Chandra Bubbles
The first 15 years of proposals approved for the Chandra Space Telescope
- Type
- Interactive data visualization
- Role
- Solo developer
- Data
- 2,536 approved proposals, Cycles 1–15
- Built with
- D3, JavaScript
Each year, astronomers compete for observing time on the Chandra Space Telescope. Chandra Bubbles shows every proposal that won time in the telescope's first 15 observing cycles: each circle is one proposal, sized by the time it was awarded and colored by its science area.
- Active galaxies & quasars
- Supernovae & neutron stars
- Compact binaries
- Galaxy clusters & extragalactic
- Stars & white dwarfs
- Normal galaxies
- Galactic diffuse emission
- Solar system
View the numbers for this cycle
| Science area | Proposals | Time (ks) | Share of time |
|---|
Background
Chandra Bubbles started in 2014 as part of “Eye to the Sky,” a final project for CS171, a data visualization course, that I worked on with Daniel Schultz and Patrick O'Brien. I was the sole developer of the bubble chart. I was also working at the Center for Astrophysics at the time, so I was the team's science liaison and source of Chandra data.
The team's first ideas centered on a rotating globe with the stars visible from a chosen spot on Earth. It was visually striking, but it couldn't show what the Chandra data was really about: how the telescope's time is divided up. A bubble chart of proposals, cycle by cycle, did that much better.
The plan was to scrape the data from Chandra's published lists of approved proposals, one page per cycle, but the pages weren't built to be machine-readable, which made that harder than expected. The class version showed a single cycle. After the class ended, I expanded it to all of Chandra's historical data at the time, Cycles 1 through 15, and in 2016 turned it into a standalone site.
This version
The original ran on D3 version 3. For this page it was rebuilt on current D3, with the same data and the same idea, plus a few changes:
- Circle area, not radius, is proportional to time, as the original project proposal intended, so large proposals aren't exaggerated
- Chandra renamed some science categories over the years. The 13 names are grouped into 8 science areas so colors stay consistent from cycle to cycle; the exact category is shown on hover
- A “By category” layout with labels and totals, a table of the numbers, and support for dark mode and phones
The original code is on GitHub.