Starship Asterisk*

Image Credit: NASA, ESA, and A. Shapley (UCLA)

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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.

Credit: G. Hüdepohl (atacamaphoto.com)/ESO

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Few people have ever viewed the Moon through a telescope as monumental as ESO’s Very Large Telescope (VLT). Astronomers at Paranal Observatory in Chile recently enjoyed this unique opportunity when one of the telescope’s instruments, VIMOS (VIsible Multi-Object Spectrograph), was decommissioned to free up a space at the UT3 telescope for the upcoming CRIRES+ (the CRyogenic InfraRed Echelle Spectrograph Upgrade Project).

VIMOS was astonishingly productive; the spectrograph studied thousands of distant galaxies seen at a time when the Universe was only at a third of its current age, and mapped their distribution and physical properties. The sensitive instruments used by the VLT, including VIMOS, are designed to image dim objects billions of light-years away, and therefore objects as near and bright as our planet’s moon easily completely saturate them with far too much light. But when VIMOS was decommissioned after 16 years of service, the astronomers stationed at Paranal took advantage of the unusual opportunity to utilise a telescope focal station with no instrument attached.

Instead of looking into deep space, they pointed and focused UT3, one of the VLT’s Unit Telescopes — the VLT has four, each with a mirror measuring 8.2 metres across — on the Moon. To create this mesmerising image, the twilight Moon was projected onto a semi-transparent screen, resulting in an intricately detailed display of the myriad crags and craters scattered across its surface. This incredible view was enjoyed by numerous astronomers including Stefan Ströbele, the Adaptive Optics engineer seen in this image.

Credit: ESA/Hubble, & NASA

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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.

Nestled within this ancient time capsule are 49 known RR Lyrae variable stars, which are indispensable tools for measuring distances in the Universe. These variable stars have well-defined luminosities, meaning that astronomers know the total amount of energy they emit. By comparing this known luminosity to how bright the stars appear in the sky, their distance can be easily calculated. Astronomical objects such as this are known as standard candles, and are fundamental to the so-called cosmic distance ladder.

bystander wrote: ↑Tue Dec 25, 2018 12:14 am Climbing the Cosmic Distance Ladder
ESA Hubble Picture of the Week | 208 Dec 24

Credit: ESA/Hubble, & NASA

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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.

Nestled within this ancient time capsule are 49 known RR Lyrae variable stars, which are indispensable tools for measuring distances in the Universe. These variable stars have well-defined luminosities, meaning that astronomers know the total amount of energy they emit. By comparing this known luminosity to how bright the stars appear in the sky, their distance can be easily calculated. Astronomical objects such as this are known as standard candles, and are fundamental to the so-called cosmic distance ladder.