http://hubblesite.org/news_release/news/2018-27

Astronomers Release Most Complete Ultraviolet-Light Survey of Nearby Galaxies

Release date: May 17, 2018 1:00 PM (EDT)

The survey of 50 galaxies in the local universe, called the Legacy ExtraGalactic UV Survey (LEGUS), is the sharpest, most comprehensive ultraviolet-light look at nearby star-forming galaxies. Astronomers are releasing the star catalogs for each of the LEGUS galaxies and cluster catalogs for 30 of the galaxies, as well as images of the galaxies themselves. The local universe, stretching across the gulf of space between us and the great Virgo cluster of galaxies, is ideal for study because astronomers can amass a big enough sample of galaxies, and yet, the galaxies are close enough to Earth that Hubble can resolve individual stars.

There has never before been a star cluster and a stellar catalog that included observations in ultraviolet light. Ultraviolet light is a major tracer of the youngest and hottest star populations, which astronomers need to derive the ages of stars and get a complete stellar history. The team used Hubble’s Wide Field Camera 3 and the Advanced Camera for Surveys over a one-year period to snap visible- and ultraviolet-light images of the galaxies and their most massive young stars and star clusters. The researchers also added archival visible-light images to provide a complete picture.

The star catalogs comprise about 39 million stars that are at least five times more massive than our Sun.

Off topic but still from Hubble.

http://hubblesite.org/image/4120/news_release/2018-12

Three Steps to the Hubble Constant

Measure the universe’s expansion rate to an unprecedented accuracy, reducing the total uncertainty to 2.3 percent. The latest Hubble result is based on measurements of the parallax of eight newly analyzed Cepheids in our Milky Way galaxy. These stars are about 10 times farther away than any studied previously, residing between 6,000 light-years and 12,000 light-years from Earth and are just like the ones Hubble can see in other galaxies. Once astronomers calibrate the Cepheids’ true brightness, they can use them as cosmic yardsticks to measure distances to galaxies much farther away.

The Outer Planet Atmospheres Legacy (OPAL) program is a long-term Hubble project that annually captures global maps of our solar system’s four outer planets.