25 years of stunning definition: This stunning spiral galaxy is Messier 100 in the constellation Coma Berenices, captured here by the NASA/ESA Hubble Space Telescope — not for the first time. Among Hubble’s most striking images of Messier 100 are a pair taken just over a month apart, before and after Servicing Mission 1, which took place 25 years ago in December 1993. After Hubble was launched, the astronomers and engineers operating the telescope found that the images it returned were fuzzy, as if it were out of focus. In fact, that was exactly what was happening. Hubble’s primary mirror functions like a satellite dish; its curved surface reflects all the light falling on it to a single focal point. However, the mirror suffered from a defect known as a spherical aberration, meaning that the light striking the edges of the mirror was not travelling to the same point as the light from the centre. The result was blurry, unfocused images. To correct this fault, a team of seven astronauts undertook the first Servicing Mission in December 1993. They installed a device named COSTAR (Corrective Optics Space Telescope Axial Replacement) on Hubble, which took account of this flaw of the mirror and allowed the scientific instruments to correct the images they received. The difference between the photos taken of Messier 100 before and after shows the remarkable effect this had, and the dramatic increase in image quality. COSTAR was in place on Hubble until Servicing Mission 4, by which time all the original instruments had been replaced. All subsequent instrumentation had corrective optics built in. This new image of Messier 100 taken with Hubble’s Wide Field Camera 3 (WFC3), demonstrates how much better the latest generation of instruments is compared to the ones installed in Hubble after its launch and after Servicing Mission 1.

Name: M 100
Type: Local Universe : Galaxy : Type : Spiral
Category: Galaxies
Constellation: Coma Berenices
Release date: 10 December 2018, 06:00
Credit: NASA, ESA

Messier 100 shows improvements of Hubble: This collage shows the spiral galaxy Messier 100 as it was observed with the NASA/ESA Hubble Space Telescope over the last 25 years. The three images of this stunning galaxy clearly show how the different servicing missions performed on Hubble improved the capabilities of the telescope. The leftmost image was taken in 1993 with the Wide Field and Planetary Camera 1 (WFPC1) — Hubble’s first camera. The image is blurry, caused by the uncorrected spherical aberration of Hubble’s main mirror. The light striking the edges of the mirror was not travelling to the same focal point as the light from the centre. The second, middle, image was taken in early 1994. with the newer Wide Field Planetary Camera 2 (WFPC2), which was installed during Servicing Mission 1, which took place in December 1993. The very same mission also installed a device named COSTAR (Corrective Optics Space Telescope Axial Replacement) on Hubble, which took account of this flaw of the mirror and allowed the scientific instruments to correct the images they received. WFPC2 was Hubble’s workhorse camera for many years and was only replaced in Servicing Mission 4, the fifth and final servicing mission. The newest image — visible to the right — was taken with the Wide Field Camera 3 (WFC3) which was installed in 2009 during Servicing Mission 4. The image was taken in 2018 to celebrate the 25th anniversary of Servicing Mission 1.

Name: M 100
Type: Local Universe : Galaxy : Type : Spiral
Category: Galaxies
Release date: 10 December 2018, 06:00
Credit: NASA, ESA

Hubble opens its eye again: For three weeks in October, Hubble’s eyes on the Universe closed. On the evening of Friday 5 October, the orbiting observatory put itself into safe mode after one of its gyroscopes failed. The telescope stopped making science observations, oriented its solar panels toward the Sun, and waited for further instructions from the ground. Within hours the ground control team had activated a backup gyroscope. However, when that gyroscope did not work correctly, the long, hard work to get the telescope exploring the Universe once again began in earnest. The Hubble team had either to figure out how to get this backup gyroscope working, or to turn to a previously developed and tested one-gyroscope mode, which is proven to work. It took weeks of creative thinking, repeated tests, and minor setbacks to solve the problem of the misbehaving gyroscope. Members of the Hubble operations team and of the review board suspected there might be some sort of obstruction in the gyroscope affecting its readings. Attempting to dislodge such a blockage, the team repeatedly tried switching the gyroscope between different operational modes and rotating the spacecraft by large amounts. In response, the extremely high rotation rates from the gyroscope gradually fell until they were close to normal. Encouraged but cautious, the team uploaded new software safeguards to Hubble to protect the telescope in case the gyroscope should again report unduly high rates, and then sent the telescope through some practice manoeuvres to simulate real science observations. They kept a close watch to make sure everything on the spacecraft performed correctly. It did. In the early morning of 27 October Hubble captured its first image since slipping into safe mode at the beginning of the month. The observations targeted star-forming galaxies 11 billion light-years away in the constellation Pegasus. Astronomers hope to use observations like this to answer the question of how the Universe was reionised between 150 million and one billion years after the Big Bang.

Name: Hubble Space Telescope
Type: Early Universe : Galaxy
Category: Galaxies
Constellation: Pegasus
Release date: 17 December 2018, 06:00
Credit: NASA, ESA, and A. Shapley (UCLA)

Globular Cluster NGC 1466: This image from the NASA/ESA Hubble Space Telescope reveals an ancient, glimmering ball of stars called NGC 1466. It is a globular cluster — a gathering of stars all held together by gravity — that is slowly moving through space on the outskirts of the Large Magellanic Cloud, one of our closest galactic neighbours. NGC 1466 certainly is one for extremes. It has a mass equivalent to roughly 140 000 Suns and an age of around 13.1 billion years, making it almost as old as the Universe itself. This fossil-like relic from the early Universe lies some 160 000 light-years away from us. NGC 1466 is one of the 5 clusters in the LMC in which the level of dynamical evolution (or "dynamical age") was measured.

Name: NGC 1466
Type: Milky Way : Star : Grouping : Cluster : Globular
Category: Star Clusters
Constellation: Hydrus
Distance: 150000 light years
Release date: 24 December 2018, 06:00
Credit: ESA/Hubble & NASA