Galaxies Used to Refine the Hubble Constant: These galaxies are selected from a Hubble Space Telescope program to measure the expansion rate of the universe, called the Hubble constant. The value is calculated by comparing the galaxies' distances to the apparent rate of recession away from Earth (due to the relativistic effects of expanding space). By comparing the apparent brightness of the galaxies' red giant stars with nearby red giants, whose distances were measured with other methods, astronomers are able to determine how far away each of the host galaxies are. This is possible because red giants are reliable milepost markers because they all reach the same peak brightness in their late evolution. And, this can be used as a "standard candle" to calculate distance. Hubble's exquisite sharpness and sensitivity allowed for red giants to be found in the stellar halos of the host galaxies. The red giants were searched for in the halo of each galaxy. The center row shows Hubble's full field of view. The bottom row zooms even tighter into the Hubble fields. The red giants are identified by yellow circles.

Type: Early Universe : Galaxy
Category: CosmologyGalaxies
Release date: 16 July 2019, 17:21
Credit: NASA, ESA, W. Freedman (University of Chicago), ESO, and the Digitized Sky Survey

Structure of Exoplanet GJ 3470 b: This artist's illustration shows the theoretical internal structure of the exoplanet GJ 3470 b. It is unlike any planet found in the Solar System. Weighing in at 12.6 Earth masses the planet is more massive than Earth but less massive than Neptune. Unlike Neptune, which is 3 billion miles from the Sun, GJ 3470 b may have formed very close to its red dwarf star as a dry, rocky object. It then gravitationally pulled in hydrogen and helium gas from a circumstellar disk to build up a thick atmosphere. The disk dissipated many billions of years ago, and the planet stopped growing. The bottom illustration shows the disk as the system may have looked long ago. Observations by the NASA/ESA Hubble Space telescope and the NASA Spitzer space telescopes have chemically analyzed the composition of GJ 3470 b's very clear and deep atmosphere, yielding clues to the planet's origin. Many planets of this mass exist in our galaxy.

Name: Gliese 3470b
Type: Milky Way : Star : Circumstellar Material : Planetary System
Category: Exoplanets
Release date: 3 July 2019, 15:17
Credit: NASA, ESA, and L. Hustak (STScI)

A Weakened Black Hole Allows Its Galaxy to Awaken: The Phoenix galaxy cluster contains the first confirmed supermassive black hole that is unable to prevent large numbers of stars from forming in the core of the galaxy cluster where it resides. Optical observations with the NASA/ESA Hubble Space Telescope provide evidence for further cooling of gas near the center of the Phoenix Cluster. Ten billion solar masses of cooler gas are located along filaments to the north and south of the black hole, which likely originate from outbursts by the supermassive black hole located in the center of the image. This image was captured using observations from various telescopes. Optical light data from Hubble show galaxies (in yellow), and filaments of cooler gas where stars are forming (in light blue).

Name: Phoenix Cluster
Type: Early Universe : Galaxy : Grouping : Cluster
Category: Galaxies
Constellation: Phoenix
Distance: 6 billion light years
Release date: 19 November 2019, 11:18
Credit: NASA, ESA, and NRAO

Artist's impression of Milky Way inflows and outflows: This illustration envisions the Milky Way galaxy's gas recycling above and below its stellar disk. The NASA/ESA Hubble Space Telescope observes the invisible gas clouds rising and falling with its sensitive Cosmic Origins Spectrograph (COS) instrument. The spectroscopic signature of the light from background quasars shining through the clouds gives information about their motion. Quasar light is redshifted in clouds shooting up and away from the galactic plane, while quasar light passing through gas falling back down appears blueshifted. This differentiation allows Hubble to conduct an accurate audit of the outflowing and inflowing gas in the Milky Way's busy halo—revealing an unexpected and so-far unexplained surplus of inflowing gas. Astronomers have discovered an unexplained surplus of gas flowing into our Milky Way after conducting a galaxy-wide audit of outflowing and inflowing gas. Rather than a gas equilibrium and "balanced books," ten years of data from the Hubble Space Telescope showed there is more gas coming in than going out.

Name: Milky Way
Type: Milky Way
Category: Illustrations
Release date: 11 October 2019, 17:53
Credit: NASA, ESA, and D. Player (STScI)

Hubble Probes Cotton Candy Planets: New observations from the NASA/ESA Hubble Space Telescope have provided the first spectroscopic observations of two of these super-puffy planets, which are located in the Kepler-51 system. The recent Hubble observations allowed a team of astronomers to refine the mass and size estimates for these worlds – independently confirming their “puffy” nature. Though no more than several times the mass of Earth, their hydrogen/helium atmospheres are so bloated they are nearly the size of Jupiter. In other words, these planets might look as big and bulky as Jupiter, but are roughly 1/100th the mass of Jupiter. How and why their atmospheres balloon outwards remains unknown, but this feature makes super-puffs prime targets for atmospheric investigation. Using Hubble, the team went looking for evidence of components, notably water, in the atmospheres of Kepler-51b and 51d. Hubble observed the planets when they passed in front of their star, aiming to observe the infrared color of their sunsets. Astronomers deduced the amount of light absorbed by the atmosphere across a range of infrared light wavelengths, thus creating a spectrum for each planet in hopes of seeing the telltale signs of constituents like water in the features of the spectra. The team concluded that the low densities of these planets are in part a consequence of the young age of the system, a mere 500 million years old. Models suggest these planets formed outside of the star’s “snow line” where icy materials can survive. The planets then migrated inward, like a string of railroad cars. Link:

Name: Kepler-51b, Kepler-51d
Type: Milky Way : Planet
Category: Exoplanets
Release date: 23 December 2019, 11:43
Credit: NASA, ESA, and NRAO