In a holiday image courtesy of the Hubble Space Telescope, the Cepheid variable star RS Puppis, 10 times more massive than the sun and 200 times larger, shines in a wreath-like “gossamer cocoon” of dust, brightening and dimming over a 41.5-day cycle. RS Puppis has an average intrinsic brightness 15,000 times greater than the Sun’s and is one of the most luminous Cepheids in the Milky Way. As it pulsates, the surrounding nebula flashes in wave like “light echoes. By measuring those fluctuations and the faint light echoes moving across the nebula, astronomers have been able to establish the distance to RS Puppis with high precision. The European Southern Observatory’s New Technology Telescope found that distance to be about 6,500 light years in 2008. Follow-on studies by Hubble in 2014 came up with a slightly lower value. The European Space Agency’s Gaia spacecraft was able to directly measure the distance to RS Puppis using geometric parallax, coming up with a value of 5,580 (plus or minus 260) light years.
This NASA/ESA Hubble Space Telescope image reveals the simple beauty of NGC 339, a 6.5-billion-year-old massive intermediate age star cluster that lies in the SMC, a dwarf galaxy some 200,000 light-years away from us. The relationship between such clusters and true globular clusters is not yet fully understood.
This NASA/ESA Hubble Space Telescope image reveals NGC 1222, a galaxy with a rather eventful story to tell. NGC 1222 has been described as a peculiar example of a so-called lenticular galaxy, but one that exhibits very recent star formation on a huge scale — an event known as a starburst — due to having recently consumed two dwarf galaxies.
This glorious spiral galaxy is known as NGC 24, measures some 40,000 light-years across and lies about 25 million light-years away in the southern constellation of Sculptor. However, there may be more to this picture than first meets the eye: 80 percent of NGC 24’s mass is thought to be held within an invisible dark matter halo.