As the IAU General Assembly in Hawai'i draws to a close, the results were still coming in: a new bevy of dwarf galaxies discovered around the Milky Way, the celebration of the first Dark-Sky Sanctuary, and a new directly imaged exoplanet to boot.
The morning twilight is rapidly growing in this subequatorial latitude. I walk slowly and breathe deeply at an altitude of 4,200 meters (13,800 ft), where air has 40% less oxygen than at sea level, where I was a day before.
The pristine night sky of Mauna Kea, the highest point of Hawai‘i, performs a last few minutes before the Sun rises. The twin Keck telescopes, shining yellow adaptive optics laser into the atmosphere, dominate the view. Behind me the Japanese-owned Subaru telescope, as well as the caravan of other telescopes tucked in their domes in front of me, are all collecting the last data before closing down for the day.
Our New Dwarf Galaxy Neighbors
After my 24-hour trip to Mauna Kea, I returned to the International Astronomical Union General Assembly in Honolulu. In the last few days of the two-week-long conference, the problem of missing satellite galaxies captured my attention. According to a leading scenario, dwarf galaxies are the building blocks of galaxy formation, so there should be hundreds or thousands of these faint satellites around the Milky Way and other grand galaxies. Yet by the 1980s, astronomers had identified less than 10 satellite galaxies around the Milky Way — the most prominent of these in our night sky are of course the Large and Small Magellanic Clouds.
With the digital revolution in astronomical imaging and with the increasing size of telescopes, astronomers are now finding many more of these cosmic islets that were once hidden among the foreground stars of the Milky Way. The current list contains about 35 confirmed satellites, ranging in size from less than 1% of the Milky Way’s diameter to 10%. Some of these dwarfs are as close as 30,000 light-years from the outer spiral arms of our galaxy, while others lie more than a million light-years away.
Now Josh Simon (Carnegie Institution for Science) reports that within the first two years of observations collected by the Dark Energy Survey, astronomers have found 17 new candidate and confirmed dwarf galaxies. (Sky & Telescope reported 9 of these earlier this year; another 8 discoveries were released in August). But even as the list grows, it still doesn’t completely close the gap between galaxy formation theory and observation.
Dark Sky Sanctuaries
My work as a nightscape photographer very much ties in with dark skies and light pollution. I was fortunate to attend one of the conference’s public events honoring astronomical heritage and the importance of dark skies. Hosted by the Bishop Museum in Honolulu, the reception launched the book, “Hawaiian and Pacific Star Names.” The International Dark-Sky Association (IDA) also celebrated Dark Sky Sanctuaries, sites that, along with dark sky parks and reserves, will preserve our night skies. Sanctuaries designates the rarest and most fragile dark places left on the planet, and the plan is to include prominent observatory sites. The event celebrated the first approved Dark Sky Sanctuary in the Elqui Valley of northern Chile, the location of the Association of Universities for Research in Astronomy (AURA) Observatory. The site will be known as the “Gabriela Mistral Dark Sky Sanctuary,” named after the famed Chilean poet.
Exoplanet Direct Imaging
The newly discovered exoplanet Eridani b made breaking news here as the first directly imaged exoplanet from the Gemini Planet Imager (GPI) situated at the southern Gemini telescope in Chile. Read the full story on 51 Eridani b.
Vienna in 2017
The 10-day astronomy marathon ended on August 14th. The next host of the 2018 IAU General Assembly will be in Vienna, a highly cultural city, home to an office of the United Nations, and a hub for a variety of international events. The IAU also voted for South Korea to host the 2021 General Assembly.