Just over a week ago, the Herschel Space Observatory was turned off for good. Built and operated by the European Space Agency, Herschel launched on May 14, 2009, and hung out at a Lagrangian Point—at L2 or 1.5 million kilometers from Earth in the opposite direction of the Sun. It did its job—and a really good job at that—for almost four years.
Herschel sent thousands of images back to Earth, allowed scientists to better understand star formation, and sought evidence of water vapor, oxygen, and deuterium in our Solar System and beyond. In fact, scientists couldn’t keep up with the data coming back from Herschel, so even though the telescope is now silent, the analysis of what Herschel saw will continue for years to come.
Within a couple of years, the Hubble Space Telescope, which launched in 1990 and orbits Earth at about 560 kilometers above us, will face a similar fate. The possibility of maintenance and servicing missions for Hubble ended when the space shuttle stopped flying two years ago.
Over the last few weeks—in part because we’ll be attending the Launch Pad Astronomy Workshop in July—we’ve been catching up with Hubble by watching Experiencing Hubble: Understanding the Greatest Images of the Universe. This series of lectures about astronomy is organized around a Top 10 list of Hubble images from David M. Meyer, a professor at Northwestern University. The lectures are loosely hung on the spectacular composite photographs, so that, for instance, a Hubble view of the Sombrero Galaxy offers entre into a wider discussion of galaxy shapes and distances generally and, by route of explanation of galaxy distances, to the work of astronomer Henrietta Leavitt. In other words, each lecture is triggered by a particular Hubble image and unfolds in a way that invites the non-scientist to learn about astronomy related to what that image displays.
One of Hubble’s major achievements was to allow scientists to narrow their estimate of the universe’s rate of expansion and thereby better estimate the age of the universe. As scientists sorted through the information that Hubble provided, they surmised that the expansion may well be accelerating and that dark energy—a phenomenon scientists surmise indirectly—might be the cause of this speeding up of the universe’s expansion.
In addition, Hubble sends back remarkable images that continue to allow astronomers to better understand how stars are formed and die. Images and data also suggest that black holes really are likely at the centers of many galaxies. Closer to home, Hubble allowed scientists to watch Comet Shoemaker-Leavitt 9 collide with Jupiter in almost real time. And though Pluto was demoted from planet status, Hubble saw that it has a fifth moon.
What’s on the horizon, so to speak, in the lineage of space telescopes? If all goes well—it was canceled, then un-canceled a couple of years ago—the James Webb Space Telescope is set to head toward L2 in 2018. Like the International Space Station, this set of instruments is a collaborative project among many countries.
The plan is for Webb to use infrared observation to see through the so-called dust in space and show us objects that have been especially difficult to see, even with Herschel and Hubble, because they are very-very far away, dim, or cold. The hope is that, as a result, we will better understand even earlier history of the universe and the formation of stars, planets, and perhaps even life.