the sky; when Galle and D’Arrest pointed their telescope at that spot, they found the planet, first try out. (John Couch Adams in Cambridge had made similar calculations, but couldn’t find any observer to listen to him and take a look.) 

Once Neptune was found, people started looking at earlier observations when it should have been visible and discovered that it had actually been seen, but not recognized as a planet, by Jérôme Lalande in 1795 and John Herschel (son of the discoverer of Uranus) in 1835. In fact, one observation of Jupiter and its moons made by Galileo in 1613 also includes a star that is now thought to be Neptune!

With all these observations, it was quite easy to trace out the orbit of Neptune and calculate its period to be 164.79 years, or 60,190 days. On July 12, 2011, exactly 60,190 days will have passed since Neptune was discovered. Thus on that night it celebrates its first Neptune-year since it was recognized by fellow dwellers in its solar system.

But what’s happening today with Neptune? Who better to ask than the world’s leading expert on the planet, Heidi Hammel.

Dr. Hammel achieved world-wide fame in 1994 as the lead scientist on the team using the Hubble Space Telescope to observe the impact of Comet Shoemaker-Levy into Jupiter. Her images not only were published in newspapers and television world-wide, her gracious presence and clear explanations to the reporters made her an instant media star… one that was recognized by the world’s largest association of planetary astronomers, the Division for Planetary Sciences of the American Astronomical Society, who awarded her the Sagan Medal in 2002 for her contributions to the public understanding and enthusiasm for planetary science. She even was the subject of a biography, Beyond Jupiter, by Fred Bortz, written to inspire school children (especially girls aged 9-12) to consider a career in science.

After graduating from MIT in 1982, she went to the University of Hawaii where she earned her PhD in physics and astronomy in 1988. After that she worked at the Jet Propulsion Laboratory and MIT. In 2005 she joined the board of directors of The Planetary Society. Now a senior research scientist with the Space Science Institute, her work concentrates on observing and understanding the outer planets. She has been an author on more than 300 papers, going back to her undergraduate days at MIT.

It was at MIT when I first met Heidi, while she was a student and I was a research post-doctoral fellow. But it wasn’t in the planetary sciences department where we crossed paths… in fact, I was also trying out a future career by appearing in the MIT Musical Theatre Guild’s production of Fiddler on the Roof. While I was on stage as the Rabbi (blame my beard!) Heidi was in the orchestra pit, playing the drums.

We’ve stayed in touch over the years, meeting up at various scientific meetings around the world. This conversation occurred via Skype from my office in the Vatican Observatory south of Rome, and her home in Connecticut.

Were you aware that this is the first anniversary of the discovery of Neptune – in Neptune years?

If I had not been aware, then the number of calls from reporters would have alerted me, because you are not the only one to call me! Sometime this week I will also be talking to the BBC, and I have some other emails awaiting in my in-box.

I am happy that you have actually that you responded to me, then! This is what happens when you’re the world’s leading expert on a planet.

I guess so! [Laughs] One of them, anyway.

NASA captured the detailed snapshot of the Neptunian dark spot earlier in September and November 2018 with the Hubble Wide Field Camera. The mystery blob is the sixth of its kind to suddenly appear on Neptune since NASA first observed the phenomenon 30 years ago. In 1989, NASA’s historic Voyager 2 spacecraft flew past Neptune and snapped images of two dark spots in the planet’s southern hemisphere. Scientists dubbed the incredible discovery “The Dark Spot” and “The Dark Spot Two”. [source: WSBuzz.com]

We’re able to do thermal imaging of Neptune now, because we finally have big enough telescopes and big enough detectors that are arrays instead of single channel bolometers. Now we can do infrared imaging, and with the large telescopes we have enough spatial resolution to actually map out where some of the heat is coming from on the planet.

What are some of the telescopes that you are using?

Gemini [a pair of 8.1 meter telescopes in Hawaii and Chile], and the VLT [the Very Large Telescope array, a set of four 8.2 meter telescopes in Chile]. Glenn Orton is really the expert on this… he’s been doing the VLT work, and I have been doing some of the Gemini work.

What we see is that down on the south pole of Neptune is a very bright spot, and we really don’t know much about the details of that or why it’s there. But it’s quite evident in the imaging that there’s this tightly confined spot...

We first thought it was the pole itself. When we look in the near-infrared images from Keck – which are reflected light, not thermal emission – there is a very tiny confined spot at the south pole. So when we got our thermal images (which don’t have as much resolution) with a bright polar spot, we initially that maybe that was the pole itself. But in some of the images, the spot seems to shift around, as if it is something that is close to the pole but not quite at the pole. But we’re not really sure, we don’t have enough data.

So it’s a mystery. Why is there a bright polar spot there? What’s causing it and why should it be moving? It’s very hard to answer these questions with the limited data that we have.

Why does it matter?

The specific question of whether Neptune has a hot spot on its pole or not...

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