Comet 46P/Wirtanen: The NASA/ESA Hubble Space Telescope observed comet 46P/Wirtanen on 13 December 2018 when the comet was 12 million kilometers from Earth. In the image, the comet’s nucleus is hidden in the center of a fuzzy glow from the comet’s coma. The coma is a cloud of gas and dust that the comet has ejected during its pass through the inner Solar System due to heating from the Sun. The inner part of a comet’s coma is normally not accessible from Earth. The close fly-by of comet 46P/Wirtanen allowed astronomers to study it in detail. They combined the unique capabilities of Hubble, NASA’s Chandra X-ray Observatory, and the Neil Gehrels-Swift observatory to study how gases are released from the nucleus, what the comet’s ices are composed of, and how gas in the coma is chemically altered by sunlight and solar radiation. Comet 46P/Wirtanen made its closest approach to Earth on 16 December, when it passed just over 11 million kilometers from our planet, about 30 times farther away than the Moon. Although it is the brightest comet of 2018, 46P/Wirtanen is only barely visible to the unaided eye. It is best viewed through binoculars or a telescope. Comet 46P/Wirtanen orbits the Sun once every 5.4 years, much quicker than the 75-year orbit of the more famous Comet Halley. Most of its passes through the inner Solar System are much farther from Earth, making this display particularly notable. Link:

Name: 46P/Wirtanen
Type: Solar System : Interplanetary Body : Comet
Category: Solar System
Release date: 27 December 2018, 17:06
Credit: NASA, ESA, and D. Bodewits (Auburn University) and J.-Y. Li (Planetary Science Institute)

Hubble captures blobs of material sweeping through stellar disc: These two images, both taken with the NASA/ESA Hubble Space Telescope, are taken six years apart. They show fast-moving blobs of material sweeping outwardly through a debris disc around the young, nearby red dwarf star AU Microscopii (AU Mic). Red dwarfs are the most abundant and longest-lived stars in our Milky Way. AU Mic, however, is only about 23 million years old, making it a very young star. The top image was taken in 2011; the bottom in 2017. Hubble's Space Telescope Imaging Spectrograph (STIS) took the images in visible light. This comparison of the two images shows the six-year movement of one of the known blobs (marked by an arrow). Researchers estimate that the blob, which is zipping along at nearly 24 000 kilometres an hour, traveled more than 1300 million kilometres between 2011 and 2017. That is about the distance from Earth to Saturn. Astronomers do not know how the blobs are launched through the system. Eventually, the blob highlighted in the image will sweep through the disc, escape the star's gravitational grip, and race out into space. Astronomers expect the string of blobs to clear out the disc within 1.5 million years. Their estimated ejection speeds are between 14 000 kilometres per hour and 43 000 kilometres per hour, fast enough to escape the star's gravitational clutches. They currently range in distance from roughly 1500 million kilometres to more than 8800 million kilometres from the star. The disc, seen edge-on, is illuminated by scattered light from the star. The glare of the star, located at the centre of the disc, has been blocked out by the STIS coronagraph so that astronomers can see more structure in the disc. The bright dot above the left side of the disc in the 2017 image is a background star. The system resides 32 light-years away in the southern constellation Microscopium.

Name: AU Microscopii
Type: Milky Way : Star : Circumstellar Material : Disk : Debris
Category: Stars
Distance: 30 light years
Release date: 9 January 2019, 10:33
Credit: NASA, ESA, J. Wisniewski (University of Oklahoma), C. Grady (Eureka Scientific), and G. Schneider (Steward Observatory)

Hubble captures intricate structures inside a giant migrating blob: The NASA/ESA Hubble Space Telescope image on the left is an edge-on view of a portion of a vast debris disc around the young, nearby red dwarf star AU Microscopii (AU Mic). Though planets may have already formed in the disc, Hubble is tracking the movement of several huge blobs of material that could be "snowplowing" remaining debris out of the system, including comets and asteroids. The box in the image at left highlights one blob of material extending above and below the disc. Hubble's Space Telescope Imaging Spectrograph (STIS) took the picture in 2018, in visible light. The glare of the star, located at the centre of the disc, has been blocked out by the STIS coronagraph so that astronomers can see more structure in the disc. The STIS close-up image at right reveals, for the first time, details in the blobby material, including a loop-like structure and a mushroom-shaped cap. Astronomers expect the train of blobs to clear out the disk within only 1.5 million years. The consequences are that any rocky planets could be left bone-dry and lifeless, because comets and asteroids will no longer be available to glaze the planets with water or organic compounds. AU Mic is approximately 23 million years old. The system resides 32 light-years away in the southern constellation Microscopium.

Name: AU Microscopii
Type: Milky Way : Star : Circumstellar Material : Disk : Debris
Category: Stars
Distance: 30 light years
Release date: 9 January 2019, 10:34
Credit: NASA, ESA, J. Wisniewski (University of Oklahoma), C. Grady (Eureka Scientific), and G. Schneider (Steward Observatory)

Artist’s Impression of WASP-121b: This artist's illustration shows an alien world that is losing magnesium and iron gas from its atmosphere. The observations represent the first time that so-called "heavy metals" — elements more massive than hydrogen and helium — have been detected escaping from a hot Jupiter, a large gaseous exoplanet orbiting very close to its star. The planet, known as WASP-121b, orbits a star brighter and hotter than the Sun. The planet is so dangerously close to its star that its upper atmosphere reaches a blazing 4,600 degrees Fahrenheit, about 10 times greater than any known planetary atmosphere. A torrent of ultraviolet light from the host star is heating the planet's upper atmosphere, which is causing the magnesium and iron gas to escape into space. Observations by Hubble's Space Telescope Imaging Spectrograph have detected the spectral signatures of magnesium and iron far away from the planet. The planet's "hugging" distance from the star means that it is on the verge of being ripped apart by the star's gravitational tidal forces. The powerful gravitational forces have altered the planet's shape so that it appears more football shaped. The WASP-121 system is about 900 light-years from Earth.

Name: WASP-121b
Type: Milky Way : Star : Circumstellar Material : Planetary System
Category: Exoplanets
Distance: 900 light years
Release date: 2 August 2019, 10:03
Credit: NASA, ESA, and J. Olmsted (STScI)